Laboratory Diagnosis of Virus Infections

Virus Diagnosis

• Direct demonstration of the virus, its antigens or nucleic acid

• Virus Isolation:– Chick embryo– Cell culture (cell line)– Animal inoculation

• Serology

Direct Demonstration of virus, antigens or nucleic acid

• Cytology (CPE: cell lysis, vacuolation, syncytia, changes in cell morphology, inclusion bodies)

• Electron microscope (number of virus particles)

• Genetic Probing using tagged probes specific for a unique target sequence in the viral genome

• Direct Immunofluorescence, ELISA, RIA, latex agglutination

Virus Isolation (cell line)

• Primary cell line

• Diploid cell line

• Continuous cell lines (HeLa)

Virus Isolation (cell line)

• Virus growth is detected in cell line by

CPE, interference, hemadsorption, hemagglutination)

Serology

• Detection of antibodies to the virus

• Has limitations

• IgM, 4-fold or more increase in IgG or high fixed titre

• Neutralization, hemagglutination inhibition, ELISA, indirect fluorescent test, RIA, latex agglutination