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Flashcards in Introduction to Viruses Deck (32)
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1

What three categories can viruses be placed into

Icosahedral - have 20 faces with each being an equilateral
Helical - the protein binds around DNA/RNA in a helical fashion
Complex - neither icosahedral or helical

2

Where do viruses replicate

Inside the host cell as they are obligate intracellular pathogens

3

Viruses are...

non-cellular and small

4

How can viruses be classified

Order
Family
Genus
Species
(in this order)

5

What factors are looked at when determining virus families

Virion shape/symmetry
Presence/absence of envelope
Genome structure
Mode of replication

6

Describe the structure of viruses

They have:
Spike projections
Lipid envelope
Protein caspid
Virion associated polymerase
Nucleic acid

7

How do viruses replicate

The viruses undergoes:
Maturation
Attachment
Uncoating
Replication of genomic nucleic acid (either through mRNA synthesis or genomic nucleic acid synthesis)
Protein synthesis
Virus proteins are inserted into the membrane
Virion is assembled
Budding and release

8

What is host range in viruses

Some viruses may only infect humans while others can also infect other animals/birds

9

What can the coinfection of human and animal/bird strains in one organism cause

The recombination and generation of a new strain

10

What can a viral infection cause

Clearance of a virus with: no, short or long-term immunity
Chronic infection (e.g. HIV, Hep B)
Latent infection
Transformation

11

What is transformation

Long-term infection with altered cellular gene expression (e.g. EBV)

12

Give an example of a disease which shows viral latency

Herpes Simplex Virus
Varicella Zoster Virus

13

What is viral latency

When viruses stay dormant in the host cell after a primary infection.
The full viral genome is present but its expression is restricted

14

What is reduced in viral latency

Number of viral antigens present
No viral particles produced

15

Where is reactivation most likely to occur

Immunocompromised patients

16

How can viruses lead to cancer

By:
Modulation of cell cycle control - to drive cell proliferation
Modulation of apoptosis - prevents apoptosis
Reactive oxygen species mediated damage - some persistent viral infections can cause persistent inflammatory processes which lead to cancer via reactive oxygen species

17

Give examples of viruses which can lead to cancer

EBV - leading to Hodgkin’s lymphoma, nasopharyngeal carcinoma and post-transplant lymphoproliferative disease
Human herpes virus 8 - leading to Kaposi's sarcoma, primary effusion lymphoma, Castlemans's disease
HPV - cervical, anal oropharyngeal cancers

18

What parts of a virus can be dectected

Whole organism
Part of organism (e.g. antigen, nucleic acid)
Immune response to a pathogen (e.g. antibodies)

19

How can the whole viral organism be detected

Microscopy
Culture

20

How can part of the viral organism be detected

Antigen dectection
DNA/RNA dectection
Extraction of genetic material from sample
Amplification of region of target organism genome

21

What can an immune response be used to determine

An acute/recent infection
Prior infection/response to vaccination

22

Are antiviral agents virustatic or virucidal

Virustatic

23

When is antiviral therapy used

Prophylaxis - to prevent infection
Pre-emptive therapy -
when there is evidence of infection/replication but before symptoms begin
Overt disease
Suppressive therapy - to keep viral replication below the rate which causes tissue damage in an asymptomatic infected

24

How can viral infections be prevented

Vaccinations
Passive immunisation with immunoglobulin
Prophylactic treatment post exposure
Infection prevention and control measures
Blood/tissue/organ screening
Antenatal screening

25

What infection prevention and control measure can be put into place

Isolation of symptomatic patients
Personal protective equipment
Safe use and disposal of sharps

26

Give examples of viruses which can be eradicated

Small pox (eradicated in 1979)
Measles
Polio

27

What properties do viruses require to potentially be eradicated

They should:
Have no animal reservoir or ability to amplify in the environment
Be clearly identifiable, with accurate diagnostic tools
Have no chronic carrier state
Have efficient and practical intervention, e.g. vaccination
Have political/social support

28

How are viruses classified

Shape
Presence of envelope
Genome structure
Mode of replication

29

What cancer is hepatitis B associated with

Hepatocelluar carcinoma

30

What is S. aureus common cause of

Skin and soft tissue infections