BACKGROUND: The human microflora is known to be extremely complex, yet most pathogenesis research is conducted in mono-species models of infection. Consequently, it remains unclear whether the level of complexity of a host's indigenous flora can affect the virulence potential of pathogenic species. Furthermore, it remains unclear whether the colonization ...

BACKGROUND: Caspase-12 functions as an antiinflammatory enzyme inhibiting caspase-1 and the NOD2/RIP2 pathways. Due to increased susceptibility to sepsis in individuals with functional caspase-12, an early-stop mutation leading to the loss of caspase-12 has replaced the ancient genotype in Eurasia and a significant proportion of individuals from African populations. In ...

Staphylococcus aureus (SA) is a leading cause of a diverse spectrum of bacterial diseases, including abscesses. Nitric oxide (NO) is a critical component of the natural host defense against pathogens such as SA, but its therapeutic applications have been limited by a lack of effective delivery options. We tested the ...

Successful immune defense is a complex balancing act. In order to protect a host against invasion by harmful pathogens, an immune response must be rapid and vigorous, and must eliminate foreign invaders before their populations grow beyond control. That same immune response, however, must be selective enough to recognize and ...

The pathogen virulence is traditionally thought to co-evolve as a result of reciprocal selection with its host organism. In natural communities, pathogens and hosts are typically embedded within a web of interactions with other species, which could affect indirectly the pathogen virulence and host immunity through trade-offs. Here we show ...

Iron is an essential micronutrient for both microbial pathogens and their mammalian hosts. Changes in iron availability and distribution have significant effects on pathogen virulence and on the immune response to infection. Recent advances in our understanding of the molecular regulation of iron metabolism have shed new light on how ...

The biologic mechanisms linking socioeconomic position and psychosocial factors to cardiovascular disease (CVD) are not well understood. Immune response to persistent pathogens may be one of these mechanisms. We analyzed cross-sectional data from the multi-ethnic study of atherosclerosis (N=999) composed of adults age 45-84. Log-binomial regression and ordinal logistic regression ...

Candida albicans is a common opportunistic pathogen of the human body and is the frequent causative agent of candidiasis. Typically, these infections are associated with the formation of biofilms on both host tissues and implanted biomaterials. As a result of the intrinsic resistance of C. albicans biofilms to most antifungal ...

The virulence of the pathogenic Yersinia species depends on a plasmid-encoded type III secretion system (T3SS) that transfers six Yersinia outer protein (Yop) effector proteins into the cytoplasm of eukaryotic cells, leading to disruption of host defence mechanisms. It is shown in this study that Yersinia pestis YscW, a protein ...

Plant immune responses to pathogens are often associated with enhanced production of reactive oxygen species (ROS), known as the oxidative burst, and with rapid hypersensitive host cell death (the hypersensitive response, HR) at sites of attempted infection. It is generally accepted that the oxidative burst acts as a promotive signal ...

Type I IFNs were discovered as the primary antiviral cytokines and are now known to serve critical functions in host defense against bacterial pathogens. Accordingly, established mediators of IFN antiviral activity may mediate previously unrecognized antibacterial functions. RNase-L is the terminal component of an RNA decay pathway that is an ...

BACKGROUND: An important layer of active defense in plant immunity is the detection of pathogen-associated molecular patterns (PAMPs) mediated by cell-surface receptors. For the establishment of disease, pathogens depend on the ability to overcome PAMP perception and disable plant signaling pathways activated in response to PAMPs. Pattern recognition receptors (PRRs) ...

Organisms evolve two routes to surviving infections-they can resist pathogen growth (resistance) and they can endure the pathogenesis of infection (tolerance). The sum of these two properties together defines the defensive capabilities of the host. Typically, studies of animal defenses focus on either understanding resistance or, to a lesser extent, ...

Members of the bacterial genus Francisella are highly virulent and infectious pathogens. New models to study Francisella pathogenesis in evolutionarily distinct species are needed to provide comparative insight, as the mechanisms of host resistance and pathogen virulence are not well understood. We took advantage of the recent discovery of a ...

Expression of capsular polysaccharide by bacterial pathogens is associated with increased resistance to host clearance mechanisms, in particular by evading opsonization and uptake by professional phagocytes. The potential for rapid progression of disease caused by encapsulated bacteria points to the importance of innate immunity at the mucosal surface where infection ...

Candida albicans infection is a significant cause of morbidity and mortality in immunocompromised patients. In vivo and in vitro models have been developed to study both the fungal and the mammalian immune responses. Phagocytic cells (i.e., macrophages) play a key role in innate immunity against C. albicans by capturing, killing ...

Human adenoviruses cause a significant number of acute respiratory, enteric and ocular infections, however they have also served as useful model systems for uncovering fundamental aspects of cell and molecular biology. In addition, replication-defective forms of adenovirus are being used in gene transfer and vaccine clinical trials. Over the past ...

Most, if not all, animals coexist with a complement of prokaryotic symbionts that confer a variety of physiologic benefits. In humans, the interaction between animal and bacterial cells is especially important in the gastrointestinal tract. Technical and conceptual advances have enabled rapid progress in characterizing the taxonomic composition, metabolic capacity, ...

The Echinococcus organisms, the cause of echinococcosis (hydatid disease), are parasitic helminths with life cycles involving a carnivorous definitive host (usually dog or fox) and an intermediate host (human, ungulate, or rodent). They are complex multicellular pathogens that, despite being under constant barrage by the immune system, are able to ...

Pseudomonas aeruginosa is an important opportunistic bacterial pathogen, causing infections of the respiratory and other organ systems in susceptible hosts. P. aeruginosa infection is initiated by adhesion to and invasion of mucosal epithelial cells. The failure of host defenses to eliminate P. aeruginosa from mucosal surfaces results in P. aeruginosa ...

OspF, OspG and IpaH(9.8) are type III secretion system (T3SS) effectors of Shigella flexneri that downregulate the host innate immune response. OspF modifies mitogen-activated protein kinase pathways and polymorphonuclear leucocyte transepithelial migration associated with Shigella invasion. OspF also localizes in the nucleus to mediate chromatin remodelling, resulting in reduced transcription ...

To develop intracellularly within phagocytes and cause chronic infection, Brucella must overcome different steps of the host immune responses. IFNgamma is a key mediator of the innate and adaptive responses produced during Brucella infection. Therefore, Brucella would control host defenses by impairing macrophage responses to IFNgamma. We first showed that ...

Haem oxygenase (HO)-1 is a cytoprotective enzyme that plays a critical role in defending the body against oxidant-induced injury during inflammatory processes. HO catalydes the degradation of haem to carbon monoxide (CO), biliverdin and ferrous iron. Biliverdin is converted to bilirubin, a potent endogenous antioxidant. CO has a number of ...

Adaptation to environmental conditions is key to fungal survival during infection of human hosts. Although the host immune system is often considered the primary obstacle to fungal colonization, invading fungi must also contend with extreme abiotic stresses. Recent work with human pathogenic fungi has uncovered systems for detecting and responding ...

Hypoxia is typical for most battlefields of host-pathogen interactions in the human host. While adaptation of human cells to low levels of oxygen has been well established, little information exists on mechanisms of hypoxic adaptation in microbial pathogens. Importantly, the impact of hypoxia on microbial infection, virulence and pathogenesis is ...

We studied the host specificity, interactions with plant immune systems, and virulence factors of the phytopathogenic Type III secretion system-carrying bacterium Pseudomonas syringae. In studying host specificity, we ran growth and pod assays using seventeen pathovars of P. syringae on kidney bean hosts. We tracked bacterial growth numbers over six ...

Herpesviruses have evolved numerous strategies to subvert host immune responses so they can coexist with their host species. These viruses 'co-opt' host genes for entry into host cells and then express immunomodulatory genes, including mimics of members of the tumour-necrosis factor (TNF) superfamily, that initiate and alter host-cell signalling pathways. ...

The genetic analysis of mechanisms of pathogen resistance in the nematode Caenorhabditis elegans has revealed a role for evolutionarily conserved signaling pathways that are required for innate immunity in a wide range of organisms, from worms to mammals. C. elegans represents one of the more simple host organisms in which ...

Anthrax toxins significantly contribute to anthrax disease pathogenesis, and mechanisms by which the toxins affect host cellular responses have been identified with purified toxins. However, the contribution of anthrax toxin proteins to dissemination, disease progression, and subsequent immunity after aerosol infection with spores has not been clearly elucidated. To better ...

Bartonella henselae (Bh) is a worldwide distributed zoonotic pathogen. Depending on the immune status of the infected individual this bacterium can cause a wide spectrum of clinical manifestations, ranging from cat scratch disease (CSD) to bacillary angiomatosis (BA) and bacillary peliosis (BP). BA and BP are characterized by tumor-like lesions ...

The voltage-dependent anion channel (VDAC) is a major outer mitochondrial membrane protein. It is well documented that VDAC plays an important role in apoptosis, a kind of programmed cell death, in mammalian systems. However, little is known about the role of the plant counterpart during the process of plant-specific cell ...

Abstract How does an animal host prevent intracellular symbionts getting out of hand? A new paper in BMC Biology provides evidence that the mutualism between a beetle and its bacterial endosymbiont could be mediated through the expression of host immune genes.

In many important human pathogens, such as Shigella and Salmonella spp., the bacterial type III secretion (T3S) apparatus is required to initiate inflammation via activation of caspase-1- or NF-kappaB-dependent genes. Using an ex vivo infection model, the goal of the present study was to determine whether the chlamydial T3S apparatus ...

A large number of the world's most widespread and problematic pathogens evade host immune responses by inducing strain-specific immunity to immunodominant epitopes with high mutation rates capable of altering antigenic profiles. The immune system appears to be decoyed into reacting to these immunodominant epitopes that offer little cross protection between ...

Gastrointestinal mucins produced by goblet cells comprise the main structural components of the mucus layer. Mucins play a critical role in the maintenance of mucosal homeostasis and are responsible for the differential effector and regulatory responses against a plethora of microorganisms, including commensals and pathogens. In this review, we present ...

Epithelial tissues facing the external environment are essential to combating microbial infection. In addition to providing a physical barrier, epithelial tissues mount chemical defenses to prevent invasion of internal tissues by pathogens. Here, we describe that the melanization reaction implicated in host defense is activated in the respiratory system, the ...

Cnidarian bleaching is a breakdown in the mutualistic symbiosis between host Cnidarians, such as reef building corals, and their unicellular photosynthetic dinoflagellate symbionts. Bleaching is caused by a variety of environmental stressors, most notably elevated temperatures associated with global climate change in conjunction with high solar radiation, and it is ...

Mucosal tissues such as the gastrointestinal tract are typically exposed to a tremendous number of microorganisms and many of them are potentially dangerous to the host. In contrast, the urogenital tract is rather infrequently colonized with bacterial organisms and also devoid of physical barriers as a multi-layered mucus or ciliated ...

Evaluation of: Ketavarapu JM, Rodriguez AR, Yu J et al.: Mast cells inhibit intramacrophage Francisella tularensis replication via contact and secreted products including IL-4. Proc. Natl Acad. Sci. USA 105(27), 9313-9318 (2008). The intracellular pathogen Francisella tularensis is a highly infectious organism that infects cells of the immune system. Mast ...

Some pathogens have evolved mechanisms to overcome host immune defenses by inhibiting host defense signaling pathways and suppressing the expression of host defense effectors. We present evidence that Pseudomonas aeruginosa is able to suppress the expression of a subset of immune defense genes in the animal host Caenorhabditis elegans by ...

In order to support healthy aquaculture, we developed assays to assess immune functions and their susceptibility to environmental conditions or toxicants. Flow cytometry allowed the rapid and quantitative analysis of oyster and lobster cell subpopulations and their functions (phagocytosis, peroxide production, natural killer cell-like activity and apoptosis). We demonstrated experimentally ...

Neisseria gonorrhoeae is a gram-negative diplococcus that in human beings produces gonorrhea. Much clinical evidence has led to the conclusion that gonococcus has important mechanisms to evade host immune functions; however, these mechanisms are only now beginning to be elucidated. In this study, we determined that the BALB/c mouse is ...

Several Borrelia burgdorferi genes induced under mammalian host conditions have been purported to be important in Lyme disease pathogenesis based on their binding to host structures. These genes include the dbpBA locus, whose products bind host decorin and glycosoaminoglycans. Recently, the dbpBA genes were reported to be involved in borrelial ...

Converging studies have shown that M1 and M2 macrophages are functionally polarized in response to microorganisms and host mediators. Gene expression profiling of macrophages reveals that various Gram-negative and Gram-positive bacteria induce the transcriptional activity of a "common host response," which includes genes belonging to the M1 program. However, excessive ...

RHO-like monomeric G-proteins of plants (ROPs, also called RACs), are involved in plant development and interaction with the environment. The barley (Hordeum vulgare) ROP protein HvRACB has been shown to be required for entry of the biotrophic powdery mildew fungus Blumeria graminis f.sp. hordei (Bgh) into living host cells. To ...

Chronic rhinosinusitis (CRS) has been defined as persistent symptomatic inflammation of the nasal and sinus mucosa resulting from the interaction of multiple host and environmental factors. Recent studies have implicated Alternaria fungi or toxigenic Staphylococcus aureus as critical agents in CRS pathogenesis. The emphasis on environmental agents in CRS etiology ...

Oomycete pathogens of plants and animals are related to marine algae and have evolved mechanisms to avoid or suppress host defences independently of other groups of pathogens, such as bacteria and fungi. They cause many destructive diseases affecting crops, forests and aquaculture. The development of genomic resources has led to ...

The plant apoplast constitutes a space for early recognition of potentially harmful non-self. Basal pathogen recognition operates via dynamic sensing of conserved microbial patterns by pattern recognition receptors or of elicitor-active molecules released from plant cell walls during infection. Recognition elicits defence reactions depending on cellular export via SNARE (soluble ...

Pantoea stewartii subsp. stewartii (Pnss) causes Stewart's bacterial wilt of sweet corn and leaf blight of maize. The pathogenicity of Pnss depends on synthesis of extracellular polysaccharide and an Hrp type III secretion system. WtsE, a type III secreted effector protein, is essential for the virulence of Pnss on corn. ...

Sarcoidosis continues to be a disease of research interest because of its complicated immune mechanisms and elusive etiology. So far, it has been established that granulomatous inflammation in sarcoidosis is predominantly a T-helper 1 immune response mediated by a complex network of lymphocytes, macrophages, and cytokines. The cause of progression ...