Immunogenicity of capsular antigens of Pasteurella multocida in turkeys.

Capsular antigens were isolated from Pasteurella multocida, strain P-1059 and their immunogenicity was tested in turkeys. The crude capsular antigen (CCA) was extracted from bacterial cells grown on membranes by heating at 56 C in a 2.5% NaCl solution. The purified polysaccharide antigen (PPA) was obtained by precipitation of CCA by cetylpyridinium chloride. Young adult turkeys were inoculated at 0 and 14 days and were challenge exposed at 28 days by IM inoculation of a live culture of P-1059. The turkeys were observed for 2 weeks and mortality was recorded; bacterial isolation was done at the time of necropsy. In 3 trials, CCA provided 80% to 100% protection; in 1 trial, PPA failed to provide protection. Freund's incomplete adjuvant and aluminum hydroxide gel were effective as potentiating agents when higher than 280 microgram of CCA was used. The CCA showed significant (P less than 0.05) protection after treatment with heat (100 C, 5 min), chloroform, or trypsin, but lost its immunogenicity completely by acid hydrolysis. The CCA was not toxic to mice at 2 mg. The limulus lysate test showed that CCA contained endotoxin in less than or equal to 5% of the total solids. These results indicate that the surface antigen isolated from P multocida by saline extraction was immunogenic in young adult turkeys.