3rd Conf Retro and Opportun Infect. 1996 Jan 28-Feb 1;:166. Unique
Globally circulating strains of HIV-1 and HIV-2 are known to exhibit
considerable genetic diversity and this variability is believed to pose
a formidable challenge to AIDS vaccine development efforts. Phylogenetic
analysis of viral sequences have shown that HIV-1 can be classified into
two groups (M and O). group M comprises the great majority of HIV-1
isolates and can be further subdivided into at least nine sequence
subtypes (A-I). Similarly, HIV-2 can be classified into five sequence
subtypes (A-E), although these are based on the analysis of considerably
fewer viruses. Importantly, the majority of HIV-1 and HIV-2 isolates
cluster consistently in phlyogenetic trees derived from different
regions of the genome. Nevertheless, recent studies have noted several
viruses which occupy different positions in phylogenetic trees,
depending on which genes or part of their genome is used for analysis.
Further examination of these cases revealed mosaic HIV-1 and HIV-2
pro-viruses. Moreover, a recent survey of near full-length gag and env
sequences from the database suggested that approximately 10% of HIV-1
viruses originated from probable recombinants. These results indicate
that co-infection with highly divergent viral strains can occur in HIV-1
infected humans and that intersubtype recombination can be expected to
increase in geographic regions where multiple sequence subtypes
co-circulate. In addition, these results have immediate consequences for
our understanding of HIV-1 pathogenesis, vaccine development, and the
methods that should be employed to monitor the molecular epidemiology of
HIV-1 worldwide.
AIDS Vaccines HIV-1/CLASSIFICATION/*GENETICS
HIV-2/CLASSIFICATION/*GENETICS Mosaicism Phylogeny Recombination,
Genetic Variation (Genetics) ABSTRACT