ANTIBODY REACTIVITY TO SYNTHETIC PEPTIDES REPRESENTING THE PRINCIPAL NEUTRALIZING DETERMINANT OF HIV-1 IN MOUSE STRAINS FOLLOWING REPEATED IMMUNIZATION WITH RECOMBINANT GP 160

The third variable region (V3) of the HIV-1 gp120 envelope molecule ap pears to represent a target for naturally occurring neutralizing antib odies in HIV-1-infected individuals. In this report, we examined the e xtent of antibody cross-reactivity to a panel of V3-based synthetic pe ptides in six inbred strains of mice following repeated immunization w ith a baculovirus-derived recombinant gp160 (rgp160) preparation formu lated with alum. The amino acid sequence of the rgp160 used in these i mmunizations was based upon the HIV-1 IIIB (LAI) isolate. Following fi ve injections with rgp160, all six strains developed antibodies to the homologous IIIB-based V3 peptides, designated 304-321 and RP135. Howe ver, antibody cross-reactivity to the other nonhomologous V3 peptides was either undetectable or limited among the strains of mice examined. No in vitro neutralizing activity against HIV-1 was observed in sera from any of the six inbred strains of mice that were examined. These r esults suggest that repeated immunization of mouse strains with a rgp1 60/alum formulation leads to nonneutralizing antibodies directed again st the V3 region which remain predominantly type specific.