A Sensitive Nano Luciferase Immune Complex Assay System for Highly Sensitive and Specific Detection of Antibodies Against Tick-Borne Encephalitis Virus.

Tick-borne encephalitis virus (TBEV) can cause fever, headache, neurological disorders, and/or peripheral flaccid paralysis; therefore, it is a major threat to public health. A rapid, sensitive, and simple method for detecting anti-TBEV antibodies is needed urgently to determine infection and for vaccine evaluation. Here, a luciferase-based immunocomplex assay system (Luc-IC) was developed to detect TBEV antibodies. The system is based on a reporter Nano luciferase (NLuc) that is co-expressed as a fusion protein with viral envelope domain III (ED3) in COS7 cells. The cell supernatant was used directly to detect antigen without the need for a purification step. This simple procedure effectively improved the sensitivity of the assay. Sera from 50 patients with an acute tick-borne encephalitis infection were tested to determine the sensitivity of the NLuc-IC assay. Furthermore, 62 sera from individuals infected with Japanese encephalitis virus, West Nile virus, yellow fever virus, dengue virus, or Zika virus were also tested to determine specificity. The results demonstrated that the assay was 100% sensitive and 100% specific for TBEV antibodies. Thus, this very simple NLuc-IC assay is potentially useful for rapid and accurate diagnosis of TBEV infection in both humans and animals.