Detection of rubella virus-specific immunoglobulin G in saliva by an amplification-based enzyme-linked immunosorbent assay using monoclonal antibody to fluorescein isothiocyanate

An immunoglobulin G (IgG)-capture enzyme-linked immunosorbent assay (ELISA) for rubella virus is described. The assay uses a fluorescein isothiocyanat e (FITC)-anti-FITC amplification system. The detection limit of the ELISA w as approximately 7 IU of rubella virus-specific IgG per mi of serum sample. For saliva samples the performances of the capture ELISA and previously de scribed radioimmunoassay were assessed, and the results of those two assays were compared to the rubella virus-specific IgG result obtained by a comme rcial ELISA (Behring Enzygnost) with a panel of paired serum and saliva sam ples. This comparison showed that the capture ELISA with saliva was more se nsitive than the radioimmunoassay and that the results correlated better wi th the serum IgG result than the results of the radioimmunoassay did, with an overall sensitivity of 82% and a rank correlation of 0.68, whereas the s ensitivity and rank correlation for the radioimmunoassay were 74% and 0.45, respectively. For subjects of 10 years of age or younger, the ELISA with s aliva had a sensitivity of 94% and a specificity of 100% compared to the re sults of the ELISA (Behring Enzygnost) for rubella virus-specific IgG with corresponding serum samples. The sensitivity was much lower for subjects ag es 17 years or older. The assay may have wider epidemiological use with sal iva specimens, particularly those from children.