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Background & Aims: Chronic hepatitis B is a global public health problem, and coinfection with hepatitis delta virus (HDV) worsens disease outcome. Here, we describe a hepatitis B virus (HBV) surface antigen (HBsAg)-targeting monoclonal antibody (mAb) with the potential to treat chronic hepatitis B and chronic hepatitis D., Methods: HBsAg-specific mAbs were isolated from memory B cells of HBV vaccinated individuals. In vitro neutralization was determined against HBV and HDV enveloped with HBsAg representing eight HBV genotypes. Human liver-chimeric mice were treated twice weekly with a candidate mAb starting 3 weeks post HBV inoculation (spreading phase) or during stable HBV or HBV/HDV coinfection (chronic phase)., Results: From a panel of human anti-HBs mAbs, VIR-3434 was selected and engineered for pre-clinical development. VIR-3434 targets a conserved, conformational epitope within the antigenic loop of HBsAg and neutralized HBV and HDV infection with higher potency than hepatitis B immunoglobulins in vitro. Neutralization was pan-genotypic against strains representative of HBV genotypes A-H. In the spreading phase of HBV infection in human liver-chimeric mice, a parental mAb of VIR-3434 (HBC34) prevented HBV dissemination and the increase in intrahepatic HBV RNA and covalently closed circular DNA. In the chronic phase of HBV infection or co-infection with HDV, HBC34 treatment decreased circulating HBsAg by >1 log and HDV RNA by >2 logs., Conclusions: The potently neutralizing anti-HBs mAb VIR-3434 reduces circulating HBsAg and HBV/HDV viremia in human liver-chimeric mice. VIR-3434 is currently in clinical development for treatment of patients with chronic hepatitis B or D., Impact and Implications: Chronic infection with hepatitis B virus and co-infection with hepatitis D virus place approximately 290 million individuals worldwide at risk of severe liver disease and cancer. Available treatments result in low rates of functional cure or require lifelong therapy that does not eliminate the risk of liver disease. We isolated and characterized a potent human antibody that neutralizes hepatitis B and D viruses and reduces infection in a mouse model. This antibody could provide a new treatment for patients with chronic hepatitis B and D., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Currently circulating SARS-CoV-2 variants have acquired convergent mutations at hot spots in the receptor-binding domain 1 (RBD) of the spike protein. The effects of these mutations on viral infection and transmission and the efficacy of vaccines and therapies remains poorly understood. Here we demonstrate that recently emerged BQ.1.1 and XBB.1.5 variants bind host ACE2 with high affinity and promote membrane fusion more efficiently than earlier Omicron variants. Structures of the BQ.1.1, XBB.1 and BN.1 RBDs bound to the fragment antigen-binding region of the S309 antibody (the parent antibody for sotrovimab) and human ACE2 explain the preservation of antibody binding through conformational selection, altered ACE2 recognition and immune evasion. We show that sotrovimab binds avidly to all Omicron variants, promotes Fc-dependent effector functions and protects mice challenged with BQ.1.1 and hamsters challenged with XBB.1.5. Vaccine-elicited human plasma antibodies cross-react with and trigger effector functions against current Omicron variants, despite a reduced neutralizing activity, suggesting a mechanism of protection against disease, exemplified by S309. Cross-reactive RBD-directed human memory B cells remained dominant even after two exposures to Omicron spikes, underscoring the role of persistent immune imprinting., (© 2023. The Author(s).)

The appropriate regulation of T lymphocyte functions is key to achieve protective immune responses, while at the same time limiting the risks of tissue damage and chronic inflammation. Deciphering the mechanisms underpinning T cell responses in humans may therefore be beneficial for a range of infectious and chronic diseases. Recently, the development of methods based on CRISPR-Cas9 gene-editing has greatly expanded the available tool-box for the mechanistic studies of primary human T cell responses. While the deletion of a surface protein has become a relatively straightforward task, as long as an antibody for detection is available, the identification and selection of cells lacking an intracellular protein, a non-coding RNA or a protein for which no antibody is available, remain more problematic. Here, we discuss the options currently available to scientists interested in performing gene-editing in primary human T lymphocytes and we describe the optimization of a workflow for the screening and analysis of lymphocytes following gene-editing with CRISPR-Cas9 based on T cell cloning and T7 endonuclease I cleavage assay., Competing Interests: The authors have declared that no competing interests exist.

In mammals, the 5'-methylcytosine (5mC) modification in the genomic DNA contributes to the dynamic control of gene expression. 5mC erasure is required for the activation of developmental programs and occurs either by passive dilution through DNA replication, or by enzymatic oxidation of the methyl mark to 5-hydroxymethylcytosine (5hmC), which can persist as such or undergo further oxidation and enzymatic removal. The relative contribution of each mechanism to epigenetic control in dynamic biological systems still remains a compelling question. To explore this critical issue, we used primary human T lymphocytes, in which two cellular states can be clearly identified, namely quiescent naïve T cells, which are slowly or rarely proliferating, and rapidly proliferating activated T cells. We found that active mechanisms of methylation removal were selectively at work in naïve T cells, while memory T lymphocytes entirely relied on passive, replication-dependent dilution, suggesting that proliferative capacity influences the choice of the preferential demethylation mechanism. Active processes of demethylation appear to be critical in quiescent naïve T lymphocytes for the maintenance of regulatory regions poised for rapid responses to physiological stimuli., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)