A reporter virus particle seroneutralization assay for tick‐borne encephalitis virus overcomes ELISA limitations

Abstract

Tick‐borne encephalitis (TBE) virus is the most prevalent tick‐transmitted orthoflavivirus in Europe. Due to the nonspecific nature of its symptoms, TBE is primarily diagnosed by ELISA‐based detection of specific antibodies in the patient serum. However, cross‐reactivity between orthoflaviviruses complicates the diagnosis. Specificity issues may be mitigated by serum neutralization assays (SNT), although the handling of clinically relevant orthoflaviviruses requires biosafety level (BSL) 3 conditions and they have highly divergent viral kinetics and cell tropisms. In the present study, we established a reporter virus particle (RVP)‐based SNT in which the infectivity is measured by luminescence and that can be performed under BSL‐2 conditions. The RVP‐based SNT for TBEV exhibited a highly significant correlation with the traditional virus‐based SNT (R2 = 0.8637, p < 0.0001). The RVP‐based assay demonstrated a sensitivity of 92.3% (95% CI: 79.7%–97.4%) and specificity of 100% (95% CI: 81.6%–100%). We also tested the cross‐reactivity of serum samples in RVP‐based assays against other orthoflaviviruses (yellow fever virus, dengue virus type 2, Zika virus, West Nile virus and Japanese encephalitis virus). Interestingly, all serum samples which had tested TBEV‐positive by ELISA but negative by RVP‐based SNT were reactive for antibodies against other orthoflaviviruses. Thus, the RVP‐based seroneutralization assay provides an added value in clinical diagnostics as well as in epidemiological studies.