Analysis of the ability of five adjuvants to enhance immune responses to a chimeric plant virus displaying an HIV-1 peptide

The ability of five different adjuvants (alum, complete Freund's adjuvant, Quil A, AdjuPrime and Ribi) to stimulate humoral and T-cell mediated immune responses against a purified chimeric virus particle was investigated. Each adjuvant was administered subcutaneously to adult mice together with 10 mu g of wildtype (wt) cowpea mosaic virus (CPMV) or a chimeric CPMV displaying the HIV-1 gp41 peptide, residues 731-752. All preparations elicited strong antibody responses to CPMV, but Quil A elicited the highest and most consistent responses to the HIV-I peptide. This finding was reflected in both ELISA titres with immobilized peptide and in HIV-l-neutralizing antibody. In addition Quil A was also the only adjuvant to stimulate an in vitro proliferative T-cell response. Surprisingly with all adjuvant formulations a predominately IgG2a anti-gp41 peptide response was observed, indicating a type 1 T-helper cell-like response. Furthermore, the efficiency of the CPMV display system was demonstrated by its ability to induce good levels of peptide specific antibody in the absence of any adjuvant. (C) 1999 Elsevier Science Ltd. All rights reserved.