Virology

Question 1

def. of virus

Answer 1

broad general term for any aspect of the infectious agent which includes: infectious or inactivated particle, viral nucleaic acid and protein in infected cell

Question 2

def. of virion

Answer 2

complete intact virus particle outside of the cell

Question 3

def. viroid

Answer 3

short stretch of circular single stranded RNA without a protein coat

Question 4

what can virus be seen with

Answer 4

electron microscope

Question 5

what is virus structre

Answer 5

core of nucleic acid surrounded by protein coat +/- evelope

Question 6

3 different options for nucleic acids in viruses

Answer 6

1. DNA or RNA
2. single or double stranded
3. linear/circular

Question 7

what proteins are in viruses

Answer 7

1. structural - capsid made of capsomeres

2. enzymes - few, differ from host cell

Question 8

what is significance of virus enzymes

Answer 8

target for drugs

Question 9

what is envelope made from

Answer 9

cell as it pushes out

Question 10

5 different morphologies of virus

Answer 10

1. helical/tubular - +/- envelope
2. icosahedral - +/- envelope
3. complex

Question 11

what is enveloped cubic virus for sure

Answer 11

herpesviridae

Question 12

4 ways to class viruses

Answer 12

1. type and stucture of viral nucleic acid
2. strategy used in replication - site
3. type of symmetry of virus capsule
4. presence of envelope

Question 13

what are virus families

Answer 13

similar structural, genomic and replication properties (suffix viridae)

Question 14

what are virus genera

Answer 14

subdivisions of families (suffix: virus)

Question 15

what are genera subtypes based on

Answer 15

nucleotide sequences and antigen reactivities

Question 16

6 DNA viruses - rest are RNA

Answer 16

1. Hep B
2. HPV
3. parvovirus
4. herpes
5. adenovirus
6. polyoma viruses

Question 17

viral replications steps (7)

Answer 17

1. adsorption (attachment)
2. entry
3. uncoating
4. transcription
5. synthesis
6. assembly
7. release

Question 18

how do viruses attach

Answer 18

• random collision
• interaction between specific proteins on virus and on surface of cell
• able to only infect a limited range of cells

Question 19

2 mechs. of virus entry

Answer 19

1. endocytosis

2. fusion of envelope with cell

Question 20

how do virus uncoat

Answer 20

cell enzymes strip capsid - no longer visible

Question 21

2 things that must be synthesized

Answer 21

1. proteins (structural and enzymes)

2. nucleic acids - new virus genome

Question 22

where do DNA virus do their replications

Answer 22

• DNA in nucleus
• protein in cytoplasm
• move proteins into nucleus for packaging

Question 23

2 types of RNA viruses and how they replicate

Answer 23

+sense - actas a mRNA and can make proteins immediatelly

-sense - must first make a +sense using viral enzymes and then copy

Question 24

how do retroviruses work

Answer 24

contain reverse transcriptase

• +sense RNA > cDNA > integrated directly into the host chromosome
• virus doens’t need to do any work

Question 25

2 ways of release

Answer 25

1. bud out | 2. rupture cell

Question 26

2 ways virus may cause damage

Answer 26

1. directly | 2. through host reactions to the virus

Question 27

2 factors that affect the outcome of viral infections

Answer 27

1. host's defences | 2. virulence factors

Question 28

4 possible outcomes of a virus-host cell interaction

Answer 28

1. cell death - lytic 2. cell transformation - cancer or malignancy 3. latent infection - may reactivate any time to cause disease, may have continuous or intermittent shedding 4. cell fusion to form nucleated cells - HIV

Question 29

5 possible ways viruses evade the immune system

Answer 29

1. antigenic variation - keep switching 2. encode receptors for inflammatory cytokines - shutting down imune system 3. reduce expression of MHC-class 1 - reducing ability of T cells to kill 4. direct cell to cell propagation 5. attenuation

Question 30

3 types of persistent viral infections (some overlap)

Answer 30

1. chronic carrier - chronic illness due to continuous shedding 2. latent infection - may pop back up and may shed 3. slow virus infections - due to prolonged incubation periods

Question 31

2 routes of viral transmission

Answer 31

1. horizontal - person to person | 2. vertical - mother to fetus

Question 32

when can transmission occur

Answer 32

1. with or without disease 2. during asymptomatic shedding 3. during incubation period

Question 33

what are some epidemiological aspects that change viral outcomes

Answer 33

1. mode of tranmission 2. age 3. gender 4. ethnicity 5. travel Hx 6. occupation 7. season 8. medical conditions

Question 34

what is incubation time

Answer 34

time from infection to dev. of Sx

Question 35

2 short incubation virus (1-2 days)

Answer 35

GI and resp viruses

Question 36

3 medium incubation viruses (1-3 weeks)

Answer 36

1. MMR 2. VZV, HSV 4. enteroviruses, polio

Question 37

4 long incubation viruses (months)

Answer 37

heps, HIV, EBV, rabies

Question 38

some non-specific host defences

Answer 38

- skin - rest tract, cilia, mucous - GI - acid, lymphoid - GU- flow tears - phago - interferons

Question 39

what does humoral do

Answer 39

- Ig - neutralize viruses - elimination of viruses

Question 40

3 main Igs in virus infections

Answer 40

IgM - early - 1week to 6 months IgG - months to years, responsible for immunity IgA - dimer of 2 Igs, body secretions, mainly for GI

Question 41

what does cellular defense do

Answer 41

- elim of virus infected cells | - most important defence

Question 42

6 cell mediated types and functions

Answer 42

Th - stim cytotoxic response and activate B cells Ts - control and reg. response by supressing Th Tc - cytotoxic - min cells to kill virus infected cells Td - delayed hypersentitivity cell - release macrophage activating factor NK - direct killing of infected cells interleukins - modulate immune response

Question 43

5 times rapid and accurate diagnosis is important

Answer 43

1. tranplant 2. HIV 3. effective chemo 4. epidemiology 5. transplant safety

Question 44

3 methods to diagnose viruses

Answer 44

1. isolation (culture) 2. direct detection 3. serology (AB/antigen)

Question 45

3 methods of culture

Answer 45

1. tissue culture 2. chick embryo 3. animal innoculation

Question 46

how must viruses be samples

Answer 46

quickly and in a cool special medium

Question 47

2 adv. of cuture

Answer 47

1. definitive | 2. obtain isolate for further tests

Question 48

3 disadv. to culture

Answer 48

1. not all viruses cultruable 2. may take long time 3. biohazard

Question 49

how is direct detections done (3)

Answer 49

1. look at the sample with electron microscope 2. look for monoclonal ABs against 3. PCR for viral DNA/RNA

Question 50

what is serology tests

Answer 50

look for ABs against

Question 51

4 ways to diagnose in serology

Answer 51

1. IgM ABs 2. four fold rise in AB titre 3. seroconversion 4. very high single AB titre (unreliable)