Wk5 Viral Hepatitis Flashcards
Class IV SS(+) RNA
Icosahedral
Nonenveloped
Picornoviridae
Enterovirus
Hep A
Strength of Hep A viral capsid?
stable at pH 1
**inactivated by chlorine, formalin, UV radiation
Hep A route of infx:
fecal - oral
Surface receptor on cells infected by Hep A:
What cells are they?
HAVCR-1
liver cells, T cells
How/when Hep A gets to stool:
replicates in liver
shed into stool 10 days before pt gets jaundice
Pathogenesis of Hep A:
immune response of cytotoxic T cells
HAV itself is not cytotoxic
Why is Hep A spread so easily?
contagious 10-14 days before sx show up
many have asymptomatic but contagious infx
Onset of Hep A sx:
15-50 days post exposure
Sx of Hep A:
4-6 days
fever
fatigue
nausea
loss of appetite
abd pain
dark urine
jaundice
99% have full recovery
Lab dx fo Hep A:
anti-HAV IgM on ELISA
Prophylactic tx for HAV:
immune globulin serum
VACCINE
- 2 dose
- Killed HAV vaccine
Class IV SS(+) RNA
Icosahedral
Nonenveloped
Calciviridae
Hep E
Particularly dangerous for pregnant women:
Hep E
Sx of HEV:
Very similar to HepA, slightly later onset, slightly more severe
no treatment or vaccine
fever, fatigue, nausea, loss of appetite, abd pain, dark urine, jaundice
Class VII DS(partial) Circular DNA
Icosahedral
ENVELOPED
Hepadnaviridae
Hep B
Liver cell receptors for HBV docking:
transferrin
asialoglycoprotein
annexin V protein
HBV viral bonding protein:
HBsAg
What determines course of HBV and whether acute/chronic, asymptomatic/symptomatic disease develops?
host immune respone
if effective, disease resolves
Antibodies signaling protection/neutralization of HBV:
anti-HBsAg
”s” = surface antigen
What is the HBs “window”?
time between decline of serum HBsAg and detection of Anti-HBs antibodies
???
What happens in limited cell-mediated immune response to HBV?
chronic disease (mild s) –>
- fulminant hepatitis (can be expedited by addition of HDV)
- primary hepatocellular carcinoma
- Cirrhosis
Serology for chronic HBV:
Serum HBsAg, HBeAg
Serum Anti-HBc……maybe anti-HBe (late acute)
???
source or HBV spread:
blood
body fluids including saliva and milk
Onset of sx in HBV:
up to 45 days
**virus starts replicating 3 days post infx
Review slide
37-38
Difference in serology of person vaccinated against HBV and healthy person who had the virus:
Vaccinated: Anti-HBs only
Prior infx: Anti-HBs + Anti-HBc +/- Anti-HBe
What does it mean if follow up serology of known HBV infx comes back negative for HBsAg and Anti-HBs Ab’s?
Patient is in “window” period and test needs to be repeated
In chronic HBV, how to differentiate serologically between active viral replication and non-replicating virus?
active viral replication will be HBeAg positive and anti-HBe negative
Follow up for non-replicating chronic HBV infx:
HBV DNA test
serum ALT
if elevated –> liver biopsy
if low/normal –> monitor
Vaccination for HBV:
infants/children
high risk groups
Prophylaxis for HBV:
immune globulin serum
newborns to HBsAg+ mothers
individuals within one week of exposure
Tx for chronic HBV:
HBV polymerase inhibitors
nucleoside analogues
INF-a
Class V SS(-) RNA Circular
ENVELOPED
Icosahedral
Hep D
“Deltavirus”
Why does HDV require prior or co- HBV infx:
needs HBsAg for packaging
Chronic HBV carrier subsequently infx with HDV = ?
superinfection
**progresses more rapidly than co-infection
Tx for HDV:
clear HBV
Class IV SS(+) RNA
ENVELOPED
Icosahedral
Flaviviridae
Hep C
Test for HCV:
Anti-HCV (total)
If Anti-HCV is positive, order:
Quantitative RT-PCR for genome in serum
If quant RT-PCR for HCV is positive?
anti-viral therapy
If quant RT-PCR but liver enzymes remain elevated in 1-2 months?
repeat test
**continued positive Anti-HCV + negative RT-PCR = prior infx
Liver cell surface target of HCV:
CD81 – tetraspanin
**also on B-cells
How does HCV promote persistent infx?
inhibits apoptosis
inhibits INF-a
Gold standard dx test for HCV and tx planning:
RT-PCR – detection, quantitation, genotyping
Tx for Hep C:
INF-a
ribavirin
NS5A/B inhibitors
Class IV SS (+) RNA
ENVELOPED
icosahedral
Flaviviridae
Flavivirus
Yellow Fever
Route of infx for yellow fever:
Aedes mosquito
Disease course for yellow fever:
cytolitic –> serious life-threatening infx
both humoral and cellular immune response destroys tissue
Prevention of Yellow fever?
live-attenuated vaccine
