Impaired antibody response after immunization of HIV-infected individuals with the polysaccharide vaccine against Salmonella typhi (Typhim-Vi®)

Infections with Salmonella species, including Salmonella typhi, are more frequently observed in HIV-infected individuals than in healthy individuals. HIV-infected individuals were vaccinated with polysaccharide vaccine against Salmonella typhi (Typhim-Vi®) which is assumed to be a T-cell-independent antigen. We found that the antibody response in patients with <200×10⁶/l CD4⁺ T lymphocytes was significantly lower compared with patients with ≥200×10⁶/l CD4⁺ T lymphocytes and healthy controls. The antibody response after vaccination with the polysaccharide salmonella Vi-antigen was correlated with the number of CD4⁺ T lymphocytes and therefore Typhim-Vi can be considered to be a T-cell-independent type 2 antigen. The results of this study indicate that after vaccination the proportion of HIV-infected individuals with protective antibody concentrations against Salmonella typhi will be lower than in healthy controls.