Purification and partial characterization of a macrophage cytotoxin from Pasteurella haemolytica.

A protein from Pasteurella haemolytica that was highly immunogenic and toxic toward bovine alveolar macrophages was partially purified. When isolated from culture supernatants of P haemolytica serotype 1 or serotype 6, the protein reacted on Ouchterlony immunodiffusion tests with antisera from 12 serotypes of P haemolytica, but did not cross-react with antisera to serotypes of P multocida. This indicated that the protein may be specific for P haemolytica. Bacteria were grown in dialysis culture in a brain-heart infusion and calf-serum growth medium. The protein was isolated from the medium by ultrafiltration and size-exclusion chromatography and has a molecular weight of approximately 150,000 daltons. The protein, which is highly immunogenic and has the characteristics of a virulence factor, is common to all serotypes of P haemolytica, and may be an effective agent for immunization against P haemolytica in cattle.