The detection of respiratory syncytial virus in nasopharyngeal aspirates: Assessment, formulation, and evaluation of monoclonal antibodies as a diagnostic reagent

Comparisons were made between standard methods of cell culture, indirect immunofluorescence (IF) using hyperimmune respiratory syncytial virus (RSV) antiserum, and indirect IF using mouse monoclonal antibodies directed against various epitopes of RSV for the detection of RSV in nasopharyngeal aspirates. The monoclonal antibodies were used singly and in pools of different specificities which in turn were tested in both direct and indirect IF. In a preliminary study, aspirates from 227 infants were examined for RSV by standard methods. The results were compared with the detection of RSV in these aspirates using nine separate monoclonal antibodies and a pool consisting of five monoclonal antibodies. Respiratory syncytial virus was detected in 64 (28%) by cell culture, in 68 (30%) by indirect IF using bovine polyclonal antibody (BPA), and in 75 (33%) by indirect IF using the monoclonal antibody pool. The nine individual monoclonal antibodies when tested separately were less sensitive, detecting between 8 and 77% of all aspirates found to be positive by culture. After statistical analysis of the results obtained in the preliminary study, a refined monoclonal antibody pool was prepared and in a further study was tested by both direct and indirect IF in parallel with our two standard methods. Slides prepared from 303 nasopharyngeal aspirates collected between 1981 and 1984 and either tested the same day or stored at −20°C were used to evaluate these reagents. Overall agreement between the four tests was found in 274 (90%) specimens. Cell culture detected RSV in 68 (22%) specimens, indirect IF with BPA in 67 (22%), indirect IF with monoclonal antibody in 72 (24%), and direct IF with monoclonal antibody in 79 (26%). The pool of monoclonal antibodies used in direct or indirect IF was thus more sensitive than our standard methods for the detection of RSV in nasopharyngeal aspirates, and direct IF tests could be completed in 40 minutes.