V3 loop of HIV subtype B is associated with HIV infectivity and tropism

Abstract

Objective Our goal in this study was to analyze position 11, 22 and 25 of the V3 loop associated with co-receptor usage and disease progression through comparing the amino acid sequences and infectivity of the V3 loop of HIV-1 subtype B infection. Method HIV-1 subtype B V3 amino acid sequence were collected from the HIV seqquence database and divided into CCR5-tropic and CXCR4-tropic.The amino acid sequences of different tropism were multiple-aligned with CLUSTAL W program, and the frequencies of the amino acids sequences of two groups were calculated and sorted in descending order.We constructed pseudoviruses by changing the amino acids at position 22 of the V3 region in CCR5-tropic and CXCR4-tropic viruses and tested their infectivty. Result The amino acids at positions 11, 22, and 25 of V3 were different between the CCR5-tropic virus and CXCR4-tropic virus.The consensus amino acid frequencies were found to be 71.9% S, 66.7% A, and 56.0 % D for the CCR5-tropic virus and 50.0 % R, 57.1 % T, and 26.2 % Q for the CXCR4-tropic virus at positions 11, 22, and 25, respectively.There was a strong association between the identity of the residues at position 11, 22, and 25 of the V3 loop amino acid sequence and CD4+ T cell counts of different patients.All mutations at position 11, 22, 25 of the V3 region reduced its infectivity.When the position 11 of V3 loop of SF162 amino acid residues was converted to R, the virus tropism was changed from R5 to R5X4. Conclusion Our study indicates that position 22 of the V3 loop amino acid sequence is significantly associated with viral tropism and disease progression in HIV-1 subtype B. Key words: HIV-1; V3; Tropism; Disease progression; Infection assay