Development of a tick-borne encephalitis serodiagnostic ELISA using recombinant Fc-antigen fusion proteins

Current diagnostic tests for tick-borne encephalitis virus (TBEV) infections require high-biosafety facilities for antigen preparation and can cross-react with other flaviviruses. There is, therefore, a need to develop safe, inexpensive serodiagnostic tools with high specificity and sensitivity. In this study, a recombinant plasmid that expresses the membrane and envelope (E) proteins of TBEV fused to the Fc domain of rabbit IgG was constructed and expressed in mammalian cells. The E-Fc proteins were secreted as soluble homodimers, which retained reactivity with anti-TBEV and anti-rabbit IgG antibodies. The E-Fc proteins were then used to develop an enzyme-linked immunosorbent assay (ELISA) to detect TBEV antibodies in rodent and human sera. Compared with the neutralization test, the ELISA had over 90% sensitivity and specificity. In addition, the assay showed no cross-reactivity with Japanese encephalitis virus antibodies. These findings suggest that the E-Fc ELISA may be a useful tool for TBEV serodiagnosis.