ABSTRACT
Chronic HBV infection is a major cause of liver disease and cancer worldwide. Approaches for cure are lacking, and the knowledge of virus-host interactions is still limited. Here, we perform a genome-wide gain-of-function screen using a poorly permissive hepatoma cell line to uncover host factors enhancing HBV infection. Validation studies in primary human hepatocytes identified CDKN2C as an important host factor for HBV replication. CDKN2C is overexpressed in highly permissive cells and HBV-infected patients. Mechanistic studies show a role for CDKN2C in inducing cell cycle G1 arrest through inhibition of CDK4/6 associated with the upregulation of HBV transcription enhancers. A correlation between CDKN2C expression and disease progression in HBV-infected patients suggests a role in HBV-induced liver disease. Taken together, we identify a previously undiscovered clinically relevant HBV host factor, allowing the development of improved infectious model systems for drug discovery and the study of the HBV life cycle.
Subject(s)
Cyclin-Dependent Kinase Inhibitor p18/genetics , Gain of Function Mutation , Genetic Testing/methods , Genome-Wide Association Study/methods , Hepatitis B/genetics , Cell Line, Tumor , Cyclin-Dependent Kinase Inhibitor p18/metabolism , Gene Expression Profiling/methods , HEK293 Cells , Hep G2 Cells , Hepatitis B/metabolism , Hepatitis B/virology , Hepatitis B virus/physiology , Host Microbial Interactions , Humans , Kaplan-Meier Estimate , Liver/metabolism , Liver/pathology , Liver/virology , RNA Interference , Virus Replication/physiologyABSTRACT
Chronic hepatitis B, C and D virus (HBV, HCV and HDV) infections are a major cause of liver disease and cancer worldwide. Despite employing distinct replication strategies, the three viruses are exclusively hepatotropic, and therefore depend on hepatocyte-specific host factors. The sodium taurocholate co-transporting polypeptide (NTCP), a transmembrane protein highly expressed in human hepatocytes that mediates the transport of bile acids, plays a key role in HBV and HDV entry into hepatocytes. Recently, NTCP has been shown to modulate HCV infection of hepatocytes by regulating innate antiviral immune responses in the liver. Here, we review the current knowledge of the functional role and the molecular and cellular biology of NTCP in the life cycle of the three major hepatotropic viruses, highlight the impact of NTCP as an antiviral target and discuss future avenues of research.
Subject(s)
Hepacivirus/genetics , Hepatitis B virus/genetics , Hepatitis Delta Virus/genetics , Organic Anion Transporters, Sodium-Dependent/genetics , Symporters/genetics , Hepacivirus/pathogenicity , Hepatitis B/genetics , Hepatitis B/virology , Hepatitis B virus/pathogenicity , Hepatitis C/genetics , Hepatitis C/virology , Hepatitis D/genetics , Hepatitis D/virology , Hepatitis Delta Virus/pathogenicity , Hepatocytes/pathology , Humans , Life Cycle Stages/genetics , Virus InternalizationABSTRACT
Bispecific antibodies (bsAbs) pave the way for novel therapeutic modes of action along with potential benefits in several clinical applications. However, their generation remains challenging due to the necessity of correct pairings of two different heavy and light chains and related manufacturability issues. We describe a generic approach for the generation of fully human IgG-like bsAbs. For this, heavy chain repertoires from immunized transgenic rats were combined with either a randomly chosen common light chain or a light chain of an existing therapeutic antibody and screened for binders against tumor-related targets CEACAM5 and CEACAM6 by yeast surface display. bsAbs with subnanomolar affinities were identified, wherein each separate binding arm mediated specific binding to the respective antigen. Altogether, the described strategy represents a combination of in vivo immunization with an in vitro selection method, which allows for the integration of existing therapeutic antibodies into a bispecific format.
