[Experimental study on the possibility of using live tularemia vaccine to increase resistance to heterologous infection disease]. / Eksperimental'noe obosnovanie vozmozhnosti primeneniia tuliaremiinoi zhivoi vaktsiny glia povysheniia rezistentnosti k geterologichnym infektsionnym zabolevaniiam.

In experiments on guinea pigs immunized with Francisella tularensis 15, or live tularemia vaccine (LTV), the level of heterologous protective effect to dangerous infectious diseases caused by Yersinia pestis, Burkholderia pseudomallei, B. mallei, Mycobacterium tuberculosis was studied. The study revealed that during the first 4 weeks after the subcutaneous immunization with LTV the level of resistance of the immunized animals to heterologous infective agent reliably increased as indicated by the survival rate of the animals, as well as by the survival time of those killed by infection, in comparison with the controls. Later (on day 150 after immunization) differences in death rate between the groups perceptibly decreased. Nevertheless, the 1 1/2-fold increase of the survival time of the challenged immunized animals in comparison with the controls proved the possibility of using immunization with LTV for the urgent prophylaxis and treatment not only of tularemia, but also of plague, glanders, melioidosis and tuberculosis.

[The efficacy and outlook for the study of live vaccines for the prevention of melioidosis]. / Effektivnost' i perspektivy issledovaniia zhivykh vaktsin dlia profilaktiki melioidoza.

The effect of immunization with Burkholderia pseudomallei, (Pur- and Ts), heterologous vaccines and the recombinant culture of Francisella tularensis RM2, carrying a plasmid with fragments of B. pseudomallei chromosome, was studied on four species of experimental animals, essentially differing by their sensitivity to melioidosis. B. pseudomallei mutants formed the statistically significant level of protection in subcutaneously challenged animals, moderately sensitive to melioidosis, but were not effective when tested, under the same conditions, in animals, highly sensitive to melioidosis. The effect produced by the experimental vaccines under study in animals of all species, subjected to aerogenic challenge, was leveled. The study showed good prospects for the use of tularemia vaccine with a view to create heterologous immunity to melioidosis and the possibility of its use as the basis of bivalent gene engineering vaccine.

[The outlook for the development of live vaccines for the prevention of melioidosis]. / Perspektivy razrabotki zhivykh vaktsin dlia profilaktiki melioidoza.

The effectiveness of immunization with Burkholderia pseudomallei attenuated strains (Pur and Ts), heterologous vaccines and the recombinant culture of Francisella tularensis RM2 carrying a plasmid with fragments of B. pseudomallei chromosome was studied in four species of experimental animals, essentially differing in their sensitivity to melioidosis. The most immunogenic B. pseudomallei mutants, introduced subcutaneously, created a statistically significant level of protection in animals, moderately sensitive to melioidosis, but proved to be ineffective in highly sensitive animal models when tested under the same conditions. In aerogenic infection the effectiveness of the experimental vaccines under study in all species of the animals was on the same level. The study showed good prospects of using tularemia vaccine for inducing heterologous immunity to melioidosis, as well as the possibility of its use as the basis of a bivalent gene-engineering vaccine.

[Characterization of the recombinant strain Francisella tularensis R1A]. / Kharakteristika rekombinatnogo shtamma Francisella tularensis R1A.

For the first time F.tularensis recombinant strain R1A, obtained by the transfer of genes responsible for virulence in F.tularensis strain B 399 A-Cole into recipient cells of the R-form, was studied. Strain R1A was characterized by morphological, tinctorial and biochemical properties, similar to those of F.tularensis virulent strains, and became resistant to the bactericidal action of animal sera, as well as heat resistant (tr42). The results of animal experiments revealed that strain R1A proved to be highly virulent for noninbred white mice, faintly virulent for guinea pigs and avirulent for rabbits. In contrast to the R-form, recombinant strain R1A exhibited high antigenic activity, as well as partially protected guinea pigs from 100 DCL of F.tularensis highly virulent strain B A-Cole. The totality of its properties places recombinant strain R1A in an intermediate position between F.tularensis virulent and vaccine strains.

[The immunological efficacy of Francisella tularensis outer membranes for hamadryas baboons]. / Immunologicheskaia éffektivnost' vneshnikh membran Francisella tularensis dlia obez'ian-gamadril.

The protective properties of the preparation of F. tularensis outer membranes (OM), obtained from F. tularensis vaccine strain 15, were studied in experiments on hamadryas baboons challenged subcutaneously with F. tularensis virulent strain Schu (nonarctic subspecies). The subcutaneous immunization with the OM preparation prevented the development of clinically pronounced infection in more than 70% of the monkeys challenged with F. tularensis strain Schu in a dose of 787 live microbial cells 30 days after immunization. Antibody titers determined in the immunized monkeys with the use of the agglutination test (AT) and the passive hemagglutination test (PHAT) were usual in minimal diagnostic limits (1:80 for AT and 1:320 for PHAT) and did not significantly rise by day 20 after immunization. In all intact animals infected with F. tularensis strain Schu the development of the infectious process was registered, which was accompanied by a rise in temperature exceeding 39.5 degrees C and a rise in the titer of specific antibodies.

[An electron microscopic study of the intercellular contact of a vaccinal strain of Francisella tularensis with gram-negative and gram-positive bacteria]. / Elektronno-mikroskopicheskoe izuchenie mezhkletochnogo kontakta vaktsinnogo shtamma Francisella tularensis s gramotritsatel'nymi i grampolozhitel'nymi bakteriiami.

The use of transmission electron microscopy (the negative contrast and ultrathin section techniques) has made it possible to show that F. tularensis vaccine strain is capable, under normal conditions and in mixtures with other gram-negative and gram-positive bacteria, of forming cell aggregations with close contacts between cells, this contact being probably irreversible. The ultrastructure of bacteria taking part in the formation of intercellular contacts remains intact.