Abstract

CABRERA, Osmir et al. Preparation and evaluation of Salmonella typhi Vi polysaccharide-tetanus toxoid conjugates. Vaccimonitor [online]. 2002, vol.11, n.2, pp.6-9. ISSN 1025-028X.

Salmonella typhi Vi polysaccharide is a T-independent antigen that has proven to be protective in young adults. In controlled clinical trials in areas with high rates of typhoid fever, the protective efficacy of the Vi was approximately 70%. However, in high-risk populations, different methods have been used, to synthesize Vi polysaccharide-protein conjugates in order to enhance the antibody response and to confer T-dependent properties to the polysaccharide. In this study a conjugate, Vi polysaccharide -protein, was obtained and its immunogenicity was evaluated in mice. Purified Vi polysaccharide was linked to a carrier protein (tetanus toxoid (TT), via a carbodiimide-mediated reaction. The resultant conjugate was more immunogenic in mice than Vi alone. In contrast to the T-independent properties of Vi, the conjugates of this polysaccharide with TT induced secondary responses and an increase in the duration of IgG anti Vi antibodies, in mice. Serum of animals inoculated with the conjugate showed high IgG anti-TT antibody titers, similar to native TT.

Keywords : Salmonella typhi; polysaccharide Vi; conjugates; immunogenicity.

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