• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key

image

Play button

image

Play button

image

Progress

1/56

Click to flip

56 Cards in this Set

  • Front
  • Back
What are three clinically relevant families of enveloped dsDNA viruses?
1) Hepadenaviridae
2) Herpesviridae
3) Poxviridae
What type of nucleic acid do Hepadna viridae contain in their genome?

What is their capsid geometry?

Do they contain an envelope?
Incomplete circular dsDNA

Icosahedral

YES
What is the main human pathogen of the Hepadnaviridae?
Hepatitis B virus
Not all viruses causing hepatitis in humans are members of Hepadnaviridae.
What is the viral DNA structure of HBV?
Long, negative strand with a complementary short, positive strand.
What are two unique characteristics of HBV replication?
1) Use of an RNA intermediate
2) Use of revere transcriptase to create a template DNA strand inside the progeny capsid.
Hepadnaviridae are the only DNA viruses to replicate via an RNA intermediate.
What enzyme creates the RNA intermediate?
RNA polymerase II from the host cell.
Where in the cell is the RNA intermediate synthesized?
In the nucleus
Where in the cell is the DNA template created by reverse transcriptase?
In the cytoplasm
What are the steps of HBV replication?
1) Incomplete circular viral DNA moves into the nucleus
2) The virus produces complete circular DNA in teh nucleus
3) Viral DNA is transcribed into messenger RNA (mRNA) by host RNA polymerase II.
4) mRNA migrates to the cytoplasm where it is translated into proteins using host enzymes.
5) mRNA is reverse transcribed into a template strand by viral-encoded reverse-transcriptase enzyme
6) Template strand migrates into progeny capsid and is used to create a complementary DNA strand by host DNA-dependent DNA polymerase to form circular dsDNA progeny genomes.
What is the Dane particle?
Infectious HBV particle.
What are the four proteins encoded by HBV?
1) Hepatitis B surface antigen (HBsAg) encodes dy gene S.
2) Hepatitis B core antigen (HBcAg) encoded by gene C.
3) Protein X encoded by region X
4) Reverse transcriptase/DNA polymerase encoded by region P
What is hepatitis B e antigen (HBeAg)?
A truncated form of HBcAg associated with the HBV nucleocapsid that circulates in the serum
What is the significance of HBeAg?
Presence of HBeAg indicates increased transmissibility.
What are three modes of HBV transmission?
1) Blood-to-blood transmission (IV needles, infected blood transfusion)
2) Sexual transmission
3) Perinatal transmission, including breastfeeding.
What is the risk of becoming infected with HBV, hepatitis C virus (HCV), or human immunodeficiency virus (HIV) from a needle stick with contaminated blood?
20% chance of HBV infection
2% chance of HCV
0.2% chance of HIV infection
What are the signs and symptoms of acute HBV infection?
Jaundice, fatigue, nausea, vomiting, abdominal and joint pain, pruritus.
What are the signs and symptoms of acute HBV infection?
Elevated serum aminotransferases ([AST]/[ALT]), bilirubin, and alkaline phosphatase.
What is the prognosis for a patient with acute hepatitis B?
90% of patients clear infection
9% progress to chronic hepatitis
1% develop fulminant hepatitis and death
What are three ocmplications of chronic HBV infection?
1) Chronic hepatitis
2) Cirrhosis
3) Hepatocellular carcinoma
Why is hepatocellular carcinoma common in chronic carriers of HBV?
Chronic hepatocyte damage secondary to the immune response to the virus causes chronic cellular regeneration and an increased opportunity for mutagensis

HBV is not oncogenic by itself
Coinfection with what virus increases the risk of chronic and fulminant hepatitis in people infected with HBV?
Hepatitis D virus
What type of virus is Hepatitis D virus?
A defective RNA virus dependent on HBV for replication and its protective envelope.
Who is at greatest risk for chronic carriage of HBV?
Individuals infected as infants
90% of infected infants will progress to chronic HBV infection if not treated with vaccine and hepatitis B immune globulin.
Is there a vaccine for HBV?

Who is it administered to?
YES; a recombinant HBsAg
Routinely given in three doses to all children and those at high risk for exposure (health care workers)
What type of nucleic acid do Herpesviridae contain in their genome?

What is their capsid geometry?

Do they contain an envelope?
Linear dsDNA

Icosahedral

Yes, they are enveloped viruses
What unique structure lies between the envelope and capsid in Herpesviridae?
The tegument
What is the tegument?
A proteinaceous material containing virus-encoded enzyme and transcription factors.
How does the tegument contribute to the pathogenicity of the virus?
One of the tegument proteins is involved in activation of immediate early HSV-1 gene expression.
Where does replication of a herpesvirus occur?
In the nucleus
What are the three phases of herpesvirus gene expression?
1) Immediate-early
2) Early
3) Late
What do immediate-early genes code for?
Initiation of gene transcription in addition to a variety of regulatory functions.
What do early genes code for?
Enzymes that are necessary for replication of viral DNA including DNA polymerase, helicase, and thymidine kinase.
Why do herpesviruses require production of viral DNA polymerase?
They often infect nonreplicating cells (G0), i.e., cells that do not contain the cecessary enzymes for replication, e.g., neuronal cells.
What do late genes code for?
Structural proteins and proteins involved in assembly and maturation of viral progeny
Where do Herpesviridae assemble?
In the nucleus
How do Herpesviridae acquire their envelope?
Part of the envelope is acquired from the nuclear membrane, which is unlike most enveloped viruses that acquire their envelope form the plasma membrane.
What concept is a major characteristic of herpesviridae?

What is this?
Latent viral infections

A persistent infection with replication-competent virus that does not produce viral progeny.
What are the three classes of the herpesvirus family?

How are these classes differentiated?
1) Alphaherpesvirinae
2) Betaherpesvirinae
3) Gammaherpesvirinae

By their biologic characteristics, not by their morphology
What are three clinically relevant Alphaherpesviruses?
HSV-1
HSV-2
VZV
Where do Alphaherpesviruses establish latency?
Nerve ganglia
What are three clinically relevant Betaherpes viruses?
CMV
HHV-6
HHV-7
What are the characteristics of the growth cycle of Betaherpesviruses?
A slow repliction cycle resulting in formation of multinucleated, giant host cells.
Where do Betaherpesviruses establish latency?
Nonneural tissues, mainly macrophages and glandular tissue.
What are two clinically relevant Gammaherpesviruses?
EBV
HHV-8 (Kaposi sarcoma-associated herpesvirus)
Where do Gammagerpes viruses establish latency?
Mucosal epithelium, where they also induce proliferation of lymphoblastoid cells.
What type of nucleic acid do Poxviridae contain in their genome?

What is their capsid geometry?

Do they contain an envelope?
Linear, dsDNA with a large coding capacity.

Complex; it is neither icosahedral nor helical

YES, they contain a double envelope
Where does replication of poxviruses occur?

How is it able to do this?
Cytoplasm
Poxviridae are the only DNA viruses that replicate eentirely in the cytoplasm.

the virus encodes all enzymes necessary for replication, including a DNA-dependent RNA polymerase
How large are the poxviruses?
They are the largest viruses in size and are visible under the light microscope.
What are three clinically relevant viruses of the Poxviridaa family?
Variola
Vaccinia
Molluscum contagiosum
What disease is caused by variola infection?
Smallpox
How does smallpox present clinically?
Sudden onset of fever and malaise, followed by papular rash beginning on face and spreading to the extremities.
What is the vaccine for smallpox?
Live-attenuated vaccinia virus.
How effective is the vaccine for smallpox?
It was so effective that smallpox was the first infectious disease to be declared eradicated worldwide.
What makes the smallpox vaccine so effective?
1) Smallpox has only one stable serotype
2) There is no animal reservoir
3) the antibody response is prompt, so eposed people are protected
4) Subclinical disease is very rare; therefore most people infected with the virus are easily identified.
5) There is no carrier state.
What disease is caused to vaccinia?
Cowpox or 'milkmaid's blisters'
How does molluscum contagiosum present clinically?
Small, pink, wart-like benign tumor of skin or mucous membranes.