Viruses and Prions

Question 1

What type of nucleic acid do viruses have?

Answer 1

Either DNA or RNA (unlike bacteria which have both)

Question 2

What does the term ‘metabolically inert’ mean?

Answer 2

• Viruses cannot reproduce on their own
• Need to hijack components of host in order to reproduce
• They do not possess ribosomes/cannot perform protein synthesis

Question 3

What is a bacteriophage?

Answer 3

A virus that infects bacteria

Question 4

What size is a virus? (in nm)

Answer 4

1000-3000 nm

Question 5

What is the virus protected by?

Answer 5

• Envelope - lipid membrane (around some viruses)

- Capsid: protein shell

Question 6

What are capsids composed of?

Answer 6

Capsomeres (protein units)

Question 7

What are some of the modes of viral transmission?

Answer 7

• Inhalation via respiratory tract
• Ingestion via G.I. tract
• Inoculation: skin abrasions mucous membranes, transfusions, transplants, injections, bites
• Congenital: mother to foetus
• Sexual transmission

Question 8

Which organ system does rabies affect?

Answer 8

Nervous system

Question 9

Which organ system does influenza affect?

Answer 9

Respiratory system

Question 10

Which organ does herpes simplex affect?

Answer 10

Localised disease of the skin and and mucous membranes

Question 11

Which organ does adenovirus affect?

Answer 11

Eye

Question 12

Which organ does hepatitis affect?

Answer 12

Liver

Question 13

Which organs do mumps affect?

Answer 13

Salivary glands

Question 14

Which organ system does norovirus affect?

Answer 14

G.I. tract

Question 15

How is HIV commonly transmitted?

Answer 15

Sexually transmitted

Question 16

What does ‘cytopathic effect’ refer to in viral infections?

Answer 16

• Structural changes in host cells that are caused by viral invasion
• Can result in cell death

Question 17

What does ‘transformation’ refer to?

Answer 17

Cell not killed, changed to cancerous cell

Question 18

What does ‘latent infection’ mean?

Answer 18

Virus remains in cell, no obvious effect on cell function

Question 19

What are the stages in viral replication?

Answer 19

1. Attachment
2. Penetration
3. Uncoating
4. Synthesis of viral components
5. Assembly
6. Release

Question 20

How many people died from the flu in 1918?

Answer 20

40 million

Question 21

What are the 3 different types of influenza virus (RNA viruses)?

Answer 21

Type A
Type B
Type C

Question 22

What are the 2 key molecules on the surface of viruses that are often targeted by vaccines?

Answer 22

Haemagglutinin

Neuroaminidase

Question 23

What type of nucleic acid do influenza viruses contain?

Answer 23

RNA

Question 24

What is haemagglutinin?

Answer 24

• Glycoprotein
• Sialic acid binding
• 14 H types

Question 25

How many types of haemagglutinin are there?

Answer 25

14

Question 26

What is neuraminidase?

Answer 26

- Glycoprotein - Virion release - 9 N types

Question 27

How many types of neuraminidase are there?

Answer 27

9

Question 28

Which molecule present on the surface of the influenza virus enables virion release?

Answer 28

Neuraminidase

Question 29

Which molecule present on the surface of the influenza virus binds to silica acid?

Answer 29

Haemagglutinin

Question 30

What is antigenic drift?

Answer 30

- Minor change - Point mutations - Results in epidemics - A, B and C drift - Haemagglutinin and neuraminidase change shape -> allow virus to change shape

Question 31

Why is antigenic drift less dangerous to the host compared to antigenic shift?

Answer 31

Fragments of the outside of the virus can still be recognised by the immune system in antigenic drift (only small changes); whereas in antigen shift, there is a dramatic change in the outside structure of the virus. Virus can evade immune system

Question 32

What is antigenic shift?

Answer 32

- Results in a major change the the outside structure of the virus - Involves recombination - Results in pandemics - Only Type A are capable of antigenic shift

Question 33

Which type(s) of influenza virus are capable fo antigenic shift?

Answer 33

Type A only

Question 34

Which type(s) of influenza virus are capable fo antigenic shift?

Answer 34

Type A

Question 35

What type of specimens can be used to make a virological diagnosis?

Answer 35

Swabs, faeces, aspirates, plasma, CSF, vesicle fluids, urine

Question 36

What is PCR (polymerase chain reaction) used for?

Answer 36

To amplify target pieces of DNA for analysis

Question 37

Name 2 methods of serology

Answer 37

ELISA | Western Blotting

Question 38

Which antibody is released in the primary response?

Answer 38

IgM

Question 39

Which antibody is released in the adaptive response?

Answer 39

IgG

Question 40

What does BSE stand for?

Answer 40

Bovine Spongiform Encephalopathy

Question 41

What are the 'links' in the chain of infection?

Answer 41

1. Infectious agent 2. Reservoir 3. The portal of exit 4. The mode of transmission 5. The portal of entry 6. The susceptible host

Question 42

What is a prion protein?

Answer 42

An infectious agent devoid of nucleic acid

Question 43

What are the 3 classes of prion disease?

Answer 43

1. Infectious 2. Genetic 3. Sporadic

Question 44

How do prion proteins cause disease?

Answer 44

- Accumulation of abnormal form of a natural protein | - Conformational changes associated with specific diseases

Question 45

What is Creutzfeld-Jacob Disease (CjD)?

Answer 45

- Brain disease - Caused by accumulation of abnormal protein (prion) aggregates in the brain - No cure

Question 46

Which structural abnormality is common in infectious prions?

Answer 46

Structure tends to contain lots of beta pleated sheets (normal prion forms contain more alpha chains)

Question 47

Which unusual property of prions make them difficult to kill?

Answer 47

Resistant to thermal inactivation

Question 48

What was BSE in human populations linked to?

Answer 48

Consumption of contaminated bovine products

Question 49

What does 'iatrogenic transmission' refer to?

Answer 49

Spread of a pathogen through a medical procedure of treatment e.g. contaminated instruments, not sterilising instruments between patients