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Advanced molecular-genetic methods for the diagnosis and typing of Yersinia pestis ssp. pestis in the field and clinical material are used for epidemiological surveillance of plague in the Saylyugem natural focus. The aim of the work was to study the spatial genotypic structure of Y. pestis ssp. pestis in the transboundary Saylyugem natural plague focus using MLVA25 typing. Materials and methods. The MLVA25 typing of 160 strains of Y. pestis ssp. Pestis isolated in the Saylyugem natural plague focus in 2012–2021 was carried out. Phylogenetic tree construction was performed with the help of UPGMA and MST methods. Results and discussion. The Y. pestis ssp. pestis strains isolated from the Saylyugem natural plague focus were differentiated into 15 MLVA types by the 25 VNTR loci cluster analysis. The studied strains form a homogeneous complex of MLVA25 types without marked geographical distribution across seven spatial groups. The analysis of the frequency of occurrence of the tandem repeats number for three variable loci of Y. pestis ssp. pestis strains shows the significant differences between the samples from the Mongolian and Russian parts of the Saylyugem natural plague focus. The most pronounced differences in spatial genotypic structure are traced through the yp4280ms62 locus.

Relevance. To date, the specific prevention of plague remains the most effective measure to prevent to prevent the deterioration of the epidemiological situation for this especially dangerous infection in the territory of the Russian Federation. The development of new vaccine preparations created on the basis of avirulent strains of Yersinia pestis with specific genetic defects, can play a crucial importance in the issues of plague immunoprophylaxis.Aim. Determination and comparative analysis of the genomic organization of avirulent strains Y. pestis I-1, Y. pestis I-3536 and vaccine strain Y. pestis EV line NIIEG.Materials and methods. The features of the genetic structure of three Y. pestis strains were studied using plasmid screening and whole genome sequencing.Results and discussion. It was found that the Y. pestis I-1 and Y. pestis I-3536 strains, like Y. pestis EV, lack the chromosomal pgm region. Analysis the genome sequence of Y. pestis I-1 showed that this strain is devoid of the plasmid pMT1, while its individual genes were found in the chromosome structure and the unique 340 kb plasmid. It was revealed that the Y. pestis strain I-3536 lost the plasmid pCD1, however, fragments homologous to this plasmid were found in the structure of its genome.Conclusion. The data obtained allow us to recommend Y. pestis I-1 and Y. pestis I-3536 as the basis for the development of a modern live attenuated plague vaccine.

Objective : investigation of phylogenetic origin and affinity of Yersinia pestis strains isolated from field material collected during the epizootiologic survey of the Mongolian part of trans-boundary Sailyugem natural plague focus. Materials and methods : MLVA25-typing of 81 Y. pestis strains, including 55 isolates from the Mongolian part of transboundary Sailyugem natural plague focus, collected in 2017-2018 was carried out. The plague agent strains isolated in different years in the natural foci of Northwest Mongolia and Southern Siberia were used as comparison group. Whole genome sequencing was performed for 21 Y. pestis strains subspecies pestis isolated in Mongolia in 2018 and 1988-1990 and in Gorny Altai of the Russian Federation in 2012-2016. SNP-typing was conducted on the basis of whole genomes of Y. pestis strains identified in the current research and also genomes from GenBank international database. Search of single nucleotide polymorphisms in Y. pestis genomes was carried out in two ways: by means of snippy v. 4.3.5 software and using mummer v. 3.1 package and a set of the author’s scripts. Phylogenetic reconstruction was conducted with the help of RAxML method. Results and discussion: Results of MLVA25 typing of Y. pestis subsp. pestis demonstrated that the strains isolated in Mongolian and Russian parts of the Sailyugem and Khuukh-Serkh-Munkh-Khairkhan natural foci belong to one common cluster. SNP-typing placed the studied isolates from the Mongolian and Russian territories into 4. ANT phylogenetic line with high level of reliability which testifies to the genetic similarity of the specified pathogen groups. The data of MLVA- and SNP-typing showed insignificant variability of the plague agent in the territory of the Mongolian part of trans-boundary Sailyugem natural plague focus. On the basis of the conducted research and results of epizootiological monitoring of Russia and Mongolia border territories it is possible to draw a conclusion on gradual wide penetration of Y. pestis subsp. pestis mainly into grey marmot settlements in Southeast Altai from Northwest Mongolia.

The evaluation of sensitization conducted on guinea pig leukocytes immunized with the cell wall preparations of F. tularensis. In this research was shown that the cell wall preparations F tularensis subsp mediaasiatica A-61 and F tularensis subsp tularensis В-399 A-Cole do not caused allergization in contrast with cell wall prepararions of F. tularensis 15 (extracted by Research Institute of Epidemiology and Hygiene) and F. tularensis subsp. holarctica 306.

Relevance. In the Russian Federation is noted the negative dynamics of epizootic process of brucellosis among epidemiologically important species of farm animals (cattle and small ruminants), which represents a threat to the population. Used in Russia live vaccine based on a strain of Brucella abortus 19 the BA has reduced virulence, but capable at high doses (108 -2 109 m.c.) cause a generalized infection in guinea pigs and humans, and in violation of the rules cause post-vaccination complications. Goal. Assess possibility of the thermo-extract derived from the S- and L-forms of Brucella, get an immune response in guinea pigs, and reduce the risk of infection with virulent brucella. Materials and methods. Two series of experiments were carried out on guinea pigs. Immunized guinea pigs thermo-extracts (TE) from a strain of B. abortus I-206 in the S- and L-forms, and live brucellosis vaccine (Scientific and Production Association for Immunological Preparations «Microgen», Russia). To infect guinea pigs using virulent B. abortus 544 (Reference) and B. melitensis I-203 from the museum of living cultures of the Irkutsk Scientific Research Anti-Plague Institute. Results. In the first and second experiment after immunization L TE in dose 5 mg and 10 mg after infection with B. abortus and B. melitensis 5441-203 were approximately similar results. Immunization of Brucella in TE S-form or complex of L + S TE either of two doses (5 mg or 10 mg) cultures after infection B. abortus and B. melitensis 5441-203 gave the same result as a vaccine B. abortus 19VA. Conclusions. The results indicate the prospects of further study of experimental steps for using immunizing agents TE S, L TE and TE S + L on the laboratory animals.

Relevance. The vast majority of the virulence factors of Yersinia pestis is determined by genes of plasmid. The genome of the plague pathogen Altai subspecies Y. pestis subsp. altaica has three plasmids: pYV, pYP and pYT. Plasmids pYV Yersinia strains exhibit phenotypic traits, the effect of which is aimed at the suppression of the phagocytic activity of the cells of the immune system. Species-specific plasmid pYP determines synthesis bacteriocine (pesticin 1) and plasminogen activator, and plasmid pYT - murine toxin and a capsular antigen F1. Loss of one or more plasmids leads to a change of the pathogenic properties and a reduction or even total loss of the virulence of the pathogen, as well as affect the functional state organs of the immune system. Goal. To reveal characteristics of subpopulations of blood cells of experimental animals infected with Y. pestis containing various plasmids Materials and methods. The study was conducted on 370 white improved conventional mice with standard of content and weight (17 -19 g). As objects of study used 7 strains of Y. pestis from the collection of the museum of living cultures of the Irkutsk Scientific Research Anti-Plague Institute: Y. pestis subsp. altaica I-2948/3, Y. pestis subsp. altaica I-2948, Y. pestis subsp. altaica I-2359, Y. pestis subsp. I-3560 pestis, Y. pestis subsp. I-3480 pestis, Y. pestis subsp. I-2638 pestis, Y. pestis subsp. pestis I-3479. Results. Immunograms analysis showed that changes in the composition of blood cells in experimental animals depends on plasmids of the strain and time of observation. Importantly, the infectious process induced strains with a complete set of plasmids (Y. pestis subsp. pestis I-3560, Y. pestis subsp. pestis I-2638), is accompanied by significant changes in cell populations, as the causative agent of plague blocking barrier system key mechanisms innate immunity and prevents the formation of high-grade microorganism adaptive immunity. Conclusions. Are established features of subpopulation structure of blood cells of white mice, infected with strains of the main and Altai subspecies and their isogene options which are associated with a plasmid profile of a plague microbe. Strains of Y. pestis subsp. pestis of I-3479 and Y. pestis subsp. pestis of I-3480 can be recommended for further studying as perspective as vaccinal.

Objective of the study was a complex pheno- and genotypic investigation of Yersinia pestis I-3595 and Y. pestis I-3596 strains, isolated from marmots that were the source of human infection in 2015. Materials and methods. A comprehensive microbiological, molecular-genetic and mass-spectrometric studying of Y. pestis ssp. pestis strains, isolated from two grey marmots that became a cause of the plague case in Gorno-Altai high-mountain focus in 2015, was performed using up-to-date methods. Results and conclusions. It was established that the studied Y. pestis strains belonged to the main subspecies. Results of plasmid screening, multilocus VNTR-and mass-spectrometric analyses showed that those strains were closely related to Y. pestis variant detected in the focus in 2012 and in 2014, and circulating in Northwest Mongolia and Tuva natural focus.

The paper presents data on changes in the respiratory part of lungs of white mice with experimental plague caused by Yersinia рestis strains with different plasmid composition of Tuva and Gorno-Altaisk natural foci of plague and breeding clones. Morphological and structural changes in the lungs, which appear different degree of activation of the immune response and the severity of the pathological process caused by Y. pestis subsp. altaica and Y. pestis subsp. pestis and their isogenic plasmid options.

We have estimated the effects of the Brucella abortus 19 ВА inactivated vaccine, thermo extracts of Brucella abortus I-206 in the L- and S-forms and corpuscular antigen of Brucella abortus I-206 in L-form on the population and subpopulation structure of blood cells and peritoneal fluid of white mice. It was showed that the antigen preparations of Brucella abortus I-206 in L-form didn't caused endogenous intoxication of the organism of experimental animals in distinction from the inactivated vaccine of Brucella abortus 19 BA.

Laboratory diagnostics of plague was carried out in compliance with valid operational guidelines and regulations. But its peculiarity consisted in the performance of diagnostic investigations secondary to antimicrobial therapy with application of preparations characterized by the expressed activity towards gram-negative microorganisms, including the agent of plague (ceftriaxone, ciprolet, and amikacin). The studies revealed that under antibiotic treatment during the early phase of infection the most effective method for the laboratory plague diagnostics was PCR. Based on the results of the assay it was possible to establish not only provisional, but also the final diagnosis in a patient. Obtained was genetic characteristics of the strains isolated from the patient and the marmot, withdrawn at the patient’s place, using techniques of molecular-genetic analysis, in particular PCR, multilocus VNTR, and multilocus and genome-wide sequencing. Thereupon the strains were attributed to antique biovar of the main subspecies of plague agent. In addition, close relation to Y. pestis of the main subspecies isolated in the same focus in 2012 and to the strains from Mongolian Altai and Tuvinian mountain focus was determined based on phylogenetic analysis of the isolates.

Performed is a complex microbiological, molecular-genetic and mass-spectrometric identification of Yersinia pestis main ssp. strain, which was isolated for the first time in the history of surveillance over the Altai mountain natural plague focus in June, 2012. Determined is its high universal virulence. Plasmid screening, multi-locus VNTR- and mass-spectrometric analyses have revealed the strain to be more closely related to the plague agent variant, circulating in the territory of the natural focus Khuukh-Serkh-Munkh-Khairkhan, Bayan-Ul’giisk aimak, Mongolia.

Arabinoganactane isolated from Siberian larch (Larix sibirica) and its iron and cobalt nanobiocomposites were selected as immunomodulators to elucidate the possibility of intensification of specific immunity against plague. Comparative morphometric analysis of immune system organs of white mice inoculated with live plague vaccine (LPV) and its combination with immunomodulators was performed. Experimental data indicate that arabinogalactane and its nanobiocomposites used in combination with LPV increase immunocytopoetic function of immune system organs to larger extent than LPV.

Effects of Y. pestis EV antigenic complexes upon the functional activity of the phagocytic cells of guinea pig and white mice were assayed to demonstrate that the preparation constructed on the basis of the F1 antigen, Y. pestis EV membrane fraction and the Siberian larch arabinogalactane (AG) used as an immunomodulator, was able to increase the functional activities of the phagocytic system in test animals (guinea pigs), enhancing the adhesive and absorptive activity of the peritoneal macrophages and the intensity of active oxygen and nitrate monoxide production, as well as stimulating the activity of myeloperoxidase and the synthesis of non-enzyme cationic polymorphonuclear leucocytes. The antigenic complex prepared on the basis of the F1 antigen, Y. pestis EV membrane fraction and AG, was also shown to exert a stimulating effect on cytokine-inducing function of white-mouse macrophages expressed in the increased production of IL-1, IL-6 and FNO-α cytokines.