泉熱ウイルスに関する研究 (第1報)

Abstract

“IZUMI Fever” is one of the important exanthematic diseases in this country, which is confined almost to children and may occur either in a sporadic or in an endemic form. It is characterized by a fever of a saddleback type whose onset portends an appearance of a transient fine rash resembling that of scarlatina and followed by some intestinal disorders.Many authors have endeavoured to isolate the virus and to establish their causative nature, but almost all of them failed in volunteer experiments. In this respect we succeeded to produce a typical infection in an 8-year-old female by an oral administration of the isolated virus. After 4 days incubation period, saddleback type fever, bilateral exanthemata of arms, angina and urobilinogen in urine were recognized and the study is now in progress to isolate the same virus from feces and blood of this child again.The virus was isolated from a sporadic case, by intracerbral inoculation of the Berkefeld-N filtrate of feces to young mice. Subsequently the virus was transferred from brain to brain and now fully adapted to mice. These mice usually died until 5 days after inoculation and LD50 for mice weighing 9g. in average is 10-8.5. By intracerebral inoculation to mice the virus distributes in brain, liver, spleen, lung and kidney and intranasal and intraperitoneal administration also cause death of mice. They are stored in 50% glycerol for 4 month without loss of activity.Histopathological changes in mice was limited at the beginning of isolation of the virus rather to liver, spleen and kidney but later chiefly focused in brain, causing encephalitis and leptomeningitis. Egg culture and purification of virus were performed, but not yet succeeded.Complement fixation test was also undertaken. The antigen was prepared by Casal's method from the brain containing this virus and ASK1 (isolated by Kitaoka and others). Immunization of guinea pigs with one of both strains proved the elevation of C. F. antibody against both antigens. Therefore a cross immunity was proved in C. F. T. between these viruses, but not in neutralization test. Neutralization antibody against this virus was proved in the serum of patient from whom the virus was isolated 3, 4 and 6 month after onset, while no antibody was proved in these sera against ASK1. The sera of the experimentally infected patient mentioned above, 2 and 4 month after onset also possessed the antibody.Some disscussions were made about the tropism of this virus.