Comparison of Freund's and Ribi adjuvants for inducing antibodies to the synthetic antigen (TG)-AL in rabbits

Abstract

Antibody responses and health parameters were compared in rabbits immunized with a synthetic polypeptide antigen, [ l- Tyr, l- Glu, DL- Ala]- poly- L- lysine , in Freund's (FA) or RIbi (RA) adjuvants, Rabbits, 12 weeks old, of both sexes, were inoculated with 0.5 ml divided between two intramuscular (i.m.) sites. Eight received FA and antigen (50 μg); eight RA and antigen, eight PBS and antigen; four FA and PBS; four RA and PBS, and four PBS. Identical booster inoculations were made 21 days later, except that incomplete FA was substituted for complete FA. Rabbits were monitored until euthanasia and necropsy 7 weeks after the primary inoculation. Sera, obtained weekly, were analyzed for immunoglobulins using an enzyme immunoassay. Only rabbits given antigen with adjuvant produced high titered antibodies. Mean optical density values for immunoblobulin (Ig)M were greater the week after the booster in the group given FA. IgG values were similar for both adjuvant/antigen groups the week after the booster, but thereafter decreased in rabbits given RA. Antisera from rabbits given antigen with FA had greater avidity for the antigen than that from rabbits given antigen with RA, however, the difference was not significant ( p>0.05). Rabbits inoculated with FA and antigen had high serum creatinine kinase levels the day after inoculation, showed evidence of discomfort, and extensive granulomatous inflammation at the inoculation sites. Lesions were minimal to mild in rabbits given antigen with RA and PBS with either adjuvant. While RA did not result in adverse side effects, the IgG response to (TG)-AL with RA was transient compared to FA.