Freimane et al.
Development and validation of a novel enzyme-linked immunosorbent assay for the differentiation of tick-borne encephalitis infections caused by different virus subtypes. Infection. 2024; doi:10.1007/s15010-024-02370-2
The standard method for diagnosis of TBE virus infections is enzyme-linked immunosorbent assay (ELISA). By this method, IgM and/or IgG specific antibodies are measured in cerebrospinal fluid or in serum of patients. This test is however unable to distinguish between different TBE virus subtypes. This is because the standard assay is based on glycoprotein E as a capture antigen and is cross-reactive with all subtypes. To overcome this limitation, a novel ELISA has been developed built on non-structural protein 1 (NS1), which has specific epitopes for TBE virus subtypes.
NS1 of three TBE virus subtypes – European, Siberian and Far Eastern – has been recombinantly expressed in HEK human cell lines. These antigens were used to coat polystyrene plates and build an ELISA to detect NS1-specific antibodies.
This ELISA kit was evaluated for sensitivity and specificity with i) sera from patients with an acute infection of TBE virus subtype Eu, ii) with sera from Russian patients with a non-Eu TBE virus infection, iii) with sera from patients with dengue fever, iv) with sera from individuals with yellow fever and TBE vaccination, v) with sera from blood donors with a confirmed TBE virus infection, vi) with sera from blood donors from a non-endemic TBE region and which were negative in a TBE virus neutralization assay.
By the use of this novel assay, it was possible to discriminate between infections by three TBE virus subtypes – the European, the Siberian and the Far Eastern. This assay had a sensitivity of 94% and a specificity of 93% for infections in areas where the Eu subtype circulates. In addition, this assay showed an overall sensitivity of 91% to all three subtypes. This novel assay, based on NS1 (from different subtypes) as antigen, may be suitable for various practical and scientific purposes, such as differentiation of infection by TBE virus subtypes in regions where two or three subtypes co-circulate.