[Cross reactions of patients with acute dengue fever to tick-borne encephalitis].

Sera from 20 patients with acute dengue fever were tested on their cross reactivities to other flaviviruses, especially against tick-borne encephalitis (TBE). One of the test systems used, indirect immunofluorescence (IIFT), was shown to exhibit strong cross reactivity. The reactivity pattern of sera from patients with pre-existing vaccine-induced antibodies against TBE or yellow fever was found similar to dengue secondary antibody response. In plaque reduction neutralization tests (PRNT) no cross reactions between different flaviviruses were found. The results show that PRNT is the most specific test system for differentiation of flavivirus antibodies.