Relationship between antigen release and antibody response of infectious coryza water-in-oil-in-water emulsion vaccines

The relationship between the antigen release from formulations in vitro and the antibody response after administration of water-in-oil-in-water (W/O/W) emulsion vaccines containing Haemophilus paragallinarum (Hpg) was studied in chickens. Increases of sorbitan sesquioleate volume in the formulation led to slower antigen release and tended to induce higher hemagglutination-inhibition (HI) antibody titers. In addition, the vaccines prepared with internal aqueous phase:oil phase:external aqueous phase (A:O:A) ratios of 3:4:3 and 3:3:4 also showed slower release of antigen and higher HI antibody titer compared with those of an A:O:A ratio of 3:2:5. Vaccines prepared with polyoxyethylene (POE)(10) hydrogenated castor oil or POE(40) hydrogenated castor oil instead of sorbitan sesquioleate showed higher release and lower antibody HI titers. As a result, HI antibody titers at 6 wk after vaccination were inversely related to antigen release, as determined by the release test. The correlation coefficient was 0.942. In infectious coryza W/O/W emulsion vaccines, the slow release of antigen from the formulation induced and maintained high HI antibody titers of Hpg.