Remodeling Yersinia pseudotuberculosis to generate a highly immunogenic outer membrane vesicle vaccine against pneumonic plague

SignificanceYersinia pestis, the etiologic agent of plague, has been responsible for high mortality in several epidemics throughout human history. This plague bacillus has been used as a biological weapon during human history and is currently one of the deadliest biological threats. Currently, no licensed plague vaccines are available in the Western world. Since an array of immunogens are enclosed in outer membrane vesicles (OMVs), immune responses elicited by OMVs against a diverse range of antigens may reduce the likelihood of antigen circumvention. Therefore, self-adjuvanting OMVs from a remodeled Yersinia pseudotuberculosis strain as a type of plague vaccine could diversify prophylactic choices and solve current vaccine limitations.

γδ T cell IFNγ production is directly subverted by Yersinia pseudotuberculosis outer protein YopJ in mice and humans

Yersinia pseudotuberculosis is a foodborne pathogen that subverts immune function by translocation of Yersinia outer protein (Yop) effectors into host cells. As adaptive γδ T cells protect the intestinal mucosa from pathogen invasion, we assessed whether Y. pseudotuberculosis subverts these cells in mice and humans. Tracking Yop translocation revealed that the preferential delivery of Yop effectors directly into murine Vγ4 and human Vδ2⁺ T cells inhibited anti-microbial IFNγ production. Subversion was mediated by the adhesin YadA, injectisome component YopB, and translocated YopJ effector. A broad anti-pathogen gene signature and STAT4 phosphorylation levels were inhibited by translocated YopJ. Thus, Y. pseudotuberculosis attachment and translocation of YopJ directly into adaptive γδ T cells is a major mechanism of immune subversion in mice and humans. This study uncovered a conserved Y. pseudotuberculosis pathway that subverts adaptive γδ T cell function to promote pathogenicity.

Unconventional γδ T cells are a dynamic immune population important for mucosal protection of the intestine against invading pathogens. We determined that the foodborne pathogen Y. pseudotuberculosis preferentially targets an adaptive subset of these cells to subvert immune function. We found that direct injection of Yersinia outer proteins (Yop) into adaptive γδ T cells inhibited their anti-pathogen functions. We screened all Yop effectors and identified YopJ as the sole effector to inhibit adaptive γδ T cell production of IFNγ. We determined that adaptive γδ T cell subversion occurred by limiting activation of the transcription factor STAT4. When we infected mice with Y. pseudotuberculosis expressing an inactive YopJ, this enhanced the adaptive γδ T cell response and led to greater cytokine production from this subset of cells to aid mouse recovery. This mechanism of immune evasion appears conserved in humans as direct injection of Y. pseudotuberculosis YopJ into human γδ T cells inhibited cytokine production. This suggested to us that Y. pseudotuberculosis actively inhibits the adaptive γδ T cell response through YopJ as a mechanism to evade immune surveillance at the site of pathogen invasion.

Defective phagocyte association during infection of Galleria mellonella with Yersinia pseudotuberculosis is detrimental to both insect host and microbe

Adhesins facilitate bacterial colonization and invasion of host tissues and are considered virulence factors, but their impact on immune-mediated damage as a driver of pathogenesis remains unclear. Yersinia pseudotuberculosis encodes for a multivalent adhesion molecule (MAM), a mammalian cell entry (MCE) family protein and adhesin. MAMs are widespread in Gram-negative bacteria and enable enteric bacteria to colonize epithelial tissues. Their role in bacterial interactions with the host innate immune system and contribution to pathogenicity remains unclear. Here, we investigated howY. pseudotuberculosis MAM contributes to pathogenesis during infection of the Galleria mellonella insect model. We show that Y. pseudotuberculosis MAM is required for efficient bacterial binding and uptake by hemocytes, the host phagocytes. Y. pseudotuberculosis interactions with insect and mammalian phagocytes are determined by bacterial and host factors. Loss of MAM, and deficient microbe-phagocyte interaction, increased pathogenesis in G. mellonella. Diminished phagocyte association also led to increased bacterial clearance. Furthermore, Y. pseudotuberculosis that failed to engage phagocytes hyperactivated humoral immune responses, most notably melanin production. Despite clearing the pathogen, excessive melanization also increased phagocyte death and host mortality. Our findings provide a basis for further studies investigating how microbe- and host-factors integrate to drive pathogenesis in a tractable experimental system.

Yersinia pseudotuberculosis YopJ Limits Macrophage Response by Downregulating COX-2-Mediated Biosynthesis of PGE2 in a MAPK/ERK-Dependent Manner

Prostaglandin E2 (PGE2) is an essential immunomodulatory lipid released by cells in response to infection with many bacteria, yet its function in macrophage-mediated bacterial clearance is poorly understood. Yersinia overall inhibits the inflammatory circuit, but its effect on PGE2 production is unknown. We hypothesized that one of the Yersinia effector proteins is responsible for the inhibition of PGE2 biosynthesis. We identified that yopB-deficient Y. enterocolitica and Y. pseudotuberculosis deficient in the secretion of virulence proteins via a type 3 secretion system (T3SS) failed to inhibit PGE2 biosynthesis in macrophages. Consistently, COX-2-mediated PGE2 biosynthesis is upregulated in cells treated with heat-killed or T3SS-deficient Y. pseudotuberculosis but diminished in the presence of a MAPK/ERK inhibitor. Mutants expressing catalytically inactive YopJ induce similar levels of PGE2 as heat-killed or ΔyopB Y. pseudotuberculosis, reversed by YopJ complementation. Shotgun proteomics discovered host pathways regulated in a YopJ-mediated manner, including pathways regulating PGE2 synthesis and oxidative phosphorylation. Consequently, this study identified that YopJ-mediated inhibition of MAPK signal transduction serves as a mechanism targeting PGE2, an alternative means of inflammasome inhibition by Yersinia. Finally, we showed that EP4 signaling supports macrophage function in clearing intracellular bacteria. In summary, our unique contribution was to determine a bacterial virulence factor that targets COX-2 transcription, thereby enhancing the intracellular survival of yersiniae. Future studies should investigate whether PGE2 or its stable synthetic derivatives could serve as a potential therapeutic molecule to improve the outcomes of specific bacterial infections. Since other pathogens encode YopJ homologs, this mechanism is expected to be present in other infections. IMPORTANCE PGE2 is a critical immunomodulatory lipid, but its role in bacterial infection and pathogen clearance is poorly understood. We previously demonstrated that PGE2 leads to macrophage polarization toward the M1 phenotype and stimulates inflammasome activation in infected macrophages. Finally, we also discovered that PGE2 improved the clearance of Y. enterocolitica. The fact that Y. enterocolitica hampers PGE2 secretion in a type 3 secretion system (T3SS)-dependent manner and because PGE2 appears to assist macrophage in the clearance of this bacterium indicates that targeting of the eicosanoid pathway by Yersinia might be an adaption used to counteract host defenses. Our study identified a mechanism used by Yersinia that obstructs PGE2 biosynthesis in human macrophages. We showed that Y. pseudotuberculosis interferes with PGE2 biosynthesis by using one of its T3SS effectors, YopJ. Specifically, YopJ targets the host COX-2 enzyme responsible for PGE2 biosynthesis, which happens in a MAPK/ER-dependent manner. Moreover, in a shotgun proteomics study, we also discovered other pathways that catalytically active YopJ targets in the infected macrophages. YopJ was revealed to play a role in limiting host LPS responses, including repression of EGR1 and JUN proteins, which control transcriptional activation of proinflammatory cytokine production such as interleukin-1β. Since YopJ has homologs in other bacterial species, there are likely other pathogens that target and inhibit PGE2 biosynthesis. In summary, our study's unique contribution was to determine a bacterial virulence factor that targets COX-2 transcription. Future studies should investigate whether PGE2 or its stable synthetic derivatives could serve as a potential therapeutic target.

Oral vaccination with live attenuated Yersinia pseudotuberculosis strains delivering a FliC180-LcrV fusion antigen confers protection against pulmonary Y. Pestis infection

We incorporated the ΔPfur::TT araC PBADfur deletion-insertion mutation on top of a previous Yersinia pseudotuberculosis mutant (Δasd ΔyopJ ΔyopK) to construct a new mutant designated as Yptb5, which manifests the arabinose-dependent regulated delayed fur (encoding ferric uptake regulator) shut-off. The Yptb5 strain was used to deliver an adjuvanted fusion protein, FliC180-LcrV. Levels of FliC180-LcrV synthesis were same in Yptb5 either harboring pSMV4, a p15A ori plasmid or pSMV8, a pSC101 ori plasmid containing the fliC180-lcrV fusion gene driven by Ptrc promoter. Tissue burdens of both Yptb5(pSMV4) and Yptb5(pSMV8) in mice had similar patterns. Mice vaccinated orally with 5 × 108 CFU of either Yptb5(pSMV4) or Yptb5(pSMV8) strain were primed high antibody titers with a balanced Th1/Th2 response, also developed potent T-cell responses with significant productions of IFN-γ, IL-17A and TNF-α. Immunization with each mutant strain conferred complete protection against pulmonary challenge with 5.5 × 103 CFU (55 LD50) of Y. pestis, but partial protection (50% survival) against 100 LD50 of Y. pestis. Our results demonstrate that arabinose-dependent regulated delayed fur shut-off is an effective strategy to develop live attenuated bacterial vaccines while retaining strong immunogenicity.

Subcutaneous vaccination with a live attenuated Yersinia pseudotuberculosis plague vaccine

A single oral inoculation to mice of the live attenuated Yersinia pseudotuberculosis VTnF1 strain producing an F1 pseudocapsule protects against bubonic and pneumonic plague. However oral vaccination can fail in humans exposed to frequent intestinal infections. We evaluated in mice the efficacy of subcutaneous vaccine injection as an alternative way to induce protective immunity, while reducing the dose and avoiding strain release in nature. A single subcutaneous dose of up to 10⁸ CFU induced dose-dependent antibody production. At the dose of 10⁷ CFU, i.e. 10 times less than via the oral route, it caused a modest skin reaction and protected 100% against bubonic and 80% against pneumonic plague, caused by high doses of Yersinia pestis. Bacteria migrating to lymph nodes and spleen, but not feces, were rapidly eliminated. Thus, subcutaneous injection of VTnF1 would represent a good alternative when dissemination in nature and human intestinal responsiveness are limitations.

A Recombinant Attenuated Yersinia pseudotuberculosis Vaccine Delivering a Y. pestis YopENt138-LcrV Fusion Elicits Broad Protection against Plague and Yersiniosis in Mice

In this study, a novel recombinant attenuated Yersinia pseudotuberculosis PB1+ strain (χ10069) engineered with ΔyopK ΔyopJ Δasd triple mutations was used to deliver a Y. pestis fusion protein, YopE amino acid 1 to 138-LcrV (YopENt138-LcrV), to Swiss Webster mice as a protective antigen against infections by yersiniae. χ10069 bacteria harboring the pYA5199 plasmid constitutively synthesized the YopENt138-LcrV fusion protein and secreted it via the type 3 secretion system (T3SS) at 37°C under calcium-deprived conditions. The attenuated strain χ10069(pYA5199) was manifested by the establishment of controlled infection in different tissues without developing conspicuous signs of disease in histopathological analysis of microtome sections. A single-dose oral immunization of χ10069(pYA5199) induced strong serum antibody titers (log10 mean value, 4.2), secretory IgA in bronchoalveolar lavage (BAL) fluid from immunized mice, and Yersinia-specific CD4+ and CD8+ T cells producing high levels of tumor necrosis factor alpha (TNF-α), gamma interferon (IFN-γ), and interleukin 2 (IL-2), as well as IL-17, in both lungs and spleens of immunized mice, conferring comprehensive Th1- and Th2-mediated immune responses and protection against bubonic and pneumonic plague challenges, with 80% and 90% survival, respectively. Mice immunized with χ10069(pYA5199) also exhibited complete protection against lethal oral infections by Yersinia enterocolitica WA and Y. pseudotuberculosis PB1+. These findings indicated that χ10069(pYA5199) as an oral vaccine induces protective immunity to prevent bubonic and pneumonic plague, as well as yersiniosis, in mice and would be a promising oral vaccine candidate for protection against plague and yersiniosis for human and veterinary applications.

Lectin pathway factors in patients suffering from juvenile idiopathic arthritis

Both complement activation and certain infections (including those with Yersinia sp.) may contribute to the pathogenesis of juvenile idiopathic arthritis (JIA). We investigated factors specific for the lectin pathway of complement: mannose-binding lectin (MBL), ficolins and MBL-associated serine protease-2 (MASP-2), in 144 patients and 98 controls. One hundred and six patients had oligoarticular disease and 38 had polyarticular disease. In 51 patients (out of 133 tested), Yersinia-reactive antibodies were found (JIA Ye+ group). MBL deficiency was significantly more frequent in the JIA Ye+ group than in patients without Yersinia-reactive antibodies or in controls. Median serum ficolin-2 level was significantly lower (and proportion of values deemed ficolin-2 insufficient greater) in JIA patients irrespective of their Yersinia antibody status. The minority (C) allele at -64 of the FCN2 gene was less frequent among JIA patients than among control subjects. No differences were found in the frequency of FCN3 gene +1637delC or MASP2 +359 A>G mutations nor for median values of serum ficolin-1, ficolin-3 or MASP-2. However, high levels of serum ficolin-3 were under-represented in patients, in contrast to MBL. MBL, ficolin-1, ficolin-2, ficolin-3 and MASP-2 were also readily detectable in synovial fluid samples but at a considerably lower level than in serum. Our findings suggest a possible role for the lectin pathway in the pathogenesis of JIA, perhaps secondary to a role in host defence, and indicate that investigations on the specificity of lectin pathway recognition molecules towards specific infectious agents in JIA might be fruitful.

YopE specific CD8+ T cells provide protection against systemic and mucosal Yersinia pseudotuberculosis infection

Prior studies indicated that CD8+ T cells responding to a surrogate single antigen expressed by Y. pseudotuberculosis, ovalbumin, were insufficient to protect against yersiniosis. Herein we tested the hypothesis that CD8+ T cells reactive to the natural Yersinia antigen YopE would be more effective at providing mucosal protection. We first confirmed that immunization with the attenuated ksgA- strain of Y. pseudotuberculosis generated YopE-specific CD8+ T cells. These T cells were protective against challenge with virulent Listeria monocytogenes expressing secreted YopE. Mice immunized with an attenuated L. monocytogenes YopE+ strain generated large numbers of functional YopE-specific CD8+ T cells, and initially controlled a systemic challenge with virulent Y. pseudotuberculosis, yet eventually succumbed to yersiniosis. Mice vaccinated with a YopE peptide and cholera toxin vaccine generated robust T cell responses, providing protection to 60% of the mice challenged mucosally but failed to show complete protection against systemic infection with virulent Y. pseudotuberculosis. These studies demonstrate that vaccination with recombinant YopE vaccines can generate YopE-specific CD8+ T cells, that can provide significant mucosal protection but these cells are insufficient to provide sterilizing immunity against systemic Y. pseudotuberculosis infection. Our studies have implications for Yersinia vaccine development studies.

Flagellin-Mediated Protection against Intestinal Yersinia pseudotuberculosis Infection Does Not Require Interleukin-22

Signaling through Toll-like receptors (TLRs), the main receptors in innate immunity, is essential for the defense of mucosal surfaces. It was previously shown that systemic TLR5 stimulation by bacterial flagellin induces an immediate, transient interleukin-22 (IL-22)-dependent antimicrobial response to bacterial or viral infections of the mucosa. This process was dependent on the activation of type 3 innate lymphoid cells (ILCs). The objective of the present study was to analyze the effects of flagellin treatment in a murine model of oral infection with Yersinia pseudotuberculosis (an invasive, Gram-negative, enteropathogenic bacterium that targets the small intestine). We found that systemic administration of flagellin significantly increased the survival rate after intestinal infection (but not systemic infection) by Y. pseudotuberculosis This protection was associated with a low bacterial count in the gut and the spleen. In contrast, no protection was afforded by administration of the TLR4 agonist lipopolysaccharide, suggesting the presence of a flagellin-specific effect. Lastly, we found that TLR5- and MyD88-mediated signaling was required for the protective effects of flagellin, whereas neither lymphoid cells nor IL-22 was involved.

[CONSTRUCTION OF A TEST-SYSTEM WITH NANOPARTICLES OF COLLOID SILVER FOR DETECTION OF PSEUDOTUBERCULOSIS AND INTESTINAL YERSINIOSIS FOR CAUSATIVE AGENTS IN DOT-IMMUNOASSAY]

AIM

Construction of an immunologic test-system for detection of causative agents of enteropathogenic Yersinia (Yersinia pseudotuberculosis and Y. enterocolitica) by dot-immunoassay.

MATERIALS AND METHODS

Nenoparticles of colloid silver sized 5-9 nm were used as a marker of specific antibodies. IgG fraction was isolated from commercial antisera to Y. pseudotuberculosis (Ο:1) and Y. enterocolitica (Ο:3 and Ο:9). Testing of the obtained test-system was carried out on 20 strains of Y.pseudotuberculosis and Y. enterocolitica (10 of each species).

RESULTS

Dot-analysis had a specific character and detected enteropathogenic Yersinia at a level of 5-10⁵ - 8.10⁶ CFU/ml (100 - 1000 CFU in sample). Wherein cross-reaction with heterologic studied microorganisms - Escherichia coli, Salmonella typhimurium, Shigella flexneri, Yersina pestis EV - as not observed. A possibility of simultaneous detection and serotyping of Y. enterocolitica is shown, that is necessary for confirmation of their epidemic significance.

CONCLUSION

The developed test-systems allow to study micro volumes of the samples under study (1 μ1), are express (1.5 - 2h), highly sensitive and specific, technically simple and do not require the use of high-cost equipment, special training of the staff, may be successfully used in practical healthcar in laboratories with varying equiptment levels.

[PLASMID-ASSOCIATED VIRULENCE OF YERSINIA PSEUDOTUBERCULOSIS AND INFECTIOUS PROCESS]

Literature data regarding genetically-determined pathogenicity factors of Y pseudotuberculo- sis and associated manifestations of this infection caused by various plasmid types of the causative agent are generalized. Principal attention is given to features of cell-tissue alterations mediated by virulence plasmid pYV, as well as effects of pathogenicity of an understudied pVM82 plasmid present only in Y pseudotuberculosis sttains causing clinical-epidemic manifestation of the infec- tions as Far East scarlet-like fever (FESLF). The data obtained on the ability of far-eastern strains to produceYPMa super-antigenj Ypseudotuberculosis-derivative mitogenA, probablygive evidence on its key role in FESLF pathogenesis. Variability of damage of innate immunity cells and target- organs caused by various plasmid types of Y pseudotuberculosis by virulence could determine polymorphism of clinical-morphological manifestations of this infection. In-depth understanding of dependency of immune pathogenesis mechanisms of the disease on molecular characteristics of the causative agent opens up-perspectives of enhancement of diagnostics and prognosis of the severity of the course of pseudotuberculosis and yersiniosis in human in general.

Serotype O:8 isolates in the Yersinia pseudotuberculosis complex have different O-antigen gene clusters and produce various forms of rough LPS

In Yersinia pseudotuberculosis complex, the O-antigen of LPS is used for the serological characterization of strains, and 21 serotypes have been identified to date. The O-antigen biosynthesis gene cluster and corresponding O-antigen structure have been described for 18, leaving O:8, O:13 and O:14 unresolved. In this study, two O:8 isolates were examined. The O-antigen gene cluster sequence of strain 151 was near identical to serotype O:4a, though a frame-shift mutation was found in ddhD, while No. 6 was different to 151 and carried the O:1b gene cluster. Structural analysis revealed that No. 6 produced a deeply truncated LPS, suggesting a mutation within the waaF gene. Both ddhD and waaF were cloned and expressed in 151 and No. 6 strains, respectively, and it appeared that expression of ddhD gene in strain 151 restored the O-antigen on LPS, while waaF in No. 6 resulted in an LPS truncated less severely but still without the O-antigen, suggesting that other mutations occurred in this strain. Thus, both O:8 isolates were found to be spontaneous O-antigen-negative mutants derived from other validated serotypes, and we propose to remove this serotype from the O-serotyping scheme, as the O:8 serological specificity is not based on the O-antigen.

Co-expression of the C-terminal domain of Yersinia enterocolitica invasin enhances the efficacy of classical swine-fever-vectored vaccine based on human adenovirus

The use of adenovirus vector-based vaccines is a promising approach for generating antigen-specific immune responses. Improving vaccine potency is necessary in other approaches to address their inadequate protection for the majority of infectious diseases. This study is the first to reconstruct a recombinant replication-defective human adenovirus co-expressing E2 and invasin C-terminal (InvC) glycoproteins (rAd-E2-InvC). rAd-E2-InvC with 2 x 10(6) TCID50 was intramuscularly administered two times to CSFV-free pigs at 14 day intervals. No adverse clinical reactions were observed in any of the pigs after the vaccination. The CSFV E2-specific antibody titer was significantly higher in the rAd-E2-InvC group than that in the rAdV-E2 group as measured by NPLA and blocking ELISA. Pigs immunized with rAd-E2-InvC were completely protected against lethal challenge. Neither CSFV RNA nor pathological changes were detected in the tissues after CSFV challenge. These results demonstrate that rAd-E2-InvC could be an alternative to the existing CSF vaccine. Moreover, InvC that acts as an adjuvant could enhance the immunogenicity of rAdV-E2 and induce high CSFV E2-specific antibody titer and protection level.

Complete Protection against Pneumonic and Bubonic Plague after a Single Oral Vaccination

BACKGROUND

No efficient vaccine against plague is currently available. We previously showed that a genetically attenuated Yersinia pseudotuberculosis producing the Yersinia pestis F1 antigen was an efficient live oral vaccine against pneumonic plague. This candidate vaccine however failed to confer full protection against bubonic plague and did not produce F1 stably.

METHODOLOGY/PRINCIPAL FINDINGS

The caf operon encoding F1 was inserted into the chromosome of a genetically attenuated Y. pseudotuberculosis, yielding the VTnF1 strain, which stably produced the F1 capsule. Given orally to mice, VTnF1 persisted two weeks in the mouse gut and induced a high humoral response targeting both F1 and other Y. pestis antigens. The strong cellular response elicited was directed mostly against targets other than F1, but also against F1. It involved cells with a Th1-Th17 effector profile, producing IFNγ, IL-17, and IL-10. A single oral dose (108 CFU) of VTnF1 conferred 100% protection against pneumonic plague using a high-dose challenge (3,300 LD50) caused by the fully virulent Y. pestis CO92. Moreover, vaccination protected 100% of mice from bubonic plague caused by a challenge with 100 LD50 Y. pestis and 93% against a high-dose infection (10,000 LD50). Protection involved fast-acting mechanisms controlling Y. pestis spread out of the injection site, and the protection provided was long-lasting, with 93% and 50% of mice surviving bubonic and pneumonic plague respectively, six months after vaccination. Vaccinated mice also survived bubonic and pneumonic plague caused by a high-dose of non-encapsulated (F1-) Y. pestis.

SIGNIFICANCE

VTnF1 is an easy-to-produce, genetically stable plague vaccine candidate, providing a highly efficient and long-lasting protection against both bubonic and pneumonic plague caused by wild type or un-encapsulated (F1-negative) Y. pestis. To our knowledge, VTnF1 is the only plague vaccine ever reported that could provide high and durable protection against the two forms of plague after a single oral administration.

CCR2+ Inflammatory Dendritic Cells and Translocation of Antigen by Type III Secretion Are Required for the Exceptionally Large CD8+ T Cell Response to the Protective YopE69-77 Epitope during Yersinia Infection

During Yersinia pseudotuberculosis infection of C57BL/6 mice, an exceptionally large CD8⁺ T cell response to a protective epitope in the type III secretion system effector YopE is produced. At the peak of the response, up to 50% of splenic CD8⁺ T cells recognize the epitope YopE_69-77. The features of the interaction between pathogen and host that result in this large CD8⁺ T cell response are unknown. Here, we used Y. pseudotuberculosis strains defective for production, secretion and/or translocation of YopE to infect wild-type or mutant mice deficient in specific dendritic cells (DCs). Bacterial colonization of organs and translocation of YopE into spleen cells was measured, and flow cytometry and tetramer staining were used to characterize the cellular immune response. We show that the splenic YopE_69-77-specific CD8⁺ T cells generated during the large response are polyclonal and are produced by a “translocation-dependent” pathway that requires injection of YopE into host cell cytosol. Additionally, a smaller YopE_69-77-specific CD8⁺ T cell response (~10% of the large expansion) can be generated in a “translocation-independent” pathway in which CD8α⁺ DCs cross present secreted YopE. CCR2-expressing inflammatory DCs were required for the large YopE_69-77-specific CD8⁺ T cell expansion because this response was significantly reduced in Ccr2^-/- mice, YopE was translocated into inflammatory DCs in vivo, inflammatory DCs purified from infected spleens activated YopE_69-77-specific CD8⁺ T cells ex vivo and promoted the expansion of YopE_69-77-specific CD8⁺ T cells in infected Ccr2^-/- mice after adoptive transfer. A requirement for inflammatory DCs in producing a protective CD8⁺ T cell response to a bacterial antigen has not previously been demonstrated. Therefore, the production of YopE_69-77-specific CD8⁺ T cells by inflammatory DCs that are injected with YopE during Y. pseudotuberculosis infection represents a novel mechanism for generating a massive and protective adaptive immune response.

Dendritic cells (DCs) direct host protective adaptive immune responses during infection. How different subpopulations of DCs contribute to the formation of antigen-specific CD8⁺ T cells is incompletely understood. Infection of C57BL/6 mice with the bacterial pathogen Yersinia pseudotuberculosis results in the production of an exceptionally large CD8⁺ T cell response to an epitope in the type III secretion system effector YopE. Here, we show that this large CD8⁺ T cell response requires translocation of YopE into inflammatory DCs, which express CCR2 and accumulate in infected tissues. In contrast, when mice are infected with a Y. pseudotuberculosis strain that can secrete but not translocate YopE, a smaller response is seen, and under these conditions the generation of YopE-specific CD8⁺ T cell requires CD8α⁺ DCs. Our results indicate that distinct DC subsets participate in constructing the CD8⁺ T cell response to secreted, versus translocated, YopE. Furthermore our data indicate that inflammatory DCs are a driving force behind the massive CD8⁺ T cell response to a protective epitope in a bacterial virulence factor that is translocated into host cells.

Homology analysis and cross-immunogenicity of OmpA from pathogenic Yersinia enterocolitica, Yersinia pseudotuberculosis and Yersinia pestis

The outer membrane protein A (OmpA) is one of the intra-species conserved proteins with immunogenicity widely found in the family of Enterobacteriaceae. Here we first confirmed OmpA is conserved in the three pathogenic Yersinia: Yersinia pestis, Yersinia pseudotuberculosis and pathogenic Yersinia enterocolitica, with high homology at the nucleotide level and at the amino acid sequence level. The identity of ompA sequences for 262 Y. pestis strains, 134 Y. pseudotuberculosis strains and 219 pathogenic Y. enterocolitica strains are 100%, 98.8% and 97.7% similar. The main pattern of OmpA of pathogenic Yersinia are 86.2% and 88.8% identical at the nucleotide and amino acid sequence levels, respectively. Immunological analysis showed the immunogenicity of each OmpA and cross-immunogenicity of OmpA for pathogenic Yersinia where OmpA may be a vaccine candidate for Y. pestis and other pathogenic Yersinia.

Natural Killer Cells Mediate Protection against Yersinia pseudotuberculosis in the Mesenteric Lymph Nodes

Natural killer cells play a crucial role in the initial defense against bacterial pathogens. The crosstalk between host cells infected with intracellular pathogens and NK cells has been studied intensively, but not much attention has been given to characterize the role of NK cells in the response to extracellular bacterial pathogens such as yersiniae. In this study we used antibody-mediated NK cell depletion to address the importance of this immune cell type in controlling a Y. pseudotuberculosis infection. Analysis of the bacterial counts was used to follow the infection and flow cytometry was performed to characterize the composition and dynamic of immune cells. Depletion of NK cells led to higher bacterial loads within the mesenteric lymph nodes. We further show that in particular CD11b⁺ CD27⁺ NK cells which express higher levels of the activation marker CD69 increase within the mesenteric lymph nodes during a Y. pseudotuberculosis infection. Moreover, in response to the activation NK cells secrete higher levels of IFNy, which in turn triggers the production of the proinflammatory cytokine TNFα. These results suggest, that NK cells aid in the clearance of Y. pseudotuberculosis infections mainly by triggering the expression of proinflammatory cytokines manipulating the host immune response.

[IMMUNOCHEMICAL ACTIVITY OF YERSINIA PSEUDOTUBERCULOSIS B-ANTIGEN]

A hybridoma panel producing monoclonal antibodies to immunochemically non-identical antigenic epitopes of the protein nature located in outer membrane of Yersinia pseudotuberculosis was obtained. It was revealed that the previously identified B-antigen protecting laboratory animals from experimental plague was detected using both monoclonal antibodies against mentioned protein determinants and the determinants of lipopolysaccharide O-side chains. The B-antigen is a component of the Y. pseudotuberculosis outer membrane, egested in the form of the vesicles (OMVs) by bacteria cultivated in fluid nutrient medium.

The GAP activity of type III effector YopE triggers killing of Yersinia in macrophages

The mammalian immune system has the ability to discriminate between pathogens and innocuous microbes by detecting conserved molecular patterns. In addition to conserved microbial patterns, the mammalian immune system may recognize distinct pathogen-induced processes through a mechanism which is poorly understood. Previous studies have shown that a type III secretion system (T3SS) in Yersinia pseudotuberculosis leads to decreased survival of this bacterium in primary murine macrophages by unknown mechanisms. Here, we use colony forming unit assays and fluorescence microscopy to investigate how the T3SS triggers killing of Yersinia in macrophages. We present evidence that Yersinia outer protein E (YopE) delivered by the T3SS triggers intracellular killing response against Yersinia. YopE mimics eukaryotic GTPase activating proteins (GAPs) and inactivates Rho GTPases in host cells. Unlike wild-type YopE, catalytically dead YopER144A is impaired in restricting Yersinia intracellular survival, highlighting that the GAP activity of YopE is detected as a danger signal. Additionally, a second translocated effector, YopT, counteracts the YopE triggered killing effect by decreasing the translocation level of YopE and possibly by competing for the same pool of Rho GTPase targets. Moreover, inactivation of Rho GTPases by Clostridium difficile Toxin B mimics the effect of YopE and promotes increased killing of Yersinia in macrophages. Using a Rac inhibitor NSC23766 and a Rho inhibitor TAT-C3, we show that macrophages restrict Yersinia intracellular survival in response to Rac1 inhibition, but not Rho inhibition. In summary, our findings reveal that primary macrophages sense manipulation of Rho GTPases by Yersinia YopE and actively counteract pathogenic infection by restricting intracellular bacterial survival. Our results uncover a new mode of innate immune recognition in response to pathogenic infection.

The type III secretion system (T3SS) is a macromolecular protein export pathway found in gram-negative bacteria. It delivers bacterial toxins into eukaryotic cells to promote pathogenic infection. T3SSs and the bacterial toxins delivered are critical arsenals for many bacterial pathogens of clinical significance, such as Yersinia, Salmonella and Shigella. On the other hand, the mammalian immune system may recognize the T3SS as a danger signal to signify pathogenic infection, and to stimulate appropriate defense against pathogens. Here, we show that the innate immune system recognizes the activity of YopE delivered by the Yersinia T3SS. Modulation of host Rho GTPases by YopE elicits a defensive response, which results in killing of bacteria in host cells. Inhibition of host Rho GTPases by Clostridium difficile Toxin B, another bacterial toxin, mimics the YopE-triggered killing effect. Our study demonstrates that host cells sense manipulation of Rho GTPases by bacterial toxins as a surveillance mechanism, revealing new insights into innate immune recognition of pathogenic infections.

[Development and testing of an enzyme immunoassay-based monoclonal test system for the detection of the Yersinia pestis V antigen]

An enzyme immunoassay-based test system for Y. pestis V antigen detection was developed. The specificity and sensitivity of this system met the requirements for medical immunobiological preparations for the identification of causative agents of highly fatal diseases. The sensitivity of the test system was assessed, and its high specificity was also demonstrated: the test system did not detect bacterial cells of closely related (four Y. pseudotuberculosis strains) and heterologous microorganism strains. The test system developed was able to detect the V antigen at concentrations as low as 2.0 ng/mL in cells of nine experimental Y. pestis cultures. The obtained preparation can be recommended for use in laboratory diagnostics of plaque.

[Study of Yersinia pseudotuberculosis surface antigen epitopes using monoclonal antibodies]

A study of the influence of exogenous factors on the immunochemical activity of the bacterium Yersinia pseudotuberculosis and lipopolysaccharide preparations isolated from bacteria was performed using monoclonal antibodies. It was shown that the hybridomas that were obtained in this work produce antibodies against different and, most likely, species-specific epitopes associated with lipopolysaccharide O side chains. The antibody concentrations produced increased with a decrease in the temperature, at which the bacteria were cultivated. An inhibitory effect of proteinase K, pepsin, and trypsin on the immunochemical activity of bacterial cells, determined using a solid-phase enzyme immunoassay, was demonstrated. Treatment with sodium periodate showed no uniform effect on the reactions between monoclonal antibodies and antigens (lipopolysaccharides and microbial cells), as adjudged by an immunoassay, which is most likely a consequence of the different localization of lipopolysaccharide epitopes recognized by the antibodies from four hybridomas.

Molecular analysis of a novel Toll/interleukin-1 receptor (TIR)-domain containing virulence protein of Y. pseudotuberculosis among Far East scarlet-like fever serotype I strains

Pathogenicity of Yersinia pseudotuberculosis is determined by an arsenal of virulence factors. Particularly, the Yersinia outer proteins (Yops) and the Type III secretion system (T3SS) encoded on the pYV virulence plasmid are required for Yersinia pathogenicity. A specific group of Y. pseudotuberculosis, responsible for the clinical syndrome described as Far East scarlet-like fever (FESLF), is known to have an altered virulence gene cluster. Far East strains cause unique clinical symptoms for which the pYV virulence plasmid plays apparently a rather secondary role. Here, we characterize a previously unknown protein of Y. pseudotuberculosis serotype I strains (TcpYI) which can be found particularly among the FESLF strain group. The TcpYI protein shares considerable sequence homology to members of the Toll/IL-1 receptor family. Bacterial TIR domain containing proteins (Tcps) interact with the innate immune system by TIR-TIR interactions and subvert host defenses via individual, multifaceted mechanisms. In terms of virulence, it appears that the TcpYI protein of Y. pseudotuberculosis displays its own virulence phenotype compared to the previously characterized bacterial Tcps. Our results clearly demonstrate that TcpYI increases the intracellular survival of the respective strains in vitro. Furthermore, we show here that the intracellular survival benefit of the wild-type strain correlates with an increase in tcpYI gene expression inside murine macrophages. In support of this, we found that TcpYI enhances the survival inside the spleens of mice in a mouse model of peritonitis. Our results may point toward involvement of the TcpYI protein in inhibition of phagocytosis, particularly in distinct Y. pseudotuberculosis strains of the FESLF strain group where the pYV virulence plasmid is absent.

Hemophagocytic macrophages in murine typhoid fever have an anti-inflammatory phenotype

Histiocytes are white blood cells of the monocytic lineage and include macrophages and dendritic cells. In patients with a variety of infectious and noninfectious inflammatory disorders, histiocytes can engulf nonapoptotic leukocytes and nonsenescent erythrocytes and thus become hemophagocytes. We report here the identification and characterization of splenic hemophagocytes in a natural model of murine typhoid fever. The development of a flow-cytometric method allowed us to identify hemophagocytes based on their greater than 6N (termed 6N+) DNA content. Characterization of the 6N+ population from infected mice showed that these cells consist primarily of macrophages rather than dendritic cells and contain T lymphocytes, consistent with hemophagocytosis. Most 6N+ macrophages from Salmonella enterica serovar Typhimurium-infected mice contain intact DNA, consistent with hemophagocytosis. In contrast, most 6N+ macrophages from control mice or mice infected with a different bacterial pathogen, Yersinia pseudotuberculosis, contain damaged DNA. Finally, 6N+ splenic macrophages from S. Typhimurium-infected mice express markers consistent with an anti-inflammatory M2 activation state rather than a classical M1 activation state. We conclude that macrophages are the predominant splenic hemophagocyte in this disease model but not in Y. pseudotuberculosis-infected mice. The anti-inflammatory phenotype of hemophagocytic macrophages suggests that these cells contribute to the shift from acute to chronic infection.

[The mode of spot test of plague and pseudotuberculosis agents mix cultures]

It is supposed to implement the polymerase chain reaction with mix of two pairs of "chromosome" primers "vlm12for'/"IS216rev" and "JS for"/JSrev" species-specific for Y. pestis and Y. psdtbc correspondingly in spot test of plague and pseudotuberculosis. The additional immunodiagnostics is applied to find defective and full-fledged on plague bacteria F1-antigen synthesis in the volume agglomeration reaction and paragglutination with diagnosticums of plasmid-dependent F1 antigen and chromosome FV determined antigen. This mode is characterized by more effectiveness and lesser labor intensiveness. It accelerates the detection of the mix of two agents in bacterial inoculations, organs bioassays and other materials. Also this mode facilitates the analysis of mix cultures of agents of plague and pseudotuberculosis, obtained in "mixed" nidi, the component identification, differentiation and isolation of pure growths of both Yersinia.

[Immunogenic and protective properties of nanosized constructs based on tubular immunostimulating complexes and pore forming protein of Yersinia pseudotuberculosis]

AIM

Evaluation of immunogenic and protective properties of constructs based on subunit porin antigen from Yersinia pseudotuberculosis, immunostimulating complexes (ISCOM) and tubular immunostimulating (TI) complexes.

MATERIALS AND METHODS

Porin antibodies and blood serum cytokines were determined by using EIA. Porin-specific cell immunity was evaluated by DTH reaction inflammation index. Protective activity of porin formulations was determined by measuring specific gravity of animals surviving Yersinia pseudotuberculosis lethal challenge.

RESULTS

Porin in TI complexes develops higher immunogenicity when compared with individual protein or protein with complete Freunds adjuvant. Porin in TI complexes develops higher protective activity, inhibits interferon synthesis in mice. Incorporation of porin into TI complexes results in neutralization of porin suppressive activity against DTH mechanisms and interferon system.

CONCLUSION

TI complexes may be used as perspective carriers for bacterial antigens. TI complexes have adjuvant properties and can provide protective properties to porin vaccine constructs.

Yersinia pseudotuberculosis is resistant to killing by human neutrophils

The interaction between human neutrophils and the Gram negative gastrointestinal pathogen Yersinia pseudotuberculosis was investigated in vitro. Despite the wealth of data describing how Yersinia can affect the function of neutrophils, there are no published studies describing if neutrophil cells can affect the viability of Y. pseudotuberculosis. The wild-type IP32953 strain of Y. pseudotuberculosis was found to be resistant to killing by human neutrophils. Confocal examination and flow-cytometric analysis of this interaction revealed that bacteria were taken up.

Innate immune recognition of Yersinia pseudotuberculosis type III secretion

Specialized protein translocation systems are used by many bacterial pathogens to deliver effector proteins into host cells that interfere with normal cellular functions. How the host immune system recognizes and responds to this intrusive event is not understood. To address these questions, we determined the mammalian cellular response to the virulence-associated type III secretion system (T3SS) of the human pathogen Yersinia pseudotuberculosis. We found that macrophages devoid of Toll-like receptor (TLR) signaling regulate expression of 266 genes following recognition of the Y. pseudotuberculosis T3SS. This analysis revealed two temporally distinct responses that could be separated into activation of NFkappaB- and type I IFN-regulated genes. Extracellular bacteria were capable of triggering these signaling events, as inhibition of bacterial uptake had no effect on the ensuing innate immune response. The cytosolic peptidoglycan sensors Nod1 and Nod2 and the inflammasome component caspase-1 were not involved in NFkappaB activation following recognition of the Y. pseudotuberculosis T3SS. However, caspase-1 was required for secretion of the inflammatory cytokine IL-1beta in response to T3SS-positive Y. pseudotuberculosis. In order to characterize the bacterial requirements for induction of this novel TLR-, Nod1/2-, and caspase-1-independent response, we used Y. pseudotuberculosis strains lacking specific components of the T3SS. Formation of a functional T3SS pore was required, as bacteria expressing a secretion needle, but lacking the pore-forming proteins YopB or YopD, did not trigger these signaling events. However, nonspecific membrane disruption could not recapitulate the NFkappaB signaling triggered by Y. pseudotuberculosis expressing a functional T3SS pore. Although host cell recognition of the T3SS did not require known translocated substrates, the ensuing response could be modulated by effectors such as YopJ and YopT, as YopT amplified the response, while YopJ dampened it. Collectively, these data suggest that combined recognition of the T3SS pore and YopBD-mediated delivery of immune activating ligands into the host cytosol informs the host cell of pathogenic challenge. This leads to a unique, multifactorial response distinct from the canonical immune response to a bacterium lacking a T3SS.

CD8(+) T cells restrict Yersinia pseudotuberculosis infection: bypass of anti-phagocytosis by targeting antigen-presenting cells

All Yersinia species target and bind to phagocytic cells, but uptake and destruction of bacteria are prevented by injection of anti-phagocytic Yop proteins into the host cell. Here we provide evidence that CD8⁺ T cells, which canonically eliminate intracellular pathogens, are important for restricting Yersinia, even though bacteria are primarily found in an extracellular locale during the course of disease. In a model of infection with attenuated Y. pseudotuberculosis, mice deficient for CD8⁺ T cells were more susceptible to infection than immunocompetent mice. Although exposure to attenuated Y. pseudotuberculosis generated T_H1-type antibody responses and conferred protection against challenge with fully virulent bacteria, depletion of CD8⁺ T cells during challenge severely compromised protective immunity. Strikingly, mice lacking the T cell effector molecule perforin also succumbed to Y. pseudotuberculosis infection. Given that the function of perforin is to kill antigen-presenting cells, we reasoned that cell death marks bacteria-associated host cells for internalization by neighboring phagocytes, thus allowing ingestion and clearance of the attached bacteria. Supportive of this model, cytolytic T cell killing of Y. pseudotuberculosis–associated host cells results in engulfment by neighboring phagocytes of both bacteria and target cells, bypassing anti-phagocytosis. Our findings are consistent with a novel function for cell-mediated immune responses protecting against extracellular pathogens like Yersinia: perforin and CD8⁺ T cells are critical for hosts to overcome the anti-phagocytic action of Yops.

Pathogenic Yersinia are bacteria that cause diverse diseases such as gastroenteritis and plague. Yersinia binds to specialized immune cells called macrophages, which attempt to engulf and destroy the bacteria. The bacteria resist destruction by injecting proteins called Yops into macrophages, which stops the engulfment process. Yersinia thus survives as attached but extracellular bacteria to cause disease. Yersinia disease can be prevented by immunization. In this study, we identified one mechanism of protective immunity—that host cells called CD8⁺ T lymphocytes are important to restrict Yersinia infection. This observation is unusual because CD8⁺ T cells generally protect against intracellular pathogens: T cells destroy the host cell harboring the pathogen, thus preventing the pathogen's replication. We present data consistent with the model that CD8⁺ T cells can also restrict extracellular bacteria by showing that T cells target host cells with extracellularly attached Yersinia, thus allowing the host cells and associated bacteria to be engulfed and removed by neighboring macrophages.

[The autoagglutination factor of plague pathogen--cross-reacting antigen]

An antigen similar to the autoagglutination factor (AF) of plague pathogen in immunochemical specificity was sought in 22 bacterial species. For this, an immunoglobulin anti-AF diagnosticum that is the sheep erythrocytes sensitized with rabbit immune serum to the AF preparation isolated from the plasmid-free variant of the Yersinia pestis strain EV76. The bacteriological study applying a passive hemagglutination assay revealed AF-like antigens not only in all study strains (n = 30) of Y. pestis, but also in Yersinia pseudotuberculosis, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Proteus vulgaris. These bacteria were used to prepare AF = like antigen preparations that reacted with rabbit anti-AF serum in dot blot immunoassay. Also, as Y. pestis, AF-like antigens in polyacrylamide gel were detected as multiple protein bands that differed in mobility in Yersiniae and heterologous bacteria. Differences were found in the properties of AF-line antigens of 5 species of bacteria (sensitivity to temperature and formalin, binding to the cell surface, which enabled differentiation of serological reactions caused by AP-like antigens of other bacteria. Thus, Y. pestis AF is a cross-reacting antigen that, despite its immunochemical similarity with AF-like antigens of other bacteria, was ascertained to differ from them in properties. The findings are of interest for searching for new diagnostic tests to detect the Cafl- strains of the plague pathogen and for differentiating the causative organisms of plague and pseudotuberculosis.

[Influence of cultivation temperature of Yersinia pseudotuberculosis on the immunobiological properties of lipopolysaccharide]

AIM

To study relationship between Yersinia pseudotuberculosis cultivation temperature and immunobiological properties of lypopolysaccharide (LPS).

MATERIALS AND METHODS

LPS producing strain--Yersinia pseudotuberculosis 164/84 OX; experimental animal--guinea pigs, rabbits; methods--immunochemical (indirect hemagglutionation assay, RDP), physico-chemical (electrophoresis, gas-liquid chromatography), standard biochemical and statistical methods.

RESULTS

It was established that increase of Yersinia pseudotuberculosis cultivation temperature from 10 degrees C to 37 degrees C was associated with attenuation of LPS toxicity in guinea pigs, decrease of its immunochemical activity and contents and degree of acylation of 3OH-14:0 hydoxyacid as well as amount of electrophoretically detected O-side chains. It was assumed that the polysaccharide component plays its role in LPS toxicity.

CONCLUSION

Relation between Yersinia pseudotuberculosis cultivation temperature and structural and functional properties of LPS preparations obtained from the culture was determined.

[Modulating effect of serotonin on the development of human leukocytes apoptosis induced by Yersinia]

Effect of biogenic amine serotonin on the development of human blood leukocytes during interaction with species from Yersinia genus (Y. pestis EV, Y. pseudotuberculosis serovars I and IV, Y. enterocolitica serovars 09 and 03) was studied in model system in vitro using flow cytofluorometry. Serotonin in concentration 10(-5) M had differently marked effects on Yersinia spp.-induced apoptosis of leukocytes. Pattern of the observed changes depended from species and serovar of Yersinia. Serotonin inhibited development of early (after 6 hours) apoptosis of leukocytes induced by Y. pestis and Y. pseudotuberculosis serovar I.

[Immunostimulatory characteristics of a novel carrier on the basis of cucumarioside A2-2 and monogalactosyldiacylgycerol]

A novel antigen carrier has been formulated on the basis of a cucumarioside-A2-2 triterpene glycoside (CD) complex with cholesterol and monogalactosyldiacylglycerol from Ahnfeltia tobuchiensis (MGDG(At)) and Ulva fenestrate (MGDG(Uf)). Morphological and immunostimulative characteristics of the carrier were studied. Electron microscopy experiments demonstrated the formation of homogeneous tubular structures in a mixture of CD, cholesterol, and MGDG in molar ratio of 1:2:3. In animals immunized by the carrier bearing pore forming protein monomer of pseudotuberculosis agent CD and MGDG synergically affected synthesis of specific antibodies, interleukin-2, and gamma-interferon and delayed hypersensitivity reaction when compared to Freund's complete adjuvant or to immunostimulatory complexes between Quillaja saponaria saponins and phosphatidylcholine from egg yolk. The immunostimulatory effect depends upon the composition of polyunsaturated fatty acids of MGDG. The new tubular adjuvant carrier is a competitive adjuvant, as it includes CD obtained from far-eastern sea cucumber commercial species Cucumaria japonica, and MGDG from seaweed.

Type III secretion decreases bacterial and host survival following phagocytosis of Yersinia pseudotuberculosis by macrophages

Yersinia pseudotuberculosis uses a plasmid (pYV)-encoded type III secretion system (T3SS) to translocate a set of effectors called Yops into infected host cells. YopJ functions to induce apoptosis, and YopT, YopE, and YopH act to antagonize phagocytosis in macrophages. Because Yops do not completely block phagocytosis and Y. pseudotuberculosis can replicate in macrophages, it is important to determine if the T3SS modulates host responses to intracellular bacteria. Isogenic pYV-cured, pYV(+) wild-type, and yop mutant Y. pseudotuberculosis strains were allowed to infect bone marrow-derived murine macrophages at a low multiplicity of infection under conditions in which the survival of extracellular bacteria was prevented. Phagocytosis, the intracellular survival of the bacteria, and the apoptosis of the infected macrophages were analyzed. Forty percent of cell-associated wild-type bacteria were intracellular after a 20-min infection, allowing the study of the macrophage response to internalized pYV(+) Y. pseudotuberculosis. Interestingly, macrophages restricted survival of pYV(+) but not pYV-cured or DeltayopB Y. pseudotuberculosis within phagosomes: only a small fraction of the pYV(+) bacteria internalized replicated by 24 h. In addition, approximately 20% of macrophages infected with wild-type pYV(+) Y. pseudotuberculosis died of apoptosis after 20 h. Analysis of yop mutants expressing catalytically inactive effectors revealed that YopJ was important for apoptosis, while a role for YopE, YopH, and YopT in modulating macrophage responses to intracellular bacteria could not be identified. Apoptosis was reduced in Toll-like receptor 4-deficient macrophages, indicating that cell death required signaling through this receptor. Treatment of macrophages harboring intracellular pYV(+) Y. pseudotuberculosis with chloramphenicol reduced apoptosis, indicating that the de novo bacterial protein synthesis was necessary for cell death. Our finding that the presence of a functional T3SS impacts the survival of both bacterium and host following phagocytosis of Y. pseudotuberculosis suggests new roles for the T3SS in Yersinia pathogenesis.

[Humoral response to selected antigens of Yersinia enterocolitica and Yersinia pseudotuberculosis in the course of yersiniosis in humans. IV. Specificity of antigens]

The specificity of the lipopolisacharydes and released proteins (Yop) of Yersinia was tested using the sera of rabbits immunised with pathogenic and non-pathogenic strain of Y. enterocolitica and Y. pseudotuberculosis as well as selected sera of patients. The results of this study showed a cross-reactions between the different serotypes of Y. enterocolitica with the strongest reactions between the pathogenic serotypes O:3 and O:9 and pathogenic serotype O:5,27 and non-pathogenic serotype O:5. Sera positive for B. burgdorferi and from patients with Graves' disease showed a slight cross-reactivity with Yop proteins of Yersinia. However, the higher cross-reactivity was observed between the LPS of Yersinia and Salmonella spp. Due to the evidence of cross-reactivity the results of serological investigations should be interpreted with caution.

[Biological and physico-chemical properties of Yersinia pseudotuberculosis bacterial culture having the fra-operon Yersinia pestis]

The biological and physico-chemical properties of cultures of two isogenous recombinant variants of Yersinia pseudotuberculosis were studied. The cell genomes of the cultures are distinguished from one another only by the presence or by the absence of the fra-operon, which is a determined attribute of the plague microbe capsule-forming process. The expression of the attribute is amplified by rising the microbial biomass cultivation temperature and stimulates the decrease in the viability of the bacteria and adaptation potential in vitro. In the warm-blooded owner organism the microbes of the capsule-forming recombinant variant are characterized by the greater residual pathogenicity and immunogenic ability to the experimental plague of the laboratory animals as compared to the reference-variant cells. These specific features could be explained by more expressed colonizing ability of the capsule-forming microbes provided by owner cells' stability to the phagocyte process.

[Elaboration of new adjuvant lipid-saponin complex and its use at experimental immunization by bacterial antigen]

Results of experiments on modification of immunostimulating complexes (ISCOM's) matrix by the replacement of the phospholipid for the glycolipid (monogalactosyldiacylglycerol) from sea macrophytes, and saponin QuillA to triterpene glycoside of cucumarioside A2-2 from Cucumaria japonica are shown. The resultant complexes include the morphological structures of two types: ISCOM-like structures with the characteristic morphology and sizes and also the tubular structures with diameter of approximately 40 nm and length of 150-400 nm. We have named these structures as TI-complexes. These TI-complexes exhibit considerably lower toxicity than ISCOM. They may include an amphiphilic protein antigen and provide immunoadjuvant effect during experimental vaccination. Under conditions of experimental immunization of mice by a weak immunogen--(subunit membrane pore protein from Y. pseudotuberculosis), TI-complexes with antigen provided stronger humoral immune response to antigen than the complexes of porin with classical ISCOM, liposomes and Freund's adjuvant. Thus, it's shown the prospect of the use of TI-complexes as a new type of adjuvant carriers for antigens.

[Laboratory diagnosis of Yersinia infection and its improvement]

Results of the bacteriological and serological tests of patients with Y. enterocolitica and Y. pseudotuberculosis infections for the period from 1994 to 2004 were analyzed. Main reasons of imperfect laboratory diagnostics were revealed, such as, low sensitivity of bacteriologic test, nonobservance of existing recommendations on diagnostics of Yersinia infections, performing of single but not repeated serologic test, absence of necessary laboratory equipment. Main ways of improving of quality of Y. enterocolitica infections and differential diagnostics were of Y. pseudotuberculosis defined.

Yersinia pseudotuberculosis superantigens

Yersinia pseudotuberculosis, a gastro-intestinal bacterium, produces three closely related T cell superantigens, YPMa, YPMb and YPMc, which have no significant sequence similarity to other proteins, let alone other bacterial superantigens. Y. pseudotuberculosisderived mitogen (YPM) has been shown to play a role in the pathogenesis of human and animal Y. pseudotuberculosis infection. The three-dimensional structure of YPMa, as determined by X-ray crystallography and nuclear magnetic resonance spectroscopy, exhibits a jelly roll fold, a structural motif not observed in other superantigens. YPMa is structurally most similar to virus capsid proteins and members of the tumour necrosis factor (TNF) superfamily. In the crystal structure, YPMa forms a trimer, another feature shared with virus capsid proteins and TNF superfamily proteins. However, in solution YPMa exists as a monomer, and any functional relevance of the trimer observed in the crystals is yet to be established. Structures of YPM bound to the T cell receptor and/or the major histocompatibility complex (MHC) are not yet available and mapping of existing mutagenesis data onto the three-dimensional structure of YPMa did not reveal potential T cell receptor/MHC binding sites. Knowledge of the structure will aid the design of functional studies aimed at further characterizing this superantigen.

[Humoral response to selected antigens of Yersinia enterocolitica and Yersinia pseudotuberculosis in the course of yersiniosis in humans. I. Occurrence of antibodies to enterobacterial common antigen (ECA)]

The antibodies against the Enterobacterial Common Antigen (ECA) were detected using the ELISA in 293 serum samples collected from 185 persons suspected for yersiniosis, as well as 115 serum samples from healthy individuals (blood donors). The presence of IgA antibody in diagnostically significant titres for ECA were detected by ELISA in 3.5%, IgG in 13.0%, and IgM in 5.2% of blood donors. Statistical analysis showed that the frequency of detecting antibodies for ECA among the patients with yersiniosis was significantly higher (p < 0.05) in relation to the blood donors. Most frequently the elevated antibody levels were detected among patients with reactive arthritis (IgA 29.2%, IgG 35.4%, IgM 16.7%) while the most infrequent among patients with abdominal pain in acute phase of yersiniosis (IgA 14.9%, IgG 25.3%, IgM 19.5%). The level of antibodies for ECA, together with age increased reaching its peak, on the average, among individuals aged 41 - 60 years. In majority of the individuals studied antibodies of the IgG class reached the level much higher in relation to those of the IgA and IgM classes. The obtained results showed that the detection of antibodies to ECA may be useful in serodiagnosis of Yersinia infections.

Analysis of Kawasaki disease showing elevated antibody titres of Yersinia pseudotuberculosis

AIM

To elucidate a clinical difference between patients with Kawasaki disease documented with Yersinia pseudotuberculosis infection and patients with Kawasaki disease without Yersinia pseudotuberculosis infection.

PATIENTS AND METHODS

From January 1985 to July 2004, 452 patients were diagnosed with Kawasaki disease. Forty-two patients had elevated antibody titres of Yersinia pseudotuberculosis and/or positive stool culture (Yersinia-positive group). Three hundred and thirty patients had no elevated antibody titres (Yersinia-negative group). We compared the clinical characteristics retrospectively.

RESULTS

The age of onset in the Yersinia-positive group (3.05+/-2.20 y) was significantly higher than that in the Yersinia-negative group (2.31+/-2.05 y) (p=0.03). The age-adjusted statistical analysis demonstrated that the incidence of coronary artery lesions (dilatations plus aneurysms) in the Yersinia-positive group (22/42, 52.4%) was significantly higher than in the Yersinia-negative group (105/330, 31.8%) (p=0.001), and the incidence of additional administration of immunoglobulin in the Yersinia-positive group (13/36, 36.1%) was significantly higher than in the Yersinia-negative group (41/256, 16.0%) (p=0.004).

CONCLUSION

Our data suggest that Yersinia pseudotuberculosis infection might play a role in the developing mechanism of poor response to therapy and the tendency to develop coronary artery lesions in Kawasaki disease patients.

Intranasal inoculation of mice with Yersinia pseudotuberculosis causes a lethal lung infection that is dependent on Yersinia outer proteins and PhoP

Yersinia pseudotuberculosis infects many mammals and birds including humans, livestock, and wild rodents and can be recovered from the lungs of infected animals. To determine the Y. pseudotuberculosis factors important for growth during lung infection, we developed an intranasal model of infection in mice. Following intranasal inoculation, we monitored both bacterial growth in lungs and dissemination to systemic tissues. Intranasal inoculation with as few as 18 CFU of Y. pseudotuberculosis caused a lethal lung infection in some mice. Over the course of 7 days, wild-type Y. pseudotuberculosis replicated to nearly 1 x 10(8) CFU/g of lung in BALB/c mice, induced histopathology in lungs consistent with pneumonia, but disseminated sporadically to other tissues. In contrast, a Delta yopB deletion strain was attenuated in this model, indicating that translocation of Yersinia outer proteins (Yops) is essential for virulence. Additionally, a Delta yopH null mutant failed to grow to wild-type levels by 4 days postintranasal inoculation, but deletions of any other single effector YOP did not attenuate lung colonization 4 days postinfection. Strains with deletions in yopH and any one of the other known effector yop genes were more attenuated that the Delta yopH strain, indicating a unique role for yopH in lungs. In summary, we have characterized the progression of a lung infection with an enteric Yersinia pathogen and shown that YopB and YopH are important in lung colonization and dissemination. Furthermore, this lung infection model with Y. pseudotuberculosis can be used to test potential therapeutics against Yersinia and other gram-negative infections in lungs.

Oral inoculation with Type III secretion mutants of Yersinia pseudotuberculosis provides protection from oral, intraperitoneal, or intranasal challenge with virulent Yersinia

The enteric pathogen Yersinia pseudotuberculosis (Yptb) causes gastroenteritis, mesenteric lymphadenitis, and systemic infections in humans, livestock, and wild animals. Yptb Type III secretion system (pTTSS) mutants efficiently colonize lymphoid tissues, but not the gastrointestinal tract, spleen, or liver. Here, we show that a single oral inoculation of pTTSS mutants prevents morbidity in almost 100% of mice challenged intragastrically with virulent Yptb. In addition, a single oral inoculation of a pTTSS mutant protected 50% of mice challenged intraperitoneally or intranasally with virulent Yptb. In addition, the intranasally challenged mice that succumbed to infection lived significantly longer than non-immunized mice. Thus, pTTSS mutants can function as live attenuated vaccine when delivered orally. Potential uses for these attenuated strains include use as a livestock vaccine, a rodent plague control reagent in endemic areas around the world, and a vector for delivery of other antigens to the mesenteric lymph nodes.

The serodiagnosis of human infections with Yersinia enterocolitica and Yersinia pseudotuberculosis

The techniques of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting were evaluated for the serodiagnosis of human infections with Yersinia enterocolitica and Yersinia pseudotuberculosis. Lipopolysaccharide (LPS) was prepared from strains comprising four serogroups of Y. enterocolitica and five serogroups of Y. pseudotuberculosis, tested against 200 sera submitted to the Laboratory of Enteric Pathogens for routine serodiagnosis, and shown to contain antibodies to Yersinia LPS by agglutination. Forty four sera were found to contain antibodies that bound to one of the LPS preparations used in the immunoassay. Thirty five of the sera contained antibodies to the LPS of Y. enterocolitica O3, whilst three contained antibodies to the LPS of Y. enterocolitica O5, 27 and Y. enterocolitica O9 LPS respectively. Two sera had antibodies to the LPS of Y. pseudotuberculosis II and a single serum contained antibodies to Y. pseudotuberculosis IV. The SDS-PAGE-immunoblotting procedure described proved to be a reliable procedure for the serodiagnosis of infections with Y. enterocolitica and Y. pseudotuberculosis.

Yersinia pseudotuberculosis adhesins regulate tissue-specific colonization and immune cell localization in a mouse model of systemic infection

Yersinia pseudotuberculosis mutants deficient for the adhesins invasin and/or YadA were injected intravenously into BALB/c mice. Invasin expression inhibited colonization of the liver and spleen. YadA decreased liver colonization but promoted growth within the lung. The persistence of leukocytes within liver microabscesses correlated with enhanced colonization and lack of adhesin expression.

Mesenteric adenitis caused by Yersinia pseudotubercolosis in a patient subsequently diagnosed with Crohn’s disease of the terminal ileum

Although the association between inflammatory bowel disease and gastrointestinal infections has been suggested, the mechanisms involved in the pathogenesis of Crohn’s disease (CD) are still undetermined. We report the case of a man, who presented with mesenteric adenitis initially due to a Yersinia pseudotubercolosis infection, who was later diagnosed with Crohn’s disease. This case is in keeping with recent evidence in the literature which suggests that CD is a disease linked to abnormal immune responses to enteric bacteria in genetically susceptible individuals.

The proinflammatory response induced by wild-type Yersinia pseudotuberculosis infection inhibits survival of yop mutants in the gastrointestinal tract and Peyer's patches

Single-strain infections and coinfections are frequently used to assess roles of virulence factors in infected tissues. After oral inoculation of mice, Yersinia pseudotuberculosis yopE and yopH mutants colonize the intestines and Peyer's patches in single-strain infections but fail to persist in competition with wild-type Y. pseudotuberculosis, indicating that these two infection models provide different insights into the roles of Yops. To determine how wild-type Y. pseudotuberculosis hinders yop mutant survival, yop mutant colonization and host responses were investigated in several different infection models that isolated specific features of wild-type Y. pseudotuberculosis infection. Infection with wild-type Y. pseudotuberculosis caused significantly more inflammation than yop mutants. Results from coinfections of gamma interferon (IFN-gamma)-/- mice revealed that IFN-gamma-regulated defenses target these mutants, suggesting that YopE and YopH protect Y. pseudotuberculosis from these defenses in BALB/c mice. We developed an oral-intraperitoneal infection model to evaluate the effects of spleen and liver colonization by Y. pseudotuberculosis on yop mutants in the intestines. Spleen and liver infection increased inflammation and decreased yop mutant survival in the intestines, indicating that infection of these organs has consequences in intestinal tissues. Finally, competition infections with Y. pseudotuberculosis mutants with various abilities to induce inflammation demonstrated that survival of the yopE, but not the yopH, mutant was consistently decreased in inflamed tissues. In summary, infection with Y. pseudotuberculosis in intestinal and systemic sites induces intestinal inflammation, which decreases yop mutant survival. Thus, competition studies with wild-type yersiniae reveal critical roles of Yops in combating host responses to a normal virulent infection.

[Immunogenicity of B-antigen in experimental plague and pseudotuberculosis]

The results of the evaluation of the immunogenic properties of B-antigen, earlier identified in the culture fluid of Yersinia pseudotuberculosis submerged culture, with respect to experimental plague and pseudotuberculosis are presented. B-antigen has been shown to produce protective effect in guinea pigs and, probably, hamadryas baboons, but not in white mice infected with the causative agent of plague. Immunizaton with B-antigen protects guinea pigs from primary pneumonic plague caused by both capsule-forming and noncapsular Y. pestis virulent strains. Passive immunization with antibodies to B-antigen induces limitedly pronounced protective effect in guinea pigs and is not effective for white mice with respect to experimental plague. No active or passive protection of white mice or guinea pigs, infected with Y. pseudotuberculosis cultures, has been achieved by the injection of B-antigen or antibodies to it.