Showing papers in "Virulence in 2010"
TL;DR: Clinical studies on the treatment of infectious diseases have been performed with artificial peptides derived from human lactoferrin, histatins and BPI in addition to porcine protegrins, frog magains and bovine indolicidin, showing increasing evidence that AMPs play a crucial role in human immunity.
Abstract: The production of peptides and small proteins with microbicidal activity collectively called antimicrobial peptides (AMPs) is commonly considered to be a primitive mechanism of immunity and has been extensively studied in insects and other non-vertebrate organisms. In addition, a variety of AMPs present in amphibian skin secretion has been well characterised. There is now increasing evidence that AMPs play a crucial role in human immunity as well. Virtually all human tissues and cells typically exposed to microbes are able to produce AMPs. Important AMPs belonging to two structurally distinct classes, known as the defensins and the cathelicidins, are mainly produced by epithelial cells and neutrophils. AMPs significantly contributing to the chemical skin barrier are represented by dermcidin, psoriasin and RNase 7. The antimicrobial activity of saliva largely depends on histidine-rich AMPs known as histatins. Many more, in part less well-known AMPs and AMP-like proteins exist that exhibit various additional functions, apart from their antimicrobial properties. Among them, the neutrophil granule proteins azurocidin and cathepsin G are members of a family of serine-protease homologues called serprocidins and play a role in the regulation of the immune response and degradation of extracellular matrix proteins respectively. As another AMP-like protein of the neutrophil granule content, bactericidal/permeability increasing protein (BPI) is both able to permeabilise bacterial membranes and to function as an opsonin. The whey acidic protein (WAP) domain containing class of AMPs, including secretory leukocyte protease inhibitor (SLPI), elafin and trappin-2, is equally important in inhibition of neutrophil serine proteases and killing of microbes. Certain CC or CXC chemokines are known to possess antimicrobial properties and therefore are called kinocidins. Several kinocidins, including thrombocidin-1 and -2, are contained in the α-granules of platelets. A cytoplasmic AMP described as ubiquicidin turned out to be identical with the strongly basic ribosomal protein S30. Proteolytic cleavage of the histone protein H2A in the stomach gives rise to an AMP initially described as buforin I. Adrenomedullin is a hormone-like AMP exhibiting vasodilatory and hypotensive effects. Lysozyme is mainly known for its cell wall degrading activity, but is also capable of non-enzymatic killing of bacteria. An iron-binding protein present in milk and other secretions named lactoferrin was shown to possess antimicrobial and antiviral activity and has been implicated in protection against cancer. Clinical studies on the treatment of infectious diseases have been performed with artificial peptides derived from human lactoferrin, histatins and BPI in addition to porcine protegrins, frog magains and bovine indolicidin. Omiganan, representing an indolicidin derivative, has been demonstrated to be effective in the treatment of acne and catheter-related local infections and is currently considered to be the most promising AMP-based drug candidate.
612 citations
TL;DR: The results indicate that PCR from DNA of unstimulated peripheral blood mononuclear cells is the least sensitive method for detection of XMRV in subjects' blood.
Abstract: In October 2009, we reported the first direct isolation of infectious xenotropic murine leukemia virus-related virus (XMRV). In that study, we used a combination of biological amplification and molecular enhancement techniques to detect XMRV in more than 75% of 101 patients with chronic fatigue syndrome (CFS). Since our report, controversy arose after the publication of several studies that failed to detect XMRV infection in their CFS patient populations. In this addenda, we further detail the multiple detection methods we used in order to observe XMRV infection in our CFS cohort. Our results indicate that PCR from DNA of unstimulated peripheral blood mononuclear cells is the least sensitive method for detection of XMRV in subjects' blood. We advocate the use of more than one type of assay in order to determine the frequency of XMRV infection in patient cohorts in future studies of the relevance of XMRV to human disease.
415 citations
TL;DR: Methods to study fungal virulence, filamentation and fungal cell associates with insect hemocytes using Candida albicans and Cryptococcus neoformans to illustrate the use of G. mellonella as an infection model are presented.
Abstract: The facile inoculum delivery and handling of the insect Galleria mellonella make it a desirable model for the study of fungal pathogenesis. Here we present methods to study fungal virulence, filamentation and fungal cell associates with insect hemocytes using Candida albicans and Cryptococcus neoformans to illustrate the use of this model. The two types of fungi cause distinct infections thus we compare and contrast the infection characteristics observed in G. mellonella. The protocols presented herein can be adapted to the study of other fungal pathogens using G. mellonella as an infection model.
274 citations
TL;DR: It is demonstrated that the functional repertoire of resistance genes in the human microbiome is much more diverse than suggested using previous culture-dependent methods, and shows that many resistance genes from cultured proteobacteria from human fecal samples are identical to resistance genes harbored by human pathogens.
Abstract: The increasing levels of multi-drug resistance in human pathogenic bacteria are compromising our ability to treat infectious disease. Since antibiotic resistance determinants are readily exchanged between bacteria through lateral gene transfer, there is an increasing interest in investigating reservoirs of antibiotic resistance accessible to pathogens. Due to the high likelihood of contact and genetic exchange with pathogens during disease progression, the human microflora warrants special attention as perhaps the most accessible reservoir of resistance genes. Indeed, numerous previous studies have demonstrated substantial antibiotic resistance in cultured isolates from the human microflora. By applying metagenomic functional selections, we recently demonstrated that the functional repertoire of resistance genes in the human microbiome is much more diverse than suggested using previous culture-dependent methods. We showed that many resistance genes from cultured proteobacteria from human fecal samples are identical to resistance genes harbored by human pathogens, providing strong support for recent genetic exchange of this resistance machinery. In contrast, most of the resistance genes we identified with culture independent metagenomic sampling from the same samples were novel when compared to all known genes in public databases. While this clearly demonstrates that the antibiotic resistance reservoir of the large fraction of the human microbiome recalcitrant to culturing is severely under sampled, it may
183 citations
TL;DR: It is demonstrated that Th17-IL-23 pathway may play a crucial role in protective immunity against other intracellular pathogens by regulating the innate and adaptive immune responses.
Abstract: The identification of a new T cell subset referred to as T helper 17 (Th17) cells and its role in protective immunity against extracellular bacterial infections is well established. In contrast, initial studies suggested that the IL-23-IL-17 pathway was not required for protection against intracellular pathogens such as mycobacterial infections. However, recent studies demonstrate that Th17-IL-23 pathway may play a crucial role in protective immunity against other intracellular pathogens by regulating the innate and adaptive immune responses. The current outlook on the role of IL-23-IL-17 pathway in protective immunity to intracellular pathogens is discussed here.
170 citations
TL;DR: The syndemics model is presented as a biosocial approach for examining the nature, pathways, contexts, and health implications of PPI and the utility of this approach to PPI is suggested.
Abstract: There is growing awareness of the health implications of fact that infectious agents often do not act independently; rather their disease potential is mediated in diverse and significant ways by their relationships with other pathogens. Pathogen-pathogen interaction (PPI), for example, impacts various virulence factors in human infection. Although still in its infancy, the study of PPI, a form of epidemiological synergism, is emerging as an important arena of new research and new understanding in health and clinical care. The aims of this paper are to: 1) draw attention to the role of PPI in human disease patterns; 2) present the syndemics model as a biosocial approach for examining the nature, pathways, contexts, and health implications of PPI; and 3) suggest the utility of this approach to PPI. Toward these ends, this paper (a) reviews three of case examples of alternative PPIs, (b) describes the development and key concepts and components of the syndemics model with specific reference to interacting infectious agents, (c) contextualizes this discussion with a brief review of broader syndemics disease processes (not necessarily involving infections disease), and (d) comments on the research, treatment and prevention implications of syndemic interaction among pathogens.
114 citations
TL;DR: It is demonstrated that the nitric oxide -releasing nanoparticle (NO-np) are an easily administered topical antimicrobial for the treatment of Ab wound infections, and the findings suggest that NO-nps may also be ideal for use in combat or disaster situations.
Abstract: Acinetobacter baumannii (Ab) is a frequent cause of hospital acquired pneumonia and recently has increased in incidence as the causative agent of severe disease in troops wounded in Afghanistan and Iraq. Ab clinical isolates are frequently extremely resistant to antimicrobials, significantly complicating our capacity to treat infections due to this pathogen. Hence, the development of innovative therapeutics targeting mechanisms to which the bacteria are unlikely to evolve resistance is urgently needed. We examined the capacity of a nitric oxide-releasing nanoparticle (NO-np) to treat wounds infected with Ab. We found that the NO-nps were therapeutic in an experimental Ab murine wound model. Treatment with NO-nps significantly accelerated healing of infected wounds. Histological study demonstrated that NO-np treatment reduced suppurative inflammation, decreased microbial burden, and reduced the degradation of collagen. Furthermore, NO-np treatment alters the local cytokine milieu. In sum, we demonstrated that the NO-nps are an easily administered topical antimicrobial for the treatment of Ab wound infections, and our findings suggest that NO-nps may also be ideal for use in combat or disaster situations.
105 citations
TL;DR: It is shown that the ebpABCfm locus encodes pili on the E. faecium TX82 cell surface and provide the first evidence that pili of this emerging pathogen are important for its ability to form biofilm and to cause infection in an ascending UTI model.
Abstract: We recently identified 15 genes encoding putative surface proteins with features of MSCRAMMs and/or pili in the Enterococcus faecium TX0016 (DO) genome, including four predicted pilus-encoding gene clusters; we also demonstrated that one of these, ebpABCfm, is transcribed as an operon, that its putative major pilus subunit, EbpCfm (also called pilB), is polymerized into high molecular weight complexes, and that it is enriched among clinical E. faecium isolates. Here, we created a deletion of the ebpABCfm operon in an endocarditis-derived E. faecium strain (TX82) and showed, by a combination of whole-cell ELISA, flow cytometry, immunoblot and immunogold electron microscopy, that this deletion abolished EbpCfm expression and eliminated EbpCfm-containing pili from the cell surface. However, transcription of the downstream sortase, bpsfm, was not affected. Importantly, the ebpABCfm deletion resulted in significantly reduced biofilm formation (p < 0.0001) and initial adherence (p < 0.0001) versus the wil...
92 citations
TL;DR: Focused on how the proteins constituting the secretion system interact, a sub-complex of the T6SS was identified comprised of four cell envelope proteins: the inner membrane-anchored TssL, TssM and TagL proteins and the outer membrane-associated TssJ lipoprotein, and it was demonstrated that the TagL subunit carries a specific domain allowing anchorage of the secretionSystem to the peptidoglycan (PG) layer.
Abstract: The recently identified bacterial type VI secretion system (T6SS) has rapidly become one of the most interesting areas of research in microbiology. In a relatively short period of time the relationship between the T6SS and the bacteriophage T4 tail and baseplate has been established. However, a number of questions concerning the T6SS remain the focus of a large number of researchers worldwide. Key questions that need to be addressed include how this system assembles in the cell envelope and the mechanism by which it translocates effector proteins across two membranes, the identification of such effectors and their function, how this secretion system contributes to virulence, interbacterial interactions and/or adaptation to the environment, and the evolutionary relationship between T6SS machine and bacteriophage T4. Focused on how the proteins constituting the secretion system interact, we recently identified a sub-complex of the T6SS comprised of four cell envelope proteins: the inner membrane-anchored TssL, TssM and TagL proteins and the outer membrane-associated TssJ lipoprotein. We further demonstrated that the TagL subunit carries a specific domain allowing anchorage of the secretion system to the peptidoglycan (PG) layer. Herein, we discuss these results, examine whether PG-binding motifs are found within other T6SS subunits and express hypotheses regarding the role of PG-binding motifs in type VI secretion.
77 citations
TL;DR: The epidemiology and economic impact of Candida and the potential risk factors for Candida infection in this population of critically ill trauma patients are examined to identify independent risk Factors for candidiasis.
Abstract: Background: Data on Candida infection among critically ill trauma patients are limited and not recently updated. Here we study the epidemiology and economic impact of Candida and examine potential risk factors for Candida infection in this population. Methods: In this 5-year retrospective study, all severely injured patients with ³4 days of intensive care unit stay were included, with the primary outcome being Candida infection. We identified 3 distinct patient groups: 1) The Candida infection, 2) The Candida colonization and 3) the Candida-free group. All comparisons between groups with p-values ≤0.2 from the univariate analysis were entered into stepwise logistic regression to identify independent risk factors for candidiasis. Results: 374 patients were included. Upon comparisons between groups, candidiasis patients received significantly more blood transfusions (p=0.013), antibiotics (p=0.005), and total parenteral nutrition (TPN) (p=0.004), had a longer duration of mechanical ventilation (MV) (p=0.008...
74 citations
TL;DR: The predicted DNA specificities of TAL effectors were predicted and artificial TAL proteins with novel DNA recognition specificities were generated, enabling design of proteins with potentially any given DNA recognition specificity enabling many uses for biotechnology.
Abstract: TAL effectors are important virulence factors of bacterial plant pathogenic Xanthomonas, which infect a wide variety of plants including valuable crops like pepper, rice, and citrus. TAL proteins are translocated via the bacterial type III secretion system into host cells and induce transcription of plant genes by binding to target gene promoters. Members of the TAL effector family differ mainly in their central domain of tandemly arranged repeats of typically 34 amino acids each with hypervariable di-amino acids at positions 12 and 13. We recently showed that target DNA-recognition specificity of TAL effectors is encoded in a modular and clearly predictable mode. The repeats of TAL effectors feature a surprising one repeat-to-one-bp correlation with different repeat types exhibiting a different DNA base pair specificity. Accordingly, we predicted DNA specificities of TAL effectors and generated artificial TAL proteins with novel DNA recognition specificities. We describe here novel artificial TALs and di...
TL;DR: This paper focuses on coevolution between microbial proteinases operating as virulence factors and host defense molecules of insects, resulting in sophisticated molecular adaptations of host insects such as sensing and feedback-loop regulation of microbial metalloproteinases and corresponding countermeasures of pathogens providing evasion of host immunity induced by these virulent factors.
Abstract: Virulence is thought to coevolve as a result of reciprocal selection between pathogens and their hosts. This paper focuses on coevolution between microbial proteinases operating as virulence factors and host defense molecules of insects. Owing to shorter generation times and smaller genomes, microbes exhibit a high evolutionary adaptability in comparison with their hosts. Indeed, the latter can only compete with pathogens if they evolve mechanisms providing a comparable genetic plasticity. Gene or domain duplication and shuffling by recombination is the driving force behind the countermeasures in host defense effectors. Recent literature provides evidence for both diversifications of fungal proteinases involved in pathogenesis and expansion host proteinase inhibitors subsets contributing to insect innate immunity. For example, the pathogen-associated spectrum of proteolytic enzymes encompasses thermolysin-like metalloproteinases that putatively promoted the evolution of corresponding host inhibitors of these virulence factors which complement the insect repertoire of antimicrobial defense molecules. Beyond mutual diversification of effector molecules coevolution resulted also in sophisticated molecular adaptations of host insects such as sensing and feedback-loop regulation of microbial metalloproteinases and corresponding countermeasures of pathogens providing evasion of host immunity induced by these virulence factors.
TL;DR: The ability of IFNαβ to down regulate IFNGR provides an explanation for its ability to reduce responsiveness to IFNγ and to increase host susceptibility to bacterial infection.
Abstract: Type I and II interferons (IFNs αβ and γ) have opposing effects on immune resistance to certain pathogenic bacteria. While IFNγ generally plays a protective role, IFNαβ exacerbates Listeria monocytogenes and Mycobacterium tuberculosis infections. Our findings provided evidence that this increased susceptibility reflects a novel antagonistic cross talk between IFNαβ and IFNγ. Macrophages infected with L. monocytogenes strains that induce IFNαβ production responded poorly to IFNγ, as measured by reduced phosphorylation of STAT1 and reduced IFNγ-dependent gene expression. The impaired responsiveness to IFNγ correlated with reduced expression of its receptor, IFNGR, by both infected and bystander macrophages. Down regulation of IFNGR was dependent on responsiveness to IFNγ and mimicked by recombinant IFNβ. Mice lacking responsiveness to IFNαβ (IFNAR1 (-/-)) retained high IFNGR expression, developed higher expression of MHC-II on macrophages and DCs, and were more resistant to systemic L. monocytogenes infection--but only in the presence of IFNγ. Thus, the ability of IFNαβ to down regulate IFNGR provides an explanation for its ability to reduce responsiveness to IFNγ and to increase host susceptibility to bacterial infection. It remains to be determined whether and how such antagonistic interferon crosstalk benefits the host.
TL;DR: Candidainfection is alarmingly high among NTES patients with prolonged intensive care unit (ICU) stay and surgical complications and bacterial infections were significantly correlated with the development of candidiasis.
Abstract: Background: Candida is a significant pathogen among critically ill patients. However, candidiasis among non-trauma emergency surgery (NTES) patients has not been previously investigated. Herein we describe the incidence of both colonization and infection from Candida and risk factors for invasive disease in this population. Methods: For this retrospective single center study we included all NTES patients with ICU stay ≥4 days from May 1st, 2002 to April 30th, 2007. Patients were divided into 3 non-overlapping groups: 1) patients with Candida-infection, 2) patients with Candida colonization and 3) patients with negative Candida cultures. Groups were compared by univariate and multivariate analyses to identify significant risk factors for invasive candidiasis. Results: Of all 289 eligible patients, 63 (21.7%) fulfilled the criteria for Candida infection and 110 (38%) were included in the Candida colonization group. Interestingly, from the 63 patients with invasive candidiasis, 25 (39.7%) were infected by a ...
TL;DR: Structural work revealed that distinct regions within EBOV VP35 IID contribute to virulence through host immune evasion and viral RNA synthesis, suggesting the potential of multifunctional Ebola VP35 as a therapeutic target.
Abstract: Ebola virus (EBOV) is a member of the filoviridae family that causes severe hemorrhagic fever during sporadic outbreaks, and no approved treatments are currently available The multifunctional EBOV VP35 protein facilitates immune evasion by antagonizing antiviral signaling pathways and is important for viral RNA synthesis In order to elucidate regulatory mechanisms and to develop countermeasures, we recently solved the structures of the Zaire and Reston EBOV VP35 interferon inhibitory domain (IID) in the free form and of the Zaire EBOV VP35 IID bound to dsRNA Together with biochemical, cell biological, and virological studies, our structural work revealed that distinct regions within EBOV VP35 IID contribute to virulence through host immune evasion and viral RNA synthesis Here we summarize our recent structural and functional studies and discuss the potential of multifunctional Ebola VP35 as a therapeutic target
TL;DR: The role of the NLRP3 inflammasome has recently been identified as playing an important role in recognition of the fungal pathogen Candida albicans and the findings are reviewed.
Abstract: The relationship between host and opportunistic pathogen is a tenuous one and an injudicious response to pathogen-associated molecular patterns may result in a hostile environment to potentially beneficial commensal organisms. Therefore, discrimination between pathogenic forms, causing cellular damage, and innocuous commensal forms of microbes is critical in maintaining homeostasis. The NLRP3 inflammasome has recently been identified as playing an important role in recognition of the fungal pathogen Candida albicans. Here we will review these findings and discuss the role of the NLRP3 inflammasome in initiating an innate immune response to invasive C. albicans.
TL;DR: Evidence is provided for an expanded role for K capsule in the intracellular and extracellular pathogenesis of UTI, and additional rationale for the development of small molecule inhibitors of capsule biogenesis as anti-virulence therapeutics is provided.
Abstract: The treatment of urinary tract infections (UTIs) is becoming increasingly challenging as uropathogenic Escherichia coli (UPEC) becomes more resistant to the most widely prescribed oral antibiotics. The treatment of UTIs may also be complicated by the inherent lifestyle of UPEC in the urinary tract, revealed in recent studies demonstrating bacterial invasion into bladder epithelial cells, the formation of intracellular bacterial communities (IBCs; biofilm-like colonies in the host cell cytosol), and chronic intracellular persistence with subversion of normal immune surveillance. Identifying key targets in the pathogenesis of UTIs, including IBC formation, will be crucial to replenish the arsenal of treatments for UTIs. Focused on elucidating bacterial components that underpin the development of IBCs, Anderson et al. recently demonstrated a novel role for the K capsule polysaccharide in IBC formation. Without K capsule, intracellular UPEC failed to undergo normal IBC formation, the intracellular bacteria failed to preclude neutrophil infiltration, and UPEC did not undergo serial cycles of intracellular proliferation, resulting in attenuation of the infection. This study also demonstrated an interconnection between sialic acid homeostasis and IBC formation, demonstrating a unique role for this amino sugar in biofilm formation. This study provides evidence for an expanded role for K capsule in the intracellular and extracellular pathogenesis of UTI, and provides additional rationale for the development of small molecule inhibitors of capsule biogenesis as anti-virulence therapeutics.
TL;DR: Recent findings that Hsp90 regulates the morphogenetic transition from yeast to filamentous forms required for virulence of the most prevalent fungal pathogen of humans, Candida albicans, and does so via cAMP-PKA signalling are discussed.
Abstract: Hsp90 is environmentally contingent molecular chaperone that influences the form and function of diverse signal transducers. Here we discuss our recent findings that Hsp90 regulates the morphogenetic transition from yeast to filamentous forms required for virulence of the most prevalent fungal pathogen of humans, Candida albicans, and does so via cAMP-PKA signalling. This transition is normally regulated by environmental cues that are contingent upon elevated temperature to relieve Hsp90-mediated repression of the morphogenetic program. Intriguingly, Hsp90 inhibition induces filamentation independent of the canonical PKA transcription factor Efg1, in striking similarity to a select set of morphogenetic stimuli. Further investigation will determine the downstream transcription factors through which Hsp90 regulates morphogenesis and the precise mechanism of Hsp90's interaction with the cAMP-PKA pathway. C. albicans is one of many fungal species that undergo a morphological transition in a temperature-dependent manner, thus Hsp90's capacity to govern this key developmental program may provide insight into morphogenesis of diverse organisms.
TL;DR: The functional link between regulation of V-ATPase by fungal membrane lipid components and the importance of pH homeostasis in virulence highlights its potential as target in antifungal chemotherapy.
Abstract: Many antifungal drugs including the highly successful azoles target the fungal-specific sterol, ergosterol, yet the molecular identity of cellular pathways mediating antifungal activity remained obscure. A recent study on the requirement of ergosterol in vacuolar H+-ATPase (V-ATPase) function uncovered a critical role for ion homeostasis downstream of azole inhibition of ergosterol biosynthesis. Here we review the functional link between regulation of V-ATPase by fungal membrane lipid components and discuss contributions of V-ATPase function to pathogenicity. The importance of pH homeostasis in virulence highlights its potential as target in antifungal chemotherapy.
TL;DR: It is shown here that a pathway involving fatty acid synthesis and the evolutionary conserved wnk‑1 and gck‑3/Ste20/GCK‑VI kinases modulates nlp‑29 expression in the C. elegans epidermis, independently of p38 MAPK signaling.
Abstract: An important part of the innate immune response of the nematode C. elegans to fungal infection is the rapid induction of antimicrobial peptide gene expression. One of these genes, nlp‑29, is expressed at a low level in adults under normal conditions. Its expression is up-regulated in the epidermis by infection with Drechmeria coniospora, but also by physical injury and by osmotic stress. For infection and wounding, the induction is dependent on a p38 MAP kinase cascade, but for osmotic stress, this pathway is not required. To characterize further the pathways that control the expression of nlp‑29, we carried out a genetic screen for negative regulatory genes. We isolated a number of Peni (peptide expression no infection) mutants and cloned one. It corresponds to fasn‑1, the nematode ortholog of vertebrate fatty acid synthase. We show here that a pathway involving fatty acid synthesis and the evolutionary conserved wnk‑1 and gck‑3/Ste20/GCK‑VI kinases modulates nlp‑29 expression in the C. elegans epidermis, independently of p38 MAPK signaling. The control of the antimicrobial peptide gene nlp‑29 thus links different physiological processes, including fatty acid metabolism, osmoregulation, maintenance of epidermal integrity and the innate immune response to infection.
TL;DR: Patients expressing a basal level of CEACAM6 in ileum could be predisposed to develop ileal CD and blocking interaction between type 1 pili and CEACam6 might serve as a specific means of disrupting the colonization and the subsequent inflammatory amplification loop.
Abstract: Abnormal expression of CEACAM6 is observed at the apical surface of the ileal epithelium in Crohn's disease (CD) patients, and CD ileal lesions are colonized by pathogenic adherent-invasive Escherichia coli (AIEC). The paper of Carvalho et al. recently reported that CD associated AIEC colonize and induce strong gut inflammation in transgenic mice expressing human CEACAM6 acting as a receptor for type 1 pili produced by AIEC bacteria. AIEC also induce CEACAM6 expression by intestinal epithelial cells directly by adhering to host cells and indirectly via increased secretion of TNF-α from AIEC-infected macrophages. Patients expressing a basal level of CEACAM6 in ileum could be predisposed to develop ileal CD and blocking interaction between type 1 pili and CEACAM6 might serve as a specific means of disrupting the colonization and the subsequent inflammatory amplification loop.
TL;DR: It is found that Pol II is ubiquitylated in influenza virus infected cells and ubiquitylation can be induced by the expression of the RNA polymerases, and that the viral RNA polymerase plays a critical role in this process.
Abstract: Viruses induce an antiviral host response by activating the expression of antiviral host genes. However, viruses have evolved a wide range of strategies to counteract antiviral host responses. One of the strategies used by many viruses is the general inhibition of host gene expression, also referred to as a host shut-off mechanism. Here we discuss our recent findings that influenza virus infection results in the inhibition and degradation of host RNA polymerase II (Pol II) and that the viral RNA polymerase plays a critical role in this process. In particular, we found that Pol II is ubiquitylated in influenza virus infected cells and ubiquitylation can be induced by the expression of the RNA polymerase. Moreover, the expression of an antiviral host gene could be inhibited by the over-expression of the RNA polymerase. Both ubiquitylation and the inhibition of the host gene were dependent on the ability of the RNA polymerase to bind to Pol II. Further studies will be required to understand the interplay between the host and viral transcriptional machineries and to elucidate the exact molecular mechanisms that lead to the inhibition and degradation of Pol II as a result of viral RNA polymerase binding. These findings extend our understanding of how influenza virus counteracts antiviral host responses and underpin studies into the mechanisms by which the RNA polymerase determines virulence.
TL;DR: In vitro models used to demonstrate the presence of informative carcinogenesis-associated phenotypes in CHO cells exposed to Sh total antigen and showed increased cell proliferation, decreased apoptosis, up regulation of the anti-apoptotic molecule Bcl-2, downregulation of the tumor suppressor protein p27, and increased cell migration and invasion.
Abstract: Schistosoma haematobium is a parasitic flatworm that infects millions of people, mostly in the developing world, and is associated with high incidence of bladder cancer although why is not clear. But our group was able to define the mechanistic relationship for the first time between infection of S. haematobium and cancer. We used in vitro models to demonstrate the presence of informative carcinogenesis-associated phenotypes in CHO cells exposed to Sh total antigen, in which we showed increased cell proliferation, decreased apoptosis, up regulation of the anti-apoptotic molecule Bcl-2, down regulation of the tumor suppressor protein p27, and increased cell migration and invasion. We further discuss the molecular and cellular events that might be responsible for schistosomiasis-related bladder cancer.
TL;DR: It is shown that deletion of exsC from V. parahaemolyticus blocked synthesis of T3SS1-dependent proteins under inducing conditions (contact with HeLa cells), while in trans complementation of the ΔexsC strain with wild-typeExsC restored protein synthesis.
Abstract: Vibrio parahaemolyticus ExsA is the transcriptional regulator for type III secretion system 1 (T3SS1) while ExsD blocks T3SS1 expression. Herein we show that deletion of exsC from V. parahaemolyticus blocked synthesis of T3SS1-dependent proteins under inducing conditions (contact with HeLa cells), while in trans complementation of the ΔexsC strain with wild-type exsC restored protein synthesis. Under non-inducing conditions (Luria broth plus salt), in trans expression of exsC in a wild-type strain resulted in synthesis and secretion of T3SS1-dependent proteins. Deletion of exsC does not affect the synthesis of ExsA while expression of T3SS1 genes is independent of ExsC in the absence of ExsD. Co-expression of recombinant proteins with different antigenic tags demonstrated that ExsC binds ExsD and that the N-terminal amino acids of ExsC (positions 7 to 12) are required for binding. Co-expression and purification of antigentically tagged ExsA and ExsD demonstrated that ExsD directly binds ExsA and presumably prevents ExsA from binding promoter regions of T3SS1 genes. Collectively these data demonstrate that ExsD binds ExsA to block expression of T3SS1 genes, while ExsC binds ExsD to permit expression of T3SS1 genes. ExsA, ExsC, and ExsD from V. parahaemolyticus appear to be functional orthologues of their Pseudomonas aeruginosa counterparts.
TL;DR: A recurrence across pathogenic organisms suggests that this architectural motif was evolutionarily selected because it most effectively ensures the survival of pathogens within the eukaryotic environment.
Abstract: To penetrate host cells through their membranes, pathogens use a variety of molecular components in which the presence of heptad repeat motifs seems to be a prevailing element. Heptad repeats are characterized by a pattern of seven, generally hydrophobic, residues. In order to initiate membrane fusion, viruses use glycoproteins-containing heptad repeats. These proteins are structurally and functionally similar to the SNARE proteins known to be involved in eukaryotic membrane fusion. SNAREs also display a heptad repeat motif called the "SNARE motif". As bacterial genomes are being sequenced, microorganisms also appear to be carrying membrane proteins resembling eukaryotic SNAREs. This category of SNARE-like proteins might share similar functions and could be used by microorganisms to either promote or block membrane fusion. Such a recurrence across pathogenic organisms suggests that this architectural motif was evolutionarily selected because it most effectively ensures the survival of pathogens within the...
TL;DR: It is shown that the physical interaction of RpfG with two proteins with a diguanylate cyclase (GGDEF) domain, acts to control a sub-set of RfG-regulated virulence functions, which were dependent on DSF signaling.
Abstract: In the plant pathogen Xanthomonas campestris pv. campestris (Xcc) a two component system comprising RpfG and the complex sensor kinase RpfC is implicated in sensing and responding to the cell-cell signaling molecule DSF to positively regulate the synthesis of virulence factors such as extracellular enzymes, biofilm structure and motility. RpfG is a two-component regulator with a CheY-like receiver domain attached to an HD-GYP cyclic di-GMP phosphodiesterase domain. In a recent paper we showed that that the physical interaction of RpfG with two proteins with a diguanylate cyclase (GGDEF) domain, acts to control a sub-set of RpfG-regulated virulence functions. These protein-protein interactions required the conserved GYP motif in the HD-GYP domain of RpfG and were dependent on DSF signaling. Here we discuss these findings, considering in particular different scenarios for the role of RpfG in multiple signaling pathways involving cyclic di-GMP that impinge on virulence.
TL;DR: The presence of a putative prophage in the A. asiaticus genome is described, which shows similarity to the antifeeding prophages from the insect pathogen Serratia entomophila, and might represent the missing protein secretion apparatus in the obligate intracellular amoeba host.
Abstract: The recently sequenced genome of the obligate intracellular amoeba symbiont ‘Candidatus Amoebophilus asiaticus' is unique among prokaryotic genomes due to its extremely large fraction of genes encoding proteins harboring eukaryotic domains such as ankyrin-repeats, TPR/SEL1 repeats, leucine-rich repeats, as well as F- and U-box domains, most of which likely serve in the interaction with the amoeba host. Here we provide evidence for the presence of additional proteins which are presumably presented extracellularly and should thus also be important for host cell interaction. Surprisingly, we did not find homologues of any of the well-known protein secretion systems required to translocate effector proteins into the host cell in the A. asiaticus genome, and the type six secretion systems seems to be incomplete. Here we describe the presence of a putative prophage in the A. asiaticus genome, which shows similarity to the antifeeding prophage from the insect pathogen Serratia entomophila. In S. entomophila this...
TL;DR: It is demonstrated that both integrins αvβ6 and αv β8 can serve as specific receptors for gHGL and that on binding to gHgL, even in a soluble form, can provide the trigger for direct virus fusion with the epithelial cell plasma membrane, revealing yet another way in which an integrin can be used by a pathogen to invade a cell.
Abstract: Epstein-Barr virus is a ubiquitous orally-transmitted human herpesvirus that is carried by most of the adult population It establishes latent infections in B lymphocytes, reactivates periodically from latency and can be amplified in epithelial cells where it is thought more commonly to undergo lytic replication Entry into either cell involves fusion of the virus envelope with a cell membrane Fusion with a B cell requires four envelope glycoproteins, gB and a ternary complex of gHgLgp42 Fusion is triggered by an interaction between gp42 and HLA class II Fusion with an epithelial cell requires three envelope glycoproteins, gB and a binary complex of gHgL The presence of gp42 blocks infection and blocks the interaction of gHgL with a specific receptor on the epithelial cell surface We recently demonstrated that both integrins αvβ6 and αvβ8 can serve as specific receptors for gHgL and that on binding to gHgL, even in a soluble form, can provide the trigger for direct virus fusion with the epithelial cell plasma membrane It reveals yet another way in which an integrin can be used by a pathogen to invade a cell
TL;DR: This methodology simplifies biofilm formation under continuous replenishment of nutrients, thereby making it physiologically more relevant than the currently dominant static models.
Abstract: Candida albicans can develop biofilms on medical devices and these biofilms are most often nourished by a continuous flow of body fluids and subjected to shear stress forces. While many C. albicans biofilm studies have been carried out using in vitro static models, more limited information is available for biofilms developed under conditions of flow. We have previously described a simple flow biofilm model (SFB) for the development of C. albicans biofilms under conditions of continuous media flow. Here, we recount in detail from a methodological perspective, this model that can be assembled easily using materials commonly available in most microbiological laboratories.The entire procedure takes approximately two days to complete. Biofilms developed using this system are robust, and particularly suitable for studies requiring large amounts of biofilm cells for downstream analyses. This methodology simplifies biofilm formation under continuous replenishment of nutrients. Moreover, this technique mimics in v...
TL;DR: Using mAb 18F2 and previously generated antibodies to GXM and GalXM, the localization of three capsular components GXM, GalXM and one type of mannoprotein, MP98, is established on the C. neoformans cell.
Abstract: The capsular polysaccharides of Cryptococcus neoformans have historically been divided into three components namely, glucuronoxylomannan (GXM), galactoxylomannan (GalXM), and mannoprotein (MP) but their relative spatial-geographical relationship in the capsule is unknown. To explore this problem would require the capacity for visualizing these components in the capsule. Prior studies have reported serological reagents to GXM and GalXM but no antibodies are available against MPs. Consequently, we immunized Balb/c mice with C. neoformans recombinant mannoprotein 98 and recovered twelve monoclonal antibodies (mAbs) of which one, an IgG2a designated 18F2, bound to intact cells by immunofluorescence. mAb 18F2 bound to the cell wall surface in acapsular and encapsulated cells. Using mAb 18F2 and previously generated antibodies to GXM and GalXM we have established the localization of three capsular components GXM, GalXM and one type of mannoprotein, MP98 on the C. neoformans cell. The results show that MP98...