Enzyme-linked immunosorbent assay to assess respiratory syncytial virus concentration and correlate results with inflammatory mediators in tracheal secretions

Objective. We developed an enzyme-linked immunosorbent assay (ELISA) for th e quantitation of respiratory syncytial virus (RSV) in respiratory secretio ns in intubated patients infected with RSV. Methods. We compared the quantitative ELISA and a standardized plaque assay in intubated children <2 years of age who were mechanically ventilated for severe RSV disease and enrolled in a randomized double blind placebo-contr olled treatment trial of a monoclonal antibody to the F protein of RSV (pal ivizumab; Synagis). We also examined the relationship between the concentra tions of virus as measured by ELISA and of three inflammatory indices in re spiratory secretions (white blood cell count, myeloperoxidase and eosinophi lic cationic protein). Results. Quantitative ELISA and plaque assay were highly correlated for bot h tracheal aspirates (r = 0.67, P = 0.001) and nasal wash specimens (r = 0. 75, P = 0.001). Treatment with palivizumab significantly neutralized RSV in tracheal aspirates as measured by plaque assay. in contrast quantitation o f RSV by ELISA was not affected by palivizumab treatment. This finding is c onsistent with results that were obtained in preliminary studies of RSV-con taining media treated with monoclonal antibody, where we found that the ELI SA measured virus whether antibody-hound or not. The inflammatory indices w ere not correlated with RSV concentration measured by ELISA or plaque assay . Conclusions. We conclude that this quantitative ELISA is a potentially usef ul tool for measurement of RSV concentration in respiratory secretions that may help elucidate the pathophysiology of acute RSV infection. Specific an tiviral strategies for the treatment of RSV disease could be evaluated by t his method.