Dietary therapy of murine primary biliary cholangitis induces hepatocellular steatosis: A cautionary tale.

BACKGROUND AND AIMS: There is increased interest in utilizing dietary interventions to alter the progression of autoimmune diseases. These efforts are driven by associations of gut microbiota/metabolites with levels of short-chain fatty acids (SCFAs). Propionate is a key SCFA that is commonly used as a food preservative and is endogenously generated by bacterial fermentation of non-digestible carbohydrates in the gut. A thesis has suggested that a diet rich in propionate and other SCFAs can successfully modulate autoimmunity. Herein, we investigated the effect of long-term administration of propionylated high-amylose resistant starches (HAMSP) on the course of murine primary biliary cholangitis. MATERIALS AND METHODS: Groups of female ARE-Del mice were fed an HAMSP diet either before or after disease onset. A detailed immunobiological analysis was performed involving autoantibodies and rigorous T-cell phenotyping, including enumeration of T-cell subsets in the spleen, liver, intestinal intraepithelial lymphocytes and lamina propria by flow cytometry. Histopathological scores were used to assess the frequency and severity of liver inflammation and damage to hepatocytes and bile ducts. RESULTS: Our results demonstrate that a long-term propionate-yielding diet re-populated the T-cell pool with decreased naïve and central memory T-cell subsets and an increase in the effector memory T cells in mice. Similarly, long-term HAMSP intake reduced CD4+CD8+ double-positive T cells in intraepithelial lymphocytes and the intestinal lamina propria. Critically, HAMSP consumption led to moderate-to-severe hepatocellular steatosis in ARE-Del mice, independent of the stage of autoimmune cholangitis. CONCLUSIONS: Our data suggest that administration of HAMSP induces both regulatory and effector T cells. Furthermore, HAMSP administration resulted in hepatocellular steatosis. Given the interest in dietary modulation of autoimmunity and because propionate is widely used as a food preservative, these data have significant implications. This study also provides new insights into the immunological and pathological effects of chronic propionate exposure.

Mutated Pkhd1 alone is sufficient to cause autoimmune biliary disease on the nonobese diabetic (NOD) genetic background.

We previously reported that nonobese diabetic (NOD) congenic mice (NOD.c3c4 mice) developed an autoimmune biliary disease (ABD) with similarities to human primary biliary cholangitis (PBC), including anti-mitochondrial antibodies and organ-specific biliary lymphocytic infiltrates. We narrowed the possible contributory regions in a novel NOD.Abd3 congenic mouse to a B10 congenic region on chromosome 1 ("Abd3") and a mutated Pkhd1 gene (Pkhd1del36-67) upstream from Abd3, and we showed via backcrossing studies that the NOD genetic background was necessary for disease. Here, we show that NOD.Abd3 mice develop anti-PDC-E2 autoantibodies at high levels, and that placing the chromosome 1 interval onto a scid background eliminates disease, demonstrating the critical role of the adaptive immune system in pathogenesis. While the NOD genetic background is essential for disease, it was still unclear which of the two regions in the Abd3 locus were necessary and sufficient for disease. Here, using a classic recombinant breeding approach, we prove that the mutated Pkhd1del36-67 alone, on the NOD background, causes ABD. Further characterization of the mutant sequence demonstrated that the Pkhd1 gene is disrupted by an ETnII-beta retrotransposon inserted in intron 35 in an anti-sense orientation. Homozygous Pkhd1 mutations significantly affect viability, with the offspring skewed away from a Mendelian distribution towards NOD Pkhd1 homozygous or heterozygous genotypes. Cell-specific abnormalities, on a susceptible genetic background, can therefore induce an organ-specific autoimmunity directed to the affected cells. Future work will aim to characterize how mutant Pkhd1 can cause such an autoimmune response.

Dual B-cell targeting therapy ameliorates autoimmune cholangitis.

OBJECTIVE: The ability to regulate B cell development has long been recognized to have therapeutic potential in a variety of autoimmune diseases. However, despite the presence of a classic autoantibody in primary biliary cholangitis (PBC), B cell depleting therapy and indeed therapy with other biologic agents has been disappointing. Unsuccessful treatment using Rituximab is associated with elevation of B-cell activating factor (BAFF) level. Indeed, therapies for PBC remain directed at modulating bile salt biology, rather than targeting effector pathways. With these data in mind, we proposed that targeting two major stages of B cell development, namely long-lived memory B cells and short-lived peripheral autoreactive plasma cells would have therapeutic potential. METHODS: To address this thesis, we administrated anti-BAFF and anti-CD20 monoclonal antibody to ARE-Del mice, a well-characterized murine model of human PBC. We evaluated and compared the therapeutic efficacy of the two agents individually and the combination of anti-BAFF and anti-CD20 in female mice with well-established disease. RESULTS: Our data demonstrate that there was an increased level of B cell depletion that resulted in a significantly more effective clinical and serologic response using the combination of agents as compared with the use of the individual agents. The combination of anti-BAFF and anti-CD20 treatment was more effective in reducing serum levels of antimitochondrial antibody (AMA), total IgM and IgG compared to mice treated with the 2 individual agents. Combination treatment efficiently depleted B cells in the peripheral blood, peritoneal cavity and spleen. Importantly, we identified a unique IgM+ FCRL5+ B cell subset which was sensitive to dual B-cell targeting therapy and depletion of this unique population was associated with reduced portal infiltration and bile duct damage. Taken together, our data indicate that dual B cell targeting therapy with anti-BAFF and anti-CD20 not only led to the efficient depletion of B cells both in the peripheral blood and tissues, but also led to significant clinical improvement. These findings highlight the potential application of combination of anti-BAFF and anti-CD20 in treating patients with PBC. However, additional studies in other animal models of PBC should be undertaken before considering human trials in those PBC patients who have incomplete responses to conventional therapy.

Acute peripheral immune activation alters cytokine expression and glial activation in the early postnatal rat brain.

BACKGROUND: Neuroinflammation can modulate brain development; however, the influence of an acute peripheral immune challenge on neuroinflammatory responses in the early postnatal brain is not well characterized. To address this gap in knowledge, we evaluated the peripheral and central nervous system (CNS) immune responses to a mixed immune challenge in early postnatal rats of varying strains and sex. METHODS: On postnatal day 10 (P10), male and female Lewis and Brown Norway rats were injected intramuscularly with either a mix of bacterial and viral components in adjuvant, adjuvant-only, or saline. Immune responses were evaluated at 2 and 5 days post-challenge. Cytokine and chemokine levels were evaluated in serum and in multiple brain regions using a Luminex multiplex assay. Multi-factor ANOVAs were used to compare analyte levels across treatment groups within strain, sex, and day of sample collection. Numbers and activation status of astrocytes and microglia were also analyzed in the cortex and hippocampus by quantifying immunoreactivity for GFAP, IBA-1, and CD68 in fixed brain slices. Immunohistochemical data were analyzed using a mixed-model regression analysis. RESULTS: Acute peripheral immune challenge differentially altered cytokine and chemokine levels in the serum versus the brain. Within the brain, the cytokine and chemokine response varied between strains, sexes, and days post-challenge. Main findings included differences in T helper (Th) type cytokine responses in various brain regions, particularly the cortex, with respect to IL-4, IL-10, and IL-17 levels. Additionally, peripheral immune challenge altered GFAP and IBA-1 immunoreactivity in the brain in a strain- and sex-dependent manner. CONCLUSIONS: These findings indicate that genetic background and sex influence the CNS response to an acute peripheral immune challenge during early postnatal development. Additionally, these data reinforce that the developmental time point during which the challenge occurs has a distinct effect on the activation of CNS-resident cells.

Metabolic network analysis of pre-ASD newborns and 5-year-old children with autism spectrum disorder.

Classical metabolomic and new metabolic network methods were used to study the developmental features of autism spectrum disorder (ASD) in newborns (n = 205) and 5-year-old children (n = 53). Eighty percent of the metabolic impact in ASD was caused by 14 shared biochemical pathways that led to decreased anti-inflammatory and antioxidant defenses, and to increased physiologic stress molecules like lactate, glycerol, cholesterol, and ceramides. CIRCOS plots and a new metabolic network parameter, V ° net, revealed differences in both the kind and degree of network connectivity. Of 50 biochemical pathways and 450 polar and lipid metabolites examined, the developmental regulation of the purine network was most changed. Purine network hub analysis revealed a 17-fold reversal in typically developing children. This purine network reversal did not occur in ASD. These results revealed previously unknown metabolic phenotypes, identified new developmental states of the metabolic correlation network, and underscored the role of mitochondrial functional changes, purine metabolism, and purinergic signaling in autism spectrum disorder.

The long and winding road: From mouse linkage studies to a novel human therapeutic pathway in type 1 diabetes.

Autoimmunity involves a loss of immune tolerance to self-proteins due to a combination of genetic susceptibility and environmental provocation, which generates autoreactive T and B cells. Genetic susceptibility affects lymphocyte autoreactivity at the level of central tolerance (e.g., defective, or incomplete MHC-mediated negative selection of self-reactive T cells) and peripheral tolerance (e.g., failure of mechanisms to control circulating self-reactive T cells). T regulatory cell (Treg) mediated suppression is essential for controlling peripheral autoreactive T cells. Understanding the genetic control of Treg development and function and Treg interaction with T effector and other immune cells is thus a key goal of autoimmunity research. Herein, we will review immunogenetic control of tolerance in one of the classic models of autoimmunity, the non-obese diabetic (NOD) mouse model of autoimmune Type 1 diabetes (T1D). We review the long (and still evolving) elucidation of how one susceptibility gene, Cd137, (identified originally via linkage studies) affects both the immune response and its regulation in a highly complex fashion. The CD137 (present in both membrane and soluble forms) and the CD137 ligand (CD137L) both signal into a variety of immune cells (bi-directional signaling). The overall outcome of these multitudinous effects (either tolerance or autoimmunity) depends upon the balance between the regulatory signals (predominantly mediated by soluble CD137 via the CD137L pathway) and the effector signals (mediated by both membrane-bound CD137 and CD137L). This immune balance/homeostasis can be decisively affected by genetic (susceptibility vs. resistant alleles) and environmental factors (stimulation of soluble CD137 production). The discovery of the homeostatic immune effect of soluble CD137 on the CD137-CD137L system makes it a promising candidate for immunotherapy to restore tolerance in autoimmune diseases.

Endosomal Sequestration of TLR4 Antibody Induces Myeloid-Derived Suppressor Cells and Reverses Acute Type 1 Diabetes.

We previously showed that treating NOD mice with an agonistic monoclonal anti-TLR4/MD2 antibody (TLR4-Ab) reversed acute type 1 diabetes (T1D). Here, we show that TLR4-Ab reverses T1D by induction of myeloid-derived suppressor cells (MDSCs). Unbiased gene expression analysis after TLR4-Ab treatment demonstrated upregulation of genes associated with CD11b+Ly6G+ myeloid cells and downregulation of T-cell genes. Further RNA sequencing of purified, TLR4-Ab-treated CD11b+ cells showed significant upregulation of genes associated with bone marrow-derived CD11b+ cells and innate immune system genes. TLR4-Ab significantly increased percentages and numbers of CD11b+ cells. TLR4-Ab-induced CD11b+ cells, derived ex vivo from TLR4-Ab-treated mice, suppress T cells, and TLR4-Ab-conditioned bone marrow cells suppress acute T1D when transferred into acutely diabetic mice. Thus, the TLR4-Ab-induced CD11b+ cells, by the currently accepted definition, are MDSCs able to reverse T1D. To understand the TLR4-Ab mechanism, we compared TLR4-Ab with TLR4 agonist lipopolysaccharide (LPS), which cannot reverse T1D. TLR4-Ab remains sequestered at least 48 times longer than LPS within early endosomes, alters TLR4 signaling, and downregulates inflammatory genes and proteins, including nuclear factor-κB. TLR4-Ab in the endosome, therefore, induces a sustained, attenuated inflammatory response, providing an ideal "second signal" for the activation/maturation of MDSCs that can reverse acute T1D.

An Exploratory Examination of Neonatal Cytokines and Chemokines as Predictors of Autism Risk: The Early Markers for Autism Study.

BACKGROUND: The identification of an early biomarker for autism spectrum disorder (ASD) would improve the determination of risk, leading to earlier diagnosis and, potentially, earlier intervention and improved outcomes. METHODS: Data were generated from the Early Markers for Autism study, a population-based case-control study of prenatal and neonatal biomarkers of ASD. Newborn bloodspots of children with ASD (n = 370), children with developmental delay (n = 140), and general population (GP) controls (n = 378) were analyzed for 42 different immune markers using a Luminex multiplex platform. Comparisons of immune marker concentrations between groups were examined using logistic regression and partial least squares discriminant analysis. RESULTS: Children with ASD had significantly increased neonatal levels of interleukin-6 (IL-6) and IL-8 compared with GP controls. An increase in IL-8 was especially significant in the ASD group with early onset compared with the GP group, with an adjusted odds ratio of 1.97 (95% confidence interval, 1.39-2.83; p = .00014). In addition, children with ASD had significantly elevated levels of eotaxin-1, interferon-γ, and IL-12p70 relative to children with developmental delay. We observed no significant differences in levels of immune markers between the developmental delay and GP groups. CONCLUSIONS: Elevated levels of some inflammatory markers in newborn bloodspots indicated a higher degree of immune activation at birth in children who were subsequently diagnosed with ASD. The data from this exploratory study suggest that with further expansion, the development of neonatal bloodspot testing for cytokine/chemokine levels might lead to the identification of biomarkers that provide an accurate assessment of ASD risk at birth.

Cross-genetic determination of maternal and neonatal immune mediators during pregnancy.

BACKGROUND: The immune system plays a fundamental role in development during pregnancy and early life. Alterations in circulating maternal and neonatal immune mediators have been associated with pregnancy complications as well as susceptibility to autoimmune and neurodevelopmental conditions in later life. Evidence suggests that the immune system in adults not only responds to environmental stimulation but is also under strong genetic control. METHODS: This is the first genetic study of > 700 mother-infant pairs to analyse the circulating levels of 22 maternal mid-gestational serum-derived and 42 neonatal bloodspot-derived immune mediators (cytokines/chemokines) in the context of maternal and fetal genotype. We first estimated the maternal and fetal genome-wide SNP-based heritability (h2g) for each immune molecule and then performed genome-wide association studies (GWAS) to identify specific loci contributing to individual immune mediators. Finally, we assessed the relationship between genetic immune determinants and ASD outcome. RESULTS: We show maternal and neonatal cytokines/chemokines displaying genetic regulation using independent methodologies. We demonstrate that novel fetal loci for immune function independently affect the physiological levels of maternal immune mediators and vice versa. The cross-associated loci are in distinct genomic regions compared with individual-specific immune mediator loci. Finally, we observed an interaction between increased IL-8 levels at birth, autism spectrum disorder (ASD) status, and a specific maternal genotype. CONCLUSIONS: Our results suggest that maternal and fetal genetic variation influences the immune system during pregnancy and at birth via distinct mechanisms and that a better understanding of immune factor determinants in early development may shed light on risk factors for developmental disorders.

Increased production of IL-17 in children with autism spectrum disorders and co-morbid asthma.

Inflammation and asthma have both been reported in some children with autism spectrum disorder (ASD). To further assess this connection, peripheral immune cells isolated from young children with ASD and typically developing (TD) controls and the production of cytokines IL-17, -13, and -4 assessed following ex vivo mitogen stimulation. Notably, IL-17 production was significantly higher following stimulation in ASD children compared to controls. Moreover, IL-17 was increased in ASD children with co-morbid asthma compared to controls with the same condition. In conclusion, children with ASD exhibited a differential response to T cell stimulation with elevated IL-17 production compared to controls.

Decreased levels of total immunoglobulin in children with autism are not a result of B cell dysfunction.

Autism spectrum disorders are a heterogeneous group of behaviorally defined disorders having complex etiologies. We previously reported a direct correlation between lower plasma levels of the immunoglobulins (Ig) IgG and IgM and increased severity of behavioral symptoms in children with autism. Our current objective was to determine if these reduced plasma levels of IgG and IgM are the result of defective B cell development, activation, or function. Results suggest no differences in the B cell parameters measured, indicating that decreased Ig in autism is not a result of B cell dysfunction and other immune cells might be involved.

Reduced levels of immunoglobulin in children with autism correlates with behavioral symptoms.

OBJECTIVES: To assay if plasma antibody levels in children with autism or developmental delays (DD) differ from those with typical development as an indicator of immune function and to correlate antibody levels with severity of behavioral symptoms. METHODS: Plasma was collected from children with autistic disorder (AU; n=116), DD but not autism (n=32), autism spectrum disorder but not full autism (n=27), and age-matched typically developing (TD) controls (n=96). Samples were assayed for systemic levels of immunoglobulin (IgG, IgM, IgA, and IgE) by enzyme-linked immunosorbent assay. Subjects with autism were evaluated using the Autism Diagnostic Observation Schedule and the Autism Diagnostic Interview-Revised, and all subjects were scored on the Aberrant Behavior Checklist (ABC) by the parents. Numerical scores for each of the ABC subscales as well as the total scores were then correlated with Ig levels. RESULTS: Children with AU have a significantly reduced level of plasma IgG (5.39+/-0.29 mg/mL) compared to the TD (7.72+/-0.28 mg/mL; P<0.001) and DD children (8.23+/-0.49 mg/mL; P<0.001). Children with autism also had a reduced level of plasma IgM (0.670.06 mg/mL) compared to TD (0.79+/-0.05 mg/mL; P<0.05). Ig levels were negatively correlated with ABC scores for all children (IgG: r=-0.334, P<0.0001; IgM: r=-0.167, P=0.0285). CONCLUSION: Children with AU have significantly reduced levels of plasma IgG and IgM compared to both DD and TD controls, suggesting an underlying defect in immune function. This reduction in specific Ig levels correlates with behavioral severity, where those patients with the highest scores in the behavioral battery have the most reduced levels of IgG and IgM.

Tobacco smoke induces a persistent, but recoverable state in Chlamydia pneumoniae infection of human endothelial cells.

We investigated the extent to which tobacco smoke could induce persistence of Chlamydia pneumoniae in human endothelial cells. Aortic and coronary artery endothelia were infected in the absence or presence of non-cytotoxic concentrations of tobacco smoke medium. Following exposure to smoke medium, chlamydial inclusions were smaller and demonstrated fewer genome copies as determined by real-time PCR. Enumeration of inclusion-forming units (IFU) established a significant smoke-mediated, dose-dependent inhibition of elementary bodies (EB). Host cell apoptosis did not contribute to the observed restriction of productive infection. Ultrastructure analysis demonstrated an arrest in chlamydial development following smoke-exposure, with a predominance of reticulate bodies (RB) observed inside inclusions. Recovery of viable IFU was achieved with removal of smoke-medium and addition of L-tryptophan. In the presence of smoke, C. pneumoniae infection demonstrated all the characteristics of persistence in human endothelia cells. This is the first time that primary human arterial endothelial cells have been shown to support chlamydial persistence. Tobacco smoke is a well-characterized risk factor for progression of atherosclerosis, but a novel means of inducing chlamydial persistence in vascular cells. Thus, smoking may additionally contribute to atherosclerotic disease by inducing a persistent chlamydial infection in arterial endothelium.

Tobacco smoke induces persistent infection of Chlamydophila pneumoniae in HEp-2 cells.

We examined tobacco smoke exposure and its effect on the life cycle of Chlamydophila pneumoniae (C. pneumoniae) in HEp-2, a human respiratory epithelial cell line. Using noncytotoxic concentrations of smoke medium, chlamydiae were grown in tissue culture and infectious particles were quantitated indirectly by immunocytometry of infected indicator cells. Chlamydial genome copy number was assessed with real-time polymerase chain reaction, and ultrastructure was examined by transmission electron microscopy. There was a significant reduction (56-64%; p<0.05) in the number of infectious elementary bodies following smoke exposure compared to untreated cultures. Under the same conditions, at late time points, smoke-exposed cultures showed significantly fewer chlamydial DNA copies (p<0.04). Moreover, smoke exposure induced large aberrant bodies that predominated within the inclusion. Following in vitro smoke exposure, alterations in the developmental cycle of C. pneumoniae included: inhibition of productive infection, reduced bacterial cell division, and formation of aberrant bodies. Thus, using this novel system, we were able to induce chlamydial persistence. Tobacco smoke exposure may represent a risk for establishment of a chronic reservoir of C. pneumoniae infection within respiratory epithelium.