Evaluation of immunogenicity of Campylobacter strains isolated from ovine abortions by laboratory test systems

A microagglutination test and in vitro serum bactericidal assay were used for testing cross-reactions and cross-bactericidal activities of 15 Campylobacter strains isolated from ovine abortions. Antisera against certain strains of C. fetus subsp. fetus and C. jejuni showed higher microagglutination titres and bactericidal activity against homologous and/or heterologous strains. In both tests, cross-reactions and bactericidal activity were higher among the strains of homologous species than among those of heterologous species. The pregnant guinea-pig model was used for testing the efficacy of experimental campylobacter vaccines. Monovalent bacterins prepared with either C. fetus subsp. fetus or C. jejuni did not produce immunity to cross-challenge with the opposite species. Guinea-pigs immunized with the bivalent bacterin were found to be immune to both groups of Campylobacter when subsequently challenged. In vaccinated guinea-pigs, their in vivo ability to overcome infection is reflected in the in vitro bactericidal capacity of homologous rabbit antiserum.