Our findings showed that CRF01_AE accounted for the majority (55.6%) of HIV-1-infections in MSM of Anhui province. This is consistent with the results of a national survey of HIV-1 molecular epidemiology in 2006, which reported that CRF07_BC (35.5%), CRF01_AE (27.6%), CRF08_BC (20.1%), and subtype B' (9.6%) were the four predominant HIV-1 strains in China . Furthermore, CRF01_AE has replaced subtype B as the most common subtype among MSM [16, 22]. The dominance of CRF01_AE was observed among MSM in coastal cities and provinces, such as Tianjin (88.9%), Jiangsu (70%), Shandong (77.8%), and Zhejiang (100%), in one province of central China, Shanxi (84.6%), and in one province of western China, Gansu (50%) .
In this study, a high proportion of MSM (30.9%) were married or divorced, raising concerns about the risk of acquiring HIV-1 from or transmitting HIV-1 to their sexual partners. Various forms of HIV transmission, including both homosexual and heterosexual behavior, likely exist among MSM of Liaoning province . Therefore, further study should be carried out to determine which subtypes of HIV-1 predominantly infect the heterosexuals and IDUs.
We focused on HIV-1-infected treatment-naive MSM in Anhui province, and found that the overall TDR rate was 3.0%, slightly lower than the national level and Liaoning province [23, 24]. The first nationwide survey of TDR in HIV-1-infected treatment-naive individuals was conducted in 2005, and the national TDR rate was reported to be 3.8% . In 2011, the overall TDR rate was 4.9% among HIV-1-infected treatment-naive MSM in 19 Chinese provinces/cities (Anhui province was not included) . According to an investigation in Liaoning province, 4.5% of ART-naive MSM had drug-resistant strains .
We report that 1.5% of samples were resistant to NRTIs, 1.5% of samples were resistant to NNRTIs, and none were resistant to PIs. Specific mutations included L210W, Y181C, and G190A, which confers different levels of drugs resistance. However, we detected many minor mutations which could compensate for the reduced fitness of resistant mutants, even though the minor mutations have not previously been associated with decreased in vitro susceptibility. Other commonly observed mutations were T69A/N/S, V179E, L10I/L/V, V11I/V, L33F, and A71A/T/V; none of these mutations is known to confer drug resistance to NRTIs, NNRTIs, or PIs.
Specific polymorphisms may occur in particular subtypes. For example, L10V, V11I/V, L33F, T69A/N/S, and P236L were present only in individuals with CRF01_AE strains. These mutations do not affect the susceptibility to ARV drugs. However, they might influence the emergence of drug-resistant viruses by modifying drug susceptibility and/or virus replication . The present study found that substitutions of A71T/V and L10I often appeared in CRF07_BC, which was different from other studies reporting that substitutions of A71T/V often appeared in B viruses, whereas L10I was frequently discovered in CRF01_AE viruses . A98G and V179E were excluded from the WHO list of SDRMs because of high occurrence in viruses from treatment-naive individuals. A98G has been shown to confer low-level resistance against EFV and NVP, and V179D in CRF01_AE/CRF07_BC recombinant viruses has been shown to confer low-level resistance against EFV and intermediate level resistance against NVP, while V179D in CRF01_AE viruses does not affect resistance to any RT drugs (data not published). This phenomenon is worthy of further study.
Our data represent only TDR in HIV-1-infected treatment-naive MSM in Anhui province; therefore, the results may not be representative of other areas. Nevertheless, these data warn us that HIV transmitted-drug-resistant isolates may be prevalent among HIV-1-infected treatment-naive MSM, which will no doubt compromise the success of future ART in these patients.
There were several limitations in our study. First, although all the subjects were newly diagnosed as HIV-infected, the date of their infections was not known. However, it is suggested that a substantial proportion of the subjects were infected recently, because more than half of the individuals had CD4 counts of ≥350 cells/μl, and almost half were between 18–29 years old. Second, the prevalence of TDR might be underestimated, because some mutations may have disappeared over time due to lack of replicative fitness. However, some NNRTI-related mutations, such as K103N, can persist for a long period of time [27, 28].