title: Attenuation of Japanese encephalitis virus by brain passage of guinea pigs.
abstract: JE virus was difficult to keep alive in guinea pig brain beyond 3 days and the virus was lost after 3 days. Ten cross passages from guinea pig to mice attenuated JE virus (GP10) and the result indicated that 3 passages could induce illness in guinea pig (GP4). GP4 and GP10 did not induce viremia to mice. 0.1 ml of 1:100,000 and 1:10,000 mouse suspension of GP4 inoculated into the author subcutaneously did not cause any uncomfortable symptom.
mesh_terms: D000818:Animals; D001769:Blood / Q000382:microbiology; D001921:Brain / Q000382:microbiology*; D004664:Encephalitis Virus, Japanese / Q000254:growth & development* / Q000302:isolation & purification; D004672:Encephalitis, Japanese / Q000382:microbiology; D006168:Guinea Pigs; D051379:Mice; D014774:Virulence