Immune sera for use in hemagglutination-inhibition reactions for the typing of arboviruses are generally prepared by experimentally immunizing mammals such as mice, guinea-pigs or rabbits. Such sera, however, are often lacking in potency and type-specificity, particularly those in group B. The authors have therefore attempted to obtain reference sera by immunizing chicks with antigenic suspensions of virulent mouse-brain. After some experimentation with techniques, they found the best results were obtained by two intramuscular inoculations at seven days interval, the first being administered to week-old chicks. With Sindbis virus group A this schedule yielded high-titer, type-specific sera such as are obtained with guinea-pigs only by hyperimmunization. In group B, potent and high type-specific sera were obtained with Central European tick-borne encephalitis virus, St Louis encephalitis virus and West Nile virus, which are all known usually to cause difficulty by cross-reacting. With Murray Valley encephalitis virus, only four of 21 sera reacted sufficiently specifically, and then at low titer. Attempts with dengue-1 were unsuccessful. Author
Trans. of World Health Organization. Bulletin (Switzerland) v32 p665-673 1965.