Deck 12: Flaviviruses

Question 1

Which of the following describes the phenomenon of antibody-dependent enhancement?

A) Antibodies bound to a flavivirus particle allows entry into a cell via the Fc receptor.
B) Antibodies bound to the host cell receptor make it unable to bind a flavivirus particle.
C) Antibodies bound to infected cells cause the immune system to kill them.
D) Antibodies bound to a flavivirus particle allow it to be removed by the immune system.
E) The overproduction of antibodies during a flavivirus infection

Answer 1

A

Question 2

How was Yellow Fever Virus introduced into the New World from Africa?

A) Infected animals were imported.
B) Tires containing infected mosquitoes were imported.
C) Migrating birds brought it.
D) It came over on slave trading ships.
E) Walter Reed released it from a laboratory.

Answer 2

D

Question 3

Flavivirus virions obtain their envelopes from the cellular membranes of which of the following organelles?

A) Endoplasmic Reticulum
B) Nucleus
C) Golgi apparatus
D) Plasma membrane
E) Mitochondria

Answer 3

A

Question 4

Infection with a second strain of Dengue fever virus within two years of having had the first strain causes Dengue Hemorrhagic Fever.

Question 5

West Nile Virus was introduced into the United States in 1999 and became an endemic infection over the next several years.Which of the following wild animal populations does this virus circulate in?

A) Bats
B) Bees
C) Birds
D) Beetles
E) Bears

Question 6

A cloned DNA copy of the yellow fever virus can be used to produce infectious viral RNA.

Question 7

Which of the following statements comparing flaviviruses with togaviruses is FALSE?

A) Flaviviruses have a T=3 capsid while togaviruses have a T=4 capsid.
B) Flaviviruses have smaller virions that togaviruses.
C) Flaviviruses do not produce subgenomic RNAs like togaviruses.
D) Flaviviruses have enveloped virions but togaviruses have naked virions.
E) Flaviviruses produce a single-polyprotein while togaviruses produce more than one.

Question 8

In the mature flavivirus virion, the fusion peptide on the E protein is buried in the dimer interface.Which of the following conditions causes the fusion peptide to become exposed?

A) Uptake of the virion via receptor mediated endocytosis.
B) Interaction with the sialic acid residues on the surface of the cell.
C) Binding to the host cell receptor on the surface of the cell.
D) Drop in pH in the endosome.
E) Binding to the host cell membrane.

Question 9

Which of the following conditions is required to induce fusion of the flavivirus envelope with the host cell membrane?

A) Increase in pH
B) Decrease in pH
C) Binding of envelope protein to the host cell receptor
D) Uptake of the virion into a vesicle.
E) Proteolytic degradation of the virion.

Question 10

Which of the following statements comparing flaviviruses with picornaviruses is FALSE?

A) They both use an IRES to initiation translation of the viral genome.
B) They both have enveloped virions
C) They both encode the structural proteins at the 5' end of the genome.
D) They both produce their proteins from a single open-reading frame.
E) They both produce viral proteases to cleave the polyprotein.

Question 11

Which of the following proteins from flaviviruses has the RNA-dependent RNA polymerase activity?

A) NS1
B) NS2
C) NS3
D) NS4
E) NS5

Question 12

Which of the following techniques was used to isolate the flavivirus Hepatitis C virus?

A) Molecular cloning of the viral cDNA
B) Purification of virus particles
C) Antibody staining with patient serum
D) Plaque assay
E) Southern blotting

Question 13

When is the "pr" region cleaved by the protease furin from the prM protein of flaviviruses?

A) During translation of the structural proteins.
B) When the virion acquires the envelope from the ER.
C) As the capsid is being assembled in the cytoplasm.
D) After the virion moves through the trans Golgi network.
E) After release of the virions from the host cell.

Question 14

The hydrophobic region of the flavivirus capsid protein is thought to do which of the following?

A) Bind to the host cell receptor.
B) Interact with the viral envelope.
C) Insert into the host cell membrane.
D) Interact with and condense the genomic RNA.
E) Bind to other capsid proteins.

Question 15

The yellow fever vaccine strain has 32 amino acid mutations in comparison to the wildtype pathogenic virus strain.Which of the following genes contains the majority of these amino acid substitutions?

A) Polymerase
B) Capsid protein
C) Envelope glycoprotein
D) Protease
E) Helicase

Question 16

Which of the following describes the primary mechanism of transmission of the flavivirus Hepatitis C?

A) Mosquito bites
B) Contaminated blood transfusions
C) Aerosols
D) Contaminated food and water
E) Animal bites

Question 17

Which of the following cellular proteases helps to process the polyprotein of flaviviruses?

A) Chymotrypsin
B) Trypsin
C) Furin
D) Cathepsin D
E) Papain

Question 18

The nonstructural proteins of flaviviruses are produced on the rough ER and have membrane spanning domains.Which of the following explains why the nonstructural proteins are localized to cellular membranes?

A) Fatty acids are a required cofactor for RNA synthesis.
B) Viral RNA replication can only occur in the lumen of the ER.
C) Membranes serve to localize the viral replication complex.
D) The viral replication proteins must be glycosylated before they are active.
E) The nonstructural proteins require proteolytic processing by lysosomal enzymes.

Question 19

Which of the following diseases is caused by a member of the flavivirus family?

A) Yellow Fever
B) Dengue Fever
C) West Nile Encephalitis
D) Hepatitis C
E) All of the above.

Question 20

Which of the following describes the reason why the precursor to the capsid protein from flaviviruses has a membrane spanning domain?

A) So that it is localized on the membranes where viral RNA replication takes place.
B) So that it islocalized on the membranes where the virions obtain their envelope.
C) So that it is close to where the other structural proteins are localized.
D) So that it will be translated by ribosomes associated with the ER.
E) All of the above are correct.

Question 21

Describe the final processing steps that the flavivirus virion goes through in order to be converted from an immature virion into a mature infectious virion.

Question 22

Once the West Nile Virus became endemic in the United States, 20% of the population has seroconverted to the virus.

Question 23

In a flavivirus infection, newly synthesized positive-strand RNA genomes can only be packaged into new virions.

Question 24

Describe the events that events that lead West Nile virus from moving from a local epidemic to becoming endemic in the United States.

Question 25

Since flaviviruses replicate in the cytoplasm of the host cell, they do not need to encode a methyltransferase enzyme to produce the 5' cap on the viral genomic RNA.