Hepatitis C in Australia: Epidemiology and Clinical Presentation (and a bit of virology ) A/Prof Mark Douglas
Hepatitis C - Distribution Te and Jensen 2010 Clin Liver Dis
Hepatitis C Epidemiology Estimated global prevalence of HCV infection 3% (170 million) in 1999 (WHO) Africa 5.3% (31.9 million) Eastern Mediterranean 4.6% (21.3 million) South-East Asia 2.15% (32.3 million) Western Pacific 3.9% (62.2 million) Americas 1.7% (13.1 million) Europe 1.03% (8.9 million) Wide variation Egypt 15-20% Scandinavia 0.01 to 0.1%
Hepatitis C Disease Burden HCV estimated to be the cause of 27% of cirrhosis and 25% of HCC worldwide Main cause of cirrhosis requiring liver transplant: Australia, USA, UK Prevalence in Australia 1% Causes more deaths than HIV in Australia and USA
Hepatitis C - Transmission Source human blood blood contaminated body fluids Route inoculation Sexual transmission rare, but reported (well described in HIV +ve MSM) vertical transmission 5% (at birth)
Mode of HCV Transmission INDUSTRIALISED COUNTRIES OTHER COUNTRIES ++++ IV DRUG USE + ++ TRANSFUSION BEFORE 1990 ++ + BORN TO VIRAEMIC MOTHER + + NON-MEDICAL PROCEDURES ++ + NOSOCOMIAL ++++
HCV Genetic Variation Genotypes (1-6) Pattern of nucleotide sequence across entire genome Variation > 30% between genotypes Subtypes (1a, 1b etc) vary 20-25% Breeds true on transmission Geographical distribution (adapt to population) Quasispecies Sequence variation in particular domains (up to 10%) Evolve within a single patient over time, in part to immune pressure and selection Hyper-variable region, envelope glycoproteins E1, E2
Global Distribution of HCV Genotypes 1a, 1b, 2 1,2,3 1b 4a 4 4 1a 1b,3 3 6 1b 6 1,2 1b 1b 5a 1c,3 1,3 Webster et al.,2000 Genotypes 1-3 Worldwide Genotypes 4 & 5 Africa Genotype 6 Asia
Typical Course of HCV Infection Minor (anicteric) acute illness 20-40% virus clearance 60-80% chronic viral replication Chronic HCV 20-30% no evidence of disease 60-80% chronically elevated LFTs 3-9% develop cirrhosis over 20-30y HCC 1-3% per year once cirrhotic
Serum markers of Hepatitis C
Diagnosis of HCV Infection Anti-HCV antibodies, antigen (ELISA) Detect HCV RNA by RT-PCR Quantitative PCR, genotype Disease LFTs (especially ALT) Liver biopsy (Fibroscan) HCC screen (ultrasound, AFP)
Hepatitis C - Control Screening blood products for HCV Available since 1990 Voluntary unpaid blood donation preferable to paid donations Needle syringe programs
Hepatitis C Virus Shimizu et al., 1996 Positive single strand RNA virus Flaviviridae family, Hepacivirus genus 9.6 kbp genome ~3000 amino acid polyprotein 60 nm enveloped virions Lipo-viral particles Until recently, unable to grow in cell culture
Features of the HCV Genome cellular proteases viral proteases core E1 E2 NS2 NS3 NS4B NS5A NS5B Structural proteins P7 NS4A Non-structural proteins Core (capsid) E1 and E2 (envelope glycoproteins)
HCV Proteins Core Highly basic core protein E1*gp31 Envelope glycoprotein, heterodimer in virion E2* gp70 Envelope glycoprotein, heterodimer in virion p7 Cleaved from E2, behaves as ion channel NS2 Serine protease (NS2/3) NS3 serine protease, helicase and NTPase activities NS4A cofactor essential for NS3 serine protease activity NS4B induces a membranous replication complex at the ER NS5A RNA binding, replication complex, regulate life cycle NS5B RNA Polymerase (RNA dependent)
HCV Proteins - ER Membrane Associations Moradpour et al, 2007
HCV Life Cycle Cytoplasmic replication Replication complexes at ER Membranous web induced by NS4B Moradpour et al, 2007
HCV Binding and entry Circulate in vivo as lipoviral particles Use lipoprotein receptors Essential receptors: CD81 Scavenger receptor SR-B1 Claudin-I (Evans, 2007) Occludin (Ploss, 2009) EGFR (Lupberger, 2011) Pietschmann 2009. Nature
HCV Replication Moradpour et al, 2007 Replication in hepatocytes PBMC as well? Animal models Chimpanzee Humanised chimeric mice In vitro models: Subgenomic replicons JFH-1 cell culture model NS5B - RNA polymerase RNA replication, membrane protected replication complexes at the ER
HCV replication & lipids Lipid droplets important for virus production (Miyanari 2007) Core protein associates with lipid droplets (stop association blocks virus production) NS5A colocalises with core on LDs Virus assembly occurs at LD-ER interface Inhibiting fatty acid synthase inhibits virus replication (Su 2002; Yang 2008) HCV causes steatosis (fatty liver), insulin resistance and Type 2 Diabetes Cholesterol metabolism key for HCV replication
Immune Response to HCV Non-Specific (Innate) Immunity Cell senses viral proteins, RNA (RIG-I, TLR3) Type I, III interferon (IFN) response NK cells Specific (Acquired) Immunity Humoral (antibodies to HCV proteins) Cell mediated (cytotoxic T lymphocytes) No protective immunity Some Auto-immunity Extra-hepatic manifestations of HCV
Evolution of Quasispecies Immune Escape
Hepatitis C Treatment Outcomes
Evolution of SVR rates 1989 1995 (2000) 1998 2001 SVR (%) G1 G2/3 G1 G2/3 100 80 61-79 76-82 60 40 ALL ALL 18-39 35-43 ALL 33-36 42-46 20 6-19 11-19 10-22 0 24 48 78 Peg-IFN IFN + weeks RBV IFN monotherapy PEG + RBV *Range of values reported; lower bar represents lower value Manns, Foster et al., Nature Reviews Drug Discovery 2007
Potential New Drug Targets Pockros, PJ (2010, Therap Adv Gastro, 3:191 202)
Direct Acting Antivirals (DAAs) NS3/4A protease inhibitors telaprevir, boceprevir, simeprevir, paretaprevir NS5B polymerase inhibitors Nucleos(t)ide analogues (sofosbuvir) Non-nucleoside analogues (dasabuvir) NS5A inhib. (daclatasvir, ledipasvir, ombitasvir) Rosen, H. R. (2011, NEJM, 364:2429 2438)