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      HBV Immune-Therapy: From Molecular Mechanisms to Clinical Applications

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          Abstract

          Chronic hepatitis B virus (HBV) infection represents a worldwide public health concern with approximately 250 million people chronically infected and at risk of developing liver cirrhosis and hepatocellular carcinoma. Nucleos(t)ide analogues (NUC) are the most widely used therapies for HBV infection, but they often require long-lasting administration to avoid the risk of HBV reactivation at withdrawal. Therefore, there is an urgent need to develop novel treatments to shorten the duration of NUC therapy by accelerating virus control, and to complement the effect of available anti-viral therapies. In chronic HBV infection, virus-specific T cells are functionally defective, and this exhaustion state is a key determinant of virus persistence. Reconstitution of an efficient anti-viral T cell response may thus represent a rational strategy to treat chronic HBV patients. In this perspective, the enhancement of adaptive immune responses by a checkpoint inhibitor blockade, specific T cell vaccines, lymphocyte metabolism targeting, and autologous T cell engineering, including chimeric antigen receptor (CAR) and TCR-redirected T cells, constitutes a promising immune modulatory approach for a therapeutic restoration of protective immunity. The advances of the emerging immune-based therapies in the setting of the HBV research field will be outlined.

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          Most cited references79

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          The blockade of immune checkpoints in cancer immunotherapy.

          Among the most promising approaches to activating therapeutic antitumour immunity is the blockade of immune checkpoints. Immune checkpoints refer to a plethora of inhibitory pathways hardwired into the immune system that are crucial for maintaining self-tolerance and modulating the duration and amplitude of physiological immune responses in peripheral tissues in order to minimize collateral tissue damage. It is now clear that tumours co-opt certain immune-checkpoint pathways as a major mechanism of immune resistance, particularly against T cells that are specific for tumour antigens. Because many of the immune checkpoints are initiated by ligand-receptor interactions, they can be readily blocked by antibodies or modulated by recombinant forms of ligands or receptors. Cytotoxic T-lymphocyte-associated antigen 4 (CTLA4) antibodies were the first of this class of immunotherapeutics to achieve US Food and Drug Administration (FDA) approval. Preliminary clinical findings with blockers of additional immune-checkpoint proteins, such as programmed cell death protein 1 (PD1), indicate broad and diverse opportunities to enhance antitumour immunity with the potential to produce durable clinical responses.
            • Record: found
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            CD8 T Cell Exhaustion During Chronic Viral Infection and Cancer

            Exhausted CD8 T (Tex) cells are a distinct cell lineage that arise during chronic infections and cancers in animal models and humans. Tex cells are characterized by progressive loss of effector functions, high and sustained inhibitory receptor expression, metabolic dysregulation, poor memory recall and homeostatic self-renewal, and distinct transcriptional and epigenetic programs. The ability to reinvigorate Tex cells through inhibitory receptor blockade, such as αPD-1, highlights the therapeutic potential of targeting this population. Emerging insights into the mechanisms of exhaustion are informing immunotherapies for cancer and chronic infections. However, like other immune cells, Tex cells are heterogeneous and include progenitor and terminal subsets with unique characteristics and responses to checkpoint blockade. Here, we review our current understanding of Tex cell biology, including the developmental paths, transcriptional and epigenetic features, and cell intrinsic and extrinsic factors contributing to exhaustion and how this knowledge may inform therapeutic targeting of Tex cells in chronic infections, autoimmunity, and cancer.
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              Epigenetic stability of exhausted T cells limits durability of reinvigoration by PD-1 blockade.

              Blocking Programmed Death-1 (PD-1) can reinvigorate exhausted CD8 T cells (TEX) and improve control of chronic infections and cancer. However, whether blocking PD-1 can reprogram TEX into durable memory T cells (TMEM) is unclear. We found that reinvigoration of TEX in mice by PD-L1 blockade caused minimal memory development. After blockade, reinvigorated TEX became reexhausted if antigen concentration remained high and failed to become TMEM upon antigen clearance. TEX acquired an epigenetic profile distinct from that of effector T cells (TEFF) and TMEM cells that was minimally remodeled after PD-L1 blockade. This finding suggests that TEX are a distinct lineage of CD8 T cells. Nevertheless, PD-1 pathway blockade resulted in transcriptional rewiring and reengagement of effector circuitry in the TEX epigenetic landscape. These data indicate that epigenetic fate inflexibility may limit current immunotherapies.

                Author and article information

                Journal
                Int J Mol Sci
                Int J Mol Sci
                ijms
                International Journal of Molecular Sciences
                MDPI
                1422-0067
                05 June 2019
                June 2019
                : 20
                : 11
                : 2754
                Affiliations
                [1 ]Laboratory of Viral Immunopathology, Unit of Infectious Diseases and Hepatology, Azienda-Ospedaliero-Universitaria di Parma, Parma 43126, Italy; cboni@ 123456ao.pr.it (C.B.); barili.valeria@ 123456gmail.com (V.B.); greta.acerbi@ 123456gmail.com (G.A.); rossi.marzia@ 123456gmail.com (M.R.); avecchi2@ 123456ao.pr.it (A.V.); dilettal@ 123456hotmail.com (D.L.); apenna@ 123456ao.pr.it (A.P.); gmissale@ 123456ao.pr.it (G.M.); cferrari00@ 123456gmail.com (C.F.)
                [2 ]Department of Medicine and Surgery, University of Parma, Parma 43126, Italy
                Author notes
                [* ]Correspondence: pfisicaro@ 123456ao.pr.it ; Tel.: +39-0521-703865; Fax: +39-0521-703857
                [†]

                These authors contributed equally to this work.

                Author information
                https://orcid.org/0000-0002-7630-5180
                https://orcid.org/0000-0001-7711-2156
                https://orcid.org/0000-0003-3720-9214
                Article
                ijms-20-02754
                10.3390/ijms20112754
                6600394
                31195619
                958403d8-772e-48be-81ee-853a92891d9c
                © 2019 by the authors.

                Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/).

                History
                : 29 April 2019
                : 04 June 2019
                Categories
                Review

                Molecular biology
                chronic hbv infection,t cell exhaustion,immune-therapy
                Molecular biology
                chronic hbv infection, t cell exhaustion, immune-therapy

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