HCV Pathogenicity

Question 1

Hepatocellular Carcinoma

How common?

Answer 1

Is 5th most common cancer in males and 8th in females
>500,000 cases per anum with 70% associated with HBV/HCV

Very aggressive with poor prognosis

Question 2

Therapy for HCC

Answer 2

Only reliable therapy is resection/transplantation

Question 3

Development of HCC

Factors that’s increase chance of HCV

Answer 3

Hepatocytes are present predominantly in G0 phase and don’t cycle, thus have a very high metabolic activity

Liver has a high propensity for regeneration- can regenerate 90% loss

Increase chance
Chronic liver injury
Inflammation
Increased cell turnover
Oxidative DNA damage

Question 4

Molecular requirements for development of HCC

Answer 4

5 main

P53- skewed to decrease apoptosis

TGFbeta- skewed to decrease apoptosis and increase cell cycle progression

Rb-skewed to increase cell cycle progression

Growth factors- skewed to promote cell cycle progression and vascularisation

Wnt/ Beta-catenin - skewed to increase gene expression, to mediate increased cell adhesion and proliferation

Evidence HCV effects all these pathways

Question 5

How does HCV affect pathways that promote HCC

Answer 5

In vitro evidence

NS5A affects p53/TGFbeta/ growth factor/ wnt/ beta-cafe in signalling

Core affects p53 and TGFbeta signalling

NS5B affects p53/Rb signalling

NS3 affects p53 signalling

Question 6

Why does HCC take 30 years to develop if HCV subverts necessary pathways

Answer 6

Lack of additional factors
HCV only one factor
HCV isn’t cause but factor

Question 7

Issues with Huh7 cells

Answer 7

Issue studying link between HCV and HCV with Huh7 cells is that they are derived from hepatoma, this they are already transformed thus don’t represent a good model

• Y220 loss of function mutation in p53
• Lack of p21 to regulate p53
• high level of GSK3beta phosphorylation - high levels of beta-cage in

Question 8

HCV and insulin resistance ?

Answer 8

Natively insulin binding to InsR stimulate glycogen synthesis and decreases gluconeogenesis

HCV disturbs this by interfering with IC signalling and stimulate IL-18/TNFalpha production

• HCV appears to develop hepatic insulin resistance
• results in metabolic syndrome
• IL-18/TNFalpha promote peripheral insulin resistance in skeletal muscle
• peripheral insulin resistance +metabolic syndrome + host genetics come together to induce whole body insulin resistance

Question 9

Whole body insulin resistance is associated with

Answer 9

Accelerated fibroogenesis

Increased incidence of HCC

Type 2 diabetes

Reduced antiviral response

Question 10

HCV and lipid metabolism

Answer 10

Core proteins shown to associate with lipid droplets,
Infection induces lipid accumulation

Lipogenesis of lipids needed for

• as substrate for fatty acid oxidation in mitochondria
• formation of cellular membranes
• secretion as lipoprotein secretions,being released into EC medium

HCV shown to block lipoprotein secretion, increase lipogenesis and abrogate fatty acid degradation/oxidation to a high degree- increased IC conc of lipids

Question 11

Effect of HCV on energy

Answer 11

Inhibits AMPK which increases lipid conc necessary for viral replication

AMPK means AMP kinase is hydrolyses to turn on energy production and switches of energy usage reducing and reduces cholesterol synthesis

Hypothesised diabetes type 2 drugs could trea HCV but didn’t work

Question 12

IFN therapy of HCV

Answer 12

Combination therapy consists of IFNalpha and Ribavirin
-IFNalpha is pegylated or conjugated to albumin which have much longer half life

• IFNalpha activated the cellular IFN-mediated antiviral responses
• Ribavirin is a broad range antiviral

Treatment consists of a weekly dose of PEG-IFN / Alb-IFN (1.5ug/kg) by subcutaneous injection + a daily dose of 800-1400 mg Ribavirin administered orally

Question 13

Problems with IFN therapy

Answer 13

Response rate of IFN based therapy varies with genotype

1,4,5,6 48 weeks of therapy 40-50% work
2,4 24 weeks of therapy 80% work

High proportion of non-responders
-50% of responders relapse after cessation of the therapy

Side effects are severe and people often stop taking drug

• IFN- neutrophilia/haemophilia/thrombocytopenia - fatigue+nausea
• Ribavirin can lead to anaemia

Costs approximately 11k for 48 weeks for therapy

Question 14

Cyclophilin A

Answer 14

CypA is a peptidyl-prolyl isomerase, that catalyses the cis-trans isomerisation of Pro residues and has been shown to be required for HCV RNA replication
-it binds to NS5A and NS5B - may be required because NS5A is rich in pro

Cyclosporin A (CsA), an 11 aa peptide that is a fungal metabolite, works effectively to block cyclophillin A function- usually and immunosuppressant

• developed derivatives (Alisporivir) that lack immunosuppressive activity which worked in vitro and in clinical trials
• but not well enough to warrant use compared to newer drugs

Question 15

miRNA 122

Answer 15

2 copies of miRNA 122 binds to the 5’UTR of HCV at 3 sites

• 1 binds 2 sequences spanning the 5’-most stem loop
• the other binds at a seq downstream of stem loop

miR-122 is liver-specific miRNA, making up 70% of all miRNA in hepatocytes, regulating genes associated with cholesterol metabolisim + Fe homeostasis

Low levels of of miR-122 observed in HCC and shown to be required for HCV RNA replication

Developed as RNA oligonucleotides complementary to miR-122
-these were locked nucleic acid Oligos, where a 2’-O-methyl modification made them resistant to nuclease activity

Abandoned due to development of newer drugs