Sodium perturbs mitochondrial respiration and induces dysfunctional Tregs.

FOXP3+ regulatory T cells (Tregs) are central for peripheral tolerance, and their deregulation is associated with autoimmunity. Dysfunctional autoimmune Tregs display pro-inflammatory features and altered mitochondrial metabolism, but contributing factors remain elusive. High salt (HS) has been identified to alter immune function and to promote autoimmunity. By investigating longitudinal transcriptional changes of human Tregs, we identified that HS induces metabolic reprogramming, recapitulating features of autoimmune Tregs. Mechanistically, extracellular HS raises intracellular Na+, perturbing mitochondrial respiration by interfering with the electron transport chain (ETC). Metabolic disturbance by a temporary HS encounter or complex III blockade rapidly induces a pro-inflammatory signature and FOXP3 downregulation, leading to long-term dysfunction in vitro and in vivo. The HS-induced effect could be reversed by inhibition of mitochondrial Na+/Ca2+ exchanger (NCLX). Our results indicate that salt could contribute to metabolic reprogramming and that short-term HS encounter perturb metabolic fitness and long-term function of human Tregs with important implications for autoimmunity.

Acidic Microenvironments Found in Cutaneous Leishmania Lesions Curtail NO-Dependent Antiparasitic Macrophage Activity.

Local tissue acidosis affects anti-tumor immunity. In contrast, data on tissue pH levels in infected tissues and their impact on antimicrobial activity is sparse. In this study, we assessed the pH levels in cutaneous Leishmania lesions. Leishmania major-infected skin tissue displayed pH levels of 6.7 indicating that lesional pH is acidic. Next, we tested the effect of low extracellular pH on the ability of macrophages to produce leishmanicidal NO and to fight the protozoan parasite Leishmania major. Extracellular acidification led to a marked decrease in both NO production and leishmanicidal activity of lipopolysaccharide (LPS) and interferon γ (IFN-γ)-coactivated macrophages. This was not directly caused by a disruption of NOS2 expression, a shortage of reducing equivalents (NAPDH) or substrate (L-arginine), but by a direct, pH-mediated inhibition of NOS2 enzyme activity. Normalization of intracellular pH significantly increased NO production and antiparasitic activity of macrophages even in an acidic microenvironment. Overall, these findings indicate that low local tissue pH can curtail NO production and leishmanicidal activity of macrophages.

Staphylococcus colonization, mortality and morbidity in hemodialysis patients: 10 years of observation.

Colonization with Staphylococci is widely distributed among patients with end-stage renal disease who are receiving hemodialysis (HD). In addition to more intensive care and use of artificial devices, the incidence of methicillin-resistant Staphylococcus aureus (MRSA) colonization and infection has increased. Such colonization has recently been associated with a more than doubled mortality rate in HD patients. However, it is not clear whether the (presumably increasing) incidence of methicillin-sensitive Staphylococcus aureus (MSSA) colonization is associated with MRSA and/or morbidity and mortality. We therefore established a screening program in our HD population (n=156) and followed these patients over 10 years. We discovered eighty-eight MSSA-colonized patients and one MRSA-colonized patient by cross-sectional and admission-related screenings between 2000 and 2010. The morbidity and mortality of the HD patients was not related to MSSA colonization. The MSSA colonization rate decreased slightly during the 10-year observation period. We conclude that the incidence of MRSA colonization in our unit was lower compared to that reported in the literature. The reasons for this finding are complex and require further investigation. The incidence of MSSA colonization was frequent but did not impact morbidity or mortality.

Four years of universal pneumococcal conjugate infant vaccination in Germany: impact on incidence of invasive pneumococcal disease and serotype distribution in children.

INTRODUCTION: Vaccination with pneumococcal conjugate vaccine (PCV) for all children <2 years was recommended in Germany in July 2006. Initially PCV7 was exclusively used; PCV10 became available from April 2009 and PCV7 was replaced by PCV13 in December 2009. OBJECTIVE: To compare the incidence and serotype distribution of invasive pneumococcal disease (IPD) for pneumococcal meningitis and non-meningitis IPD in children from 2007 to 2010 with reference to the pre-vaccination period from 1997 to 2001. METHODS: Nationwide surveillance of IPD for children <16 years in Germany was based on two independent reporting sources: active surveillance in paediatric hospitals and passive web-based surveillance through microbiological laboratories. Serotyping was performed using the Neufeld Quellung reaction. CASE DEFINITION: isolation of Streptococcus pneumoniae from a normally sterile body site. IPD incidence was estimated by capture-recapture analysis. Rate ratios comparing post- to pre-vaccination incidence were calculated as well as PCV7 and non-PCV7 serotype specific incidences. RESULTS: While PCV7 incidence decreased by 88% (95%CI: 83 to 91) in children <16 years both in pneumococcal meningitis and non-meningitis IPD, an increase in Non-PCV7 serotypes was observed which was more pronounced in non-meningitis cases (168%; 95%CI: 140-257) than in pneumoccocal meningitis (65%; 95%CI: 23-123). The changes in incidence after four years were: <16 years: -35% (95%CI: -49 to -19), <2 years: -46% (95%CI: -61 to -27) for pneumococcal meningitis and+11% (95%CI: -4 to +29) and -26% (95%CI: -41 to -7) for non-meningitis IPD respectively. CONCLUSION: Infant PCV7 vaccination in Germany prompted a decrease in the incidence of pneumococcal meningitis similar to that observed in England/Wales. In non-meningitis IPD the decrease was smaller and confined to the age group <2 years with no change or an increase in incidence in other age groups pointing to potential ascertainment bias due to increased blood-culturing.

Efficacy of vision restoration therapy after optic neuritis (VISION study): study protocol for a randomized controlled trial.

BACKGROUND: Optic neuritis is a frequent manifestation of multiple sclerosis. Visual deficits range from a minor impairment of visual functions through to complete loss of vision. Although many patients recover almost completely, roughly 35% of patients remain visually impaired for years, and therapeutic options for those patients hardly exist. Vision restoration therapy is a software-based visual training program that has been shown to improve visual deficits after pre- and postchiasmatic injury. The aim of this pilot study is to evaluate whether residual visual deficits after past or recent optic neuritis can be reduced by means of vision restoration therapy. METHODS/DESIGN: A randomized, controlled, patient- and observer-blinded clinical pilot study (VISION study) was designed to evaluate the efficacy of vision restoration therapy in optic neuritis patients. Eighty patients with a residual visual deficit after optic neuritis (visual acuity ≤0.7 and/or scotoma) will be stratified according to the time of optic neuritis onset (manifestation more than 12 months ago (40 patients, fixed deficit) versus manifestation 2 to 6 months ago (40 patients, recent optic neuritis)), and randomized into vision restoration therapy arm or saccadic training arm (control intervention). Patients will be instructed to complete a computer-based visual training for approximately 30 minutes each day for a period of 6 months. Patients and evaluators remain blinded to the treatment allocation throughout the study. All endpoints will be analyzed and P-values < 0.05 will be considered statistically significant. The primary outcome parameter will be the expansion of the visual field after 3 and 6 months of treatment as determined by static visual field perimetry and high resolution perimetry. Secondary outcome variables will include visual acuity at both low and high contrast, glare contrast sensitivity, visually evoked potentials, optical coherence tomography and other functional tests of the visual system, alertness, health-related quality of life, fatigue, and depression. DISCUSSION: If vision restoration therapy is shown to improve visual function after optic neuritis, this method might be a first therapeutic option for patients with incomplete recovery from optic neuritis. TRIAL REGISTRATION: NCT01274702.

Post-pandemic seroprevalence of pandemic influenza A (H1N1) 2009 infection (swine flu) among children <18 years in Germany.

BACKGROUND: We determined antibodies to the pandemic influenza A (H1N1) 2009 virus in children to assess: the incidence of (H1N1) 2009 infections in the 2009/2010 season in Germany, the proportion of subclinical infections and to compare titers in vaccinated and infected children. METHODOLOGY/PRINCIPAL FINDINGS: Eight pediatric hospitals distributed over Germany prospectively provided sera from in- or outpatients aged 1 to 17 years from April 1(st) to July 31(st) 2010. Vaccination history, recall of infections and sociodemographic factors were ascertained. Antibody titers were measured with a sensitive and specific in-house hemagglutination inhibition test (HIT) and compared to age-matched sera collected during 6 months before the onset of the pandemic in Germany. We analyzed 1420 post-pandemic and 300 pre-pandemic sera. Among unvaccinated children aged 1-4 and 5-17 years the prevalence of HI titers (≥1∶10) was 27.1% (95% CI: 23.5-31.3) and 53.5% (95% CI: 50.9-56.2) compared to 1.7% and 5.5%, respectively, for pre-pandemic sera, accounting for a serologically determined incidence of influenza A (H1N1) 2009 during the season 2009/2010 of 25,4% (95% CI : 19.3-30.5) in children aged 1-4 years and 48.0% (95% CI: 42.6-52.0) in 5-17 year old children. Of children with HI titers ≥1∶10, 25.5% (95% CI: 22.5-28.8) reported no history of any infectious disease since June 2009. Among vaccinated children, 92% (95%-CI: 87.0-96.6) of the 5-17 year old but only 47.8% (95%-CI: 33.5-66.5) of the 1-4 year old children exhibited HI titers against influenza A virus (H1N1) 2009. CONCLUSION: Serologically determined incidence of influenza A (H1N1) 2009 infections in children indicates high infection rates with older children (5-17 years) infected twice as often as younger children. In about a quarter of the children with HI titers after the season 2009/2010 subclinical infections must be assumed. Low HI titers in young children after vaccination with the AS03(B)-adjuvanted split virion vaccine need further scrutiny.

Essential crosstalk between myeloid and lymphoid cells for development of chronic colitis in myeloid-specific signal transducer and activator of transcription 3-deficient mice.

Dysregulated cytokine responsiveness by myeloid cells can be a trigger for the development of chronic inflammation as well as inflammatory bowel disease. Thus, mice with a myeloid-specific defect in signal transducer and activator of transcription (Stat) 3 develop spontaneous colitis secondary to the inability of myeloid cells to respond to the immunosuppressive cytokine interleukin-10. We now examined whether the inflammation caused by Stat3-deficient macrophages is cell autonomous or dependent on their interaction with lymphocytes. For this purpose, myeloid-specific Stat3-deficient mice (LysMcre/Stat3(flox) mice) were intercrossed with RAG-1 knockout mice to generate LysMcre/Stat3(flox) RAG(-/-) mice. In these mutants and LysMcre/Stat3(flox) littermate control mice we determined the onset and severity of spontaneous chronic enterocolitis, and the reaction to dextran sodium sulphate (DSS)-induced epithelial damage, as well as to lipopolysaccharide (LPS) challenge. In contrast to LysMcre/Stat3(flox) mice, LysMcre/Stat3(flox) RAG(-/-) animals are protected from chronic enterocolitis. Although they respond to oral dextran sulphate with acute colitis symptoms, the inflammation heals similarly to wild type mice whereas LysMcre/Stat3(flox) mice exhibit continued colitis pathology. In addition, the hyperreactivity of LysMcre/Stat3(flox) mice to LPS-challenge in vivo was less severe in the absence of lymphocytes. Despite clear differences in the strength of inflammatory responses, macrophages of both LysMcre/Stat3(flox) mice and LysMcre/Stat3(flox) RAG(-/-) animals exhibited increased costimulatory capacity. In conclusion, our findings demonstrate that Stat3-deficient myeloid cells alone are not capable of inducing the severe pathology seen in LysMcre/Stat3(flox) mice. Yet when these cells can interact with lymphocytes their increased costimulatory potential will trigger an overshooting inflammatory response.

MHC class II expression through a hitherto unknown pathway supports T helper cell-dependent immune responses: implications for MHC class II deficiency.

MHC class II (MHCII) deficiency or bare lymphocyte syndrome (BLS) is a severe immunodeficiency characterized by deficient T helper (Th)-cell-dependent immunity. The disease is caused by defects of the MHCII promoter complex resulting in low or absent MHCII expression. We demonstrate in a murine model of MHCII deficiency (RFX5- or CIITA-deficient mice) that residual MHCII expression by professional antigen-presenting cells (APCs) is sufficient to support activation of adoptively transferred Th cells. Furthermore, upon transplantation of WT thymic epithelium, we observed development of endogenous Th cells with restoration of Th-cell-dependent antibody responses and immunity to cytomegalovirus infection, thus opening the possibility of an alternative treatment regimen for BLS. Residual MHCII expression was further induced by the presence of Th cells and also other stimuli. Analysis of CIITA/RFX5 double-deficient animals revealed that this inducible MHCII expression is genetically independent of the known promoter complex and thus constitutes an alternative MHCII expression pathway. In these experiments, we also detected a novel repressive function of the RFX complex in the absence of CIITA.

Modulation of central hypersensitivity by nociceptive input in chronic pain after whiplash injury.

OBJECTIVE: Chronic pain after whiplash injury is associated with hypersensitivity of the central nervous system to peripheral stimulation. It is unclear whether central hypersensitivity is modulated by peripheral nociceptive input. We hypothesized that changes in nociceptive input would correlate with changes in magnitude of central hypersensitivity. DESIGN: Fifteen patients with chronic pain after whiplash injury were investigated. Changes in nociceptive input were induced by infiltration of painful and tender muscles with bupivacaine (0.25%). Such infiltrations produce either pain reduction or pain enhancement, the latter effect probably resulting from transient injection-induced trauma. We used this individual variability in correlation analyses. Changes in intensity of neck pain, as assessed by a visual analog scale (VAS), after infiltration were assumed to reflect changes in nociceptive input. Changes in pressure pain thresholds recorded at healthy tissues (nonpainful point of the neck and the second toe) were used to measure changes in central hypersensitivity. The correlations between the change in VAS score and changes in pressure pain thresholds 15 minutes after infiltration were analyzed. RESULTS: Statistically significant negative correlations were found between change in VAS score and changes in threshold measurements performed at the neck, but not at the toe. CONCLUSIONS: Different mechanisms underlie hyperalgesia localized at areas surrounding the site of pain and hyperalgesia generalized to distant body areas. Central hypersensitivity as a determinant of neck pain is probably a dynamic condition that is influenced by the presence and activity of a nociceptive focus.

Compartmentalized production of CCL17 in vivo: strong inducibility in peripheral dendritic cells contrasts selective absence from the spleen.

Dendritic cells (DCs)(*) fulfill an important regulatory function at the interface of the innate and adaptive immune system. The thymus and activation-regulated chemokine (TARC/CCL17) is produced by DCs and facilitates the attraction of activated T cells. Using a fluorescence-based in vivo reporter system, we show that CCL17 expression in mice is found in activated Langerhans cells and mature DCs located in various lymphoid and nonlymphoid organs, and is up-regulated after stimulation with Toll-like receptor ligands. DCs expressing CCL17 belong to the CD11b(+)CD8(-)Dec205(+) DC subset, including the myeloid-related DCs located in the subepithelial dome of Peyer's patches. CCL17-deficient mice mount diminished T cell-dependent contact hypersensitivity responses and display a deficiency in rejection of allogeneic organ transplants. In contrast to lymphoid organs located at external barriers of the skin and mucosa, CCL17 is not expressed in the spleen, even after systemic microbial challenge or after in vitro stimulation. These findings indicate that CCL17 production is a hallmark of local DC stimulation in peripheral organs but is absent from the spleen as a filter of blood-borne antigens.