Recombinant nucleoprotein-based serological diagnosis of Crimean-Congo hemorrhagic fever virus infections.

An enzyme-linked immunosorbent assay (ELISA) using recombinant nucleoprotein (rNP) was reported for the detection of immunoglobulin G (IgG) antibodies to Crimean-Congo hemorrhagic fever (CCHF) virus (CCHFV). The immunoglobulin M (IgM)-capture ELISA was developed for the diagnosis of CCHFV infections, using CCHFV rNP as an antigen. These newly developed assays were applied to a study of a CCHF-outbreak and evaluated with sera collected from patients diagnosed as having CCHF by positive reverse transcription-polymerase chain reaction (RT-PCR) and by detection of IgG response. IgM antibodies to CCHFV were detected in 10 of the 13 patients. IgM antibodies to the rNP of CCHFV were detected by the CCHFV rNP-based IgM-capture ELISA in all 6 patients in whom IgG responses were demonstrated, while it was not detected in the 10 patients in whom IgG responses were not demonstrated. Furthermore, the IgM antibodies were detected in 6 of the 61 residents living a CCHF endemic area during the endemic season, while it was not detected in any of the 48 Japanese residents that had never visited the CCHF endemic area. It is concluded that this newly developed CCHFV rNP-based IgM-capture ELISA is a useful method for the diagnosis of CCHFV infections.