Variability of human immunodeficiency viruses type 1.

The variability of human immunodeficiency virus type 1 (HIV-1) is very high . To date, three distinct lineages of HIVs, type 1 group M, type I group O and type 2 are described, suggesting at least three different zoonotic infe ctions. HIV-1 group M is responsible for the global epidemic of AIDS. At le ast ten subtypes of HIV-1 group M, labelled A through J, have been discover ed. Viral sequences from both the gag and the env gene, particularly a part of gp120 referred to as the V3 region have been used to identify subtypes of HIV-1 group M. The nucleotide distance between viruses of different subt ypes is on average 30% for the env gene. The various subtypes are geographi cally distributed throughout the world. Some of the subtypes were identifie d as recombinant or mosaic viruses. The existence of different subtypes of HIV-1 have major implication for vac cination. They may also influence the diagnosis of HIV infection. To date i t is unclear whether subtypes of HIV-1 differ with respect to transmissibil ity or pathogenicity.