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Hepatitis Viruses

Hepatitis Viruses. Fe A. Bartolome, MD Department of Microbiology Our Lady of Fatima University. HEPATITIS A. infectious hepatitis; Enterovirus 72 Picornavirus genus Heparnavirus/Hepatovirus naked, icosahedral symmetry positive sense, ssRNA virus with a VPg protein attached to 5” end

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Hepatitis Viruses

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  1. Hepatitis Viruses Fe A. Bartolome, MD Department of Microbiology Our Lady of Fatima University

  2. HEPATITIS A • infectious hepatitis; Enterovirus 72 • Picornavirus genus Heparnavirus/Hepatovirus • naked, icosahedral symmetry • positive sense, ssRNA virus • with a VPg protein attached to 5” end • replication similar to other Picornaviruses • not cytolytic • released by exocytosis

  3. HEPATITIS A • Characteristics: • Stable to: acid (pH 1), solvents (ether, chloroform), detergents, salt/ground water, drying, temperature (40C – 560C) • Inactivated by: chlorine treatment, formalin, UV radiation

  4. HEPATITIS A • Pathogenesis: • MOT: fecal-oral  food (shellfish – clams, oysters, mussels); water; dirty hands • Ingestion  oropharynx or epithelial lining of intestines  blood stream  liver (hepatocytes and Kupffer cells)  bile  stool • Virus shedding: 2-3 wks before & 1 week after onset of jaundice or until antibody is detected • Interferon – limits viral shedding • NK cells & cytotoxic T cells  lysis of infected cells • Antibody, complement, ADCC  induce immunopathology

  5. HEPATITIS A • Pathogenesis: • MOT: fecal-oral  food (shellfish – clams, oysters, mussels); water; dirty hands • Ingestion  oropharynx or epithelial lining of intestines  blood stream  liver (hepatocytes and Kupffer cells)  bile  stool • Virus shedding: 2-3 wks before & 1 week after onset of jaundice or until antibody is detected • Interferon – limits viral shedding • NK cells & cytotoxic T cells  lysis of infected cells • Antibody, complement, ADCC  induce immunopathology

  6. HEPATITIS A • Epidemiology: • 90% of infected children & 20-25% of infected adults with inapparent but productive infections • HAV viremia transient  blood-borne transmission rare

  7. HEPATITIS A • Clinical Syndromes: • Children: mild infection, usually asymptomatic • Adults: abrupt onset of symptoms • viral shedding precedes onset of symptoms • complete recovery in 99% • fulminant hepatitis: 1-3 persons/1000 with 80% mortality • immune complex-related symptoms rare

  8. HEPATITIS A • Laboratory Diagnosis: • ELISA or radioimmunoassay • (+) IgM anti-HAV  acute infection  fecal shedding decreases as IgM titer increases • (+) IgG anti-HAV  resolution, past infection • Prophylaxis: immune serum globulin < 2 wks after exposure

  9. HEPATITIS B • serum hepatitis • Hepadnavirus • infects liver, kidneys and pancreas  humans and chimpanzees • 15% of population infected during birth or childhood • small, enveloped • circular, partly ds DNA virus • mature virion  Dane particle

  10. HEPATITIS B • Important proteins: • DNA polymerase – with reverse transcriptase & ribonuclease H activity • HBcAg – core antigen; surrounds polymerase; T cell antigens • HBeAg – minor component of virion; primarily secreted into serum • HBsAg – surface antigen; Australia antigen • HBx – transcriptional transactivator; promote viral replication; protein kinase

  11. HEPATITIS B • HBsAg with 3 glycoproteins encoded by same gene but translated from different AUG start codons • S (gp27) – contained in M glycoprotein; major component of HBsAg • M (gp36) – contained in the L glycoprotein • L (gp42) – essential for virion assembly

  12. HEPATITIS B • Replication unique: • With distinctly defined tropism for liver • Small genome  economy in transcription and translation • Replicates through an RNA intermediate • Binds to human serum albumin  target the virus to the liver • Cell penetration  partial DNA strand converted to complete dsDNA  nucleus

  13. HEPATITIS B • two phases of hepatocyte infection: • Proliferative phase • HBV DNA present in episomal form • Viral HBsAg & HBcAg + MHC class I molecules  activation of CD8+ T cells  (+) hepatocyte destruction • Integrative phase • For hepatocytes not destroyed by immune system  viral DNA incorporated into host genome

  14. HEPATITIS B • (+) HBsAg and HBeAg in blood  on-going active infection • MOT: • Blood & other body fluids – semen, saliva, milk, vaginal secretions, amniotic fluid • Sexual contact • Perinatal – passage through birth canal • Intracellular accumulation of filamentous forms of HBsAg  responsible for characteristic ground glass cytopathology

  15. HEPATITIS B • CMI + inflammation  responsible for causing symptoms; eliminate infected hepatocytes • Immune complexes between HBsAg and anti-HBs  (+) type III HS reaction  vasculitis, arthralgia, rash, renal damage • Infants & young children  immarture CMI  less ability to resolve infection  90% chronic carriers

  16. Ab Immune complex Type III HS HBsAg Symptoms, resolution Liver Viremia CMI Ab Prevent spread & disease MOT Blood HEPATITIS B • Spread of Hepatitis B

  17. Acute Hepatitis B 90% 1% 9% Resolution Fulminant HBsAg+ > 6 months 50% Asymptomatic carrier state Chronic persistent hepatitis Chronic active hepatitis Resolution Extrahepatic disease: PAN, GN HCC Cirrhosis HEPATITIS B • Clinical outcomes:

  18. HEPATITIS B • Laboratory: • Detection of HBeAg is the best correlate to the presence of infectious virus • Chronic infection  continued finding of HBeAg, HBsAg or both without detectable antibodies

  19. HEPATITIS B Interpretation of Serologic Markers of HBV Infection

  20. HEPATITIS C • NANB post-transfusion hepatitis • Flavivirus genus Hepacivirus • Enveloped, ss positive sense RNA virus • 5’ end encodes nucleocapsid core protein  highly conserved • Envelope proteins  E1 and E2 • Hypervariable regions (HVR1 & 2)  present in E2 sequence • Non-structural proteins (e.g. NS5B  viral RNA-dependent RNA polymerase)  with poor fidelity

  21. HEPATITIS C • Infects only humans and chimpanzees • Binds to cells with CD81 surface receptors OR coats itself with LDL or VLDL & uses their receptors for uptake into hepatocytes • Inhibit apoptosis & IFN- by binding to TNFR and protein kinase R (PKR)  prevent death of host cell and promote persistent infection • CMI  production of tissue damage • Antibody not protective

  22. HEPATITIS C • Remains cell-associated • MOT: • Parenteral - >90% of HIV (+) individuals infected with HCV • Secretions • Sexual • Perinatal (6%) • PERSISTENT INFECTION AND CHRONIC HEPATITIS ARE THE HALLMARKS!

  23. HCV Acute infection Recovery & clearance Persistent infection Chronic hepatitis Liver failure Cirrhosis HCC HEPATITIS C • Outcomes:

  24. HEPATITIS C • Laboratory: • (+) anti-HCV antibodies (50-70%) in symptomatic acute infection • HCV RNA persists despite presence of neutralizing antibodies (90%) • Episodic elevation of serum aminotransferases • Treatment: IFN- alone or with ribavirin – only known treatment

  25. HEPATITIS D • Delta hepatitis; viroid-like • Replication defective  viral parasite • Enveloped, circular RNA virus  surrounded by delta antigen core  surrounded by HBsAg-containing envelope • Unusual transcription and replication process • Host cell RNA pol II  makes RNA copy  replicates genome  makes mRNA  form a ribozyme  cleave RNA circle  form mRNA

  26. HEPATITIS D • MOT similar to HBV • Replicate and cause disease only in people with active HBV infection  results in cytotoxicity and liver damage • With direct cytopathic effect

  27. HEPATITIS D • Clinical outcomes: Co-infection HDV + HBV Healthy individual rare 3-4% 90% Recovery w/ immunity Chronic HBV/HDV hepatitis Fulminant hepatitis Death Cirrhosis

  28. HDV HBV carrier 80% 7-10% 10-15% Acute, severe disease Chronic HBV/HDV hepatitis Fulminant hepatitis Death Recovery Cirrhosis HEPATITIS D • Clinical outcomes: Superinfection

  29. HEPATITIS E • Enteric or epidemic NANB hepatitis • MOT: fecal-oral • Resembles Calicivirus or Norwalk agent in size and structure  non-enveloped, ssRNA virus • Symptoms and course similar to HAV • Causes only acute disease • Poor response to serum IgG • Infection serious in pregnant women  mortality approx. 20%

  30. HEPATITIS G • Flavivirus similar to HCV • MOT: contaminated blood or blood products; possibly sexual • In 75% of infection  HGV cleared from plasma; 25% become chronic • Site of replication: mononuclear cells  not hepatotropic • Does not cause elevation in serum aminotransferases • With protective effect on patients co-infected with HIV  inhibit HIV replication in cultures of peripheral blood mononuclear cells

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