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Abstract

Amoebiasis is the third worldwide disease due to a parasite. The causative agent of this disease, the unicellular eukaryote Entamoeba histolytica, causes dysentery and liver abscesses associated with inflammation and human cell death. During liver invasion, before entering the parenchyma, E. histolytica trophozoites are in contact with liver sinusoidal endothelial cells (LSEC). We present data characterizing human LSEC responses to interaction with E. histolytica and identifying amoebic factors involved in the process of cell death in this cell culture model potentially relevant for early steps of hepatic amoebiasis. E. histolytica interferes with host cell adhesion signalling and leads to diminished adhesion and target cell death. Contact with parasites induces disruption of actin stress fibers and focal adhesion complexes. We conclude that interference with LSEC signalling may result from amoeba-triggered changes in the mechanical forces in the vicinity of cells in contact with parasites, sensed and transmitted by focal adhesion complexes. The study highlights for the first time the potential role in the onset of hepatic amoebiasis of the loss of liver endothelium integrity by disturbance of focal adhesion function and adhesion signalling. Among the amoebic factors required for changed LSEC adherence properties we identified the Gal/GalNAC lectin, cysteine proteases and KERP1.

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El-Zahaby, H. M., Gullner, G. and Király, Z. (1995): Effects of powdery mildew infection of barley on the ascorbate-glutathione cycle and other antioxidants in different host-pathogen interactions. Phytopathol. 85 , 1225

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European Journal of Microbiology and Immunology
Authors: Markus M. Heimesaat, Gül Karadas, André Fischer, Ulf B. Göbel, Thomas Alter, Stefan Bereswill and Greta Gölz

Sporadic cases of gastroenteritis have been attributed to Arcobacter butzleri infection, but information about the underlying immunopathological mechanisms is scarce. We have recently shown that experimental A. butzleri infection induces intestinal, extraintestinal and systemic immune responses in gnotobiotic IL-10−/− mice. The aim of the present study was to investigate the immunopathological role of Toll-like Receptor-4, the receptor for lipopolysaccharide and lipooligosaccharide of Gram-negative bacteria, during murine A. butzleri infection. To address this, gnotobiotic IL-10−/− mice lacking TLR-4 were generated by broadspectrum antibiotic treatment and perorally infected with two different A. butzleri strains isolated from a patient (CCUG 30485) or fresh chicken meat (C1), respectively. Bacteria of either strain stably colonized the ilea of mice irrespective of their genotype at days 6 and 16 postinfection. As compared to IL-10−/− control animals, TLR-4−/− IL-10−/− mice were protected from A. butzleri-induced ileal apoptosis, from ileal influx of adaptive immune cells including T lymphocytes, regulatory T-cells and B lymphocytes, and from increased ileal IFN secretion. Given that TLR-4-signaling is essential for A. butzleri-induced intestinal inflammation, we conclude that bacterial lipooligosaccharide or lipopolysaccharide compounds aggravate intestinal inflammation and may thus represent major virulence factors of Arcobacter. Future studies need to further unravel the molecular mechanisms of TLR-4-mediated A. butzleri-host interactions.

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The octapeptide NAP is well known for its neuroprotective properties. We here investigated whether NAP treatment could alleviate pro-inflammatory immune responses during experimental subacute ileitis. To address this, mice with a human gut microbiota were perorally infected with one cyst of Toxoplasma gondii (day 0) and subjected to intraperitoneal synthetic NAP treatment from day 1 until day 8 postinfection (p.i.). Whereas placebo (PLC) control animals displayed subacute ileitis at day 9 p.i., NAP-treated mice exhibited less pronounced pro-inflammatory immune responses as indicated by lower numbers of intestinal mucosal T and B lymphocytes and lower interferon (IFN)-γ concentrations in mesenteric lymph nodes. The NAP-induced anti-inflammatory effects were not restricted to the intestinal tract but could also be observed in extra-intestinal including systemic compartments, given that pro-inflammatory cytokines were lower in liver, kidney, and lung following NAP as compared to PLC application, whereas at day 9 p.i., colonic and serum interleukin (IL)-10 concentrations were higher in the former as compared to the latter. Remarkably, probiotic commensal bifidobacterial loads were higher in the ileal lumen of NAP as compared to PLC-treated mice with ileitis. Our findings thus further support that NAP might be regarded as future treatment option directed against intestinal inflammation.

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A F. oxysporum f. sp. dianthi strain, transformed with genes coding for fluorescent proteins (GFP or DsRedFP) as markers, was used to study the first host/pathogen interaction on carnation roots. The transformants’ mycelium observed under fluorescent light displayed a high expression of GFP and DsRedFP as a bright green or red cytoplasmic fluorescence. The root apparatus of a partially resistant cultivar of carnation was artificially inoculated by stable transformants and local colonization of plant tissues was monitored by means of fluorescence microscopy. A GFP transformed strain of F. oxysporum f. sp. dianthi allowed to follow first colonization steps on and within host root tissues. Implication of this research in studying resistance processes in carnation is discussed.

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Septoria tritici blotch (STB) caused by the fungus Mycosphaerella graminicola, is one of the most important foliar diseases of wheat (T. aestivum spp., aestivum L.). Various practices such as crop rotation, application of fungicides, and deployment of genetic resistance have been utilised to control this disease and subsequently reduce yield losses. During the last 20 years, significant progress has been made in understanding host-pathogen interaction, inheritance of STB resistance, localisation of loci controlling STB resistance and identification of molecular markers associated with STB resistance in common wheat. We review the progress made on various aspects of molecular breeding for STB resistance especially on mapping and validation of qualitative and quantitative trait loci in common wheat.

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Francisella tularensis is a Gram-negative bacterium, the causative agent of the zoonotic disease tularaemia. The bacterium has developed several extracellular and intracellular strategies to evade the hosts’ innate and adaptive immune responses. The aims of the study were to examine complement sensitivity of wild and attenuated F. tularensis ssp. holarctica strains in animal hosts of distinct sensitivity to the bacterium, to compare the complement-evading ability of wild strains of different phylogeographic background, and to examine the role of factor H in the host–pathogen interactions. Complement sensitivity assays were carried out on various F. tularensis ssp. holarctica wild strains and on the attenuated live vaccine strain (LVS) with sera of the highly sensitive house mouse (Mus musculus), the moderately sensitive European brown hare (Lepus europaeus) and the relatively resistant cattle (Bos taurus). Specific binding of complement regulator factor H to bacterial membrane proteins was examined by Western blot assays. All wild strains interacted with the hosts’ complement system and showed no significant differences in their survivability. The attenuated LVS was resistant to serum killing in mouse, but was lysed in the sera of hare and cattle. Direct binding of factor H to F. tularensis membrane proteins was not detected.

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The oil quality and yield of groundnut ( Arachis hypogaea L.) is mainly lessened by Puccinia arachidis Speg. For screening large number of genotypes to rust resistance under in vitro conditions, the present study was motivated to test and verify the reliability of certain pathogen related enzymes, alterations in protein expression level and isoenzymes, activated ahead of host pathogen interaction. Biparental segregants acquired through NCD 1 mating fashion from crosses, viz. TMV1×ICG1697 and VRI2×ICG1697 were artificially inoculated with rust pathogen. After rust infection in groundnut, the alterations in the activity of peroxidase (PO), polyphenol oxidase (PPO), ascorbic acid oxidase (AAO) and chitinase were studied at 80 and 90 days after sowing (DAS) both in susceptible and resistant segregants along with parents. Both susceptible and resistant segregants manifest increased activity of all of these three enzymes, the magnitude was higher in resistant segregants. The activity of ascorbic acid oxidase and chitinase were high at 90 DAS, while polyphenol oxidase and peroxidase exhibited maximum activity at 80 DAS. Four additional isoforms of PO and PPO and prominent expression of a 56 kDa protein were observed in resistant genotypes. The potential amount and activity of these enzymes were genetically determined and such changes in the quantity, isoenzyme and protein can be relied for screening rust tolerant genotypes in groundnut.

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Cereal Research Communications
Authors: P. Motallebi, S. Tonti, V. Niknam, H. Ebrahimzadeh, A. Pisi, P. Nipoti, M. Hashemi and A. Prodi

Fusarium culmorum is a soilborne fungal pathogen, agent of crown and root rot disease (FCRR), responsible of major economic losses in wheat plants. This host—pathogen interaction, following methyl jasmonate (MeJA) application at the beginning of the necrotrophic stage of infection, has not been previously studied at molecular level. In this study, using real-time quantitative PCR, the emerging role of MeJA in the basal resistance of two bread wheat cultivars against F. culmorum has been investigated. MeJA treatment was dispensed 6 hours after pathogen inoculation (6 hai) to detect the defense response at the beginning of the necrotrophic stage. The expression of phenylalanine ammonia-lyase (PAL), lipoxygenase (LOX), cytochrome P450 (CYP709C1) genes and of some pathogenesis related (PR) genes, including PR3, PR4 and PR9, was examined in both root and crown tissues of the susceptible wheat cultivar Falat and the tolerant cultivar Sumai3. The pathogen responsive defense genes were induced in both cultivars, with a higher level of induction in Sumai3 than in Falat. MeJA treatment reduced the symptoms in cv Falat, whereas no significant effects have been detected in cv Sumai3. In fact, MeJA treatment caused a striking difference in defense gene induction. The genetic change was present in root and crown tissues of both wheat cultivars, demonstrating a systemic signaling pathway. The chemically induced protection correlated with induction of the F. culmorum-responsive genes supports a possible role of jasmonate signaling in regulating basal resistance in wheat–F. culmorum interaction.

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Karnal bunt of wheat (Tilletia indica) is an important internationally quarantined disease from food security point of view. For understanding host specificity and host-pathogen interaction, putative pathogenicity-related genes were analysed in Tilletia indica in response to host factor at different time points. Highest radial mycelia growth (3.4 cm) was recorded in media amended with susceptible host factor followed by resistant host (2.6 cm) and control (2.0 cm) at 30 days after incubation significantly. Fourteen homologous sequences of putative pathogenicity-related genes, viz. TiPmk1, TiKss1, TiHog1, TiHsp70, TiKpp2, TiCts1, TiHos2, TiChs1, TiPrf1, TiSid1, TiSsp1, TiSte20, TiUbc4 and TiUkc1, were identified in T. indica by in silico analysis. Some of the pathogenicity-related genes were highly expressed significantly in T. indica in response to susceptible host factor as compared to resistant host factor. TiPmk1, TiHog1, TiKss1 were found highly upregulated up to 26-fold (3 days), 20-fold (3 days) and 18-fold (4 days), respectively, significantly in presence of susceptible host factor. The TiCts1 and TiChs1 showed transcripts up to 26-fold (4 days) and 20-fold (3 days) in the presence of susceptible host factor. Further, the TiUbc4 and TiUkc1 were found upregulated up to 20-fold and 7-fold at 8 days and 3 days post incubation. This study provided the insight on expression of putative pathogenicity-related genes in T. indica which will help in understanding the infection mechanism and basis for further functional genomics approach.

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