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Separate jasmonate-dependent and salicylate-dependent defense-response pathways in Arabidopsis are essential for resistance to distinct microbial pathogens

Thomma, Bart P. H. J.; Eggermont, Kristel; Penninckx, Iris A. M. A.; Mauch-Mani, Brigitte; Vogelsang, Ralph; Cammue, Bruno P. A.; Broekaert, Willem F.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 08/12/1998 EN
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The endogenous plant hormones salicylic acid (SA) and jasmonic acid (JA), whose levels increase on pathogen infection, activate separate sets of genes encoding antimicrobial proteins in Arabidopsis thaliana. The pathogen-inducible genes PR-1, PR-2, and PR-5 require SA signaling for activation, whereas the plant defensin gene PDF1.2, along with a PR-3 and PR-4 gene, are induced by pathogens via an SA-independent and JA-dependent pathway. An Arabidopsis mutant, coi1, that is affected in the JA-response pathway shows enhanced susceptibility to infection by the fungal pathogens Alternaria brassicicola and Botrytis cinerea but not to Peronospora parasitica, and vice versa for two Arabidopsis genotypes (npr1 and NahG) with a defect in their SA response. Resistance to P. parasitica was boosted by external application of the SA-mimicking compound 2,6-dichloroisonicotinic acid [Delaney, T., et al. (1994) Science 266, 1247–1250] but not by methyl jasmonate (MeJA), whereas treatment with MeJA but not 2,6-dichloroisonicotinic acid elevated resistance to Alternaria brassicicola. The protective effect of MeJA against A. brassicicola was the result of an endogenous defense response activated in planta and not a direct effect of MeJA on the pathogen...

Modulation of Tumor Necrosis Factor by Microbial Pathogens

Rahman, Masmudur M; McFadden, Grant
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
EN
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481.41367%
In response to invasion by microbial pathogens, host defense mechanisms get activated by both the innate and adaptive arms of the immune responses. TNF (tumor necrosis factor) is a potent proinflammatory cytokine expressed by activated macrophages and lymphocytes that induces diverse cellular responses that can vary from apoptosis to the expression of genes involved in both early inflammatory and acquired immune responses. A wide spectrum of microbes has acquired elegant mechanisms to overcome or deflect the host responses mediated by TNF. For example, modulatory proteins encoded by multiple families of viruses can block TNF and TNF-mediated responses at multiple levels, such as the inhibition of the TNF ligand or its receptors, or by modulating key transduction molecules of the TNF signaling pathway. Bacteria, on the other hand, tend to modify TNF-mediated responses specifically by regulating components of the TNF signaling pathway. Investigation of these diverse strategies employed by viral and bacterial pathogens has significantly advanced our understanding of both host TNF responses and microbial pathogenesis. This review summarizes the diverse microbial strategies to regulate TNF and how such insights into TNF modulation could benefit the treatment of inflammatory or autoimmune diseases.

The role of released ATP in killing Candida albicans and other extracellular microbial pathogens by cationic peptides

Vylkova, Slavena; Sun, Jianing N.; Edgerton, Mira
Fonte: Springer Netherlands Publicador: Springer Netherlands
Tipo: Artigo de Revista Científica
EN
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A unifying theme common to the action of many cationic peptides that display lethal activities against microbial pathogens is their specific action at microbial membranes that results in selective loss of ions and small nucleotides chiefly ATP. One model cationic peptide that induces non-lytic release of ATP from the fungal pathogen Candida albicans is salivary histatin 5 (Hst 5). The major characteristic of Hst 5-induced ATP release is that it occurs rapidly while cells are still metabolically active and have polarized membranes, thus precluding cell lysis as the means of release of ATP. Other cationic peptides that induce selective release of ATP from target microbes are lactoferricin, human neutrophil defensins, bactenecin, and cathelicidin peptides. The role of released extracellular ATP induced by cationic peptides is not known, but localized increases in extracellular ATP concentration may serve to potentiate cell killing, facilitate further peptide uptake, or function as an additional signal to activate the host innate immune system at the site of infection.

Microbial pathogens in ticks, rodents and a shrew in northern Gyeonggi-do near the DMZ, Korea

Chae, Joon-Seok; Yu, Do-Hyeon; Shringi, Smriti; Klein, Terry A.; Kim, Heung-Chul; Chong, Sung-Tae; Lee, In-Yong; Foley, Janet
Fonte: The Korean Society of Veterinary Science Publicador: The Korean Society of Veterinary Science
Tipo: Artigo de Revista Científica
EN
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A total of 1,618 ticks [420 individual (adults) and pooled (larvae and nymphs) samples], 369 rodents (Apodemus agrarius, Rattus norvegicus, Tscherskia triton, Mus musculus, and Myodes regulus), and 34 shrews (Crocidura lasiura) that were collected in northern Gyeonggi-do near the Demilitarized Zone (DMZ) of Korea during 2004-2005, were assayed by PCR for selected zoonotic pathogens. From a total of 420 individual and pooled tick DNA samples, Anaplasma (A.) phagocytophilum (16), A. platys (16), Ehrlichia (E.) chaffeensis (63), Borrelia burgdorferi (16), and Rickettsia spp. (198) were detected using species-specific PCR assays. Out of 403 spleens from rodents and shrews, A. phagocytophilum (20), A. platys (34), E. chaffeensis (127), and Bartonella spp. (24) were detected with species-specific PCR assays. These results suggest that fevers of unknown causes in humans and animals in Korea should be evaluated for infections by these vector-borne microbial pathogens.

Lipoic Acid Metabolism in Microbial Pathogens

Spalding, Maroya D.; Prigge, Sean T.
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
Publicado em /06/2010 EN
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Summary: Lipoic acid [(R)-5-(1,2-dithiolan-3-yl)pentanoic acid] is an enzyme cofactor required for intermediate metabolism in free-living cells. Lipoic acid was discovered nearly 60 years ago and was shown to be covalently attached to proteins in several multicomponent dehydrogenases. Cells can acquire lipoate (the deprotonated charge form of lipoic acid that dominates at physiological pH) through either scavenging or de novo synthesis. Microbial pathogens implement these basic lipoylation strategies with a surprising variety of adaptations which can affect pathogenesis and virulence. Similarly, lipoylated proteins are responsible for effects beyond their classical roles in catalysis. These include roles in oxidative defense, bacterial sporulation, and gene expression. This review surveys the role of lipoate metabolism in bacterial, fungal, and protozoan pathogens and how these organisms have employed this metabolism to adapt to niche environments.

Evolution of eukaryotic microbial pathogens via covert sexual reproduction

Heitman, Joseph
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 22/07/2010 EN
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476.70242%
Sexual reproduction enables eukaryotic organisms to re-assort genetic diversity and purge deleterious mutations, producing better-fit progeny. Sex arose early and pervades eukaryotes. Fungal and parasite pathogens once thought asexual have maintained cryptic sexual cycles, including unisexual or parasexual reproduction. As pathogens become niche and host-adapted, sex appears to specialize to promote inbreeding and clonality yet maintain out-crossing potential. During self-fertile sexual modes, sex itself may generate genetic diversity de novo. Mating-type loci govern fungal sexual identity; how parasites establish sexual identity is unknown. Comparing and contrasting fungal and parasite sex promises to reveal how microbial pathogens evolved and are evolving.

Monocyte-Mediated Defense Against Microbial Pathogens

Serbina, Natalya V.; Jia, Ting; Hohl, Tobias M.; Pamer, Eric G.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
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483.42184%
Circulating blood monocytes supply peripheral tissues with macrophage and dendritic cell (DC) precursors and, in the setting of infection, also contribute directly to immune defense against microbial pathogens. In humans and mice, monocytes are divided into two major subsets that either specifically traffic into inflamed tissues or, in the absence of overt inflammation, constitutively maintain tissue macrophage/DC populations. Inflammatory monocytes respond rapidly to microbial stimuli by secreting cytokines and antimicrobial factors, express the CCR2 chemokine receptor, and traffic to sites of microbial infection in response to monocyte chemoattractant protein (MCP)-1 (CCL2) secretion. In murine models, CCR2-mediated monocyte recruitment is essential for defense against Listeria monocytogenes, Mycobacterium tuberculosis, Toxoplasma gondii, and Cryptococcus neoformans infection, implicating inflammatory monocytes in defense against bacterial, protozoal, and fungal pathogens. Recent studies indicate that inflammatory monocyte recruitment to sites of infection is complex, involving CCR2-mediated emigration of monocytes from the bone marrow into the bloodstream, followed by trafficking into infected tissues. The in vivo mechanisms that promote chemokine secretion...

Influence of Air Quality on the Composition of Microbial Pathogens in Fresh Rainwater

Kaushik, Rajni; Balasubramanian, Rajasekhar; de la Cruz, Armah A.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /04/2012 EN
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476.4246%
In this study, the microbiological quality of fresh rainwater was assessed from 50 rain events under tropical weather conditions for a year. The levels of four major opportunistic waterborne pathogens, namely, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Aeromonas hydrophila, in rainwater samples were quantified by using a robust and sensitive quantitative PCR (qPCR) method. Of the 50 rainwater samples, 25 were found to be positive for at least one pathogen: 21 for E. coli, 16 for P. aeruginosa, 6 for K. pneumoniae, and 1 for A. hydrophila. In addition to the microbiological assessment of rainwater samples, we also studied the influence of prevailing air quality on the microbial quality of rainwater over the sampling period. A significant change in the diversity and relative abundance of the basic microbial indicator organisms in rainwater was observed during a major regional air pollution episode in Southeast Asia due to biomass-burning emissions.

Modulation of NF-κB signalling by microbial pathogens

Rahman, Masmudur M.; McFadden, Grant
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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473.63223%
The nuclear factor-κB (NF-κB) family of transcription factors plays a central part in the host response to infection by microbial pathogens, by orchestrating the innate and acquired host immune responses. The NF-κB proteins are activated by diverse signalling pathways that originate from many different cellular receptors and sensors. Many successful pathogens have acquired sophisticated mechanisms to regulate the NF-κB signalling pathways by deploying subversive proteins or hijacking the host signalling molecules. Here, we describe the mechanisms by which viruses and bacteria micromanage the host NF-κB signalling circuitry to favour the continued survival of the pathogen.

Secretory IgA: Arresting Microbial Pathogens at Epithelial Borders

Mantis, Nicholas J.; Forbes, Stephen J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
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473.46027%
Secretory IgA (SIgA), the predominant class of antibody found in intestinal secretions. While SIgA’s role in protecting the intestinal epithelium from the enteric pathogen and toxins has long been recognized, surprisingly little is known about the molecular mechanisms by which this is achieved. The present review summarizes the current understanding of how SIgA functions to prevent microbial pathogens and toxins from gaining access to the intestinal epithelium. We also discuss recent work from our laboratory examining the interaction of a particular protective monoclonal IgA with Salmonella and propose, based on this work, that SIgA has a previously unrecognized capacity to directly interfere with microbial virulence at mucosal surfaces.

Beneficial and Harmful Interactions of Antibiotics with Microbial Pathogens and the Host Innate Immune System

Anderson, Ronald; Tintinger, Gregory; Cockeran, Riana; Potjo, Moliehi; Feldman, Charles
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 25/05/2010 EN
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In general antibiotics interact cooperatively with host defences, weakening and decreasing the virulence of microbial pathogens, thereby increasing vulnerability to phagocytosis and eradication by the intrinsic antimicrobial systems of the host. Antibiotics, however, also interact with host defences by several other mechanisms, some harmful, others beneficial. Harmful activities include exacerbation of potentially damaging inflammatory responses, a property of cell-wall targeted agents, which promotes the release of pro-inflammatory microbial cytotoxins and cell-wall components. On the other hand, inhibitors of bacterial protein synthesis, especially macrolides, possess beneficial anti-inflammatory/cytoprotective activities, which result from interference with the production of microbial virulence factors/cytotoxins. In addition to these pathogen-directed, anti-inflammatory activities, some classes of antimicrobial agent possess secondary anti-inflammatory properties, unrelated to their conventional antimicrobial activities, which target cells of the innate immune system, particularly neutrophils. This is a relatively uncommon, potentially beneficial property of antibiotics, which has been described for macrolides, imidazole anti-mycotics...

An important role of the pepper phenylalanine ammonia-lyase gene (PAL1) in salicylic acid-dependent signalling of the defence response to microbial pathogens

Kim, Dae Sung; Hwang, Byung Kook
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
EN
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468.64316%
Phenylalanine ammonia-lyase (PAL) is an inducible enzyme that responds to biotic and abiotic stresses. Results suggest the potential significance of pepper PAL1 in the plant defence response to microbial pathogens.

How Often Do They Have Sex? A Comparative Analysis of the Population Structure of Seven Eukaryotic Microbial Pathogens

Tomasini, Nicolás; Lauthier, Juan José; Ayala, Francisco José; Tibayrenc, Michel; Diosque, Patricio
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 23/07/2014 EN
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The model of predominant clonal evolution (PCE) proposed for micropathogens does not state that genetic exchange is totally absent, but rather, that it is too rare to break the prevalent PCE pattern. However, the actual impact of this “residual” genetic exchange should be evaluated. Multilocus Sequence Typing (MLST) is an excellent tool to explore the problem. Here, we compared online available MLST datasets for seven eukaryotic microbial pathogens: Trypanosoma cruzi, the Fusarium solani complex, Aspergillus fumigatus, Blastocystis subtype 3, the Leishmania donovani complex, Candida albicans and Candida glabrata. We first analyzed phylogenetic relationships among genotypes within each dataset. Then, we examined different measures of branch support and incongruence among loci as signs of genetic structure and levels of past recombination. The analyses allow us to identify three types of genetic structure. The first was characterized by trees with well-supported branches and low levels of incongruence suggesting well-structured populations and PCE. This was the case for the T. cruzi and F. solani datasets. The second genetic structure, represented by Blastocystis spp., A. fumigatus and the L. donovani complex datasets, showed trees with weakly-supported branches but low levels of incongruence among loci...

A phylogeny-based sampling strategy and power calculator informs genome-wide associations study design for microbial pathogens

Farhat, Maha R; Shapiro, B Jesse; Sheppard, Samuel K; Colijn, Caroline; Murray, Megan
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em 15/11/2014 EN
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476.70242%
Whole genome sequencing is increasingly used to study phenotypic variation among infectious pathogens and to evaluate their relative transmissibility, virulence, and immunogenicity. To date, relatively little has been published on how and how many pathogen strains should be selected for studies associating phenotype and genotype. There are specific challenges when identifying genetic associations in bacteria which often comprise highly structured populations. Here we consider general methodological questions related to sampling and analysis focusing on clonal to moderately recombining pathogens. We propose that a matched sampling scheme constitutes an efficient study design, and provide a power calculator based on phylogenetic convergence. We demonstrate this approach by applying it to genomic datasets for two microbial pathogens: Mycobacterium tuberculosis and Campylobacter species.

Guidelines for Optimisation of a Multiplex Oligonucleotide Ligation-PCR for Characterisation of Microbial Pathogens in a Microsphere Suspension Array

Wuyts, Véronique; Roosens, Nancy H. C.; Bertrand, Sophie; Marchal, Kathleen; De Keersmaecker, Sigrid C. J.
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
EN
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476.4246%
With multiplex oligonucleotide ligation-PCR (MOL-PCR) different molecular markers can be simultaneously analysed in a single assay and high levels of multiplexing can be achieved in high-throughput format. As such, MOL-PCR is a convenient solution for microbial detection and identification assays where many markers should be analysed, including for routine further characterisation of an identified microbial pathogenic isolate. For an assay aimed at routine use, optimisation in terms of differentiation between positive and negative results and of cost and effort is indispensable. As MOL-PCR includes a multiplex ligation step, followed by a singleplex PCR and analysis with microspheres on a Luminex device, several parameters are accessible for optimisation. Although MOL-PCR performance may be influenced by the markers used in the assay and the targeted bacterial species, evaluation of the method of DNA isolation, the probe concentration, the amount of microspheres, and the concentration of reporter dye is advisable in the development of any MOL-PCR assay. Therefore, we here describe our observations made during the optimisation of a 20-plex MOL-PCR assay for subtyping of Salmonella Typhimurium with the aim to provide a possible workflow as guidance for the development and optimisation of a MOL-PCR assay for the characterisation of other microbial pathogens.

The Response of CD1d-Restricted Invariant NKT Cells to Microbial Pathogens and Their Products

Van Kaer, Luc; Parekh, Vrajesh V.; Wu, Lan
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 13/05/2015 EN
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486.492%
Invariant natural killer T (iNKT) cells become activated during a wide variety of infections. This includes organisms lacking cognate CD1d-binding glycolipid antigens recognized by the semi-invariant T cell receptor of iNKT cells. Additional studies have shown that iNKT cells also become activated in vivo in response to microbial products such as bacterial lipopolysaccharide, a potent inducer of cytokine production in antigen-presenting cells (APCs). Other studies have shown that iNKT cells are highly responsive to stimulation by cytokines such as interleukin-12. These findings have led to the concept that microbial pathogens can activate iNKT cells either directly via glycolipids or indirectly by inducing cytokine production in APCs. iNKT cells activated in this manner produce multiple cytokines that can influence the outcome of infection, usually in favor of the host, although potent iNKT cell activation may contribute to an uncontrolled cytokine storm and sepsis. One aspect of the response of iNKT cells to microbial pathogens is that it is short-lived and followed by an extended time period of unresponsiveness to reactivation. This refractory period may represent a means to avoid chronic activation and cytokine production by iNKT cells...

A phylogeny-based sampling strategy and power calculator informs genome-wide associations study design for microbial pathogens

Farhat, Maha R; Shapiro, B Jesse; Sheppard, Samuel K; Colijn, Caroline; Murray, Megan
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
476.70242%
Whole genome sequencing is increasingly used to study phenotypic variation among infectious pathogens and to evaluate their relative transmissibility, virulence, and immunogenicity. To date, relatively little has been published on how and how many pathogen strains should be selected for studies associating phenotype and genotype. There are specific challenges when identifying genetic associations in bacteria which often comprise highly structured populations. Here we consider general methodological questions related to sampling and analysis focusing on clonal to moderately recombining pathogens. We propose that a matched sampling scheme constitutes an efficient study design, and provide a power calculator based on phylogenetic convergence. We demonstrate this approach by applying it to genomic datasets for two microbial pathogens: Mycobacterium tuberculosis and Campylobacter species. Electronic supplementary material The online version of this article (doi:10.1186/s13073-014-0101-7) contains supplementary material, which is available to authorized users.

Phylogenetic and transcriptional analysis of a strictosidine synthase-like gene family in Arabidopsis thaliana reveals involvement in plant defence responses

Sohani, M.; Schenk, C.; Schultz, C.; Schmidt, O.
Fonte: Georg Thieme Verlag Publicador: Georg Thieme Verlag
Tipo: Artigo de Revista Científica
Publicado em //2009 EN
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473.63223%
Protein domains with similarity to plant strictosidine synthase-like (SSL) sequences have been uncovered in the genomes of all multicellular organisms sequenced so far and are known to play a role in animal immune responses. Among several distinct groups of Arabidopsis thaliana SSL sequences, four genes (AtSSL4–AtSSL7) arranged in tandem on chromosome 3 show more similarity to SSL genes from Drosophila melanogaster and Caenorhabditis elegans than to other Arabidopsis SSL genes. To examine whether any of the four AtSSL genes are immune-inducible, we analysed the expression of each of the four AtSSL genes after exposure to microbial pathogens, wounding and plant defence elicitors using real-time quantitative RT-PCR, Northern blot hybridisation and Western blot analysis with antibodies raised against recombinant AtSSL proteins. While the AtSSL4 gene was constitutively expressed and not significantly induced by any treatment, the other three AtSSL genes were induced to various degrees by plant defence signalling compounds, such as salicylic acid, methyl jasmonate and ethylene, as well as by wounding and exposure to the plant pathogens Alternaria brassicicola and cucumber mosaic virus. Our data demonstrate that the four SSL-coding genes are regulated individually...

Sequence-based identification of microbial pathogens: a reconsideration of Koch's postulates.

Fredericks, D N; Relman, D A
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1996 EN
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478.44934%
Over 100 years ago, Robert Koch introduced his ideas about how to prove a causal relationship between a microorganism and a disease. Koch's postulates created a scientific standard for causal evidence that established the credibility of microbes as pathogens and led to the development of modern microbiology. In more recent times, Koch's postulates have evolved to accommodate a broader understanding of the host-parasite relationship as well as experimental advances. Techniques such as in situ hybridization, PCR, and representational difference analysis reveal previously uncharacterized, fastidious or uncultivated, microbial pathogens that resist the application of Koch's original postulates, but they also provide new approaches for proving disease causation. In particular, the increasing reliance on sequence-based methods for microbial identification requires a reassessment of the original postulates and the rationale that guided Koch and later revisionists. Recent investigations of Whipple's disease, human ehrlichiosis, hepatitis C, hantavirus pulmonary syndrome, and Kaposi's sarcoma illustrate some of these issues. A set of molecular guidelines for establishing disease causation with sequence-based technology is proposed, and the importance of the scientific concordance of evidence in supporting causal associations is emphasized.

Subversion of the chemokine world by microbial pathogens

Liston, Adrian; McColl, Shaun
Fonte: The Company of Biologists Ltd Publicador: The Company of Biologists Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
489.89707%
It is well known that microbial pathogens are able to subvert the host immune system in order to increase microbial replication and propagation. Recent research indicates that another arm of the immune response, that of the chemokine system, is also subject to this sabotage, and is undermined by a range of microbial pathogens, including viruses, bacteria, and parasites. Currently, it is known that the chemokine system is being challenged by a number of mechanisms, and still more are likely to be discovered with further research. Here we first review the general mechanisms by which microbial pathogens bypass mammalian chemokine defences. Broadly, these can be grouped as viral chemokine interacting proteins, microbial manipulation of host chemokine and chemokine receptor expression, microbial blockade of host chemokine receptor signalling, and the largely hypothetical mechanisms of microbial enhancement of host anti-chemokine networks (including digestion, antagonism, and neutralisation of host chemokines and chemokine receptors). We then discuss the potential results of these interactions in terms of outcome of infection.