Human immunodeficiency virus type 1 envelope glycoprotein gp120 V1V2 apex (HIV-1 gp120 V1V2 apex) (HIV-1 gp120 V1V2 apex)

The HIV-1 envelope glycoprotein gp120 V1V2 apex is a critical structural domain located at the distal tip of the trimeric envelope (Env) spike, which serves as the sole target for neutralizing antibodies on the virus surface [UniProt P04578]. This apex is formed by the association of the first and second variable loops (V1 and V2) from three gp120 subunits, creating a complex quaternary epitope characterized by both protein residues and conserved N-linked glycans [McLellan et al., Nature 2011]. Biologically, the V1V2 apex is essential for maintaining the Env trimer in its pre-fusion closed conformation, thereby shielding the core of the protein from immune recognition until it encounters the CD4 receptor [Julien et al., Science 2013]. In the progression of HIV-1 infection, the virus utilizes the high mutability of the V1V2 loops to escape host immune pressure, making this region a key determinant of viral fitness and neutralization sensitivity [NIH/NIAID]. Therapeutic strategies focus on this site because it is the target of potent broadly neutralizing antibodies (bNAbs) like PG9 and PGT145, which can neutralize a wide range of global HIV-1 isolates [Sok et al., Science 2014]. These bNAbs typically utilize long, anionic heavy-chain loops to penetrate the glycan shield and bind the underlying conserved protein scaffold, effectively blocking viral entry into host cells [PubMed PMC4289608].

Other names

V1V2 domainV1V2 loopEnv trimer apexQuaternary V1V2 epitopegp120 V1V2 region

Broadly neutralizing antibodies bind to the quaternary V1V2 apex, stabilizing the pre-fusion closed state of the Env trimer and sterically hindering the interaction with the CD4 receptor, thereby preventing viral entry [McLellan et al., Nature 2011; PubMed PMC4289608].