Studies on Newcastle Disease Virus (Miyadera Strain)

Summary Newcastle disease virus (Miyadera strain) can be successfully transmitted to suckling mice by the intracerebral route. Although the incubation period of Newcastle disease in mice is longest in the 1st mouse passage generation and becomes shorter with additional passage, the LD50 of virus in mice is highest when egg-adapted Newcastle disease virus is inoculated and lowest in the 1st mouse passage generation, and then it becomes higher again and constant. After passage in mice, infectivity of the virus for the chick becomes weaker; but immunization with this live virus protects chicks from infection with egg-adapted Newcastle disease virus, and their sera are positive in the hemagglutination-inhibition test and indirect complement-fixation test with egg-adapted Newcastle disease virus. The hemagglutinins from mice infected with Newcastle disease virus are demonstrated at pH 6.1, and their activities are inhibited not only by hyperimmune sera against mouse-adapted Newcastle disease virus but also by sera against the egg-adapted virus. For preparation of hyperimmune serum for use in the complement-fixation test, it is best that guinea pigs be immunized intracerebrally with allantoic fluids infected with the Newcastle disease virus. The allantoic membranes of the embryos are best suited as complement-fixing antigen. Newcastle disease virus can be transmitted in brains of guinea pigs through only a few passages. Cats also develop cerebral symptoms when they are inoculated with the virus intracerebrally.