[Genetic characteristics of HIV-1 CRF01_AE strains in four provinces, southern China].

Objective: To analyze the genetic characteristics of HIV-1 CRF01_AE strains prevailing in the four provinces of southern China.

Methods: Plasma samples were collected from the newly diagnosed HIV-1 individuals reported in 2006 in Guangdong, Guangxi, Jiangxi and Hunan province. The gag and env gene fragments were amplified from RNA template extracted from plasma using RT and nested PCR methods. CRF01_AE sequences were analyzed by phylogenetic methods and characterized by calculating the genetic distance and Entropy analysis.

Results: Two main epidemic clusters were found to exist in the CRF01_AE strains from 210 HIV-1 CRF01_ AE infected individuals collected in the 4 provinces, southern China. It was found that no international reference strain was closely correlated with cluster I, which including 123 samples. The strains in cluster II, consisting 57 cases of samples, were closely related with the strains identified in Vietnam. Genetic distance analysis of gag and env genes showed that the diversity of cluster I was obviously less than that of cluster II. Data on nucleotide polymorphism showed that nucleotides compositions of 42 sites in gag and 40 sites in env were significantly different between the two clusters. When compared with cluster II, the polymorphism decreased at 61 nucleotide sites but increased at 21 sites in cluster I.

Conclusion: This was the first report describing that two main epidemic clusters were existed in CRF01_AE strains prevailing in the 4 provinces, Southern China. The virus in cluster I was the dominant strain in this region, with shorter period of circulation and higher proportion seen in the HIV-infected population, which might belong to CRF01_AE strain with certain features facilitating the spread of the virus. The virus in cluster II was highly homology with the CRF01_AE strains from Vietnam, and seemed to have had several events of epidemics in populations in border regions of China and Vietnam.