Flashcards in M- Hepatitis Viruses Deck (41)
What is the mode of transmission of HepA?
Where is infection with this virus most common?
What can stop the spread?
1. food and water
2. household contacts (most common)
3. sexual contacts
Common in developing countries- hand washing can stop spread
What is the mode of transmission of HepE?
It is transmitted by the fecal-oral route.
1. Water (most common route)
2. some food (pork)
Common in developing countries
Describe the genome of Hep A and Hep E.
HepA is RNA with 3 domains encoding structural and non-structural proteins
HepE is RNA with 2 domains encoding structural and non-structural proteins
What characteristic of the virion of HepA and HepE allow it to spread by the fecal oral route?
They have no lipid coat so detergents are not able to digest and destroy their infectivity.
How does HAV infection present in:
1. young children
2. older children and adults
Who is most likely to present with acute liver failure (fulminant hepatitis) from an HEV infection?
Women in the third trimester of pregnancy
What serology markers are measured for HepA?
Which are markers of acute infection?
Which are markers of prior infection?
1. IgM HAV Ab
2. Total (IgG+IgM) HAV Ab
1. Total (IgG+IgM) Ab
What serology markers are measured for HepA?
Which are for acute?
Which are for prior infection?
1. IgM HEV Ab
2. IgG HEV Ab
IgG HEV Ab
What is the therapy for HAV and HEV?
1. Supportive- anti-emetics, IV fluid, cholestyramine
If they have fulminant hepatitis they need a transplant
What is prevention AFTER exposure for HAV?
within 2 weeks the person can get intramuscular injection of ISG (immune serum globulin) an antibody titer to prevent clinical HepA
What is prevention of HAV before exposure?
a vaccine made of formalin activated HepA antigen
Describe the virion and genome of HBV.
Virion: Coat with host lipids
Genome: DNA with overlapping strands
Describe the structural genes and proteins of HBV.
Describe the non-structural genes and proteins of HBV.
Which gene is viral specific and consequently a drug target?
1. pre-S1, pre-S2, S (surface antigens)
2. C gene (core antigen)
1. P (polymerase)*** viral specific so drug target
2. pre-C (e antigen)
3. X gene
What part of HBV is done by host machinery?
What part of HBV replication is done by viral machinery (polymerase)?
HBV DNA is used to generate RNA transcripts to translate viral proteins (specifically polymerase)
1. polymerase does reverse transcription
3. DNA-dependent DNA synthesis
When can HBc be detected in the blood?
Where does immunohistochemical staining show HBc?
It can only be detected in the blood if the surface coat is removed.
Immunohistochemical staining using HBc antibody can demonstrate the presence of HBc in the nucleus of infected cells
What are the 3 ORFs of HBV? Which genes are in each?
1. Polymerase has its own
2. HBc, HBe and HBs are on one ORF
3. HBs from a much shorter RNA transcript... This makes surface coat too small to attach to hepatocytes but makes spheres and filaments
What are the three antigen-antibody systems for HBV?
What is each a marker of?
1. HBc Ab- marker of exposure
2. HBs Ab- marker of vaccination or resolution
3. HBe Ab- marker of replication
What is the first HBV antibody to be detected?
HBc IgM - a sign of acute infection
HBc IgG persists later as a marker of exposure
Do host or viral factors determine the outcome of a HBV infection?
HBV protein antigens are similar in acute, chronic, fulminant and asymptomatic so it is the HOST cytotoxic T cell immune response that determines how bad the infection is.
What is the HBV marker for replication? Why?
HBe because it is is translated on the same reading frame as HBc but is upstream.
If HBe Ag is detected, this means that all the machinery necessary for viral replication is available and being used.
High HBe in the blood means it is highly infection due to the replication
If HBe is not present in an HBV infection, what does that mean?
It means that the virus is not in an infectious state.
HBe is a pre-core sequence that encodes transport to the ER and secretion from the infected hepatocyte.
If HBe is not being translated, the virus remains in the hepatocyte.
How is HBV transmitted?
Which way is more associated with an ensuing chronic infection?
1. Percutaneously and through other body secretions
2. Vertical transmission- the baby will develop chronic hepatitis
Compare the incubation times for HAV, HEV and HBV.
HAV and HEV have a short incubation period (weeks) where HBV has a long incubation period of months
What are non-hepatic manifestations of HBV?
antigen-antibody complexes form causing:
1. serum sickness-like syndrome
What serology test is most informative for HBV if it is negative?
HBs Ab because as HBs Ag increases, the HBs Ab will decrease because it forms antigen-antibody complexes.
If HBs Ab is negative, but HBs Ag is positive, it means that the person has a chronic infection.
What serological test for HBV is most informative if it is positive?
HBe Ab because it is a sign of replication of the virus
What are the two groups of people where HBV becomes chronic?
1. Infants that got the virus through vertical transmission
2. Immunocompromised adults
Why is chronic hepatitis and cirrhosis rare after an icteric hepatitis in immunocompetent adults?
Icteric illness is a sign of immune responsiveness
What are the two treatments for chronic HBV?
How does each work?
1. decrease viral replication
2. boost immune response
This converts active (HBe Ag and HBV DNA +)
inhibit reverse transcriptase of HBV