HIV-1 genetic diversity in Galicia Spain: BG intersubtype recombinant viruses circulating among injecting drug users.

Background: The HIV-1 epidemics in Western Europe are dominated by B subtype viruses. Non-B subtype is largely restricted to individuals infected outside of Europe and to their direct contacts and is generally acquired by the heterosexual route.

Methods: Protease and a segment of reverse transcriptase were amplified and sequenced from plasma RNA in 451 individuals from seven cities of Galicia, north-western Spain. Subtype sequence homologies were determined using the BLAST algorithm. Non-B sequences were examined by phylogenetic analysis and intersubtype recombination by bootscanning. The env V3 region was analysed in all non-B and in 38 B subtype viruses.

Results: Ten different non-B genetic forms were identified in 20 (4.4%) individuals. Subtypes were concordant between pol and V3 in five viruses; 14 (70%) infections were with intersubtype recombinant viruses, and one individual had a dual B+G infection. Seven recombinant viruses were phylogenetically related to five reported recombinant forms. Three non-recombinant G and six recombinant BG viruses formed a monophyletic cluster for pol. All but three individuals with non-B infections were native Spanish. Only 6 of 16 individuals referred to sexual contacts with sub-Saharan Africans. Twelve (60%) non-B subtype infections, including all with G and BG viruses, were in injecting drug users (IDU).

Conclusions: Non-B subtype viruses were identified in 4.4%, with a high diversity of genetic forms, including 70% infections with intersubtype recombinant viruses. The majority of individuals with non-B infections were IDU, most of them without known contacts with non-European sources, and among whom BG recombinant viruses are circulating.