Journal of Vaccines & Vaccination

Use of O-specific polysaccharides for preparation of immunogenic conjugates of Salmonella enterica serovars Typhi and Paratyphi A

16^th Euro Global Summit and Expo on Vaccines & Vaccination

June 19-21, 2017 Paris, France

Abdul Haque and Muhammad Aamir

The University of Faisalabad, Pakistan
National Institute for Biotechnology and Genetic Engineering, Pakistan

Posters & Accepted Abstracts: J Vaccines Vaccin

Abstract:

Typhoid and paratyphoid fevers, caused by Salmonella enterica serovars Typhi (S. Typhi) and Paratyphi A (S. Paratyphi A) are major health problems in developing countries. The available vaccines have certain limitations regarding their efficacy and inability to induce an immune response especially in individuals under 2 years of age. Conjugate vaccines which consist of a bacteria-specific polysaccharide chemically bound to a carrier protein overcome these problems by inducing a T-cell dependent immune response characterized by enhanced immunogenicity in all ages. Traditionally, Vi antigen of S. Typhi has been used for vaccine preparation but realization of importance of Vi negative isolates in recent years has made it imperative to prepare vaccines based on antigens which are present universally in all isolates. So we selected O-specific polysaccharides (OSP) for our experiments. In this study, O-specific polysaccharides (OSP) of S. Typhi were conjugated to diphtheria toxoid (DT) using adipic acid dihydrazide (ADH) as a linker. These conjugates (OSP-AH-DT) were then evaluated for their immunogenicity using mice as a model and showed significantly higher levels of IgG ELISA titers (P=0.0241 and 0.0245) than lipopolysaccharides alone. Different immunization schedules were compared and it was found that schedule-B (three injections with 4-weeks interval) induced higher immune responses than schedule-A (three injections with 2-weeks interval). We showed that diphtheria toxoid can be successfully employed as a carrier protein for conjugation with S. Typhi OSP and the resultant conjugates elicit adequate immune response. We carried out similar successful experiments by preparing conjugates of S. Paratyphi A OSP and diphtheria toxoid.

Biography :

Email: ahaqnibge@gmail.com