pathophysiology of viral hepatitis (ninja nerd) Flashcards
What is meant by an ‘Acute Infection’ of hepatitis ?
The body can rid of the virus in <6months
What is meant by a ‘Chronic Infection’ of hepatitis ?
Lasts longer than 6months
Is Hep A an acute or chronic infection ?
Acute
How is Hep A transmitted ?
fecal-oral route
= patient ingested faeces of an infected person
What is the structure of Hep A virus like ?
- no envelope (no phospholipid bilayer surrounding the virus)
- capsid
- single stranded RNA
Is the RNA single or double stranded in the Hep A virus ?
Single stranded = SSRNA
Is Hep B an acute or chronic infection ?
Both
- starts acute
- can stay in liver and cause damage to liver cells for >6months
How is Hep B transmitted ?
- blood
- sex
- perinatal (to the foetus in utero)
What is the structure of Hep B virus like ?
- has an envelope (phospholipid bilayer)
- capsid
- partially double stranded DNA
Is the RNA single or double stranded in the Hep B virus ?
partially double stranded
Is Hep C an acute or chronic infection ?
Both
- starts acute
- can stay in liver and cause damage to liver cells for >6months
How is Hep C transmitted ?
- sex
- blood
- perinatal (to foetus in utero)
What is the structure of Hep C virus like ?
- has an envelope (phospholipid bilayer)
- capsid
- single stranded RNA
Is Hep D an acute or chronic infection ?
mainly a chronic infection
How is Hep D transmitted ?
- sex
- blood
- perinatal (to foetus in utero)
What is different about how Hep D infects the host ?
Hep D relies on Hep B
CO-INFECTION = Hep B and D infect at same time
SUPERINFECTION = Hep B infects, Hep D infects later
What are the 2 mechanisms of infection via Hep D ?
- co-infection (Hep B and D infect at same time)
- superinfection (Hep B infects first, Hep D infects later)
What is the structure of Hep D virus like ?
- has an envelope
- capsid
- circular single stranded RNA
Is a Hep E infection acute or chronic ?
mainly acute
can cause chronic but it is not very common
How is Hep E transmitted ?
Fecal-oral route
= someone ingests faecal matter of an infected person
What is the structure of Hep E virus like ?
- no envelope
- capsid
- single stranded RNA
Which is the only form of Hepatitis that contains DNA ?
Hep B
How do the ssRNA hepatitises (A, C, D, E) replicate themselves within the host ?
- uses host ribosomes for protein synthesis
- synthesises viral proteins e.g capsomeres to make the capsid, antigens, polymerase etc
- synthesised into new viruses by host golgi apparatus
- synthesised RNA polymerase formulates new RNA strands that combine with the viral proteins to form new viruses
How does the dsDNA hepatitis (Hep B) replicate itself within the host ?
- viral DNA released into nucleus of cell
- host RNA polymerase translates it into viral mRNA that leaves the nucleus
- host ribosomes perform protein synthesis using the viral mRNA
- synthesises viral proteins e.g capsomeres to make the capsid, antigens, polymerase etc
- synthesised into vesicles by host golgi apparatus
- synthesised viral RNA polymerase formulates new RNA strands
- RNA converted to DNA by reverse transcriptase
- vesicles and DNA combine to form new viruses
What happens when new hepatitis viruses accumulate within the cell ?
- death of the hepatocyte
How does accumulation of hepatitis viruses within a cell cause cell death ?
- Overload = Lysis
= accumulation causes lysis of the cell - Immune Response
= viral proteins interact with MHC-1 receptors on cell surface
= triggers Tcell response (CD8 Tcells)
= they recognise foreign antigen (viral protein)
= release perforins that perforate the cell membrane
= release granzymes that enter via perforations and trigger apoptosis
What do damaged hepatocytes secrete ?
Interferon Gamma (INF-γ)
= activates macrophages
What type of cell does INF-γ activate in response to heptocyte cell death ? What does this cell type do ?
INF-γ activates macrophages that stimulate CD8 Tcells to kill the infected cell
