1. LAB. DIAGNOSIS OF VIRUSES
5 methods are used for diagnosis in the virology laboratory:
Direct microscopy
Cultivation of viruses
Serology
4. Detection of viral antigens
5. Detection of viral nucleic acids

3. DIRECT MICROSCOPY @ Three procedures can be used :
1. Light microscopy: to reveal inclusion
bodies or multinucleated giant cells
e.g. herpesvirus
2. Immunofluorescence microscopy: to
read viral fluorescent antibodies
3. Electron microscopy: to detect virus
particles

5. Cultivation of Viruses
Inoculation of fertile: Specimen is injected in day-old eggs. Three days later eggs are opened to see spots on membranes and fluids.
Inoculation of lab. Animals: Specimen is injected in 2 day-old suckling mice, and look for clinical signs in mice.
3. Viral tissue culture

7. VIRAL TISSUE CULTURE @ Transport specimen in Hank’s medium
or store at 4 °C immediately
@ Virus growth in living cells produces a
Cytopathic Effect (CPE) .
@ Identification depends on :
* time taken for the CPE to appear
* type of cell present in CPE

9. If no CPE, virus is detected by:
Hemadsorption Test: For viruses with hemagglutination antigens, eg mumps, and influenza viruses
2. Interference Test: Formation of CPE by another virus, eg Rubella which does not cause CPE, but it can cause CPE when ECHO virus is added to the cell culture

11. 3. Phenol red indicator changes yellow: This is due to decrease in acid production when the infected cells die in medium
4. Phenol red indicator remains red (alkaline): This is used to detect Eenteroviruses

13. 5. Use of a known antibody and made to react with the virus antigen in the cell culture by one of the following tests :
1) Complement Fixation Test .
2) Hemagglutination Inhibition Test
3) Neutralization Test.
4) Fluorescent-Antibody Test

15. 5) Radioimmunoassay Test.
6) Enzyme-Linked Immunosorbent
Assay (ELlSA) Test.
7) Immunoelectron microscopy
Test

17. SEROLOGY @ Blood is collected twice: at the
acute stage and days later
@ If the antibody titer in second sample is at least 4-fold higher than the titer in the acute stage sample, patient is considered to be infected.

19. @ IgM antibody only is used to diagnose
acute infection, e g infection by
hepatitis B virus.
@ Tests used are: Complement fixation, Hemagglutination-inhibition, ELlSA, Neutralization, Radioimmunoassay, and
Fluorescent-antibody tests
@ Heterophile non-specific agglutination
antibody test: can be used to detect
Epstein-Bar virus

21. DETECTION OF VIRAL ANTIGENS
@ Detected in patient's blood
or body fluids by ELISA.
@ Examples :
* p24 antigen of HIV
* HBs antigen of Hepatitis B

23. DETECTION OF VIRAL NUCLEIC ACIDS
@ DNA,RNA, & mRNA are detected in
blood or tissues by polymerase chain
reaction (PCR), using DNA or RNA
probe
@ For small amounts of N.A., amplify
these N.A. by PCR.