A reliable protocol for producing primary monomeric HIV-1 gp120 is presented.
The protocol avoids renowned problems in amplifying and cloning HIV-1 Env sequences.
The conditions for studying the gp120 interactions with CD4 and CCR5 are described.
The binding assay to CD4 is adaptable to large collections of glycoproteins.
The receptor binding assays confirmed that the gp120 are functionally relevant.