Elicitation of Epithelial Cell-Derived Immune Effectors by Outer Membrane Vesicles of Nontypeable Haemophilus influenzae

Sharpe, Samantha W.; Kuehn, Meta J.; Mason, Kevin M.

doi:10.1128/iai.05332-11

Cited by 108 publications

(125 citation statements)

References 58 publications

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“…Previous studies of NTHI invasion of human alveolar epithelial cells have generated differing observations about the role of lipid rafts (20,22). Additionally, internalization of NTHI outer membrane vesicles (OMVs) by human pharyngeal epithelial cells in vitro was shown to be lipid raft dependent, although it is conceivable that OMVs would have different properties than whole bacteria (8). Such variability illustrates the importance of controls and of varied model system components, such as bacterial strains, host cell types, and experimental conditions, in studies examining internalization and trafficking pathways.…”

Section: Discussionmentioning

confidence: 99%

“…Colonization and the transition from commensal to opportunistic pathogen require NTHI to resist host innate immune defenses, including nutrient sequestration, mucociliary clearance, antimicrobial peptides, secretory IgA1, and phagocytosis by immune cells or by epithelial cells. Bacterial counterresistance mechanisms under investigation include adhesins, antimicrobial peptide degradation, IgA1 protease, biofilm production, modification of surface-exposed lipooligosaccharide moieties, production of outer membrane vesicles (OMVs), and others (3)(4)(5)(6)(7)(8)(9)(10)(11)(12). Understanding these factors will help identify targets for therapeutic intervention, as NTHI infections induce acquired immunity consisting largely of strain-specific bactericidal antibodies that afford little or no crossprotection against newly acquired strains, given the high degree of antigenic heterogeneity among strains.…”

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confidence: 99%

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Internalization and Trafficking of Nontypeable Haemophilus influenzae in Human Respiratory Epithelial Cells and Roles of IgA1 Proteases for Optimal Invasion and Persistence

2014

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Nontypeable Haemophilus influenzae (NTHI) is a leading cause of opportunistic infections of the respiratory tract in children and adults. Although considered an extracellular pathogen, NTHI has been observed repeatedly within and between cells of the human respiratory tract, and these observations have been correlated to symptomatic infection. These findings are intriguing in light of the knowledge that NTHI persists in the respiratory tract despite antibiotic therapy and the development of bactericidal antibodies. We hypothesized that intracellular NTHI avoids, escapes, or neutralizes the endolysosomal pathway and persists within human respiratory epithelial cells and that human IgA1 proteases are required for optimal internalization and persistence of NTHI. Virtually all strains encode a human IgA1 protease gene, igaA, and we previously characterized a novel human IgA1 protease gene, igaB, that is associated with disease-causing strains and is homologous to the IgA1 protease that is unique to pathogenic Neisseria spp. Here, we show that NTHI invades human bronchial epithelial cells in vitro in a lipid raft-independent manner, is subsequently trafficked via the endolysosomal pathway, and is killed in lysosomes after variable durations of persistence. IgaA is required for optimal invasion. IgaB appears to play little or no role in adherence or invasion but is required for optimal intracellular persistence of NTHI. IgaB cleaves lysosome-associated membrane protein 1 (LAMP1) at pHs characteristic of the plasma membrane, early endosome, late endosome, and lysosome. However, neither IgA1 protease inhibits acidification of intracellular vesicles containing NTHI. NTHI IgA1 proteases play important but different roles in NTHI invasion and trafficking in respiratory epithelial cells. Nontypeable Haemophilus influenzae (NTHI) is a Gram-negative, human-exclusive commensal bacterium of the nasopharynx and is a leading cause of opportunistic infections in the upper and lower respiratory tracts, including otitis media, sinusitis, conjunctivitis, community-acquired pneumonia, and exacerbations of chronic obstructive pulmonary disease (COPD) and of cystic fibrosis (1, 2).When a new strain of NTHI is acquired, the outcome depends on a variety of dynamic host and bacterial factors. Colonization and the transition from commensal to opportunistic pathogen require NTHI to resist host innate immune defenses, including nutrient sequestration, mucociliary clearance, antimicrobial peptides, secretory IgA1, and phagocytosis by immune cells or by epithelial cells. Bacterial counterresistance mechanisms under investigation include adhesins, antimicrobial peptide degradation, IgA1 protease, biofilm production, modification of surface-exposed lipooligosaccharide moieties, production of outer membrane vesicles (OMVs), and others (3-12). Understanding these factors will help identify targets for therapeutic intervention, as NTHI infections induce acquired immunity consisting largely of strain-specific bactericidal antibodies that afford littl...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Internalization and Trafficking of Nontypeable Haemophilus influenzae in Human Respiratory Epithelial Cells and Roles of IgA1 Proteases for Optimal Invasion and Persistence

2014

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“…Unlike the traditional, highly characterized type I to VI secretion systems, OMVs have the capacity to transport a mixture of soluble and insoluble material, which may be advantageous to the bacteria by protecting their cargo from proteases or by allowing for the assembly of multivalent complexes. Once released from bacteria, the vesicles are free to interact with the host, with considerable evidence that OMVs can be internalized into host cells (9,16,31) and have a role in modulating the host immune response (4,49,54,61).…”

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confidence: 99%

Biogenesis of Outer Membrane Vesicles in Serratia marcescens Is Thermoregulated and Can Be Induced by Activation of the Rcs Phosphorelay System

et al. 2012

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Outer membrane vesicles (OMVs) have been identified in a wide range of bacteria, yet little is known of their biogenesis. It has been proposed that OMVs can act as long-range toxin delivery vectors and as a novel stress response. We have found that the formation of OMVs in the Gram-negative opportunistic pathogen Serratia marcescens is thermoregulated, with a significant amount of OMVs produced at 22 or 30°C and negligible quantities formed at 37°C under laboratory conditions. Inactivation of the synthesis of the enterobacterial common antigen (ECA) resulted in a hypervesiculation phenotype, supporting the hypothesis that OMVs are produced in response to stress. We demonstrate that the phenotype can be reversed to wild-type (WT) levels upon the loss of the Rcs phosphorelay response regulator RcsB, but not RcsA, suggesting a role for the Rcs phosphorelay in the production of OMVs. MS fingerprinting of the OMVs provided evidence of cargo selection within wild-type cells, suggesting a possible role for Serratia OMVs in toxin delivery. In addition, OMV-associated cargo proved toxic upon injection into the haemocoel of Galleria mellonella larvae. These experiments demonstrate that OMVs are the result of a regulated process in Serratia and suggest that OMVs could play a role in virulence.

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“…The contribution of outer membrane vesicles to the magnitude of cytokine elicitation was determined by further clarification of the conditioned medium to remove the outer membrane vesicles by ultracentrifugation at 38,000 ϫ g for 1 h as previously described (38).…”

Section: Methodsmentioning

confidence: 99%

Association of O-Antigen Serotype with the Magnitude of Initial Systemic Cytokine Responses and Persistence in the Urinary Tract

et al. 2016

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Urinary tract infection (UTI) is one of the most common ailments requiring both short-term and prophylactic antibiotic therapies. Progression of infection from the bladder to the kidney is associated with more severe clinical symptoms (e.g., fever and vomiting) as well as with dangerous disease sequelae (e.g., renal scaring and sepsis). Host-pathogen interactions that promote bacterial ascent to the kidney are not completely understood. Prior studies indicate that the magnitude of proinflammatory cytokine elicitation in vitro by clinical isolates of uropathogenic Escherichia coli (UPEC) inversely correlates with the severity of clinical disease. Therefore, we hypothesize that the magnitude of initial proinflammatory responses during infection defines the course and severity of disease. Clinical UPEC isolates obtained from patients with a nonfebrile UTI elicited high systemic proinflammatory responses early during experimental UTI in a murine model and were attenuated in bladder and kidney persistence. Conversely, UPEC isolates obtained from patients with febrile UTI elicited low systemic proinflammatory responses early during experimental UTI and exhibited prolonged persistence in the bladder and kidney. Soluble factors in the supernatant from saturated cultures as well as the lipopolysaccharide (LPS) serotype correlated with the magnitude of proinflammatory responses in vitro. Our data suggest that the structure of the O-antigen sugar moiety of the LPS may determine the strength of cytokine induction by epithelial cells. Moreover, the course and severity of disease appear to be the consequence of the magnitude of initial cytokines produced by the bladder epithelium during infection. IMPORTANCEThe specific host-pathogen interactions that determine the extent and course of disease are not completely understood. Our studies demonstrate that modest changes in the magnitude of cytokine production observed using in vitro models of infection translate into significant ramifications for bacterial persistence and disease severity. While many studies have demonstrated that modifications of the LPS lipid A moiety modulate the extent of Toll-like receptor 4 (TLR4) activation, our studies implicate the O-antigen sugar moiety as another potential rheostat for the modulation of proinflammatory cytokine production. The plasticity of the Escherichia coli genome has led to the evolution of strains that can serve as keystone commensal organisms in the microbiota as well as to the development of multiple virulent pathotypes that cause both intestinal and extraintestinal infections. Comparison of the genetic content of over 180 strains has revealed that the core E. coli genome is composed of about 1,700 genes, with an additional pangenome of over 16,000 genes (1). It has become increasingly apparent that the plasticity of the E. coli genome allows acquisition of virulence traits from diverse genetic origins and, as such, the potential to attain the same phenotypic trait using different mechanisms (2). Given this vast variat...

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Elicitation of Epithelial Cell-Derived Immune Effectors by Outer Membrane Vesicles of Nontypeable Haemophilus influenzae

Cited by 108 publications

References 58 publications

Internalization and Trafficking of Nontypeable Haemophilus influenzae in Human Respiratory Epithelial Cells and Roles of IgA1 Proteases for Optimal Invasion and Persistence

Internalization and Trafficking of Nontypeable Haemophilus influenzae in Human Respiratory Epithelial Cells and Roles of IgA1 Proteases for Optimal Invasion and Persistence

Biogenesis of Outer Membrane Vesicles in Serratia marcescens Is Thermoregulated and Can Be Induced by Activation of the Rcs Phosphorelay System

Association of O-Antigen Serotype with the Magnitude of Initial Systemic Cytokine Responses and Persistence in the Urinary Tract

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