Hepatitis Viruses Flashcards
Chronic Hepatitis viruses are those which are
Parenterally transmitted
Acute Hepatitis infections are those which are?
Enterically transmitted
Hepatitis A general char
enterically transmitted (acute)
Hep B general?
parenterally transmitted
Hep C general?
Parenterally trans
Hep D general?
Dependent on co-infection with B
Hep E general?
Enterically transmitted
Hep G generall?
Parenterally transmitted
Hepatits A morphology
ss RNA, positive sense, Icosahedral capsid (no envelope…makes sense because an enveloped virus wouldn’t survive in the GI)
How many serotypes of Hepatits A are there and what implication does this have on the vaccine?
One serotype. Means its easy to make a vaccine
Reservoir for Hep A?
Humans
HAV spreads via which route?
Fecal- oral
Where does HAV replicate?
GI tract…incubation period here is about 15-30 days
Where does the virus spread?
LIVER (duh), spleen, kidney
Remember, the virus sheds in the GI tract during the asymptomatic incubation period. This is the period of time where it is spread most easily becase the pt doesn;t know they have it.
Once virus shedding is over, the pt is not infectious
What symptoms shows up once shedding stops
jaundice
Presentation of HAV pt?
Jaundice with high liver enzymes
DX of HAV
Isolated from the pts feces. Do an ELISA for anti-HAV IgM
At risk populations
Day Care Workers
Dudes (gay)
Diners (salad bar eaters especially)
Drug-users
What is a Hepatitis B virion called?
Dane Particle
What is the DNA structure of the HBV?
Partially dsDNA (one fill length circular DNA strand with another partial strand inside it).
What are the 5 major proteins encoded by the HBV genome?
- DNA polymerase with Reverse Transcriptase capability
- HBsAG (Hep B surface Antigen) this thing is an attachment protein found mostly in 20nm particles and filaments
- HBcAG: core antigen, capsid protein
- HBeAG: Secreted form of HBcAG ( important for diagnosis)
- x antigen: Influences gene expression
What is the significance of the HBsAG in regards to our immune response?
There are trillions of these things (they outnumber the actual virus particles by a long shot) but our immunoglobulins recognize the HBsAG which means that we have a huge immune reaction to the surface antigen fillaments and less of a reaction to the actual virions. They act as a smokescreen of sorts. Allows for infection to become chronic
What is one of teh first thing that happens to the HBV once it enters the cell and uncoats?
Completes the synthesis of the second DNA strand to produce a fully double stranded DNA genome
- Then gets supercoiled—-> enters nucleus
- Transcribes mRNAs to code for the four proteins
and one full length copy of the genome in RNA form. Need to get this back to a double stranded DNA structure, this is where the Reverse transcriptase comes in. - Once RT converts the RNA to DNA, the viral polymerase begins synthesizing the second DNA strand. Doesn’t finish it though.
- Gets packaged into a core structure
- Buds through the ER (picks up an envelope)
HBV is in a sense the exact opposite of HIV
ok…HIV is an RNA virus with a double stranded DNA intermediate
HBV endemic where?
China and Sub-Saharan Africa where infection occurs earlier, not necessarily more
HBV enters how?
Parenterally (not through the mouth) Mostly sexually transmitted
HBV replicates where?
Liver
HBV incubation?
45-160 days….way longer than HAV
Serological markers of HBV
HBsAG surface marker and HBeAG
How do you determine whether a person is chronically infected?
If at the 6 mos mark you are still detecting HBeAG and HBsAG instead of antibodies to these things then you can safely assume that the person is chronically infected
Screening positive for HBsAG means
The person is either recently (acutely) infected or they are chronically infected carrier
Screening positive for Anti-HBs
Person was infected in the past and it resolved, or the person was vaccinated
Screening positive for HBeAG
Active infection, high risk of transmission, high Viral levels
Screening positive for Anti HBe
carrier but low risk of transmission
Screening positve for Anti HBc
past infection, this will not be positive if they were simply vaccinated
IgM Anti-HBc
acute infection…IgM is early, IgG is late
What markers would you expect to see in a vaccinee?
Anti- HBsAG
What markers would you see in a high risk carrier?
HBeAG, HBV DNA, HBsAG
What markers would you see in a resolved acute infection?
Anti HBs and Anti HBc (core is not in the vaccine)
What markers would you see in a low risk carrier
Anti- HBe and HBV DNA and HBsAG
HDV morphology>
small circular ss RNA, non enveloped but has a capsid
Why is HDV defective?
It can replicate its genome but it cannot make a receptor therefore it relies on HBV infection to exist
What is a HDV co-infection?
This occurs when an HDV infection accompanies an acute HBV infection
What is a HDV super-infection?
Occurs when an HDV infection accompanies a chronic HBV infection
What tips you off to a HDV super-infection?
A pt with chronic liver disease from HBV suddenly gets worse
HCV structure?
ss RNA, positive sense, icosahedral capsid, enveloped
What is significant about the envelope proteins of HCV?
They are combined at first (E1 and E2 combined). They are cleaved by NS3 protease. This NS3 protease is a significant drug target/
How many genotypes of HCV are ther
6
which HCV genotypes are present in the US
1,2,3
US incidence of HCV?
2%
Highest incidence of HCV in 45-50 yo men
ok
The majority of HCV infections come from
Drug use
Besides drug use, what are some other modes of HCV contraction?
Sex, blood transfusions
Acute infections of HCV rarely lead to full liver infections
truth
KNOW
HCV pts can have multiple bouts due to reinfection. Antigenic variation accounts for most of the immune escape. This variation is mediated by changes in the hypervariable region (30 AA) of the E2 gene.
The cellular damage from HBV and HCV is from our own immune response. These viruses are not cytolytic
ok
40% of Chronic Hepatitis due to
HCV
20% of Chronic Hepatitis due to
HBV
Chronic HBV infection depends most on what?
Age of infection
Infection with HBV prior to the age of 1 means
90% chance you will have chronic HBV
1-5 yo= 30
over 5 yo= 2%
90% of hepatitis B infections in adults resolve
true
85% of infection with HCV
chronic
Time table for those with HCV left untreated
CHronic Hep (10 yrs) Cirrhosis (20) Cancer (30)
At risk HCV pts
anyone born between 1945- 1965
HCV incubation time
7-9 weeks
DX of HCV
Screen pts for HCV core antigen and then test HCV genotype using RT-PCR
Least curable form of HCV
Genotype 1
Most curable form
Genotype 2
Highest risk for fatality from HEV
Pregnant women
Reservoir for HEV?
Swine
Which of the hep viruses causes cirrhosis
B,C,D
WHich cause acute liver failure
A,E
Which cannot be cured
HCV chronic
When should you always be screened for HBV
Chemotherapy and HIV treatment