IgG78-DM1 inhibits pulmonary fibrosis by targeting and killing CD248-positive myofibroblasts in mice / 细胞与分子免疫学杂志

Objective To investigate the therapeutic effect of targeting and killing CD248-positive myofibroblasts on bleomycin-induced pulmonary fibrosis in mice. Methods IgG78-DM1, an antibody-maytansine 1 (DM1) conjugate targeting CD248, was prepared. The drug conjugation efficiency was measured and calculated by UV spectrophotometer, and the identification of IgG78-DM1 was performed through SDS-PAGE and Western blot analysis. In vitro, the binding activity of IgG78-DM1 on CD248-positive myofibroblasts was detected by flow cytometry and the cytotoxicity of IgG78-DM1 to CD248-positive myofibroblasts was evaluated by CCK-8 assay. In vivo, C57BL/6 male mice were randomly divided into control group, idiopathic pulmonary fibrosis group, human IgG-DM1 (hIgG-DM1) control group, and IgG78-DM1 treatment group. Then, the mouse models with pulmonary fibrosis induced by bleomycin were constructed. Two weeks later, the animal models were intravenously injected with IgG78-DM1. After the treatment of two weeks, lung tissues were collected for Masson staining and Sirius Red staining to evaluate the degree of pulmonary fibrosis. Real-time fluorescence quantitative PCR was used to measure the expression levels of CD248, as well as markers of fibroblastic activation including alpha-smooth muscle actin (α-SMA) and type I collagen alpha 1 (COL1A1). The safety of IgG78-DM1 was preliminarily assessed by conducting liver and kidney function tests. Results IgG78-DM1 was successfully prepared, and its drug conjugation ratio was 3.2. The antibody structure remained stable after conjugation, allowing effective binding and cytotoxicity against CD248-positive myofibroblasts. After treatment with IgG78-DM1, the degree of pulmonary fibrosis in mice significantly reduced, accompanied by the decrease of the expression of CD248, α-SMA, and COL1A1. The liver and kidney function of the mice remained at normal levels compared to the normal control group. Conclusion IgG78-DM1 effectively inhibits pulmonary fibrosis in mice by targeting and killing CD248-positive myofibroblasts. The safety of this strategy is preliminarily assessed.

The Strand-biased Transcription of SARS-CoV-2 and Unbalanced Inhibition by Remdesivir

SARS-CoV-2, a positive single-stranded RNA virus, caused the COVID-19 pandemic. During the viral replication and transcription, the RNA dependent RNA polymerase (RdRp) "jumps" along the genome template, resulting in discontinuous negative-stranded transcripts. In other coronaviruses, the negative strand RNA was found functionally relevant to the activation of host innate immune responses. Although the sense-mRNA architectures of SARS-CoV-2 were reported, its negative strand was unexplored. Here, we deeply sequenced both strands of RNA and found SARS-CoV-2 transcription is strongly biased to form the sense strand. During negative strand synthesis, apart from canonical sub-genomic ORFs, numerous non-canonical fusion transcripts are formed, driven by 3-15 nt sequence homology scattered along the genome but more prone to be inhibited by SARS-CoV-2 RNA polymerase inhibitor Remdesivir. The drug also represses more of the negative than the positive strand synthesis as supported by a mathematic simulation model and experimental quantifications. Overall, this study opens new sights into SARS-CoV-2 biogenesis and may facilitate the anti-viral vaccine development and drug design. One Sentence SummaryStrand-biased transcription of SARS-CoV-2.