AIDS Research and Human Retroviruses

Abstract

We have evaluated the genetic diversity of HIV-1 strains infecting injecting drug users (IDUs) in Lisbon, Por-tugal. Heteroduplex mobility assay and/or phylogenetic analysis revealed that env (C2V3C3 or gp41) subtype B is present in 63.7 % of the 135 viral samples studied, followed by subtypes G (23.7%), A (6.7%), F (5.2%), and D (0.7%). Similar analysis of gag (p24/p7) performed on 91 of the specimens demonstrated that 49.5% of the infections were caused by subtype G viruses; other gag subtypes identified were B (39.5%), F (3.3%), A and D (1.1. % each), and the recombinant circulating form CRF02_AG (5.5%). Discordant env/gag sub-types were detected in 34.1 % of the strains and may reflect the presence of dual infections and/or recombi-nant viruses. The presumptive B/G recombinant form was highly predominant (21 of 31). The genetic pat-tern of HIV-1 subtype B and G strains is suggestive of multiple introductions and recombination episodes and of a longstanding presence of both subtypes in the country. C2V3C3 amino acid sequences from IDU-derived subtype G viruses presented highly significant signatures, which distinguish the variants from this transmis-sion group. The unusually high prevalence of subtype G sequences (34.1%), independent of the geographic origin of the infected individuals, makes this IDU HIV-1 epidemic unique. 511 INJECTING DRUG USERS (IDUs) form one of the major riskgroups for HIV-1 infection in Portugal. In the period of 1997–2001, 62 % of the reported AIDS cases were related to this transmission class1 but, following the general trends in most Western European countries, the incidence of HIV-1 infection among Portuguese IDUs has started to decrease. Phylogenetic analyses of HIV-1 isolates distributed world-wide showed, overall, 23 distinct HIV-1 subtypes (A–D, F–H, J, and K) and circulating recombinant forms (CRF01–14) within