PHM142 Fall 2015
Coordinator: Dr. Jeffrey Henderson
Instructor: Dr. David Hampson
Biochemistry of
Hepatitis C
Lisa Liu, Anastasia Pimenova, Brittany Nicholls
Hepatitis C
1
liver disease caused by the Hepatitis C virus (HCV)
causes both acute and chronic infection
HCV caused by blood borne virus
blood-blood transmission
130-150 million people globally have chronic hepatitis
~240,000 individuals are infected in Canada
current drug treatment available
no vaccine available
Prognosis
1
Effects of Hepatitis C
1,2
gallbladder
impairment
HCV structure
3
single stranded RNA lipid and protein-enveloped virus of 9.6kb
http://viralzone.expasy.org/all_by_species/37.html
HCV Genomic/Proteomic Structure
3
RNA codes for 3 000
amino acid polyprotein
● 3 structural
proteins make the
envelope: capsid
and envelope
glycoproteins E1/E2
● non structural proteins for genome replication:
NS2, NS3, NS4A, NS4B, NS5A, NS5B
http://viralzone.expasy.org/all_by_species/37.html
Entry into Liver Endothelium
HCV Capture: 2 options
1. Via DC-SIGN. Paracellular
transport.
2. Via L-SIGN. Transcellular
transport.
4
Entry into Hepatocyte
3 steps:
1. Interaction with LDLR
2. Binding to SR-BI and
CD81
3. Use of CLDN-1 and
OCLN to result in
clathrin-mediated
endocytosis
4
HCV infection overview
● after capsid uncoating, RNA is
translated into protein at the rough ER
● proteins encoded by HCV make more
HCV RNA
● structural proteins (capsid, E1, E2) are
packaged and assembled in the Golgi
● capsid is assembled with RNA inside
and expelled by exocytosis
● virus can now infect other hepatocytes
5
Replication of HCV: Translation
5
5’UTR has internal ribosome entry site (IRES) that
facilitates hepatocytic 40s ribosome subunit binding
60s subunit recruited, can now translate
Role of HCV protein segments
5
HCV polyprotein cleaved by hepatocyte proteases into:
NS2, NS3 and NS4A: HCV proteases that cleave the
polyprotein
NS3: also acts as helicase, unwinds HCV RNA for replication
NS5B: RNA polymerase, makes +/- HCV RNA strands
NS4B: creates vesicles for viral assembly
Damage to hepatocytes
6
HCV is not directly cytopathic to hepatocytes
Immune mediated
subvert activity of NK cells, and CD4+ and
CD8+ T cells
HCV-specific T cells become unresponsive and
disappear
Many pathways are proposed and involve the
innate and adaptive immune responses
Damage to Hepatocytes via Cytokines
HCV core proteins and NS3 proteins trigger monocytes
and mast cells to release cytokines
IL1, IL6, IL8, TNF
Due to impaired immune system, cytokines are
continuously released
lead to hepatocyte damage, fibrogenesis and cirrhosis
via inflammation
6
Summary Slide
Single stranded RNA lipid and protein-enveloped virus of 9.6kb
Affects liver and causes liver damage
Structural proteins: E1, E2 and capsid, Non-structural
proteins:NS2, NS3, NS4A, NS4B, NS5A, NS5B
Entry via clathrin coated endocytosis
3 step process using LDLR, SR-BI, CD81, CLDN1, OCLN
Replication via non-structural proteins
Damage to liver via adaptive and innate immune responses
cytokines cause inflammation and cell death
References
1.
Webster DP, Klenerman P, Dusheiko GM. Hepatitis C. Lancet.
2015;385(9973):1124-35.
2. Li Y, Yamane D, Masaki T, Lemon SM. The yin and yang of hepatitis C: synthesis
and decay of hepatitis C virus RNA. Nat Rev Microbiol. 2015;13(9):544-58.
3. Budkowska A. Mechanism of cell infection with hepatitis C virus (HCV)--a new
paradigm in virus-cell interaction. Pol J Microbiol. 2009;58(2):93-8.
4. Lyu J, Imachi H, Fukunaga K, Yoshimoto T, Zhang H, Murao K. Roles of lipoprotein
receptors in the entry of hepatitis C virus. World J Hepatol. 2015;7(24):2535-42.
5. Tan S. Hepatitis C Viruses, Genomes and Molecular Biology. Horizon Scientific
Press; 2006.
6. Spengler U, Nattermann J. Immunopathogenesis in hepatitis C virus cirrhosis. Clin
Sci. 2007;112(3):141-55.