Attachment, Entry, Assembly and Exit (5,10)

Question 1

How is the growth curve different between enveloped and non-enveloped viruses?

a. Non-enveloped viruses do not demonstrate a latent period
b. Enveloped viruses have a higher yield when they are intracellular
c. Intracellular viruses have a higher yield when non-enveloped and extracellular viruses have a higher yield when enveloped
d. The uncoating phase is only seen in enveloped viruses and has a low gradient on the curve

Answer 1

c. Intracellular viruses have a higher yield when non-enveloped and extracellular viruses have a higher yield when enveloped

Question 2

What does it mean if P(0) = 0.02?

a. The multiplicity of infection is at 2%
b. 2% of cells are not infected
c. There is a 2% chance that any cell will become infected
d. There are 2 plaque forming units/cell

Answer 2

b. 2% of cells are not infected

Question 3

What is not a method used by viruses to invade host cells?

a. Fusion and direct uncoating at the plasma membrane
b. Pinocytosis or phagocytosis
c. Endocytosis followed by uncoating within the endosome
d. Endocytosis followed by uncoating at the nuclear membrane

Answer 3

b. Pinocytosis or phagocytosis

Question 4

What is NOT involved in the entry and uncoating of adenovirus?

a. The virus directly fuses with the host cell using CAR receptors and uncoats at the cell surface
b. When the endosome acidifies, the penton base is released and bursts the endosome so the capsid can be released
c. The adenovirus penton fibre interacts with intergrins recpetors called CAR to initiate RME
d. Once the capsid is released from the endosome, it travels to the nuclear pore using the host cell microtubule network

Answer 4

a. The virus directly fuses with the host cell using CAR receptors and uncoats at the cell surface

Question 5

What is NOT involved in the entry and uncoating of Reovirus?

a. The capsid undergoes proteolysis in the endosome to produce the infectious subviral particle (ISVP)
b. ISVP proteins prevent endosome maturation and the virus can persist in the host
c. The outer capsid proteins bind cell receptors to mediate RME
d. ISVP proteins mediate membrane penetration

Answer 5

b. ISVP proteins prevent endosome maturation and the virus can persist in the host

Question 6

What does not occur during entry of Influenza?

a. Envelope haemagglutinin molecules bind sialic acid on cell glycoproteins
b. Neuraminidase releases sialic acid and is part of the viral envelope
c. Endosome acidification is required so that the fusion domain of haemagluttinin can be exposed
d. The virus enters host cells by interacting with glycoprotein siali acid and directly fusing with the plasma membrane

Answer 6

d. The virus enters host cells by interacting with glycoprotein siali acid and directly fusing with the plasma membrane

Question 7

What is CD46/SLAM?

a. A paramyxovirus ligand that reacts initiates fusion of the measles virus
b. A HIV-1 ligand that interacts with CD4 co-receptors during cell entry
c. The product of VP4 in Rotavirus following cleavage by trypsin
d. The flavivirus peptide that initiates membrane fusion following conformational change

Answer 7

a. A paramyxovirus ligand that reacts initiates fusion of the measles virus

Question 8

What is the correct description for HIV-1 glycoproteins?

a. Gp120, gp41 and gp160 all exist as a trimer
b. Only gp160 can bind CD4
c. Gp160 is the precursor for gp41 and gp120
d. Gp41 is a surface protein and gp120 is a transmembrane protein

Answer 8

c. Gp160 is the precursor for gp41 and gp120

Question 9

What happens during HIV entry? (put in order)
• Binding of gp120 to CCR causes conformational change in gp41 (transmembrane) and fusion peptide is inserted into membrane
• Gp120 (surface) binding to CD4 causes conformational change in gp120. Exposes binding site for chemokine coreceptor (CCR)
• HIV-1 envelope glycoproteins gp120-41 bind CD4

Answer 9

• HIV-1 envelope glycoproteins gp120-41 bind CD4
• Gp120 (surface) binding to CD4 causes conformational change in gp120. Exposes binding site for chemokine coreceptor (CCR)
• Binding of gp120 to CCR causes conformational change in gp41 (transmembrane) and fusion peptide is inserted into membrane

Question 10

What is used to determine is a virus infects a cell via endocytosis or direct fusion?

a. Genome sequencing and analysis
b. Exposing cells to a weak base to prevent endosome acidification
c. Electron microscopy
d. PCR for well-known fusion proteins such as SLAM, Gp120 and Gp41

Answer 10

b. Exposing cells to a weak base to prevent endosome acidification

Question 11

• Initial binding of a virus is specific and the strongest form of attachment due to covalent protein-protein interactions.

Answer 11

F

Question 12

• Virions may enter a cell by fusion, receptor mediated endocytosis or passive pinocystosis.

Answer 12

F

Question 13

• Measles virus unocats by fusing their envelope with the cell plasma membrane.

Answer 13

T

Question 14

• Poliovirus enters a cell after interaction between the CD155 receptor and capsid leads to a conformational change of the VP1 capsid protein.

Answer 14

T

Question 15

• All reoviruses have a double shelled capsid except for rotavirus.

Answer 15

F

Question 16

• It is common for enveloped viruses to enter in the endosome and rely on endosome acidification initiating a conformational change.

Answer 16

T

Question 17

What is not a step in virus assembly shared by all viruses?

a. Form individual structural units of protein shell from one/several viral proteins
b. Selective nucleic acid packaging and other essential virion components
c. Envelope acquiring
d. Protein shell assembly, interactions between structural units

Answer 17

c. Envelope acquiring

Question 18

What is not an issue to consider during virus assembly?

a. Some viruses require access to viral-encoded non-structural morphogenetic factors, such as chaperones
b. Proteins and nucleic acids must reach their correct location
c. Intracellular trafficking is essential
d. Virion components can be hard to locate when mixed up in the cytoplasm of non-compartmentalised eukaryotic cells

Answer 18

d. Virion components can be hard to locate when mixed up in the cytoplasm of non-compartmentalised eukaryotic cells

Question 19

What is ψ?

a. Viral nucleic acid that has been distinguished from host cell DNA/RNA
b. Packaging signals in the viral genome
c. A morphogenetic chaperon required for virus assembly
d. The inverted repeat present in the HIV genome that aids in genome packaging

Answer 19

b. Packaging signals in the viral genome

Question 20

What is involved in the genome packaging of adenovirus?

a. The RNA genome is spliced and each mRNA is tagged with a specific packaging signal
b. A complex, repeating and overlapping packaging signal at the left IR and origin has enhancers to stimulate late transcription
c. The packaging signal at the right IR interacts with viral IV2A to stimulate early transcription
d. Because it has a dsDNA genome, it manipulates host cell machinery to selectively target viral proteins

Answer 20

b. A complex, repeating and overlapping packaging signal at the left IR and origin has enhancers to stimulate late transcription

Question 21

What is not involved in the packaging of the HIV genome?

a. Stem Loop 3 is only exposed in monomeric RNA which signals for packaging to occur
b. Gag NC mediates selective encapsidation of genome RNA during assembly
c. Ψ signals are in spliced regions so that only genomic RNA, and not mRNA, is packaged
d. The NC only binds to dimeric RNA that represents genomic HIV nucleic acid

Answer 21

a. Stem Loop 3 is only exposed in monomeric RNA which signals for packaging to occur

Question 22

What is not a way that virions can be assembled?

a. Association of individual monomeric proteins translated as separate components
b. From large polyprotein subunits refolded after proteolytic processing
c. With assistance of viral or cellular chaperon proteins for folding
d. Using scaffold proteins that bring components together and are incorporated into the mature particle

Answer 22

d. Using scaffold proteins that bring components together and are incorporated into the mature particle

Question 23

How does the virion assembly of SV40 and Adenovirus compare?

a. Both viruses require the chaperon protein L4
b. Adenovirus has spliced mRNAs that translate monomeric proteins
c. In adenovirus monomeric proteins assemble to penton units first as homo-multimers
d. Sv40 has Hexon units made from trimers of papovaviral protein II

Answer 23

c. In adenovirus monomeric proteins assemble to penton units first as homo-multimers

Question 24

What is NOT involved in the encapsidation of Herpes Virus?

a. Genome replication makes concatomers
b. Packaging signals, pac1 pac2 are recognised so viral DNA can be cleaved within DR1
c. One end of the genome is recognised by the pac proteins before cleavage and encapsidation
d. Scaffold proteins are involved and a protease is required to finalise the viral structure

Answer 24

c. One end of the genome is recognised by the pac proteins before cleavage and encapsidation

Question 25

What happens during the assembly and encapsidation of poliovirus? a. The process relies on the action of the L4 chaperone b. Proteolytic cleavage and correct protein folding is essential c. VP2 and VP4 are cleaved to form VP0 d. The 5s structural unit is made up of 3CDpro subunits

Answer 25

b. Proteolytic cleavage and correct protein folding is essential

Question 26

Put the sequence of poliovirus maturation and exit in order 1. Particles assemble in cytoplasm (incompletely cleaved, retain VP0) 2. Cell dies, virus released 3. RNA genome replication in cytoplasm in smooth ER 4. Package viral RNA and form non-infectious virion 5. Final cleavage of VP0 to VP4 and 2 leads to infectious virus

Answer 26

3. RNA genome replication in cytoplasm in smooth ER 1. Particles assemble in cytoplasm (incompletely cleaved, retain VP0) 4. Package viral RNA and form non-infectious virion 5. Final cleavage of VP0 to VP4 and 2 leads to infectious virus 2. Cell dies, virus released

Question 27

Which virus is huge and capable of inducing cell lysis to release viral particles? a. Adenovirus b. Poxvirus c. Poliovirus d. Mimivirus

Answer 27

d. Mimivirus

Question 28

What best describes a strategy used in the assembly of an enveloped virus? a. Alphavirus depends on envelope glycoproteins and capsid b. Coronavirus requires the internal matrix and capsid proteins to drive budding c. Retrovirus budding is driven by envelope proteins d. Picornavirus budding is driven by matrix proteins and RNP for efficiency

Answer 28

a. Alphavirus depends on envelope glycoproteins and capsid

Question 29

What is false about the targeting of virus glycoproteins and enveloped virus assembly? a. BFA can block viral infection by blocking ER to Golgi transport b. Glycoproteins with retention motifs are destined for the ER or Golgi c. Glycoproteins can only target the plasma membrane due to the thickness of their transmembrane domain d. Glycoproteins require specific processing in the ER and Golgi

Answer 29

c. Glycoproteins can only target the plasma membrane due to the thickness of their transmembrane domain

Question 30

What is not involved in the assembly of influenza virus? a. Mature HA, NA and M2 are made in the nucleus b. M1 binds RNP and prevents further transcription and NEP binds the complex via M1 c. When the membrane pinches off, NA cleaves sialic acid and the virion is released d. Glycoproteins concentrate in the PM and are bound by M1 which initiates budding

Answer 30

a. Mature HA, NA and M2 are made in the nucleus

Question 31

What would happen if furin was not functional in a cell infected with Flavivirus? a. The virus would fail to exit the recycling endosome b. prM would not be cleaved to M and the virus would not mature c. The viral envelope would fuse with cell envelopes during its transport d. pH would not have a role in maturation of the virion

Answer 31

b. prM would not be cleaved to M and the virus would not mature

Question 32

What is false about the assembly and maturation of HIV? a. The virus assembles at the plasma membrane due to the accumulation of TM-SU, myr-MA-GAG into lipid rafts b. HIV Gag-MA is modified by myristoylation and phosphorylation c. TM-SU has RNA binding sites (basic) and two zinc-finger motifs d. Furin cleavage releases Tm and SU from env precursor

Answer 32

c. TM-SU has RNA binding sites (basic) and two zinc-finger motifs

Question 33

How does vaccina exit the cell? a. It travels to the edge of the cell via actin b. It exits the cell by hijacking microtubules and using them as propeller like tails c. It uses the secretory network to exit via exocytosis d. It utilises microtubules and actin

Answer 33

d. It utilises microtubules and actin

Question 34

• The adenovirus packaging signals is in spliced regions so only genomic RNA is packaged as opposed to mRNAs.

Answer 34

F (HIV)

Question 35

• New DNA virus particles are often released after a cell breaks down due to the toxic effects of viral proteins.

Answer 35

T

Question 36

• Most DNA viruses assemble in the nucleus.

Answer 36

T

Question 37

• SV40 Vp1,2,3 can enter the nucleus due to the action of the L4 chaperone.

Answer 37

F

Question 38

• Adenovirus hexon proteins lack a NLS but still enter the nucleus due to the action of a chaperon.

Answer 38

T

Question 39

• Nuclear localisation signals have a high amount of basic charged AAs which can bind nucleic acid.

Answer 39

T

Question 40

• Membrane bound glycoproteins are translated on free ribosomes.

Answer 40

F

Question 41

• Ribosomes dock to the ER if the translated protein has a N terminal 20 AA hydrophilic sequence.

Answer 41

F

Question 42

• Enveloped viruses bud from the cell membrane so that the cell membrane forms the coat with viral proteins and the nucleocapsid is inside.

Answer 42

T

Question 43

• The movement of viral proteins and particles with the cell is independent of host cell processes.

Answer 43

F

Question 44

• Flavivirus exits the cell by exocytosis after passing through the ER, Golgi and Recycling Endosome.

Answer 44

T

Question 45

• During HIV maturation, Gag myristoylation promotes binding to phosphatidylinositol-(4,5)-bisphosphate which is only found in the PM.

Answer 45

T

Question 46

• When exiting polarised cells, viruses that exit apically come into contact with blood, lymph and nerves and can spread systemically.

Answer 46

F