Methods of Laboratory Diagnosis
Laboratory diagnosis of viral infections can be carried out by many methods. These methods include
(a) demonstration of virus-induced cytopathic effects (CPEs) in the cells,
(b) direct detection of viruses,
(c) virus isolation and viral assays,
(d) detection of viral proteins and other enzymes,
(e) detection of viral genome, and
(f) viral serology (Fig. 53-1).
Detection of Viral Proteins and Other Enzymes
During replication of viruses in host cells, viral proteins, antigens, and other enzymes are produced. These viral products and com-ponents can be detected by many methods including biochemical, immunological, and molecular methods in clinical specimens.
Enzyme-linked immunosorbent assay (ELISA), direct immu-nofluorescence assay, and radioimmunoassay (RIA) are widely used methods. These methods are used for detection and identi-fication of viruses and viral antigens in clinical specimens, as well as in cell cultures. These tests use specific monoclonal or mono-specific antibodies that are raised against specific viral antigens.
Identification and quantification of specific virus can also be carried out by detection and assay of characteristic viral enzymes. For example, detection of reverse transcriptase in serum or cell culture suggests the presence of a retrovirus. Similarly, demonstration of hemagglutinins or hemadsorption in the cell culture indicates the presence of influenza virus.