[Biological properties of heat-labile lethal toxin of Yersinia pseudotuberculosis].

: The aim of the study was to assess the biological properties of heat-labile lethal protein toxin of Y. pseudotuberculosis. Toxin was extracted from Y. pseudotuberculosis strain 2517 type III serovar pYV-. The toxin killed mice 1-3 days after intraperitoneal administration (LD50=0.3 mcg of the protein). Heating at 56 degrees C during 30 min inactivated lethal activity of the toxin. It had a dose-dependent dermonecrotic effect during intracutaneous administration in rabbits. Hyperimmune rabbit serum to the toxin was obtained. Incubation of the toxin (LD100=1.2 mcg of the protein) with the serum at 37 degrees C during 30 min resulted in neutralization of lethal and dermonecrotic effects. The toxin did not have the cytotoxic effect on HeLa, Hep-2, and SPEV cells, but showed hemolytic activity to human and animal erythrocytes, and weak mitogenic activity to splenic cells of CBA line mice compared with control mitogen (concanavalin A).