Abstract
It is known that the house rat (Rattus norvegicus) is not susceptible for Japanese B encephalitis (JBE) virus. The young rats weighing 60-70g were inoculated intracerebrally with an amount of 0.05cc of 10% brain suspension infected with the virus, strain No. 2869, which had been isolated from an encephalitis horse brain in Chiba 1947 and transferred mice to mice up to the 15th generation. The amount of virus in the rat brain was followed up daily by calculating LD 50 in each brain suspension. The virus was found gradually to decrease in titer by the 6th day while no more virus on the 3rd or the 4th days in the virus suspension preserved in the incubator of 37°C.
The virus was found 3 days longer in the brain of rats, injected with virus suspension mixed with autolyzed nornal rat brain suspension than in the brain injected with the virus suspension without autolyzed brain. However, there was no evidence that the autolyzed brain suspension enhanced the multiplication or promotion of the growth of virus in the brain.
Neither complement fixing antibody nor neutralizing antibodies were found in the sera cellected daily by the 30th day from the rats infected with single attack.
