Antigens used in the different test systems.

The BNITM IFA is performed on CCHFV-infected Vero-cells at presence of all viral antigens. In the EI IIFT tests, detection of antibodies against CCHFV is performed using recombinant proteins. The two BB ELISAs [18] employ recombinant CCHFV-NP as antigen. The CCHFV-NP was recombinantly expressed in E. coli, purified and directly labelled with horseradish peroxidase. For the BB IgM ELISA, plates are coated with anti-human IgM antibodies. The BB IgG ELISA employs the IgG immune complex binding principle. In this type of ELISA, the recombinantly produced tandem immunoglobulin-like domain of the human FcγR CD32 is used as a capture molecule to bind immune complexes formed between pathogen-specific IgG antibodies and either native or recombinant viral antigens [21]. The wells of the EI ELISAs are coated with a mixture of the recombinant structural proteins of the Crimean-Congo hemorrhagic fever virus. The VB IgM test is a μ-capture ELISA. The VB IgG test is an indirect ELISA using immobilized CCHFV antigen. VectorBest does not provide information about the used antigen. (XLSX)