Abstract
Four-week-old mice administered with anti-thymocyte serum (ATS) were infected ip. with five strains (less virulent Nakayama-NIH, moderately virulent G-1, Mie 44-1, JaGAr01 and highly virulent JaTH 160) of Japanese encephalitis virus and mortality, virus multiplication and antibody response were studied.
When 0.2 ml of ATS was injected into mice on 0, 3, and 7 day ip., number of leukocyte in circulating blood was markedly reduced during the first 24 hours and gradually recovered to the normal level by 12 days. Mortality of mice treated with ATS one day before, or one day before and three days after ip. infection with JaTH 160 or Nakayama-NIH strain showed no difference from that of infected mice without ATS treatment. However, apparent increase of mortality and shortening of average incubation period were observed in ATS-treated mice, when infected with Mie 44-1, G-1 and JaGArOl strains.
Time of appearance, duration and heights of viremia were apparently the same in mice infected with Mie 44-1 and JaTH 160 strain regardless of ATS-treatment. However, virus multiplication in brain was markedly enhanced by ATS treatment in mice infected with Mie 44-1. On the other hand, no change of viral growth in brain was observed in mice when infected with JaTH 160. Neutralizing antibody response following JE virus infection was found to be slightly retarded in ATS treated mice as compared with non-treated mice infected with either JaTH 160 or Mie 44-1,
The above findings suggest that cell mediated immunity may be involved in the host-defence against JE virus infection in mice, since ATS treatment mainly impairs T cell function in mice.
