Dr. Amanj SaeedMB.CH.B MSc PhD

Clinical virologist

Hepatitis C Virus (HCV)EnvelopeEnvelope

CoreCore

EnvelopeEnvelopeGlycoproteinsGlycoproteins Viral RNA (9400 nucleotides)Viral RNA (9400 nucleotides)

55-65 nm55-65 nm

• HCV is small enveloped positive sense RNA virus

• Belongs to Genus Hepacivirus of Flaviviridae family

• Genome is 9.6 kb.• 6 major genotypes.

HCVHepatitis C virus (HCV) is a small, enveloped

positive strand RNA virus belong to a genus Hepacivirus of the Flaviviridae family

An estimated 200?? million people worldwide are infected with HCV .

80% of infected individuals will develop chronic persistent infection, and of these 30% will develop progressive liver diseases including chronic hepatitis, cirrhosis and hepatocellular carcinoma (HCC).

HCVHCV infection has a major impact on public

health, yet no vaccine is available to prevent the infection and the antiviral therapies are characterised by:

limited efficacy high cost substantial side effects.

STRUCTURALGENES

NON-STRUCTURALGENES

+ ve ss RNA } Genomic organisation } FLAVIVIRUS

Core

5’UTR

E1 E2 P7 NS2 NS3

NS4A

NS4B NS5A NS5B

3’UTR

schematic representation of HCV genome

HCV– receptor interaction E1 and E2 are essential for host cell entry by

binding to receptors and inducing fusion of the host cell membrane

Several cell surface molecules have been proposed to play a role in mediating HCV attachment and entry:

the tetraspanin CD81 scavenger receptor class B type 1 (SRB1) heparin sulphate (HS) and the low density lipoprotein (LDL) receptor,

claudin-1 and occludin. Epidermal growth factor Receptor Ephrin receotor

Translation of HCV genome Translation of HCV genome yields a

polyprotein precursor that is subsequently processed by cellular and viral proteases.

Structural proteins include (core, E1, E2, P7)Nonstructural proteins include: NS2, NS3,

NS4A, NS4B, NS5A, NS5B.

HCV replication HCV Replication proceeds via formation of

complementary minus strand RNA using a viral genome as a template and subsequent synthesis of plus strand

Both these steps are dependent on NS5B (viral RNA Dependent RNA polymerase).

HCVHCV genome replication is associated with a

high mutation rate and sequence diversity which eventually results in a circulating population of diverse but closely related HCV variants, known as a quasispecies which underlies the following :

capacity to escape against immune responses

presence of multiple variants which facilitate the selection of adaptive mutations.

HCV genetic diversity: consequences

Diagnosismay result in false negativity

Pathogenicityare all genotypes equally dangerous?

Treatmentdo all genotypes respond equally to therapy?

Vaccine developmentcreates problems

Models for studying HCV pathogenesis

Analyzing the effect of HCV on transformed cell lines.

transgenic technology.Infection with related viruses (like GBV-B) The best model for HCV study is using

chimpanzees (economic and moral reasons limit the use of chimpanzee in research).

Models for studying HCV pathogenesisSub-genomic replicon systems .generation of an infectious clone of a

genotype 2 isolate of HCV known as JFH-1 which has the capacity to go through a full viral life cycle and produce infectious virus in hepatocyte derived cell lines.

Models for studying HCV pathogenesisHCV pseudoparticles (HCVpp).Recent studies developed an experimental

system to use primary human hepatocytes as a model for studying HCV pathogenesis

Anti-HCV POSITIVEEvidence of infection at some time

Gives no indication as to when infection occurred

Gives no indication as to whether infection was cleared or is still present

Anti-HCV: NegativeNo evidence of infection with HCV

BUT - be aware of possible false negatives

if infection very recent (window period)

if patient immunosuppressed at time of infection

Genome DetectionRequires amplification eg Reverse Transcriptase Polymerase Chain Reaction

Technically more exacting

Expensive

Interpretation RT/PCR results

POSITIVE

infectiousat risk of chronic

liver diseaserequires liver

biopsy

NEGATIVE

not infectious not at risk of chonic

liver diseasemay not require

biopsy

Hepatitis C virus: routes of transmissionParenteral

Injecting drug useBlood/blood productsOther needles Failure of infection control eg outbreaks (see

refs)Mother-to-baby (5%)Sexual (?real)

ACUTE INFECTIONUsually asymptomatic

CHRONICINFECTION 75-85%

InfectionResolved 15-25%

20 yrs

5 yrs

ASYMPTOMATIC, mild liver disease

CHRONIC INFLAMMATORY HEPATITUS

CIRRHOSIS eg 20%

HEPATOCELLULAR CARCINOMA

Chronic inflammation and the wound healing response are likely to be the framework within which HCV induces hepatic fibrosis

Natural history of Hepatitis C Infection

Infection by Hepatitis C Virus

Acute Hepatitis (>90 % Asymptomatic)

Chronic hepatitis(75-85%)

Cirrhosis(20%)

HCC

Spontaneous recovery(15-25%)

Chronic active(20%)

Asymptomatic(80%)

6 Mon

ths

10-30 Years

Transplantation

Hepatitis C

Treatment

Chronic infection – 80%

Clearance – 20%

Infection

Blood donors – anti-HCV

Organ and tissue donors – anti-HCV

Renal units – regular anti-HCV testing

Antenatal screening – NOT currently recommended

Infected patient healthcare worker

Infected healthcare worker patient

Surgeon-to-patient HCV transmission: phylogenetic evidence

2

Known transmissions from 5 surgeons (1 cardiac, 2 general, 2 O&G) thus far

Protection of patients:Guidelines??Known HCV RNA +ve HCWs – OUTCurrent HCWs doing EPPs encouraged to be

tested if risk factors .Needlestick injuries – early Rx benefit to HCWFor HCWs entering EPP-specialties – test for

HCV infection

Diagnosis Test for viral antigen and Antibody (ELISA)Test for genome (Quantitative RNA PCR)

Treatment Pegylated INF-α + Ribavirin