Effects of the lipopolysaccharide-protein complex and crude capsular antigens of Pasteurella multocida serotype A on antibody responses and delayed type hypersensitivity responses in the chicken

The effects of the lipopolysaccharide-protein complex (LPS) and crude capsu lar antigen (CCA) prepared from Pasteurella multocida serotype A isolated f rom a duck in the Philippines, on antibody responses to sheep red blood cel ls (SRBC) and Brucella abortus (BA) and delayed type hypersensitivity (DTH) responses to bovine serum albumin (BSA) in the chickens were studied. Chic kens injected subcutaneously with LPS and CCA at 1 and 2 weeks of age and i mmunized intravenously with the mixed antigens of SRBC and BA, at 3 and 4 w eeks of age showed significantly increased antibody responses against both SRBC and BA, when evaluated at 7 days after each immunization. In addition, these chickens sensitized intramuscularly with the emulsion of BSA in comp lete Freund's adjuvant at 5 weeks of age, and then injected into the wattle with BSA at 7 weeks of age also showed significantly increased DTH respons es against BSA, when evaluated at 24 and 48 hr after challenge. These resul ts indicate that LPS and CCA of P, multocida serotype A have a property enh ancing humoral and cell-mediated immune responses.