Viruses Flashcards
1
Q
How are viruses classified?
A
- specificity of infection
- genome
- structures
2
Q
Outline the innate immune response
A
- non-specific
- Produces soluble factors
- Phagocytic cells
- Immediate and early
3
Q
Outline adaptive immunity
A
- Takes 1-2 weeks
- highly antigen specific
- memory based
- Activation of B+T cells
4
Q
Outline the features of influenza type A virus
A
- SSRNA virus
- Envelope virus carrying glycoproteins
- Infects birds and mammals
5
Q
What are the 2 main vaccine targets on influenza type A virus?
A
- Hemagglutinin
- Neuraminidase
6
Q
What is antigenic drift?
A
Minor antigenic changes in glycoproteins on the surface of a virus
7
Q
What is antigenic shift?
A
The abrupt and major changes in glycoprotein
8
Q
What causes antigenic drift in influenza A?
A
- Has an RNA genome
- Replication of RNA has high mutation rate
- No proofreading
9
Q
Why does the flu vaccine not work every year?
A
- The annual flu vaccine is based on predicting the HA and NA antigens
- Mutations in HA and NA surface proteins which occur may be different to the ones predicted
10
Q
How does Antigenic shift occur?
A
- Genetic reassortment of HA and NA genes occurs in an intermediate host
- This leads to recomination or reassortment of viral strains
- This often occurs when a flu strain jumps species
11
Q
Outline the features of HIV-1 retrovirus
A
- RNA envelope virus
- Replication requires reverse transcriptase
- Infects immune cells
12
Q
What type of cells does HIV infect?
A
CD4+ helper T cells
13
Q
What are the features of Reverse transcriptase?
A
- Replicates the viral RNA genome into DNA
- Not normally expressed in human cells
- Lacks 3’-5’ proofreading so high error rate
14
Q
What are impacts of reverse transcriptase not having prrofreading?
A
- Mutations accumulate
- Mutations which affect reverse transcriptase itself occur
- Affects the therapeutic outcome
15
Q
How can viral replication be inhibited with nucleoside analogues?
A
- DNA synthesis joins 3’OH of growing DNA chain to 5’ phosphate group of the incoming dNTP
- If the 3’OH is blocked (by analogues) then DNA chain growth will terminate
