[Prophylactic use of ceftriaxone in combination with F I antigen immunization in studies on uninbred albino mice infected by Yersinia pestis. Antiplague immunity development].

Administration of highly immunogenic (ED50 12.6 mcg/mouse) F I antigen (100 mcg/mouse) to albino mice 5 hours after their contamination approximately with 1000 LD50 of Yersinia pestis 231 provided 99-percent survival of same animals (17-50%) and 2-5-day prolongation of the life-span, that was indicative of the phenomenon analogous to the survival phenomenon observed in infected animals immunized by immunogenic strains of the plague microbe. The experiment on the mice confirmed high efficacy of ceftriaxone (100-percent survival) when used prophylactically for 5 days 5 hours after the contamination by Y. pestis 231 (approximately 1000 LD50) in the dose equivalent to the daily dose for humans. However, no antiplague immunity developed in the survivors: the immunity index (II) of 1.5x10. The use of ceftriaxone according to the same scheme simultaneously with single immunization by F I antigen in a dose of 100 mcg/mouse resulted not only in 100-percent survival of the animals but also in development of expressing antiplague immunity (II 2.2x10(5)). The protection level corresponded to the control with the same live-stock of the animals after a single immunization in the analogous dose of F I antigen (II 3.2x10(4)) and the ceftriaxone use (II 1.0x10(5)), as well as after immunization of the mice by 10(6) microbial cells of Y. pestis EV NIIEG (II 1.2x10(5)). The results of the study are indicative of the prospective use of subsingle vaccines of the new generation based on F I antigen for combined specific and urgent prophylaxis.