An AB recombinant and its parental HIV type 1 strains in the area of the former Soviet Union: low requirements for sequence identity in recombination

In the former Soviet Union (SU) increasing numbers of HIV-1 infections amon g injecting drug users (IDU) have been reported, especially in the Ukraine. The main subtype transmitted among the IDUs seems to be subtype A, but lim ited numbers of subtype B cases have also been reported. In Kaliningrad, Ru ssia, an AB recombinant strain was earlier shown to be responsible for the local outbreak. Here we describe the genetic relationship of HIV-1 strains circulating among IDUs in the former SU. For subtype A and the AB recombina nt strains nearly full-length genomes were sequenced, and for one subtype B strain the entire envelope gene was cloned. The relationship between the A B recombinant strain and the subtype A and subtype B strains and the mosaic structure of the recombinant was studied by phylogenetic analysis. Ukraini an A and B strains were shown to be the probable parental viruses of the Ka liningrad AB recombinant strain. In the envelope gene the recombination bre akpoint could also be precisely mapped to a region of similarity of only 14 base pairs. This suggests that only short stretches of absolute sequence i dentity may be needed for efficient RNA recombination between HIV-1 subtype s.