Exposure of Salmonella enterica Serovar Typhimurium to a Protective Monoclonal IgA Triggers Exopolysaccharide Production via a Diguanylate Cyclase-Dependent Pathway

Amarasinghe, Jayaleka J.; D'Hondt, Rebecca; Waters, Christopher M.; Mantis, Nicholas J.

doi:10.1128/iai.00813-12

Cited by 42 publications

(54 citation statements)

References 81 publications

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“…While speculative at this stage, the results presented here are reminiscent of studies we have conducted with S. Typhimurium in which a monoclonal IgA (Sal4) specific for the O antigen is sufficient to paralyze the bacterium within a matter of minutes (23). Sal4 also affects type 3 secretion system (T3SS) activity, membrane potential, and permeability, as well as exopolysaccharide production (21,24). Moreover, the association of Sal4 with the S. Typhimurium O antigen induces distinct ultrastructural changes in the bacterium's surface morphology, including wrinkles and blebs that are nearly identical to those observed on the surface of V. cholerae following 2D6 treatment (20).…”

Section: Discussionmentioning

confidence: 79%

“…There is emerging evidence to suggest that protective anti-LPS IgA antibodies may have direct effects on microbial virulence, independent of agglutination (20)(21)(22)(23)(24). In the case of V. cholerae, Bishop and Camilli demonstrated using dark-field microscopy that polyclonal anti-LPS IgA antibodies inhibit V. cholerae motility in vitro, an observation that has been confirmed by others (13,14).…”

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confidence: 59%

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Rapid Effects of a Protective O-Polysaccharide-Specific Monoclonal IgA on Vibrio cholerae Agglutination, Motility, and Surface Morphology

2015

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b2D6 is a dimeric monoclonal immunoglobulin A (IgA) specific for the nonreducing terminal residue of Ogawa O-polysaccharide (OPS) of Vibrio cholerae. It was previously demonstrated that 2D6 IgA is sufficient to passively protect suckling mice from oral challenge with virulent V. cholerae O395. In this study, we sought to define the mechanism by which 2D6 IgA antibody protects the intestinal epithelium from V. cholerae infection. In a mouse ligated-ileal-loop assay, 2D6 IgA promoted V. cholerae agglutination in the intestinal lumen and limited the ability of the bacteria to associate with the epithelium, particularly within the crypt regions. In vitro fluorescence digital video microscopy analysis of antibody-treated V. cholerae in liquid medium revealed that 2D6 IgA not only induced the rapid (5-to 10-min) onset of agglutination but was an equally potent inhibitor of bacterial motility. Scanning electron microscopy showed that 2D6 IgA promoted flagellum-flagellum cross-linking, as well as flagellar entanglement with bacterial bodies, suggesting that motility arrest may be a consequence of flagellar tethering. However, monovalent 2D6 Fab fragments also inhibited V. cholerae motility, demonstrating that antibody-mediated agglutination and motility arrest are separate phenomena. While 2D6 IgA is neither bactericidal nor bacteriostatic, exposure of V. cholerae to 2D6 IgA (or Fab fragments) resulted in a 5-fold increase in surface-associated blebs, as well an onset of a wrinkled surface morphotype. We propose that the protective immunity conferred by 2D6 IgA is the result of multifactorial effects on V. cholerae, including agglutination, motility arrest, and possibly outer membrane stress. C holera is a life-threatening disease that remains endemic in many parts of the world (1-3). The etiological agent of cholera, Vibrio cholerae, is a noninvasive, Gram-negative bacterium that is acquired by humans via the fecal-oral route. Following ingestion, V. cholerae colonizes the mucosal surfaces of the small intestines, a process that is facilitated by the bacterium's single polar flagellum (4-7). Adherence to the epithelial surface requires expression of the toxin-coregulated pilus (TCP), in addition to other virulence factors (8), most notably, a potent ADP-ribosylating toxin known as cholera toxin (CT). CT disrupts chloride secretion within intestinal epithelial cells, inducing profuse water and electrolyte secretion and ultimately resulting in the hallmark "rice water diarrhea" associated with cholera. Cholera outbreaks frequently occur when water sanitation is disrupted, either following natural disasters or seasonally in areas where V. cholerae is endemic (9). The recent cholera outbreak in Haiti following the 2010 earthquake highlighted the ongoing potential of V. cholerae to cause mass causalities, as it resulted in more than half a million infected individuals and more than 7,000 deaths (10). Due to the rapid onset of symptoms and limited treatment options, control of cholera in many parts of the globe, particularly...

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Section: Discussionmentioning

confidence: 79%

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confidence: 59%

Rapid Effects of a Protective O-Polysaccharide-Specific Monoclonal IgA on Vibrio cholerae Agglutination, Motility, and Surface Morphology

2015

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“…The intracellular level of c-di-GMP was below the level of detection in the WT strain Ea1189, suggesting that under the conditions we examined, the levels of this molecule are relatively low in E. amylovora compared with those in other bacteria. For reference, we were able to detect and quantify c-di-GMP levels in a number of other bacterial species, including but not limited to V. cholerae, Yersinia pestis, Salmonella enterica serovar Typhimurium, and Clostridium difficile (36,(60)(61)(62)(63).…”

Section: Discussionmentioning

confidence: 99%

Cyclic Di-GMP Modulates the Disease Progression of Erwinia amylovora

et al. 2013

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The second messenger cyclic di-GMP (c-di-GMP) is a nearly ubiquitous intracellular signal molecule known to regulate various cellular processes, including biofilm formation, motility, and virulence. The intracellular concentration of c-di-GMP is inversely governed by diguanylate cyclase (DGC) enzymes and phosphodiesterase (PDE) enzymes, which synthesize and degrade c-di-GMP, respectively. The role of c-di-GMP in the plant pathogen and causal agent of fire blight disease Erwinia amylovora has not been studied previously. Here we demonstrate that three of the five predicted DGC genes in E. amylovora (edc genes, for Erwinia diguanylate cyclase), edcA, edcC, and edcE, are active diguanylate cyclases. We show that c-di-GMP positively regulates the secretion of the main exopolysaccharide in E. amylovora, amylovoran, leading to increased biofilm formation, and negatively regulates flagellar swimming motility. Although amylovoran secretion and biofilm formation are important for the colonization of plant xylem tissues and the development of systemic infections, deletion of the two biofilm-promoting DGCs increased tissue necrosis in an immature-pear infection assay and an apple shoot infection model, suggesting that c-di-GMP negatively regulates virulence. In addition, c-di-GMP inhibited the expression of hrpA, a gene encoding the major structural component of the type III secretion pilus. Our results are the first to describe a role for c-di-GMP in E. amylovora and suggest that downregulation of motility and type III secretion by c-di-GMP during infection plays a key role in the coordination of pathogenesis. Erwinia amylovora is the causal agent of fire blight and a devastating phytopathogen that infects plant species of the family Rosaceae, most notably apple and pear trees (1). E. amylovora can infect flowers, fruits, actively growing shoots, and rootstock crowns (2). During the primary infection via the flower (1), E. amylovora cells multiply rapidly on the stigma. Motility and free moisture are important factors in the subsequent dissemination of cells down the outside of the stigma to nectarthodes, which provide entry into the plant (3-5).Following flower infection, E. amylovora cells spread systemically through host vascular tissues and cortical parenchyma. The wilting symptoms of fire blight are the result of bacterial invasion, the secretion of extracellular polysaccharide (EPS), and the formation of biofilms within host xylem that plug these tubes, restricting water flow (6, 7). E. amylovora secretes two distinct EPSs, amylovoran and levan, both of which contribute to plant infection (6). Amylovoran is an acidic polysaccharide composed of repeating units of galactose and glucuronic acid (8-10), while levan is a homopolymer of fructose residues synthesized from sucrose by the secreted enzyme levansucrase (11). Biofilm formation by E. amylovora is required for effective colonization of host xylem tissues, the exit of pathogen cells from infected leaves into host stems, and systemic spread within trees (6, 7). The...

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“…However, it is also possible that I2 was present when I1 was sampled and that the two SNPs were independent mutational changes. YihV plays a role in O-antigen capsule assembly and translocation and biofilm formation (24,25). However, we did not test whether the SNPs observed in yihV affected capsule production and biofilm formation.…”

Section: Resultsmentioning

confidence: 95%

Genomic Variability of Serial Human Isolates of Salmonella enterica Serovar Typhimurium Associated with Prolonged Carriage

et al. 2015

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c Salmonella enterica serovar Typhimurium is an important foodborne human pathogen that often causes self-limiting but severe gastroenteritis. Prolonged excretion of S. Typhimurium after the infection can lead to secondary transmissions. However, little is known about within-host genomic variation in bacteria associated with asymptomatic shedding. Genomes of 35 longitudinal isolates of S. Typhimurium recovered from 11 patients (children and adults) with culture-confirmed gastroenteritis were sequenced. There were three or four isolates obtained from each patient. Single nucleotide polymorphisms (SNPs) were analyzed in these isolates, which were recovered between 1 and 279 days after the initial diagnosis. Limited genomic variation (5 SNPs or fewer) was associated with short-and long-term carriage of S. Typhimurium. None of the isolates was shown to be due to reinfection. SNPs occurred randomly, and the majority of the SNPs were nonsynonymous. Two nonsense mutations were observed. A nonsense mutation in flhC rendered the isolate nonmotile, whereas the significance of a nonsense mutation in yihV is unknown. The estimated mutation rate is 1.49 ؋ 10 ؊6 substitution per site per year. S. Typhimurium isolates excreted in stools following acute gastroenteritis in children and adults demonstrated limited genomic variability over time, regardless of the duration of carriage. These findings have important implications for the detection of possible transmission events suspected by public health genomic surveillance of S. Typhimurium infections. Nontyphoid Salmonella (NTS) infections generally result in a short-term, self-limiting gastroenteritis. However, NTS can be excreted continually and asymptomatically in stools for many weeks, even after the initial diarrheal episode has been resolved. Children are the more common carriers, especially children under the age of 3 years (1, 2). Fecal shedding of NTS after an intestinal infection can last for up to 4 weeks in adults and 7 weeks in children (3). In a very small proportion of cases, carriage can last for a year after the initial onset of the disease (3). Carriers excrete large numbers of bacteria in their feces and can facilitate the transmission of Salmonella to other hosts by contaminating water and food sources. The persistence of fecal shedding in asymptomatic patients can have a duration similar to that for patients with clinical disease (4). Antibiotic treatment of NTS disease is rarely indicated, as it does not assist in clearance of infection but may increase the duration of asymptomatic shedding (4).Salmonella enterica serovar Typhimurium is one of the leading causes of NTS gastroenteritis in humans in Australia and other countries. Salmonellosis is a notifiable disease in all Australian states and territories. In the state of New South Wales (NSW), the notification rate has been around 50 cases per 100,000 population (5). Sequencing of S. Typhimurium genomes or analyses of tandem repeats within the genome have increasingly been employed for tracking community ou...

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Exposure of Salmonella enterica Serovar Typhimurium to a Protective Monoclonal IgA Triggers Exopolysaccharide Production via a Diguanylate Cyclase-Dependent Pathway

Cited by 42 publications

References 81 publications

Rapid Effects of a Protective O-Polysaccharide-Specific Monoclonal IgA on Vibrio cholerae Agglutination, Motility, and Surface Morphology

Rapid Effects of a Protective O-Polysaccharide-Specific Monoclonal IgA on Vibrio cholerae Agglutination, Motility, and Surface Morphology

Cyclic Di-GMP Modulates the Disease Progression of Erwinia amylovora

Genomic Variability of Serial Human Isolates of Salmonella enterica Serovar Typhimurium Associated with Prolonged Carriage

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