Infectious Causes of Hepatitis Flashcards
1
Q
acute viral hepatitis presents with
A
- non-specific flu like symptoms
- jaundice
- dark urine
- pale faeces
2
Q
chronic viral hepatitis presents as
A
- general malaise
- cirrhosis, liver cancer
3
Q
early exposure to acute viral hepatitis (HAV, HEV) results in
A
- less severe acute disease (not mounting as strong an immune response)
- higher rates of chronic infection
4
Q
Hep A belongs to what family of viruses?
A
Picornaviridae (polio, rhinoviruses)
5
Q
What is the structure of HAV?
A
- non-enveloped - resistant to stomach acid, dessication, outside environements
- +ssRNA
- 30nm, 7500nt encode single polyprotein
- single serotype worldwide
- replicates in cell culture tf able to produce vaccines
6
Q
What is the HAV (+HEV) life cycle?
A
- transmitted from bile or faeces into food/water
- ingested
- replicates in intestinal epithelia
- travels through blood to liver
- replicates in liver
- gets into bile and faeces
7
Q
ALT indicates
A
presence of replicating virus
8
Q
How is acute viral hepatitis diagnosed?
A
- determine acute vs chronic/past
- serological tests (ELISA)
- IgM Ab to viral proteins (acute)
- reactive 1-2wks post-infection
- IgG Ab to viral proteins (convalescent)
- rising titre confirms acute
- IgM Ab to viral proteins (acute)
- NA tests (PCR) on blood/faeces (not as helpful with timing infection)
9
Q
What is the incubation period of HAV?
A
- Average: 30 days
- Range: 15-50 days
10
Q
HEV belongs to which family?
A
- Hepeviridae
11
Q
What is the structure of HEV?
A
- non-enveloped but more fragile than HAV (doesn’t survie environment as well)
- icosahedral
- 30nm (small, similar to HAV)
- +ssRNA (like HAV)
- 7.7kb (similar size to HAV)
12
Q
What is the incubation period of HEV?
A
- Average: 40 days
- Range: 2-10 weeks
13
Q
How is HEV diagnosed?
A
- serology - ELISA for IgM and IgG
- NA assays (PCR) of serum and faeces
- Immune EM
- recently cutltured in vitro - candidate for vaccines
14
Q
Which hepatitis virus has the highest risk of perinatal transmission?
A
HBV 30-50%
15
Q
What is the structure of HBV?
A
- double-walled:
- outer envelope
- inner capsid
- also exists as incomplete envelope-only particles that are non-infectious
- HBsAg only
- dsDNA with an incomplete segment
- carries DNApol and RNA primer
16
Q
How does HBV replicate?
A
- infects predominantly hepatocytes
- core enters nucleus and the ssDNA gap is ‘repaired’
- forms covalently closed circular DNA episome
- cccDNA acts as template for pregenome RNA
- encodes core, precore proteins and polymerase
- pregenome RNA form an encapsulated structure with polymerase
- reverse transcribed into DNA forming a new core particle
- DNA core particle can re-enter nucleus to amplify copies of ccDNA or assemble surface proteins via RER-golgi and bud off to infect
17
Q
What is the life cycle of HBV (and HDV and HVC)?
A
- transmitted by blood, semen, exudates, secretions
- sex, close contact, or injection
- penetrates mucosal epithelia
- finds its way into blood
- replicates in hepatocytes of liver
