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Fundamentals of Diagnostics Exam 2 > Virology > Flashcards

Virology Flashcards

1
Q

what antibodies do we usually test for

A

usually IgG, but sometimes IgM. IgM takes longer to develop

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2
Q

what is a direct ELISA

A

antigen on plate and patient antibody binds. an enzyme allows visualization

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3
Q

what is indirect ELISA

A

antigen on plate. patient antibody binds then a secondary antibody conjugate is added for visualization

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4
Q

what is a competitive ELISA

A

antigen on plate. patient antibody binds. then an inhibitor antigen binds to decrease color reaction. so, less of a reaction on the plate means more host antibody is present. opposite from other ELISAs

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5
Q

describe titers

A

using ELISA testing, sample is diluted in a serial manner until no reaction occurs. the last well with a reaction is your titer

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6
Q

what is lateral flow assay

A

SNAP tests. may test for antigen or antibody

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7
Q

what is agar gel immunodiffusion? examples of its use?

A

antigen in middle. samples and controls in a circle around it. positive samples will have a white line near it. very reliable. gold standard
ex: coggins

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8
Q

what is a hemagglutination inhibition test

A

some viruses bind RBCs and prevent agglutination. serum is added and if antibodies are present, they will stop the virus from binding and allow the blood to clot. gold standard

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9
Q

what is a plate agglutination test

A

mix serum with stained antigen and form clumps if there is antibody. larger clumps with more antibodies

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10
Q

what viral protein is usually tested for

A

spike proteins

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11
Q

what is a capture/sandwich ELISA

A

antibody fixed to plate. antigen present in serum binds the antibody. add another label antibody for visualization.
useful for BVD where patient wouldn’t have antibody

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12
Q

what is fluorescent antibody testing? what is it used for?

A

direct method. fluorescent labeled antibodies bind target antigens in fresh tissue. look under fluorescent microscope.
ex: rabies

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13
Q

what is immunohistochemistry? what is it used for?

A

like IFA, but use fixed tissue. expose tissue to antibody then visualize under a normal scope. see the effect of virus in tissues, can see viral inclusions in the cell (usually pathopneumonic)
ex: FIP, marek’s dz

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14
Q

what are the pros and cons of ELISAs and lateral flow assays

A

pro - quick, less expensive, readily available, some done in clinic, can get titers with ELISA
cons - less specific/risk of false positives/negatives (esp with lateral flow), not as likely to be accepted for regulatory purposes, cross reactivity possible

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15
Q

what are the pros and cons of AGID (agar gel immunodiffusion) and HIs (hemoagglutination inhibition)

A

pros - specific, gold standard for some tests, often accepted for import/export
cons - harder to find, longer incubation, labor intensive, often more expensive

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16
Q

what are the pros and cons of fluorescent antibody tests and immunohistochemistry

A

pros - both usually quite specific, visualize pathogen location, FA is fast, IHC is an option for fixed tissue
cons - rarely an antemortem test, can be expensive, may be species specific, limits assays

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17
Q

differentiate antigen vs antibody tests

A

antigen - detect current infection, detects in immunocompetent animals
antibody - detect previous/chronic infection, detects vaccination that elicits IgG

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18
Q

what is the benefit of real-time PCR

A

it quantifies viral load

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19
Q

what does a higher Ct value mean in PCR

A

more cycles for the sample to break through the threshold, so less virus present

20
Q

what is a multiplex panel

A

PCR panel for multiple viruses that cause similar signs

21
Q

what is whole genome sequencing

A

done on a pure viral sample. usually used for epidemiology and research

22
Q

what is metagenomic sequencing

A

start with a mixed sample and sequence everything in it. computer helps analyze the data

23
Q

what are pros and cons for PCR

A

pros - fast, sensitive, reliable
cons - no distinction btwn live and inactive, may miss if virus mutates, contamination issues, need to know what you’re testing for

24
Q

what are the pros and cons for sequencing

A

pro - large amount of data, ID unknown pathogens, track mutations
cons - expensive, lots of analysis, best on pure samples

25
Q

describe viral isolation

A

grow virus from diagnostic sample to identify, gold standard, only test to prove viable virus is present

26
Q

what media are used for viral culture

A

embryos and special cell lines. cell lines should be similar to tissue the virus infects

27
Q

how do you know virus is growing on your culture

A

usually thru cytopathic effects or electron microscopy
can also use fluorescent antibody test, hemagglutination, PCR, sequencing

28
Q

what is cytopathic effects

A

damage done by viruses on cells

29
Q

why might you use virus isolation

A

with low viral load, unknown pathogens, and for species without serological or molecular tests

30
Q

describe electron microscopy

A

stained with heavy metal salts to visualize surface structures, can search blindly, can detect primary and secondary pathogens

31
Q

T/F: if you don’t see inclusion bodies on a group of cells, there are no viruses present that can cause inclusion bodies

A

F - usually only present at certain stages of disease

32
Q

pros and cons of virus isolation

A

pros - detect living viruses, detect and identify unknown viruses, sensitive, amplify and collect live virus
cons - difficult, long wait time, expensive, sensitive to contamination

33
Q

pros and cons of electron microscopy

A

pros - visualize pathogen, work even if mutated, false positives rare, see all actors involved
cons - expensive, less common, longer turnaround time, may pick up an innocent bystander

34
Q

pros and cons to histopath

A

pros - false positives unlikely, inclusions often distinct and pathognomonic, virus inactivated so no risk of spread
cons - absence of inclusions ≠ negative, longer turnaround time

35
Q

what kind of swabs should not be used for viral testing

A

wood - antiviral, interferes with PCR
calcium alginate - interferes with viral isolation and PCR testing

36
Q

what kind of swabs pick up more virus

A

flocked - has bristles

37
Q

with a case of avian influenza where you are trying to decide if it is safe to bring in new birds, which test should you use to be sure your flock is virus free?
a. lateral flow assay
b. real time PCR
c. virus isolation

A

c is best. tells if any viable virus present

a- quick, but risk of false positives
b- sensitive, but detects inactivated virus as well as live. would be ok, but would end up waiting longer than necessary to bring in new birds

38
Q

what test is accepted from the regulatory bodies for avian influenza

A

virus isolation

39
Q

how much tissue is needed for viral testing

A

not a lot. a few grams

40
Q

what test should be used with a herd of cattle with respiratory illness

A

PCR resp panel. histology helpful but may not be diagnostic

41
Q

you have a cat with clinical signs consistent for FIP. a fecal sample is PCR positive for coronavirus. does this cat have FIP?

A

not necessarily. normal coronavirus and FIP are both shed in the feces

42
Q

is PCR, fluorescent antibody test, or lateral flow assay helpful in testing for FIP

A

no, do not differentiate typical coronavirus from FIP

43
Q

does a FCoV negative ELISA mean this cat does not have FIP

A

no. in late stage FIP, antibodies drop and may not be detected. serum testing not helpful for FIP

44
Q

an abdominal fluid sample is PCR positive for coronavirus. does this cat have FIP

A

not definitive, but is suggestive. good enough to act on this.
histopathology and immunochemistry on biopsy tissues are more definitive than PCR

45
Q

how should whole fish be sent to the lab

A

overnight on ice packs or dry ice.
not formalin b/c inactivates virus. not with ground shipping or just an insulated envelope. will rot

Fundamentals of Diagnostics Exam 2 (5 decks)

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