1α,25-dihydroxyvitamin D3 in combination with transforming growth factor-ß increases the frequency of Foxp3⁺ regulatory T cells through preferential expansion and usage of interleukin-2.

A high prevalence of vitamin D insufficiency and deficiency exists worldwide, which is associated with an increased incidence and severity of a range of immune-mediated diseases. This has resulted in considerable interest in the immunodulatory functions of vitamin D. The active form of vitamin D, 1α,25-dihydroxyvitamin D3 [1,25(OH)2D3], has been shown to increase the frequency of Foxp3(+) CD4(+) T regulatory (Treg) cells when present at high concentrations or under strong T-cell stimulation in culture. Supporting evidence exists in vivo for a positive association between serum 25(OH)D and Foxp3(+) Treg cell numbers in humans. The aim of this work was to identify the cytokine milieu required in vitro to promote Foxp3(+) Treg cells in cultures containing 1,25(OH)2D3 at more moderate concentrations (10(-7) M). Stimulation of human CD4(+) T cells with a combination of 1,25(OH)2D3 and transforming growth factor-ß (TGF-ß) greatly increased the frequency of Foxp3(+) Treg cells, which is proposed to result from the preferential expansion of Foxp3(+) Treg cells, as compared with the Foxp3(-) effector T cells, in culture. The differential effect on proliferation may result from enhanced availability and usage of interleukin-2 by the Foxp3(+) Treg cells compared with Foxp3(-) effector T cells. In summary, modulation of the cytokine environment to one high in TGF-ß in the presence of 1,25(OH)2D3(10(-7) M) significantly increased Foxp3(+) Treg cell frequency. These data provide additional evidence for the important immunomodulatory properties of 1,25(OH)2D3 that exist and may help to control inflammatory diseases.

A transcriptomic reporter assay employing neutrophils to measure immunogenic activity of septic patients' plasma.

BACKGROUND: There are diverse molecules present in blood plasma that regulate immune functions and also present a potential source of disease biomarkers and therapeutic targets. Genome-wide profiling has become a powerful method for assessing immune responses on a systems scale, but technologies that can measure the plasma proteome still face considerable challenges. An alternative approach to direct proteome assessment is to measure transcriptome responses in reporter cells exposed in vitro to plasma. In this report we describe such a "transcriptomic reporter assay" to assess plasma from patients with sepsis, which is a common and severe systemic infectious process for which physicians lack efficient diagnostic or prognostic markers. METHODS: Plasma samples collected from patients with culture-confirmed bacterial sepsis and uninfected healthy controls were used to stimulate three separate cell types - neutrophils, peripheral blood mononuclear cells, and monocyte-derived dendritic cells. Whole genome microarrays were generated from stimulated cells to assess transcriptional responses. Unsupervised analysis and enriched functional networks were evaluated for each cell type. Principal component analyses were used to assess variability in responses. A random K-nearest neighbor - feature selection algorithm was used to identify markers predictive of sepsis severity, which were then validated in an independent data set. RESULTS: Neutrophils demonstrated the most distinct response to plasma from septic patients with 709 genes showing altered expression profiles, many of which are involved in established immunologic pathways. The amplitude of the neutrophil transcriptomic response was shown to be correlated with sepsis severity in two independent sets of patients comprised of 64 total septic patients. A subset of 30 transcripts selected using one set of patients was demonstrated to have a high degree of accuracy (82-90%) in predicting sepsis severity and outcomes in the other independent set. This subset included several genes previously established in sepsis pathogenesis as well as novel genes. CONCLUSIONS: These results demonstrate both the suitability and potential clinical relevance of a neutrophil reporter assay for studying plasma, in this case from septic patients. The distinctive transcriptional signature we found could potentially help predict severity of disease and guide treatment. Our findings also shed new light on mechanisms of immune dysregulation in sepsis.

Human immune responses to Burkholderia pseudomallei characterized by protein microarray analysis.

BACKGROUND: We aimed to determine the antibody and T cell responses to Burkholderia pseudomallei of humans to select candidate vaccine antigens. METHODS: For antibody profiling, a protein microarray of 154 B. pseudomallei proteins was probed with plasma from 108 healthy individuals and 72 recovered patients. Blood from 20 of the healthy and 30 of the recovered individuals was also obtained for T cell assays. RESULTS: Twenty-seven proteins distinctively reacted with human plasma following environmental exposure or clinical melioidosis. We compared the responses according to the patient's history of subsequent relapse, and antibody response to BPSL2765 was higher in plasma from individuals who had only 1 episode of disease than in those with recurrent melioidosis. A comparison of antibody and T cell responses to 5 B. pseudomallei proteins revealed that BimA and flagellin-induced responses were similar but that BPSS0530 could induce T cell responses in healthy controls more than in recovered patients. CONCLUSIONS: By combining large-scale antibody microarrays and assays of T cell-mediated immunity, we identified a panel of novel B. pseudomallei proteins that show distinct patterns of reactivity in different stages of human melioidosis. These proteins may be useful candidates for development of subunit-based vaccines and in monitoring the risks of treatment failure and relapse.

Bystander T cells in human immune responses to dengue antigens.

BACKGROUND: Previous studies of T cell activation in dengue infection have focused on restriction of specific T cell receptors (TCRs) and classical MHC molecules. However, bystander T cell activation, which is TCR independent, occurs via cytokines in other viral infections, both in vitro and in vivo, and enables T cells to bypass certain control checkpoints. Moreover, clinical and pathological evidence has pointed to cytokines as the mediators of dengue disease severity. Therefore, we investigated bystander T cell induction by dengue viral antigen. RESULTS: Whole blood samples from 55 Thai schoolchildren aged 13-14 years were assayed for in vitro interferon-gamma (IFN-γ) induction in response to inactivated dengue serotype 2 antigen (Den2). The contribution of TCR-dependent and independent pathways was tested by treatment with cyclosporin A (CsA), which inhibits TCR-dependent activation of T cells. ELISA results revealed that approximately 72% of IFN-γ production occurred via the TCR-dependent pathway. The major IFN-γ sources were natural killer (NK) (mean ± SE = 55.2 ± 3.3), CD4+T (24.5 ± 3.3) and CD8+T cells (17.9 ± 1.5), respectively, as demonstrated by four-color flow cytometry. Interestingly, in addition to these cells, we found CsA-resistant IFN-γ producing T cells (CD4+T = 26.9 ± 3.6% and CD8+T = 20.3 ± 2.1%) implying the existence of activated bystander T cells in response to dengue antigen in vitro. These bystander CD4+ and CD8+T cells had similar kinetics to NK cells, appeared after 12 h and were inhibited by anti-IL-12 neutralization indicating cytokine involvement. CONCLUSIONS: This study described immune cell profiles and highlighted bystander T cell activation in response to dengue viral antigens of healthy people in an endemic area. Further studies on bystander T cell activation in dengue viral infection may reveal the immune mechanisms that protect or enhance pathogenesis of secondary dengue infection.

Glibenclamide reduces pro-inflammatory cytokine production by neutrophils of diabetes patients in response to bacterial infection.

Type 2 diabetes mellitus is a major risk factor for melioidosis, which is caused by Burkholderia pseudomallei. Our previous study has shown that polymorphonuclear neutrophils (PMNs) from diabetic subjects exhibited decreased functions in response to B. pseudomallei. Here we investigated the mechanisms regulating cytokine secretion of PMNs from diabetic patients which might contribute to patient susceptibility to bacterial infections. Purified PMNs from diabetic patients who had been treated with glibenclamide (an ATP-sensitive potassium channel blocker for anti-diabetes therapy), showed reduction of interleukin (IL)-1ß and IL-8 secretion when exposed to B. pseudomallei. Additionally, reduction of these pro-inflammatory cytokines occurred when PMNs from diabetic patients were treated in vitro with glibenclamide. These findings suggest that glibenclamide might be responsible for the increased susceptibility of diabetic patients, with poor glycemic control, to bacterial infections as a result of its effect on reducing IL-1ß production by PMNs.

Phenotypic and functional characterization of human memory T cell responses to Burkholderia pseudomallei.

BACKGROUND: Infection with the Gram-negative bacterium Burkholderia pseudomallei is an important cause of community-acquired lethal sepsis in endemic regions in southeast Asia and northern Australia and is increasingly reported in other tropical areas. In animal models, production of interferon-gamma (IFN-gamma) is critical for resistance, but in humans the characteristics of IFN-gamma production and the bacterial antigens that are recognized by the cell-mediated immune response have not been defined. METHODS: Peripheral blood from 133 healthy individuals who lived in the endemic area and had no history of melioidosis, 60 patients who had recovered from melioidosis, and 31 other patient control subjects were stimulated by whole bacteria or purified bacterial proteins in vitro, and IFN-gamma responses were analyzed by ELISPOT and flow cytometry. FINDINGS: B. pseudomallei was a potent activator of human peripheral blood NK cells for innate production of IFN-gamma. In addition, healthy individuals with serological evidence of exposure to B. pseudomallei and patients recovered from active melioidosis developed CD4(+) (and CD8(+)) T cells that recognized whole bacteria and purified proteins LolC, OppA, and PotF, members of the B. pseudomallei ABC transporter family. This response was primarily mediated by terminally differentiated T cells of the effector-memory (T(EMRA)) phenotype and correlated with the titer of anti-B. pseudomallei antibodies in the serum. CONCLUSIONS: Individuals living in a melioidosis-endemic region show clear evidence of T cell priming for the ability to make IFN-gamma that correlates with their serological status. The ability to detect T cell responses to defined B. pseudomallei proteins in large numbers of individuals now provides the opportunity to screen candidate antigens for inclusion in protein or polysaccharide-conjugate subunit vaccines against this important but neglected disease.