Cross-protection of Salmonella abortusovis, S. choleraesuis, S. dublin and S. gallinarum in mice induced by S. abortusovis and S. gallinarum: bacteriology and humoral immune response.

Cross-protection induced by primary infection with Abortusovis and Gallinarum was examined against challenge injection with these Salmonella serotypes as well as with Dublin and Choleraesuis, the other virulent serotypes. Abortusovis induced efficient protection against the other Salmonella. Gallinarum was ineffective against Choleraesuis. Even with low multiplication in mice, the Gallinarum J91 strain induced a weak but significant protection against Dublin (same O group serotype). The antibodies in the blood of mice were tested with ELISA specific for the Salmonella antigens used to prime or to challenge animals. The Gallinarum J91 strain was detected to be more antigenic in ELISA than the other Salmonella antigens. It is difficult to conclude on a correlation between IgM or IgG antibodies and induction of protection, because of the variability in immune response according to the different serotype used. Nevertheless, the negative linkage between a number of bacteria in the spleen of mice challenged with Gallinarum and Dublin, and the level of IgM and IgG antibodies specific for the challenging serotype, showed that humoral immune response could be one element of cross-protection, mainly by the immune response against the same O serotype.