Abstract
Serums of three normal humans which had the activity of destroying HeLa cells were accidentally found when we were cultivating the cells using serums purchased from a blood bank in Tokyo. Subsequently three viral strains were isolated from these serums. They were found to be strains of a single virus which has been designated as the HSO virus (Human Serum Orphan). The virus has the following properties:
1) It is filtrable through Seitz EK, Chamberland L3 and Berkefeld N and readily sedimented by centrifugation at 80, 000×g for 60 minutes.
2) It is rapidly inactivated at 56°C in 12 minutes, and gradually at 37°C. It is very stable at -20°C.
3) It is not inactivated by ethyl ether.
4) It well multiplies with cytopathogenic effects in cultures of HeLa cells or cells of skinmuscle tissues of the human embryo, but shows no evidence of multiplication and cytopathogenesis in cultures of monkey kidney cells. Cytopathogenesis is shown in cultures of H946 strain of human bone-marrow cells, Chang's strain of human liver cells or Henle's strain of human intestinal cells, but not in cell cultures of chick embryo tissues.
5) It has no pathogenicity to mice, suckling and adult, guinea pigs, rabbits or developing chick embryos. The Japanese monkey (M. fuscata) seems to have low susceptibility to the virus, showing leucopenia upon infection.
6) It is not neutralized by antiserums against the viruses of influenza (PR8, FM1, Lee), HVJ, Japanese encephalitis, herpes simplex, vaccinia and Rift Valley fever. No cross-neutralization occurs between HSO virus and the viruses of polio Types 1, 2 and 3, ECHO Types 1-7, 9 and 12, Coxsackie A Types 11, 13, 15 and 18, and adeno Types 1-14. The three strains of HSO virus are not distinguishable from each other by neutralization test.
After due discussion of the differentiation from the known viruses it was concluded that HSO virus is a new virus.
Neutralizing antibodies for HSO virus were found in 14.5 per cent (14/92) of adults and in 22.7 per cent (5/22) of children, 8 to 10 years of age, a fact indicating that the virus is disseminated among human beings. However, no data have been yet obtained in relation to clinical manifestations in human beings which might be produced by HSO virus infections.
