Lab 3.1 Only

Question 1

What are the main purposes of virus detection?

Answer 1

§ Clinical cases - need for a specific diagnosis
§ Certification of freedom from specific infection
§ Disease status prior to artificial insemination, embryo transfer, blood transfusion
§ Tracking zoonoses
§ Xenotransplantation for humans

Question 2

The primary purpose of virus isolation is:

Answer 2

1. To isolate and identify viruses in clinical samples
2. To do research on viral structure, replication, genetics and effects on host cell
3. To prepare viruses for vaccine production

Question 3

Cytopathic effect (CPE) shows what signs?

Answer 3

-Rounding and clumping of cells
-Vacuolation
-Fusion of cells
-Syncytia or giant cells

Question 4

advantages of virus isolation

Answer 4

• Supply of virus for further characterization
• Production of vaccines and other diagnostic tests

Question 5

disadvantages of virus isolation

Answer 5

• Time consuming and technically demanding
• Some viruses cannot be propagated
• Need to have an idea of what virus you are isolating to choose the “right” cells for growth

Question 6

methods for virus visualization

Answer 6

• Indirect visualization using light microscope
  > Cell culture: cytopathic effect
  > Histology: inclusion bodies
• Direct visualization of the virus in transmission Electron Microscopy (EM)
• Can provide size and shape of particles
• Cannot provide specific information about the virus

Question 7

disadvantages to virus visualization

Answer 7

• Expensive equipment and trained staff
• It needs high concentrations of viral particles
• Not accessible to vet clinics

Question 8

Direct virual detection methods, vs indirect

Answer 8

Direct:
-Virus visualization
-Antigen detection
-Detection of viral nucelic acid genomes

Indirect
-Antibody tests (serological)

Question 9

what it means if we directly detect viral protein in the host, and
Methods for direct detection of viral proteins (antigens)

Answer 9

Detecting viral protein is a good indicator that the pathogens is still present in the host

-Immunofluorescence: Fluorescence Antibody Test (FA)
-Immunohistochemistry
-ELISA: Enzyme - linked Immunosorbent Assay for antigen detection

Question 10

methods for direct detection of viral nucleic acids in host, and why this is useful

Answer 10

If virus is still present in an animal, its genetic material may be detectable!
- Polymerase chain reaction (PCR)
-Sequencing

Question 11

difference between immunofluorencence and immunohistochemistry techniques

Answer 11

-immunofluorescence uses biopsy, immunohistochem uses histological slide

Question 12

how does direct ELISA work?

Answer 12

• Looking for viral PROTEINs (antigens) (direct ELISA)

Question 13

The most versatile, rapid, sensitive and specific test for virus diagnosis

Answer 13

PCR - direct detection of nucleic acids

Question 14

purpose of serological tests for virus diagnosis

Answer 14

indirect detection
-Detection of antibodies (host response) against a virus -Indicate the host exposure to the virus

Question 15

best serological tests for viral exposure

Answer 15

• ELISA (indirect)
• Virus neutralization

Question 16

how does indirect elisa work

Answer 16

looking for host antibody in the specimen

• Harvest serum from animal, dilute and add to a well in a plate coated with a known viral protein (antigen)
• Detect virus-specific antibody (e.g., IgG) with labeled anti-IgG antibody containing an indicator (e.g., alkaline peroxidase)
  > add substrate and look for color change

Question 17

direct vs indirect ELISA

Answer 17

direct looks for antigen, indirect looks for host antibodies