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Persistent Bordetella bronchiseptica carriage is associated with broad phenotypic alterations of peripheral CD4+CD25+ T cells and differentially affects immune responses to secondary non-infectious and infectious stimuli in mice

ABSTRACT: The respiratory tract is constantly exposed to the environment and displays a favorable niche for colonizing microorganisms. However, the effects of respiratory bacterial carriage on the immune system and its implications for secondary responses remain largely unclear. We have employed respiratory carriage with Bordetella bronchiseptica (Bb) as the underlying model to comprehensively address effects on subsequent immune responses. Persistent carriage was associated with the stimulation of Bordetella-specific CD4+, CD8+ and CD4+CD25+Foxp3+ T cell responses and broad transcriptional activation was observed in CD4+CD25+ T cells. Importantly, transfer of lymphocytes from persistent carriers to acutely B. bronchiseptica infected mice resulted in a significantly increased bacterial burden in the recipient’s upper respiratory tract. In contrast, we found that B. bronchiseptica carriage resulted in a significant benefit for the host in systemic infection with Listeria monocytogenes. At the same time, vaccination and influenza A virus infection were unaffected. These data demonstrate that there are significant immune modulatory processes triggered by persistent B. bronchiseptica carriage that differentially affect subsequent immune responses. Thereby our results demonstrate the complexity of immune regulation induced by persistent bacterial carriage in the respiratory tract that can be beneficial or detrimental to the host, depending on the pathogen and the considered compartment.

ORGANISM(S): Mus musculus

PROVIDER: GSE116913 | GEO | 2018/07/12

REPOSITORIES: GEO

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Project description:Public health importance: Babies born preterm, approximately 1 out of every 9 live births in the United States, have significant respiratory morbidity over the first two years of life, exacerbated by respiratory viral infections. Many (<50%) return to pediatricians, emergency rooms and pulmonologists with symptoms of respiratory dysfunction (SRD): intermittent or chronic wheezing, poor growth and an excess of upper and lower respiratory tract infections (LRTI). SRD correlate inversely with gestational age and weight at birth and is more common in those with chronic lung disease of prematurity, yet its incidence and severity varies widely among both the prematurely born and those born at term. There is evidence from clinical studies and animal models that risks of LRTI and recurrent wheezing is influenced by gut and respiratory flora and by T cell responses to infection. Information gained from this study will be used to identify characteristics, risk factors and potential mechanisms for early and persistent lung disease in children born at term and born preterm. This Clinical Research Study will investigate the relationships between sequential respiratory viral infections, patterns of intestinal and respiratory bacterial colonization, and adaptive cellular immune phenotypes which are associated with increased susceptibility to respiratory infections and long term respiratory morbidity in preterm and full term infants. We hypothesize that the timing and acquisition of specific viral infections and bacterial species are directly related to respiratory morbidity in the first year of life as defined by SRD and by measures of pulmonary function. We hypothesize that cellular and molecular immuno-maturity are altered due to factors presented by premature birth in such a way as to promote chronic inflammatory and cytotoxic damage to the lung, with subsequent enhanced, damaging responses to infectious agents and environmental irritants. Our preliminary studies demonstrate both feasibility and expertise in mutiparameter immunophenotyping of small volume peripheral blood samples obtained from premature infants including gene expression arrays of flow cytometry sorted cells. We will use new technologies for known viral identification, as well as high-throughput metagenome sequencing of RNA and DNA virus like particles (VLP) to be used for viral discovery in infant respiratory sample and use of high-throughput pyrosequencing (454T) of bacterial 16S rRNA to determine shifts in bacterial community structure, occurring in pre-term (PT) as compared to full term (FT) infants, over the first year of life. Finally, we present statistical approaches to stratify disease risk predictors using multivariate logistic regression modeling approaches. We propose to evaluate T cell phenotypic and functional profiles relative to viral and predominant bacterial exposures according to highly complementary, but independent, Specific Objectives. Objective 1: To determine if viral respiratory infections and patterns of respiratory and gut bacterial community structure (microbiome) in prematurely born babies predict the rate and degree of immunologic maturation, and pulmonary dysfunction, measured from birth to 36 weeks corrected gestational age (CGA). Objective 2: To determine the relationship between respiratory viral infections and disease severity up to one year CGA, and the lymphocyte (Lc) phenotypes documented at term gestation (birth for term infants and 36 wks/NICU discharge in preterm infants) and at one year CGA. Three secondary outcomes of this objective will be to a) relate the quantity, type and severity of viral infections with pulmonary function at one and three years of life, b) relate the viral community structure to severity of viral infections and c) to seek evidence of modulation of viral susceptibility by bacterial respiratory and gut community structure (microbiome). The relationship of colonization with known and non-identified bacterial species in both the respiratory tract and the gut will be evaluated.

Project description:Rationale: Lower respiratory tract infections continue to exact unacceptable worldwide mortality, often because the infecting pathogen cannot be identified. The respiratory epithelia provide protection from pneumonias through organism-specific generation of antimicrobial products, offering potential insight into the identity of infecting pathogens. Objective: This study assesses the capacity of the host gene expression response to infection to predict lower respiratory pathogens without reliance on culture data. Methods: Mice were inhalationally challenged with S. pneumoniae, P. aeruginosa, A. fumigatus or PBS prior to whole genome gene expression microarray analysis of their pulmonary parenchyma. Characteristic gene expression patterns for each condition were identified, allowing the derivation of prediction rules for each pathogen. After confirming the predictive capacity of gene expression data in blinded challenges, a computerized algorithm was devised to predict the infectious conditions of subsequent subjects. Measurements and Main Results: We observed robust, pathogen-specific gene expression patterns as early as 2 h after infection. We were able to develop a predictive model that used a limited number of specifically regulated transcripts to discriminate perfectly among infecting pathogens in the training data. Validation trials using an algorithmic decision tree revealed 94.4% diagnostic accuracy when discerning the presence of bacterial infection. The model subsequently differentiated between bacterial pathogens with 71.4% accuracy and between non-bacterial conditions with 70.0% accuracy, both far exceeding the expected diagnostic yield of standard culture-based bronchoscopy with bronchoalveolar lavage. Conclusions: These data substantiate the specificity of the pulmonary innate immune response and support the feasibility of a gene expression-based clinical tool for pneumonia diagnosis. Keywords: pathogen- and time-dependent host lung gene expression changes in pneumonia Mouse lungs were removed 6 h after challenge with P. aeruginosa, S. pneumoniae, A. fumigatus or sham (PBS), RNA was collected from leukoreduced lung homogenates, then cRNA was amplified and hybridized to Illumina Sentrix mouse-6 gene expression arrays v1.1. Gene expression data was analyzed to determine if there were distinct patterns of host trasnscription that corresponded with a specific infection.

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Persistent Bordetella bronchiseptica carriage is associated with broad phenotypic alterations of peripheral CD4+CD25+ T cells and differentially affects immune responses to secondary non-infectious and infectious stimuli in mice

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