Evaluation of Immune Response for Vi-CRM₁₉₇Conjugated Vaccine againstSalmonella entericaserovar Typhi in Mice

Abstract

Typhoid fever, a serious systemic infection caused by Salmonella enterica serovar Typhi, breaks out in developing countries. However, existing vaccines only induce relatively low protective effects with humoral responses and do not stimulate secondary immune response, especially to young people. The objective of this study is to evaluate the immunogenicity of the vaccine containing virulence capsular polysaccharide (Vi) conjugated with the optimal ratios of non-toxic variant of diphtheria toxin (CRM 197 ) in mice. Six-week-old BALB/c female mice were injected intraperitoneally three times at intervals of 14 days and sera were collected on days 0, 14, 28, 42 and 56 post-injection. The efficacy of the vaccine was evaluated by comparing between negative control group injected with PBS and vaccine groups injected with Vi or Vi-CRM 197 conjugate of different ratio. Vi and CRM 197 -specific antibody responses were evaluated using enzyme-linked immunosorbent assay. The result showed that Vi-CRM 197 -1 group revealed the highest and significant Vi-specific IgG immune responses among the other groups and Vi group (p < 0.01). In conclusion, Vi-CRM 197 -1 conjugate vaccine induced the highest humoral immune response in mice and may be used as an effective vaccine to replace the existing typhoid vaccine for infants under 2 years old.

Application of radiation technology in vaccines development

“…Salmonella enterica causes a variety of infectious diseases in animals and humans [ 112 113 ]. Live attenuated vaccines generally confer better protection than killed vaccines; however, they are limited by their toxicity and cause mild diarrhea.…”