ANTIGENIC ANALYSIS OF HIV TYPE-1 EXTERNAL ENVELOPE (ENV) GLYCOPROTEINC2 REGION - IMPLICATION FOR THE STRUCTURE OF ENV

To determine whether the amino acid sequence extending from residue 27 3 to residue 288 in the second conserved region C2 of the HIV-1 envelo pe glycoprotein represents a target for antibodies on monomeric and ol igomerized HIV-1 gp120(env), we characterized several antisera and mon oclonal antibodies (MAb) raised against C2 synthetic peptides. A cross -reactive epitope was evidenced on HIV-1Lai and HIV-1Eli C2-derived pe ptides, but was not encountered on HIV-2 C2-derived peptide. This epit ope was found to be expressed on the native monomeric gp120(env) but w as not detected in the context of oligomeric Env, suggesting this regi on is sequestered in the oligomeric molecule. Preincubation of oligome ric Env with sCD4 apparently failed to expose this epitope. Our result s suggest that the amino acid sequence extending from residue 273 to r esidue 288 in C2 of HIV-1 gp120(env) may be involved in intermolecular interaction within the oligomeric Env complex.