Second Conserved Domain of gp120 Is Important for HIV Infectivity and Antibody Neutralization

Rabbit antisera were raised against three overlapping synthetic peptides with sequence homology to the second conserved domain of the external envelope glycoprotein (gp120) of the human immunodeficiency virus (HIV). All of the antisera immunoprecipitated the envelope glycoprotein. In particular, an antiserum directed against amino acids 254 to 274 of env was efficient in neutralizing three different isolates of HIV in vitro, without affecting the binding of the virus to CD4-positive cells. Therefore, this conserved region of gp120 appears to be critical in a postbinding event during virus penetration and may represent a target for antibody neutralization of HIV. These findings may be applicable in the design of a vaccine for the acquired immunodeficiency syndrome.