Adjuvant effect of chicken interferon-gamma for inactivated Salmonella Enteritidis antigen

The adjuvant effect of chicken interferon-gamma (ChIFN-gamma) was examined for protecting chickens against intestinal colonization of Salmonella Enteritidis (SE) following oral exposure. Ten 7-week-old chickens per group were immunized with inactivated SE twice with or without co-administration of ChIFN-gamma intramuscularly, and all chickens were challenged with SE. Sera collected from immunized groups with or without ChIFN-gamma, and from unimmunized group were measured for SE antibody by agglutination test. The levels of antibodies were raised by 1 week post-immunization and did not show any difference between groups with and without ChIFN-gamma. No antibodies were detected in unimmunized group before challenge. Fecal samples from each group were cultured at 1, 4, 7, and 13 days post-challenge to determine the incidence of intestinal colonization and the numbers of SE shed into the environment. Co-administration of ChIFN-gamma, significantly reduced the incidence of intestinal colonization (P<0.05). At 13 days post-challenge, the bacterial counts of SE in organs were also reduced in ChIFN-gamma administered group. These data suggest co-administration of ChIFN-gamma with SE antigen enhances protection against SE challenge without acceleration of antibody production.