T lymphocyte dysfunction contributes to human immunodeficiency virus type 1 (HIV-1) disease progression by impairing antivirus cellular immunity. However, the mechanisms of HIV-1 infection-mediated T cell dysfunction are not completely understood. Here, we provide evidence that expansion of monocytic myeloid-derived suppressor cells (M-MDSCs) suppressed T cell function in HIV-1-infected individuals. We observed a dramatic elevation of M-MDSCs (HLA-DR ^−/low CD11b ⁺ CD33 ^+/high CD14 ⁺ CD15 ⁻ cells) in the peripheral blood of HIV-1-seropositive subjects ( n = 61) compared with healthy controls ( n = 51), despite efficacious antiretroviral therapy for nearly 2 years. The elevated M-MDSC frequency in HIV-1 ⁺ subjects correlated with prognostic HIV-1 disease markers, including the HIV-1 load ( r = 0.5957; P < 0.0001), CD4 ⁺ T cell loss ( r = −0.5312; P < 0.0001), and activated T cells ( r = 0.4421; P = 0.0004). Functional studies showed that M-MDSCs from HIV-1 ⁺ subjects suppressed T cell responses in both HIV-1-specific and antigen-nonspecific manners; this effect was dependent on the induction of arginase 1 and required direct cell-cell contact. Further investigations revealed that direct HIV-1 infection or culture with HIV-1-derived Tat protein significantly enhanced human MDSC generation in vitro , and MDSCs from healthy donors could be directly infected by HIV-1 to facilitate HIV-1 replication and transmission, indicating that a positive-feedback loop between HIV-1 infection and MDSC expansion existed. In summary, our studies revealed a novel mechanism of T cell dysfunction in HIV-1-infected individuals and suggested that targeting MDSCs may be a promising strategy for HIV-1 immunotherapy.

Summary: SARS-CoV-2 infection have caused global pandemic and claimed over 5,000,000 tolls ^1–4 . Although the genetic sequences of their etiologic viruses are of high homology, the clinical and pathological characteristics of COVID-19 significantly differ from SARS ^5,6 . Especially, it seems that SARS-CoV-2 undergoes vast replication in vivo without being effectively monitored by anti-viral immunity ⁷ . Here, we show that the viral protein encoded from open reading frame 8 (ORF8) of SARS-CoV-2, which shares the least homology with SARS-CoV among all the viral proteins, can directly interact with MHC-I molecules and significantly down-regulates their surface expression on various cell types. In contrast, ORF8a and ORF8b of SARS-CoV do not exert this function. In the ORF8-expressing cells, MHC-I molecules are selectively target for lysosomal degradation by an autophagy-dependent mechanism. As a result, CTLs inefficiently eliminate the ORF8-expressing cells. Our results demonstrate that ORF8 protein disrupts antigen presentation and reduces the recognition and the elimination of virus-infected cells by CTLs ⁸ . Therefore, we suggest that the inhibition of ORF8 function could be a strategy to improve the special immune surveillance and accelerate the eradication of SARS-CoV-2 in vivo.

Comprehensively elucidating the molecular mechanisms of human immunodeficiency virus type 1 (HIV-1) latency is a priority to achieve a functional cure. As current 'shock' agents failed to efficiently reactivate the latent reservoir, it is important to discover new targets for developing more efficient latency-reversing agents (LRAs). Here, we found that TRIM28 potently suppresses HIV-1 expression by utilizing both SUMO E3 ligase activity and epigenetic adaptor function. Through global site-specific SUMO-MS study and serial SUMOylation assays, we identified that P-TEFb catalytic subunit CDK9 is significantly SUMOylated by TRIM28 with SUMO4. The Lys44, Lys56 and Lys68 residues on CDK9 are SUMOylated by TRIM28, which inhibits CDK9 kinase activity or prevents P-TEFb assembly by directly blocking the interaction between CDK9 and Cyclin T1, subsequently inhibits viral transcription and contributes to HIV-1 latency. The manipulation of TRIM28 and its consequent SUMOylation pathway could be the target for developing LRAs.

BACKGROUND. Chimeric antigen receptor (CAR) T cells have emerged as an approach to treat malignant tumors. This strategy has also been proposed for the treatment of HIV-1 infection. We have developed a broadly neutralizing antibody–derived (bNAb-derived) CAR T cell therapy that can exert specific cytotoxic activity against HIV-1–infected cells. METHODS. We conducted an open-label trial of the safety, side-effect profile, pharmacokinetic properties, and antiviral activity of bNAb-derived CAR T cell therapy in individuals infected with HIV-1 who were undergoing analytical interruption of antiretroviral therapy (ART). RESULTS. A total of 14 participants completed only a single administration of bNAb-derived CAR T cells. CAR T cell therapy administration was safe and well tolerated. Six participants discontinued ART, and viremia rebound occurred in all of them, with a 5.3-week median time. Notably, the cell-associated viral RNA and intact proviruses decreased significantly after CAR T cell treatment. Analyses of HIV-1 variants before or after CAR T cell administration suggested that CAR T cells exerted pressure on rebound viruses, resulting in a selection of viruses with less diversity and mutations against CAR T cell–mediated cytotoxicity. CONCLUSION. No safety concerns were identified with adoptive transfer of bNAb-derived CAR T cells. They reduced viral reservoir. All the rebounds were due to preexisting or emergence of viral escape mutations. TRIAL REGISTRATION. ClinicalTrials.gov (NCT03240328). FUNDING. Ministry of Science and Technology of China, National Natural Science Foundation of China, and Department of Science and Technology of Guangdong Province.

Since the outbreak of the coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the public health worldwide has been greatly threatened. The development of an effective treatment for this infection is crucial and urgent but is hampered by the incomplete understanding of the viral infection mechanism and the lack of specific antiviral agents. We previously reported that teicoplanin, a glycopeptide antibiotic that has been commonly used in the clinic to treat bacterial infection, significantly restrained the cell entry of Ebola virus, SARS-CoV and MERS-CoV by specifically inhibiting the activity of cathepsin L (CTSL). Here, we found that the cleavage sites of CTSL on the Spike of SARS-CoV-2 were highly conserved among all the variants. The treatment with teicoplanin suppressed the proteolytic activity of CTSL on Spike and prevented the cellular infection of different pseudotyped SARS-CoV-2 viruses. Teicoplanin potently prevented the entry of authentic SARS-CoV-2 into the cellular cytoplasm with an IC ₅₀ of 2.038 μM for the Wuhan-Hu-1 reference strain and an IC ₅₀ of 2.116 μM for the SARS-CoV-2 (D614G) variant. The pre-treatment of teicoplanin also prevented SARS-CoV-2 infection in hACE2 mice. In summary, our data reveal that CTSL is required for both SARS-CoV-2 and SARS-CoV infection and demonstrate the therapeutic potential of teicoplanin for universal anti-CoVs intervention. Importance: Disease prevention and treatment are two important countermeasures to end the coronavirus disease 2019 (COVID-19). However, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19, evolves all the time, resulting in the emerging of many epidemic SARS-CoV-2 mutants, which significantly impairs the effectiveness of early strain-based vaccines and antibodies. Developing universal vaccines and broad-spectrum antiviral drugs are essential to confront SARS-CoV-2 mutants including those may emerge in the future. Our study reported here showed that the cleavage sites of cellular cathepsin L (CTSL) are highly conserved among all the SARS-CoV-2 mutants and SARS-CoV. The CTSL inhibitor teicoplanin not only inhibited the cell entry of two live SARS-CoV-2 strains and various pseudotyped viruses but also prevented live virus infection in animal models. Based on our previous finding that teicoplanin also inhibited SARS-CoV and MERS-CoV infection, we believe that teicoplanin possesses the potential to become a universal anti-CoVs drug.