Despite the relatively low incidence of plague, its etiological agent, Yersinia pestis, is an exceptional epidemic danger due to the high infectivity and mortality of this infectious disease. Reports on the isolation of drug-resistant Y. pestis strains indicate the advisability of using asymmetric responses, such as phage therapy and vaccine prophylaxis in the fight against this problem. The current relatively effective live plague vaccine is not approved for use in most countries because of its ability to cause heavy local and system reactions and even a generalized infectious process in people with a repressed immune status or metabolic disorders, as well as lethal infection in some species of nonhuman primates. Therefore, developing alternative vaccines is of high priority and importance. However, until now, work on the development of plague vaccines has mainly focused on screening for the potential immunogens. Several investigators have identified the protective potency of bacterial outer membrane vesicles (OMVs) as a promising basis for bacterial vaccine candidates. This review is aimed at presenting these candidates of plague vaccine and the results of their analysis in animal models.

The present review contains information concerning immunobiological properties of plague microbe antigens. All of the identified antigens are evaluated in relation to pathogenicity of Yersinia pestis namely a resistance to phagocytosis, toxicity, adhesiveness etc. as well as persistence ability and adaptation to variable environment. In addition, the role of antigens in immunogenicity of living plague microbe for experimental animals is considered. The data concerning mechanisms of antigenic contribution to the development of adaptive immunity are presented.

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Objective was to assess the effect of specific bacteriophages and gentamycine on the morphological-functional properties of bacteria in the vaccine strain Yersinia pestis EV.Materials and methods. The vaccine strain Y. pestis EV, Pokrovskaya bacteriophage and the pseudotuberculous diagnostic bacteriophage were used for the study. The microbial culture was grown on solid and in liquid growth media at 27 °C for 20–24 h. The co-incubation of bacteria and bacteriophage or gentamycine was carried out at 27 °C for 20 minutes or at 37 °C for 2 hours, respectively. Culture preparations were examined by transmission electron microscopy.Results and discussion. The influence of cultivation conditions and various stress factors on the vesicle production by the vaccine strain Y. pestis EV cells was evaluated. The nature and intensity of morphological-functional changes in Y. pestis EV cells in response to the effect of bacteriophages (plague Pokrovskaya and pseudotuberculous bacteriophages) or an antibiotic (gentamycine) were determined. It was established that co-incubation of Y. pestis EV with Pokrovskaya bacteriophage or gentamycine for 20 min leads to the increase in the production of extracellular vesicles and is accompanied by the development of degenerative changes in bacterial cells.

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