Flashcards in Hepatitis Viruses Deck (62):
What other viruses other than the hepatitis viruses cause acute hepatitis?
Herpes sSimplex Virus.
Yellow Fever Virus.
What are some common clinical features amongst the hepatitis viruses?
Nausea + emesis.
Right upper quadrant pain.
Raised liver enzymes like AST/ALT.
What kind of genome does hepatitis A have and is it an enveloped virus?
What does convalescence mean?
Refers to the time spent recovering from an illness or medical procedure.
What is the incubation period of hepatitis A?
3-5 weeks ~ 28 days
Is hepatitis A an acute or chronic disease?
No chronic form of the disease.
Convalescence may be prolonged (fatigue + alcohol intolerance up to 18 months).
Relate the severity of a hepatitis A infection to the age at which one acquires the virus.
Severe - adults and pregnant women
Mild or asymptomatic - children
What is a complication of hepatitis A infection? Who are at risk ?
Pregnant women, elderly, pre-existing liver disease.
Outline the pathogenesis of hepatitis A.
Virus enters gut > replicates in alimentary tract > replicates in liver > virus excreted in stools for 2 weeks preceding the onset of symptoms.
*viraemia is transient!
How is hepatitis A transmitted?
Faecal-oral route. *virus shed in stools for 2weeks before symptoms.
Shell-fish grown in sewage-polluted water.
How does one diagnose hepatitis A?
- HAV-specific IgM
Ways to prevent hepatitis A infection?
- recommended form of post-exposure prophylaxis
- normal Ig given
*in cases where risk for severe disease both are given.
Which antibodies fall/rise towards the end of the disease?
IgM falls (active immunity)
IgG rises (indicative of past exposure)
What kind of genome does HEV have and is it an enveloped virus?
What is the incubation period of HEV and how bad is the illness it causes?
2-9 weeks ~ 45 days
Usually acute self-limiting hepatitis.
Relate HEV infection to the age at which one normally acquires the virus.
Mostly young adults.
What are the complications of HEV infection?
Fulminant hepatitis (pregnant women greater risk).
Chronic hepatitis > cirrhosis (organ transplant/HIV infection).
Outline the pathogenesis of HEV infection.
Replicates in gut initially >replicates in liver > virus shed in stool prior to symptoms SIMILAR TO HAV
*viraemia is transient
*large innocuous required to establish infection
How is HEV spread?
Faecal-oral route. *contaminated water
Animals are reservoirs (pig, dog) *inadequately cooked meat
What pattern suggests that a large innocuous is required in order to establish a HEV infection?
Case-to-case transmission is low therefore suggests large innocuous required.
What specimens can be sent to the lab to test for HEV infection?
Stools and serum.
How does one test for HEV infection? Which tests are available here in SA?
1. Virus particles in stools (electron microscopy)
2. IgM in serum
3. PCR for HEV genome in stool or serum
*none available for routine test in SA
What kind of genomic material does HBV have and is the virion enveloped?
Circular DNA (incompletely double-stranded)
What is the incubation period of HBV?
Onset of symptoms is insidious.
Which tends to cause more severe disease between HAV and HBV?
Relate the age of infection with HBV and the likeliness of subsequent chronic illness.
5% of adults develop chronic infection.
90% of infants vertically infected develop chronic infection.
Why is it that infants develop chronic infection with HBV?
Very young develop immunotolerance > lesser immune response
*less inflammation of liver but higher rate of chronicity as a result
How is HBV transmitted?
What does parenternal mean?
Administered or occurring elsewhere in the body than the mouth and alimentary canal.
Outline the pathogenesis of HBV.
Virus replicates in liver > viraemia prolonged therefore blood highly infectious
What is one way HBV visions avoid destruction by the immune system?
Excess viral surface antigen is produced (form sphere and cylinders) that bind to antibodies, mopping them up.
What is responsible for hepatocellular damage in HBV infection?
Host immune response.
Name 5 complications of HBV infection.
Fulminant hepatitis. (Rare)
Extra hepatic manifestations.
Co-infection with HIV (faster progression + severe liver damage)
Name three extra-hepatic manifestations of HBV.
*caused by deposition of immune complexes
What forms of persistent infection with HBV are there?
Chronic persistent hepatitis:
- virus persists/minimal liver damage
Chronic active hepatitis:
- aggressive destruction of liver tissue > rapid progression to cirrhosis + liver failure.
What is polyarteritis nodosa?
Vascular is of medium/small-sized arteries > become swollen + damaged from attack by rogue immune cells.
How is HBV transmitted?
Close personal contact (horizontal spread).
What is a feature of the enzymes coded for by HBV?
HBV polymerase has DNA polymerase and reverse transcriptase activity.
What can HBV vaccines contain?
Purified serum-derived sAg from HBV carriers.
Recombinat sAg via genetic engineering of yeasts.
When do infants receive HBV vaccinations in SA?
6,10 and 14 weeks.
If mum is a chronic carrier then at:
- birth, 1m and 6m (additional dose at 2m if baby <2kg)
What can one give to a person as a form of post-exposure prophylaxis for HBV?
Vaccine + HBV Ig
What two classes of drugs are used to treat chronic HBV infection.
Nucleoside reverse transcriptase inhibitors.
What does interferon-alpha do in the chronically HBV infected individual.
Enhances the host immune response to HBV and improves immune control of the virus.
What two common nucleoside reverse transcriptase inhibitors are used to treat chronic HBV infection? What do they do?
Tenofovir and Lamividine.
They interfere with viral replication but CANNOT CLEAR HBV INFECTION!!!
Which HBV viral surface antigens can be detected and what is each a a marker of?
sAg - viral replication in liver (secreted in excess)
eAg - indicative of high replication rates in liver
cAg - present in infected cells not in blood
What surface antibodies can be detected against HBV and what is each indicative of?
sAb - indicates immunity (found in late convalescence)
eAb - indicates low infectivity (detectable as viral replication falls)
cIgM - indicates recent infection
cIgG - indicates exposure to HBV
Which antibodies to HBV are found in chronic carriers and which aren't?
sAb - not found in chronic carriers
cIgG - found in chronic carriers (also those who clear the infection)
Genome of HCV and is it enveloped?
Incubation period of HCV?
How may a case of HCV present?
Some: fatigue + jaundice.
What is a feature of HCV genome?
Genome has a high mutation rate.
Can HCV cause chronic infection?
80% of newly infected individuals develop chronic infection.
Complications of HCV infection?
1. Chronic infection > cirrhosis
2. HCC in 1-5% of HCV infected people
3. Immune complex disorders
4. Co-infection with HIV > aggressive liver disease
5. Extra hepatic manifestations
Transmission of HCV?
- vertical transmission and sexual intercourse (minor roles)
How to diagnose HCV?
- IgG indicates exposure > useful for diagnosing chronic infections
- HCV genome detectable in serum 4-6 weeks post-exposure
- indicative of infectivity
How to treat a chronic HCV infection?
Interferon-alpha + ribavirin = clearance in ~40% of cases
Vaccine for HCV?
What is HDV?
A defective virus that requires HBV as a helper virus in order to replicate.
Two forms of HDV infection?
- HBV and HDV at same time
- HDV after HBV infection
How does HDV infection impact HBV infection?
Increases severity of liver disease.
Fulminant hepatitis 10X more common in co-infection that sole HBV infection.
70-80% chance of cirrhosis if co-infected.
Genome of HDV and why does it need HBV to replicate?
sAg derived from HBV