Adjuvant effects of various lipopeptides and interferon-γ on the humoral immune response of chickens

The adjuvant effects of various lipopeptides and recombinant chicken interferon gamma (IFN gamma) on the humoral immune response of laying hens was investigated in four immunization studies. We used the lipopeptide Pam(3)Cys-Ser-(Lys)(4) (PCSL), the conjugate P-T-h1 consisting of the lipopeptide P3CS and the T-helper epitope T-h1 (FI-SEAIIHVLHSRHPG), and the conjugate P-T-h2 of the lipopeptide P3CSS and the T-helper epitope T-h2 which corresponds to the peptide EWEFVNTPPLV, as adjuvants. Human serum albumin (HSA), recombinant bovine somatotropin (RBST), and human immunoglobulin G (IgG) served as antigens in the different experiments. All tested adjuvants enhanced the humoral immune response with various intensities. Chickens showed high antibody titers after the immunization with HSA even without adjuvant, but the adjuvant effects of PCSL and the combination of PCSL and recombinant chicken interferon-gamma (IFN-gamma) were much more pronounced using the antigens REST and IgG. Especially after the third immunization, higher titers of antibodies were induced by the coadministration of P-T-h1 and, to a greater extent, by the combination of PCSL and P-T-h1 compared with the use of PCSL. Also, chickens that had received PCSL and P-T-h2 showed the highest immune response, even after the second booster. The average concentrations of chicken immunoglobulin Y were significantly higher in Ei-mo-old chickens (9.4 mg/mL serum and 10.1 mg/mL egg yolk) compared with 9-mo-old chickens (5.9 mg/mL serum and 5.1 mg/mL egg yolk). The specific serum antibody response was higher in the older chickens than in the younger chickens. Because chicken antibodies are likely to be used increasingly for diagnostic and therapy in the future, lipopeptides and recombinant chicken IFN-gamma may find many applications as adjuvants, thus contributing to the welfare of experimental animals.