The chitin-binding protein GbpA of Vibrio cholerae has been recently described as a common adherence factor for chitin and intestinal surface. Using an isogenic in-frame gbpA deletion mutant, we first show that V. cholerae O1 El Tor interacts with mouse intestinal mucus quickly, using GbpA in a specific manner. The gbpA mutant strain showed a significant decrease in intestinal adherence, leading to less colonization and fluid accumulation in a mouse in vivo model. Purified recombinant GbpA (rGbpA) specifically bound to N-acetyl-D-glucosamine residues of intestinal mucin in a dose-dependent, saturable manner with a dissociation constant of 11.2 M. Histopathology results from infected mouse intestine indicated that GbpA binding resulted in a time-dependent increase in mucus secretion. We found that rGbpA increased the production of intestinal secretory mucins (MUC2, MUC3, and MUC5AC) in HT-29 cells through upregulation of corresponding genes. The upregulation of MUC2 and MUC5AC genes was dependent on NF-B nuclear translocation. Interestingly, mucin could also increase GbpA expression in V. cholerae in a dose-dependent manner. Thus, we propose that there is a coordinated interaction between GbpA and mucin to upregulate each other in a cooperative manner, leading to increased levels of expression of both of these interactive factors and ultimately allowing successful intestinal colonization and pathogenesis by V. cholerae.Vibrio cholerae is the causative agent of the potentially lethal disease cholera. V. cholerae strains belonging to serogroups O1 and O139 are mainly responsible for cholera epidemics, while strains of other serogroups may cause sporadic outbreaks of the disease. Although the O139 strain has evolved recently, V. cholerae O1 biotype El Tor strains have still been responsible for most of the epidemics in recent years (20,26). In order to cause the disease, V. cholerae must adhere to the intestinal mucus barrier (52). The ability of V. cholerae to adhere to animal cells has been studied before (26,42), and various adherence factors have been proposed, including the virulence-associated toxin-coregulated pilus (5), outer membrane proteins (26, 42), and lipopolysaccharide (LPS) (11). Attachment of V. cholerae to abiotic surfaces has also been recently described (50). However, there is still no information about the factor(s) responsible for initial adherence of the bacteria to the intestine and whether the host plays any role in aiding the colonization of the intestine by the bacteria.Vibrios are marine organisms that adhere to chitin in the environment (12, 33) and utilize chitin as the sole source of nitrogen and carbon by using a family of glycosyl hydrolases, called chitinases (21). Genome analysis of V. cholerae O1 El Tor has revealed the presence of seven such chitinase genes (7), some of which have been characterized (27,37). One of these genes is the putative chitinase gene with locus number VCA0811, the product of which has been recently identified as a common adhesion molecule for both chitinou...

Acute pulmonary infection by Streptococcus pneumoniae is characterized by high bacterial numbers in the lung, a robust alveolar influx of polymorphonuclear cells (PMNs) and a risk of systemic spread of the bacterium. We investigated host-mediators of S. pneumoniae-induced PMN migration and the role of inflammation in septicemia following pneumococcal lung infection. Hepoxilin A3 (HXA3) is a PMN chemoattractant and a metabolite of the 12-lipoxygenase (12-LOX) pathway. We observed that S. pneumoniae infection induced the production of 12-lipoxygenase in cultured pulmonary epithelium and in the lungs of infected mice. Inhibition of the 12- LOX pathway prevented pathogen-induced PMN transepithelial migration in vitro and dramatically reduced lung inflammation upon high-dose pulmonary challenge with S. pneumoniae in vivo, thus implicating HXA3 in pneumococcus-induced pulmonary inflammation. PMN basolateral-to-apical transmigration in vitro significantly increased apical-to-basolateral transepithelial migration of bacteria. Mice suppressed in the expression of 12-lipoxygenase exhibited little or no bacteremia and survived an otherwise lethal pulmonary challenge. Our data suggest that pneumococcal pulmonary inflammation is required for high level bacteremia and systemic infection, partly by disrupting lung epithelium through 12-LOX-dependent HXA3 production and subsequent PMN transepithelial migration.

Influenza A virus (IAV) claims ∼250,000-500,000 lives annually worldwide. Currently, there are a few in vitro models available to study IAV immunopathology. Monolayer cultures of cell lines and primary lung cells (two-dimensional [2D] cell culture) is the most commonly used tool, however, this system does not have the in vivo-like structure of the lung and immune responses to IAV as it lacks the three-dimensional (3D) tissue structure. To recapitulate the lung physiology in vitro, a system that contains multiple cell types within a 3D environment that allows cell movement and interaction would provide a critical tool. In this study, as a first step in designing a 3D-Human Tissue-Engineered Lung Model (3D-HTLM), we describe the 3D culture of primary human small airway epithelial cells (HSAEpCs) and determined the immunophenotype of this system in response to IAV infections. We constructed a 3D chitosan-collagen scaffold and cultured HSAEpCs on these scaffolds at air-liquid interface (ALI). These 3D cultures were compared with 2D-cultured HSAEpCs for viability, morphology, marker protein expression, and cell differentiation. Results showed that the 3D-cultured HSAEpCs at ALI yielded maximum viable cells and morphologically resembled the in vivo lower airway epithelium. There were also significant increases in aquaporin-5 and cytokeratin-14 expression for HSAEpCs cultured in 3D compared to 2D. The 3D culture system was used to study the infection of HSAEpCs with two major IAV strains, H1N1 and H3N2. The HSAEpCs showed distinct changes in marker protein expression, both at mRNA and protein levels, and the release of proinflammatory cytokines. This study is the first step in the development of the 3D-HTLM, which will have wide applicability in studying pulmonary pathophysiology and therapeutics development.

CS6 is a widely expressed colonization factor of enterotoxigenic Escherichia coli (ETEC). To date, CS6 has not been well characterized in its native state. Here, we purified CS6 for the first time from an ETEC clinical isolate. Purified CS6 was composed of two structural subunits, CssA and CssB, which were present in equal amounts and tightly linked through noncovalent, detergent-stable association. The CssA subunit was poorly immunogenic, whereas CssB was highly immunogenic. Although the predicted molecular mass of CssA is 15 kDa, the purified CssA has an effective molecular mass of 18.5 kDa due to fatty acid modification. When purified CS6 was screened for its ability to bind with different extracellular matrix proteins, fibronectin (Fn) was found to interact with CS6 as well as CssA in a dose-dependent and saturable manner. This interaction was inhibited both by a synthetic peptide corresponding to the C-terminal hydrophilic, surface-exposed region Enterotoxigenic Escherichia coli (ETEC) infection is the leading cause of infantile diarrhea in developing countries and an important etiologic agent for traveler's diarrhea. ETEC accounts for approximately 210 million diarrhea episodes and 380,000 deaths annually (35). Community-based studies conducted in developing countries with children younger than 5 years have shown that ETEC was the most frequently isolated enteropathogen (34, 35). As a cause of traveler's diarrhea, ETEC was found to be associated with 40 to 70% of the cases, with drastic outcome in terms of morbidity and economic consequences (34).In order to initiate pathogenesis, ETEC strains must adhere to the small intestine (14). This event is mediated by several proteinaceous surface antigens, collectively known as colonization factor antigens (CFAs) (6). To date, more than 25 distinct colonization factors have been identified, of which CS6 is the most prevalent in many countries (7,20,22). Many of the colonization factors have morphology of fimbriae or pili (14). However, the morphology of CS6 has not so far been defined. CS6 was assumed to be either a nonfimbrial or a short oligomeric assembly that does not protrude enough to be visualized under an electron microscope (17). Functional CS6 is expressed and transported to the bacterial surface in a chaperone-usher pathway. CssC and CssD are the chaperone and usher proteins, respectively, that help surface expression of the CS6 structural subunits, CssA and CssB (33).The role of CS6 in intestinal adherence has been demonstrated using CS6-expressing whole bacteria, but the receptor specificity is still unknown (11). A recent report has shown that when CssB is mutated, binding of bacteria to a colonic cell line (CaCo-2) is reduced slightly compared to that of the bacteria expressing whole CS6 (30).Here, we have purified CS6 to homogeneity from a clinical isolate of ETEC and separated its subunits (CssA and CssB) for the first time. We have characterized CS6 in its native form and demonstrated that fibronectin (Fn) is the interacting matrix for adherence....

The pulmonary epithelium is divided into upper, lower, and alveolar (or small) airway epithelia and acts as the mechanical and immunological barrier between the external environment and the underlying submucosa. Of these, the small airway epithelium is the principal area of gas exchange and has high immunological activity, making it a major area of cell biology, immunology, and pharmaceutical research. As animal models do not faithfully represent the human pulmonary system and ex vivo human lung samples have reliability and availability issues, cell lines, and primary cells are widely used as small airway epithelial models. In vitro, these cells are mostly cultured as monolayers (2-dimensional cultures), either media submerged or at air-liquid interface. However, these 2-dimensional cultures lack a three dimension-a scaffolding extracellular matrix, which establishes the intercellular network in the in vivo airway epithelium. Therefore, 3-dimensional cell culture is currently a major area of development, where cells are cultured in a matrix or are cultured in a manner that they develop ECM-like scaffolds between them, thus mimicking the in vivo phenotype more faithfully. This review focuses on the commonly used small airway epithelial cells, their 2-dimensional and 3-dimensional culture techniques, and their comparative phenotype when cultured under these systems.