Variable and conserved neutralization antigens of human immunodeficiency virus.

Human immunodeficiency virus type 1 (HIV-1, HTLV-III/LAV), the retrovirus responsible for acquired immune deficiency syndrome (AIDS), shows a high degree of genetic polymorphism, particularly in the env gene. We have examined sera from rabbits and guinea pigs immunized with gp130, a recombinant env glycoprotein, and sera from HIV-1-infected subjects, to test their capacity to neutralize a panel of genetically divergent HIV-1 isolates. The sera raised against recombinant antigen specifically neutralized the virus strain from which the env gene was cloned (HTLV-IIIB), but not an independent isolate (HTLV-IIIRF). One rabbit serum tested on seven isolates cross-neutralized two at lower titres. In contrast, human sera from Britain and Uganda, chosen for ability to neutralize HTLV-IIIRF, cross-neutralized six other HIV-1 isolates. When serum and isolate were derived from the same subject, the serum was in some cases effective at slightly lower concentrations (higher titres). Human complement did not affect neutralization titres. These findings indicate that genetically diverse HIV-1 isolates carry both variable and widely conserved antigenic epitopes for neutralizing antibodies. The identification of shared epitopes may help the development of protective vaccines.