Effect of Adjuvants on Immunogenicity of MN Recombinant Glycoprotein 120 in Guinea Pigs

The immunogenicity of recombinant gp120 from the MN strain of HIV-1, a candidate HIV-1 vaccine, was evaluated in guinea pigs using adjuvant formulations with different physical and chemical properties. The adjuvants tested included Freund's adjuvant (FA), alum, and the novel adjuvant QS-21. These studies demonstrated that QS-21 provides a number of advantages compared to the two other adjuvants tested. QS-21 formulations accelerated the production of antibodies to MN rgp120 and elicited complete seroconversion after a single immunization. QS-21 shifted the antigen dose-response curve for antibody production by as much as three orders of magnitude, enabling a more economical use of antigen. Antibody titers to MN rgp120 and to the principal neutralizing determinant in the V3 domain were higher in animals receiving QS-21 formulations than in animals immunized with the other adjuvants, and correlated well with higher virus neutralization titers in an in vitro assay. These results support the testing of QS-21 in future clinical trials of candidate HIV-1 vaccines.