[Study on the distribution of human immunodeficiency virus-1 subtypes in different regions of China and mother-to-child transmission].

ABSTRACT

OBJECTIVE: To study the distribution of human immunodeficiency virus (HIV)-1 genotypes in major prevalent regions of China and to illustrate the relationship between HIV-1 subtypes and mother-to-child transmission in a retrospective cohort. METHODS: HIV-1 gag p17 and env C2-V4 region were amplified by nested-polymerase chain reaction (nPCR) and the sequences were obtained by sequencing gag nPCR products or clones of env gene. RESULTS: 60 HIV-1 positive individuals were subject to typing for gag p17 and 69 for env C2-V4 region. Single clade was only found in Henan (subtype B') and Xinjiang (subtype C), and subtypes C and E were demonstrated in Yunnan. These regions represented most of the HIV-1 infections in China. Multiple subtypes (A, B, C, E, etc.) were found in Beijing and Shanghai, where HIV infections were still in low level. The sequences of subtype C were less diversive in Xinjiang (p17 0.0192 +/- 0.0078, C2-V4 0.0455 +/- 0.0145) than in Yunnan (p17 0.0279 +/- 0.0102, C2-V4 0.0482 +/- 0.0171), but all of them clustered in "C" branch in phylogenetic trees. Trafficking of subtype C from Yunnan to Xinjiang was found but had already been reported by others. Compared to subtype C, subtype E was quite divergent (p17 0.0473 +/- 0.0105, C2-V4 0.1114 +/- 0.0112) in Yunnan, but no recombination was found in the C2-V4 region of env gene. Highe divergence of subtype B' was found in Henan and the peripheral provinces (p17 0.0381 +/- 0.0101, C2-V4 0.0691 +/- 0.0166), which might be attributed to the early epidemics of HIV-1 in these areas (early 1990's). In maternal-child cohort, subtypes B (7/21), C (11/21), E (1/21) and undefined types (2/21) were identified in non-transmitting HIV-1 positive mothers, while only subtype B (7/11) and C (4/11) appeared in transmitting HIV-1 positive mothers. The rate of transmission was 53.8% (7/13) in mothers infected with subtype B and 30.8% (4/13) in those infected with subtype C, but with no significant difference (P = 0.196). The imbalancing distribution of subtypes might be explained by the fact that transfusion or illegal blood would increased mother-to-child transmission on HIV-1 and most of mothers with clade B were infected by illegal blood transfusion in this cohort. In addition, most of the maternal-child pair's sequences clustered in gag or env phylogenetic trees but only a few did disperse among the unrelated patients because children were older (>/= 4 years). CONCLUSION: The characteristics of HIV-1 clade's distribution differed over most parts of China but no difference was demonstrated between subtype B and C in mother-to-child transmission on HIV-1.