Cross-reactive immunogenic proteins of P.multocida serotypes: candidates for improving vaccine

Because P.multocida serotypes have no cross protection Several studies have been focused on identification of immunogenic molecules shared between different serotypes in the hope of production of a wide-range vaccine effective against all causative serotypes. In the present study, crude sonicated cell extracts of P. multocida serotypes A:1, A:3, and A:4 were immunoblotted against chicken hyper-immune sera in order to identify cross-reactive immunogenic proteins of them. 35 chickens aged two months randomly divided into 7 groups of five and were injected by monovalent or trivalent serotypes with time intervals of 14 days between first and second injections, and 10 days between second and third and third to fourth injections. The first inoculum was adjuvanted with complete Freund adjuvant (CFA), the second and third inocula were adjuvanted with incomplete Freund adjuvant (IFA), and the fourth one was without any adjuvant. Results showed that there are at least 5 cross-reactive immunogenic proteins in serotypes A:1, A:3, and A:4, in a way that antibodies produced by chicken in an immune response to immunization with whole cell Pasteurella suspensions are able to react with each of the 3 serotypes. These cross-reactive agents are proteins (or at least in some parts) with the molecular weight of 39, 40, 37, 53, and 30 K.Da. The 39 K.Da band was the most prominent immunoblott and introduced as candidate for molecular identification and future vaccine studies.