Cross-protection against Salmonella enteritidis infection in mice.

Mice were immunized subcutaneously with live vaccines and live vaccines with complete adjuvant incorporating Salmonella enteritidis Se 795, Salmonella typhi-murium M206, Salmonella gallinarum 9R or Salmonella pullorum Sp223. They were challenged along with unvaccinated controls with 100 LD50 of virulent S. enteritidis 5694 SMR subcutaneously on the 21st day post-vaccination. The humoral immune response was studied by assessing the sequential level of agglutinins, complete and incomplete somatic antibodies, opsonophagocytic antibodies, cytophilic antibodies and bactericidal antibodies before and after challenge. The level of these antibodies and the protection afforded by the particular vaccine is correlated and the possible involvement of a humoral mechanism is discussed.