HIV-1 envelope glycoprotein V3 loop (also known as principal neutralizing domain) (V3 loop)

The HIV-1 principal neutralizing domain refers to a specific region of the viral envelope glycoprotein gp120, known as the V3 loop, which is a key target for virus-neutralizing antibodies. This domain consists of approximately 24–35 amino acids, with a central, relatively conserved Gly-Pro-Gly motif, flanked by more variable regions. It plays a significant role in determining viral infectivity, tropism (which coreceptor the virus uses), and sensitivity to neutralization by antibodies. Although the V3 loop is immunogenic and a major target of neutralizing antibodies, its high sequence variability and structural masking by glycan shields or surrounding domains contribute to immune evasion and limit the breadth of the natural and elicited antibody response. The V3 loop is a principal focus for vaccine design, but sequence diversity remains a barrier to eliciting broadly protective antibodies.

Other names

Principal neutralizing determinant (PND)Principal neutralizing domain (PND)HIV-1 V3 loopHIV-1 envelope glycoprotein V3 regiongp120 V3 loop

Broadly neutralizing antibodies bind to the V3 loop, block its interaction with host receptors, and neutralize the virus by preventing cell entry. Vaccine candidates aim to induce V3-specific antibodies that neutralize diverse HIV-1 strains.