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Review Article - (2012) Volume 3, Issue 1

Designing Vaccines against Human Papillomavirus and Hepatitis B Virus: Similarities and Differences for Preventable Viral Infections and role of AS04 Adjuvant System in Addressing Specific Challenges

Nathalie Garcon*, Dominique Descamps, Maarten Leyssen, Michel Stoffel and Alberta Di Pasquale
GlaxoSmithKline Biologicals, Wavre, Belgium
*Corresponding Author: Nathalie Garcon, Vice President, Head of Global Adjuvant Center For Vaccine, GlaxoSmithKline Biologicals, Avenue Fleming 20, 1300 Wavre, Belgium, Tel: +32 (0)1 085 8856, Fax: +32 (0)1 085 8856 Email:


This opinion paper describes the experience of GSK Bio in developing two vaccines with a novel Adjuvant System (AS04) against two viral infections, Human papillomavirus (HPV) and Hepatitis B virus (HBV).

Developing a vaccine against HPV is difficult because the virus remains local, evades the immune system, and does not induce a reliable long lasting protection upon natural infection. Vaccination of pre-haemodialysis and haemodialysis patients against hepatitis B represents a challenge as well, because these patients are immunocompromised and develop a reduced and short lasting immune response to administration of conventional HBV vaccines.

Adjuvants can be used to amplify the immune response to vaccine antigens. The combination of antigens with more than one adjuvant (referred to as “Adjuvant System”), can lead to the development of vaccines which generate specific and effective immune responses adapted to both the pathogen and the target population. The Adjuvant System AS04 contained in the two licensed vaccines against HPV and HBV described here is a combination of the TLR4 agonist MPL and aluminium salt.

Clinical results from these AS04 adjuvanted vaccines are described in light of other vaccines adjuvanted with aluminium salts only. The vaccines formulated with AS04 have been shown to enhance the immune responses while maintaining a clinically acceptable reactogenicity and safety profile.

Keywords: HPV; HBV; Vaccines; AS04; Adjuvants; Adjuvant system


Several intracellular pathogens can establish long-lasting chronic infections and may lead to clinical disease. Two examples of such pathogens are the Human papillomavirus (HPV) and the Hepatitis B virus (HBV). Immunological mechanisms are involved both in the establishment and maintenance of the tolerance to these infections. Chronic infections and diseases are the results of a delicate interplay between the pathogen’s actions to survive in the host and the attempts of the immune system to eradicate it.

HPV is one of the most common chronic viral infections in humans. The virus consists of circular, double stranded DNA and has no envelope. Approximately 130 different HPV types have been identified so far [1] and about 40 of these infect the human genital tract, including 15 of types considered as oncogenic [2]. It is estimated that up to 80% of women will acquire a HPV infection in their lifetime [3]. Cervical HPV infections are asymptomatic; although most of them clear spontaneously and only 5–10% will become persistent infection possibly leading to the development of clinical pre-cancerous lesions and cancer.

Upon natural infection, HPV remains at the site of infection, evades the immune system, and does not reliably induce protective immunity as the virus does not kill infected cells and hence neither inflammation nor release of danger signals to be recognised by the immune system is triggered. As a result, new infections and re-infection can occur [4]. A prophylactic HPV vaccine should therefore induce a better immune response than natural infection by overcoming the challenges due to the pathogen (i.e. have the ability to block the virus at the site of entrance), hence induce higher level of antibodies, and provide longterm protection [4].

HBV infects hepatocytes and consists of a double-stranded circular DNA genome, an outer envelope protein (HBsAg), an inner nucleocapsid protein, (HBcAg), and a soluble small molecular weight protein (HBeAg) produced by the core gene. The HBsAg envelope protein can be shed and is also found as a non-infectious self-assembling tubular or spherical particle in the bloodstream of infected patients [5]. Overall eight genotypes of HBV are known [6,7].

In addition to challenges due to pathogen features, the challenges of HBV vaccination are also due to the host characteristics, i.e. poor immune response of pre-haemodialysis and haemodialysis patients to standard HBV vaccination as a consequence of their impaired immune system. This is of particular concern since these patients are at increased risk of HBV infection during dialysis procedures [8]. In this population, double dosage of vaccine in a 4 dose schedule is recommended, followed by regular booster when the antibody level declines below the protective level. This contrasts with the recommendations in healthy subjects, consisting of 3 or 4 doses with no boosters [9].

The need for improved vaccine formulations for challenging immunological requirements and populations led GSK Bio to develop HPV and HBV vaccines adjuvanted with the AS04 Adjuvant System. The choice of AS04 was based on the results from preclinical and clinical studies, which consistently showed a higher antibody response with the AS04-adjuvanted formulations as compared to aluminiumcontaining formulations [10-12].

Similarities and Differences between HPV and HBV Infections

HPV infection

HPV is mainly transmitted by sexual contact, and remains located in the epithelial cells of the mucosa or the skin. There is little, if any, exposure of the virus to the host’s immune system because HPV proteins are expressed at low levels and not secreted [13-15]. The natural infectious cycle of HPV is adapted to the differentiation program of the infected cell. Basal keratinocytes mature vertically through the epithelium to the cervical lumen. The time from infection to viral release is approximately 3 weeks, which coincides with the time for basal keratinocytes to undergo complete differentiation, desquamation and natural cell death. The adaptation of HPV to the differentiation program of keratinocytes is an important mechanism as it allows the virus to evade detection by the immune system. The virus by itself is not cytolytic, therefore natural cell death does not present a danger signal to the immune system nor it is accompanied by inflammation [2]. During maturation, the late proteins L1 and L2 are expressed to form capsids and viruses are only shed externally [16].

As a result of these and other host evasion mechanisms, the local innate immune responses aiming to control or eradicate the virus are attenuated, allowing the infection to become persistent [2,17]. Some of the viral antigens have cell-transforming properties that can lead to the development of benign or malignant tumours, if the infection persists [18]. HPV viral load measurement may also be predictive of future cervical neoplasia and a linear association between increasing grade of cervical intraepithelial neoplasia lesions and HPV-16 viral load has been noted [19].

HBV infection

HBV is a systemic pathogen with a specific tropism for the hepatocytes but it can also be found in the blood and in other cells and tissues [20]. The infection with HBV is a complex process and is still not fully understood [21]. A large amount of virus can be produced by infected liver cells without causing a cytopathic effect, even though up to 1012 virus particles may circulate in the bloodstream during infection. The infected cells become a target for the immune system causing liver cell damage and resulting clinical symptoms of hepatitis disease [20].

Acute infection may evolve into chronic infection if T cell responses to HBV are not induced or not capable of controlling the virus [22]. T cell responses to HBV antigens disappear gradually with the onset of chronic infection, probably because of exhaustion and/or tolerance induction [23]. The transition from acute to chronic infection appears to represent a failure of immune clearance of virus-infected cells and is marked by persistence of high levels of HBV DNA and HBsAg in serum [20]. HBV infection can therefore either lead to acute clinical hepatitis disease followed by clearance of the virus, or to the persistence of the virus and chronic, but often subclinical, infection. The latter type of infection can be maintained for many years and may lead in the long term to complications such as liver fibrosis or hepatocellular carcinoma (HCC). The inactive carrier state generally has a benign course. However, the infection can be reactivated either spontaneously or by immune suppression [24-26]. The re-activation of the infection can be abrupt and resemble acute hepatitis [27]. CHB is a lifelong infection, which evolves over time in response to changes in the balance between the immune response and the viral activity.

Progression of Chronic Infections with HBV and HPV to Malignant Cancers

Infections with HPV or HBV may result in the development of malignant tumours with a significant mortality rate.


Cervical cancer is the second most common cancer in women worldwide [3]. About 500,000 new cases of cervical carcinoma occur every year worldwide [28,29]. All cervical cancers are associated with HPV infection [29,30] and persistent infection with an oncogenic type of HPV is an important early precursor event in the progression to cervical precancerous lesions and cervical cancer [18,31-36]. A persistent infection is generally defined as the continued detection of viral DNA of the same HPV type in the cervix for at least 6–12 months [37-39].

HPV types are classified into low risk HPV, i.e., which do not lead to neoplastic transformation and high risk or oncogenic HPV, i.e., which are associated with the development of cancers. Among the 15 oncogenic HPV types [34,40-43], HPV types 16 and 18 cause approximately 70% of all cervical cancer cases worldwide [18,40], followed by 45, 31 and 33 which cause an additional 10% of cervical cancer cases [44]. HPV can also cause other non-cervical carcinomas such as head and neck cancer [45].

Infection by oncogenic HPV can evolve to low grade cervical intraepithelial lesions (CIN1), to high grade cervical intraepithelial neoplasias (CIN2 and CIN3), e.g. cancer in situ (CIS) and ultimately to invasive cervical carcinoma (CC). Only a small percentage will progress from CIN2 to CC and this process usually takes several years. At each stage, with the exception of CIS and CC, the infection may revert to the previous stage, although therapy is recommended from stage 2 onwards. In most cases total clearance of lesions and infection has been observed, but the rate of spontaneous clearance decreases with the severity of the precancerous lesions [46].


Worldwide, more than 350 million individuals are chronically infected with HBV and up to 40% of infected patients will develop serious complications [47-49].

About 600,000 deaths each year are due to HBV-related acute hepatitis, liver fibrosis or HCC [50]. CHB is the first cause of liver cancer worldwide and the primary cause for cancer in men in Asia [51]. HBV is the leading cause for HCC and core promoter mutations have been shown in many studies to be associated with increased risk of HCC and to precede HCC diagnosis [52].

It is well documented that the chance of an acute versus chronic infection is dependent on the age at infection. Young children who become infected with hepatitis B virus are the most likely to develop chronic infection. About 90% of infants infected during the first year of life and 30% to 50% of children infected between 1 and 4 years of age will develop chronic infection. The situation is different in adults. At the onset of HBV infection, 35% of adults show symptoms of acute hepatitis whereas the other 65% have sub-clinical disease [25]. About 5% of adults develop CHB, but the rates of chronicity are much higher in immune deficient individuals. About 60% of patients on haemodialysis develop CHB when infected with HBV compared to 5-10% of healthy adults [53,54].

Differences in Immune Responses after Natural Infection for HPV and HBV


As HPV infections are usually limited to their host cells, the keratinocytes, the virus is barely exposed to the systemic immune system due to the absence of a bloodstream phase and the host is unable to mount a strong antibody response. Innate cell-mediated immunity is the primary mechanism of defence for HPV infection, adaptive response comes into play at a later stage. Antibody levels induced by natural infection are very low, but the antibody levels increase in individuals with persistent infections [55]. Antibody levels observed after natural infection seem to be unreliable for long-term protection. Hence, it has been observed that seropositive individuals can be reinfected with the same type of HPV [56,57]. However, recent data from natural history evaluations show that the reduced risk of a new infection can be associated with high levels of antibodies [58]. The limited innate immune response, the low level of viral gene expression in the basal epithelium, and the lack of cytopathic effects result in a delayed adaptive immune response.

The degree of protection and the duration of immunity induced by natural incident infection are not known, but only 50–60% of women develop detectable serum antibodies to HPV after natural infection [17,59]. A cell-mediated immune response of effector T lymphocytes directed against the early E2 and E6 HPV proteins occurs first, as reflected by the infiltration of specific helper and cytotoxic T lymphocytes, macrophages, and the local production of proinflammatory cytokines [4,60,61]. Approximately 8 months after infection, low levels of neutralizing antibodies to the major capsid protein L1 may appear in the serum of infected individuals, and specific IgG and secretory IgA are found locally in the cervical mucosa, but at very low levels [62-64].


HPV immune response is distinct from what is observed with the HBV infection, where a rapid anamnestic response can occur upon virus challenge, even in the absence of detectable specific antibody titres at the time of infection [65]. One important difference between HPV and HBV viral infections is that HBV shows persistent viraemia during the course of the infection. The rapid presence of viral particles in the bloodstream allows the immune system to recognize the pathogen and to mount a rapid and strong response against the pathogen.

The immune response to HBV infection includes cellular response and the secretion of high levels of circulating antibodies to neutralize and control the pathogen [20,66,67]. During acute hepatitis B disease, a strong cytotoxic T lymphocyte (CTL) response is detected [68]. This CTL response is directed against multiple epitopes within the envelope, polymerase, HBc and HBe antigens [66,69-73] and leads to the destruction of hepatocytes.

During the early phase, Kuppfer cells, NK cells, NK T cells are activated in the liver and contribute to the early clearance of the virus through secretion of type 1 interferons [74].

Cell-mediated immunity is crucial for the control of HBV infection [20]. Strong virus-specific CD4+ and CD8+ T cell responses are induced during transient infection and these responses can persist for decades after viral clearance [75]. Patients who spontaneously recover from HBV infection typically mount vigorous specific CD4+ and CD8+ T cell responses whereas those with CHB have late, transient or narrowly focused T cell responses [66]. The continued presence of T cells suggest that HBV persists at low levels despite absence of detectable HBV DNA and presence of antibodies to HBsAg in serum [76]. Reactivation of hepatitis B during immunosuppressive therapy in people who had previously cleared an HBV infection has been amply documented [77,78].

The main similarities and differences for HPV and HBV infections are summarised in Table 1.

Similarities •Chronic infection can lead to cancer
Differences HPV HBV
  • Local infection at the mucosa
• Attenuation of immune mechanism
• Many viral subtypes
• Viral entry occurs rapidly, but infected cell shows no inflammation
• Virus elimination via natural cell clearance
• Innate immune response, late induction of adaptive response (low antibody levels after long exposure to infection)
• Natural immunity does not reliably prevent from infection
• Systemic infection
• Viral progression 1 to 6 months from infection to disease
• Strong immune response
• Neutralising antibodies and CTL activation
• Immune mechanisms in subjects who recovered from HBV infection provide lifelong immunity

Table 1: Similarities and differences HBV and HPV infection.

The Challenges of HPV and HBV Vaccinations


The mechanism of protection against HPV infection is not completely understood, but it has been shown in animal models that high levels of HPV-specific neutralising serum antibodies play an important role in preventing infection [79-81]. This provided the necessary evidence that a vaccine inducing neutralising antibodies could be developed for humans. These antibodies are not produced locally, but result from the transudation or exudation from serum to the cervical mucus. The levels of antibodies in the cervix have been shown to correlate with the levels of antibodies in the serum, supporting passive transfer of antibodies in the cervix (Figure 1) [82-84].


Figure 1: Transudation / Exudation.

In order to provide long-term protection against HPV infection and associated lesions, prophylactic HPV vaccines should elicit an appropriate immune response in terms of antibodies and memory B cells. The first challenge of HPV vaccination is to provide protective efficacy through a systemic immune response against a virus that enters only via the mucosal route and remains localized. The antibodies must not only reach the cervical mucosa, but they also need to be sustained at sufficient levels and in a timely and spatially orchestrated manner to neutralize the virus before it enters the cells. In that respect, antibody titres inferior or even close to those induced by natural HPV infection are unlikely to be sufficient. Currently, two prophylactic HPV vaccines are available (Table 2).

HPV vaccines
Product Manufacturer Description Adjuvant Lit
Cervarix GSK Biologicals Human papillomavirus (types 16, 18) recombinant vaccine AS04
(3-O-desacyl-4'- monophosphoryl lipid A adsorbed on aluminium hydroxide)
Gardasil® Merck & Co Human papillomavirus (types 6, 11, 16, 18) recombinant vaccine Amorphous aluminium hydroxyphosphate sulfate [161]
HBV vaccines
Product Manufacturer Antigen Adjuvant  
Engerix GSK Biologicals Recombinant vaccine containing the surface antigen (HBsAg) Aluminium hydroxide [162]
FENDrix GSK Biologicals Recombinant vaccine containing the surface antigen (HBsAg) AS04
(3-O-desacyl-4'- monophosphoryl lipid A adsorbed on aluminium phosphate)
Recombivax HB® Merck & Co Recombinant vaccine containing the surface antigen (HBsAg) Amorphous aluminium hydroxyphosphate sulfate [163]

The information given in this table is not meant to be exhaustive

Table 2: Examples of HBV and HPV vaccines.


Efficacious HBV vaccines are available for more than 20 years (Table 2). About 95% of healthy young individuals respond to vaccination with the standard hepatitis B vaccines. However, HBV infection is still a major health problem worldwide [85]. Compared to adults with normal immune status, pre-haemodialysis and haemodialysis patients have a suboptimal response to standard HBV vaccination with aluminium adjuvanted vaccines, because their immune system is impaired. These patients require double dosage of HBV vaccine and a four-dose schedule, followed by frequent boosters to maintain protection [86-90]. For that reason GSK Bio developed an alternative HBV vaccine formulation targeted to this specific population [91]. Up to 60% of infected patients on haemodialysis are not able to clear the virus and therefore become chronic HBV carriers [92]. Moreover, even though patients are vaccinated and appropriate measures to prevent transmission of the virus have been put in place, HBV outbreaks in dialysis centres still occur [93,94].

In the normal healthy population, long-term protection relies on immune memory in humans reaching anti-HBs concentrations ≥10 mIU/mL post vaccination.

For immunocompromised individuals, protection against HBV infection relies more on circulating antibodies [95]. Studies in haemodialysis patients showed that many patients with anti-HBs levels between 10 and 100 mIU/mL did not retain protective antibody level of ≥10 mIU/mL one year post vaccination. It has therefore been suggested that anti-HBs concentrations ≥100 mIU/mL represented a more reliable indicator after vaccination, allowing protection to last for one year post vaccination [95,96].

The main similarities and differences for HPV and HBV vaccine formulations as described above are summarised in Table 3.

Similarities •Acceptable safety profile
•Need for enhanced protection
•Long persistence of protection needed to prevent new infections
•Strong immune priming needed
•Vaccination prevents from disease but not necessarily from infection
Differences HPV HBV
  •Risk of re-infection or new infection
•Need of local protection with high antibody level at site of infection
•Need to prevent infection
•Antibodies migrate from serum to mucosa by transudation or exudation
•Role of B-memory and vaccine anamnestic response unknown up to now
•No serological correlate of protection identified
•Serological correlate of protection identified
•Role of B cell memory established, protection observed in absence of circulating antibodies
•Immunocompromised patients are in need of higher doses and of booster dose

Table 3: Similarities and differences for HBV and HPV vaccines.

The Role of B-Cell Memory in Long Term Protection

Naïve B lymphocytes differentiate into antigen-specific memory B cells and plasma cells after stimulation by the antigen through the B cell receptor followed by cognate T cell help. Memory B cells survive in secondary lymphoid organs in the absence of antigen and mediate secondary immune responses upon re-encounter with the antigen. Plasma cells are terminally differentiated cells that home to spleen and bone marrow and secrete high rates of antibodies. Traditionally, the induction of memory B cells is considered as a crucial factor for longterm vaccine-induced protection [4]. Recent studies have demonstrated a positive correlation between the frequency of antigen-specific B-cell memory and antigen-specific serum antibody levels in studies of vaccines against tetanus toxoid [97], smallpox [98] and hepatitis B [99].

The biology of plasma cells, which secrete these antibodies, is still not completely understood and under considerable debate [100]. Of particular interest for this discussion is the question about the respective role of memory B cells and long lived plasma cells in persistence of humoral response [97,101-103]. Three different concepts to explain persistence of humoral response have been postulated:

short-lived plasma cells are generated continuously from memory B cells, a process that would be driven by persisting antigen [103]

long-lived plasma cells with a defined half-life are generated from memory B cells, a process that would be activated by signals from cytokine receptors and Toll-like receptors by a new encounter with the pathogen [97,98]

plasma cells can stay for a long time in special survival niches in the bone marrow [100,102]. This mechanism is currently considered as the most important since depletion of memory B cell has been shown not to significantly impact level of circulating antibodies [104,105].

The generation of memory B-cells and their response to antigen recall are crucial factors for the long-term efficacy of vaccine-induced humoral protection. B-cell memory and its generation are poorly understood. The rapid clonal expansion of B-cells in the lymph node follicle leads to the formation of the germinal centre where the key event of affinity maturation for the generation of high-affinity B-cell receptors (BCR), and thus high-affinity antibodies, occurs. This event is critical for vaccines whose efficacy is dependent upon the generation of high-affinity neutralising serum IgG. At some point the maturing B-cells exit from the germinal centre and enter the long-term memory B-cell compartment. Upon antigen rechallenge, these memory cells rapidly expand and differentiate into plasma cells.

Testing for anti-HBs antibodies is often negative many years after vaccination, but protection is solid and long lasting though, as demonstrated in a follow-up study 20 years after vaccination of high risk infants in Thailand [106,107]. For HBV it has been demonstrated that postvaccination titres ≥10 mIU correlate with the induction of T-helper cell responses which mediate generation of B-cell memory. Natural exposure to HBV after vaccination therefore results in an anamnestic response that prevents disease symptoms from occurring and in many cases even infection [108]. Based on this observation it can be expected that a new HBV vaccine formulation inducing higher levels of serum antibodies will also have a major impact on the generation and longevity of B-cell memory in pre-haemodialysis and haemodialysis patients. For HPV the role of B-cell memory is still under discussion [10], but it seems to be very likely that in analogy to HBV, a higher initial vaccine response will correlate with a longer persistence of antibodies, enhanced B-cell memory and a higher anamnestic response.

Uncertainty remains as to whether reinfection or re-exposure to oncogenic HPV through the cervix or genital tract is capable of triggering antibody production from memory B cells to prevent infections with pathological consequences. Since HPV infection does not induce viraemia and resides within the cervical epithelium, an anamnestic response might not be a reliable mechanism of protection. Neutralising antibodies at the site and time of exposure are likely to provide the best protection against infection.

Because women are at risk for acquisition of HPV infection for as long as they are sexually active, vaccination needs to induce long-term protective efficacy. Serum neutralizing antibodies, which are known to transudate/exudate to the site of infection, are generally presumed to constitute the major basis of protection against HPV infection for prophylactic vaccines.

AS04 Adjuvant System in Vaccines against HBV and HPV

The careful selection of antigens and the addition of adjuvants to amplify the immune response is one of the most used approaches in vaccine design today. Many of recently developed vaccines contain purified antigens, obtained for example by recombinant technologies that have the advantages of a reduced reactogenicity as compared to the whole pathogen. However, the use of purified antigens do not always lead to the induction of an adequate immune response, as the purification process may have removed immunogenic components that are important in triggering the immune defence mechanisms [109]. The addition of adjuvants in that context proofs useful in ensuring a good immune response along with an acceptable reactogenicity and safety profile.

Adjuvants are substances with immunostimulatory properties [110-113]. Aluminium salts were the first to be registered for use in humans and are still the most widely used adjuvants in vaccines in all age populations [114,115]. Their mode of action has been shown to rely on several mechanisms such as local inflammation and an improved uptake of the antigen by the antigen presenting cells (APCs). Aluminium salts can induce a sufficient antibody response but they are poor activators of dendritic cells (one of the main tissue resident innate cells that can become antigen presenting cells) and they induce weak cellular response with a preferential Th2 pattern [116,117]. Recently, aluminium salts have been found to activate components of the inflammasome complex [118-120] by inducing uric acid [121], but the role of the inflammasome in mediating the adjuvant properties of aluminium salts is still a matter of debate [120].

Some adjuvants interact with the Toll-like receptors family (TLR), represented by transmembrane signalling proteins expressed on many cell types, in particular on immune cells such as dendritic cells, allowing the immune system to detect infection [122,123]. A TLR specific ligand activates a signalling pathway which results in cytokine secretion, up-regulation of co-stimulatory receptors and induction of host immune and inflammatory responses [124,125]. One of these TLR activating molecules, 3-O-desacyl-4’-monophosphoryl lipid A (MPL), is a derivative of a lipopolysaccharide (LPS) from the Re595 strain of Salmonella minnesota [126,127] and acts on the immune system as a TLR4 agonist [128-131]. MPL is capable of directly activating key innate immune mechanisms, including the activation of antigenpresenting cells and the induction of cytokines, such as TNFα and IL-6, which will ultimately enhance the adaptive immune response, i.e. induce T helper cells and B cell responses [132-134]. Activation of TLR4 by MPL stimulates the maturation of APCs and their migration to the lymph nodes. Thus, a higher amount of antigen is presented more efficiently to the B and T cells of the adaptive immune system resulting in an enhanced immune response to the vaccine antigen (Figure 2) [122,123,131,135].


Figure 2: Enhanced activation of immune system.

The AS04 Adjuvant System consists of MPL either adsorbed on aluminium hydroxide for the HPV vaccine or aluminium phosphate for the HBV vaccine [136].

Preclinical data with AS04

Several immunogenicity studies performed in mice, guinea pigs and monkeys have shown the effectiveness of MPL to potentiate both specific antibody and cellular immune responses after vaccination [127,137]. Studies in mice showed that recombinant yeast-derived HBsAg adjuvanted with AS04 was able to induce an overall increase in antibody titres compared to the classical adjuvantation with aluminium alone, both in young and elderly animals [12].

The immunogenicity of AS04-adjuvanted HPV vaccine was investigated in mice and monkeys and AS04 formulation showed significantly higher titres of HPV-specific antibodies than aluminium salt formulation. In order to evaluate the quality of the humoral response, specific HPV neutralizing antibodies were analyzed in monkeys. In these studies, compared to the same vaccine antigens formulated with aluminium hydroxide alone, the formulation with AS04 induced consistently higher antibody levels throughout the observation period and elicited also a higher frequency of HPV-16 and HPV-18 L1 VLP-specific memory B cells (2.2–5.2-fold) [10]. These preclinical data provided necessary supportive evidence to evaluate the AS04-adjuvanted formulations in clinical studies for both vaccines.

AS04 mode of action

Experiments in vivo and in vitro were performed to understand where and how AS04 interacts with the immune system and which types of immune cells are involved [138]. AS04 has to be administered at the same site as the antigen at the same time or within 24 hours to trigger a transient immune response localized to the injection site and the draining lymph nodes. During this period production of specific cytokines is increased leading to higher numbers of dendritic cells and moncytes acting as antigen presenting cells in the draining lymph nodes. In the draining lymph node increased activation of antigenspecific T-cells is observed. There was no evidence of direct stimulation of adaptive immune response cells by AS04, thus making a non-antigen specific immune response very unlikely. With the exception of the site of injection and the draining lymph node there was no evidence of systemic activation of other lymphatic organs such as the spleen or distant lymph nodes, confirming that the effect of the adjuvant is localised and transient. The results of the mode of action experiments are useful to explain the clinical immunogenicity and safety profile of the vaccine, as discussed below.

AS04-adjuvanted HPV-16/18 vaccine

Immunogenicity: In Phase II studies conducted in humans, the AS04-adjuvanted HPV-16/18 vaccine was shown to induce a higher and sustained anti-HPV-16/18 neutralising antibody response along with a higher frequency of memory B cells as compared to the same vaccine antigens formulated with aluminium salts [10]. Administration of the vaccine to HPV-naïve women aged 15 to 25 years elicited high and sustained persistence of neutralising antibody titres, with > 98% of women still seropositive up to 6.4 years after the first dose [139]. According to a mathematical modelling, the vaccine is predicted to generate sustained longevity of anti-HPV-16 and -18 antibody titres, both remaining substantially above those associated with natural infection and lasting for several decades in young women aged 15–25 years [140]. Available immunogenicity data up to 8.4 years are in line with published data on antibody persistence [141]. In women 15 to 55 years of age who received three doses of AS04-adjuvanted vaccine, the levels of anti-HPV-16 and -18 antibodies in serum were shown to highly correlate with those in cervicovaginal secretions at 18 months after the third vaccine dose. This indicate that parenteral administration of the AS04-adjuvanted vaccine can induce serum IgG antibodies that transudate to the cervical epithelium in women at all age [142].

In a comparative study between the AS04-adjuvanted HPV-16/18 vaccine and the quadrivalent HPV-6/11/16/18 vaccine adjuvanted with amorphous aluminium hydroxyphosphate sulfate salt, the AS04-adjuvanted HPV-16/18 vaccine induced significantly higher serum neutralizing antibody titres for HPV-16/18 after the three-dose vaccination course (p < 0.0001). Positivity rates for anti-HPV-16 and -18 neutralizing antibodies in cervicovaginal secretions and circulating HPV-16 and -18 specific memory B-cell frequencies were also higher after vaccination with the AS04-adjuvanted HPV-16/18 vaccine [143].

Efficacy: In a Phase IIb study, the HPV-16/18 AS04-adjuvanted vaccine was shown to be highly efficacious against persistent infections and pre-cancerous lesions associated with HPV-16/18. Cross-protective efficacy against incident infection with oncogenic HPV-45/31 was also observed [139]. The primary analysis of a large Phase III study in women 15 to 25 years of age confirmed the high efficacy against CIN2 or greater (CIN2+) associated with HPV types 16 and 18, which was up to 98% in an HPV naive cohort (HPV seronegative and DNA negative for oncogenic types) which approximates young adolescents before sexual debut [144]. The end of study analysis revealed that overall vaccine efficacy on CIN2+, irrespective of HPV type, was 64.9% [CI: 52.7 to 74.2] in this cohort. The corresponding value against CIN3+ was 93.2% [CI: 78.9 to 98.7] [145]. Cross-protection was observed against virological and/or histopathological endpoints for HPV-31, HPV-33 and HPV-45 [146].

Currently no studies are available where the efficacy of the AS04- adjuvanted HPV-16/18 vaccine and the HPV-6-11-16-18 vaccine are compared. Whether the differences observed in the immune profile of the two vaccines have an influence on the magnitude of protection in the long-term still remains to be determined.

AS04-adjuvanted HBV vaccine

The immunogenicity and safety of the AS04-adjuvanted HBV vaccine was assessed in haemodialysis patients and compared with double dose of a licensed aluminium adjuvanted HBV vaccine. In a study performed with haemodialysis and pre-haemodialysis patients aged more than 15 years, who were naive for HBV infection markers and with a documented creatinine clearance of ≤30 ml/min, it was shown that 91% of subjects who received the AS04-adjuvanted HBV vaccine (one dose containing 20 μg HBsAg administered at Month 0, 1, 2 and 6) and 84% in the control group (two doses containing 20 μg HBsAg each administered at Month 0, 1, 2 and 6) were seroprotected at Month 7. From month 1 to month 6, a significantly faster onset of protection with antibody concentrations of ≥10 mIU/ml was observed in the AS04-adjuvanted HBV vaccine group as compared to the control group. The percentage of subjects with antibody concentrations ≥100 mIU/ml was greater at all time points in the AS04-adjuvanted HBV vaccine group. At month 7, as already observed in healthy subjects, anti-HBs geometric mean concentrations were much higher in the AS04-adjuvanted HBV vaccine group (3559 mIU/ml [95% CI: 2130; 5847]) than in the control group (933 mIU/ml [95% CI: 516; 1688]) [11].

In an extension study, unselected patients were followed up to 42 months post vaccination. At Month 36 about 80% of the subjects in the AS04-adjuvanted HBV vaccine group were still seroprotected against HBV as compared with 51% in the control group. Similarly, at Month 42 about 78% of the subjects in the AS04-adjuvanted HBV vaccine group were still seroprotected against HBV as compared with 52% in the control group. These long term follow up data are consistent with the observation that pre-heamodialysis and haemodialysis patients loose more rapidly seroprotective levels of anti-HBs [147]. Therefore anti-HBs antibody concentrations have to be followed up regularly and most subjects need repeated booster doses of the vaccine. The decrease in seroprotection rate over time was significantly slower in the AS04- adjuvanted HBV vaccine group, and a booster dose was required less rapidly than in the standard HBV vaccine group. Indeed, fewer patients primed with AS04-adjuvanted HBV vaccine had to receive a booster dose during the follow-up period (16.7% versus 42.9 in control group; p=0.0098) [147].

The aim for both AS04-adjuvanted vaccines is to elicit an enhanced immune response with a long duration for their specific population. The benefits of the AS04 Adjuvant System for both vaccines are summarised in Table 4. The existence of an established serological correlate of protection for HBV allows the evaluation on how the enhanced immune response impacts the protection afforded by the HBV vaccine formulated with AS04.

High and sustained antibody titres in serum correlate with high antibody titres in mucosa
Sustained protection
Enhanced protection of high risk population
Longer persistence of high antibody levels
Less need for a booster
High neutralizing levels of antibody
Higher frequency of B-cell memory
Antibody persistence
Contributes to achieve needed immune profile to ensure protection

Table 4: Benefits of AS04 for the vaccines.

Safety of AS04-Adjuvanted Vaccines

Various preclinical toxicology evaluations did not indicate other findings for AS04 than local inflammation [12]. The safety of the AS04 has been evaluated in humans for more than 15 years. The AS04-based vaccines are generally well tolerated when evaluated during clinical development programmes. Clinical studies with AS04-based HPV and HBV vaccines showed a satisfactory and clinically acceptable reactogenicity and safety profile comparable to classic aluminiumadjuvanted vaccines [8,148,149]. The pooled safety analysis of AS04- adjuvanted HPV vaccines [149] showed no clinically relevant differences between both study groups for serious adverse events, pregnancy outcomes, and most solicited general symptoms (with the exception of myalgia, which was slightly higher in the AS04 group). Solicited local symptoms such as pain, redness, or swelling were more often reported for the AS04-adjuvanted HPV vaccine than compared with aluminium adjuvanted control vaccines. The increased local reactogenicity did not impact on vaccine compliance and this observation is in line with the experience with other adjuvanted vaccines. Since AS04 is a novel adjuvant with effects on the immune system, specific attention was given to adverse events of potential auto-immune origin in the clinical trials with AS04 containing vaccines. A large meta-analysis including all randomized and controlled studies with registered and candidate vaccines containing AS04 as Adjuvant System was performed. The integrated safety review based on more than 68.000 subjects for events of potential autoimmune aetiology revealed no statistically significant differences between the AS04-adjuvanted vaccine group and the control group with an observed event rate of approximately 0.5% for both study groups [150]. Post-marketing experience of more than 25 million AS04-adjuvanted vaccine doses distributed has confirmed an acceptable safety profile [151].

Other Strategies for Development of HPV and HBV Vaccines

HPV vaccines

Currently available HPV prophylactic vaccines contain VLP from oncogenic types HPV-16/18, the two most prevalent types in cervical cancer, which cause approximately 70% of cervical cancer One strategy for improving the coverage of the vaccine against HPVrelated disease is to increase the number of HPV types included in the vaccine formulation. Accordingly, a multivalent HPV vaccine with L1 VLP types 16, 18, 31, 33, 35, 45, 52, and 58 is undergoing clinical development [152]. Increasing the number of types in the vaccine however faces its own challenges, such as the potential for immune interference between the different types, as previously reported with many other vaccines [153]. Another approach under consideration is based on the L2 protein, which has the potential to generate broad protection through cross-protection [154]. Whether multivalent or L2 based vaccines will further increase the overall efficacy of the AS04 adjuvanted HPV vaccine against CIN3+ needs to be evaluated in the coming years.

Prophylactic vaccines have the potential to protect against new infections, but do not impact the progress of existing HPV infections or lesions. As a result, a therapeutic HPV vaccine would be warranted. Such a vaccine may reduce the incidence of cervical cancer by clearing early and/or late state infections by activating cellular immune responses in order to kill cancer cells which express foreign proteins, like the E6 and E7 HPV proteins.

Therapeutic HPV vaccines under development use technologies like protein vaccines or viral vectors [154]. A study with synthetic oncoproteins E6 and E7 of HPV-16 revealed that the vaccine was effective over a period of 12 to 24 months. A regression of HPV16 positive and high-grade vulvar intraepithelial neoplasia lesions in the majority of subjects was observed [155]. Another study vaccine for CIN3 immunotherapy consisting of a fusion heat shock protein covalently linked to the entire sequence of HPV 16 E7 showed efficacy in subjects infected with HPV types other than 16, suggesting crossreactivity [156]. A clinical trial with a modified recombinant vaccinia virus expressing E2 for the treatment of CIN2 and CIN3 lesions associated with oncogenic papillomavirus showed the the vaccine was very effective in stimulating the immune system against papillomavirus resulting in a regression of high-grade lesion [157].

HBV vaccines

Vaccines based on the preS/S epitope may elicit a rapid and higher seroprotection rate compared with the conventional HBsAg vaccines in risk groups [158]. Clinical trials with an HBV vaccine adjuvanted with immunostimulatory sequences containing repeating sequences of cytosine phosphoguanosine (CpG) dinucleotide motifs have shown high titres and sustained seroprotection in healthy and hyporesponsive populations [159]. Therapeutic HBV vaccines to target and induce HBV-specific T cell responses are another area of research currently being pursued [160].

Learnings for Future Developments

The current AS04 experience with these and other vaccines is showing new opportunities in vaccine development to address unmet medical needs. The Adjuvant System approach will play a prominent role for GSK Bio in the development of future vaccines. The experiences of GSK Bio collected during preclinical and clinical studies of AS04- adjuvanted vaccines can be summarised as follows:

1) Enhanced immune response needs to be translated in clinical benefits. This can easily be shown if an immune correlate of protection is available.

2) The presence of an adjuvant in the vaccine formulation needs to be justified by scientific data suggesting that the addition of an adjuvant may result in a clinical benefit.

3) Stronger innate immune stimulation is usually accompanied with increased reactogenicity, which however needs to remain within an acceptable range.

4) Safety concerns about triggering autoimmune diseases needs to be constantly addressed during preclinical and clinical development, and post licensure surveillance.

5) Mode of action studies of the used adjuvant are becoming more and more relevant to support the observed immunogenicity and safety profile of clinical studies.

6) The long-term benefits of enhanced immune response in term of clinical protection remains to be determined.


Adjuvant Systems have been developed in an effort to design new vaccines that would enable the induction of enhanced immune responses aiming to increased protection, while providing a clinically acceptable safety profile.

The selection of a vaccine formulation should be based on the characteristics of the pathogen, the target population and the medical need. The Adjuvant System technology is an additional option for the development of new vaccines against challenging diseases or for subjects with immune-deficient conditions where classical approaches have proven to be less effective. There are important differences for challenging diseases like HPV and HBV to consider, but AS04 has been shown to induce enhanced immune responses.

Experience based on the AS04-adjuvanted HPV-16/18 vaccine shows that the vaccine induced enhanced and sustained levels of neutralizing antibodies against HPV, which have been shown to transudate to the cervical mucosa, along with high cell-mediated immune response.

Experience with the AS04-adjuvanted hepatitis B vaccine in prehaemodialysis and haemodialysis patients has shown that the vaccine induced higher levels of specific antibodies and increased the percentage of subjects seroprotected after vaccination. In addition, the antibody decline over time was significantly lower in the AS04-adjuvanted vaccine group, resulting in fewer booster doses needed compared to the standard vaccines adjuvanted with aluminium salts only.

In conclusion, our experience with AS04 adjuvanted vaccines encourages further evaluation of other adjuvanted vaccines for currently unmet medical needs.

Literature Search

Data for this review were identified by searches of PubMed and references from relevant articles. The following search terms were used: “human papillomavirus”, “HPV”, “hepatitis B”, “HBV”, “adjuvants”, “aluminium”, “MPL”, “AS04”, “AAHS”, “immune response”, “innate immune response”, “adaptive immune response”, “long term protection”, “B cell”, “memory B cell”. Only articles in English were reviewed. No date restrictions were set in these searches.

Declaration of Funding

GSK Biologicals funded all costs associated with the development and the publishing of the present manuscript.

Conflict of Interest

Nathalie Garcon, Dominique Descamps, Maarten Leyssen, Michel Stoffel and Alberta Di Pasquale declare they are employees of GSK Biologicals.


We would like to acknowledge Markus Voges (GSK Biologicals) for assistance in preparing the manuscript, Géraldine Drevon, Geraldine Verplancke, and Slavka Baronikova (GSK Biologicals) for editorial assistance and coordination of manuscript development.


  1. de Villiers EM, Fauquet C, Broker TR, Bernard HU, zur Hausen H (2004) Classification of papillomaviruses. Virology 324: 17-27.
  2. Stanley MA, Pett MR, Coleman N (2007) HPV: from infection to cancer. Biochem Soc Trans 35: 1456-1460.
  3. Baseman JG, Koutsky LA (2006) The epidemiology of human papillomavirus infections. J Clin Virol 32: S16-24.
  4. Stanley M, Lowy DR, Frazer I (2006) Chapter 12: Prophylactic HPV vaccines: Underlying mechanisms. Vaccine 24: 106-113.
  5. Hoofnagle JH, Doo E, Liang TJ, Fleischer R, Lok AS (2007) Management of hepatitis B: summary of a clinical research workshop. Hepatology 45: 1056-1075.
  6. Chu CJ, Keeffe EB, Han SH, Perrillo RP, Min AD, et al. (2003) Hepatitis B virus genotypes in the United States: results of a nationwide study. Gastroenterology 125: 444-451.
  7. Magnius LO, Norder H (1995) Subtypes, genotypes and molecular epidemiology of the hepatitis B virus as reflected by sequence variability of the S-gene. Intervirology 38: 24-34.
  8. Beran J (2008) Safety and immunogenicity of a new hepatitis B vaccine for the protection of patients with renal insufficiency including pre-haemodialysis and haemodialysis patients. Expert Opin Biol Ther 8: 235-247.
  9. Leuridan E, Van Damme P (2011) Hepatitis B and the need for a booster dose. Clin Infect Dis 53:68-75.
  10. Giannini SL, Hanon E, Moris P, Van Mechelen M, Morel S, et al. (2006) Enhanced humoral and memory B cellular immunity using HPV16/18 L1 VLP vaccine formulated with the MPL/aluminium salt combination (AS04) compared to aluminium salt only. Vaccine 24: 5937-5949.
  11. Tong NK, Beran J, Kee SA, Miguel JL, Sánchez C, et al. (2005) Immunogenicity and safety of an adjuvanted hepatitis B vaccine in pre-hemodialysis and hemodialysis patients. Kidney Int 68: 2298-2303.
  12. Garcon N (2010) Preclinical development of AS04. Methods Mol Biol 626: 15-27.
  13. Crum CP, Nagai N, Levine RU, Silverstein S (1986) In situ hybridization analysis of HPV 16 DNA sequences in early cervical neoplasia. Am J Pathol 123: 174-182.
  14. Greenfield I, Nickerson J, Penman S, Stanley M (1991) Human papillomavirus 16 E7 protein is associated with the nuclear matrix. Proc Natl Acad Sci USA 88: 11217-1122.
  15. Stoler MH, Rhodes CR, Whitbeck A, Wolinsky SM, Chow LT, et al. (1992) Human papillomavirus type 16 and 18 gene expression in cervical neoplasias. Hum Pathol 23: 117-128.
  16. Muñoz N, Castellsagué X, de González AB, Gissmann L (2006) Chapter 1: HPV in the etiology of human cancer. Vaccine 24: S3/1-10.
  17. Schwarz TF, Leo O (2008) Immune response to human papillomavirus after prophylactic vaccination with AS04-adjuvanted HPV-16/18 vaccine: improving upon nature. Gynecol Oncol 110: S1-10.
  18. Bosch FX, Lorincz A, Muñoz N, Meijer CJ, Shah KV (2002) The causal relation between human papillomavirus and cervical cancer. J Clin Pathol 55: 244-265.
  19. Bory JP, Cucherousset J, Lorenzato M, Gabriel R, Quereux C, et al. (2002) Recurrent human papillomavirus infection detected with the hybrid capture II assay selects women with normal cervical smears at risk for developing high grade cervical lesions: a longitudinal study of 3,091 women. Int J Cancer 102: 519-525.
  20. Chisari FV, Ferrari C (1995) Hepatitis B virus Immunopathogenesis. Annu Rev Immunol 13: 29-60.
  21. Lok AS, Heathcote EJ, Hoofnagle JH (2001) Management of hepatitis B: 2000--summary of a workshop. Gastroenterology 120: 1828-1853.
  22. Maini MK, Boni C, Lee CK, Larrubia JR, Reignat S, et al. (2000) The role of virus-specific CD8(+) cells in liver damage and viral control during persistent hepatitis B virus infection. J Exp Med 191: 1269-1280.
  23. Rehermann B (2007) Chronic infections with hepatotropic viruses: mechanisms of impairment of cellular immune responses. Semin Liver Dis 27: 152-160.
  24. de Franchis,R; Meucci,G; Vecchi,M; Tatarella,M; Colombo,M et al. The Natural History of Asymptomatic Hepatitis B Surface Antigen Carriers. Ann Intern Med 118: 191-194.
  25. Hoofnagle JH, Shafritz DA, Popper H (1987) Chronic type B hepatitis and the "healthy" HBsAg carrier state. Hepatology 7: 758-763.
  26. Manno M, Cammà C, Schepis F, Bassi F, Gelmini R, et al. (2004) Natural history of chronic HBV carriers in northern Italy: morbidity and mortality after 30 years. Gastroenterology 127: 756-763.
  27. Chu CM (2000) Natural history of chronic hepatitis B virus infection in adults with emphasis on the occurrence of cirrhosis and hepatocellular carcinoma. J Gastroenterol Hepatol 15 Suppl: E25-E30.
  28. Bosch FX, Manos MM, Muñoz N, Sherman M, Jansen AM, et al. (1995) Prevalence of human papillomavirus in cervical cancer: a worldwide perspective. J Natl Cancer Inst 87: 796-802.
  29. Parkin DM, Bray F, Ferlay J, Pisani P (2005) Global cancer statistics, 2002. CA Cancer J Clin 55: 74-108.
  30. Franco EL, Harper DM (2005) Vaccination against human papillomavirus infection: a new paradigm in cervical cancer control. Vaccine 23: 2388-2394.
  31. Kjaer SK, van den Brule AJ, Bock JE, Poll PA, Engholm G, et al. (1996) Human papillomavirus--the most significant risk determinant of cervical intraepithelial neoplasia. Int J Cancer 65: 601-606.
  32. Kjaer SK, van den Brule AJ, Paull G, Svare EI, Sherman ME, et al. (2002) Type specific persistence of high risk human papillomavirus (HPV) as indicator of high grade cervical squamous intraepithelial lesions in young women: population based prospective follow up study. Br Med J 325: 572-578.
  33. Schlecht NF, Kulaga S, Robitaille J, Ferreira S, Santos M, et al. (2001) Persistent human papillomavirus infection as a predictor of cervical intraepithelial neoplasia. JAMA 286: 3106-3114.
  34. Walboomers JM, Jacobs MV, Manos MM, Bosch FX, Kummer JA, et al. (1999) Human papillomavirus is a necessary cause of invasive cervical cancer worldwide. J Pathol 189: 12-19.
  35. Wallin KL, Wiklund F, Angström T, Bergman F, Stendahl U, et al. (1999) Type-specific persistence of human papillomavirus DNA before the development of invasive cervical cancer. N Engl J Med 341: 1633-1638.
  36. Zur Hausen H (1991) Human papillomaviruses in the pathogenesis of anogenital cancer. Virology 184: 9-13.
  37. Cuschieri KS, Cubie HA, Whitley MW, Gilkison G, Arends MJ, et al. (2005) Persistent high risk HPV infection associated with development of cervical neoplasia in a prospective population study. J Clin Pathol 58: 946-950.
  38. Ho GY, Burk RD, Klein S, Kadish AS, Chang CJ, et al. (1995) Persistent genital human papillomavirus infection as a risk factor for persistent cervical dysplasia. J Natl Cancer Inst 87: 1365-1371.
  39. Trottier H, Mahmud SM, Lindsay L, Jenkins D, Quint W, et al. (2009) Persistence of an incident human papillomavirus infection and timing of cervical lesions in previously unexposed young women. Cancer Epidemiol Biomarkers Prev 18: 854-862.
  40. Cogliano V, Baan R, Straif K, Grosse Y, Secretan B, et al. (2005) Carcinogenicity of human papillomaviruses. Lancet Oncol 6: 204.
  41. de Villiers EM, Fauquet C, Broker TR, Bernard HU, zur Hausen H (2004) Classification of papillomaviruses. Virology 324: 17-27.
  42. Muñoz N, Bosch FX, de Sanjose S, Herrero R, Castellsagué X, et al. (2003) Epidemiologic classification of human papillomavirus types associated with cervical cancer. N Engl J Med 348: 518-527.
  43. Schiffman M, Herrero R, Desalle R, Hildesheim A, Wacholder S, et al. (2005) The carcinogenicity of human papillomavirus types reflects viral evolution. Virology 337: 76-84.
  44. Muñoz N, Bosch FX, Castellsagué X, Díaz M, de Sanjose S, et al. (2004) Against which human papillomavirus types shall we vaccinate and screen? The international perspective. Int J Cancer 111: 278-285.
  45. Psyrri A, DiMaio D (2008) Human papillomavirus in cervical and head-and-neck cancer. Nat Clin Pract Oncol 5: 24-31.
  46. Hebner CM, Laimins LA (2006) Human papillomaviruses: basic mechanisms of pathogenesis and oncogenicity. Rev Med Virol 16: 83-97.
  47. Wright TL Introduction to chronic hepatitis B infection. Am J Gastroenterol S1-6.
  48. Shepard CW, Simard EP, Finelli L, Fiore AE, Bell BP (2006) Hepatitis B virus infection: epidemiology and vaccination. Epidemiol Rev 28: 112-125
  49. YuMC, Yuan JM, Govindarajan S, Ross RK (2000) Epidemiology of hepatocellular carcinoma. Can J Gastroenterol 14: 703-709
  50. Yim HJ, Lok ASF (2006) Natural history of chronic hepatitis B virus infection: what we knew in 1981 and what we know in 2005. Hepatology 43: S173-S181
  51. Girndt M, Kohler H (2002) Hepatitis B virus infection in hemodialysis patients. Semin Nephrol 22: 340-350.
  52. Zacks SL, Fried MW (2001) Hepatitis B and C and renal failure. Infect Dis Clin North Am 15: 877-899
  53. de Gruijl TD, Bontkes HJ, Walboomers JMM, Schiller JT, Stukart MJ, et al. (1997) Immunoglobulin G responses against human papillomavirus type 16 virus-like particles in a prospective nonintervention cohort study of women with cervical intraepithelial neoplasia. J Natl Cancer Inst 89: 630-638
  54. Viscidi RP, Schiffman M, Hildesheim A, Herrero R, Castle PE, et al. (2004) Seroreactivity to human papillomavirus (HPV) types 16 18 or 31 and risk of subsequent HPV infection: results from a population-based study in Costa Rica. Cancer Epidemiol Biomarkers Prev 13: 324-327
  55. Viscidi RP, Snyder B, Cu-Uvin S, Hogan JW, Clayman B, et al. (2005) Human papillomavirus capsid antibody response to natural infection and risk of subsequent HPV infection in HIV-positive and HIV-negative women. Cancer Epidemiol.Biomarkers Prev 14: 283-288
  56. Safaeian M, Porras C, Schiffman M, Rodriguez AC, Wacholder S, et al. (2010) Epidemiological study of anti-HPV16/18 seropositivity and subsequent risk of HPV16 and -18 infections. J Natl Cancer Inst 102: 1653-1662
  57. Carter JJ, Koutsky LA, Hughes JP, Lee SK, Kuypers J, et al. (2000) Comparison of human papillomavirus types 16, 18, and 6 capsid antibody responses following incident infection. J Infect Dis 181: 1911-1919
  58. de Gruijl TD, Bontkes HJ, Walboomers JM, Stukart MJ, Doekhie FS, et al. (1998) Differential T helper cell responses to human papillomavirus type 16 E7 related to viral clearance or persistence in patients with cervical neoplasia: a longitudinal study. Cancer Res 58: 1700-1706
  59. van der Burg SH, Piersma SJ, de Jong A, van der Hulst JM, Kwappenberg KM, et al. (2007) Association of cervical cancer with the presence of CD4+ regulatory T cells specific for human papillomavirus antigens. Proc Natl Acad Sci USA 104: 12087-12092
  60. Bontkes HJ, de Gruijl TD, Walboomers JM, Schiller JT, Dillner J, et al. (1999) Immune responses against human papillomavirus (HPV) type 16 virus-like particles in a cohort study of women with cervical intraepithelial neoplasia. II. Systemic but not local IgA responses correlate with clearance of HPV-16. J Gen Virol 80: 409-417
  61. Passmore JA, Marais DJ, Sampson C, Allan B, Parker N, et al. (2007) Cervicovaginal oral and serum IgG and IgA responses to human papillomavirus type 16 in women with cervical intraepithelial neoplasia. J Med Virol 79: 1375-1380
  62. Rocha-Zavaleta L, Pereira-Suarez AL, Yescas G, Cruz-Mimiaga RM, Garcia-Carranca A, et al. (2003) Mucosal IgG and IgA responses to human papillomavirus type 16 capsid proteins in HPV16-infected women without visible pathology. Viral Immunol 16: 159-168.
  63. Einstein MH, Schiller JT, Viscidi RP, Strickler HD, Coursaget P, et al. (2009) Clinician's guide to human papillomavirus immunology: knowns and unknowns. Lancet Infect Dis 9: 347-356.
  64. Bertoletti A, Naoumov NV (2003) Translation of immunological knowledge into better treatments of chronic hepatitis B. J Hepatology 39: 115-124
  65. Rehermann B, Nascimbeni M (2005) Immunology of hepatitis B virus and hepatitis C virus infection. Nat Rev Immunol 5: 215-229.
  66. Ferrari C, Penna A, Bertoletti A, Valli A, Degli Antoni A, et al. (1990) Cellular immune response to hepatitis B virus-encoded antigens in acute and chronic hepatitis B virus infection. J Immunol 145: 3442-3449.
  67. Ferrari C, Bertoletti A, Penna A, Cavalli A, Valli A, et al. (1991) Identification of immunodominant T cell epitopes of the hepatitis B virus nucleocapsid antigen. J Clin Invest 88: 214-222.
  68. Missale G, Redeker A, Person J, Fowler P, Guilhot S, et al. (1993) HLA-A31- and HLA-Aw68-restricted cytotoxic T cell responses to a single hepatitis B virus nucleocapsid epitope during acute viral hepatitis. J Exp Med 177: 751-762.
  69. Nayersina R, Fowler P, Guilhot S, Missale G, Cerny A, et al. (1993) HLA A2 restricted cytotoxic T lymphocyte responses to multiple hepatitis B surface antigen epitopes during hepatitis B virus infection. J Immunol 150: 4659-4671
  70. Penna A, Chisari FV, Bertoletti A, Missale G, Fowler P, et al. (1991) Cytotoxic T lymphocytes recognize an HLA-A2-restricted epitope within the hepatitis B virus nucleocapsid antigen. J Exp Med 174: 1565-1570.
  71. Penna A, Fowler P, Bertoletti A, Guilhot S, Moss B, et al. (1992) Hepatitis B virus (HBV)-specific cytotoxic T-cell (CTL) response in humans: characterization of HLA class II-restricted CTLs that recognize endogenously synthesized HBV envelope antigens. J Virol 66: 1193-1198.
  72. Wieland S, Thimme R, Purcell RH, Chisari FV (2004) Genomic analysis of the host response to hepatitis B virus infection. Proc Natl Acad Sci USA 101: 6669-6674.
  73. Rehermann B, Ferrari C, Pasquinelli C, Chisari FV (1996) The hepatitis B virus persists for decades after patients' recovery from acute viral hepatitis despite active maintenance of a cytotoxic T-lymphocyte response. Nat Med 2: 1104-1108.
  74. Liang TJ, Baruch Y, Ben-Porath E, Enat R, Bassan L, et al. (1991) Hepatitis B virus infection in patients with idiopathic liver disease. Hepatology 13: 1044-1051.
  75. Lau GK, Yiu HH, Fong DY, Cheng HC, Au WY, et al. (2003) Early is superior to deferred preemptive lamivudine therapy for hepatitis B patients undergoing chemotherapy. Gastroenterology 125: 1742-1749.
  76. Lok AS, Liang RH, Chiu EK, Wong KL, Chan TK, et al. (1991) Reactivation of hepatitis B virus replication in patients receiving cytotoxic therapy. Report of a prospective study. Gastroenterology 100: 182-188.
  77. Christensen ND, Reed CA, Cladel NM, Han R, Kreider JW (1996) Immunization with viruslike particles induces long-term protection of rabbits against challenge with cottontail rabbit papillomavirus. J Virol 70: 960-965.
  78. Day PM, Thompson CD, Buck CB, Pang YY, Lowy DR, et al. (2007) Neutralization of human papillomavirus with monoclonal antibodies reveals different mechanisms of inhibition. J Virol 81: 8784-8792.
  79. Suzich JA, Ghim S-J, Palmer-Hill FJ, White WI, Tamura JK, et al. (1995) Systemic immunization with papillomavirus L1 protein completely prevents the development of viral mucosal papillomas. Proc Natl Acad Sci U S A 92: 11553-11557.
  80. Kemp TJ, Hildesheim A, Falk RT, Schiller JT, Lowy DR, et al. (2008) Evaluation of two types of sponges used to collect cervical secretions and assessment of antibody extraction protocols for recovery of neutralizing anti-human papillomavirus type 16 antibodies. Clin Vaccine Immunol 15: 60-64.
  81. Nardelli-Haefliger D, Wirthner D, Schiller JT, Lowy DR, Hildesheim A, et al. (2003) Specific antibody levels at the cervix during the menstrual cycle of women vaccinated with human papillomavirus 16 virus-like particles. J Natl Cancer Inst 95: 1128-1137.
  82. Schiller JT, Davies P (2004) Delivering on the promise: HPV vaccines and cervical cancer. Nat Rev Microbiol 2: 343-347.
  83. Lok AS (2005) The maze of treatments for hepatitis B. N Engl J Med 352: 2743-2746.
  84. Bruguera M, Cremades M, Mayor A, Sanchez Tapias JM, Rodes J (1987) Immunogenicity of a recombinant hepatitis B vaccine in haemodialysis patients. Postgrad Med J 63 Suppl 2: 155-158.
  85. Bruguera M, Rodicio JL, Alcazar JM, Oliver A, Del RG, et al. (1990) Effects of different dose levels and vaccination schedules on immune response to a recombinant DNA hepatitis B vaccine in haemodialysis patients. Vaccine 8: S47-S49.
  86. Chang PC, Schrander-van der Meer AM, van Dorp WT, van LE (1996) Intracutaneous versus intramuscular hepatitis B vaccination in primary non-responding haemodialysis patients. Nephrol Dial Transplant 11: 191-193.
  87. van Geelen JA, Schalm SW, de Visser EM, Heijtink RA (1987) Immune response to hepatitis B vaccine in hemodialysis patients. Nephron 45: 216-218.
  88. Waite NM, Thomson LG, Goldstein MB (1995) Successful vaccination with intradermal hepatitis B vaccine in hemodialysis patients previously nonresponsive to intramuscular hepatitis B vaccine. J Am Soc Nephrol 5: 1930-1934.
  89. Chonchol M (2006) Neutrophil dysfunction and infection risk in end-stage renal disease. Semin Dial 19: 291-296.
  90. Ribot S, Rothstein M, Goldblat M, Grasso M (1979) Duration of hepatitis B surface antigenemia (HBs Ag) in hemodialysis patients. Arch Intern Med 139: 178-180.
  91. Hutin YJF, Goldstein ST, Varma JK, O'Dair JB, Mast EE, et al. (1999) An outbreak of hospital-acquired hepatitis B virus infection among patients receiving chronic hemodialysis. Infect Control Hosp Epidemiol 20: 731-735.
  92. Igaki N, Nakaji M, Moriguchi R, Akiyama H, Tamada F, et al. (2003) An outbreak of fulminant hepatitis B in immunocompromised hemodialysis patients. J Gastroenterol 38: 968-976.
  93. Navarro JF, Teruel JL, Mateos ML, Marcen R, Ortuno J (1996) Antibody level after hepatitis B vaccination in hemodialysis patients: Influence of hepatitis C virus infection. Am J Nephrol 16: 95-97.
  94. Sezer S, Ozdemir FN, Guz G, Arat Z, Çolak T, et al. (2000) Factors influencing response to hepatitis B virus vaccination in hemodialysis patients. Transplant Proc 32: 607-608.
  95. Bernasconi NL, Traggiai E, Lanzavecchia A (2002) Maintenance of serological memory by polyclonal activation of human memory B cells. Science 298: 2199-2202.
  96. Traggiai E, Puzone R, Lanzavecchia A (2003) Antigen dependent and independent mechanisms that sustain serum antibody levels. Vaccine 21: S2-35-S2/37.
  97. Banatvala J, Van Damme P, Oehen S (2000) Lifelong protection against hepatitis B: the role of vaccine immunogenicity in immune memory. Vaccine 19: 877-885.
  98. Radbruch A, Muehlinghaus G, Luger EO, Inamine A, Smith KG, et al. (2006) Competence and competition: the challenge of becoming a long-lived plasma cell. Nat Rev Immunol 6: 741-750.
  99. Ahmed R, Gray D (1996) Immunological memory and protective immunity: understanding their relation. Science 272: 54-60
  100. Manz RA, Thiel A, Radbruch A (1997) Lifetime of plasma cells in the bone marrow. Nature 388: 133-134.
  101. Zinkernagel RM, Bachmann MF, Kündig TM, Oehen S, Pirchet H, et al. (1996) On immunological memory. Annu Rev Immunol 14: 333-367.
  102. Ahuja A, Anderson SM, Khalil A, Shlomchik MJ (2008) Maintenance of the plasma cell pool is independent of memory B cells. Proc Natl Acad Sci U S A 105: 4802-4807.
  103. DiLillo DJ, Hamaguchi Y, Ueda Y, Yang K, Uchida J, et al. (2008) Maintenance of long-lived plasma cells and serological memory despite mature and memory B cell depletion during CD20 immunotherapy in mice. J Immunol 180: 361-371.
  104. Poovorawan Y, Chongsrisawat V, Theamboonlers A, Bock HL, Leyssen M, et al. (2010) Persistence of antibodies and immune memory to hepatitis B vaccine 20 years after infant vaccination in Thailand. Vaccine 28: 730-736.
  105. Poovorawan Y, Chongsrisawat V, Theamboonlers A, Leroux-Roels G, Kuriyakose S, et al. (2011) Evidence of protection against clinical and chronic hepatitis B infection 20 years after infant vaccination in a high endemicity region. J Viral Hepat 18: 369-375.
  106. Plotkin SA (2001) Immunologic correlates of protection induced by vaccination. Pediatr Infect Dis J 20: 63-75
  107. Matzinger P (2002) The danger model: a renewed sense of self. Science 296: 301-305.
  108. Cox JC, Coulter AR (1997) Adjuvants--a classification and review of their modes of action. Vaccine 15: 248-256.
  109. Engers H, Kieny MP, Malhotra P, Pink JR (2003) Third meeting on Novel Adjuvants Currently in or Close to Clinical Testing World Health Organization--Organisation Mondiale de la Sante, Fondation Merieux, Annecy, France, 7-9 January 2002. Vaccine 21: 3503-3524.
  110. O'Hagan DT, MacKichan ML, Singh M (2001) Recent developments in adjuvants for vaccines against infectious diseases. Biomol Eng 18: 69-85.
  111. O'Hagan DT, Valiante NM (2003) Recent advances in the discovery and delivery of vaccine adjuvants. Nat Rev Drug Discov 2: 727-735.
  112. Glenny AT, Buttle GA, Stevens MF (1931) Rate of disappearance of diphtheria toxoid injected into rabbits and guinea pigs: toxoid precipitated with alum. J Pathol 34: 267-275.
  113. Ramon G (1926) Procédés pour accroître la production des antitoxines. Ann Inst Pasteur 40: 1-10.
  114. Brewer JM (2006) (How) do aluminium adjuvants work? Immunol Lett 102: 10-15.
  115. Lindblad EB (2004) Aluminium adjuvants-in retrospect and prospect. Vaccine 22: 3658-3668.
  116. Eisenbarth SC, Colegio OR, O'Connor W, Sutterwala FS, Flavell RA (2008) Crucial role for the Nalp3 inflammasome in the immunostimulatory properties of aluminium adjuvants. Nature 453: 1122-1126.
  117. Lambrecht BN, Kool M, Willart MA, Hammad H (2009) Mechanism of action of clinically approved adjuvants. Curr Opin Immunol 21: 23-29.
  118. Marrack P, McKee AS, Munks MW (2009) Towards an understanding of the adjuvant action of aluminium. Nat Rev Immunol 9: 287-293.
  119. Kool M, Soullié T, van Nimwegen M, Willart MA, Muskens F, et al. (2008) Alum adjuvant boosts adaptive immunity by inducing uric acid and activating inflammatory dendritic cells. J Exp Med 205: 869-882.
  120. Akira S, Takeda K, Kaisho T (2001) Toll-like receptors: critical proteins linking innate and acquired immunity. Nat Immunol 2: 675-680.
  121. Janssens S, Beyaert R (2003) Role of Toll-like receptors in pathogen recognition. Clin Microbiol Rev 16: 637-646.
  122. Iwasaki A, Medzhitov R (2004) Toll-like receptor control of the adaptive immune responses. Nat Immunol 5: 987-995.
  123. Trinchieri G, Sher A (2007) Cooperation of Toll-like receptor signals in innate immune defence. Nat Rev Immunol 7: 179-190.
  124. Johnson AG, Tomai M, Solem L, Beck L, Ribi E (1987) Characterization of a nontoxic monophosphoryl lipid A. Rev Infect Dis 5: S512-516.
  125. Ulrich JT, Myers KR (1995) Monophosphoryl lipid A as an adjuvant. Past experiences and new directions. Pharm Biotechnol 6: 495-524.
  126. Baldridge JR, McGowan P, Evans JT, Cluff C, Mossman S, et al. (2004) Taking a Toll on human disease: Toll-like receptor 4 agonists as vaccine adjuvants and monotherapeutic agents. Expert Opin Biol Ther 4: 1129-1138.
  127. Hirschfeld M, Ma Y, Weis JH, Vogel SN, Weis JJ (2000) Cutting edge: repurification of lipopolysaccharide eliminates signaling through both human and murine toll-like receptor 2. J Immunol 165: 618-622.
  128. Medzhitov R, Preston-Hurlburt P, Janeway CA Jr (1997) A human homologue of the Drosophila Toll protein signals activation of adaptive immunity. Nature 388: 394-397.
  129. Tapping RI, Akashi S, Miyake K, Godowski PJ, Tobias PS (2000) Toll-like receptor 4, but not toll-like receptor 2, is a signaling receptor for Escherichia and Salmonellalipopolysaccharides. J Immunol 165: 5780-5787.
  130. De Becker G, Moulin V, Pajak B, Bruck C, Francotte M, et al. (2000) The adjuvant monophosphoryl lipid A increases the function of antigen-presenting cells. Int Immunol 12: 807-815
  131. Ismaili J, Rennesson J, Aksoy E, Vekemans J, Vincart B, et al. (2002) Monophosphoryl lipid A activates both human dendritic cells and T cells. J Immunol 168: 926-932.
  132. Martin M, Michalek SM, Katz J (2003) Role of innate immune factors in the adjuvant activity of monophosphoryl lipid A. Infect Immun 71: 2498-2507.
  133. Schnare M, Barton GM, Holt AC, Takeda K, Akira S, et al. (2001) Toll-like receptors control activation of adaptive immune responses. Nat Immunol 2: 947-950.
  134. Garçon N, Chomez P, Van Mechelen M (2007) GlaxoSmithKline Adjuvant Systems in vaccines: concepts, achievements and perspectives. Expert Rev Vaccines 6: 723-739.
  135. Tomai MA, Johnson AG (1989) T cell and interferon-gamma involvement in the adjuvant action of a detoxified endotoxin. J Biol Response Mod 8: 625-643.
  136. Didierlaurent AM, Morel S, Lockman L, Giannini SL, Bisteau M, et al. (2009) AS04, an Aluminum Salt- and TLR-4 Agonist-Based Adjuvant System, Induces a Transient Localized Innate Immune Response Leading to Enhanced Adaptive Immunity. J Immunol 183: 6186-6197.
  137. Romanowski B, de Borba PC, Naud PS, Roteli-Martins CM, De Carvalho NS, et al. (2009) Sustained efficacy and immunogenicity of the human papillomavirus (HPV)-16/18 AS04-adjuvanted vaccine: analysis of a randomised placebo-controlled trial up to 6.4 years. Lancet 374: 1975-1985.
  138. David MP, Van Herck K, Hardt K, Tibaldi F, Dubin G, et al. (2009) Long-term persistence of anti-HPV-16 and -18 antibodies induced by vaccination with the AS04-adjuvanted cervical cancer vaccine: modeling of sustained antibody responses. Gynecol Oncol 115: S1-6.
  139. Roteli-Martins CM, Naud P, Borba P, Teixeira J, De Carvalho N, et al. Sustained Immunogenicity and Efficacy of the HPV-16/18 AS04 adjuvanted Vaccine: Follow-up to 8.4 years. The 28th Annual Meeting of the European Society for Paediatric Infectious Diseases, France.
  140. Schwarz TF, Spaczynski M, Schneider A, Wysocki J, Galaj A, et al. (2009) Immunogenicity and tolerability of an HPV-16/18 AS04-adjuvanted prophylactic cervical cancer vaccine in women aged 15-55 years. Vaccine 27: 581-587.
  141. Einstein MH, Baron M, Levin MJ, Chatterjee A, Edwards RP, et al. (2009) Comparison of the immunogenicity and safety of Cervarixä and Gardasil® human papillomavirus (HPV) cervical cancer vaccines in healthy women aged 18-45 years. Hum Vaccin 5: 705-719.
  142. Paavonen J, Naud P, Salmerón J, Wheeler CM, Chow SN, et al. (2009) Efficacy of human papillomavirus (HPV)-16/18 AS04-adjuvanted vaccine against cervical infection and precancer caused by oncogenic HPV types (PATRICIA): final analysis of a double-blind, randomised study in young women. Lancet 374: 301-314.
  143. Lehtinen M, Paavonen J, Wheeler CM, Jaisamrarn U, Garland SM, et al. (2012) Overall efficacy of HPV-16/18 AS04-adjuvanted vaccine against grade 3 or greater cervical intraepithelial neoplasia: 4-year end-of-study analysis of the randomised, double-blind PATRICIA trial. Lancet Oncol 13: 89-99.
  144. Wheeler CM, Castellsagué X, Garland SM, Szarewski A, Paavonen J, et al. (2012) Cross-protective efficacy of HPV-16/18 AS04-adjuvanted vaccine against cervical infection and precancer caused by non-vaccine oncogenic HPV types: 4-year end-of-study analysis of the randomised, double-blind PATRICIA trial. Lancet Oncol 13: 100-110.
  145. Kong NC, Beran J, Kee SA, Miguel JL, Sánchez C, et al. (2008) A new adjuvant improves the immune response to hepatitis B vaccine in hemodialysis patients. Kidney Int 73: 856-862.
  146. Boland G, Beran J, Lievens M, Sasadeusz J, Dentico P, et al. (2004) Safety and immunogenicity profile of an experimental hepatitis B vaccine adjuvanted with AS04. Vaccine 23: 316-320.
  147. Descamps D, Hardt K, Spiessens B, Izurieta P, Verstraeten T, et al. (2009) Safety of human papillomavirus (HPV)-16/18 AS04-adjuvanted vaccine for cervical cancer prevention: A pooled analysis of 11 clinical trials. Hum Vaccin 5: 332-340.
  148. Verstraeten T, Descamps D, David MP, Zahaf T, Hardt K, et al. (2008) Analysis of adverse events of potential autoimmune aetiology in a large integrated safety database of AS04 adjuvanted vaccines. Vaccine 26: 6630-6638.
  149. MHRA (2011) Cervarix (HPV vaccine): Update on UK safety covering the first two years of the HPV immunisation programme.
  150. NIH (2011) A Phase III Clinical Trial to Study the Immunogenicity, Tolerability, and Manufacturing Consistency of V503.
  151. Dagan R, Poolman JT, Zepp F (2008) Combination vaccines containing DTPa-Hib: impact of IPV and coadministration of CRM197 conjugates. Expert Rev Vaccines 7: 97-115
  152. Trimble CL, Frazer IH (2009) Development of therapeutic HPV vaccines. Lancet Oncol 10: 975-980.
  153. Kenter GG, Welters MJ, Valentijn AR, Lowik MJ, Berends-van der Meer DM, et al. (2009) Vaccination against HPV-16 oncoproteins for vulvar intraepithelial neoplasia. N Engl J Med 361: 1838-1847.
  154. Einstein MH, Kadish AS, Burk RD, Kim MY, Wadler S, et al. (2007) Heat shock fusion protein-based immunotherapy for treatment of cervical intraepithelial neoplasia III. Gynecol Oncol 106: 453-460.
  155. Garcia-Hernandez E, Gonzalez-Sanchez JL, Andrade-Manzano A, Contreras ML, Padilla S, et al. (2006) Regression of papilloma high-grade lesions (CIN 2 and CIN 3) is stimulated by therapeutic vaccination with MVA E2 recombinant vaccine. Cancer Gene Ther 13: 592-597.
  156. Rapicetta M, D'Ugo E, Argentini C, Catone S, Canitano A, et al. (2009) New perspectives for hepatitis B vaccines and immunization. Vaccine 27: 3271-3275.
  157. Barry M, Cooper C (2007) Review of hepatitis B surface antigen-1018 ISS adjuvant-containing vaccine safety and efficacy. Expert Opin Biol Ther 7: 1731-1737.
  158. Vandepapeliere P, Horsmans Y, Moris P, Van Mechelen M, Janssens M, et al. (2008) Vaccine adjuvant systems containing monophosphoryl lipid A and QS21 induce strong and persistent humoral and T cell responses against hepatitis B surface antigen in healthy adult volunteers. Vaccine 26: 1375-1386.
  159. Castellsague X, Munoz N, Pitisuttithum P, Ferris D, Monsonego J, et al. (2011) End-of-study safety, immunogenicity, and efficacy of quadrivalent HPV (types 6, 11, 16, 18) recombinant vaccine in adult women 24-45 years of age. Br J Cancer 105: 28-37.
  160. Assad S, Francis A (1999) Over a decade of experience with a yeast recombinant hepatitis B vaccine. Vaccine 18: 57-67.
  161. Venters C, Graham W, Cassidy W (2004) Recombivax-HB: perspectives past, present and future. Expert Rev Vaccines 3: 119-129.
Citation: Garcon N, Descamps D, Leyssen M, Stoffel M, Pasquale AD (2012) Designing Vaccines against Human Papillomavirus and Hepatitis B Virus: Similarities and Differences for Preventable Viral Infections and role of AS04 Adjuvant System in Addressing Specific Challenges. J Vaccines Vaccin 3:130.

Copyright: © 2012 Garcon N, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.