Christine D. Palmer

Disordered macrophage cytokine secretion underlies impaired acute inflammation and bacterial clearance in Crohn's disease

The cause of Crohns disease (CD) remains poorly understood. Counterintuitively, these patients possess an impaired acute inflammatory response, which could result in delayed clearance of bacteria penetrating the lining of the bowel and predispose to granuloma formation and chronicity. We tested this hypothesis in human subjects by monitoring responses to killed Escherichia coli injected subcutaneously into the forearm. Accumulation of 111In-labeled neutrophils at these sites and clearance of 32P-labeled bacteria from them were markedly impaired in CD. Locally increased blood flow and bacterial clearance were dependent on the numbers of bacteria injected. Secretion of proinflammatory cytokines by CD macrophages was grossly impaired in response to E. coli or specific Toll-like receptor agonists. Despite normal levels and stability of cytokine messenger RNA, intracellular levels of tumor necrosis factor (TNF) were abnormally low in CD macrophages. Coupled with reduced secretion, these findings indicate accelerated intracellular breakdown. Differential transcription profiles identified disease-specific genes, notably including those encoding proteins involved in vesicle trafficking. Intracellular destruction of TNF was decreased by inhibitors of lysosomal function. Together, our findings suggest that in CD macrophages, an abnormal proportion of cytokines are routed to lysosomes and degraded rather than being released through the normal secretory pathway.

The Ultra-Potent and Selective TLR8 Agonist VTX-294 Activates Human Newborn and Adult Leukocytes

Background Newborns display distinct immune responses that contribute to susceptibility to infection and reduced vaccine responses. Toll-like receptor (TLR) agonists may serve as vaccine adjuvants, when given individually or in combination, but responses of neonatal leukocytes to many TLR agonists are diminished. TLR8 agonists are more effective than other TLR agonists in activating human neonatal leukocytes in vitro, but little is known about whether different TLR8 agonists may distinctly activate neonatal leukocytes. We characterized the in vitro immuno-stimulatory activities of a novel benzazepine TLR8 agonist, VTX-294, in comparison to imidazoquinolines that activate TLR8 (R-848; (TLR7/8) CL075; (TLR8/7)), with respect to activation of human newborn and adult leukocytes. Effects of VTX-294 and R-848 in combination with monophosphoryl lipid A (MPLA; TLR4) were also assessed. Methods TLR agonist specificity was assessed using TLR-transfected HEK293 cells expressing a NF-κB reporter gene. TLR agonist-induced cytokine production was measured in human newborn cord and adult peripheral blood using ELISA and multiplex assays. Newborn and adult monocytes were differentiated into monocyte-derived dendritic cells (MoDCs) and TLR agonist-induced activation assessed by cytokine production (ELISA) and co-stimulatory molecule expression (flow cytometry). Results VTX-294 was ∼100x more active on TLR8- than TLR7-transfected HEK cells (EC50, ∼50 nM vs. ∼5700 nM). VTX-294-induced TNF and IL-1β production were comparable in newborn cord and adult peripheral blood, while VTX-294 was ∼ 1 log more potent in inducing TNF and IL-1β production than MPLA, R848 or CL075. Combination of VTX-294 and MPLA induced greater blood TNF and IL-1β responses than combination of R-848 and MPLA. VTX-294 also potently induced expression of cytokines and co-stimulatory molecules HLA-DR and CD86 in human newborn MoDCs. Conclusions VTX-294 is a novel ultra-potent TLR8 agonist that activates newborn and adult leukocytes and is a candidate vaccine adjuvant in both early life and adulthood.

Sex Differences in Plasmacytoid Dendritic Cell Levels of IRF5 Drive Higher IFN-α Production in Women.

Increased IFN-α production contributes to the pathogenesis of infectious and autoimmune diseases. Plasmacytoid dendritic cells (pDCs) from females produce more IFN-α upon TLR7 stimulation than pDCs from males, yet the mechanisms underlying this difference remain unclear. In this article, we show that basal levels of IFN regulatory factor (IRF) 5 in pDCs were significantly higher in females compared with males and positively correlated with the percentage of IFN-α–secreting pDCs. Delivery of recombinant IRF5 protein into human primary pDCs increased TLR7-mediated IFN-α secretion. In mice, genetic ablation of the estrogen receptor 1 (Esr1) gene in the hematopoietic compartment or DC lineage reduced Irf5 mRNA expression in pDCs and IFN-α production. IRF5 mRNA levels furthermore correlated with ESR1 mRNA levels in human pDCs, consistent with IRF5 regulation at the transcriptional level by ESR1. Taken together, these data demonstrate a critical mechanism by which sex differences in basal pDC IRF5 expression lead to higher IFN-α production upon TLR7 stimulation in females and provide novel targets for the modulation of immune responses and inflammation.

17(R)‐Resolvin D1 differentially regulates TLR4‐mediated responses of primary human macrophages to purified LPS and live E. coli

Detection and clearance of bacterial infection require balanced effector and resolution signals to avoid chronic inflammation. Detection of GNB LPS by TLR4 on mϕ induces inflammatory responses, contributing to chronic inflammation and tissue injury. LXs and Rvs are endogenous lipid mediators that enhance resolution of inflammation, and their actions on primary human mϕ responses toward GNB are largely uncharacterized. Here, we report that LXA4, LXB4, and RvD1, tested at 0.1–1 μM, inhibited LPS‐induced TNF production from primary human mϕ, with ATL and 17(R)‐RvD1, demonstrating potent inhibition at 0.1 μM. In addition, 17(R)‐RvD1 inhibited LPS‐induced primary human mϕ production of IL‐7, IL‐12p70, GM‐CSF, IL‐8, CCL2, and MIP‐1α without reducing that of IL‐6 or IL‐10. Remarkably, when stimulated with live Escherichia coli, mϕ treated with 17(R)‐RvD1 demonstrated increased TNF production and enhanced internalization and killing of the bacteria. 17(R)‐RvD1‐enhanced TNF, internalization, and killing were not evident for an lpxM mutant of E. coli expressing hypoacylated LPS with reduced inflammatory activity. Furthermore, 17(R)‐RvD1‐enhanced, E. coli‐induced TNF production was evident in WT but not TLR4‐deficient murine mϕ. Thus, Rvs differentially modulate primary human mϕ responses to E. coli in an LPS‐ and TLR4‐dependent manner, such that this Rv could promote resolution of GNB/LPS‐driven inflammation by reducing mϕ proinflammatory responses to isolated LPS and increasing mϕ responses important for clearance of infection.

Bactericidal/Permeability-Increasing Protein (rBPI21) and Fluoroquinolone Mitigate Radiation-Induced Bone Marrow Aplasia and Death

Even when given 24 hours after lethal radiation, a fragment of an endotoxin-neutralizing protein plus a fluoroquinolone antibiotic improves survival and hematopoietic recovery in mice. Reducing Risks of Radiation Radiation—intentional or not—kills dividing cells, dealing a double whammy to the body. The demise of dividing intestinal cells renders the gut leaky, letting microbes in and shuttling down the immune cell production line in the bone marrow, leaving the body extra susceptible to the invading microbes. In a new approach to treating these lethal effects of radiation, Guinan et al. deliver a double whammy of their own by combining an antibiotic and an inhibitor of dangerous microbial endotoxin to prevent death by radiation in mice. The dual drugs are effective when given 24 hours after the radiation, a boon for use in a disaster where immediate treatment might not be possible. The authors found a clue for this new approach to radiation mitigation by studying patients irradiated in preparation for a bone marrow transplant. Among the responses was a drop in serum concentrations of BPI (bactericidal/permeability-increasing protein), a protective protein that binds to lipopolysaccharide, which is shed by microbes and can cause severe lethal reactions in patients. They reasoned that replacing the declining BPI could be beneficial and tested this idea in mice. Although BPI alone did not help irradiated mice survive, when BPI was given together with an antibiotic, about 70 to 80% of the animals lived, whereas almost none of the untreated animals were alive after 20 days. The combined BPI/antibiotic therapy also caused a rebound in the number of cells in the bone marrow after their radiation-induced depletion. What makes this combo treatment particularly appealing is the fact that both BPI and the antibiotic have previously been used safely in humans, an important point when calculating the risk-benefit ratio of treating individuals whose exact dose of radiation may not be clear. With nontoxic agents, one can more comfortably treat someone who may have received a small dose. This advantage, plus the fact that, at least in mice, the BPI/antibiotic can be administered a full day after exposure and still be effective, suggests that this double-drug approach should be tested for use in humans. Identification of safe, effective treatments to mitigate toxicity after extensive radiation exposure has proven challenging. Only a limited number of candidate approaches have emerged, and the U.S. Food and Drug Administration has yet to approve any agent for a mass-casualty radiation disaster. Because patients undergoing hematopoietic stem cell transplantation undergo radiation treatment that produces toxicities similar to radiation-disaster exposure, we studied patients early after such treatment to identify new approaches to this problem. Patients rapidly developed endotoxemia and reduced plasma bactericidal/permeability-increasing protein (BPI), a potent endotoxin-neutralizing protein, in association with neutropenia. We hypothesized that a treatment supplying similar endotoxin-neutralizing activity might replace the BPI deficit and mitigate radiation toxicity and tested this idea in mice. A single 7-Gy radiation dose, which killed 95% of the mice by 30 days, was followed 24 hours later by twice-daily, subcutaneous injections of the recombinant BPI fragment rBPI21 or vehicle alone for 14 or 30 days, with or without an oral fluoroquinolone antibiotic with broad-spectrum antibacterial activity, including that against endotoxin-bearing Gram-negative bacteria. Compared to either fluoroquinolone alone or vehicle plus fluoroquinolone, the combined rBPI21 plus fluoroquinolone treatment improved survival, accelerated hematopoietic recovery, and promoted expansion of stem and progenitor cells. The observed efficacy of rBPI21 plus fluoroquinolone initiated 24 hours after lethal irradiation, combined with their established favorable bioactivity and safety profiles in critically ill humans, suggests the potential clinical use of this radiation mitigation strategy and supports its further evaluation.

Diminished Macrophage Apoptosis and Reactive Oxygen Species Generation after Phorbol Ester Stimulation in Crohn's Disease

Background Crohns Disease (CD) is a chronic relapsing disorder characterized by granulomatous inflammation of the gastrointestinal tract. Although its pathogenesis is complex, we have recently shown that CD patients have a systemic defect in macrophage function, which results in the defective clearance of bacteria from inflammatory sites. Methodology/Principal Findings Here we have identified a number of additional macrophage defects in CD following diacylglycerol (DAG) homolog phorbol-12-myristate-13-acetate (PMA) activation. We provide evidence for decreased DNA fragmentation, reduced mitochondrial membrane depolarization, impaired reactive oxygen species production, diminished cytochrome c release and increased IL-6 production compared to healthy subjects after PMA exposure. The observed macrophage defects in CD were stimulus-specific, as normal responses were observed following p53 activation and endoplasmic reticulum stress. Conclusion These findings add to a growing body of evidence highlighting disordered macrophage function in CD and, given their pivotal role in orchestrating inflammatory responses, defective apoptosis could potentially contribute to the pathogenesis of CD.

Innate immune activation in neonatal tracheal aspirates suggests endotoxin-driven inflammation

Background:Tracheal aspirates (TAs) from critically ill neonates accumulate bacterial endotoxin and demonstrate mobilization of endotoxin-binding proteins, but the potential bioactivity of endotoxin in TAs is unknown. We characterized innate immune activation in TAs of mechanically ventilated neonates.Methods:Innate immune activation in TAs of mechanically ventilated neonates was characterized using a targeted 84-gene quantitative real-time (qRT) PCR array. Protein expression of cytokines was confirmed by multiplex assay. Expression and localization of the endotoxin-inducible antimicrobial protein Calgranulin C (S100A12) was assessed by flow cytometry. Endotoxin levels were measured in TA supernatants using the Limulus amoebocyte lysate assay.Results:Analyses by qRT-PCR demonstrated expression of pattern recognition receptors, Toll-like receptor-nuclear factor κB and inflammasome pathways, cytokines/chemokines and their receptors, and anti-infective proteins in TA cells. Endotoxin positivity increased with postnatal age. As compared with endotoxin-negative TAs, endotoxin-positive TAs demonstrated significantly greater tumor necrosis factor (TNF), interleukin (IL)-6, IL-10, and serpin peptidase inhibitor, clade E, member 1 (SERPINE1) mRNA, and IL-10, TNF, and IL-1β protein. Expression of S100A12 protein was localized to TA neutrophils.Conclusion:Correlation of endotoxin with TA inflammatory responses suggests endotoxin bioactivity and the possibility that endotoxin antagonists could mitigate pulmonary inflammation and its sequelae in this vulnerable population.

Human immunodeficiency virus type 1 persistence following systemic chemotherapy for malignancy

Background Systemic chemotherapies for various malignancies have been shown to significantly, yet transiently, decrease numbers of CD4+ T lymphocytes, a major reservoir for human immunodeficiency virus type 1 (HIV-1) infection. However, little is known about the impact of cytoreductive chemotherapy on HIV-1 reservoir dynamics, persistence, and immune responses. Methods We investigated the changes in peripheral CD4+ T-cell-associated HIV-1 DNA and RNA levels, lymphocyte activation, viral population structure, and virus-specific immune responses in a longitudinal cohort of 15 HIV-1-infected individuals receiving systemic chemotherapy or subsequent autologous stem cell transplantation for treatment of hematological malignancies and solid tumors. Results Despite a transient reduction in CD4+ T cells capable of harboring HIV-1, a 1.7- and 3.3-fold increase in mean CD4+ T-cell-associated HIV-1 RNA and DNA, respectively, were observed months following completion of chemotherapy in individuals on antiretroviral therapy. We also observed changes in CD4+ T-cell population diversity and clonal viral sequence expansion during CD4+ T-cell reconstitution following chemotherapy cessation. Finally, HIV-1 DNA was preferentially, and in some cases exclusively, detected in cytomegalovirus (CMV)- and Epstein-Barr virus (EBV)-responsive CD4+ T cells following chemotherapy. Conclusions Expansion of HIV-infected CMV/EBV-specific CD4 + T cells may contribute to maintenance of the HIV DNA reservoir following chemotherapy.

Enhanced immune activation linked to endotoxemia in HIV-1 seronegative MSM.

This study assessed cellular and soluble markers of immune activation in HIV-1 seronegative MSM. MSM immune profiles were characterized by an increased expression of CD57 on T cells and endotoxemia. Endotoxin presence was linked to recent high-risk exposure and associated with elevated cytokine levels and decreased CD4+/CD8+ T cell ratios. Taken together, these data show elevated levels of inflammation linked to periods of endotoxemia resulting in a significantly different immune phenotype in a subset of MSM at a high risk of HIV-1 acquisition.

CCR5-Δ32 Heterozygosity, HIV-1 Reservoir Size, and Lymphocyte Activation in Individuals Receiving Long-term Suppressive Antiretroviral Therapy

We conducted a case-controlled study of the associations of CCR5-Δ32 heterozygosity with human immunodeficiency virus type 1 (HIV-1) reservoir size, lymphocyte activation, and CCR5 expression in 114 CCR5(Δ32/WT) and 177 wild-type CCR5 AIDS Clinical Trials Group participants receiving suppressive antiretroviral therapy. Overall, no significant differences were found between groups for any of these parameters. However, higher levels of CCR5 expression correlated with lower amounts of cell-associated HIV-1 RNA. The relationship between CCR5-Δ32 heterozygosity, CCR5 expression, and markers of HIV-1 persistence is likely to be complex and may be influenced by factors such as the duration of ART.