Objective: The current available assays for HIV subtyping, such as sequence-based phylogenetic analysis or heteroduplex mobility assay (HMA), are labor-intensive and time-consuming. The authors have just developed a simple and rapid subtype-screening assay for subtypes B, C, and CRF01-AE using a single nested multiplex PCR.
Methods: Proviral DNA from HIV-positive samples was extracted and subjected to first round PCR with universal primers for gag region that can detect HIV-1 M group isolates. In the second round PCR, three pairs of subtype-specific primers, respectively detecting subtype B, C and CRF01-AE, were added into one tube. The PCR products of different subtypes could be distinguished in agarose-gel electrophoresis. Another pair of primers exclusively detecting the prevalent recombinant B/C strains CRF07-BC and CRF08-BC were designed and used. Additionally, all of these samples were sequenced and analyzed phylogenetically.
Results: Phylogenetic analysis showed that out of 119 samples, there were 43 subtype B samples (Euro-American B 11, Thailand B 32), 54 subtype C, 17 CRF01-AE, 3 subtype A and 2 subtype D samples. The subtype B, C, and CRF01-AE specific primer sets detected 35 (81.4%), 46 (85.2%), and 13(76.5%) samples with accuracy and specificity. Non-specific bands occasionally appeared but did not interfere with interpretation of the results. The primer pairs for CRF07-BC and CRF08-BC amplified target sequences were confirmed by sequencing and phylogenetic analysis. The specificity of all these subtype-specific primers was found to be 100%.
Conclusion: A simple and rapid assay was developed for screening subtypes B, C, CRF01-AE, CRF07-BC and CRF08-BC in China. This assay may have potential application in HIV laboratories in China and worldwide.