Experimental Animals Infected with Japanese Encephalitis Virus Report 5. On Correlation between Virus Distribution and Histopathological Findings of The Mouse Brain in Early Stage of Infection.

In 100 gpc-strain female mice, Japanese Encephalitis (JE) virus-JaTH160 strain (10＾6.6 BLU/0.2 ml) -was subcutaneously inoculated. The body weight in each mouse was measured every morning and evening after infection. Over one gram decreasing of the body weight of daily difference was considered as an initial sympton. All these mice were sacrificed at the 8th day regarding as the early stage of the infection. One brain was divided into 3 parts, one of which was kept in -80℃. for virus recovery, the other was kept in -80℃. with treatment of dry-ice acetone hexane for fluorescent antibody technique (FAT), and the third was fixed with 10% formaline for histological examination. The correlationship among the development of symptoms, virus recovery, and histological findings of the brain in each mouse was simultaneously investigated. Each treated emulsion of each mouse brain was intrathalamically inoculated in several suckling mice and the virus content in each mouse brain was confirmed one by one. Furthermore, unclear case except for all or non was re-examined. The other partial brain sectioned with cryostatt was examined by direct method of FAT. The never cell and its process, seemed to almost normal morphologcically, revealed positive fluorescence. On histopathological observation, the initial response to JE infection was found as leukocyte migration with or without karyorrhexis from vessel. It seems that this phenomenon is extremely noteworthy finding. On the other hand, leukocyte infiltration was found in inflammatory focus with progression of the nervous tissue injury again. But, the circulatory disturbance could not be recognized histologically. So, it suggests that there are 2 phases in the leukocyte migration in JE functionally, the former is the sign of infection of brain, and the later is the manifestation of repair of brain injury regard as the inflammatory reaction. Glia cell response, especially Hortega microglia cell, was considered as primary reaction against above leucocyte migration and they show the tendency to from the loose glia nodule. Afterward it takes part in repairing process as secondary response to the nervous tissue injury also. Perivascular cell cuffing was observed as secondary response against some nervous tissue injury, and this appearance may be parallel with antibody formation in early stage of the injury. In this time, the 8th day of infection, the summary of each finding observed in 100 mice is given as follows