ROLE OF OUTER-MEMBRANE PROTEIN H(OMPH)-SPECIFIC AND OMPA-SPECIFIC MONOCLONAL-ANTIBODIES FROM HYBRIDOMA TUMORS IN PROTECTION OF MICE AGAINSTPASTEURELLA-MULTOCIDA

Two major outer membrane proteins of Pasteurella multocida, designated OmpH and OmpA, were characterized and shown to be related to the fami lies of porin and heat-modifiable proteins, respectively. The backpack hybridoma tumor system in BALB/c mice was used to continuously delive r immunoglobulin G2b (IgG2b) monoclonal antibodies (MAbs) specific for OmpH (MAb MT1) and OmpA (MAb MT4.1). MAbs were detected in serum and peritoneal lavage samples of mice bearing hybridoma tumors by an enzym e-linked immunosorbent assay and an immunoblot assay. Highly significa nt protection was observed in mice bearing MT1 hybridoma tumors agains t both intraperitoneal and intranasal challenge infections with homolo gous nontoxigenic P. multocida strains possessing MAb MT1-reacting epi topes, whereas the mice bearing MT4.1 hybridoma tumors were not protec ted. The numbers of P. multocida organisms in the lungs of mice bearin g MT1 hybridoma tumors were significantly less than those in lungs of mice bearing MT4.1 hybridoma tumors at 48 h postchallenge. These resul ts indicate that the OmpH-specific MAb inhibited proliferation of P. m ultocida in the lungs. MAb MT1 was unable to kill P. multocida in vitr o in the presence of complement. However, an enhanced phagocytosis by polymorphonuclear cells (PMNs) was observed in mice bearing MT1 hybrid oma tumors. P. multocida induced a more extensive and rapid influx of PMNs into the peritoneal cavity of mice bearing MT1 hybridoma tumors t han of mice bearing MT4.1 hybridoma tumors. The results of this study demonstrate for the first time that IgG MAbs against OmpH of P. multoc ida are involved in the protection of mice against lethal challenge in fection by means of opsonization and inhibition of proliferation of P. multocida as a result of increased influx of PMNs into the infection site.