Salmonella vaccines may fail to elicit antibody responses in immune individuals.

2003 MAR 12 - (NewsRx.com & NewsRx.net) -- by Maria G. Essig, MS, ELS, senior medical writer - Vaccines based on Salmonella vectors are likely to be ineffective in patients with preexisting Salmonella immunity, according to a study published in the journal Infection and Immunity.

"There are conflicting reports concerning the impact of prior vector priming on the immunogenicity of recombinant-Salmonella-based vaccines," reported Christofer J. Vindurampulle and Stephen R. Attridge at the University of Adelaide in Australia. "A comparison of experimental protocols identified two variables which might account for this inconsistency: the potential of the vector strain to colonize the murine gut-associated lymphoid tissue (GALT) and the nature of the foreign antigen subsequently delivered by the recombinant Salmonella construct."

Vindurampulle and Attridge engineered an aroA mutant of the Salmonella enterica serovar Stanley and found that it did not affect GALT colonization significantly. However, the response of anti-lipopolysaccharide (anti-LPS) antibodies was reduced, as was the effect of vector priming.

"Studies were also performed to ascertain the extent to which any observed hyporesponsiveness consequent upon vector priming might be determined by the characteristics of the foreign antigen," the investigators said (Impact of vector priming on the immunogenicity of recombinant Salmonella vaccines. Infect Immun, 2003;71(1):287-297).

When used to deliver the Escherichia coli antigens, K88 pilus protein or LT-B toxin subunit, to mice that had been previously vector-primed, S. enterica serovar Stanley did not stimulate any anti-K88 serum IgG or intestinal IgA antibody responses. In addition, antibody responses against LT-B were ...