Hepatitis B Flashcards
What is the important difference between HBV compared with HAV and HEV?
HBV can lead a chronic infection and be a risk factor for cirrhosis and cancer whereas HAV and HEV are only really associated with acute infections
It is also a DNA virus NOT a RNA virus
I.e. only hepatitis virus which is DNA virus
What are the differences between endemic and sporadic HBV?
Endemic:
- associated with chronic Hep B
- has high prevalence (China/Sub-saharan africa/indian subcontinent)
- Vertical transmission and horizontal in childhood
Sporadic:
- associated with acute Hep B
- low incidence
- sexual and IVDU transmission
Which populations should be screened for HBV?
What does this screening process use to identify those with HBV?
Blood and organ donors Healthcare workers Pregnant women Dialysis patients GUM clinic attendee IVDU/prisoners People from country with intermediate-> high prevalence of chronic hep B
Looks for HBV surface antigen HBsAg (envelope protein)
I.e. will be presented on surface of infected hepatocytes
What are the main structural components of HBV virus and how does it enter and replicate in host cell?
(From outside in)
- HBV surface antigen (HBsAg)
- HBV core antigen
- HBV DNA (located within HBV core)
- HBV polyermase (located withinth HBV core)
Enters cell
Host polymerase transcribes HBV DNA to mRNA
MRNA enters host ribosome to undergo translation to form new viral proteins
Some of viral mRNA transcribed back into viral DNA vua viral polymerase in order to assembly new virus
What is the mechanism behind liver damage due to HBV?
Damage is immune-mediated (not due to infection or replication):
-immune-mediated response leads to TC killing infect cells and macrophages and NK cells causing direct or indirect cytolysis
I.e. response and associated inflammation-> scarring
How does the form of transmition change with the age of infection?
Neonate:
-vertical i.e. mum to baby
Toddler
-Horizontal i.e. close contact
Adult
-sexual
What is the natural history of a vertical infection of HBV?
What are the consequences?
95% of those being infected vertically with HBV with develop chronic hepatitis Leads to development of cirrhosis Once reached cirrhosis stage at risk of: -liver failire + decompensation -liver cancer -death
5%= HBV resolves and are immune
How can you differentiate between a HBV chronic hepatitis and cirrhosis with serology
Chronic hepatitis:
- HBsAg +ve
- HBeAg +ve/-ve
- high HBV titre
Cirrhosis
- HBsAg +ve
- HBeAg -ve
- low HBV titre
What are the main methods of transmission of HBV?
Blood or bodily fluids
- sexual intercourse
- IVDU or tattoos
- sharing contaminated toothbrush
- vertical from mother to childs
What are the 2 main outcomes of being infected with HBV?
Fully recoved within 2 months
10% become chronic carriers
What does it mean when someone is a chronic Hep B carrier?
Means the virus has intergrated into DNA and viral proteins are continuing to be produced
What are the 5 main viral markers associated with HBV?
What does the presence of these markers indicate?
Surface antigen (HBsAg)
- active infection
- also associated with vaccination
E antigen (HBeAg)
- marker of viral replication -> implies high infectivity
- presence indicates patient in acute phase of infection i.e. virus actively replicating
Core antibodies (HBcAb) -implies past or acute vs chronic infection
Surface antibodies (HBsAb)
- implies vaccination or past/current infection
- indicates there has been an immune response to HBsAg (could be positive for those been vaccinated or those who have been infected so need to do further testes to determien the difference)
Hepatitis B virus DNA (HBV DNA)
-direct count of viral load
What is included in a viral screen for Hep B and how would you interpret a positive result for these markers?
HBcAb-> looking for previous infection
HBsAg-> looking for active infection
If positive need to test for
- HBeAg= gives a marker of viral replication and indicates person high infective
- HBV DNA= indicates the viral load
What can HBcAb due used to distinguish between?
Between acute, chronic and past infections by measuring IgM and IgG versions of HBcAb
IgM:
-implies active infection
high titre =active infection
low titre =chronic infection
IgG:
-implies past infection when HBsAg negative
What does a positive HBeAg mean?
What does a negative HBeAg with positive HBeAb?
+ve HBeAg:
- actively replicating HBV
- higher the HBeAg the more highly infectious a person is
Person been through the acute replication phase of viral infection but virus has now stopped replicating meaning they are less infectious
