Discrimination of Vaccinated and infected Pigs by Salmonella-specific IGa antibodies

Abstract

Isotype switching from IgM to IgG or IgA leads to generation of high affinity antibodies during the immune response. This phenomenon can be applied for differentiation of early and late infection stages. The purpose of this study was to evaluate the applicability of a newly developed Ig-isotype specific Salmonella antibody ELISA for discrimination between vaccinated and infected pigs. Using this novel ELISA we were able to detect different patterns of Salmonella-specific IgM, IgG and IgA antibodies following immunization with a S. Typhimurium live vaccine or after experimental infection with a nalidixic-acid resistant wild-type strain of S. Typhimurium. Interestingly, Salmonella-specific IgA antibodies represented an excellent tool for the recognition of fresh infection in vaccinated pigs. Under SPF conditions, we were able to discriminate between naive, vaccinated, experimentally infected nonvaccinated, and experimentally infected vaccinated animals. However, the highest specific IgA levels were detected in challenged vaccinated pigs. Preliminary results from field trials support the findings from experiments using SPF animals