Pathogen blockade of TAK1 triggers caspase-8-dependent cleavage of gasdermin D and cell death.

Limited proteolysis of gasdermin D (GSDMD) generates an N-terminal pore-forming fragment that controls pyroptosis in macrophages. GSDMD is processed via inflammasome-activated caspase-1 or -11. It is currently unknown whether macrophage GSDMD can be processed by other mechanisms. Here, we describe an additional pathway controlling GSDMD processing. The inhibition of TAK1 or IκB kinase (IKK) by the Yersinia effector protein YopJ elicits RIPK1- and caspase-8-dependent cleavage of GSDMD, which subsequently results in cell death. GSDMD processing also contributes to the NLRP3 inflammasome-dependent release of interleukin-1ß (IL-1ß). Thus, caspase-8 acts as a regulator of GSDMD-driven cell death. Furthermore, this study establishes the importance of TAK1 and IKK activity in the control of GSDMD cleavage and cytotoxicity.

Dissociation of Tissue Destruction and Bacterial Expansion during Bubonic Plague.

Activation and/or recruitment of the host plasmin, a fibrinolytic enzyme also active on extracellular matrix components, is a common invasive strategy of bacterial pathogens. Yersinia pestis, the bubonic plague agent, expresses the multifunctional surface protease Pla, which activates plasmin and inactivates fibrinolysis inhibitors. Pla is encoded by the pPla plasmid. Following intradermal inoculation, Y. pestis has the capacity to multiply in and cause destruction of the lymph node (LN) draining the entry site. The closely related, pPla-negative, Y. pseudotuberculosis species lacks this capacity. We hypothesized that tissue damage and bacterial multiplication occurring in the LN during bubonic plague were linked and both driven by pPla. Using a set of pPla-positive and pPla-negative Y. pestis and Y. pseudotuberculosis strains in a mouse model of intradermal injection, we found that pPla is not required for bacterial translocation to the LN. We also observed that a pPla-cured Y. pestis caused the same extensive histological lesions as the wild type strain. Furthermore, the Y. pseudotuberculosis histological pattern, characterized by infectious foci limited by inflammatory cell infiltrates with normal tissue density and follicular organization, was unchanged after introduction of pPla. However, the presence of pPla enabled Y. pseudotuberculosis to increase its bacterial load up to that of Y. pestis. Similarly, lack of pPla strongly reduced Y. pestis titers in LNs of infected mice. This pPla-mediated enhancing effect on bacterial load was directly dependent on the proteolytic activity of Pla. Immunohistochemistry of Pla-negative Y. pestis-infected LNs revealed extensive bacterial lysis, unlike the numerous, apparently intact, microorganisms seen in wild type Y. pestis-infected preparations. Therefore, our study demonstrates that tissue destruction and bacterial survival/multiplication are dissociated in the bubo and that the primary action of Pla is to protect bacteria from destruction rather than to alter the tissue environment to favor Y. pestis propagation in the host.

Silencing urease: a key evolutionary step that facilitated the adaptation of Yersinia pestis to the flea-borne transmission route.

The arthropod-borne transmission route of Yersinia pestis, the bacterial agent of plague, is a recent evolutionary adaptation. Yersinia pseudotuberculosis, the closely related food-and water-borne enteric species from which Y. pestis diverged less than 6,400 y ago, exhibits significant oral toxicity to the flea vectors of plague, whereas Y. pestis does not. In this study, we identify the Yersinia urease enzyme as the responsible oral toxin. All Y. pestis strains, including those phylogenetically closest to the Y. pseudotuberculosis progenitor, contain a mutated ureD allele that eliminated urease activity. Restoration of a functional ureD was sufficient to make Y. pestis orally toxic to fleas. Conversely, deletion of the urease operon in Y. pseudotuberculosis rendered it nontoxic. Enzymatic activity was required for toxicity. Because urease-related mortality eliminates 30-40% of infective flea vectors, ureD mutation early in the evolution of Y. pestis was likely subject to strong positive selection because it significantly increased transmission potential.

[Structural analysis of genes participating in melibiose fermentation and isocitrate lyase production in Yersinia pestis strains of main and non main subspecies].

Comparative analysis of nucleotide sequences of genes participating in melibiose fermentation and isocitrate lyase production was conducted in 90 natural Yersinia pestis strains of main and non main subspecies. It was ascertained that the lack of the ability to utilize disaccharide melibiose in strains of the main subspecies is caused by integration of the insertion sequence IS285 at 73 bp from the beginning of the structural gene melB that encodes the transport protein galactoside permease. In contrast, strains of non main subspecies (caucasica, altaica, and ulegeica) contain the intact gene melB and are capable of fermenting melibiose. Differences in the manifestation of the other differential trait, production of isocitrate lyase, are connected with the presence of mutation (insertion of two nucleotides +CC) in the regulatory gene iclR encoding repressor protein of the acetate operon, which is the reason for constitutive synthesis of this enzyme. Strains of non main subspecies do not contain mutations in gene iclR, and this correlates in these strains with their capacity for inducible synthesis of isocitrate lyase.

Physiological and regulatory characterization of KatA and KatY in Yersinia pestis.

The catalase or catalase-peroxidase activity commonly exists in many pathogens and plays an important role in resisting the oxidative burst of phagocytes helping the pathogen persistently colonize in the host. Yersinia pestis is a facultative pathogen and the causative agent of plague. KatY has been identified as a thermosensing antigen with modest catalase activity in this pathogen. Here Y. pestis KatA and KatY were experimentally confirmed as a monofunctional catalase and bifunctional catalase-peroxidase, respectively. Their expression induced by H2O2 was proven to be mediated by the oxidative regulator, OxyR. Expression of KatA changed with growth phases and was crucial to its traditional physiological role in protecting Y. pestis cells against toxicity of exogenous H2O2. KatY was regulated by temperature and H2O2, two major elements of phagolysosomal microenvironments. Consistent with the above results, gene expression of katY increased significantly during intracellular growth of Y. pestis compared with that in vitro growth. However, a DeltakatY mutant was fully virulent to mice, suggesting that KatY is not required for Y. pestis virulence.

[Lectin of Yersinia pestis vaccine strain EV and its immunological properties]. / Lektin vaktsinnogo shtamma Yersinia pestis EV i izuchenie ego immunobiologicheskikh svoistv.

As the result of the chromatographic separation of Y. pestis EV membrane proteins, a protein fraction with hemagglutinating activity was obtained. The isolated preparation was glycoprotein with a molecular weight of 22 kD, contained 16% of carbohydrates and exhibited thermolabile properties. The determination of the carbohydrate specificity of this glycoprotein revealed that it belonged to the class of lectins. Changes in the content of 11 corticosteroids and the population composition of lymphocytes, as well as the detection of specific antibodies in the blood serum of guinea pigs immunized with lectin, were indicative of the fact that the preparation was sufficiently immunogenic and induced the activation of the processes of proliferation and activation of lymphocytes during immunogenesis. The lectin isolated from Y. pestis EV outer membrane may be regarded as an additional factor ensuring the contact of the pathogen with the cells of the body and as a promising component of combined plague vaccine.

Are bacterial proteases important virulence factors?

The contribution of bacterial proteases to virulence has been relatively understudied. It is a simple matter to argue that bacterial proteases have the potential to destroy the structural and functional proteins that constitute host tissues as well as to destroy proteins important in host defense. Systematically demonstrating that such interactions occur during disease pathogenesis is more difficult, although a few studies have suggested that the ability of a pathogen to use proteases to cross proteinaceous barriers within the host contributes to bacterial virulence. This manuscript reviews concepts of bacterial virulence. Next, it describes how the host regulates the activities of its own proteases to maintain a state of health, and examines evidence suggesting that dysregulation of host proteases results in disease. Finally, evidence supporting a role for endogenous microbial proteases or acquisition of host proteases by microbes as virulence determinants is discussed as are suggestions for future directions for research in this area.

[The protective activity of the adhesion pili of Yersinia pestis]. / Izuchenie protektivnoi aktivnosti pilei adgezii Yersinia pestis.

Y. pestis adhesion pili (AP) in the native form and in the subunit form, used for immunization in one or two injections in a dose of 12-100 mu g on aluminum hydroxide, did not protect white mice and guinea pigs from experimental Y. pestis infection. The study revealed that AP produced a pronounced cytotoxic effect on macrophages and practically no influence on leukocytes. This result was confirmed in the study of luminol-dependent chemiluminescence and in the analysis of 5'-nucleotidase activity of phagocytes. These data make it possible to regard AP as Y. pestis antimacrophagal pathogenicity factor.

[Regulatory properties of the rat heart adenylate cyclase in the course of toxic-infective shock caused by Yersinia pestis]. / Reguliatornye svoistva adenilattsiklazy serdtsa krys v dinamike chumnogo toksiko-infektsionnogo shoka.

Influence of intravenously administered to rats murine toxin of Y. pestis in the dose of I mg/ml (LD100) on the regulatory properties of heart plasma membranes adenylate cyclase (AC) has been studied during the intoxication. It has been shown that basal, fluoride,- and 5-guanylyl imidodiphosphate-stimulated AC activity remained unchanged during the intoxication. Stimulation of AC by isoproterenol, glucagon and histamine did not change during the first two hours and significantly decreased after 5 hours of intoxication. Affinity of AC for the investigated hormones did not change through the experiments.

[Cytochemical changes in the peripheral blood leukocytes of guinea pigs inoculated against plague, tularemia and anthrax]. / Tsitokhimicheskie izmeneniia v leikotsitakh perifericheskoi krovi u morskikh svinok, privitykh protiv chumy, tuliaremii i sibirskoi iazvy.

The immunization of guinea pigs with trivaccine and monovaccines against plaque, tularemia and anthrax induces a decrease in the activity of acidic phosphatase in lymphocytes, as well as a decrease in the number of lymphocytes containing this enzyme. A decrease in the activity of alkaline phosphatase and peroxidase had been found to occur in neutrophil leukocytes. Besides, neutrophil leukocytes have shown an increase in the activity of acidic phosphatase and nonspecific esterases. The study based on the evaluation of the activity of the above-mentioned enzymes in lymphocytes and neutrophils has not revealed the predominant influence exercised by any of the antigens, different in their nature and used separately or in the form of a combined preparation, on immunogenesis.