Viral Diagnosis by Immunofluorescence

Abstract

The main use of immunofluorescence in both human and veterinary virology should be for the rapid detection of antigen at site of lesion. For human disease WHO has strongly recommended immunofluorescence for rapid diagnosis of respiratory infection by detecting virus in nasopharyngeal secretions, and in the absence of an electron microscope for the investigation of skin and eye scrapings and brain biopsies. The principle of the technique and its methodology are briefly outlined and the use of conventional, egg-derived and monoclonal antibodies discussed. Some further advantages of the immunofluorescence technique are mentioned such as the investigation of outbreaks of respiratory disease in an animal house, the detection of antigen in secretions after infectivity of virus is lost, investigation of post-mortem specimens, control of cross-infection and diagnosis of infection at a distance from the virus laboratory. The major criticism of immunofluorescence is its labour intensiveness, which is balanced by its increased sensitivity and so far comparisons with alternative techniques such as ELISA have confirmed this increased sensitivity. Conjugated-staphylococcal protein A would appear to have no part in this technology as discussed and little information is available on the use of biotin-avidin as a detection system. Automation of reading fluorescence has been attempted by use of time-resolved fluoroimmunoassay, but it is too early to judge whether this technique is sufficiently practical, reproducible and economic for universal use.