HIV-1 envelope glycoprotein gp120 third variable region (gp120 V3 region)

The gp120 V3 region is the third variable loop of the HIV-1 envelope glycoprotein gp120 and serves as a principal determinant for viral tropism and coreceptor selection. It mediates HIV binding to host cell chemokine receptors CCR5 or CXCR4, facilitating viral entry following CD4 engagement[1][3][5][7][10]. Structurally, the V3 loop protrudes from the gp120 core and consists of a base, a flexible stem, and a crown containing conserved motifs crucial for coreceptor interaction[7]. It is highly immunodominant and the main target of neutralizing antibodies that can prevent HIV infection; antibodies targeting the V3 loop are elicited in nearly all HIV-infected individuals and are a focus of HIV vaccine design[3][4][7][8]. Due to its genetic diversity and structural flexibility, the V3 loop also plays a role in immune escape and drug resistance. Predictive algorithms using V3 sequence and structure guide patient selection for coreceptor antagonist therapy and are used in disease monitoring[5][10]. Safety concerns relate primarily to its rapid adaptation, facilitating viral escape from immune pressure and pharmacologic blockade[7][9][10].

Other names

V3 loopthird variable region of gp120gp120 V3HIV-1 gp120 V3 loop

Inhibition of coreceptor binding (CCR5/CXCR4 antagonists); Neutralization via antibody binding to exposed V3 epitopes (monoclonal antibodies); Allosteric inhibition of envelope glycoprotein conformational changes