OUTER-MEMBRANE PROTEINS OF BOVINE PASTEURELLA-MULTOCIDA SEROGROUP-A ISOLATES

The outer membrane proteins (OMPs) of P. multocida serotypes A3 (7 iso lates), A4 (2 isolates), A3,4 and A2 (one isolate each) obtained from pneumonic cattle (10 isolates) and from one pig isolate were investiga ted to identify potential immunogens. SDS-PAGE of P. multocida OM isol ated by SDG centrifugation of spheroplasts revealed eight major OMPs. Outer membranes isolated by sarcosyl extraction or SDG had similar pro tein composition on Coomassie blue-stained SDS-PA gel and on immunoblo ts. Two major OMPs (M(r)s of 35 and 46 kDa at 100 degrees C) demonstra ted heat modifiability with apparent M(r)s of 30 and 34 kDa at 37 degr ees C, respectively. The N-terminal aa sequences of these heat modifia ble proteins revealed homology with E. coli OmpA and Hib P1 proteins, respectively. Protease treatment of whole cells followed by western im munoblots using bovine convalescent sera identified several immunogeni c, surface-exposed and conserved OMPs among the eleven P. multocida is olates examined. The whole organism SDS-PAGE profiles of the eleven P. multocida isolates differed such that six patterns were seen. These p atterns could potentially be used as a typing system for P. multocida bovine isolates based on the molecular weights of whole cell proteins. The above observations have potentially important implications relati ve to the immunity to infection.