Objective  To understand the spread characteristics and pre-treatment drug resistance of HIV-1 in newly reported HIV-1 infection cases in Zigong, Sichuan province, and provide scientific evidence for the development of individualized treatment programs and effective interventions.

Methods Collect plasma samples and demographic information from newly reported HIV-1 infected individuals in Zigong City from 2022 to 2024, amplify the pol region to obtain gene sequences, construct a phylogenetic tree to determine genetic subtypes, and upload the sequences to the Stanford University HIV Drug Resistance Database in the USA to analyze drug resistance. Using a 0.5% genetic distance as the threshold, construct a molecular transmission network to analyze the characteristics of drug resistance transmission and network associations.

Results A total of 1 523 pol gene region sequences were obtained, the main genetic subtypes were CRF07_BC ( 52.26%), CRF01_AE ( 22.72%), CRF08_BC ( 16.41%), and CRF85_BC ( 4.01%). There were significant differences among different genetic subtypes in terms of age (χ²=39.665, P<0.001), educational level (χ²=10.657, P=0.031), transmission route (χ²=21.403, P=0.006), and drug resistance status (χ²=52.520, P<0.001) of the HIV-1 infection cases. Drug resistance monitoring of 1 523 samples from HIV-1 infection cases showed that 173 samples had varying degrees of drug resistance, with an overall drug resistance rate of 11.35%. The drug resistance rate was 7.81% (119/1 523) for non-nucleoside reverse transcriptase inhibitors (NNRTIs), 1.31% (20/1 523) for nucleoside reverse transcriptase inhibitors (NRTIs) and 1.51% (23/1 523) for protease inhibitors (PIs). The main drug resistance mutation loci of NNRTIs were K103 and E138, and the combined mutation loci with relatively high proportions were K103N/KN/KNRS and E138A/EA/EG/EK/K. Based on the genetic distance of 0.5%, 705 sequences were enrolled in the network (46.29%), forming 150 molecular clusters. Subtype CRF07_BC had the highest clustering rate. There were 2 drug-resistant transmission clusters, with Q58E and M46I as the main mutation loci. In addition, a large drug-resistant transmission cluster with 13 nodes was also detected in subtype CRF85_BC, with E138A as the main mutation locus.

Conclusion The circulating subtypes of HIV-1 in Zigong were complex. It is necessary to pay attention to the key transmission molecular clusters and take necessary interventions to prevent the spread of HIV-1 infection. Meanwhile, the drug resistance rate of HIV-1 infection cases before antiviral treatment reached a medium level. Pretreatment drug resistance monitoring should be included in the management of HIV infection cases. Through the analysis on drug resistance mutation loci, the drug resistance characteristics of different subtypes and their impact on treatment can be clarified.