Systemic Virology

Question 1

What are the 3 types of investigation for viral infections?

How can each of these be carried out?

Answer 1

ELISA testing (enzyme-linked immunosorbent assay)

Serotyping

Genotyping

• DNA sequencing
• Real time PCR

Question 2

Briefly outline the process of an ELISA test. (3)

Answer 2

1. Antigen is attached to a surface (usually a polystyrene microtiter plate)
2. A specific antibody is washed over the surface, so that it binds to the antigen
   a. This antibody is bound to an enzyme
3. A substance is added which, when bound to the enzymes on the antibody, will convert to create a detectable signal (e.g. colour change)
   a. Therefore, you will be able to see if the enzyme is present or not

Question 3

List 6 viral infections for which an ELISA test is used for diagnosis.

Answer 3

HIV
Hepatitis B (surface antigen)
Hepatitis C virus
Rubella IgG
Cytomegalovirus IgG
Epstein-Barr virus IgM

Question 4

Briefly outline the 3 stages of PCR.

Answer 4

1. Denaturation - DNA heated to separate strands
2. Annealing - cooling and addition of primers
3. Extension - DNA polymerase creates new DNA strands from primers