[Endotoxin tolerance of mice to the effect of lipopolysaccharide and lipopolysaccharide-mice toxin complex of virulent strain Yersinia pestis 231].

AIM: Comparative study of the effect of endotoxin tolerance of mice to the effect of lipopolysaccharide (LPS37) and complex of lipopolysaccharide with mice toxin (LPS37-MT) of a virulent Yersinia pestis 231 strain. MATERIALS AND METHODS: Preparations of LPS of highly virulent strain Y. pestis 231 obtained by phenol method from cells cultivated at 37 degrees C as well as commercial preparations of S-LPS and R-LPS of Escherichia coli were used. Mice toxin was isolated from vaccine strain Y. pestis EV76. Effect of endotoxin tolerance was determined in mice treated with aminosugar D-galactosamine. RESULTS: The effect of initial LPS37 and modified form LPS37-MT of Y. pestis 231 was established to significantly differ from each other. When Y. pestis LPS37 is combined with heterologous forms--E. coli LPS or Y. pestis LPS37-MT, the inflammatory response of the organism differs and varies from complete or partial tolerance to complete lack thereof. For LPS37-MT complex only the sequence of administration to bioassay animals of LPS preparations is principal. In the case when primary activation is carried out by LPS37-MT and secondary--by Y. pestis LPS37 or S- and R- forms of E. coli LPS--the tolerance effect is absent. On the contrary, if LPS37-MT is used for recurrent activation against the background of all the other LPS forms including Y. pestis 231 LPS37 the inflammatory response is completely suppressed. CONCLUSION: Tolerance of mice to effect of LPS and LPS-MT complex of virulent Y. pestis 231 strain was shown to be different.

[Toxicity and cytokine-inducing activity of lipopolysaccharide of virulent Yersinia pestis 231 strain].

AIM: Determine correlation between toxicity and cytokine inducing activity of parent and conformation modified forms of lipopolysaccharides (LPS) of virulent Yersinia pestis strain. MATERIALS AND METHODS: LPS was isolated by phenol method from Y. pestis 231 cells grown at 37 degrees C (LPS37). LPS37 was modified by "mice" toxin (MT) Y. pestis. Toxicity was controlled in mice. TNFalpha and IFNgamma cytokine production was determined by enzyme immunoassay. The study was performed in human monocytes U-937 cell line. TLR4 re-stimulation was performed after activation of monocytes by S-LPS and R-LPS of Escherichia coli. RESULTS: LPS37 conformation change of virulent Y. pestis 231 strain during formation of complex with "mice" toxin increases its toxicity for animals by 2 times. LPS37 and LPS37-MT induce TNFalpha and IFNgamma synthesis by human monocytes. LPS37 simultaneously activates MyD88-dependent as well as MyD88-independent signal pathways. Modified LPS37-MT form is a strong activator only of MyD88-dependent pathway and thereafter induces synthesis of predominately one of the cytokines--TNFalpha. Monocyte response to primary and recurrent activation by LPS37 and LPS37-MT corresponds to R- and S-LPS E. coli cytokine response profile. CONCLUSION: A direct correlation between toxicity of LPS37 and LPS37-MT and their TNFalpha-inducing activity was demonstrated in the study. LPS37 and LPS37-MT of Y. pestis 231 differentially activates TLR4 signal pathways of human monocytes.

[Effect of Yersinia pestis EV 76 lypopolysaccharides with different levels of toxicity on dynamics of TNF-alpha and INF-gamma synthesis by human monocytes].

UNLABELLED: AIM. To study dynamics of synthesis of TNF-alpha and INF-gamma by cell line U-937 human monocytes under the effect of Yersinia pestis EV 76 lypopolysaccharides (LPS) with different levels of toxicity: original LPS28 and LPS37 as well as their conformationally--changed variants with enhanced toxicity--complex of LPS with murine toxin (MT) of Y. pestis, and LPS modified by biologicall active compound (BAC) obtained from human erythrocytes. MATERIALS AND METHODS: Using phenol method, LPS were obtained from Y. pestis EV 76 cells grown at 28 and 37 degrees C. Production of cytokines was measured by ELISA. RESULTS: It was shown that original and modified forms of LPS28 and LPS37 induce synthesis of both TNF-alpha and INF-gamma by human monocytes. Expression of genes for two ways of synthesis of these cytokines points to activation and transmission of signal induced by all studied forms of Y. pestis EV 76 LPS through TLR4. Levels of activity of MyD88-dependent and MyD88-independent signaling pathways are different and depend from chemical structure of LPS28 and LPS37, conformation of their modified forms and duration of their exposition with monocytes. Dynamics ofcytokine synthesis corresponds to response of synergized TLR on activation with profound agonistic/antagonistic effect. CONCLUSION: It was determined that conformational modifications of Y. pestis EV76 LPS occurring due to effect of MT and BAC accompanied by quantitative, qualitative and temporal changes of TNF-alpha and INF-gamma synthesis by human monocytes and correlate with increase of their toxic properties.

[Possible mechanisms of implementation of toxic potential of lipopolysaccharides of pathogenic bacteria].

The significance of variability of biological properties of lipopolysaccharides (LPS) is discussed in the paper within the pathogenesis of infectious process. On the basis of an analysis of published data and of results of independent research of two microorganisms (Yersinia pestis and Francisella tularensis) a conclusion is made on that a biologically inert LPS form (with a weak cytokine-inducing ability, apirogenicity and non-toxicity etc.) is typical of highly pathogenic bacteria. It is suggested that the above phenomenon is biologically expedient. Presumably, the inert LPS transforms to the active form inside a sensitive host and, according to an infection stage, each of them being functionally significant. It is the inert status of LPS that enables the pathogens, at the initial stages, to surmount freely the humoral and cell barriers of host. As the infection progressively aggravates and the proliferation of bacteria modifies itself due to LPS micro- and macroorganisms, its chemical structure and biopolymer conformation change. Both modification mechanisms enhance the LPS toxic potential. In case of a sensitive host, such variations transform the biologically inert LPS into a toxically active form with its function of endotoxin being realized. There is no LPS modification in a host insensitive to such infection, which entails either recovery or prolonged persistence of the pathogen inside the microorganism.

[Utilization of hemoglobin by the plague microbe]. / Utilizatsiia gemoglobina chumnym mikrobom.

Hemin and hemoglobin are found to be adequate sources of iron for growth of Yersinia pestis. The mechanism of their assimilation is similar and consists of absorbtion of the free intact hem molecule.

[An increase in the virulence of Yersinia pestis bacteria when the cells are incubated in hemolyzed human erythrocytes]. / Povyshenie virulentnosti bakterii Yersinia pestis pri inkubatsii kletok v gemolizirovannykh éritrotsitakh krovi cheloveka.

The incubation of Y. pestis, the causative agent of plague, in hemolyzed human red blood cells at 37 degrees C for 3 hours enhanced the virulence of vaccine strain EV76 in white mice and guinea pigs and decreased the LD50 of attenuated strains. The phenomenon of increased virulence has been observed only in case of the combined injection of bacteria with the incubation medium. The virulence of Y. pestis cells, introduced alone after such treatment, has proved to remain at the same level.

[The utilization of heme iron by Yersinia pestis in human blood and blood sera]. / Utilizatsiia gemovogo zheleza Yersinia pestis v krovi i syvorotkakh krovi cheloveka.

Y. pestis, the causative agents of plague, have been found to be incapable of using heme iron bound to haptoglobin and hemopexin complexes in human blood and blood serum, and protein components of the serum are not the factors inhibiting this process. At the same time iron of free hemoglobin can be successfully utilized by Y. pestis in the systems used in this study. On the contrary, hemin not only produces any stimulating effect on the growth of Y. pestis in blood serum, but leads to the death of these bacteria [correction of lasteria].

[Attempt at detecting the systems of host specificity in the bacterial causative agents of plague]. / Popytka vyiavleniia sistem khoziaiskoi spetsifichnosti u bakterii vozbuditelia chumy.

An attempt at revealing the system of host specificity in Y. pestis by the methods of transformation and conjugation has been made. No endonuclease restriction has been detected.

[Role of iron in Yersinia pestis multiplication in normal mammalian blood sera]. / Rol' zheleza pri pazmnozhenii Yersinia pestis v normal'nykh syvorotkakh krovi mlekopitaiushchikh.

Y. pestis multiply in normal blood sera of susceptible and nonsusceptible animals at 28 degrees C, while at 37 degrees C bacteriostasis has been registered. Inhibition of the growth of Y. pestis at this temperature is due to the limited supply of iron to bacterial cells.

[The activation of Yersinia pestis "murine" toxin and endotoxin by hemolyzed erythrocytes from mammalian blood]. / Aktivatsiia "myshinogo" toksina i éndotoksina Yersinia pestis gemolizirovannymi éritrotsitami krovi mlekopitaiushchikh.

Y. pestis "mouse" toxin and endotoxin have been found to be capable of being activated with hemolyzed mammalian red blood cells. The LD50 of the activated endotoxin decreases 5-10 times in comparison with the initial preparation. The LD50 of the activated "mouse" toxin decreases 5 times. As revealed in this study, the joint introduction of nonlethal doses of "mouse" toxin and endotoxin is highly toxic for white mice and guinea pigs. The presence of both "mouse" toxin and endotoxin in the toxic mixture is an essential factor for these two species of animals.

[DNA-methyltransferase of the plague microbe]. / DNK-metiltransferazy chumnogo mikroba.

DNA-methyltransferases of Yersinia pestis EV, plague agent bacteria were isolated by P-II phosphocellulose chromatography. The methylating activity is eluated by two fractions at the 0.47 M and 0.53 M NaCl concentrations. Methylases of the plague microbe are specific with respect to two bases (adenine and cytosine) and are capable of modifying both native and denaturated form of DNA.

[Comparison of specific recognition sites of adenine and cytosine DNA-methylase of Yersinia Pestis EV 76 C dam and dcm by Escherichia coli methylases]. / Sravnenie spetsifichnosti saitov uznavaniia adeninovoi i tsitozinovoi DNK-metilaz Yersinia pestis EV 76 C dam i dcm metilazami Escherichia coli.

Using enzymatic modelling of in vitro methylation of chromosome DNAs from Yersinia pestis EV 76, E. coli 834 and E. coli C600 RII by DNA methylases of Eco RII and Eco dam as well as of DNA hydrolysis of plasmid pBR 322 from the cells of Y. pestis EV 76, E. coli C600 and E. coli 834 by restrictases of Eco RII and Cfu I, it was found that cytosine DNA methylase from plague bacteria does not correspond to the type of RII methylases of E. coli. Adenyl DNA methylase is related to E. coli methylases type dam and modifies adenine in the nucleotide sequence of GATC.