unit 6 characteristics of viruses

Question 1

filterable and how it pertains to viruses

Answer 1

viruses are small enough to pass through a filter bacteria cannot

Question 2

why are viruses considered nonliving

Answer 2

viruses have no cellular structure and depend on a host cell to survive

Question 3

naked virus vs enveloped virus

Answer 3

naked: lacks envelope and exterior is protein capsid

enveloped: capsid surrounded by plasma membrane from host cell

Question 4

why is naked virus more environmentally stable

Answer 4

enveloped viruses are damaged by anything the host cell would be damaged by

Question 5

arboviruses

Answer 5

viruses that are spread to humans through insect bite

Question 6

replication of animal viruses

Answer 6

1. attachment: adhesion molecules on capsid/envelope
   bind to host cell and absorption changes configuration
2. penetration: virus enters cell through direct, membrane fusion, or endocytosis
3. uncoating: release of genome
4. replication: replicate genome and assemble virus
5. assembly: maturation
6. release of virions: lysis or budding/exocytosis

Question 7

discuss the effects viruses can have on animal cells

Answer 7

cytopathic effects

Question 8

oncogenes

Answer 8

genes capable of causing cancer

Question 9

oncoviruses

Answer 9

viruses capable of causing cancer

Question 10

how many oncoviruses are thought to cause cancer

Answer 10

15-20% of known cancers are associated with cancers because viruses provide first step: allow for mutations

Question 11

how can viruses cause cancer

Answer 11

1. activation of proto-oncogenes –> increased expression of genes
2. viruses supresses tumor supressor proteins like p53 –> allows mutated cancer cells to proliferate

Question 12

cancer causing viruses

Answer 12

HBV/HCV –> liver cancer
HPV –> cervical cancer
EBV –> nasopharyngeal cancer

Question 13

cytopathic effect

Answer 13

cellular changes due to infection (can either be structural or morphological)

Question 14

latent infection

Answer 14

persistence of viral genome with viral replication –> dormant period

Question 15

examples of CPE

Answer 15

vacuolation (formation of vacuoles)
inclusion bodies
syncytium (membrane fuses together to produce large single cells)
cell swelling + clumping

Question 16

common methods for direct microscopic examination of virus specimens

Answer 16

electron microscopy, DFA (fluorescent antigens), nucleic acids

Question 17

collection and transport respiratory

Answer 17

swabs –> VTM + UTM

ex. influenza, RSV, adenovirus

Question 18

collection and transport GI tract

Answer 18

stool collection + swab –> VTM + UTM

ex. rotavirus and norovirus

Question 19

collection and transport lesions

Answer 19

swabs –> VTM + UTM

ex. HSV and HPV

Question 20

collection and transport blood

Answer 20

blood and bone marrow sample –> sodium heparin + EDTA

ex. HIV + enteroviruses

Question 21

collection and transport urine

Answer 21

urine collection –> VTM + UTM

ex. CMV

Question 22

collection and transport tissue

Answer 22

swabs –> VTM + UTM

ex. HSV, varicella-zoster virus, mmr

Question 23

collection and transport eyes

Answer 23

swabs + scraping –> VTM + UTM

ex. conjunctivitis and keratitis

Question 24

processing specimens for the recovery of viruses from clinical specimens

Question 25

proper storage conditions of clinical specimens collected for viral isolation

Answer 25

refrigerated at 4 degrees for up to 4 days in VTM/UTM –> frozen at -70 degrees

Question 26

direct detection of viral antigens and nucleic acids

Answer 26

antigens –> use of rapid tests which are not as sensitive and require further testing

Question 27

importance of viral culture in diagnosing viral diseases

Question 28

tubes/flasks, shell vials. and microtiter plates for growing monolayers for recovery of viruses

Question 29

3 categories of cell lines for the isolation of viruses

Question 30

strategy of serolgy in diagnosing viral diseases