Infection Patterns of Nude Mice to Japanese Encephalitis Virus : Report 1. Virus Recovery from Organs of Nude Mice Inoculated Subcutaneously

1) Each of 109 BALB/c nu/nu and BALB/c nu/+ mice was inoculated subcutaneously with JaTH 160 strain of Japanese encephalitis virus (JEV) and the course of JEV infection in mice was pursued for 8 weeks. The development of symptoms and the death of infected nu/nu mice were apparently retarded and protracted in comparison with those of nu/+ mice. 2) Virus distribution in organs of nu/nu and nu/+ mice was examined for 8 weeks. Organs where virus was clearly recognized in the early stage of infection in both of nu/nu and nu/+ mice were blood plasma, superficial lymph nodes, bone marrows and spleen. Time of disappearance of virus from organs was in correspondence to that of appearance of neutralizing antibody. In nu/nu mice, virus was decreased under the presence of antibody but still persisted in each organ. In nu/+mice, virus rapidly disappeared in accordance with the increase of neutralizing antibody. The rate of virus detection in bone marrows is lower than that in superficial lymph nodes but virus persisted in the same way as in superficial lymph nodes. 3) In nu/nu mice, virus propagated in brain with rather large variation and in some of them, virus titer was comparatively low. In nu/+ mice, on the other hand, increase of virus in brain was almost straightforward. 4) Neutralizing antibody titer of nu/nu mice was slightly lower than that of nu/+ mice and variation of antibody titer of nu/nu mice was larger than that of nu/+ mice. The above findings suggest that not only humoral immunity but also cell mediated immunity plays important role in the onset of Japanese encephalitis following JEV infection in mice.