Abstract: Abstract: To evaluate the diversity of immunogenicity of IROMPs, OMPs and whole-cell bacterin (WCB) of leporid P. multocida. 20 mice were equally assigned to 4 groups at random. They were immunimized by IROMPs, OMPs and WCB respectively. The indirect ELISA was used to detect antibody responses. After two months postvaccinally, the antisera to these three immunogens and normal serum were collected and diluted with sterile physiological saline (1:10 V/V). Then 48 mice were equally assigned to 8 groups at random, group a and b, antisera to IROMPs; group c and d, antisera to OMPs; group e and f, antisera to WCB; group g and h, normal serum. Then group a, c, e and g were challenged with P. multocida C51-17 and group b, d, f and h were challenged with C51-3 to observe the passive protection. The results of active immunity showed that titers of serum antibodies of group WCB were higher than those of group IROMPs and OMPs before 21d, After that, antibody response of group IROMPs climbed up rapidly and soon bypass that of WCB group. At last, the titers were: IROMPs > WCB > OMPs. The results of passive protection indicated IROMPs-antisera could enhanced resistance against P. multocida C51-3 and C51-17, while OMPs-antisera and WCB-antisera couldn’t provide effective protction against C51-3. It demonstrated that IROMPs could enhance resistance against challenge of heterologous serotype of P.multocida, maybe had characteristics of cross-protection factors (CPFs).

Key words: Pasteurella multocida, rabbit, Atigenicity, IROMPs