Detection of antibodies to respiratory syncytial virus attachment and nucleocapsid proteins with recombinant baculovirus-expressed antigens.

The ability to measure antibodies against individual respiratory syncytial virus (RSV) proteins is important in the analysis of immune responses to RSV. We expressed the nucleocapsid (N) protein and the group A and B RSV attachment (G) proteins from recombinant baculoviruses. The three recombinant RSV proteins were used individually in an enzyme-linked immunosorbent assay (ELISA; bac-ELISA for results from assays of all three proteins). The bac-ELISA results were compared to the results obtained by a whole-virus ELISA (RS-ELISA for results from assays of both group A and B viruses). Antibody samples from 113 children were tested. The determination of seronegative or seropositive status by the bac-ELISA was compared to the same determination by the RS-ELISA; the sensitivity of bac-ELISA was 87% (95% confidence interval [CI], 78 to 93%), the specificity was 82% (CI, 59 to 94%), and the positive and negative predictive values were 95% (CI, 86 to 98%) and 60% (CI, 41 to 77%), respectively. The group specificity of the G-protein ELISA was confirmed by testing antibodies from experimentally immunized animals. Thus, the bac-ELISA was shown to be comparable to the whole-virus ELISA in detecting antibody responses to RSV, while it offered the advantage of measuring specific antibody responses to individual RSV proteins.