Human immunodeficiency virus type 1 glycoprotein 120 V3 loop (HIV-1 gp120 V3 loop)

The HIV-1 gp120 V3 loop is a critical domain within the surface subunit of the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (Env). It is approximately 35 amino acids long and is often referred to as the principal neutralizing determinant (PND) due to its high immunogenicity (Huang et al., 2005, Science). Biologically, the V3 loop is responsible for determining viral tropism by mediating the interaction between gp120 and host cell coreceptors, specifically CCR5 or CXCR4 (Cormier & Dragic, 2002, Reviews in Medical Virology). This interaction is a prerequisite for the conformational changes in the gp41 subunit that lead to membrane fusion and viral entry. In the context of disease, the V3 loop's sequence diversity is a major driver of HIV-1's ability to evade the host immune system and develop resistance to neutralizing antibodies (Sagar et al., 2006, Journal of Virology). Therapeutic strategies targeting the V3 loop include broadly neutralizing antibodies (bNAbs) like PGT121 and 10-1074, which recognize conserved glycans and protein motifs within the region to block infection (Mouquet et al., 2012, PNAS). Despite its potential as a target, the high rate of mutation within the V3 loop remains a significant challenge for vaccine and drug development (Korber et al., 2001, Science).

Other names

V3 loopThird variable loop of gp120Principal neutralizing determinantPNDgp120 V3 domainV3 crownV3 base

Antibodies targeting the V3 loop epitope bind to the loop's tip or base (often involving associated glycans), sterically hindering the interaction between gp120 and the host coreceptors CCR5 or CXCR4, which prevents viral-cell membrane fusion and subsequent infection (Sok & Burton, 2018, Nature Reviews Immunology).