MONOCLONAL-ANTIBODIES FOR THE DIRECT-DETECTION OF INFLUENZA-A VIRUS BY ELISA IN CLINICAL SPECIMENS FROM PATIENTS WITH RESPIRATORY-INFECTIONS

Background: Monoclonal antibody technology provides antibody reagents of known specificity, high titres and unlimited availability, that for m ideal reference antibodies for use in specific viral antigen-detecti on methods. Objectives: To produce mouse monoclonal antibodies against antigenic sites of influenza-A virus, and evaluate their use as diagn ostic reagents in a sandwich ELISA. Study design: (1) Production and c haracterization of monoclonal antibodies against influenza-A virus; (2 ) application of these antibodies in an ELISA method for direct antige n detection; and (3) evaluation of the ELISA as routine procedure. Res ults: Four monoclonal antibodies (A1-A4) from mice immunized intranasa lly with influenza-A virus were selected according to their specific r eactivity with either nucleoprotein or matrix protein antigens as demo nstrated by Western blot analysis. These antibodies lacked haemaggluti nation inhibition and neutralization properties and recognized both H1 N1 and H3N2 strains of influenza-A virus equally. A sandwich ELISA usi ng unlabelled antibodies for antigen capture and biotin-labelled antib odies for antigen detection was used to analyse nasopharyngeal secreti ons or nasal swabs from culture-confirmed influenza-A-infected patient s and comparable specimens from patients with other viral respiratory infections. Only influenza-A virus (strains H1N1 and H3N2) could be de tected in samples from patients with known influenza-A and influenza-B infections, and also after re-isolation of such viruses in convention al cultures of MDCK cells or embryonated hens' eggs. The antigen-detec tion assay showed a diagnostic sensitivity of 100% and a specificity o f 98.3% compared with conventional culture methods. Conclusion: The re ported ELISA appears to be a rapid and inexpensive method for diagnosi s and epidemiological studies of influenza-A infections.