DIAGNOSIS OF TICK-BORNE ENCEPHALITIS - EVALUATION OF SERA WITH BORDERLINE TITERS WITH THE TBE-ELISA

Tick-borne encephalitis (TEE) is a member of the Flaviviridae family, Strong cross-reactions can occur between members of this family, so th at it may be difficult to diagnose specific flavivirus infections, esp ecially when tests with frequent cross-reactions e.g. ELISA tests are used, We tested 238 sera with borderline titers for TEE using the indi rect immunofluorescence or neutralization test for other flaviviruses (yellow fever, dengue, West Nile) to detect cross-reactions due to oth er flavivirus infections or flavivirus vaccination, Only one serum rea cted against all the flaviviruses tested, indicating crossreactivity d ue to infection with any of the flaviviruses. Two other sera exhibited low antibody titers against yellow fever, which could be confirmed by the neutralization test, indicating recent yellow fever vaccination, None of the other sera reacted at all against any of the flaviviruses tested in the tests used, which indicates false positive reactions wit h the TBE-ELISA, Sera with borderline titers in the TBE-ELISA in parti cular should be retested using other test Systems (preferably neutrali zation) and for other flaviviruses (yellow fever, dengue, West Nile) t o detect cross-reactions and to confirm positive results.