Diagnosis of Viral infections Flashcards
(23 cards)
What is Virus Isolation?
Grow virus in lab, Virus needs to have cells to grow.
What are the advantages of virus isolation?
Amplified.
What are the disadv of virus isolation?
Need to suspect virus, need time, some viruses cannot be cultured.
What is Electron Microscopy? What does it identify about viruses?
Uses negative staining under a microscope. Detects virus morphology.
What are the adv of Electron microscopy?
Used for viruses that can’t be cultured, identify new virus.
What are the disadv of electron microscopy?
Specialised equipment and personell, Low sensitivity.
What is PCR?
Viral nucleic acid detected, and can be amplified.
What are the adv of using PCR?
Very sensitive, doesn’t require live virus, specific.
What are the disadv of using PCR?
Contamination
Outline how an Antigen Elisa is done.
Capture antibody used to detect antigen, then enzyme labelled antibody put it. Substrate changes colour if ELA has bound.
Advantages of Antigen Elisa
Fast, No live virus required, specific
Disadv of Antigen Elisa
No amplification, not specific
What are the three important immunoassays? What do they detect?
Immunofluorescence assay, Immunoperoxidase assay, Immunochromotography. All detect antigen.
How is an Immunofluorescence assay carried out?
Virus detected using antibody with fluorescent particle attached which binds to antigen.
How is an Immunoperoxidase assay carried out?
Elisa on a slide. ELA used to detect antigen, substrate changes colour if it has bound.
How is an Immunochromatography carried out?
Labelled antibody added, and then run on chromatography. Antibody at test line will capture antibody will capture antigen if it’s present, labelled antibody then can be identified.
What are the adv and disadv of Immunoassays?
+ Fast, no live virus, specific
- No amplification, low sensitivity
To identify host immune response, how many samples is ideal? When would you take these? What do you test for?
2 samples ideal: One when showing clinical signs, and one 2-3 weeks later. Test for IgG.
What is a Neutralisation assay? What does it test for?
Serum sample should neutralise virus and prevent cell death if there are antibodies present. Tests for host immune response.
What is a Haemagglutinin inhibition assay? What does it test?
Some viruses agglutinate RBC. If antibody present, the virus cannot agglutinate.
What is a positive haemagglutinin inhibition assay?
Antibodies present - dot appearance.
What is a negative haemagglutinin inhibition assay?
Larger dot - no antibodies/
What are the adv and disadv of antibody detection?
+ Cheap, specific, sensitive.
- Retrospective, negative may mean still in lag phase.
