Hepatitis Viruses I Flashcards
1
Q
Hepatitis means…
A
…inflammation of the liver.
- The causes of hepatitis are varied and include viruses, bacteria, protozoa and toxins.
- Viral hepatitis accounts for significant cases of hepatitis
- Some hepatitis may result in cirrhosis of liver and hepatocellular carcinoma (HCC)
2
Q
Other Viruses that can cause liver inflammation…
A
- Epstein–Barr virus (Herpesviridae)
- Cytomegalovirus (Herpesviridae)
- Varicella–zoster virus (Herpesviridae)
- Yellow fever virus (Flaviviridae)
3
Q
Hepatitis A Virus
A
- Hepatitis A Virus genus of the Picornaviridae family
- ( + ) ss RNA icosohedral naked
4
Q
Hepatitis A Structure
A
- small, icosahedral l (+) single stranded RNA (7.48 kb)
- 4 structural proteins
5
Q
Hepatitis A Replication
A
- replicates in the cytoplasm
- the mRNA is encoded as a polyprotein that is further cleaved to various mature proteins
- virus assembly in the cytoplasm lvirus release as a result of cell lysis
- difficult to propagate in vitro lseveral HAV strains
6
Q
HAV Clinical Disease
A
•Worldwide - Higher incidence in lower socioeconomic population
7
Q
HAV Transmission
A
•fecal–oral transmission, shellfish (oysters, clams), water, contaminated food, vegetables
8
Q
HAV Incubation
A
- Virus replicates initially in the enteric mucosa (incubation period 15 – 45 days, mean 25)
- Virus can be found in feces 10-14 days before the onset, replication in intestine, followed by a period of viremia with spread to the liver lmost infections are asymptomatic
9
Q
HAV
A
lacute hepatitis: replicate in small intestine, ldevelopment of viremia, spreads to liver
- replicates in the liver and causes necrosis of liver lonset is sudden after 14–40 days incubation
- The response to replication in the liver consists of lymphoid cell infiltration, necrosis of liver parenchymal cells, and proliferation of Kupffer cells. A variable degree of biliary stasis may be present
- Cytotoxic T lymphocytes (CTLs) damage the hepatocytes
- Initial immune response is the development of HAVspecific IgM antibody followed by appearance of IgG after a few weeks
10
Q
HAV Symptoms
A
- fever, poor appetite, nausea, headache, malaise, vomiting, abdominal pain, jaundice (may not develop in children), dark urine, clay-colored stool, enlarged liver
- usually self–limiting (complete recovery), immunity is complete
- In rare cases (~0.1%) fulminant hepatitis is associated with extensive liver necrosis
11
Q
HAV Prevention
A
- Immune serum globulin administered before or during incubation period. (Household members, travelers going to endemic areas)
- Inactivated Hepatitis A Vaccine: Havrix and VAQTA Inactivated Hepatitis A virus strain HM175
- Booster: 6-12 month after the initial dose
- Active immunization is as effective as ISG, if given shortly after exposure.
- 92% decline in HAV since vaccination (1995)
12
Q
Hepatitis B Virus
A
- Hepatitis B Virus genus of the Hepadnaviridae family
- partially ds DNA icosohedral enveloped
13
Q
Hepatitis B Structure
A
- Small (42 nm), circular, smallest DNA virus
- Partially double stranded DNA 3200 nucleotides associated with viral DNA polymerase
- HBcAg (core antigen) encloses DNA
- HBeAg (encoded by core gene), glycoprotein
- HBsAg (surface antigen) surrounds the core, envelope
- 4 subtypes of HBsAg (adw, ayw, adr, ayr)
14
Q
HBV Replication
A
- Full length (+)RNA is inserted into core
- Reverse transcriptase synthesizes a full length (–)DNA strand using the (+)RNA template
- (–)DNA template is used to make a variable short piece of (+)DNA l RNA degrades in the core
- Virus assembly in the cytoplasm
- Acquires envelope from Golgi or ER membranes
- Released from the cells
15
Q
HBV Epidemiology
A
- Worldwide, in the United States 0.1 to 0.5% of the population are chronic carriers
- 50% infections in U.S. are sexually transmitted