Evaluation of Serological Diagnostic Test Systems Assessing the Immune Response to Japanese Encephalitis Vaccination.

A new commercial anti-Japanese encephalitis virus IgM and IgG indirect immunofluorescence test (IIFT) was evaluated for the detection of the humoral immune response after Japanese encephalitis vaccination. The IgM IIFT was compared to two IgM capture ELISAs and the IgG IIFT was analysed in comparison to a plaque reduction neutralization test (PRNT50) and an IgG ELISA. Moreover, the course of the immune reaction after vaccination with an inactivated JEV vaccine was examined. For the present study 300 serum samples from different blood withdrawals from 100 persons vaccinated against Japanese encephalitis were used. For the IgM evaluation, altogether 78 PRNT50 positive samples taken 7 to 56 days after vaccination and 78 PRNT50 negative sera were analyzed with the Euroimmun anti-JEV IgM IIFT, the Panbio Japanese Encephalitis – Dengue IgM Combo ELISA and the InBios JE Detect IgM capture ELISA. For the IgG evaluation, 100 sera taken 56 days after vaccination and 100 corresponding sera taken before vaccination were tested in the PRNT50, the Euroimmun anti-JEV IgG IIFT, and the InBios JE Detect IgG ELISA. The Euroimmun IgM IIFT showed in comparison to the Panbio ELISA a specificity of 95% and a sensitivity of 86%. With respect to the InBios ELISA, the values were 100% and 83.9%, respectively. The analysis of the Euroimmun IgG IIFT performance and the PRNT50 results demonstrated a specificity of 100% and a sensitivity of 93.8%, whereas it was not possible to detect more than 6.6% of the PRNT50 positive sera as positive with the InBios JE Detect IgG ELISA. Thus, the IIFT is a valuable alternative to the established methods in detecting anti-JEV antibodies after vaccination in travellers and it might prove useful for the diagnosis of acutely infected persons. Author Summary: Japanese encephalitis, caused by the Japanese encephalitis virus, is the most prominent viral encephalitis in Asia. Three billion people live in endemic areas and at least 50,000 clinical cases occur each year, although reliable vaccines are available. Concerning the burden caused by this disease, more should be done to prevent it. Good and reliable diagnostics are one of the prerequisites for an effective fight against the virus, but it is nearly impossible to produce and evaluate an in-house assay according to high standard quality criteria as done for commercial tests. Only a few commercial assays are available and the thorough evaluation of these assays is of great importance for diagnostic laboratories. The sensitivity and specificity are statistical measures to assess the performance of a diagnostic assay. In this study the Euroimmun IgM indirect immunofluorescence test (IIFT) was compared to the Panbio and InBios IgM ELISAs. It showed a specificity of 95% and 100%, and a sensitivity of 86% and 93.8%, respectively. The specificity of the IgG IIFT in comparison to PRNT50 was 100% and the sensitivity was 93.8%. Overall, the IIFT showed a comparable performance and could be used as an alternative to the established assays. [ABSTRACT FROM AUTHOR]