Closely related HIV-1CRFO1_AE variant among injecting drug users in northern Vietnam: Evidence of HIV spread across the Vietnam-China border

To investigate the nature of recent HIV outbreaks among injecting drug user s (IDUs) near the Vietnam-China border, we genetically analyzed 24 HIV-posi tive blood specimens from 2 northern provinces of Vietnam (Lang Son and qua ng Ninh) adjacent to the China border, where HIV outbreaks among IDUs were first detected in late 1996, Genetic subtyping based on gag (p17) and env ( C2/V3) sequences revealed that CRF01_AE is a principal strain circulating t hroughout Vietnam, including the provinces near the China border, The major ity of CRF01_AE sequences among IDUs in Quang Ninh and Lang Son showed sign ificant clustering with those found in nearby Pingxiang City of China's Gua ngxi Province, sharing a unique valine substitution 12 amino acids downstre am of the V3 loop. This particular subtype E variant, uniquely found among IDUs in northern Vietnam and southeastern China, is designated E-v. The gen etic diversity of CRF01_AE distributed in Quang Ninh (1.5 +/- 0.6%) and Pin gxiang City (1.9 +/- 1.2%) was remarkably low, indicating the emerging natu re of HIV spread in these areas. It is also noted that the genetic diversit y of CRF01_AE among IDUs was consistently lower than that in persons infect ed sexually, suggesting that fewer closely related CRF01_AE variants were i ntroduced into IDUs and, conversely, that multiple strains of CRF01_AE had been introduced via the sexual route. The data in the present study provide additional evidence that HIV outbreaks among IDUs in northern Vietnam were caused by the recent introduction of a highly homogeneous CRF01_AE variant (E-v) closely related to that prevailing in nearby southern China.