Viral Infection

Question 1

What are the features of a virus?

Answer 1

Protein spikes
Protein coat (capsid)
Nucleic acid (DNA or RNA)
Lipid envelope (not all)

Question 2

Why is a virus’ genome small?

Answer 2

It is limited by the size of the capsid/protein coat

Question 3

What are the types of virus structure?

Answer 3

Icosahedral symmetry

Helical symmetry

Question 4

What is icosahedral symmetry?

Answer 4

Like a 20 sided dice

Question 5

What kind of symmetry do adenoviruses have?

Answer 5

Icosahedral

Question 6

What is helical symmetry?

Answer 6

Made up of a single repeated subunit in a spiral structure

Question 7

How do non-enveloped viruses enter human cells?

Answer 7

Endocytosis

Question 8

How do enveloped viruses enter human cells?

Answer 8

The viral and cell envelope fuse, mediated by a viral enzyme

Question 9

What is endocytosis?

Answer 9

A viral cell enters the human cell by binding to a receptor, which initiates internalisation of both the receptor and the virus

Question 10

What process do viruses undergo after entering the cell?

Answer 10

Uncoating

Question 11

What can unceasing be due to?

Answer 11

The viral ion pump

Question 12

What is uncoating?

Answer 12

The viral nucleic acid is released from the capsid

Question 13

What is used as instructions to produce new viral proteins?

Answer 13

Nucleic acid

Question 14

What might crystals of assembling viruses be visible by light microscope as?

Answer 14

Inclusions

Question 15

What is assembly?

Answer 15

Nucleic acid and proteins are packaged together

Question 16

What step is not yet targeted by antivirals?

Answer 16

Assembly

Question 17

What are the two methods of viral release from host cells?

Answer 17

Budding

Lysis

Question 18

What is release by budding?

Answer 18

The mature replicated viral cells are released with envelopes derived from the host cell membrane

Question 19

Which type of viruses are released by lysis?

Answer 19

Non-enveloped viruses

Question 20

What is release by lysis?

Answer 20

Viruses accumulate until the virus lyses the cell and the viral cells burst out

Question 21

What is selective toxicity?

Answer 21

Where antibiotics are only target the pathogenic bacteria and not human cells

Question 22

What structures are targeted by antibiotics?

Answer 22

Bacterial ribosomes
Growing bacterial cell wall
Other structures and enzymes

Question 23

What are targets of antivirals?

Answer 23

Viral nucleic acid polymerases
Other viral enzymes involved in nucleic acid replication or protein synthesis
Enzymes involved in: 
- Uncoating 
- Attachment
- Entry
- Release

Question 24

What is rational drug design?

Answer 24

The use of detailed molecular analysis of viral targets to design a molecule that might inhibit its function rather than blind testing of random molecules for antiviral properties

Question 25

Where is rational drug design not a successful strategy?

Answer 25

Bacteria

Question 26

How can antiviral resistance be analysed?

Answer 26

Genotypically | Phenotypically

Question 27

What is phenotypic analysis of antiviral resistance?

Answer 27

Grown in vitro in presence of drug

Question 28

What is genotypic analysis of antiviral resistance?

Answer 28

The phenotype is inferred from the genotype

Question 29

What is pathogenesis?

Answer 29

The mechanism by which the virus causes disease

Question 30

What are methods of pathogenesis?

Answer 30

Cell death due to lysis or hijacking of cell machinery Cell death due to immune system Cell proliferation

Question 31

How would you establish whether a newly discovered virus is a pathogen?

Answer 31

A case control study Take a large group of people with clinical signs of infection Take a control group similar to the other group Compare prevalence of virus in the groups

Question 32

What may cell proliferation cause?

Answer 32

Cancer

Question 33

How do cytotoxic T cells destroy virally infected cells?

Answer 33

They recognise proteins on the cell surface as being foreign and induce apoptosis

Question 34

How do antibodies destroy virally infected cells?

Answer 34

Neutralising antibody prevents virus binding to cellular receptors

Question 35

Which classes of antibody are involved in destroying virally infected cells by neutralisation?

Answer 35

IgG | IgM

Question 36

What does it mean for a virus to become quiescent?

Answer 36

No active replication will take place

Question 37

How can recent infection be differentiated from past infection?

Answer 37

Detection of virus specific IgM antibodies Detection of virus specific IgG antibodies Detection of very high titre of IgG antibodies

Question 38

What may be required to differentiate recent infection and past infection?

Answer 38

Paired (acute and convalescent) blood samples

Question 39

What does convalescent mean?

Answer 39

Recovering from illness

Question 40

What methods are used for virus detection?

Answer 40

PCR | Antigen detection by various methods

Question 41

What techniques for virus detection are now less used?

Answer 41

Cell culture | Electron microscopy