Investigation of disease and intervention in populations of men having sex with men (MSM) has garnered attention globally, a primary reason being the rapid increase in the prevalence of human immunodeficiency virus (HIV)-1 among MSM. The purpose of this study was to understand the current HIV-1 molecular characteristics and characterize HIV-1 transmission networks in the MSM population. Nine hundred and fourteen newly diagnosed HIV-positive MSM were included in this study. The HIV-1 pol gene region was amplified and sequenced. A maximum likelihood phylogenetic tree was constructed, and transmission clusters were identified using 1.5% distance and 0.9 bootstrap values. In total, 767 sequences were successfully obtained, with CRF01_AE being the major genotype (43.3%, 332/767), followed by CRF07_BC (31.3%, 240/767), CRF67_01B (7.2%, 55/767), and URF (6.4%, 49/767). The transmitted HIV drug resistance rate was 4.0% (31/767), and the most common mutations were E138G (n = 4) and G190A (n = 4). A total of 182 (23.7%) sequences were included in the HIV-1 transmission networks, forming 79 clusters. Four clusters were identified as fast-growing, and the proportion of young MSM was higher than that of non-MSM (51.6% vs. 31.8%). The genetic diversity of HIV-1 in Jiangsu was complex, and cross-region transmission might exist for CRF67_01B. Transmission among young MSM within networks was greater than the other age groups; thus, they could be essential in the control of the HIV epidemic in Jiangsu. This study was approved by the ethical review board of the National Center for AIDS/STD Control and Prevention (Project No. X140617334).
Keywords: HIV-1 transmission network; MSM; molecular epidemiology; transmitted drug resistance.