Viral Hepatitis Flashcards
What is the virus structure?
• are not able to replicate by themselves but require host cells and its cellular biochemical machinery to generate progeny • consist of DNA or RNA enclosed within a virus-encoded protein coat (nucleocapsid) and (sometimes) an outer-most host cell membrane-derived envelope • attach to host cell using receptorbinding proteins targeting host cell surface molecules that also serve as virus-specific receptors
What are the clinical symptoms of hepatitis?
- yellowing of skin and eyes (jaundice- increase bilirubin)
- dark urine
- clay-coloured stool
- nausea and vomiting
- loss of appetite
- fever
- abdominal pain
- weakness
What are the biochemical and serological tests for hepatitis?
• biochemical blood tests for hepatitis = liver enzymes (ALT, AST, ALP, GGT) = other liver proteins (e.g. albumin, prothrombin) = bilirubin (direct, indirect) • serological and molecular tests for viral hepatitis s - Enzyme Immunosorbent Assays (EIA) = Viral antigen = Anti-viral antibody - Molecular assays = PCR = Viral load - Sequencing = Genotype = Antiviral resistance • liver biopsy
Which hepatitis viruses are similar?
A and E (faecal, oral transmission)
B, C and D (parenteral, sexual)
Describe Hepatitis A Virus
• non-enveloped ss+ve RNA picornavirus
• at least 6 major genotypes, I-VI (type I is prevalent worldwide)
• incubation time is 10-50 days (avg 25-30 days)
• primarily children and young adults
• no seasonality (peaks may be seen in autumn)
• faecal-oral transmission
• abrupt onset, commonly with pyrexia
• resolves spontaneously (without chronicity – ie, no carrier
state) followed by life-long immunity
• fatality rate <0.5% in icteric cases (age dependent)
• inactivated virus vaccine (and immunoglobulin*) available
• treatment: supportive
Describe HAV transmission
- Sewage-contaminated water
- Shellfish filter off virus particles while feeding
- Shellfish harvested; eaten raw or partially cooked
- Virus ingested
What is the HAV Course of Infection?
- anti-HAV IgM in blood • IgM antibody to HAV • indicates recent HAV infection • persist for up to 4-6 months post infection - HAV RNA in blood • present at the onset of symptoms/signs - anti-HAV IgG in blood • IgG antibody to HAV • indicates HAV infection (or vaccine response) • detectable by onset of symptoms/signs • persists for life
Describe Viral Hepatitis Prevalence
A= Sub Saharan Africa, India, SE Asia B= Sub Saharan Africa, SE Asia, Russia C= anywhere, European and north American D= Europe, South America, Sub Saharan Africa E= higher distribution, E Europe, South France
What is the HAV outcome?
Children vs Adults =Subclinical infection= C 80-95%/ A 10-25% =Icteric disease= C 5-20%/ A 75-90% =Complete recovery= >98% both -No chronic disease =Fatality rate= C 0.1%/ A 0.3-2.1%
Describe Hepatitis B Virus
• Enveloped partially dsDNA hepadnavirus
• At least 8 main genotypes, A-H (type
A is prevalent in Europe)
• Incubation time is 40-180 days (avg 60-90 days)
• Primarily babies and young adults
• No seasonality
• Parenteral, vertical, sexual transmission (close contact)
• Insidious onset, sometimes apyrexial
• Virus remains in hepatocytes for life and may re-active under
immunosuppression (anti-HBcAb IgM may become detectable again)
• Chronic infection* (carrier state) develops in 5-10% of adults (but >95% of
neonates) and is associated with hepatocellular cancer
• Up to 2% fatality rate in icteric cases- liver failure
Describe HBV treatment
Recombinant HBV surface antigen vaccine (and immunoglobulin**) available
• Treatment (for chronic infection): Interferon alpha OR antivirals (eg, tenofovir,
entecavir); HBsAg seroconversion will occur in a small proportion of cases
treated with interferon alpha, but is even less likely to occur with antivirals;
however, antivirals are very effective in suppressing virus replication
(* Hepatitis B surface antigen-positive >6 months; ** Limited use)
Describe HBV structure
- Virion Dane particle
- Surface antigen= protein on envelope
- HB particles
Describe HBV Nomenclature
Hepatitis-B Surface Antigen (HBsAg)
• Found in HBV envelope
• Indicates active HBV infection
• Found in serum during acute and chronic (carrier state) infection
• Anti-HBsAg (antibody to HBsAg)
= Indicates past HBV infection or immune response to HBV vaccine
or passive antibody transferred following administration of HBV Ig
(HBIG)
Hepatitis-B Core Antigen (HBcAg) • Part of the HBV nucleocapsid • Anti-HBcAg IgM (IgM antibody to HBcAg) = Indicates recent HBV infection = Persists for 4-6 months post infection • Anti-HBcAg IgG (IgG antibody to HBcAg) = Indicates recent or past infection with HBV = Detectable by onset of acute symptoms and persists for life
Hepatitis-B E Antigen (HBeAg) • Associated with HBV nucleocapsid • Indicates active HBV infection • Anti-HBeAg (antibody to HBeAg) = Indicates HBV seroconversion
Describe HBV acute infection
Anti-HBc
-1 month= onset
Antibodies take time to develop-Surface antigen eliminated from blood when antibodies take over
E antigen= high viral load
Describe HBV chronic infection
-HBsAg
Surface antigen persists
Surface antibodies neutralise
