Adjuvant Effect of Chicken Interferon-γ for Inactivated Salmonella Enteritidis Antigen

The adjuvant effect of chicken interferon-γ (ChIFN-γ) 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-γ intramuscularly, and all chickens were challenged with SE. Sera collected from immunized groups with or without ChIFN-γ, 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-γ. No antibodies were detected in unimmunized group before challenge. Fecal samples from each group were cultured at 1, 4, 7, and 13 days postchallenge to determine the incidence of intestinal colonization and the numbers of SE shed into the environment. Co-administration of ChIFN-γ, 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-γ administered group. These data suggest co-administration of ChIFN-γ with SE antigen enhances protection against SE challenge without acceleration of antibody production.