| Leporid Pasteurella multocida is worldwide zoonotic pathogens of pasteurellosis leporid , may cause many diseases such as rhinitis, endemic pneumonia, septicemia, otitis media, conjunctivitis, pyometra and testitis, which made substantial economic losses for rabbit industry. The iron-regulated outer membrane proteins (IROMPs) were considered to be related with cross protection factors, and were important protective antigens. In the present study, we investigated the immunity of IROMPs from different aspects in order to develop new vaccine candidates.1 Cross Antigenicity Test of Iron-regulated Outer Membrane Proteins (IROMPs) of Leporid Pasteurella multocidaLeporid Pasteurella multocida strain JS, C51-2, C51-3 and C51-17 were cultured in iron-replete, iron-restricted and normal conditions respectively. The bacterium cells grown under above conditions were measured to characterize iron-regulated outer membrane proteins (IROMPs) by the Congo Red binding test, all tested strains showed greater binding to Congo Red in case of the expression of IROMPs. The SDS-PAGE patterns of OMP extracts of these four strains grown under the iron-rich, iron-restricted or normal conditions, demonstrated that the IROMPs of 147kD,135 kD,99 kD,94 kD,82 kD and 72 kD were expressed when grown in iron-restricted media, other than in iron-replete and normal conditions. Murine serum antibodies against the whole-cell bacterin of strain C51-17 grown in normal condition, couldn't react with the IROMPs. The IROMP extracts from strain C51-17 could elicit the hosts to produce antibodies, and antibodies could react with the IROMPs of the four strains by western blots. The bands of 99 kD, 94 kD or 87.6kD IROMP had the common antigens among the four strains in higher titers by ELISA . It showed that the IROMP extracts from P. multocida grown in iron-restricted condition, maybe had the epitopes of cross-protected factors (CPFs).2 Evaluation of the immunity and protection of iron-regulated outer membrane proteins (IROMPs) of leporid Pasteurella multocidaTo evaluate the diversity of immunogenicity of IROMPs, OMPs and whole-cellbacterin (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 ELIS A 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 C51-17 and group b, d, f and h were challenged with C51-3 to observe the passive protection. The result of active immunity showed that titers of serum antibodies of group WCB were higher than those of group IROMPs and OMPs before 2Id, After that, antibody response of group IROMPs climbed up rapidly and soon bypass that of WCB group. In total, the titers were: IROMPs >OMPs >WCB. The result of passive protection indicated IROMPs-antisera could enhanced resistance against C51-3 and C51-17, while OMPs-antisera and WCB-antisera couldn't provide effective protction against C51-3. All these results demonstrated that IROMPs could enhance resistance against challenge of heterologous serotype of P. multocida, maybe had characteristics of cross-protection factors (CPFs).3 The relationship between the components of outer membrane proteins (OMPs) and drug resistance of Pasteurella multocidaIron was one of essential nutrient factors. Outer membrane proteins(OMPs) played important role in the course of uptake and transfer of iron, and they were related with drug resistance of bacterium. Two leporid Pasteurella multocida strain C51-3 and C51-17 were cultured in normal, iron-replete and iron-restricted condition. These bacteria cells were harvested and sonicated, then dealed with sacosyl to extract outer membrane proteins(OMPs...
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