Hepatitis C is a highly prevalent liver disease with estimated 170 million chronic carriers worldwide and 5 million carriers in Western Europe. It is caused by Human Hepatitis C Virus (HCV), a (+)-stranded RNA virus belonging to Flaviviridae family. Viral persistence and pathogenesis pose two major questions: what are the mechanisms by which the virus evades clearance by the immune system, causes liver damage in chronic HCV infection, and why does it operate differently in different individuals and groups? Tentative answers to these questions focus on viral diversity, host genetic factors, and direct or/and indirect viral-host interactions. Some of the viral polymorphisms appear to be associated with the clinical course of hepatitis C.
The objective of this project is to characterize polymorphisms in HCV that predispose to viral clearance versus development of chronic liver disease, in the scope with the INTAS Call on Genomics with respect to molecular mechanisms of infectious diseases. In particular, we will explore how viral polymorhisms influence activities of proteins determining viral fitness. This approach is feasible given a wide set of clinical specimens already obtained by co-applicants in on-going studies of immune response in HCV infection from acute stage until resolution or chronization. Using this Biobank, we shall:
Determine sequences of dominant HCV strains circulating in acute infection, pre-extinction viral population in patients clearing HCV, and population circulating in patients after establishment of chronic infection creating HCV sequence database with annotation of outcome;
Complete and summarize the data on anti-HCV immune response in acute and chronic infection; Compile a map of immune pressure sites; Study patterns of immune selection in acute resolving, acute chronizing and chronic HCV infection;
Define regions determining viral replicative fitness and characterize their sequence diversity;
Compare viral diversity in the regions subjected to immune selection, and in the regions determining viral replicative fitness;
Reveal patterns predisposing to HCV clearance versus chronization;
Clone and express in pro- and eukaryotes proteins bearing hallmarks of clearance versus chronization with emphasis on core, and RNA-dependent RNA polymerase (NS5B);
Using representative panel of assays, characterize activities of these proteins in vitro, and modulation of activities with viral evolution;
Relate the in vitro functionality of proteins derived from early and late viral strains to the rate of clearance, course of chronic disease, eventually the response to treatment, and, on the long run, to the incidence of hepatocellular carcinoma.
Knowledge of HCV diversity/polymorphisms as it is translated into viral fitness and pathogenesis, could guide introduction of early treatment, and predict treatment outcome. It will also be a helpful guide for immune prevention/therapy against more virulent HCV species.