Microbiology- Viruses and Disease

Question 1

4 components of a virus molecule

Answer 1

protein spikes
protein coat (capsid)
nucleic acid
envelope

Question 2

Viruses contains RNA and DNA. T/F

Answer 2

False

They only contain one or the other as they have a very small genome, which is limited by the capsid

Question 3

What comprises the protein coat?

Answer 3

repeated subunits of virally encoded protein

Question 4

Where is the lipid envelope derived form?

Answer 4

The host cell which the virus grew in

Question 5

Limitation of microscopy

Answer 5

Only tells you the shape of a microbe, which may be indistinguishable from others in its group

Question 6

How does a virus become phagocytosed?

Answer 6

• Attachment
• Entry
• Uncoating
• Nucleic acid and protein synthesis
• Assembly
• Release

Question 7

How does a virus attach to a cell?

Answer 7

its ligand attaches to specific receptors on target cell

Question 8

By which process may non-enveloped viruses enter the cell?

Answer 8

Endocytosis

Question 9

How do enveloped viruses enter the cell?

Answer 9

By fusion of viral and cell envelopes

Question 10

What is endocytosis

Answer 10

binding to receptor initiates internalisation of both the receptor and the virus

Question 11

Uncoating

Answer 11

Viral nucleic acid is released from capsid due to viral ion pump

Question 12

Nucleic acid and protein synthesis

Answer 12

Nucleic acid is used as instructions to produce new viral proteins - host ribosomes are ALWAYS used and host polymerases may be used.
Viral nucleic acid is replicated into progeny genomes

Question 13

Assembly

Answer 13

Nucleic acid and proteins packaged together

Question 14

Inclusions

Answer 14

crystals of assembling virus may be seen under light microscopy

Question 15

Release

Answer 15

A piece of the host membrane ends up around capsid ie reverse of entry process

Question 16

Release by budding

Answer 16

Mature progeny virus released with envelope derived from the host cell membrane.
NOT ALL VIRUSES RELEASED LIKE THIS

Question 17

Release by lysis

Answer 17

virus breaks down the cell

Question 18

Antibiotics are active against viruses. T/F?

Answer 18

False

only active against bacteria

Question 19

Objective of antibiotics

Answer 19

Selective toxicity

Question 20

How do antivirals inhibit entry?

Answer 20

Via fusion, mediated by viral enzyme

Question 21

How do antivirals inhibit uncoating?

Answer 21

they inhibit the ion pump in the virus capsid

Question 22

How do antivirals inhibit assembly?

Answer 22

No antivirals target this step yet

Question 23

Rational drug design for antivirals

Answer 23

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 24

In which setting is antiviral resistance most seen?

Answer 24

long periods of treatment eg immunocompromised patients

Question 25

How is antiviral resistance analysed?

Answer 25

genotypically
- the phenotype can be inferred from genotype

can also be done phenotypically ie green in vitro in presence of drug

Question 26

How to establish if a newly discovered virus is a pathogen?

Answer 26

Case-control study

• One group with clinical signs of infection
• Second group as similar as possible to the first group, except that they are well
• Compare prevalence of virus in the cases and the controls

Question 27

Role of cytotoxic T lymphocyte in immunity and virus infection

Answer 27

recognise proteins on the cell surface as being foreign and will signal the infected cell to commit suicide in order to prevent the formation of further mature virus

Question 28

Examples of neutralising antibodies and their role in immunity and infection

Answer 28

IgG, IgM

Bind to cell receptors

Cell mediated immunity is generally more important than humoral immunity in providing recovery from viral infection, though antibodies have a clear role in long term adaptive immunity

Question 29

Quiescent

Answer 29

Becomes latent but may reactivate

eg Herpes simplex virus, Varicella-zoster virus

Question 30

Examples of continually active viruses/ chronic infections

Answer 30

• HIV

- Hep C

Question 31

How to confirm viral infection in lab

Answer 31

detect antibody response to virus and the virus itself

Question 32

Ways in which recent and past infection can be differentiated?

Answer 32

Detection of:

• virus specific IgM
• rising titre of IgG
• very high titre of IgG

Paired blood samples may be needed ie acute and convalescent

Question 33

Virus detection methods

Answer 33

PCR
Antigen detection
- cultures, EM