Comparisons Between The Immunogenicities Of Seven Inactivated Riemerella Anatipestifer Tetravalent Vaccines With Different Adjuvants

Seven inactivated tetravalent vaccines of Riemerella anatipestifer (RA),of which three (1#,3#,7#) employed oil-emulsion,two(4#,6#) employed propolis,two(8#,10#) employed aluminum hydroxide as their basic adjuvants,were developed and compared by the methods as follows:challenges were performed by homologous virulent RA strains to measure their protective abilities;indirect enzyme-linked immunosorbent assay (ELISA) was used to monitor antibody production;lymphocyte transformation test (LTT) was performed to study the expression of cell-mediated immunity. The result indicated that effective levels of duckling protection,with different speeds and durations,could all be secured by administering one dose of these vaccines. Propolis vaccines could confer ducklings partial resistance to challenge as early as 3 days after immunization and absolute immunity still exist 93 days postvaccination. Oil-emulsion vaccines could confer ducklings partial resistance to challenge as early as 10 days after immunization and absolute immunity also exist 93 days postvaccination. Aluminum hydroxide vaccines could confer ducklings partial resistance to challenge as early as 10 days after vaccination but the duration of absolute immunity is only 2-5 weeks. ELISA showed that antibody responses induced by propolis vaccine were faster than that of oil-emulsion vaccines and aluminum hydroxide vaccines;antibody responses induced by oil-emulsion vaccines were longer in duration than that of propolis vaccines and aluminum hydroxide vaccines;the maximum antibody responses induced by oil-emulsion vaccines and propolis vaccines were higher than that of aluminum hydroxide vaccines;Antibody levels were all significantly boosted by revaccination of these vaccines and in addition to this,oil-emulsion vaccines showed longer antibody duration. Lymphocyte transformation test demonstrated that all these vaccines stimulated significantly higher levels of T cell-mediated immunity with a duration of 2 weeks or so than that of control after initial immunization and the levels and durations could both be boosted by revaccination. A phenomenon that the innate T cell-mediated immunity system of ducklings continued to develop as ducklings grew were also observed during the period of this test. Comprehensive comparison and analysis indicate that,of these seven vaccines,3#,6#,10# are better than other(s) in the same group;propolis vaccines are more excellent than oil-emulsion vaccines and aluminum hydroxide vaccines in immunogenicity.