Characteristics of cellular and humoral immune responses after immunization with different rabies vaccines.

Three rabies vaccines were compared: 1. the Fermi type vaccine, a phenol-treated suspension of brain tissue from infected sheep; 2. a virus grown in sheep brain, purified from the contaminating material to 85-90% and inactivated with beta-propiolactone; 3. and the MNIIP-74 strain cultured in Japanese quail embryo cells and inactivated with beta-propiolactone. A single immunization of mice with any of the preparations resulted in about 50% inhibition of splenocyte migration after 2 days; by day 15 the inhibition was 95-98%. By day 45 the migration index returned to the initial level. Increased ability to blast transformation in splenocytes was found by day 15, reached the maximum (160 to 212% of the control level taken for 100%) by day 30, and then began to decrease. The most marked change in blast transformation was brought about by the purified cerebral vaccine, while the less marked one by the tissue culture vaccine. The titre of virus-neutralizing antibodies reached a maximum after 15-30 days, 60 days after immunization it dropped twice. The resistance of mice to intracerebral infection with the rabies virus shortly after immunization might be due to cellular protective factors, while at later intervals it correlated with the level of virus-neutralizing antibodies.