HIV gp120

HIV gp120 Full Name

Human Immunodeficiency Virus glycoprotein 20

HIV gp120 Introduction

HIV-1 gp120 is the exterior envelope glycoprotein responsible for the initial attachment of the virus to host cells. Produced as part of the gp160 precursor, gp120 is cleaved from gp41 to form the functional trimeric Env complex, which mediates binding to the primary receptor CD4 and subsequent engagement of a coreceptor, typically CCR5 or CXCR4. CD4 binding induces conformational changes in gp120 that expose or reposition the V3 loop and other regions necessary for coreceptor recognition, initiating fusion between viral and host membranes. These interactions determine viral tropism, with R5-tropic variants predominating in early infection and X4 or dual-tropic variants emerging later, influencing disease progression. gp120's structure, comprising an inner and outer domain with surface-exposed variable loops, allows precise receptor engagement while maintaining conserved elements critical for Env integrity and gp120–gp41 association.

The gp120 glycoprotein is heavily N-glycosylated and contains multiple variable regions (V1–V5), which contribute to antigenic diversity and immune evasion. The glycan shield masks conserved surfaces and limits access of antibodies to vulnerable epitopes, complicating neutralization. Nonetheless, certain conserved domains, including the CD4 binding site, V1/V2 apex, gp120-gp41 interface, and C5 domain, remain targets for broadly neutralizing antibodies. Structural studies demonstrate that CD4 binding triggers large-scale rearrangements in gp120, revealing coreceptor-binding sites while maintaining other regions in protected conformations. Neutralization resistance often arises from alterations in the V2 and V3 loops or modifications in glycan composition, which affect both antibody accessibility and receptor engagement. The V3 loop, in particular, governs coreceptor specificity and trimer stability, highlighting its central role in viral entry and susceptibility to humoral immune responses.

gp120's conformational dynamics and glycan-mediated shielding present challenges for vaccine and therapeutic design. Broadly neutralizing antibodies often target conserved epitopes that are transiently exposed during CD4-induced conformational changes, emphasizing the importance of mimicking native Env trimer states in immunogens. Stabilized trimer designs, such as SOSIP or other engineered mimetics, are used to present these conformational epitopes effectively and guide B-cell maturation toward bnAb lineages. Additionally, small molecules and lectins that block gp120–CD4 or gp120–coreceptor interactions can inhibit viral entry, providing therapeutic avenues that exploit structural features of gp120. Diversity across HIV-1 subtypes, variable loops, and glycan patterns necessitates strategies that focus on conserved functional elements to elicit broadly effective neutralizing responses. Ongoing research continues to explore how conformational exposure, coreceptor dependence, and glycosylation patterns shape vaccine efficacy, antibody breadth, and therapeutic potential, reinforcing gp120 as a central target in HIV prevention and treatment.

Alternate Names for HIV gp120

HIV-1 gp120; HIV1 gp120; Envelope surface glycoprotein gp120; Glycoprotein 120; gp120; gp120 glycoprotein; Human Immunodeficiency Virus 1; SU; Surface protein; Retroviridae; Lentivirus; human immunodeficiency virus

• 1. Bowder D., et al. Contribution of the gp120 V3 loop to envelope glycoprotein trimer stability in primate immunodeficiency viruses. Virology. 2018;521:158-168.
  2. Sagar M., et al. Transmembrane Domain Membrane Proximal External Region but Not Surface Unit–Directed Broadly Neutralizing HIV-1 Antibodies Can Restrict Dendritic Cell–Mediated HIV-1 Trans-infection. The Journal of Infectious Diseases. 2012;205(8):1248-1257.