Microbiology 2 Flashcards
Hep A Virus
enterically-transmitted “infectious” hepatitis
- family Picornaviridae, genes Enterovirus
- nonenveloped icosahedral capsid, <7kb ss RNA +
- single serotype
- spread: fecal-oral rout, replicates in GI tract
- incubation: 15-30 days (fastest)
- spreads to liver, kidney, spleen, isolated from feces
- onset of jaundice marks end of virus shedding
- in US, 33% have had HAV, and accounts for 33% of hepatitis cases
Hep B Virus
parenterally-transmitted “serum” hepatitis
- Hepadnavirus, virus partical (Dane particle)
- enveloped, dsDNA, 3200bp, L(-) full-length, S(+) 15-60% of L(-) strand
- ONLY ONE THATS DNA*
- patient blood has trillions of 20nm particles & filaments that have HBsAg & phospholipid (no genome)
Hep C Virus
“nonA, nonB PT-hepatitis
- Flaviviridae (hepacivirus), enveloped icosahedral
- 9.4kb genome ssRNA + (3,000aa) polyprotein is co & posttranslationally cleaved into 10 smaller (by NS3 protease, target for antiviral drugs)
Hep D Virus
dependent on co-infection with HBV
- delta virus, encodes delta Ag, found only in patients with chronic or severe HBV hepatitis
- defective circular ssRNA of 1.7kb
- requires HBV for transmission
- particles contain delta Ag and HBsAg which facilitates hepatocyte infection
Hep E virus
“nonA, nonB” ET-hepatitis
- calicivirus: nonenveloped icosahedral capsid, 7.5kb ss RNA +
- single serotype
- most in development countries
- 15-20% fatality rate seen in pregnant women
- swine/other animal reservoir (Japan)
HAV and HEV cause what?
acute hepatitis only
HBV and HCV cause what?
chronic hepatitis and leads to hepatocellular carcinoma
During Hep A outbreaks, who’s at highest risk?
- diners (employees not washing hands)
- day care center workers
- gay men
- injecting drug users
What 4 proteins, does Hep B encode?
- DNA polymerase w/reverse transcriptase activity
- HBsAg: surface antigen, attachment protein
- HBcAG: core antigen, capsid protein (HBeAg is secreted form of HBcAg, seroconversion is important to make chronic cases)
- X antigen: influences gene expression
Hep B Virus: Replication
- attachment/fusion at plasma membrane
- virus DNA reaches nucleus, completes dsDNA circle using host enzymes
- host cell DNA-dept. RNA polymerase transcribes DNA to make mRNAs & full-length RNA copies (called pregenomic RNA) which are the same sense as mRNA
- RNAs sent to cytoplasm, core protein made & encapsidates pregenomic RNA/DNA polymerase
- polymerase acts as reverse transcriptase of pregenomic RNA to give DNA L(-) strand
- buds out
Hep B Virus Transmission
- fecal-oral
- sexual
Hep B Virus Epidemiology
- endemic to China/Sub-Saharan Africa (early, 10-20% population)
- late infection in US/Europe, <1%
- replicated in liver
- incubation: 45-160 day, blood becomes infectious
- virus present in semen/vaginal secretions
Hep B Virus Chronic
-if not resolved in 6 months
Resolved: loss of HBV DNA, seroconverson of HBsAg to HBs abs
Chronic: HBV DNA & BBsAg remain, monitor for seroconverstion of HBeAg to HBe abs
-chronic patients remain asymptomatic until cirrhosis-related complications or hepatacellular carcinomas appear
Hep D Virus co-infection with Hep B
- provides surface antigen to Hep D
- severe acute disease
- low risk for chronic HDV infection
Super-infection of HBV patient (give Hep D)
- high risk for severe chronic disease
- tip off is often chronic HBV patient who is suddenly worse
