HIV-1 Subtypes and Recombinants

Abstract

ConclusionHIV-1 undergoes rapid genetic diversification due to high mutation rates as well as frequent genomic recombination. Some regions of the genome such as the envelope gene show particularly high rates of evolution due to selection pressure exerted by the host. While only one or a few point mutations are enough to show major phenotypic changes for properties such as drug resistance or immune evasion, HIV-1s are phylogenetically classified into subtypes on the basis of 20%–35% differences in their amino acid sequences.The main group of HIV-1 has 9 subtypes, all of which have been found in Africa. However, only three (A, C, and D) have spread to cause large numbers of infections at the present time. A growing number of CRFs—at least 6—have been described in Africa. Only CRF02_AG, which is the dominant virus in West Africa, has already accounted for a large number of infections. However, CRF01_AE, which is present in the Central African Republic, is also the dominant virus in the heterosexual epidemic of Thailand. HIV-1 subtypes can be most reliably classified using nucleotide sequencing or HMA. To be sure that a given virus is not a recombinant, it is necessary to check the sequences of multiple regions of the viral genome.