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Pathogen Interactions (pathogen + interaction)
Selected AbstractsCandida albicans proteinases and host/pathogen interactionsCELLULAR MICROBIOLOGY, Issue 10 2004Julian Naglik Summary Candida infections are common, debilitating and often recurring fungal diseases and a problem of significant clinical importance. Candida albicans, the most virulent of the Candida spp., can cause severe mucosal and life-threatening systemic infections in immunocompromised hosts. Attributes that contribute to C. albicans virulence include adhesion, hyphal formation, phenotypic switching and extracellular hydrolytic enzyme production. The extracellular hydrolytic enzymes, especially the secreted aspartyl proteinases (Saps), are one of few gene products that have been shown to directly contribute to C. albicans pathogenicity. Because C. albicans is able to colonize and infect almost every tissue in the human host, it may be crucial for the fungus to possess a number of similar but independently regulated and functionally distinct secreted proteinases to provide sufficient flexibility in order to survive and promote infection at different niche sites. The aim of this review is to explore the functional roles of the C. albicans proteinases and how they may contribute to the host/pathogen interaction in vivo. [source] Resting spore formation of aphid-pathogenic fungus Pandora nouryi depends on the concentration of infective inoculumENVIRONMENTAL MICROBIOLOGY, Issue 7 2008Zhi-Hong Huang Summary Resting spore formation of some aphid-pathogenic Entomophthorales is important for the seasonal pattern of their prevalence and survival but this process is poorly understood. To explore the possible mechanism involved in the process, Pandora nouryi (obligate aphid pathogen) interacted with green peach aphid Myzus persicae on cabbage leaves under favourable conditions. Host nymphs showered with primary conidia of an isolate (LC50: 0.9,6.7 conidia mm,2 4,7 days post shower) from air captures in the low-latitude plateau of China produced resting spores (azygospores), primary conidia or both spore types. Surprisingly, the proportion of mycosed cadavers forming resting spores (Pcfrs) increased sharply within the concentrations (C) of 28,240 conidia mm,2, retained high levels at 240,1760, but was zero or extremely low at 0.3,16. The Pcfrs,C relationship fit well the logistic equation Pcfrs = 0.6774/[1 + exp(3.1229,0.0270C)] (r2 = 0.975). This clarified for the first time the dependence of in vivo resting spore formation of P. nouryi upon the concentration of infective inoculum. A hypothesis is thus proposed that some sort of biochemical signals may exist in the host,pathogen interaction so that the fungal pathogen perceives the signals for prompt response to forthcoming host-density changes by either producing conidia for infecting available hosts or forming resting spores for surviving host absence in situ. [source] IDENTIFYING COEVOLUTIONARY PATTERNS IN HUMAN LEUKOCYTE ANTIGEN (HLA) MOLECULESEVOLUTION, Issue 5 2010Xiaowei Jiang The antigenic peptide, major histocompatibility complex molecule (MHC; also called human leukocyte antigen, HLA), coreceptor CD8, or CD4 and T-cell receptor (TCR) function as a complex to initiate effectors' mechanisms of the immune system. The tight functional and physical interaction among these molecules may have involved strong coevolution links among domains within and between proteins. Despite the importance of unraveling such dependencies to understand the arms race of host,pathogen interaction, no previous studies have aimed at achieving such an objective. Here, we perform an exhaustive coevolution analysis and show that indeed such dependencies are strongly shaping the evolution and probably the function of these molecules. We identify intramolecular coevolution in HLA class I and II at domains important for their immune activity. Most of the amino acid sites identified to be coevolving in HLAI have been also detected to undergo positive Darwinian selection highlighting therefore their adaptive value. We also identify coevolution among antigen-binding pockets (P1-P9) and among these and TCR-binding sites. Conversely to HLAI, coevolution is weaker in HLAII. Our results support that such coevolutionary patterns are due to selective pressures of host,pathogen coevolution and cooperative binding of TCRs, antigenic peptides, and CD8/CD4 to HLAI and HLAII. [source] Molecular and infection biology of the horse pathogen Rhodococcus equiFEMS MICROBIOLOGY REVIEWS, Issue 5 2009Kristine Von Bargen Abstract The soil actinomycete Rhodococcus equi is a pulmonary pathogen of young horses and AIDS patients. As a facultative intracellular bacterium, R. equi survives and multiplies in macrophages and establishes its specific niche inside the host cell. Recent research into chromosomal virulence factors and into the role of virulence plasmids in infection and host tropism has presented novel aspects of R. equi infection biology and pathogenicity. This review will focus on new findings in R. equi biology, the trafficking of R. equi -containing vacuoles inside host cells, factors involved in virulence and host resistance and on host,pathogen interaction on organismal and cellular levels. [source] Host behaviour and exposure risk in an insect,pathogen interactionJOURNAL OF ANIMAL ECOLOGY, Issue 4 2010Benjamin J. Parker Summary 1.,Studies of variability in host resistance to disease generally emphasize variability in susceptibility given exposure, neglecting the possibility that hosts may vary in behaviours that affect the risk of exposure. 2.,In many insects, horizontal transmission of baculoviruses occurs when larvae consume foliage contaminated by the cadavers of virus-infected conspecific larvae; so, host behaviour may have a strong effect on the risk of infection. 3.,We studied variability in the behaviour of gypsy moth (Lymantria dispar) larvae, which are able to detect and avoid virus-contaminated foliage. 4.,Our results show that detection ability can be affected by the family line that larvae originate from, even at some distance from a virus-infected cadaver, and suggest that cadaver-detection ability may be heritable. 5.,There is thus the potential for natural selection to act on cadaver-detection ability, and thereby to affect the dynamics of pathogen-driven cycles in gypsy moth populations. 6. We argue that host behaviour is a neglected component in studies of variability in disease resistance. [source] Co-chaperone BAG3 and adenovirus penton base protein partnershipJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 3 2010E. Gout Abstract The BAG family of Hsp70/Hsc70 co-chaperones is characterised by the presence of a conserved BAG domain at the carboxyl-terminus. BAG3 protein is the only member of this family containing also the N-terminally located WW domain. We describe here the identification of adenovirus (Ad) penton base protein as the first BAG3 partner recognising BAG3 WW domain. Ad penton base is the viral capsid constituent responsible for virus internalisation. It contains in the N-terminal part two conserved PPxY motifs, known ligands of WW domains. In cells producing Ad penton base protein, cytoplasmic endogenous BAG3 interacts with it and co-migrates to the nucleus. Preincubation of BAG3 with Ad base protein results in only slight modulation of BAG3 co-chaperone activity, suggesting that this interaction is not related to the classical BAG3 co-chaperone function. However, depletion of BAG3 impairs the cell entry of the virus and viral progeny production in Ad-infected cells, suggesting that the interaction between virus penton base protein and cellular co-chaperone BAG3 positively influences virus life cycle. These results thus demonstrate a novel host,pathogen interaction, which contributes to the successful infectious life cycle of adenoviruses. In addition, these data enrich our knowledge about the multifunctionality of the BAG3 co-chaperone. J. Cell. Biochem. 111: 699,708, 2010. © 2010 Wiley-Liss, Inc. [source] Pathogen fitness components and genotypes differ in their sensitivity to nutrient and temperature variation in a wild plant,pathogen associationJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2007A.-L. LAINE Abstract Understanding processes maintaining variation in pathogen life-history stages affecting infectivity and reproduction is a key challenge in evolutionary ecology. Models of host,parasite coevolution are based on the assumption that genetic variation for host,parasite interactions is a significant cause of variation in infection, and that variation in environmental conditions does not overwhelm the genetic basis. However, surprisingly little is known about the stability of genotype,genotype interactions under variable environmental conditions. Here, using a naturally occurring plant,pathogen interaction, I tested whether the two distinct aspects of the infection process , infectivity and transmission potential , vary over realistic nutrient and temperature gradients. I show that the initial pathogen infectivity and host resistance responses are robust over the environmental gradients. However, for compatible responses there were striking differences in how different pathogen life-history stages and host and pathogen genotypes responded to environmental variation. For some pathogen genotypes even slight changes in temperature arrested spore production, rendering the developing infection ineffectual. The response of pathogen genotypes to environmental gradients varied in magnitude and even direction, so that their rankings changed across the abiotic gradients. Hence, the variable environment of spatially structured host,parasite interactions may strongly influence the maintenance of polymorphism in pathogen life-history stages governing transmission, whereas evolutionary trajectories of infectivity may be unaffected by the surrounding environment. [source] Experimental periodontitis in mice selected for maximal or minimal inflammatory reactions: increased inflammatory immune responsiveness drives increased alveolar bone loss without enhancing the control of periodontal infectionJOURNAL OF PERIODONTAL RESEARCH, Issue 4 2009A. P. F. Trombone Background and Objective:, Inflammatory immune reactions that occur in response to periodontopathogens are thought to protect the host against infection, but may trigger periodontal destruction. However, the molecular and genetic mechanisms underlying host susceptibility to periodontal infection and to periodontitis development have still not been established in detail. Material and Methods:, In this study, we examined the mechanisms that modulate the outcome of Aggregatibacter (Actinobacillus) actinomycetemcomitans -induced periodontal disease in mice mouse strains selected for maximal (AIRmax) or minimal (AIRmin) inflammatory reactions. Results:, Our results showed that AIRmax mice developed a more severe periodontitis than AIRmin mice in response to A. actinomycetemcomitans infection, and this periodontitis was characterized by increased alveolar bone loss and inflammatory cell migration to periodontal tissues. In addition, enzyme-linked immunosorbent assays demonstrated that the levels of the cytokines interleukin-1,, tumor necrosis factor-, and interleukin-17 were higher in AIRmax mice, as were the levels of matrix metalloproteinase (MMP)-2, MMP-13 and receptor activator of nuclear factor-,B ligand (RANKL) mRNA levels. However, the more intense inflammatory immune reaction raised by the AIRmax strain, in spite of the higher levels of antimicrobial mediators myeloperoxidase and inducible nitric oxide synthase, did not enhance the protective immunity to A. actinomycetemcomitans infection, because both AIRmax and AIRmin strains presented similar bacterial loads in periodontal tissues. In addition, the AIRmax strain presented a trend towards higher levels of serum C-reactive protein during the course of disease. Conclusion:, Our results demonstrate that the intensity of the inflammatory immune reaction is associated with the severity of experimental periodontitis, but not with the control of A. actinomycetemcomitans periodontal infection, suggesting that the occurrence of hyperinflammatory genotypes may not be an evolutionary advantage in the complex host,pathogen interaction observed in periodontal diseases. [source] Accumulation of Defence Response-related and Unique Expressed Sequence Tags during the Incompatible Interaction in the Oryza sativa,Magnaporthe oryzae PathosystemJOURNAL OF PHYTOPATHOLOGY, Issue 7-8 2009Rekha Dixit Abstract Resistance gene-dependent accumulation of expressed sequence tags (ESTs) was studied in a blast resistant, Oryza sativa ssp. indica cv. Tetep after challenge inoculation with an incompatible race of Magnaporthe oryzae. The nucleotide sequence of 287 randomly selected cDNA clones from the rice cDNA library constructed from the RNA isolated after challenge inoculation of the host was obtained and submitted in NCBI Genbank (Accession Nos. DN475717,DN475431). Of these, 184 (63%) ESTs were highly representative of the rice transcriptomes. A set of 178 unique transcripts was identified after assembly of 287 ESTs into unigenes. These unigenes were categorized into 17 functional groups. Analysis of this EST library illustrated a broad functional representation. Twenty-one unigenes were identified as putative homologues of the genes that were up regulated during host,pathogen interaction. Similarity search of 178 unigenes with NCBI database of 14 plants unigenes showed similarity ranging from 29,100%. The unigenes obtained in this study were physically located on the pseudomolecules of rice genome. This information can be used for determining the arrays of genes being expressed during Oryza sativa,M. oryzae interactions, which will be helpful in understanding the molecular basis of disease resistance. [source] The Interaction of Plasmodiophora brassicae and Arabidopsis thaliana: Parameters for Disease Quantification and Screening of Mutant LinesJOURNAL OF PHYTOPATHOLOGY, Issue 11-12 2002J. Siemens Abstract The soil-borne obligate pathogen Plasmodiophora brassicae causes clubroot disease in species of Brassicaceae, including Arabidopsis thaliana. The host,pathogen interaction was studied with respect to the age of the plant at the time point of inoculation and to different infection pressures in order to establish a standardization of infection parameters and evaluation of disease extent for A. thaliana lines. Spore number per root weight, root and shoot weight of inoculated and non-inoculated plants as well as infection rate and disease index (DI) were analysed and correlated. The disease extent of different lines was comparable as measured by the relation of root weight of inoculated and non-inoculated plants (Ri/Rni index) and the DI. Most of the 71 screened A. thaliana lines turned out to be susceptible. However, the mutant lines tu8, tu3, det1-1, and rhd3-1 showed a certain degree of tolerance under specific culture conditions. The reactions of rhd3-1 indicate that hypertrophy is a prerequisite for maturation of the pathogen. The reactions of the tu3 and tu8 mutants indicate a role of indole glucosinolates and indole-3-acetonitrile/IAA in development of clubroot disease. [source] The role of plant defence proteins in fungal pathogenesisMOLECULAR PLANT PATHOLOGY, Issue 5 2007RICARDO B. FERREIRA SUMMARY It is becoming increasingly evident that a plant,pathogen interaction may be compared to an open warfare, whose major weapons are proteins synthesized by both organisms. These weapons were gradually developed in what must have been a multimillion-year evolutionary game of ping-pong. The outcome of each battle results in the establishment of resistance or pathogenesis. The plethora of resistance mechanisms exhibited by plants may be grouped into constitutive and inducible, and range from morphological to structural and chemical defences. Most of these mechanisms are defensive, exhibiting a passive role, but some are highly active against pathogens, using as major targets the fungal cell wall, the plasma membrane or intracellular targets. A considerable overlap exists between pathogenesis-related (PR) proteins and antifungal proteins. However, many of the now considered 17 families of PR proteins do not present any known role as antipathogen activity, whereas among the 13 classes of antifungal proteins, most are not PR proteins. Discovery of novel antifungal proteins and peptides continues at a rapid pace. In their long coevolution with plants, phytopathogens have evolved ways to avoid or circumvent the plant defence weaponry. These include protection of fungal structures from plant defence reactions, inhibition of elicitor-induced plant defence responses and suppression of plant defences. A detailed understanding of the molecular events that take place during a plant,pathogen interaction is an essential goal for disease control in the future. [source] Claviceps purpurea: molecular aspects of a unique pathogenic lifestyleMOLECULAR PLANT PATHOLOGY, Issue 5 2004PAUL TUDZYNSKI SUMMARY Claviceps purpurea is a ubiquitous pathogen of cereals and grasses, causing Ergot disease, which results in substitution of grains by sclerotia. These overwintering structures contain ergot-alkaloids, which can cause severe intoxication in mammals. C. purpurea is an interesting model system for the study of host,pathogen interaction. It displays strict organ specificity, attacking exclusively young grass ovaries. It is optimally adapted to this special niche of infection, probably by mimicry of pollen tubes: there are no resistance genes known, and no effective resistance reactions can be detected in the early steps of infection. In this early phase of host tissue colonization the fungus shows directed, almost unbranched growth towards the base of the ovary. Thus, C. purpurea represents one of the few systems in which directed growth in filamentous fungi can be studied. Finally, the fungus behaves as a true biotroph in planta, although it can be easily grown in axenic culture. We describe here the tools available to study this interesting pathogen, report on recent molecular investigations concerning the role of cell-wall-degrading enzymes and of reactive oxygen species in this specialized interaction, and present an update of the signalling cascades involved in early events of pathogenesis. [source] Experimental superficial candidiasis on tissue modelsMYCOSES, Issue 4 2010J. A. M. S. Jayatilake Summary Candida species are common pathogens causing superficial mycoses primarily affecting the mucosa and the skin in humans. Crucial steps during pathogenesis of superficial candidiasis comprise fungal adhesion, colonisation and subsequent penetration of the respective tissues. Exploring these pathological events and perhaps fungal and tissue responses towards drug treatment is imperative in the management of this infection. Unfortunately, pathological biopsies of superficial candidiasis do not exhibit the early changes in the host,pathogen interaction as the tissues are already invaded by the fungi. In vivo experimental assessments of pathological processes of superficial candidiasis are also limited because of the difficulties in providing reproducible and comparable conditions in the host environment. Conversely, in vitro models have helped studying fungal,host interactions under more defined and controlled conditions. Some common in vitro models used to simulate superficial candidiasis are chick chorioallantoic membrane, mucosal explants and single layer or multiple layer cell cultures. Interestingly, these experimental approaches share advantages as well as disadvantages when compared with in vivo conditions. Hence, this review intends to discuss about the experimental superficial candidiasis produced in various tissue models and their advantages as well as disadvantages with a particular reference to further improvement of validity and reliability of such experiments. [source] Molecular and histochemical characterisation of two distinct poplar Melampsora leaf rust pathosystemsPLANT BIOLOGY, Issue 2 2010B. Boyle Abstract In this study, we compared interactions of two Melampsora foliar rust species with poplar, which resulted in either limited or abundant pathogen proliferation. In the pathosystem exhibiting limited pathogen growth, a defence response was observed after invasion of poplar leaf tissues by the biotroph, with late and clear production of reactive oxygen species (ROS) and other products. Characterisation of the histological, biochemical and transcriptional events occurring in both pathosystems showed striking similarity with components of plant defence reactions observed during qualitative resistance. Key components associated with development of an active defence response, such as up-regulation of pathogenesis-related (PR) genes, were observed during infection. Moreover, the time course and strength of gene induction appear to be critical determinants for the outcome of the tree,pathogen interaction. This work provides basic biochemical characterisation and expression data for the study of so-called partial resistance in the poplar,rust pathosystem, which is also applicable to other plant,pathogen interactions resulting in quantitative disease resistance. [source] Citrus tristeza virus resistance in a core collection of sour orange based on a diversity study of three germplasm collections using QTL-linked markersPLANT BREEDING, Issue 4 2008G. P. Bernet Abstract Seven markers linked to QTL involved in CTV accumulation, leafminer resistance and apomictic reproduction were used to characterize 64 sour orange (Citrus aurantium L.) accessions from three national collections in order to identify a representative core in which the resistance behaviour against two Citrus tristeza virus (CTV) isolates was studied. Different degrees of apomixis were found between the foreign collections. Most of the C. aurantium accessions fall into three main groups based on three multilocus genotypes. The haplotype diversity at three CTV accumulation QTL-linked markers was further studied by sequence analysis of alleles. Genotypic and allelic diversity at one of them, tightly linked to Ctv-R2 in Poncirus trifoliata (L.) Raf., match the plant,CTV interaction types reported among Poncirus and Citrus species. Only those selected accessions from the major group presented CTV resistance during 30 months of continuous growth, but later the resistance broke down in some plants. CTV tolerance appears related to slow growing genotypes. Certain micronutrients: Mn, and B depending on the accession, might play a relevant role in this host,pathogen interaction particularly in alkaline soils. [source] Aggressiveness of Phytophthora infestans and phenotypic analysis of resistance in wild Petota accessions in EcuadorPLANT PATHOLOGY, Issue 4 2007M. G. Chacón The aggressiveness of four Phytophthora infestans isolates collected from wild and cultivated potato species (sect. Petota) and the level of resistance of nine Petota species were assessed in the highland tropics of Ecuador. For this, isolates of P. infestans were inoculated on whole plants of Petota species in the field and net house and six epidemiological components , infection frequency (IF), incubation period (IP), latent period (LP), lesion size (LS), lesion growth rate (LGR), and relative area under the lesion expansion curve (RAULEC) , were measured during a single infection cycle. Additionally, host specificity was determined by testing for a significant host by pathogen interaction using the same components. The results showed significant differences among isolates of the EC-1 clonal lineage for IP, IF, and RAULEC. Significant differences among isolates were not found for the other components measured. There were significant differences in resistance among the accessions of Petota hosts tested. RAULEC, LGR, LP, and LS were in general more adequate in differentiating among the more resistant and more susceptible accessions but the importance of each component varied with host species. There was slight and inconsistent evidence for the existence of host specificity in some isolates of Petota hosts. IP was the only component for which a significant host by isolate interaction was observed and in most cases the isolates had the greatest aggressiveness on their hosts of origin. [source] Differential induction of superoxide dismutase in downy mildew-resistant and -susceptible genotypes of pearl milletPLANT PATHOLOGY, Issue 4 2002M. P. Babitha Differential induction of superoxide dismutase (SOD) in downy mildew-resistant and -susceptible genotypes of pearl millet (Pennisetum glaucum) was observed on inoculation with Sclerospora graminicola. SOD activity was studied in resistant (IP18292) and susceptible (23B) pearl millet seedlings inoculated with S. graminicola. SOD activity increased by 2·3-fold in resistant seedlings upon inoculation. SOD activity was greatest in roots, with a specific activity of 3182 U per mg protein, after inoculation. SOD activity increased in all the resistant genotypes upon inoculation with S. graminicola. Native PAGE analysis showed four isozymes of SOD, three of which (SOD-1, -2 and -4) were Cu/Zn-SOD, whereas isozyme SOD-3 was Mn-SOD. This study also revealed increased intensity of all four isozymes of SOD in the resistant genotype upon inoculation. The involvement of SOD in pearl millet (host),downy mildew pathogen interaction is discussed. [source] Organization and sequence of four flagellin-encoding genes of Edwardsiella ictaluriAQUACULTURE RESEARCH, Issue 10 2009Victor S Panangala Abstract Edwardsiella ictaluri, the cause of enteric septicaemia in channel catfish (Ictalurus punctatus), is motile by means of peritrichous flagella. We determined the complete flagellin gene sequences and their organization in E. ictaluri by sequencing genomic segments from a ,-ZAP phage genomic library of E. ictaluri. Four flagellin genes (fliC1, fliC2, fliC3 and fliC4) are arranged in tandem within 6 kb in the E. ictaluri genome. Each flagellin-coding sequence is preceded by a ,28 recognition site consensus sequence. The predicted amino acid sequences of all four flagellin proteins (between 36 and 37.5 kDa) are similar in the N-terminal (1,160 aa) and C-terminal (last 74 aa) portions and are divergent in the central portion of the proteins. Proteins encoded by flC1, fliC2 and fliC3 are more similar to each other (88,90% aa identity) than to the protein encoded by fliC4 (76,78% aa identity). basic local alignment search tool analysis of GenBank sequences showed that all flagellin aa sequences are more similar to those of Serratia marcescens (72,74% identity) than to those of Edwardsiella tarda (,64% identity). Primary determination of E. ictaluri flagellin gene sequences facilitate advanced studies on the role of flagella in host,pathogen interaction. [source] Immune subversion by chromatin manipulation: a ,new face' of host,bacterial pathogen interactionCELLULAR MICROBIOLOGY, Issue 8 2008Laurence Arbibe Summary Bacterial pathogens have evolved various strategies to avoid immune surveillance, depending of their in vivo,lifestyle'. The identification of few bacterial effectors capable to enter the nucleus and modifying chromatin structure in host raises the fascinating questions of how pathogens modulate chromatin structure and why. Chromatin is a dynamic structure that maintains the stability and accessibility of the host DNA genome to the transcription machinery. This review describes the various strategies used by pathogens to interface with host chromatin. In some cases, chromatin injury can be a strategy to take control of major cellular functions, such as the cell cycle. In other cases, manipulation of chromatin structure at specific genomic locations by modulating epigenetic information provides a way for the pathogen to impose its own transcriptional signature onto host cells. This emerging field should strongly influence our understanding of chromatin regulation at interphase nucleus and may provide invaluable openings to the control of immune gene expression in inflammatory and infectious diseases. [source] Seasonality and the dynamics of infectious diseasesECOLOGY LETTERS, Issue 4 2006Sonia Altizer Abstract Seasonal variations in temperature, rainfall and resource availability are ubiquitous and can exert strong pressures on population dynamics. Infectious diseases provide some of the best-studied examples of the role of seasonality in shaping population fluctuations. In this paper, we review examples from human and wildlife disease systems to illustrate the challenges inherent in understanding the mechanisms and impacts of seasonal environmental drivers. Empirical evidence points to several biologically distinct mechanisms by which seasonality can impact host,pathogen interactions, including seasonal changes in host social behaviour and contact rates, variation in encounters with infective stages in the environment, annual pulses of host births and deaths and changes in host immune defences. Mathematical models and field observations show that the strength and mechanisms of seasonality can alter the spread and persistence of infectious diseases, and that population-level responses can range from simple annual cycles to more complex multiyear fluctuations. From an applied perspective, understanding the timing and causes of seasonality offers important insights into how parasite,host systems operate, how and when parasite control measures should be applied, and how disease risks will respond to anthropogenic climate change and altered patterns of seasonality. Finally, by focusing on well-studied examples of infectious diseases, we hope to highlight general insights that are relevant to other ecological interactions. [source] Novel strategies targeting pathogen transmission reduction in insect vectors: Tsetse-transmitted trypanosomiasis controlENTOMOLOGICAL RESEARCH, Issue 4 2007Brian L. WEISS Abstract Insect vectors are essential for the transmission of important human diseases such as malaria, leishmaniasis, Chagas and sleeping sickness. Insects are also responsible for the transmission of agricultural diseases that affect livestock and crops. Traditionally, control of the vector populations has been an effective disease management strategy. Recently, vector control strategies have been fortified by research in insect biology and in insect,pathogen interactions as well as by the development of transgenic technologies. In addition to insect population reduction methods, disease control via selective elimination of pathogens in insects can now be explored. Here we explore the tsetse vectors of African trypanosomes and describe the application of recent knowledge gained in their symbiotic, reproductive and vectorial biology to develop novel disease control strategies. [source] NATURAL SELECTION ON A POLYMORPHIC DISEASE-RESISTANCE LOCUS IN IPOMOEA PURPUREAEVOLUTION, Issue 2 2007Joel M. Kniskern Although disease-resistance polymorphisms are common in natural plant populations, the mechanisms responsible for this variation are not well understood. Theoretical models predict that balancing selection can maintain polymorphism within a population if the fitness effects of a resistance allele vary from a net cost to a net benefit, depending upon the extent of pathogen damage. However, there have been a few attempts to determine how commonly this mechanism operates in natural plant,pathogen interactions. Ipomoea purpurea populations are often polymorphic for resistance and susceptibility alleles at a locus that influences resistance to the fungal pathogen, Coleosporium ipomoeae. We measured the fitness effects of resistance over three consecutive years at natural and manipulated levels of damage to characterize the type of selection acting on this locus. Costs of resistance varied in magnitude from undetectable to 15.5%, whereas benefits of resistance sometimes equaled, but never exceeded, these costs. In the absence of net benefits of resistance at natural or elevated levels of disease, we conclude that selection within individual populations of I. purpurea probably does not account completely for maintenance of this polymorphism. Rather, the persistence of this polymorphism is probably best explained by a combination of variable selection and meta-population processes. [source] Expression of the recombinant bacterial outer surface protein A in tobacco chloroplasts leads to thylakoid localization and loss of photosynthesisFEBS JOURNAL, Issue 21 2007Anna Hennig Bacterial lipoproteins play crucial roles in host,pathogen interactions and pathogenesis and are important targets for the immune system. A prominent example is the outer surface protein A (OspA) of Borrelia burgdorferi, which has been efficiently used as a vaccine for the prevention of Lyme disease. In a previous study, OspA could be produced in tobacco chloroplasts in a lipidated and immunogenic form. To further explore the potential of chloroplasts for the production of bacterial lipoproteins, the role of the N-terminal leader sequence was investigated. The amount of recombinant OspA could be increased up to ten-fold by the variation of the insertion site in the chloroplast genome. Analysis of OspA mutants revealed that replacement of the invariant cysteine residue as well as deletion of the leader sequence abolishes palmitolyation of OspA. Also, decoration of OspA with an N-terminal eukaryotic lipidation motif does not lead to palmitoylation in chloroplasts. Strikingly, the bacterial signal peptide of OspA efficiently targets the protein to thylakoids, and causes a mutant phenotype. Plants accumulating OspA at 10% total soluble protein could not grow without exogenously supplied sugars and rapidly died after transfer to soil under greenhouse conditions. The plants were found to be strongly affected in photosystem II, as revealed by the analyses of temporal and spatial dynamics of photosynthetic activity by chlorophyll fluorescence imaging. Thus, overexpression of OspA in chloroplasts is limited by its concentration-dependent interference with essential functions of chloroplastic membranes required for primary metabolism. [source] Regulation of whole bacterial pathogen transcription within infected hostsFEMS MICROBIOLOGY REVIEWS, Issue 3 2008My-Van La Abstract DNA microarrays are a powerful and promising approach to gain a detailed understanding of the bacterial response and the molecular cross-talk that can occur as a consequence of host,pathogen interactions. However, published studies mainly describe the host response to infection. Analysis of bacterial gene regulation in the course of infection has confronted many challenges. This review summarizes the different strategies used over the last few years to investigate, at the genomic scale, and using microarrays, the alterations in the bacterial transcriptome in response to interactions with host cells. Thirty-seven studies involving 19 different bacterial pathogens were compiled and analyzed. Our in silico comparison of the transcription profiles of bacteria grown in broth or in contact with eukaryotic cells revealed some features commonly observed when bacteria interact with host cells, including stringent response and cell surface remodeling. [source] Downy mildew (Plasmopara viticola) epidemics on grapevine under climate changeGLOBAL CHANGE BIOLOGY, Issue 7 2006SALINARI FRANCESCA Abstract As climate is a key agro-ecosystem driving force, climate change could have a severe impact on agriculture. Many assessments have been carried out to date on the possible effects of climate change (temperature, precipitation and carbon dioxide concentration changes) on plant physiology. At present however, likely effects on plant pathogens have not been investigated deeply. The aim of this work was to simulate future scenarios of downy mildew (Plasmopara viticola) epidemics on grape under climate change, by combining a disease model to output from two general circulation models (GCMs). Model runs corresponding to the SRES-A2 emissions scenario, characterized by high projections of both population and greenhouse gas emissions from present to 2100, were chosen in order to investigate impacts of worst-case scenarios, among those currently available from IPCC. Three future decades were simulated (2030, 2050, 2080), using as baseline historical series of meteorological data collected from 1955 to 2001 in Acqui Terme, an important grape-growing area in the north-west of Italy. Both GCMs predicted increase of temperature and decrease of precipitation in this region. The simulations obtained by combining the disease model to the two GCM outputs predicted an increase of the disease pressure in each decade: more severe epidemics were a direct consequence of more favourable temperature conditions during the months of May and June. These negative effects of increasing temperatures more than counterbalanced the effects of precipitation reductions, which alone would have diminished disease pressure. Results suggested that, as adaptation response to future climate change, more attention would have to be paid in the management of early downy mildew infections; two more fungicide sprays were necessary under the most negative climate scenario, compared with present management regimes. At the same time, increased knowledge on the effects of climate change on host,pathogen interactions will be necessary to improve current predictions. [source] Evolution of the innate immune system: the worm perspectiveIMMUNOLOGICAL REVIEWS, Issue 1 2004Hinrich Schulenburg Summary:, Simple model organisms that are amenable to comprehensive experimental analysis can be used to elucidate the molecular genetic architecture of complex traits. They can thereby enhance our understanding of these traits in other organisms, including humans. Here, we describe the use of the nematode Caenorhabditis elegans as a tractable model system to study innate immunity. We detail our current understanding of the worm's immune system, which seems to be characterized by four main signaling cascades: a p38 mitogen-activated protein kinase, a transforming growth factor-,-like, a programed cell death, and an insulin-like receptor pathway. Many details, especially regarding pathogen recognition and immune effectors, are only poorly characterized and clearly warrant further investigation. We additionally speculate on the evolution of the C. elegans immune system, taking into special consideration the relationship between immunity, stress responses and digestion, the diversification of the different parts of the immune system in response to multiple and/or coevolving pathogens, and the trade-off between immunity and host life history traits. Using C. elegans to address these different facets of host,pathogen interactions provides a fresh perspective on our understanding of the structure and complexity of innate immune systems in animals and plants. [source] Short-term epidemic dynamics in the Cakile maritima,Alternaria brassicicola host,pathogen associationJOURNAL OF ECOLOGY, Issue 5 2001Peter H. Thrall Summary 1Studies combining within- and among-population processes are crucial for understanding ecological and co-evolutionary dynamics in host,pathogen interactions. We report on work over an 18-month period involving multiple beach populations of the plant Cakile maritima and its fungal pathogen Alternaria brassicicola along the south-east coast of Australia. 2Results from permanent transects replicated on several beaches show that disease incidence and prevalence vary significantly with plant age, class and distance from the sea, as well as time during the season. Plant density is also positively related to disease levels. 3Results from three subregions indicate that disease persistence depends on survival of infected plants behind the foredunes of protected beaches. Population extinction was more likely on beaches with greater wind exposure and sea access, with the latter also related to colonization consistent with the dispersal of Cakile seeds via ocean currents. 4Although disease dynamics during the epidemic were similar across subregions, the severity of the epidemic varied significantly among these areas, suggesting that large-scale environmental factors may influence the timing and development of the epidemic. 5Estimates of synchrony in disease dynamics indicated that populations within a subregion were significantly correlated with respect to epidemic development. There was, however, no evidence for spatial synchrony in disease dynamics based on among-population covariances in disease prevalence and interbeach distances. Populations within a subregion were thus often at quite different phases of the epidemic at any given time. [source] Proteomic identification of biomarkers related to Helicobacter pylori -associated gastroduodenal disease: Challenges and opportunitiesJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 11 2008Ming-Shiang Wu Abstract Helicobacter pylori colonize the stomach of over half the world's population. While 80,90% H. pylori -infected individuals have clinically asymptomatic gastritis, 10,15% develop peptic ulcer, and 1,2% gastric malignancies. These variable clinical outcomes have led to an interest in prognostic indicators. The current disease paradigm suggests that host genetics and bacterial virulence both play important roles in modulating the final outcome of H. pylori infection. Elucidation of the interaction between host and bacterium is essential to clarify pathogenesis and to develop new strategies for prevention and treatment. Proteomic technology is a powerful tool for simultaneously monitoring proteins and protein variation on a large scale in biological samples. It has provided an unprecedented opportunity to survey a cell's translational landscape comprehensively, and the results may allow in-depth analyses of host and pathogen interactions. Using this high-throughput platform and taking advantage of complete sequences for both the H. pylori and the human genome in available databases, we have identified several crucial proteins that have pathogenic and prognostic potential. Among them, antibodies to AhpC and GroEs of H. pylori could be utilized for identification of patients who are at high risk of disease complications after H. pylori infection. Evolving proteomic technologies, together with appropriate clinical phenotyping and genotype information should enhance understanding of disease pathogenesis and lead to more precise prediction of variable disease outcomes. It will also facilitate development of biomarkers for diagnosis, treatment, and prevention of H. pylori infection. [source] Development of Greenhouse Inoculation Procedures for Evaluation of Partial Resistance to Cercospora zeae-maydis in Maize InbredsJOURNAL OF PHYTOPATHOLOGY, Issue 11-12 2005G. Asea Abstract Greenhouse experiments were conducted to determine the effects of inoculation methods on incubation period, lesion length, percentage leaf area affected and sporulation of Cercospora zeae-maydis on young maize (Zea mays L.) plants inoculated at V3 growth stage. Seedling plants were inoculated by four methods: (i) application of conidial suspension while puncturing the leaves within the whorl several times, (ii) spraying conidial suspension on leaves, (iii) placing colonized agar into lateral slits in leaves and (iv) placing colonized agar into whorls. Analysis of variance revealed a significant effect of genotype and inoculation method on several components of resistance and overall disease severity. Application of conidial suspension while puncturing the whorl was found to be the least laborious method, and it produced characteristic symptoms of gray leaf spot. Consistent trends were observed in classification of inbreds to resistant, susceptible and intermediate classes. Increasing the duration of exposure to high humidity by placing plastic bags over plants for 5 days significantly increased disease severity (P , 0.001). Cercospora zeae-maydis produced conidia in all the lesions examined. Spore production was generally most abundant in lesions on susceptible inbreds that displayed necrotic lesion types (LT) and least abundant in lesions on resistant inbreds that were characterized by chlorotic and fleck LTs. The results demonstrated that inoculations in the greenhouse can provide an indication of inbred responses to C. zeae-maydis and may be useful in evaluating resistance and in studies of host,pathogen interactions. [source] Microsatellite loci for the fungus Ascosphaera apis: cause of honey bee chalkbrood diseaseMOLECULAR ECOLOGY RESOURCES, Issue 3 2009STEPHEN A. REHNER Abstract The fungus Ascosphaera apis is a worldwide fungal pathogen of honey bees. To provide tools for understanding the dispersal history of this pathogen, strain differences in virulence, and host,pathogen interactions, we used the draft genome assembly of A. apis to develop microsatellite loci for this species. We present testing results for 25 scorable loci revealing two to eight alleles per locus in a survey of Maryland isolates of this fungus. [source] | ||||||||||||||||||||||||||||||||||