Complete Genome Assembly of Yersinia pestis subsp. pestis bv. Medievalis SCPM-O-B-6530, a Proline-Dependent Strain Isolated from the Central-Caucasian High-Mountain Plague Focus in Kabardino-Balkar Republic (Russia)

We report the complete genome assembly of Yersinia pestis subsp. pestis bv. Medievalis SCPM-O-B-6530, a strain belonging to the most ancient phylogenetic group (group 2.MED0) of Y. pestis subsp. pestis bv. Medievalis. This proline-dependent strain, carrying an additional plasmid (pCKF), was isolated from the Central-Caucasian high-mountain plague focus in Kabardino-Balkar Republic, Russia.

Enhancement of the Yersinia pestis EV NIIEG Vaccine Srain Immunogenic and Protective Activity under Cultivation with Azoxymer Bromide (Polyoxidonium)

Background. The live-attenuated vaccine based on the Yersinia pestis strain EV line NIIEG is still used in Russia, providing protective efficacy against plague. Nevertheless, there is an urgent need for developing new ways to increase the immunogenicity of the Y. pestis EV NIIEG vaccine strain. In this study, the ability of direct action of immunoadjuvant azoximer bromide (polyoxidonium, PO) on the immunobiological properties of vaccine strain Y. pestis EV NIIEG during cultivation on a dense nutrient medium was evaluated. Materials & Methods. Y.pestis EV NIIEG, cultivated at 28 °С for 48 h on LB agar, Miller pH 7.2 ± 0.1 (Sigma-Aldrich, USA) with the addition of PO and without. MALDI-TOF mass-spectrometry was deployed for the obtainment of mass-spectra of ribosomal proteins from Y. pestis EV NIIEG cells on the MicroflexTM LT mass spectrometer (Bruker Daltonics, Germany). Protective efficacy was evaluated under subcutaneously challenge guinea pigs and mice BALB's with 400 LD50 doses of the Y. pestis 231, Y. pestis P-13268 Vietnam (MLD=5 CFU). Antibody titers to F1 in serum were determined using an ELISA. Results. The addition of the therapeutic concentration of PO in the cultivation medium induced a significant increase in the immunogenicity of Y. pestis EV NIIEG that resulted in enhancement of serum antibody levels against Y. pestis F1 antigen and several times the growth of protective efficacy in the bubonic plague model on two types of experimental animals. ImD50 of the vaccine strain Y. pestis EV NIIEG, cultivated with PO, was significantly (p < 0,05) lower in comparison to ImD50 for Y. pestis EV NIIEG in standard cultivation conditions. One year of storage at a temperature of 4 °С did not alter the protective properties of the vaccine strain Y. pestis EV NIIEG, cultivated with PO. Conclusions. Morphological studies confirmed the absence of influence PO introduction into the cultivation environment on the safety of the vaccine strain. MALDI-TOF MS profile of the Y. pestis EV NIIEG, cultivated with PO, had peaks characteristic features. The mass peak at m/z 3,061 was significantly down-regulated and new mass peaks at m/z 2,759, m/z 3,533 were determined. These changes are accompanied by the increase of Y. pestis EV NIIEG immunogenicity.

Differential word expression analyses highlight plague dynamics during the second pandemic

Research on the second plague pandemic that swept over Europe from the fourteenth to nineteenth centuries mainly relies on the exegesis of contemporary texts and is prone to interpretive bias. By leveraging certain bioinformatic tools routinely used in biology, we developed a quantitative lexicography of 32 texts describing two major plague outbreaks, using contemporary plague-unrelated texts as negative controls. Nested, network and category analyses of a 207-word pan-lexicome, comprising overrepresented terms in plague-related texts, indicated that ‘buboes' and ‘carbuncles' are words that were significantly associated with the plague and signalled an ectoparasite-borne plague. Moreover, plague-related words were associated with the terms ‘merchandise’, ‘movable’, ‘tatters', ‘bed’ and ‘clothes'. Analysing ancient texts using the method reported in this paper can certify plague-related historical records and indicate the particularities of each plague outbreak, which can inform on the potential sources for the causative Yersinia pestis .

Peptidoglycan-Free Bacterial Ghosts Confer Enhanced Protection against Yersinia pestis Infection

To develop a modern plague vaccine, we used hypo-endotoxic Yersinia pestis bacterial ghosts (BGs) with combinations of genes encoding the bacteriophage ɸX174 lysis-mediating protein E and/or holin-endolysin systems from λ or L-413C phages. Expression of the protein E gene resulted in the BGs that retained the shape of the original bacterium. Co-expression of this gene with genes coding for holin-endolysin system of the phage L-413C caused formation of structures resembling collapsed sacs. Such structures, which have lost their rigidity, were also formed as a result of the expression of only the L-413C holin-endolysin genes. A similar holin-endolysin system from phage λ containing mutated holin gene S and intact genes R-Rz coding for the endolysins caused generation of mixtures of BGs that had (i) practically preserved and (ii) completely lost their original rigidity. The addition of protein E to the work of this system shifted the equilibrium in the mixture towards the collapsed sacs. The collapse of the structure of BGs can be explained by endolysis of peptidoglycan sacculi. Immunizations of laboratory animals with the variants of BGs followed by infection with a wild-type Y. pestis strain showed that bacterial envelopes protected only cavies. BGs with maximally hydrolyzed peptidoglycan had a greater protectivity compared to BGs with a preserved peptidoglycan skeleton.

Plague and Plague Vaccines

Plague is a zoonosis caused by the Gram-negative bacillus, Yersinia pestis, a member of the Enterobacteriaceae family. Madagascar, the Democratic Republic of Congo and Peru are still considered highly endemic for plague; however, the bacterium also exists in some regions in Asia and the USA. First symptoms occur 1 to 7 days after exposure. There are three clinical forms of plague: bubonic, pneumonic, and septicemic plague. Transmitted as an aerosol, Y. pestis has been developed as a biological weapon. There are adjuvanted whole-cell vaccines which need repeated dosing, and which are highly reactogenic; subunit vaccines are in development.

Combinatorial Viral Vector-Based and Live Attenuated Vaccines without an Adjuvant to Generate Broader Immune Responses to Effectively Combat Pneumonic Plague

Yersinia pestis , the causative agent of plague, is a Tier-1 select agent and a reemerging human pathogen. A 2017 outbreak in Madagascar with >75% of cases being pneumonic and 8.6% causalities emphasized the importance of the disease.

Plagued by a cryptic clock: Insight and issues from the global phylogeny of Yersinia pestis

Plague has an enigmatic history as a zoonotic pathogen. This potentially devastating infectious disease will unexpectedly appear in human populations and disappear just as suddenly. As a result, a long-standing line of inquiry has been to estimate when and where plague appeared in the past. However, there have been significant disparities between phylogenetic studies of the causative bacterium, Yersinia pestis, regarding the timing and geographic origins of its reemergence. Here, we curate and contextualize an updated phylogeny of Y. pestis using 601 genome sequences sampled globally. We perform a detailed Bayesian evaluation of temporal signal in subsets of these data and demonstrate that a Y. pestis-wide molecular clock model is unstable. To resolve this, we devised a new approach in which each Y. pestis population was assessed independently. This enabled us to recover significant temporal signal in five populations, including the ancient pandemic lineages which we now estimate may have emerged decades, or even centuries, before a pandemic was historically documented from European sources. Despite this, we only obtain robust divergence dates from populations sampled over a period of at least 90 years, indicating that genetic evidence alone is insufficient for accurately reconstructing the timing and spread of short-term plague epidemics. Finally, we identify key historical data sets that can be used in future research, which will complement the strengths and mitigate the weaknesses of genomic data.

IDENTIFICATION OF CORRELATES OF PROTECTION FROM YERSINIA PESTIS ON A MOUSE MODEL AND ASSESSMENT OF THE POSSIBILITY OF USING THEM AS MARKERS OF VACCINATION EFFICIENCY IN HUMANS

In conditions when the assessment of changes in the incidence rate cannot be used as an indicator of the effectiveness of a live plague vaccine, there is a real need to search for other, in particular, immunological correlates of the vaccine's protection. Modern concepts of the patho- and immunogenesis of plague make it possible to narrow the search for possible correlates of protection, focusing on the assessment of cellular factors of the immune response. The aim of this work is to identify the immunological correlates of protection against plague in mice immunized with Yersinia pestis EV NIIEG, and to assess the dynamics of selected markers of immunological effectiveness of vaccination in people vaccinated against plague. Experimental model - BALB / c mice, 40 individuals in each group were immunized with Y. pestis EV at doses of 2 × 102, 1 × 103, 5 × 103, 2.5 × 104 CFU, and on the 21st day they were infected with Y. pestis 231 at a dose of 400 LD50. Control group - intact animals. Immunogenicity was determined by ImD50 and calculated by the Kerber method. Volunteers - 20 people who were first vaccinated with the live plague vaccine and 20 people who were not vaccinated against the plague (comparison group). The production of cytokines in the blood was determined on an enzyme-linked immunosorbent analyzer "LAZURIT" (Dynex Technologies, USA): in mice before infection with Y. pestis 231 on the 14th and 21st days after vaccination; in humans - before vaccination, 1, 6 and 12 months after vaccination. We used commercial kits in accordance with the instructions for their use. The immunized mice showed a significant increase (2.2 times) in the induced IFN-γ production and a moderate increase in the concentration of TNF-α, IL-10 and IL-17A on the 14th day of immunogenesis. A high correlation was found between the survival rate of animals and the level of antigen- / mitogen-induced production of IFN-γ (r = 0.94, p = 0.039), both on the 14th and 21st days, as well as a noticeable relationship with the level of production of IL-10 and IL-17A on the 14th day of immunogenesis. In volunteers one month after inoculation, an increase in the indicators of mitogen-induced production of all detectable cytokines was noted, but the levels of IFN-γ, TNF-α, IL-10, IL-17A significantly increased by the 6th month of observation (p <0.05), although only for IFN-γ and IL-17A, the induced production of these cytokines remained at a sufficiently high level up to a year after inoculation. Thus, IFN-γ and IL-17A can be considered as possible informative correlates of protection of mice from Y. pestis on days 14 and 21, considering the increase in the induced production of these cytokines as adequate markers of the protective efficacy of immunization, and the assessment of the dynamics of these parameters in volunteers vaccinated with the plague live vaccine, an increase in the levels of IFN-γ and IL-17A can be considered a favorable prognostic marker of the immunological efficacy of the vaccine in the period from the 6th to the 12th month of observation.