HIV-1 subtyping using phylogenetic analysis of pol gene sequences.

HIV-1 pol gene sequencing is now used routinely in France to identify mutations associated with resistance to reverse transcriptase (RT) or protease (PR) inhibitors. These sequences may also provide other information, such as the HIV-1 subtype. HIV-1 subtyping was compared using the RT and PR gene sequences to heteroduplex mobility assay (HMA) of the envelope gene. The RT and PR genes of 51 samples that had been subtyped earlier by HMA were sequenced. Sequences were aligned and subtypes were determined by phylogenetic analysis with reference HIV sequences. HMA gave the following subtypes: A (20), B (19), C (1), D (3), F (1), G (3) and CRF01-AE (4). Phylogenetic analysis of the RT gene gave: A (5), B (19), C (2), D (3), F (1), G (6), J (2), CRF01_AE (4), CFR02_AG (7) and undetermined (2). PR gene analysis did not infer subtypes with sufficient confidence. HMA and RT subtyping was not in agreement in nine cases. RT subtyping can identify CFR02_AG and CRF01_AE variants from A subtype RT. It was shown that phylogenetic analysis of the RT gene could provide a useful method for HIV-1 subtyping. The length of the amplicon and the relative performance of each primer pair used in this study favoured RT sequences as a subtyping tool. One potential advantage over env subtyping HMA is the ability to identify some circulating recombinant forms (CRFs).