Enzyme immunoassay for direct detection of influenza type A and adenovirus antigens in clinical specimens.

Detection of viral antigens in specimens without prior cultivation in cell culture provides the most rapid method for specific viral diagnosis. A solid-phase, double-antibody enzyme immunoassay was developed for this purpose and tested with clinical specimens containing influenza type A and adenovirus. Polystyrene microtiter wells were the solid phase and were coated with virus-specific guinea pig immunoglobulins. Specimens were added, and bound viral antigens were detected by addition of virus-specific rabbit immunoglobulins followed by enzyme-labeled goat antirabbit immunoglobulin G. Two methods of labeling goat anti-rabbit immunoglobulin G with horseradish peroxidase were investigated: covalent attachment and a noncovalent, immunological binding of antibody to enzyme, the peroxidase-antiperoxidase method. Both methods of labeling resulted in assays that could detect 10(3.5) 50% tissue culture infectious doses of influenza type A and 10(3.8) 50% tissue culture infectious doses of adenovirus. Equal sensitivity was noted with alkaline phosphatase-labeled goat anti-rabbit immunoglobulin G. An increase in sensitivity of three- to sixfold was achieved when virus-specific rabbit immunoglobulins and conjugate were diluted in 1% gelatin. The solid-phase, double-antibody enzyme immunoassay detected influenza type A and adenovirus in isolation-positive clinical specimens with 53% (21/40) and 62% (13/21) efficiency, respectively. The solid-phase, double-antibody enzyme immunoassay has considerable potential as a practical and rapid method for detection of respiratory viral antigens in nasal wash and throat swab specimens. For optimal value, however, greater sensitivity than was provided by the present methods is desirable.