OBJECTIVEA molecular technique based on quasispecies analysis for tracing postexposure HIV transmission was applied in an investigation of a possible case of HIV transmission after blood transfusion.

METHODSSixteen plasma specimens were collected from 3 HIV infections (T1-T3) involved in a possible HIV transmission chain and 13 HIV/AIDS (C1-C13) controls. The RNAs were extracted and then amplified by RT-PCR, the PCR products were cloned and sequenced.BioEdit 6.0.7 and MEGA 4.0 software were used to analyze gene sequences, calculate gene dispersion ratio and construct phylogenetic tree.

RESULTSThe sequences of 13 specimens were successfully obtained.The HIV strains from T1, T2 and T3 were CRF07_BC recombinants, those from 5 out of the 6 controls lived in the same city with T2 and T3 were CRF07_BC recombinants as well, while those from 4 controls living in the same city with T1 were CRF01_AE recombinants. Compared with the clone sequences from T1, the mean gene dispersion ratio of T2 was the least (2.0%), followed by C12 (2.8%) , T3 (2.9%) and others. The phylogenetic tree showed that all clones from T1, T2, T3 and C12 might cluster together,and implied that the direction of HIV transmission was from T3 to T2, and then to T1.

CONCLUSIONThe results support the possible epidemiological clue that HIV was transmitted from T3 to T2, and then to T1, indicating that molecular epidemiological investigation could provide more direct evidence for tracing postexposure HIV transmission.