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

Abstract

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 (human) specimens containing influenza type A and adenovirus. Polystyrrene microtiter wells were the solid phase and were coated with virus-specific guinea pig Ig. Specimens were added; bound viral antigens were detected by addition of virus-specific rabbit Ig followed by enzyme-labeled goat antirabbit IgG. Two methods of labeling goat anti-rabbit IgG 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 103.5 50% tissue culture infectious doses [TCI] of influenza type A and 103.8 50% TCI of adenovirus. Equal sensitivity was noted with alkaline phosphatase-labeled goat anti-rabbit IgG. An increase in sensitivty of 3- to 6-fold was achieved when virus-specific rabbit Ig and conjugate were diluted in 1% gelatin. The solid-phase, double-antibody enzyme immunoassay detected influenza type A and adenovuris in isolation-positive clinical specimens with 53% (21/40) and 62% (13/21) efficiency, respectively. The solid-phase, double-antibody enzyme immunoassay apparently 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.