V5 region in the HIV-1 envelope glycoprotein determines viral sensitivity to the broadly neutralizing monoclonal antibody VRC01.

Our results showed that interchanging the V5 region between the two clones completely swapped their neutralization sensitivity profiles, while exchanging the loop D region alone had minimal impact. Mutagenesis analysis revealed that the potential N-linked glycosylation site (PNGS) at position 460 in the V5 region contributed to over 90% of observed resistance, while other amino acid changes made no discernible differences. Furthermore, changes in resistance were found to positively correlate with VRC01 binding activity to the corresponding envelope glycoprotein. None of the substitutions, however, significantly altered binding and neutralization sensitivity to bnmAb b12 or soluble CD4. Of note, a mutation that removed the PNGS at position 463 in the V5 region increased resistance to ibalizumab, a non-immunosuppressive monoclonal antibody that binds CD4 and has been shown to inhibit entry of diverse HIV-1 isolates. Conclusion In summary, our data indicates that amino acid residues in the V5 region play a critical role in determining viral sensitivity to VRC01. Increased length, glycosylation and long side-chain of amino acids in the V5 region may collectively create steric hindrance that lowers binding affinity, thereby increasing resistance to VRC01 neutralization.