Hepatitis C

Question 1

NANB

Answer 1

• Harvey J Alter
• lipid enveloped virus

Question 2

Approaches by Genelabs and Chiron to identify and isolate NANB virus

Answer 2

• Ab titer containing number of Abs w/ affinity for various viral Ags
• use liver tissue and plasma from infected chimp
• use human Abs to find viral proteins (Immunoscreening)

Question 3

HCV & HCC

Answer 3

• chronic infection
• liver disease: fibrosis, cirrhosis, HCC

HCC
- malignant tumour
- poor prognosis
- high levels of anti-HCV present
- genotype** 1b** have higher rates

Question 4

HCV & Anti-D immunoglobulin

Answer 4

• Anti-D used to treat Rhesus neg mother with Rhesus pos baby

Question 5

Most resistant genotype of HCV to therapy

Answer 5

Genotype 1a

Question 6

How does HCV enter?

Answer 6

• enters liver via hepatic artery and portal vein
  (vessels that transport blood to liver)

Question 7

Acute HCV

Answer 7

lasts from 0 to 24 wks
- often remains undetected

Question 8

CHC

Answer 8

Chronic hepatitis C
- 70% individuals develop this

Cirrhosis and hepatoceelular carcinoma - most common causes of mortality at end stage CHC

Question 9

Structure of HCV

Answer 9

• envelope proteins (contains lipid bilayer)
• positive ssRNA
• capsid (protects nucleic acid)

Question 10

HCV IRES

Answer 10

Internal Ribosomal Entry Site
- contains regions of dsRNA
- used by virus to bind to ribosomes and start translation

Question 11

HCV is a ….

Answer 11

Hepacivirus

Question 12

Where does HCV bind

Answer 12

binds to hepatocyte cell surface protein receptors and enters cell by receptor-mediated endocytosis

Question 13

HCV receptors

Answer 13

LDLRs on basolateral hepatocyte surface

Interacts with
- CD81
- tight junction proteins (claudins, CLDN1, OCLN)

Question 14

Where does HCV translation and replication begin

Answer 14

Cytosol

Question 15

Innate immunity receptors involved in HCV detection

Answer 15

TLR-7: detects HCV ssRNA
TLR-3: detects **dsRNA **
RIG-1: detects **ssRNA **in cytoplasm
PKR: detects dsRNA (IRES region)

detection leads to activation of TFs…
- NFkB
- IRF3
- IRF7

and subsequent production and secretion of cytokines and IFNs… (ANTI-VIRALS)
- IFN alpha
- IFN beta
- IFNλ

Question 16

HCV defenses

Answer 16

Sensing of HCV can activate innate antiviral defences through IFN induction in hepatocytes

Question 17

HCV control of IFN induction and immune evasion

Answer 17

NS3-NS4A (HCV protease)

• cleaves HCV polyprotein (liberates NS proteins)
• blocks RIG-1 by cleaving MAVS from intracellular membranes
• **Blocks TLR3 **by cleaving TRIF
• with E2 protien - both block PKR activity

NET result: suboptimal innate response

Question 18

Significance of cleaved MAVS

Answer 18

patients have lower IFNs

Question 19

IFN therapy

Answer 19

• variable
• many patients maintain high HCV viral load

Question 20

HCV genotypes

Answer 20

2 & 3: highest IFN-a treatment response rate (70-80%)
1 & 4: curative in 40-50% cases

Question 21

ISGs

Answer 21

IFN stimulated genes

• IFN induces expression of 100s of ISGs with antiviral and immunomodulatory activities
• genotypes 1 &4 have high levels of ISGs in patients liver before therapy (less effect IFN response)

Question 22

Are ISGs anti-viral?

Answer 22

No

Differential induction of specific ISGs in patients with different outcomes of HCV infection

Question 23

Treatment of chronic HCV with IFNs

Answer 23

Pegylated IFN-a combined w/ ribavirin for 24-48 wks

Question 24

Sustained Virologic Response

Answer 24

undetectable level of HCV RNA, 12 wks after end of therapy
- virological surrogate for clinical cure

Question 25

Ribavirin

Answer 25

a guanosine analog used to stop viral RNA synthesis

Question 26

Why are some outcomes resolved vs chronic

Answer 26

- HCV genotypes (1,4 not good) - role of host factor and genetics - IFNa S/E

Question 27

Genotypes 1 & 4

Answer 27

Cured with IFNs about 40-50% time

Question 28

Factors that influence therapy responses to pegylated IFN-a

Answer 28

- viral genotype (2,3 : better clinical outcome) - IFNλ3,4 genotypes *single NT polymorphism located upstream of IFNλ3 gene is predictive of HCV clearance *individuals woth IFNλ4 are associated with decreased clearance of HCV - role of MHC/HLA and HCV AP to T cells *some people inherit better MHC (more protection)

Question 29

Role of MHC/HLA and HCV AP to T cells in clearance of HCV

Answer 29

spontaneous clearance: HLA-B27, HLA-B57, HLA-A03

Question 30

HLA-B27

Answer 30

- immunodominant **HLA-B27-restricted virus specific CD8+ T cell epitopes** - escape from CD8 T cell response targeting this epitope is difficult - binding epitope located in conserved region of RNA dependant RNA polymerase **NS5B** (puts fitness contraints on HCVs) - high fitness cost; less likely to mutate *epitope conserved in HCV G1 but not G3 -> not protective in HCV G3 infection

Question 31

What dictates infection outcome

Answer 31

1. Host AP genes 2. HCV genotype

Question 32

First direct acting antiviral drugs

Answer 32

Telaprevir Boceprevir *HCV protease inhibitors

Question 33

IFN free Direct acting antiviral treatments

Answer 33

**HCV NS4A** interacts with HCV NS3 - NS3 is a protease and cleaves polyprotein **HCV NS5A** - interacts with multiple host cell and viral proteins **NS5A** - plays multiple roles in mediating viral replication, host cell interactions, viral pathogenesis **NS5B ** - RNA Polymerase****

Question 34

Targets for DAAs

Answer 34

1. NS3/NS4A protease 2. NS5B Polymerase 3. NS5A replication complex

Question 35

Simeprevir

Answer 35

PI - once daily dose - given with PEG-IFN + RBV

Question 36

Sofosbuvir

Answer 36

NS5B polymerase inhibitor *resistance barrier much higher compared to PIs

Question 37

Features of IFN-free DAA regimens

Answer 37

- 8 to 12 wks - excellent safetly profile - efficacy over 95%

Question 38

Pan-genotypic DAA therapies

Answer 38

Sofosbuvir NS5B Velpatasvir NS5A inhbitor

Question 39

What drug types offer exceptional SVR across all genotypes

Answer 39

NS5A NS5B inhibitors

Question 40

Most difficult genotype to treat with IFNs

Answer 40

G1