First HIV-2 Case Reported in Sichuan Province: Implications for HIV Prevention and Treatment in China

         In September 2025, the Chinese Journal of AIDS & STD reported the first HIV-2 case in Sichuan Province. The case was identified in January 2025 during a routine health screening in a county of Meishan City. Following confirmatory tests, nucleic acid detection, and sequence analysis, it was diagnosed as an HIV-2 infection. This marks the first HIV-2 case in Sichuan since the province’s initial HIV report in 1992. Researchers noted that this discovery underscores the potential complexity of HIV lineages in China, posing new requirements for the existing prevention system, laboratory testing, and treatment monitoring. Although HIV-2 has lower transmissibility and a limited epidemic scope, its detection reflects the ongoing evolutionary biology of the AIDS virus. Globally, HIV-1 remains the dominant strain driving the epidemic, with higher pathogenicity and mutation rates, making it the primary focus of AIDS research and prevention.

         HIV-2 (Human Immunodeficiency Virus Type 2) is a human retrovirus belonging to the Lentivirus genus. Structurally similar to HIV-1, it is an enveloped virus containing a viral capsid, matrix proteins, viral nucleic acid (double-stranded positive-sense RNA), and essential enzymes (reverse transcriptase, integrase, and protease). Its genome encodes the typical "gag-pol-env" structure: gag encodes structural proteins (e.g., matrix MA, capsid CA, nucleocapsid NC), pol encodes enzymes (protease PR, reverse transcriptase RT, integrase IN), and env encodes envelope glycoproteins (SU and TM subunits). Regarding accessory proteins, HIV-2 differs from HIV-1 in some aspects; for instance, HIV-2 encodes Vpx (absent in HIV-1) in addition to Vpr. Vpx plays a role in counteracting host antiviral restriction factors such as SAMHD1.

         HIV-2 exhibits a "low replication, high persistence" pathogenic profile. A distinctive feature of its replication cycle is the Vpx-mediated degradation pathway of the host restriction factor SAMHD1: Vpx recruits the CRL4^DCAF1 complex to ubiquitinate SAMHD1, leading to its proteasomal clearance, thereby increasing dNTP levels in myeloid cells to facilitate reverse transcription. Research from 2024–2025 further revealed that this pathway is not unidirectional—host deubiquitinating enzyme USP37 can partially restore SAMHD1 levels, while the oxygen-sensing complex PHD3-VHL reduces Vpx stability through hydroxylation, indicating a dynamic balance between viral replication and the cellular metabolic environment.

         Additionally, Vpx has been found to regulate transcription, DNA repair, and inflammatory pathways, contributing to a cellular microenvironment conducive to viral persistence. Structural biology analyses have shown subtle differences in the spatial configuration of the HIV-2 capsid (CA) hexamer and its binding interfaces with host restriction factors compared to HIV-1, potentially explaining its lower pathogenicity and slower disease progression.

         A "milder" mechanism does not equate to epidemiological safety. As of July 2024, approximately 39.9 million people globally are infected with HIV, with about 2 million cases attributed to HIV-2. HIV-2 is primarily prevalent in West Africa and its diaspora communities, though sporadic cases have appeared in Europe, India, and China. Its lower transmission efficiency compared to HIV-1 is linked to lower viral loads, weaker Env-receptor binding, and slower gp41-mediated fusion. However, the confirmed case in Meishan, Sichuan, demonstrates that low-prevalence strains can be detected in routine health screenings, reflecting the increasing sensitivity of China's HIV subtyping and prevention system. Simultaneously, it exposes limitations in laboratory confirmation and nucleic acid monitoring, which remain centered on HIV-1.

         Diagnostically, due to antigenic differences between HIV-2 and HIV-1, HIV-2 samples often show weak antibody responses and low RNA levels, increasing the risk of missed detection in routine tests. The recommended diagnostic workflow includes fourth-generation HIV-1/2 antigen-antibody combination testing, followed by subtyping confirmation and nucleic acid or DNA testing, integrated with clinical history and geographic risk factors.

         For treatment, HIV-2 exhibits intrinsic resistance to NNRTIs (non-nucleoside reverse transcriptase inhibitors). Current guidelines recommend a first-line regimen of two NRTIs plus an INSTI (integrase strand transfer inhibitor), or, in specific cases, a combination with protease inhibitors such as darunavir or lopinavir. Clinical studies have confirmed that INSTIs like raltegravir achieve stable viral suppression and immune restoration in HIV-2 patients.

         abinScience has provided antibodies and recombinant proteins for multiple studies, aiding researchers in analyzing virulence factors, signaling pathways, and host responses. Founded in Strasbourg, France, abinScience leverages the region's robust research ecosystem to focus on developing and producing high-quality life science reagents. Committed to its vision of "Empowering Bioscience Discovery," abinScience provides efficient and reliable experimental solutions to support cutting-edge life science research worldwide. Below is a list of HIV-2-related protein and antibody products offered by abinScience:

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