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Many Pathogens (many + pathogen)
Selected AbstractsVirulence evolution via host exploitation and toxin production in spore-producing pathogensECOLOGY LETTERS, Issue 4 2002Troy Day Many pathogens produce resilient free-living propagules that allow their dissemination in the absence of direct contact between susceptible and infected hosts. One might expect pathogens capable of producing such long-lived propagules to evolve high levels of virulence because their reproductive success is de-coupled from the survival of their host. Despite some comparative data supporting this prediction, theory has questioned its general validity. I present theoretical results that incorporate two transmission routes neglected by previous theory: death-mediated propagule production and direct host-host transmission. This theory predicts that spore-producing pathogens should evolve high levels of virulence under quite broad conditions. Moreover, a novel prediction of this theory is that the production of propagules can generate selection for the evolution of pathogen characteristics such as toxins whose sole function is to kill the host. This latter result reveals an unanticipated mechanism through which virulence is expected to evolve in spore-producing pathogens. [source] Pathogen evasion strategies for the major histocompatibility complex class I assembly pathwayIMMUNOLOGY, Issue 1 2008Antony N. Antoniou Summary Major histocompatibility complex (MHC) class I molecules bind and present short antigenic peptides from endogenously or exogenously derived sources to CD8+ cytotoxic T lymphocytes (CTL), with recognition of a foreign peptide normally targeting the cell for lysis. It is generally thought that the high level of MHC polymorphism, which is concentrated mostly within the peptide-binding groove, is driven by the ,evolutionary arms race' against pathogens. Many pathogens have developed novel and intriguing mechanisms for evading the continuous sampling of the intracellular and intercellular environments by MHC molecules, none more so than viruses. The characterization of immunoevasion mechanisms has improved our understanding of MHC biology. This review will highlight our current understanding of the MHC class I biosynthetic pathway and how it has been exploited by pathogens, especially viruses, to potentially evade CTL recognition. [source] Evasion of macrophage scavenger receptor A-mediated recognition by pathogenic streptococciEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 11 2008Thomas Areschoug Abstract PRR recognize conserved structures on pathogenic microbes and are important for the defense against invading microorganisms. However, accumulating evidence indicates that many pathogens have evolved mechanisms to avoid recognition by PRR. One type of PRR is the macrophage scavenger receptor A (SR-A), which has been shown to play an important role in recognition and non-opsonic phagocytosis of pathogenic bacteria. The bacterial ligands for SR-A have been suggested to be LPS or lipoteichoic acid. Here, we use murine bone marrow-derived macrophages to analyze the role of SR-A in non-opsonic phagocytosis of two major Gram-positive pathogens, Streptococcus agalactiae (group B streptococcus; GBS) and Streptococcus pyogenes. We show that the polysaccharide capsule of GBS and the surface M protein of S. pyogenes, two important virulence factors, prevent SR-A-mediated non-opsonic phagocytosis of streptococci. The sialic acid moiety of the GBS capsule was crucial for its ability to prevent recognition by SR-A. Moreover, we show that a ligand on GBS recognized by SR-A in the absence of capsule is the surface lipoprotein Blr. These findings represent the first example of a microbial strategy to prevent recognition by SR-A and suggest that bacterial surface proteins may be of importance as ligands for SR-A. [source] A Quantitative Polymerase Chain Reaction Assay for the Detection of Polyscytalum pustulans, the Cause of Skin Spot Disease of PotatoJOURNAL OF PHYTOPATHOLOGY, Issue 3 2009A. K. Lees Abstract Skin spot disease of potato caused by the pathogen Polyscytalum pustulans is likely to become more important with the withdrawal of 2-aminobutane as a fungicide, and new methods of control will need to be found. As part of a disease control strategy, it will be necessary to study the disease in more detail, to utilize host resistance and to identify stocks where problems are likely to arise. Existing methods for the detection and quantification of P. pustulans are time-consuming and require specific expertise. Real-time PCR assays have been developed for many pathogens of potato and have subsequently been used as tools for the study of the epidemiology and control of disease. The development of a real-time PCR assay for the detection and quantification of P. pustulans is described. The specificity of the assay was demonstrated and detection was shown to be reliable at levels as low as 20,250 fg/,l DNA, (equivalent to 60,680 pg DNA/g) in soil and on symptomless tubers at attogram (ag) levels. These values are in line with previously developed tests. [source] | |||||||||||||