Assessment of immunization regimens of duckRiemerella anatipestifervaccines

Aims Riemerella anatipestiferinfections of goslings and ducklings can result in high mortality. Since there are at least 21 serotypes ofR. anatipestifer, cross-protection is an important goal for vaccine development. Methods and Results In this study, we evaluated the immunostimulatory effect of different immunization regimens - the traditional inactivated vaccinevsprime-boost regimens using DNA and protein subunit vaccines (DNA+subunit, subunit+subunit, subunit+inactivated and DNA+DNA). Results showed that, when compared to the inactivated vaccine, prime-boost regimens induced higher and up to 16-week longer lasting levels of antibody responses, significantly elevated the percentage of the cytotoxic CD8(+)T cell and higher expression levels of IFN-gamma, IL-6 and IL-12 mRNAs. Furthermore, as an indication of cross-protection, sera from prime-boost regimens were able to recognize lysates ofR. anatipestiferserotypes 1, 2 and 6. Conclusions Prime-boost regimens especially DNA-prime and protein-boost, induce strong long-term immune response and may prove protective for breeder ducks requiring long-term protection. Significance and Impact of the Study It is worth mentioning that the subunit+inactivated regimen group also elicited strong immune response. The cost of this regimen may only be half of the other prime-boost regimens, making this subunit + inactivated combination an attractive option.