Identification of new circulating recombinant form of HIV-1 CRF139_02B in Japan, and search for the origin.

Many circulating recombinant forms (CRFs) of HIV-1 have been reported, resulting in complex molecular epidemiology of HIV-1 infection. In this study, we newly identified CRF139_02B in Japan from 4 cases of anti-retroviral therapy naïve people living with HIV. Near full-length genome sequences of CRF139_02B were determined using Illumina MiSeq. Basic Local Alignment Search Tool (BLAST) revealed that there were several sequences having the same breakpoints as CRF139_02B in the UK and Nepal, though its full-length genome sequences were not available. Maximum clade credibility tree analysis using the region of protease and reverse transcriptase of HIV- 1 estimated that the time to the most recent common ancestor of CRF139_02B variants found in Japan was 2017.6 (95% highest posterior density interval: 2015.9-2019.3), and that among the UK, Nepal, and Japan was 2010.4 (2007.8- 2012.5). These results suggested that CRF139_02B circulated in Japan recently and domestically. Furthermore, the origin of CRF139_02B could be in the UK. Because there is a possibility that further international circulation of CRF139_02B may be observed in the near future, continuous monitoring of HIV-1 molecular epidemiology will be needed.