Candida albicans elicits protective allergic responses via platelet mediated T helper 2 and T helper 17 cell polarization.

Fungal airway infection (airway mycosis) is an important cause of allergic airway diseases such as asthma, but the mechanisms by which fungi trigger asthmatic reactions are poorly understood. Here, we leverage wild-type and mutant Candida albicans to determine how this common fungus elicits characteristic Th2 and Th17 cell-dependent allergic airway disease in mice. We demonstrate that rather than proteinases that are essential virulence factors for molds, C. albicans instead promoted allergic airway disease through the peptide toxin candidalysin. Candidalysin activated platelets through the Von Willebrand factor (VWF) receptor GP1bα to release the Wnt antagonist Dickkopf-1 (Dkk-1) to drive Th2 and Th17 cell responses that correlated with reduced lung fungal burdens. Platelets simultaneously precluded lethal pulmonary hemorrhage resulting from fungal lung invasion. Thus, in addition to hemostasis, platelets promoted protection against C. albicans airway mycosis through an antifungal pathway involving candidalysin, GP1bα, and Dkk-1 that promotes Th2 and Th17 responses.

The effect of ADAMTS13 on graft-versus-host disease.

Allogeneic haematopoietic stem cell transplantation (allo-HSCT) can potentially cure malignant blood disorders and benign conditions such as haemoglobinopathies and immunologic diseases. However, allo-HSCT is associated with significant complications. The most common and debilitating among them is graft-versus-host disease (GVHD). In GVHD, donor-derived T cells mount an alloimmune response against the recipient. The alloimmune response involves several steps, including recognition of recipient antigens, activation and proliferation of T cells in secondary lymphoid organs, and homing into GVHD-targeted organs. Adhesion molecules on T cells and endothelial cells mediate homing of T cells into lymphoid and non-lymphoid tissues. In this study, we showed that Von Willebrand factor (VWF), an adhesion molecule secreted by activated endothelial cells, plays an important role in mouse models of GVHD. We investigated the effect of the VWF-cleaving protease ADAMTS13 on GVHD. We found that ADAMTS13 reduced the severity of GVHD after bone marrow transplantation from C57BL6 donor to BALB/C recipient mice. A recombinant VWF-A2 domain peptide also reduced GVHD in mice. We showed that ADAMTS13 and recombinant VWF-A2 reduced the binding of T cells to endothelial cells and VWF in vitro, and reduced the number of T cells in lymph nodes, Peyer's patches and GVHD-targeted organs in vivo. We identified LFA-1 (αLß2) as the binding site of VWF on T cells. Our results showed that blocking T-cell homing by ADAMTS13 or VWF-A2 peptide reduced the severity of the GVHD after allo-HSCT, a potentially novel method for treating and preventing GVHD.

An incoherent feedforward loop formed by SirA/BarA, HilE and HilD is involved in controlling the growth cost of virulence factor expression by Salmonella Typhimurium.

An intricate regulatory network controls the expression of Salmonella virulence genes. The transcriptional regulator HilD plays a central role in this network by controlling the expression of tens of genes mainly required for intestinal colonization. Accordingly, the expression/activity of HilD is highly regulated by multiple factors, such as the SirA/BarA two-component system and the Hcp-like protein HilE. SirA/BarA positively regulates translation of hilD mRNA through a regulatory cascade involving the small RNAs CsrB and CsrC, and the RNA-binding protein CsrA, whereas HilE inhibits HilD activity by protein-protein interaction. In this study, we show that SirA/BarA also positively regulates translation of hilE mRNA through the same mentioned regulatory cascade. Thus, our results reveal a paradoxical regulation exerted by SirA/BarA-Csr on HilD, which involves simultaneous opposite effects, direct positive control and indirect negative control through HilE. This kind of regulation is called an incoherent type-1 feedforward loop (I1-FFL), which is a motif present in certain regulatory networks and represents a complex biological problem to decipher. Interestingly, our results, together with those from a previous study, indicate that HilE, the repressor component of the I1-FFL reported here (I1-FFLSirA/BarA-HilE-HilD), is required to reduce the growth cost imposed by the expression of the genes regulated by HilD. Moreover, we and others found that HilE is necessary for successful intestinal colonization by Salmonella. Thus, these findings support that I1-FFLSirA/BarA-HilE-HilD cooperates to control the precise amount and activity of HilD, for an appropriate balance between the growth cost and the virulence benefit generated by the expression of the genes induced by this regulator. I1-FFLSirA/BarA-HilE-HilD represents a complex regulatory I1-FFL that involves multiple regulators acting at distinct levels of gene expression, as well as showing different connections to the rest of the regulatory network governing Salmonella virulence.

Conformation-dependent blockage of activated VWF improves outcomes of traumatic brain injury in mice.

Traumatic brain injury-induced coagulopathy (TBI-IC) causes life-threatening secondary intracranial bleeding. Its pathogenesis differs mechanistically from that of coagulopathy arising from extracranial injuries and hemorrhagic shock, but it remains poorly understood. We report results of a study designed to test the hypothesis that von Willebrand factor (VWF) released during acute TBI is intrinsically hyperadhesive because its platelet-binding A1-domain is exposed and contributes to TBI-induced vascular leakage and consumptive coagulopathy. This hyperadhesive VWF can be selectively blocked by a VWF A2-domain protein to prevent TBI-IC and to improve neurological function with a minimal risk of bleeding. We demonstrated that A2 given through intraperitoneal injection or IV infusion reduced TBI-induced death by >50% and significantly improved the neurological function of C57BL/6J male mice subjected to severe lateral fluid percussion injury. A2 protected the endothelium from extracellular vesicle-induced injury, reducing TBI-induced platelet activation and microvesiculation, and preventing a TBI-induced hypercoagulable state. A2 achieved this therapeutic efficacy by specifically blocking the A1 domain exposed on the hyperadhesive VWF released during acute TBI. These results suggest that VWF plays a causal role in the development of TBI-IC and is a therapeutic target for this life-threatening complication of TBI.

Regulatory Evolution of the phoH Ancestral Gene in Salmonella enterica Serovar Typhimurium.

One important event for the divergence of Salmonella from Escherichia coli was the acquisition by horizontal transfer of the Salmonella pathogenicity island 1 (SPI-1), containing genes required for the invasion of host cells by Salmonella. HilD is an AraC-like transcriptional regulator in SPI-1 that induces the expression of the SPI-1 and many other acquired virulence genes located in other genomic regions of Salmonella. Additionally, HilD has been shown to positively control the expression of some ancestral genes (also present in E. coli and other bacteria), including phoH. In this study, we determined that both the gain of HilD and cis-regulatory evolution led to the integration of the phoH gene into the HilD regulon. Our results indicate that a HilD-binding sequence was generated in the regulatory region of the S. enterica serovar Typhimurium phoH gene, which mediates the activation of promoter 1 of this gene under SPI-1-inducing conditions. Furthermore, we found that repression by H-NS, a histone-like protein, was also adapted on the S. Typhimurium phoH gene and that HilD activates the expression of this gene in part by antagonizing H-NS. Additionally, our results revealed that the expression of the S. Typhmurium phoH gene is also activated in response to low phosphate but independently of the PhoB/R two-component system, known to regulate the E. coli phoH gene in response to low phosphate. Thus, our results indicate that cis-regulatory evolution has played a role in the expansion of the HilD regulon and illustrate the phenomenon of differential regulation of ortholog genes. IMPORTANCE Two mechanisms mediating differentiation of bacteria are well known: acquisition of genes by horizontal transfer events and mutations in coding DNA sequences. In this study, we found that the phoH ancestral gene is differentially regulated between Salmonella Typhimurium and Escherichia coli, two closely related bacterial species. Our results indicate that this differential regulation was generated by mutations in the regulatory sequence of the S. Typhimurium phoH gene and by the acquisition by S. Typhimurium of foreign DNA encoding the transcriptional regulator HilD. Thus, our results, together with those from an increasing number of studies, indicate that cis-regulatory evolution can lead to the rewiring and reprogramming of transcriptional regulation, which also plays an important role in the divergence of bacteria through time.

Role of the YehD fimbriae in the virulence-associated properties of enteroaggregative Escherichia coli.

The interaction of enteroaggregative Escherichia coli (EAEC) strains with the colonic gut mucosa is characterized by the ability of the bacteria to form robust biofilms, to bind mucin, and induce a local inflammatory response. These events are mediated by a repertoire of five different aggregative adherence fimbriae variants (AAF/I-V) typically encoded on virulence plasmids. In this study, we report the production in EAEC strains of a new YehD fimbriae (YDF), which is encoded by the chromosomal gene cluster yehABCD, also present in most E. coli strains. Immuno-labelling of EAEC strain 042 with anti-AAF/II and anti-YDF antibodies demonstrated the presence of both AAF/II and YDF on the bacterial surface. We investigated the role of YDF in cell adherence, biofilm formation, colonization of spinach leaves, and induction of pro-inflammatory cytokines release. To this aim, we constructed yehD deletion mutants in different EAEC backgrounds (strains 17-2, 042, 55989, C1010, 278-1, J7) each harbouring one of the five AAFs. The effect of the YDF mutation was strain dependent and AAF independent as the lack of YDF had a different impact on the phenotypes manifested by the different EAECs tested. Expression of the yehABCD operon in a E. coli K12 ORN172 showed that YDF is important for biofilm formation but not for adherence to HeLa cells. Lastly, screening of pro-inflammatory cytokines in supernatants of Caco-2 cells infected with EAEC strains 042 and J7 and their isogenic ΔyehD mutants showed that these mutants were significantly defective in release of IL-8 and TNF-α. This study contributes to the understanding of the complex and diverse mechanisms of adherence of EAEC strains and identifies a new potential target for preventive measures of gastrointestinal illness caused by EAEC and other E. coli pathogroups.

Aberrant Fibrin Clot Structure Visualized Ex Vivo in Critically Ill Patients With Severe Acute Respiratory Syndrome Coronavirus 2 Infection.

OBJECTIVES: Disseminated fibrin-rich microthrombi have been reported in patients who died from COVID-19. Our objective is to determine whether the fibrin clot structure and function differ between critically ill patients with or without COVID-19 and to correlate the structure with clinical coagulation biomarkers. DESIGN: A cross-sectional observational study. Platelet poor plasma was used to analyze fibrin clot structure; the functional implications were determined by quantifying clot turbidity and porosity. SETTING: ICU at an academic medical center and an academic laboratory. PATIENTS: Patients admitted from July 1 to August 1, 2020, to the ICU with severe acute respiratory syndrome coronavirus 2 infection confirmed by reverse transcription-polymerase chain reaction or patients admitted to the ICU with sepsis. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Blood was collected from 36 patients including 26 ICU patients with COVID-19 and 10 ICU patients with sepsis but without COVID-19 at a median of 11 days after ICU admission (interquartile range, 3-16). The cohorts were similar in age, gender, body mass index, comorbidities, Sequential Organ Failure Assessment (SOFA) score, and mortality. More patients with COVID-19 (100% vs 70%; p = 0.003) required anticoagulation. Ex vivo fibrin clots formed from patients with COVID-19 appeared to be denser and to have smaller pores than those from patients with sepsis but without COVID-19 (percent area of fluorescent fibrin 48.1% [SD, 16%] vs 24.9% [SD, 18.8%]; p = 0.049). The turbidity and flow-through assays corroborated these data; fibrin clots had a higher maximum turbidity in patients with COVID-19 compared with patients without COVID-19 (0.168 vs 0.089 OD units; p = 0.003), and it took longer for buffer to flow through these clots (216 vs 103 min; p = 0.003). In patients with COVID-19, d-dimer levels were positively correlated with percent area of fluorescent fibrin (ρ = 0.714, p = 0.047). Denser clots (assessed by turbidity and thromboelastography) and higher SOFA scores were independently associated with delayed clot lysis. CONCLUSIONS: We found aberrant fibrin clot structure and function in critically ill patients with COVID-19. These findings may contribute to the poor outcomes observed in COVID-19 patients with widespread fibrin deposition.

Public Health Actions to Control Measles Among Afghan Evacuees During Operation Allies Welcome - United States, September-November 2021.

On August 29, 2021, the United States government oversaw the emergent establishment of Operation Allies Welcome (OAW), led by the U.S. Department of Homeland Security (DHS) and implemented by the U.S. Department of Defense (DoD) and U.S. Department of State (DoS), to safely resettle U.S. citizens and Afghan nationals from Afghanistan to the United States. Evacuees were temporarily housed at several overseas locations in Europe and Asia* before being transported via military and charter flights through two U.S. international airports, and onward to eight U.S. military bases,† with hotel A used for isolation and quarantine of persons with or exposed to certain infectious diseases.§ On August 30, CDC issued an Epi-X notice encouraging public health officials to maintain vigilance for measles among Afghan evacuees because of an ongoing measles outbreak in Afghanistan (25,988 clinical cases reported nationwide during January-November 2021) (1) and low routine measles vaccination coverage (66% and 43% for the first and second doses, respectively, in 2020) (2).

High levels of von Willebrand factor with reduced specific activities in hospitalized patients with or without COVID-19.

The COVID-19 pandemic is often accompanied by severe respiratory illness and thrombotic complications. Von Willebrand Factor (VWF) levels are highly elevated in this condition. However, limited data are available on the qualitative activity of VWF in COVID-19. We measured plasma VWF levels quantitatively (VWF antigen) and qualitatively (ristocetin-induced platelet agglutination, glycoprotein IbM (GPIbM) binding, and collagen binding). Consistent with prior reports, VWF antigen levels were significantly elevated in hospitalized patients with or without COVID-19. The GPIbM and collagen binding activity-to-antigen ratios were significantly reduced, consistent with qualitative changes in VWF in COVID-19. Of note, critically ill hospitalized patients without COVID-19 had similar reductions in VWF activity-to-antigen ratios as patients with COVID-19. Our data suggest that qualitative changes in VWF in COVID-19 may not be specific to COVID-19. Future studies are warranted to determine the mechanisms responsible for qualitative changes in VWF in COVID-19 and other critical illnesses.• VWF levels were increased in COVID-19 compared to healthy controls.• VWF activity-to-antigen ratios were decreased in COVID-19 compared to healthy controls.• There were no differences in VWF activity-to-antigen ratios between hospitalized patients with or without COVID-19.• These findings are consistent with qualitative changes in VWF in systemic inflammation which are not specific to COVID-19.• Future studies are needed to define possible roles of changes in conformation or multimer length in the qualitative changes in VWF in systemic inflammation.

Recombinant Human Vimentin Binds to P-Selectin and Blocks Neutrophil Capture and Rolling on Platelets and Endothelium.

Leukocyte adhesion to vascular endothelium and platelets is an early step in the acute inflammatory response. The initial process is mediated through P-selectin glycoprotein ligand-1 (PSGL-1) on leukocytes binding to platelets adhered to endothelium and the endothelium itself via P-selectin. Although these interactions are generally beneficial, pathologic inflammation may occur in undesirable circumstances, such as in acute lung injury (ALI) and ischemia and reperfusion injury. Therefore, the development of novel therapies to attenuate inflammation may be beneficial. In this article, we describe the potential benefit of using a recombinant human vimentin (rhVim) on reducing human leukocyte adhesion to vascular endothelium and platelets under shear stress. The addition of rhVim to whole blood and isolated neutrophils decreased leukocyte adhesion to endothelial and platelet monolayers. Furthermore, rhVim blocked neutrophil adhesion to P-selectin-coated surfaces. Binding assays showed that rhVim binds specifically to P-selectin and not to its counterreceptor, PSGL-1. Finally, in an endotoxin model of ALI in C57BL/6J mice, treatment with rhVim significantly decreased histologic findings of ALI. These data suggest a potential role for rhVim in attenuating inflammation through blocking P-selectin-PSGL-1 interactions.

Identification of mutations in the S gene of hepatitis B virus in HIV positive Mexican patients with occult hepatitis B virus infection.

INTRODUCTION AND AIM: Occult hepatitis B virus infection (OBI) is characterized by the presence of replication-competent hepatitis B virus (HBV) DNA in the liver and/or serum of patients with undetectable levels of the HBV surface antigen (HBsAg). Due to the shared infection routes HIV positive patients are at higher risk of developing OBI, thus, the aim of this study was to determine the frequency of OBI in Mexican HIV-infected patients and to identify mutations in the HBV S gene that could be associated to the development of OBI. MATERIALS AND METHODS: Plasma samples from 50 HIV-infected patients with undetectable levels of the HBsAg were obtained and analyzed. The Core, PreS and S genes were amplified by nested PCR and sequenced by the Sanger method. To analyze HBV diversity in the OBI-positive patients, ten sequences of 762bp from the HBV S gene were selected, cloned, and subsequently sequenced for mutational analyses. RESULTS: OBI infection was found with a frequency of 36% (18/50). All the HBV sequences corresponded to the H genotype. The most common mutations were: C19Y, Q129H, E164D, and I195M, with a frequency of 44%, 36%, 39% and 48% respectively. CONCLUSIONS: In this study, we report the presence of OBI in a cohort of Mexican HIV-infected patients with an overall prevalence of 36%. Mutational analyses revealed that four non-silent mutations were frequent in different regions of the HBsAg gene, suggesting that they might be associated to the development of OBI in this population, nevertheless, further studies are required to determine their role in the pathogenesis of OBI.

Extracellular Vimentin/VWF (von Willebrand Factor) Interaction Contributes to VWF String Formation and Stroke Pathology.

Background and Purpose- VWF (von Willebrand factor) strings mediate spontaneous platelet adhesion in the vascular lumen, which may lead to microthrombi formation and contribute to stroke pathology. However, the mechanism of VWF string attachment at the endothelial surface is unknown. We tested the novel hypothesis that VWF strings are tethered to the endothelial surface through an interaction between extracellular vimentin and the A2 domain of VWF. We further explored the translational value of blocking this interaction in a model of ischemic stroke. Methods- Human endothelial cells and pressurized cerebral arteries were stimulated with histamine to elicit VWF string formation. Recombinant proteins and antibodies were used to block VWF string formation. Mice underwent transient middle cerebral artery occlusion with reperfusion. Just before recanalization, mice were given either vehicle or A2 protein (recombinant VWF A2 domain) to disrupt the vimentin/VWF interaction. Laser speckle contrast imaging was used to monitor cortical perfusion. Results- Pressurized cerebral arteries produced VWF strings following histamine stimulation, which were reduced in arteries from Vim KO (vimentin knockout) mice. VWF string formation was significantly reduced in endothelial cells incubated with A2 protein or antivimentin antibodies. Lastly, A2 protein treatment significantly improved cortical reperfusion after middle cerebral artery occlusion. Conclusions- We provide the first direct evidence of cerebral VWF strings and demonstrate that extracellular vimentin significantly contributes to VWF string formation via A2 domain binding. Lastly, we show that pharmacologically targeting the vimentin/VWF interaction through the A2 domain can promote improved reperfusion after ischemic stroke. Together, these studies demonstrate the critical role of VWF strings in stroke pathology and offer new therapeutic targets for treatment of ischemic stroke.

The CpxRA stress response system regulates virulence features of avian pathogenic Escherichia coli.

Avian pathogenic Escherichia coli (APEC) causes localized and systemic avian infections and is responsible for considerable economic losses in the poultry industry. This organism adheres and invades human and avian cells, however, the regulatory networks that dictate its virulence are largely unknown. The CpxRA two-component system is responsible for sensing and controlling outer-membrane stress and detecting misfolded proteins in the bacterial periplasmic space. CpxA is a membrane sensor kinase and CpxR is a cytoplasmic transcriptional regulator. In this study, we found that the CpxRA system regulates the virulence properties of APEC. Adherence, invasiveness, motility, production of type 1 fimbriae and biofilm were negatively affected in the ΔcpxA mutant indicating that the CpxA is required for full manifestation of these phenotypes. We also found that CpxR-P directly bound to the fimA promoter, locking the fimS region of type 1 fimbriae in the phase-OFF orientation. In addition, the absence of CpxA also reduced flagella production strongly suggesting that CpxRA regulates these two important surface organelles in APEC. This study provides compelling evidence of the role of the CpxRA two-component system in the regulation of virulence factors of avian pathogenic E. coli.

A Novel Interaction of the Catalytic Subunit of Protein Phosphatase 2A with the Adaptor Protein CIN85 Suppresses Phosphatase Activity and Facilitates Platelet Outside-in αIIbß3 Integrin Signaling.

The transduction of signals generated by protein kinases and phosphatases are critical for the ability of integrin αIIbß3 to support stable platelet adhesion and thrombus formation. Unlike kinases, it remains unclear how serine/threonine phosphatases engage the signaling networks that are initiated following integrin ligation. Because protein-protein interactions form the backbone of signal transduction, we searched for proteins that interact with the catalytic subunit of protein phosphatase 2A (PP2Ac). In a yeast two-hybrid study, we identified a novel interaction between PP2Ac and an adaptor protein CIN85 (Cbl-interacting protein of 85 kDa). Truncation and alanine mutagenesis studies revealed that PP2Ac binds to the P3 block ((396)PAIPPKKPRP(405)) of the proline-rich region in CIN85. The interaction of purified PP2Ac with CIN85 suppressed phosphatase activity. Human embryonal kidney 293 αIIbß3 cells overexpressing a CIN85 P3 mutant, which cannot support PP2Ac binding, displayed decreased adhesion to immobilized fibrinogen. Platelets contain the ∼85 kDa CIN85 protein along with the PP2Ac-CIN85 complex. A myristylated cell-permeable peptide derived from residues 395-407 of CIN85 protein (P3 peptide) disrupted the platelet PP2Ac-CIN85 complex and decreased αIIbß3 signaling dependent functions such as platelet spreading on fibrinogen and thrombin-mediated fibrin clot retraction. In a phospho-profiling study P3 peptide treated platelets also displayed decreased phosphorylation of several signaling proteins including Src and GSK3ß. Taken together, these data support a role for the novel PP2Ac-CIN85 complex in supporting integrin-dependent platelet function by dampening the phosphatase activity.

The expression of Longus type 4 pilus of enterotoxigenic Escherichia coli is regulated by LngR and LngS and by H-NS, CpxR and CRP global regulators.

Enterotoxigenic Escherichia coli produces a long type 4 pilus called Longus. The regulatory elements and the environmental signals controlling the expression of Longus-encoding genes are unknown. We identified two genes lngR and lngS in the Longus operon, whose predicted products share homology with transcriptional regulators. Isogenic lngR and lngS mutants were considerably affected in transcription of lngA pilin gene. The expression of lngA, lngR and lngS genes was optimally expressed at 37°C at pH 7.5. The presence of glucose and sodium chloride had a positive effect on Longus expression. The presence of divalent ions, particularly calcium, appears to be an important stimulus for Longus production. In addition, we studied H-NS, CpxR and CRP global regulators, on Longus expression. The response regulator CpxR appears to function as a positive regulator of lng genes as the cpxR mutant showed reduced levels of lngRSA expression. In contrast, H-NS and CRP function as negative regulators since expression of lngA was up-regulated in isogenic hns and crp mutants. H-NS and CRP were required for salt- and glucose-mediated regulation of Longus. Our data suggest the existence of a complex regulatory network controlling Longus expression, involving both local and global regulators in response to different environmental signals.

Free hemoglobin increases von Willebrand factor-mediated platelet adhesion in vitro: implications for circulatory devices.

Intravascular hemolysis occurs in patients on extracorporeal membrane oxygenation. High levels of free acellular adult hemoglobin (free HbA) are associated with clotting in this mechanical device that can result in thrombotic complications. Adsorption of fibrinogen onto the surface of biomaterial correlates with platelet adhesion, which is mediated by von Willebrand factor (VWF). Because free Hb interacts with VWF, we studied the effect of hemoglobin (Hb) on platelet adhesion to fibrin(ogen) under conditions of different hydrodynamic forces. This effect was investigated using purified human HbA and fibrinogen, extracellular matrix, collagen, or purified plasma VWF as surface-coated substrates to examine flow-dependent platelet adhesion. Antibodies and VWF-deficient plasma were also used. Free Hb (≥50 mg/dL) effectively augmented platelet adhesion, and microthrombi formation on fibrin(ogen), extracellular matrix, and collagen at high shear stress. The effect of free Hb was effectively blocked by anti-glycoprotein Ibα (GPIbα) antibodies or depletion of VWF. Unexpectedly, free Hb also promoted firm platelet adhesion and stable microthrombi on VWF. Lastly, we determined that Hb interacts directly with the A1 domain. This study is the first to demonstrate that extracellular Hb directly affects the GPIbα-VWF interaction in thrombosis, and describes another mechanism by which hemolysis is connected to thrombotic events.

The sigma factor SigD of Mycobacterium tuberculosis putatively enhances gene expression of the septum site determining protein under stressful environments.

This work examined the expression of the septum site determining gene (ssd) of Mycobacterium tuberculosis CDC1551 and its ∆sigD mutant under different growing conditions. The results showed an up-regulation of ssd during stationary phase and starvation conditions, but not during in vitro dormancy, suggesting a putative role for SigD in the control of ssd expression mainly under lack-of-nutrients environments. Furthermore, we elucidated a putative link between ssd expression and cell elongation of bacilli at stationary phase. In addition, a -35 sigD consensus sequence was found for the ssd promoter region, reinforcing the putative regulation of ssd by SigD, and in turn, supporting this protein role during the adaptation of M. tuberculosis to some stressful environments.

Assessing the Congregate Disaster Shelter: Using Shelter Facility Assessment Data for Evaluating Potential Hazards to Occupants During Disasters.

Disaster shelter assessments are environmental health assessments conducted during disaster situations to evaluate the living environment of shelters for hygiene, sanitation, and safety conditions. We conducted a secondary data analysis of shelter assessment records available (n = 108) on ice storms, floods, and tornado events from 1 state jurisdiction. Descriptive statistics were used to analyze results of environmental health deficiencies found in the facilities. The greater numbers of environmental health deficiencies were associated with sanitation (26%), facility physical issues (19%), and food areas (17%). Most deficiencies were reported following ice storms, tornadoes, and flood events. This report describes the first analysis of environmental health deficiencies found in disaster shelters across a spectrum of disaster events. Although the number of records analyzed for this project was small and results may not be generalizable, this new insight into the living environment in shelter facilities offers the first analysis of deficiencies of the shelter operation and living environment that have great potential to affect the safety and health of shelter occupants.

Platelet adhesion involves a novel interaction between vimentin and von Willebrand factor under high shear stress.

The interaction between platelet receptor glycoprotein Ibα and the A1 domain of von Willebrand factor (VWF) mediates tethering/translocation of platelets to sites of vascular injury. Unexpectedly, we observed platelets translocating over A1A2A3 domains protein slower than on A1 domain at high shear stress. This observation suggests an additional interaction between A domains and an adhesive receptor. We investigated vimentin because we have data showing the interaction of vimentin with the A2 domain of VWF. Moreover, vimentin is expressed on the platelet surface. This novel interaction was analyzed by using purified VWF, recombinant proteins, anti-vimentin antibodies, parallel flow chamber adhesion assays, flow cytometry, and vimentin-deficient murine platelets. The active form of VWF bound to vimentin, and the purified A2 domain blocked that binding. The interaction of a gain-of-function A1A2A3 mutant with platelet was reduced using anti-vimentin antibody. Platelet adhesion to wild-type (WT) A1A2A3 protein, collagen, and fibrin(ogen) was inhibited (32-75%) by anti-vimentin antibody under high shear stress. Compared with WT mice, platelets from vimentin-deficient mice had a reduced flow-dependent adhesion to both collagen and purified murine VWF. Last, the vimentin knockout mice had a prolonged tail bleeding time. The results describe that platelet vimentin engages VWF during platelet adhesion under high shear stress.

A toxin-antitoxin module of Salmonella promotes virulence in mice.

Toxin-antitoxin (TA) modules are widely prevalent in both bacteria and archaea. Originally described as stabilizing elements of plasmids, TA modules are also widespread on bacterial chromosomes. These modules promote bacterial persistence in response to specific environmental stresses. So far, the possibility that TA modules could be involved in bacterial virulence has been largely neglected, but recent comparative genomic studies have shown that the presence of TA modules is significantly associated with the pathogenicity of bacteria. Using Salmonella as a model, we investigated whether TA modules help bacteria to overcome the stress conditions encountered during colonization, thereby supporting virulence in the host. By bioinformatics analyses, we found that the genome of the pathogenic bacterium Salmonella Typhimurium encodes at least 11 type II TA modules. Several of these are conserved in other pathogenic strains but absent from non-pathogenic species indicating that certain TA modules might play a role in Salmonella pathogenicity. We show that one TA module, hereafter referred to as sehAB, plays a transient role in virulence in perorally inoculated mice. The use of a transcriptional reporter demonstrated that bacteria in which sehAB is strongly activated are predominantly localized in the mesenteric lymph nodes. In addition, sehAB was shown to be important for the survival of Salmonella in these peripheral lymphoid organs. These data indicate that the transient activation of a type II TA module can bring a selective advantage favouring virulence and demonstrate that TA modules are engaged in Salmonella pathogenesis.