Identification of a novel HIV-1 circulating recombinant form (CRF209_cpx) and its descendant unique recombinant form (URF) CRF209_cpx/B among MSM in Guangdong, southern China

BACKGROUND: The epidemic of human immunodeficiency virus type 1 (HIV-1) continues to pose a significant global health challenge, with increasing genetic diversity. The co-circulation of multiple subtypes among the local population facilitates the emergence of unique or circulating recombinant forms (URFs or CRFs). In China, the predominant strains include CRF07_BC, CRF01_AE, CRF55_01B, and subtype B. This study characterizes a novel CRF209_cpx and its descendant recombinant CRF209_cpx/B among men who have sex with men (MSM) in Guangdong, southern China. METHODS: Individuals infected with URFs with similar genetic characteristics were recruited during routine surveillance of pretreatment drug resistance. Near full-length genomes (NFLGs) were amplified with two overlapping fragments using a serial dilution nested PCR approach after reverse transcription. We used SimPlot and IQ-TREE softwares to conduct recombination analyses and phylogenetic inferences. Time-scaled maximum clade credibility (MCC) phylogenetic trees were reconstructed using BEAST software to estimate evolutionary origins. Genotypic drug resistance mutations were interpreted via the Stanford HIV Database, and coreceptor usage was predicted using geno2pheno coreceptor 2.5 and the HIVcoPRED tool. RESULTS: Four NFLG sequences were obtained and identified as a novel CRF209_cpx, generated by recombination among CRF01_AE, CRF07_BC and subtype B. Phylogenetic analyses revealed that all the parental segments clustered with lineages prevalent among MSM in China. Bayesian evolutionary analysis estimated that the most recent common ancestor (tMRCA) of CRF209_cpx to have evolved between 2011 and 2013. The fifth strain was identified as a URF recombined from nascent CRF209_cpx and B. No transmitted drug resistance mutation was detected in these five sequences. The four CRF209_cpx sequences primarily utilized the CXCR4 coreceptor, while the URF exhibited R5/X4 dual tropism. CONCLUSIONS: The emergence of the complex CRF209_cpx and novel URF of CRF209_cpx/B highlights the active HIV-1 epidemic within the MSM population in Guangdong, underscoring the necessity for enhanced molecular surveillance and precise public health intervention in this key population.