Studies on the immunity of Newcastle disease virus Part III: The toxin of Newcastle disease virus

There have been made few reports on the virus toxins except those of psitacossis-lymphogranuloma and influenza groups, and, as to the Newcastle disease virus, the existence of its toxin is only presumed by Upton. Considering the fact that this toxin is neutralized by the immune serum of Newcastle disease virus, this toxin seems to have some relationship with the immunity of the virus. Therefore, the author makes reports on the fact that the Newcastle disease virus has its toxin, and about the various results gained by studying its properties. 1) The intraveneous and intraabdominal injection of the chorioallantoic fluid inoculated with this virus, could kill the injected hosts such as chickens and mice. In the case of chickens, it took less than 24 hours to kill, and in the case of mice, the animals died with convulsion. 2) This toxic substance seems to be the virus itself, because the virulence of this toxin and the concentration of virus went parallel to each other and this toxin was not able to be separated from the virus by means of kaolin-adsorption and-dissociation. 3) This virus proliferated for 48 hours in embryonated eggs showed greater virulence than that proliferated for 24 hours. In this test, however, the quantities of virus were adjusted that their infectious titer might be the same one. 4) If this virus is kept at 6°C, it lost its virulence earlier than the infectious titer. Against heating, however, this virulence was a little more stable than the infectious titer, and, in the presence of formalin, these two were lost parallel to each other. 5) The lethal toxin of Newcastle disease virus was neutralized by antiserum and was also neutralized in the bodies of immunized hosts.