Human immunodeficiency virus type 1 glycoprotein 41 P1 epitope (HIV-1 gp41 P1)

Human immunodeficiency virus type 1 (HIV-1) glycoprotein 41 (gp41) is a transmembrane subunit of the viral envelope protein essential for viral entry into host cells (UniProt P04578). The P1 epitope refers to a specific, highly conserved sequence within gp41 that spans the C-terminal heptad repeat (CHR) and the membrane-proximal external region (MPER) (He et al., 2011, PMID: 21835787). This region is critical for the conformational transition of gp41 into a six-helix bundle, a process that drives the fusion of the viral and host cell membranes (Jiang et al., 2005, PMID: 15709105). Because of its vital role in the viral life cycle, the P1 epitope is a primary target for fusion inhibitor drugs like Enfuvirtide and various broadly neutralizing antibodies such as 2F5, 4E10, and 10E8 (Huang et al., 2012, PMID: 23151586). These therapeutic agents work by binding to the exposed gp41 structure during the fusion process, effectively blocking the entry of the virus into the target T-cell (PubChem CID 16130199). However, the P1 epitope is often shielded by the gp120 subunit and is only transiently exposed, which poses significant challenges for drug delivery and vaccine efficacy (PubMed PMID: 21835787). Monitoring for mutations within this epitope is essential, as changes in the amino acid sequence can lead to high-level resistance against fusion inhibitors (FDA Label for Fuzeon).

Other names

gp41 P1 peptideMPER-CHR epitopeMembrane-proximal external region epitopegp41 fusion inhibitor epitope

The P1 epitope serves as a binding site for broadly neutralizing antibodies that intercept the gp41 pre-hairpin intermediate, preventing the transition to the fusion-active six-helix bundle state (PMID: 23151586). Additionally, peptides derived from this epitope sequence act as competitive inhibitors by binding to the N-terminal heptad repeat (HR1) of gp41, thereby blocking viral-cell membrane fusion (PMID: 15709105).