Characterization of sexually acquired HIV-1 transmission networks and genetic variation in northern frontier China, 2021-2024.

BACKGROUND

In Baotou, sexual transmission is the primary route of HIV-1 infection among newly reported cases. Given the increasing prevalence in recent years, this study aimed to identify the factors driving local viral spread and analyze the characteristics of pretreatment HIV drug resistance (PDR).

METHODS

Plasma samples were collected from 407 newly reported, treatment-naïve individuals infected via sexual transmission in Baotou between 2021 and 2024. HIV-1 pol gene sequences were obtained using next-generation sequencing (NGS) to infer genotypes, phylogenetic relationships, and molecular transmission networks. Logistic regression models identified factors associated with molecular clustering and high network connectivity. PDR was analyzed using the Stanford University HIV Drug Resistance Database.

RESULTS

Of the 407 individuals, 363 (89.2%) yielded valid HIV-1 pol sequences. The predominant subtypes were CRF07_BC (54.3%), CRF01_AE (29.2%), and CRF55_01B (3.8%). Overall, 148 sequences (40.8%) formed 37 molecular transmission clusters, including two large clusters. Centrality indicators revealed that significant differences between older heterosexual men and men who sex with men (MSM) within large transmission clusters. Analysis of drug-resistant transmission networks revealed three small clusters. The prevalence of PDR to any antiretroviral drugs, nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), and protease inhibitors (PIs) were 7.99% (29/363), 4.41% (16/363), 2.48% (9/363), and 2.20% (8/363), respectively. NNRTI-associated resistance rates were the highest, with most exhibiting moderate to high resistance levels.

CONCLUSION

Older heterosexual men maintain active, localized transmission networks in Baotou. Targeted control measures addressing this high-risk subpopulation are essential to complement existing MSM-focused interventions. The prevalence of NNRTI resistance indicates that ongoing surveillance of resistant strains and pretreatment drug resistance testing remain critical for effective clinical management.