Differential gene expression profiles of lung epithelial cells exposed to Burkholderia pseudomallei and Burkholderia thailandensis during the initial phase of infection

Department of Immunology, Faculty of Medicine, Siriraj Hospital, Bangkok, Thailand.
Asian Pacific journal of allergy and immunology / launched by the Allergy and Immunology Society of Thailand (Impact Factor: 0.97). 04/2009; 27(1):59-70.
Source: PubMed


Burkholderia pseudomallei is the causative agent of melioidosis, and its infection usually affects patients' lungs. The organism is a facultative intracellular Gram-negative bacillus commonly found in soil and water in endemic tropical regions. Another closely related Burkholderia species found in soil and water is B. thailandensis. This bacterium is a non-pathogenic environmental saprophyte. B. pseudomallei is considerably more efficient than B. thailandensis in host cell invasion and adherence. A previous study by our group demonstrated that after successfully invading cells, there was no difference in the ability to survive and to replicate between both Burkholderia species in cultured A549 human lung epithelial cells. In this study, Human Affymetrix GeneChips were used to identify the difference in gene expression profiles of A549 cells after a 2-h exposure to B. pseudomallei and B. thailandensis. A total of 280 of 22,283 genes were expressed at higher levels in the B. pseudomallei-infected cells than in the B. thailandensis-infected cells, while 280 genes were expressed at lower levels in the B. pseudomallei-infected cells. Approximately 9% of these genes were involved in immune response and apoptosis. Those genes were further selected for gene expression analysis using reverse transcription PCR and/or real-time RT-PCR. The results of RT-PCR and real-time RT-PCR are in accordance with data from the microarray data in that bcl2 gene expression in the B. pseudomallei-infected cells was 2-fold higher than the level in the B. thailandensis-infected cells even though no apoptosis was seen in the infected cells. The levels of E-selectin, ICAM-1, IL-11, IRF-1, IL-6, IL-1beta and LIF genes expression in the B. pseudomallei-infected cells were 1.5-5 times lower than in the B. thailandensis-infected cells. However, both species stimulated the same level of IL-8 production from the tested epithelial cell line, and no difference in the ratio of adherent polymorphonuclear cells (PMNs) to infected A549 cells of both species was observed. Taken together, our results suggest that B. pseudomallei manipulates host response in favor of its survival in the host cell, which may explain the more virulent characteristics of B. pseudomallei when compared with B. thailandensis.

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    • "Many researchers have demonstrated that infections by intracellular pathogens alter the expression of genes encoding pro-inflammatory cytokines and chemokines, which have been implicated as principal mediators during infections of the host in both in vitro and in vivo systems [6,7,33]. These cytokines and chemokines also function as central mediators in stimulating various host defences systems such as the cytokine-cytokine receptor interactions pathway, signalling pathways and apoptosis and eventually elicit appropriate adaptive immune system. "
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    ABSTRACT: Burkholderia cepacia is an opportunistic human pathogen associated with life-threatening pulmonary infections in immunocompromised individuals. Pathogenesis of B. cepacia infection involves adherence, colonisation, invasion, survival and persistence in the host. In addition, B. cepacia are also known to secrete factors, which are associated with virulence in the pathogenesis of the infection. In this study, the host factor that may be the cause of the infection was elucidated in human epithelial cell line, A549, that was exposed to live B. cepacia (mid-log phase) and its secretory proteins (mid-log and early-stationary phases) using the Illumina Human Ref-8 microarray platform. The non-infection A549 cells were used as a control. Expression of the host genes that are related to apoptosis, inflammation and cell cycle as well as metabolic pathways were differentially regulated during the infection. Apoptosis of the host cells and secretion of pro-inflammatory cytokines were found to be inhibited by both live B. cepacia and its secretory proteins. In contrast, the host cell cycle and metabolic processes, particularly glycolysis/glycogenesis and fatty acid metabolism were transcriptionally up-regulated during the infection. Our microarray analysis provided preliminary insights into mechanisms of B. cepacia pathogenesis. The understanding of host response to an infection would provide novel therapeutic targets both for enhancing the host's defences and repressing detrimental responses induced by the invading pathogen.
    PLoS ONE 10/2013; 8(10):e77418. DOI:10.1371/journal.pone.0077418 · 3.23 Impact Factor
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    • "In vitro studies have established that B. pseudomallei is capable of surviving and multiplying intracellularly within professional phagocytes, including macrophages, monocytes and neutrophils (Jones et al., 1996; Stevens and Galyov, 2004) or non-phagocytic cells, including respiratory epithelial cells (Brown et al., 2002; Wongprompitak et al., 2009) although the exact mechanism of invasion and colonization remains unknown. When B. pseudomallei is taken up by macrophage-like cells, it is capable of escaping from endocytic vacuoles into the cytoplasm, where it can replicate by lysing the endosome membrane (Harley et al., 1998). "
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    ABSTRACT: Burkholderia pseudomallei is the etiological agent of melioidosis, a life-threatening disease of humans and animals that occurs primarily in Southeast Asia and northern Australia. The distribution of B. pseudomallei and occurrence of melioidosis globally is very much evident. This soil and water-dwelling saprophyte is resilient to various environments. This organism has gained further notoriety following the Centre for Disease Control's classification of B. pseudomalleias a Tier 1 biological agent. Despite several decades of clinical research, the mortality rate for melioidosis remains high. Genomics-based studies have demonstrated the plasticity of the B. pseudomallei genome and the coding sequences consists of a myriad of functions that enable the bacteria to adapt to these hostile environments as well as various hosts. Diagnosis is mainly based on bacterial culture or serological assays whilst treatment is limited to third generation cephalosporins. To date, no vaccine is currently available as an immunoprophylaxis for melioidosis. By utilising the available genome sequence, a number of virulence factors have recently been identified and have provided more insight into the pathogenesis of B. pseudomallei. These factors include surface associated proteins as well as secreted effector proteins and their corresponding secretion systems. In addition, a number of recent studies on host-pathogen interaction have also demonstrated how the pathogen is able to subvert the host immune system and survive within the cell. This review presents an overview of the current understanding on B. pseudomallei pathogenesis and the disease melioidosis.
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