Biological sex influences susceptibility to Acinetobacter baumannii pneumonia in mice

Acinetobacter baumannii (A. baumannii) is an extremely versatile multidrug-resistant pathogen with a very high mortality rate; therefore, it has become crucial to understand the host response during its infection. Given the importance of mice for modeling infection and their role in preclinical drug development, equal emphasis should be placed on the use of both sexes. Through our studies using a murine model of acute pneumonia with A. baumannii, we observed that female mice were more susceptible to infection. Likewise, treatment of male mice with estradiol increased their susceptibility to infection. Analysis of the airway compartment revealed enhanced inflammation and reduced neutrophil and alveolar macrophage numbers compared with male mice. Depletion of either neutrophils or alveolar macrophages was important for bacterial clearance; however, depletion of alveolar macrophages further exacerbated female susceptibility because of severe alterations in metabolic homeostasis. Our data highlight the importance of using both sexes when assessing host immune pathways

Budd-Chiari syndrome recurring in a transplanted liver

A patient with Budd-Chiari syndrome who underwent orthotopic liver transplantation and developed recurrent disease is described. The immediate postoperative period was complicated by multiple thrombotic episodes, followed by a period of apparent remission associated with the initiation of coumadin and persantine therapy. After discontinuation of such antithrombotic therapy in order to biopsy the liver, the patient experienced another series of clinically overt vascular thromboses and ultimately died of sepsis 15 mo posttransplantation after a prolonged and complicated terminal hospital course. At autopsy, recurrent Budd-Chiari syndrome as well as thromboses in numerous other organs was demonstrated. © 1983

Induction of Type I Interferon Signaling Determines the Relative Pathogenicity of Staphylococcus aureus Strains

The tremendous success of S. aureus as a human pathogen has been explained primarily by its array of virulence factors that enable the organism to evade host immunity. Perhaps equally important, but less well understood, is the importance of the intensity of the host response in determining the extent of pathology induced by S. aureus infection, particularly in the pathogenesis of pneumonia. We compared the pathogenesis of infection caused by two phylogenetically and epidemiologically distinct strains of S. aureus whose behavior in humans has been well characterized. Induction of the type I IFN cascade by strain 502A, due to a NOD2-IRF5 pathway, was the major factor in causing severe pneumonia and death in a murine model of pneumonia and was associated with autolysis and release of peptidogylcan. In contrast to USA300, 502A was readily eliminated from epithelial surfaces in vitro. Nonetheless, 502A caused significantly increased tissue damage due to the organisms that were able to invade systemically and trigger type I IFN responses, and this was ameliorated in Ifnar-/- mice. The success of USA300 to cause invasive infection appears to depend upon its resistance to eradication from epithelial surfaces, but not production of specific toxins. Our studies illustrate the important and highly variable role of type I IFN signaling within a species and suggest that targeted immunomodulation of specific innate immune signaling cascades may be useful to prevent the excessive morbidity associated with S. aureus pneumonia

Simplified Multistep Outflow Method to Estimate Unsaturated Hydraulic Functions for Coarse-Textured Soils

Although the multistep outfl ow (MSO) method is well suited for the estimation of soil hydraulic properties by inverse solution techniques, this method has not been widely adopted because it requires advanced instrumentation and is time consuming. Th e objective of this study was to develop a modifi ed version of the multistep outfl ow technique that largely simplifi es laboratory procedures and reduces costs and time. Th e numerical inversion procedures require applying user-friendly HYDRUS soft ware to estimate fi tting parameters for soil water retention and unsaturated hydraulic conductivity curves. Whereas values of saturated water content and saturated hydraulic conductivity must be measured independently, the remaining functional parameters are estimated using an inverse solution of a transient drainage experiment using multiple suction steps and a hanging water column, with drainage outfl ows measured during drainage. A comparison test showed that the simplifi ed experiment without tensiometric measurements provided suffi cient information in the parameter identifi cation compared with a traditional pressure outfl ow experiment with tensiometric measurements for an Oso Flaco sand and a loamy sand fi eld soil in the suction range of 0 to 17 kPa

Measurement and simulation of one-dimensional transient three phase flow for monotonic liquid drainage

Simultaneous movement of oil, water, and air in a sandy porous medium was investigated experimentally under transient flow conditions and results were compared to numerical simulations employing a finite element multiphase flow code. The liquid hydrocarbon was Soltrol 170, a low-density branched alkane mixture. Liquid saturations were measured using a collinear dual-energy gamma radiation apparatus and liquid pressures were measured using hydrophilic (untreated) and hydrophobic (treated) ceramic tensiometers connected to pressure transducers. The experimental regime was selected to impose monotonically draining water and total liquid saturation paths to avoid hysteretic effects. Measured saturations and pressures are compared to values obtained from numerical simulations of the experiment using a finite element solution of the governing multiphase flow equations assuming negligible gas pressure gradients. Functional relationships between permeabilitiesk, saturations S, and capillary pressures P employed in the numerical model were estimated by two calibration methods which require different degrees of experimental effort. Measured transient water saturation versus oil-water capillary head data agreed well with predictions from static air-water S-P relations and interfacial tension data. Transient total liquid saturation versus air-oil capillary head data deviated more severely from the scaled air-water S-P data, possibly reflecting noncompliance with the assumption of negligible gas pressure gradients. Reasonably good agreement was observed between measured and numerically simulated water and oil saturations and pressures in space and time. Sensitivity of the numerical results to calibration method was not great

An engineered protein antagonist of K-Ras/B-Raf interaction

Ras is at the hub of signal transduction pathways controlling cell proliferation and survival. Its mutants, present in about 30% of human cancers, are major drivers of oncogenesis and render tumors unresponsive to standard therapies. Here we report the engineering of a protein scaffold for preferential binding to K-Ras G12D. This is the first reported inhibitor to achieve nanomolar affinity while exhibiting specificity for mutant over wild type (WT) K-Ras. Crystal structures of the protein R11.1.6 in complex with K-Ras WT and K-Ras G12D offer insight into the structural basis for specificity, highlighting differences in the switch I conformation as the major defining element in the higher affinity interaction. R11.1.6 directly blocks interaction with Raf and reduces signaling through the Raf/MEK/ERK pathway. Our results support greater consideration of the state of switch I and provide a novel tool to study Ras biology. Most importantly, this work makes an unprecedented contribution to Ras research in inhibitor development strategy by revealing details of a targetable binding surface. Unlike the polar interfaces found for Ras/effector interactions, the K-Ras/R11.1.6 complex reveals an extensive hydrophobic interface that can serve as a template to advance the development of high affinity, non-covalent inhibitors of K-Ras oncogenic mutants.National Institutes of Health (U.S.) (Grant 5-R01-CA096504-15

NetB, a New Toxin That Is Associated with Avian Necrotic Enteritis Caused by Clostridium perfringens

For over 30 years a phospholipase C enzyme called alpha-toxin was thought to be the key virulence factor in necrotic enteritis caused by Clostridium perfringens. However, using a gene knockout mutant we have recently shown that alpha-toxin is not essential for pathogenesis. We have now discovered a key virulence determinant. A novel toxin (NetB) was identified in a C. perfringens strain isolated from a chicken suffering from necrotic enteritis (NE). The toxin displayed limited amino acid sequence similarity to several pore forming toxins including beta-toxin from C. perfringens (38% identity) and alpha-toxin from Staphylococcus aureus (31% identity). NetB was only identified in C. perfringens type A strains isolated from chickens suffering NE. Both purified native NetB and recombinant NetB displayed cytotoxic activity against the chicken leghorn male hepatoma cell line LMH; inducing cell rounding and lysis. To determine the role of NetB in NE a netB mutant of a virulent C. perfringens chicken isolate was constructed by homologous recombination, and its virulence assessed in a chicken disease model. The netB mutant was unable to cause disease whereas the wild-type parent strain and the netB mutant complemented with a wild-type netB gene caused significant levels of NE. These data show unequivocally that in this isolate a functional NetB toxin is critical for the ability of C. perfringens to cause NE in chickens. This novel toxin is the first definitive virulence factor to be identified in avian C. perfringens strains capable of causing NE. Furthermore, the netB mutant is the first rationally attenuated strain obtained in an NE-causing isolate of C. perfringens; as such it has considerable vaccine potential

Isolation of the Bacteriophage DinoHI from Dichelobacter nodosus and its Interactions with other Integrated Genetic Elements

The Gram-negative anaerobic pathogen Dichelobacter nodosus carries several genetic elements that integrate into the chromosome. These include the intA, intB, intC and intD elements, which integrate adjacent to csrA and pnpA, two putative global regulators of virulence and the virulence-related locus, vrl, which integrates into ssrA. Treatment of D. nodosus strains with ultraviolet light resulted in the isolation of DinoHI, a member of the Siphoviridae and the first bacteriophage to be identified in D. nodosus. Part of the DinoHI genome containing the packaging site is found in all D. nodosus strains tested and is located at the end of the vrl, suggesting a role for DinoHI in the transfer of the vrl by transduction. Like the intB element, the DinoHI genome contains a copy of regA which has similarity to the repressors of lambdoid bacteriophages, suggesting that the maintenance of DinoHI and the intB element may be co-ordinately controlled

Stable Patterns of Gene Expression Regulating Carbohydrate Metabolism Determined by Geographic Ancestry

Background: Individuals of African descent in the United States suffer disproportionately from diseases with a metabolic etiology (obesity, metabolic syndrome, and diabetes), and from the pathological consequences of these disorders (hypertension and cardiovascular disease). Methodology/Principal Findings: Using a combination of genetic/genomic and bioinformatics approaches, we identified a large number of genes that were both differentially expressed between American subjects self-identified to be of either African or European ancestry and that also contained single nucleotide polymorphisms that distinguish distantly related ancestral populations. Several of these genes control the metabolism of simple carbohydrates and are direct targets for the SREBP1, a metabolic transcription factor also differentially expressed between our study populations. Conclusions/Significance: These data support the concept of stable patterns of gene transcription unique to a geographic ancestral lineage. Differences in expression of several carbohydrate metabolism genes suggest both genetic and transcriptional mechanisms contribute to these patterns and may play a role in exacerbating the disproportionate levels o