Hepatitis A and B

Dr. Amanj Saeed MBCHB, MSc, PhD [email protected]

Clinical Features of Viral Hepatitis

Preicteric Icteric Malaise Anorexia Nausea Abdominal discomfort Pyrexia (fever) Pale stool/dark urine Jaundice

Hepatitis A Virus

RNA genome, +ve single stranded RNA 7.5 kb in length encodes for polypeptides VP1, VP2, VP3, and VP4. Little is known about mechanism of entery Genome multiplication occurs in cytoplasm.

The genome can act as messenger RNA directly The incoming viral RNA strand directs the synthesis of a large viral polyprotein, which is then cleaved in to segments.

Hepatitis A Virus

Translation of RNA dependent RNA polymerase is crucial stem of viral life cycle. Initial step is viral RNA replication is to copy the incoming genome to form complementary negative strand. , which serves as a template for synthesis of positive genome RNA. The assembly is complex and require maturation cleavage of the structural proteins.

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Transmission and clinical

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manefestation

Faeco-oral route of transmission Entry via contaminated food or water Excreted in faeces Blood and blood products, needle, and sexual contact.

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The incubation period is 2-6 weeks.

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Many infections are silent

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Clinical features:

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Malase

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Loss of appetite

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Vague abdominal discomfort

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Fever

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Dark urine and pale faeces Jaundice (first in sclera and then skin)

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Itching in severe cases

Transmission and clinical manefestation

Hepatitis A is self limiting Recurrence is reported Less severe in children 1/1000 fulminant hepatitis (rare)

Pathology

HAV replicate in hepatocyte .

Shed in large quantities in the faeces

Hepatitis A Virus – Consequences of Infection

Asymptomatic infection Acute icteric hepatitis Fulminant hepatitis (rare) Necrosis of hepatocyte Proliferation of kupffer and other endothelial cells Elevated liver enzyme No chonicity, cirrhosis or malignant change

Immunity to HAV

Specific IgM in prodromal phase IgG neutralizing antibody is detectable for many years.

Diagnosis

Liver function test (raised serum Bilirubin and transaminases) Depressed prothrombin level Elisa for specific IgM

Immunisation

Human normal immunoglobulin Formalin inactivated vaccine.

HBV

350-360 million people chronically Infected worldwide.

Dandri and Stephen Locarnini, New insight in the pathobiology of hepatitis B virus infection, Gut, April 2012.

In europe 950 000 cases every year, 90 000 become carriers, 19 000 die of liver cirrhosis and 5000 die of liver cancer.

In US 200 000 new cases per year

Surface Ag

Hepatitis B Virus (HBV)

• Discovered in 1965 (Blumberg et al) • Hepadnavirus (DNA) Core Ag Also eAg DNA Source: Center for Disease Control and Prevention

The HBV genome

• Circular, partly double-stranded DNA • Minus strand of viral DNA is 3.2kb

• Plus strand is shorter and variable in size (1.8 to 2.7kb) • Very compact and contains 4 overlapping open reading frames (ORFs) • Upon entry into a liver cell, the viral core particle is translocated into the nucleus of the cell, the viral DNA is then repaired and matured by a virion DNA polymerase, giving rise to Covalently Closed Circular DNA (cccDNA)

Morphology

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Different shape

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Some are 42 nm in diameter and double shelled

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others are 20-22 nm in diameter.

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Complete virion some times called Dane particle The nucleocapsid contain: The DNA genome DNA dependent DNA polymerase HB core antigen (HBcAg) HB e antigen (HBeAg)

Genome

Compact genome Circular ds DNA 32 kbp in size 4 overlapping open reading frame ORF.

The virus encode 50% more protein than expected.

Replication

The virus attaches to hepatocyte using the virion S protein ( candidate receptors include transferrin receptor, the asialoglycoprotien receptor molecule, and human liver endonexin) The virus enters by endocytosis Virus nucleocapsid moves to the nucleus Enters cell as partially ds DNA 2 nd strand is completed

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covalently closed circular DNA (cccDNA) (mini chromosome) The minus strand is transcribed to give mRNA with a 3.4 kb RNA transcript called (pregenome)

Replication

Mode of genome replication is unusual include reverse transcription of DNA from RNA intermediate RT is lack of proofreading leading to high mutation rate.

Mutation occur is pre S region which is important for viral attachment and entry.

The new enveloped viruses emerge without cell lysis.

Use of Reverse Transcriptase

HBV DNA Translation mRNA

Viral proteins:

HBsAg HBcAg HBeAg Reverse Transcriptase

The main antigens

 HBsAg  HBcAg  HBeAg  Each HBV Ag stimulate corresponding antibodies  All HBV Ag and Ab (except HBcAg) together with the viral DNA polymerase can be detect in the blood at various times after infection.  HBc Ag can only be detected in the hepatocyte nuclei.

Subtypes and genotypes

    Surface antigen determine serological specificities to determine subtype of HBV.

DNA sequencing Genetic analysis revealed 7 genotype of the virus with %8 nucleotyde sequence difference differences Useful for epidemiological studies

Clinical presentation

Clinical features are variable and related to:  Age  Sex  State of immune system.

 Genotype of the virus

Natural History of HBV Infection - Adults subclinical hepatitis icteric hepatitis (jaundice) Acute infection fulminant hepatitis chronic infection (5-10%) healthy carrier chronic cirrhosis hepatitis Ca liver

Natural History of HBV Infection - Neonates subclinical hepatitis icteric hepatitis (jaundice) Acute infection fulminant hepatitis chronic infection (90%) healthy carrier chronic cirrhosis hepatitis Ca liver

Clinical features

Prodromal phase similar to that of HAV Rash and arthropathy Jaundice Chronic infection (5-10% in adults)

HBV antigen and antibody appearance

Increased serum amylase Detectible HBsAg Followed by appearance of HBeAg and DNA polymerase The first antibody to appear is anti- HBc Followed by appearance of anti-HBe (good prognostic sign) Anti HBs is the last antibody to appear and indicate full recovery and immunity to the virus.

Clinical outcome

1:1000 of case may develop fulminant hepatitis. 10 become chronic infection: chronic antigenaemia: patient fail to form anti HBs and delayed anti Hbe. HBsAg persist in blood, patient is well, liver function is normal.

Chronic active (aggressive) hepatitis: patient fail to produce anti HBs and anti Hbe, they carry HBsAg and infectious virion, become infectious to others, liver damage and impaired liver function, epesodes of hepatitis and eventually cirrhosis. HCC: occur as a result of integration of viral genome to the DNA of hepatocyte.

Hepatitis B Virus Modes of Transmission

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Perinatal

(mother to baby at the birth)

Sexual Parenteral

(unsafe injections and transfusion) •

Other body fuids??

Acute hepatitis B

HBsAg positive anti-HBc positive Acute infection will either resolve or become chronic

Resolved acute HBV infection

HBsAg disappears (may take up to 6 months Serum becomes positive for anti-HBc (IgG) - is therefore a marker of past infection anti-HBs - may also arise as a result of vaccination

Chronic HBV infection

Defined as persistence of HBsAg for > 6 months (i) HBeAg positive - high infectivity eg needlestick - increased risk of inflammatory liver disease (ii) Anti-HBe positive - low infectivity (but …..) - low risk of CLD (but ….)

Diagnosis

     ELISA Reverse passive haemagglutination Latex slide test Detection of viral DNA and DNA polymerase EM

Treatment

  Acute infection does not normally require treatment HBeAg positive carrier demand treatment    INF-α (6-10 MU three times weekly reduce viral load, HBsAg and HBeAg.

Lamivudine and Famciclovir adefovir

Prevention of HBV infection

Simple precautions Hepatitis B immunoglobulin (passive immunisation) Hepatitis B vaccine (active immunisation)

Immunisation

Vaccine (20 ug of HBsAg given IM at 0, 1, and 6 months. With booster dose at 5 year intervals for those at special risk Immunoglobulin

Who should be vaccinated?

Universal vaccination?

Selective vaccination?