We determined the subtype of HIV-1 in 89 infected individuals attending three reference hospitals located in the Tokyo metropolitan area of Japan. Subtyping was performed with subtype-specific polymerase chain reaction (PCR) distinguishing subtype A, B, C, and CRF01_AE and/or phylogenetic analysis of HIV-1 env C2V3C3 sequences. Subtype-specific PCR provided unequivocal results in 97% of samples. Sixty-five subjects were infected with subtype B, 16 with CRF01_AE, 4 with subtype A, 1 with CRF02_AG, and 3 with subtype C. Among 31 Japanese individuals infected through heterosexual contact, 13 were infected with subtype B and 12 with CRF01_AE. All of the 41 Japanese men infected through homosexual contact harbored subtype B. These results indicate that subtype B is exclusively predominant in a homosexually transmitted group, whereas subtype B and CRF01_AE are evenly predominant in a heterosexually transmitted group.
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