The proportion of older HIV-1 infected people in China has increased rapidly in recent years. Elucidation of the transmission characteristics of this high-risk population subgroup is helpful for the development of tailored interventions. A phylogenetic analysis was performed that uses available HIV-1 pol sequences amplified with nested RT-PCR from plasma samples of all newly diagnosed participants spanning from October 2017 to September 2018 in Fuyang, Anhui Province. Transmission clusters were identified as two or more sequences that shared a corresponding node with an aLRT-SH value ≥90 in the maximum-likelihood phylogenetic tree and had an overall mean genetic distance of ≤1.5%. A local transmission cluster was defined as a cluster that had more than 80% of its sequences from Fuyang. The role of older people in local HIV-1 transmission was determined using an integration of molecular and demographic data. Of 362 available sequences, 14 subtypes, and 28 local transmission clusters were identified. It was found that the proportion of older people in the local transmission cluster (69/77, 89.61%) was much higher than that of younger people (46/114, 40.35%) (χ2 test, P < 0.001). In the pretreatment drug resistance analysis, the proportion of sequences with PDRMs in the local transmission cluster was not significantly different between the older people group (57.14%, 4/7) and non-old-aged group (11.11%, 1/9) (Fisher’s exact test, P > 0.05). By combining phylogenetic analyses with demographic data, more detailed information was provided about the local transmission structure in Fuyang. These findings suggested that older people play an important role in local transmission, and more tailored interventions for this population subgroup are urgently needed.

Multiple subtypes were found to be epidemic in the Shenzhen men who have sex with men (MSM) population, which always predicts the emergence of a unique recombinant. In 2012, CRF55_01B was first reported, which later was proven to have originated in MSM in Shenzhen city. In this study, we reported a unique recombinant form (URF) of HIV-1 identified in a man who has had sex with men in Shenzhen city. The strain showed a genomic schematic map similar to CRF55_01B with subtype C segments inserted in the gag and pol genes. The full-length genome was amplified in two halves with 1-kb overlap regions. The PCR products were cloned and sequenced. A recombination detection program showed that two subtype C fragments and two subtype B fragments were inserted into the CRF01_AE backbone genome in the gag and pol regions. In the phylogenetic tree, the subtype C fragments clustered with CRF07_BC variants and the other segments grouped with CRF55_01B strains except for one segment that clustered with CRF01_AE. Similar breakpoints between our strain and CRF65_cpx were also observed. The data suggested that the URF strain might be the recombinant form of CRF55_01B, CRF01_AE, and CRF07_BC. This is the first report of a third generation of recombination of HIV-1 that originated from CRF55_01B in China. The identification of the URF indicated the severity of the HIV epidemic in Shenzhen MSM and the urgent need for epidemiological surveillance of the new recombination.

Homosexual contact is one of the main transmission routes of HIV-1 epidemic in Hebei, China. Several subtypes of HIV are prevalent simultaneously in the population, which always lead to the emergency of unique recombinant forms (URFs). In this study, we reported two new URFs from two HIV-1 positive subjects infected through homosexual contact route in Hebei, China. Phylogenetic and recombinant analyses based on the near full-length genome of the two URFs both revealed the two URFs are the second generation of recombinant strains originated from CRF01_AE and CRF07_BC. The CRF01_AE segments of two URFs located in cluster 4 of CRF01_AE strains in the phylogenetic tree. The emergence of the novel CRF01_AE/CRF07_BC recombinant forms with complicated genomic structures indicated the importance of the continuous monitoring of the HIV-1 epidemic and new URFs among the men who have sex with men populations.

Most HIV subtypes prevalent in China can be found in Shenzhen, including CRF07_BC, CRF01_AE, CRF08_BC, CRF55_01B, and subtype B. Multiple subtypes spreading in the same population always lead to the emergence of unique recombinant strains. Here, we report two unique recombinant forms (SZ44LS7251 and SZ95LS8027) of HIV-1 identified in a heterosexual population. Recombinant analyses were fulfilled based on the near full-length genomes. Both strains comprise subtypes B, C, and CRF01_AE. Phylogenetic analysis reveals that SZ44LS7251 is the second generation recombination originated from CRF55_01B andCRF07_BC, whereas SZ95LS8027 comprises CRF01_AE and CRF07_BC.The emergence of second generation recombination of HIV with complicated genomic structures supposed that high ratio of super infections or coinfections might happen in the Shenzhen area.