Vaccine-induced protection against tick-borne encephalitis virus (TBEV) is mediated by antibodies to the viral particle/envelope protein. The detection of non-structural protein 1 (NS1) specific antibodies has been suggested as a marker indicative of natural infections. However, recent work has shown that TBEV vaccines contain traces of NS1, and immunization of mice induced low amounts of NS1-specific antibodies. In this study, we investigated if vaccination induces TBEV NS1-specific antibodies in humans. Healthy army members (n = 898) were asked to fill in a questionnaire relating to flavivirus vaccination or infection, and blood samples were collected. In addition, samples of 71 suspected acute TBE cases were included. All samples were screened for the presence of TBEV NS1-specific IgG antibodies using an in-house developed ELISA. Antibodies were quantified as percent positivity in reference to a positive control. For qualitative evaluation, cut-off for positivity was defined based on the mean OD of the lower 95% of the vaccinated individuals + 3 SD. We found significantly higher NS1-specific IgG antibody titers (i.e., quantitative evaluation) in individuals having received 2, 3, or 4 or more vaccine doses than in non-vaccinated individuals. Similarly, the percentage of individuals with a positive test result (i.e., qualitative evaluation) was higher in individuals vaccinated against tick-borne encephalitis than in unvaccinated study participants. Although NS1-specific IgG titers remained at a relatively low level when compared to TBE patients, a clear distinction was not always possible. Establishing a clear cut-off point in detection systems is critical for NS1-specific antibodies to serve as a marker for distinguishing the immune response after vaccination and infection.

Faculty of Military Health Sciences University of Defence Hradec Kralove Czech Republic

Laboratory of Emerging Viral Infections Veterinary Research Institute Brno Czech Republic; Laboratory of Arbovirology Institute of Parasitology Biology Centre of the Czech Academy of Sciences Ceske Budejovice Czech Republic; Department of Experimental Biology Faculty of Science Masaryk University Brno Czech Republic

Microbiologie ADMED Analyses et Diagnostics Médicaux La Chaux de Fonds Switzerland

Microbiologie ADMED Analyses et Diagnostics Médicaux La Chaux de Fonds Switzerland; Swiss National Reference Center for Tick Transmitted Diseases Switzerland

Citace poskytuje Crossref.org

Tick-borne encephalitis virus seroprevalence and infection incidence in Switzerland, 2020-2021