Transmitted drug resistance and phylogenetic analysis of HIV CRF01_AE in Northern Vietnam.

The HIV epidemic in Vietnam began in injecting drug users (IDUs), but increasingly affects the general population. It is therefore important to monitor the spread of infection and, since antiretroviral therapy (ART) is now used more frequently, the prevalence of transmitted drug resistance. Sixty-three 1000 bp pol-gene sequences were generated from treatment-naive HIV-1 CRF01_AE infected patients from four clinics in Northern Vietnam. Four drug resistance mutations; Y181C, L210W, L74I and V75M, were found in four different patients, giving a prevalence of 6.3% (4/63). Earlier studies have shown a lower prevalence and the transmission rate should be regularly monitored prospectively in Vietnam. Additional CRF01_AE (N=190) and outgroup subtype B sequences (N=4) were retrieved from databases and included for phylogenetic analysis and calculations of the time of the most recent common ancestor (tMRCA). The 63 samples from our study clustered into two distinct groups; one small clade (N=3) that had a tMRCA in year 1997.5 and a larger group with an estimated tMRCA in 1989.8. The Vietnamese samples in the large group were distinct from CRF01_AE sequences from Thailand, but closely related to previously sequenced isolates from Vietnam, southern China and the Czech Republic, while the samples in the smaller clade appeared to represent a more recent introduction from Southern Vietnam. Our results showed that sequences from IDUs were intermingled with sequences from sexually infected patients, indicating frequent exchange of virus between the transmission risk groups in Northern Vietnam.