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Principles of disease (Ross Lilley) > Introduction to viruses > Flashcards

Flashcards in Introduction to viruses Deck (18)
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1

classification of viruses

virus families can be classified according to:
-virion shape/symmetry
-presence/absence of envelope
-genome structure
-mode of replication

2

virion

complete infective form of a virus OUTSIDE the host

3

principles of viral culture

cells are inoculated with virus in vitro, the virus repicates within these cells.

4

virus structure

-lipid envelope
-spike projections from envelope
-protein capsid inside lipid envelope
-nucleic acid inside protein capsid
-virion associted polymerase attached to DNA

5

virus replication

1. virus binds membrane of host cell
2. virus is uncoated and the viral nucleic acid enters the cell
3. this nucleic acid is replicated to be incorporated into new virions
4. the viral nucleic acid is also transcribed into mRNA which then form proteins for the production of new virions.
5. the replicated viral nucleic acid and viral proteins then combine to form virions which bud off from host cell and mature.

6

Host range

the range of organisms that a virus can infect; some viruses may only infect humans, some may infect animals/birds too.

7

consequences of a viral infection

-Clearance of virus (with no, short or long term immunity)
Hepatitis C (no lasting immunity)
Measles (long term immunity)
- Chronic infection
HIV, hepatitis B, hepatitis C
- Latent infection
- Transformation (long term infection with altered cellular gene expression)
Epstein-Barr Virus, Human Papillomavirus

8

viral latency

following primary infection viruses will lie dormant in host cells. Viral genome will remain in cells but expression will be limited. Reactivation may occur.

9

mechanisms by which viruses can cause cancers

-modulation of cell cycle
-modulation of apoptosis
-reactive oxygen species mediated damage

10

modulation of cell cycle

drives cell proliferation

11

modulation of apoptosis

prevents programmed cell death

12

Reactive oxygen species mediated damage

persistent viral infections can cause inflammatory processes which lead to cancer via reactive oxygen species)

13

3 ways in which viruses can be detected

-detecting whole organism (microscopy and culture)
- detecting part of virus (antigen, nucleic acid)
-immune response to a pathogen (antibodies)

14

antiviral therapy

all antiviral agents are virustatic, none are virucidal.

15

when is antiviral therapy used?

-prophyaxis (prevent infection)
-pre-emptive (before symptoms occur but when there is evidence of infection/replication detected)
-overt (plain) disease
-suppressive therapy

16

prevention of viral infection

-Immunisation
-Prophylactic treatment post exposure
-Infection prevention & control measures
-Blood / tissue / organ screening
-Antenatal screening

17

factors that allow a virus to be eradicated

-No animal reservoir or ability to amplify in the environment
-Clearly identifiable, with accurate diagnostic tool
-No chronic carrier state
-Efficient and practical intervention, e.g. vaccination
-Political / social support

18

human virus infections of major importance

HIV
hepatitis (A,B,C,D and E)
Polio
influenza
measles
chickenpox
herpes simplex
Dengue
Yellow fever