Recombinant strains of HIV type 1 in the United Kingdom.

Twenty-five recombinant (mosaic) HIV-1 genomes were detected among 151 samples comprising 118 non-B subtype sequences and 33 samples containing subtype B sequences. Seven of the 25 mosaic patterns were similar to characterized circulating recombinant forms (two A/E, four A/G, and one D/F) and one was a MAL-like A/D recombinant. Eighteen of the recombinants had evidence of subtype A sequences in at least one region of their genome. One sample was found to contain a novel recombinant form (pol F, env K). Two samples could not be characterized unambiguously as recombinant forms and a further one appeared to be a complex C/J/D/A genomic form. The majority of the mosaic genomes were recombinants between gag, pol, or env, whereas the C/J/D/A mosaic had cross-over breakpoints within pol. These findings suggest that almost 20% of non-B subtype isolates of HIV-1 circulating in the United Kingdom have mosaic genomes. This shows the diverse origin of HIV-1 strains circulating in the United Kingdom and may have implications for antiretroviral drug resistance.