[Characteristics of the response of mice with temporary immunodepression to the administration of live or inactivated vaccine against tick-borne encephalitis].

Mice with immunity defects caused by administration of cyclophosphane were inoculated with an inactivated vaccine or Langat virus (TP-21 strain) considered to be an approximate model of the vaccine against tick-borne encephalitis. In mice with depressed immune response, the asymptomatic infection caused by Langat virus turns into acute form and encephalitis with a fatal outcome develops in 86--100%. Pre-treatment with inactivated tick-borne encephalitis vaccine did not protect the animals with the immunity defect against neuroinfection induced by subsequent inoculation with Langat or tick-borne encephalitis virus. The experimental results suggest that the use of a live vaccine against tick-borne encephalitis in specimens with immunity defects is very dangerous because of the possibility of affection of the central nervous system.