CRISPR Immunological Memory Requires a Host Factor for Specificity.

Bacteria and archaea employ adaptive immunity against foreign genetic elements using CRISPR-Cas systems. To generate immunological memory, the Cas1-Cas2 protein complex captures 30-40 base pair segments of foreign DNA and catalyzes their integration into the host genome as unique spacer sequences. Although spacers are inserted strictly at the A-T-rich leader end of CRISPR loci in vivo, the molecular mechanism of leader-specific spacer integration remains poorly understood. Here we show that the E. coli integration host factor (IHF) protein is required for spacer acquisition in vivo and for integration into linear DNA in vitro. IHF binds to the leader sequence and induces a sharp DNA bend, allowing the Cas1-Cas2 integrase to catalyze the first integration reaction at the leader-repeat border. Together, these results reveal that Cas1-Cas2-mediated spacer integration requires IHF-induced target DNA bending and explain the elusive role of CRISPR leader sequences during spacer acquisition.

Novel Circulating and Tissue Monocytes as Well as Macrophages in Pancreatitis and Recovery.

BACKGROUND AND AIMS: Acute pancreatitis (AP) is an inflammatory disease with mild to severe course that is associated with local and systemic complications and significant mortality. Uncovering inflammatory pathways that lead to progression and recovery will inform ways to monitor and/or develop effective therapies. METHODS: We performed single-cell mass Cytometry by Time Of Flight (CyTOF) analysis to identify pancreatic and systemic inflammatory signals during mild AP (referred to as AP), severe AP (SAP), and recovery using 2 independent experimental models and blood from patients with AP and recurrent AP. Flow cytometric validation of monocytes subsets identified using CyTOF analysis was performed independently. RESULTS: Ly6C+ inflammatory monocytes were the most altered cells in the pancreas during experimental AP, recovery, and SAP. Deep profiling uncovered heterogeneity among pancreatic and blood monocytes and identified 7 novel subsets during AP and recovery, and 6 monocyte subsets during SAP. Notably, a dynamic shift in pancreatic CD206+ macrophage population was observed during AP and recovery. Deeper profiling of the CD206+ macrophage identified 7 novel subsets during AP, recovery, and SAP. Differential expression analysis of these novel monocyte and CD206+ macrophage subsets revealed significantly altered surface (CD44, CD54, CD115, CD140a, CD196, podoplanin) and functional markers (interferon-γ, interleukin 4, interleukin 22, latency associated peptide-transforming growth factor-ß, tumor necrosis factor-α, T-bet, RoRγt) that were associated with recovery and SAP. Moreover, a targeted functional analysis further revealed distinct expression of pro- and anti-inflammatory cytokines by pancreatic CD206+ macrophage subsets as the disease either progressed or resolved. Similarly, we identified heterogeneity among circulating classical inflammatory monocytes (CD14+CD16-) and novel subsets in patients with AP and recurrent AP. CONCLUSIONS: We identified several novel monocyte/macrophage subsets with unique phenotype and functional characteristics that are associated with AP, recovery, and SAP. Our findings highlight differential innate immune responses during AP progression and recovery that can be leveraged for future disease monitoring and targeting.

RUNX1 loss renders hematopoietic and leukemic cells dependent on IL-3 and sensitive to JAK inhibition.

Disease-initiating mutations in the transcription factor RUNX1 occur as germline and somatic events that cause leukemias with particularly poor prognosis. However, the role of RUNX1 in leukemogenesis is not fully understood, and effective therapies for RUNX1-mutant leukemias remain elusive. Here, we used primary patient samples and a RUNX1-KO model in primary human hematopoietic cells to investigate how RUNX1 loss contributes to leukemic progression and to identify targetable vulnerabilities. Surprisingly, we found that RUNX1 loss decreased proliferative capacity and stem cell function. However, RUNX1-deficient cells selectively upregulated the IL-3 receptor. Exposure to IL-3, but not other JAK/STAT cytokines, rescued RUNX1-KO proliferative and competitive defects. Further, we demonstrated that RUNX1 loss repressed JAK/STAT signaling and rendered RUNX1-deficient cells sensitive to JAK inhibitors. Our study identifies a dependency of RUNX1-mutant leukemias on IL-3/JAK/STAT signaling, which may enable targeting of these aggressive blood cancers with existing agents.

Mass-Cytometry-Based Quantification of Global Histone Post-Translational Modifications at Single-Cell Resolution Across Peripheral Immune Cells in IBD.

BACKGROUND AND AIMS: Current understanding of histone post-translational modifications [histone modifications] across immune cell types in patients with inflammatory bowel disease [IBD] during remission and flare is limited. The present study aimed to quantify histone modifications at a single-cell resolution in IBD patients during remission and flare and how they differ compared to healthy controls. METHODS: We performed a case-control study of 94 subjects [83 IBD patients and 11 healthy controls]. IBD patients had either ulcerative colitis [n = 38] or Crohn's disease [n = 45] in clinical remission or flare. We used epigenetic profiling by time-of-flight [EpiTOF] to investigate changes in histone modifications within peripheral blood mononuclear cells from IBD patients. RESULTS: We discovered substantial heterogeneity in histone modifications across multiple immune cell types in IBD patients. They had a higher proportion of less differentiated CD34+ haematopoietic progenitors, and a subset of CD56bright natural killer [NK] cells and γδ T cells characterized by distinct histone modifications associated with gene transcription. The subset of CD56bright NK cells had increases in several histone acetylations. An epigenetically defined subset of NK cells was associated with higher levels of C-reactive protein in peripheral blood. CD34+ monocytes from IBD patients had significantly decreased cleaved H3T22, suggesting they were epigenetically primed for macrophage differentiation. CONCLUSION: We describe the first systems-level quantification of histone modifications across immune cells from IBD patients at a single-cell resolution, revealing the increased epigenetic heterogeneity that is not possible with traditional ChIP-seq profiling. Our data open new directions in investigating the association between histone modifications and IBD pathology using other epigenomic tools.

The effect of gastric acid suppression on probiotic colonization in a double blinded randomized clinical trial.

BACKGROUND & AIMS: Probiotics contain living microorganisms consumed for their putative benefits on the intestinal microbiota and general health and a concept is emerging to use probiotic as a therapeutic intervention to reduce proton pump inhibitors (PPIs) negative effects, but data is lacking. The use of PPIs can result in disordered gut microbiota, leading to a risk of enteric infections. PPIs are frequently prescribed in the general practice setting for gastroesophageal reflux disease (GERD), peptic ulcer disease, and related conditions. Despite the availability and widespread use of probiotics and acid-suppressing medications, the effect of PPIs-induced gastric acid suppression on the survival and colonization of probiotics bacterial species is currently unclear. We hypothesized that gastric acid suppression may improve intestinal colonization of probiotics bacterial species and probiotic intervention may have a potential role in mitigating untoward effects of PPI. METHODS: In a randomized, double-blind, placebo-controlled study, healthy subjects were given either proton pump inhibitor (PPI, n = 15) or placebo (n = 15) over 6 weeks. All subjects then consumed multi-strain probiotics from weeks 2-6. Thirty participants (10 males, 20 females, age range: 18-56 years) were enrolled in the study. Shotgun metagenomic sequencing and untargeted metabolomics analyses were performed on stool samples collected at week 0, 2, and 6. RESULTS: Short term PPI treatment increased the microbial abundance of Streptococcaceae (p = 0.004), Leuconostacaceae (p = 0.001), and Pasteurellaceae (p = 0.020) at family level and corresponding genus levels. The metabolomic analysis of the stools revealed a change in 10 metabolites where Gly Arg Val and phenylacetic acid were consistently increased compared to the baseline. Probiotic intervention inhibited PPI-induced microbial changes such as a decrease in Leuconostacaceae family (p = 0.01) and led to an increase in metabolite 1H-Indole-4-carbaldehyde. Notably, PPI enhanced the colonization of certain probiotic bacterial species like Streptococcus thermophilus (p < 0.05) along with other species present in the multi-strain probiotic. CONCLUSION: Acid suppression enhanced certain probiotic associated bacterial colonization and probiotics in turn suppressed PPI-mediated intestinal microbial alterations. Thus, probiotics in combination with PPI might be a beneficial strategy that allows probiotic colonization and suppress PPI-induced microbial perturbations. CLINICAL TRIALS. GOV, NUMBER: NCT03327051.

Computational drug repositioning of atorvastatin for ulcerative colitis.

OBJECTIVE: Ulcerative colitis (UC) is a chronic inflammatory disorder with limited effective therapeutic options for long-term treatment and disease maintenance. We hypothesized that a multi-cohort analysis of independent cohorts representing real-world heterogeneity of UC would identify a robust transcriptomic signature to improve identification of FDA-approved drugs that can be repurposed to treat patients with UC. MATERIALS AND METHODS: We performed a multi-cohort analysis of 272 colon biopsy transcriptome samples across 11 publicly available datasets to identify a robust UC disease gene signature. We compared the gene signature to in vitro transcriptomic profiles induced by 781 FDA-approved drugs to identify potential drug targets. We used a retrospective cohort study design modeled after a target trial to evaluate the protective effect of predicted drugs on colectomy risk in patients with UC from the Stanford Research Repository (STARR) database and Optum Clinformatics DataMart. RESULTS: Atorvastatin treatment had the highest inverse-correlation with the UC gene signature among non-oncolytic FDA-approved therapies. In both STARR (n = 827) and Optum (n = 7821), atorvastatin intake was significantly associated with a decreased risk of colectomy, a marker of treatment-refractory disease, compared to patients prescribed a comparator drug (STARR: HR = 0.47, P = .03; Optum: HR = 0.66, P = .03), irrespective of age and length of atorvastatin treatment. DISCUSSION & CONCLUSION: These findings suggest that atorvastatin may serve as a novel therapeutic option for ameliorating disease in patients with UC. Importantly, we provide a systematic framework for integrating publicly available heterogeneous molecular data with clinical data at a large scale to repurpose existing FDA-approved drugs for a wide range of human diseases.

Vitamin D Is Associated with α4ß7+ Immunophenotypes and Predicts Vedolizumab Therapy Failure in Patients with Inflammatory Bowel Disease.

BACKGROUND AND AIMS: Vitamin D downregulates the in vitro expression of the gut-tropic integrin α4ß7 on immune cells. The clinical relevance of this finding in patients with inflammatory bowel disease [IBD] is unclear. We tested the hypothesis that vitamin D is associated with α4ß7 immunophenotypes and risk of vedolizumab [anti-α4ß7] failure in IBD. METHODS: We performed single-cell immunophenotyping of peripheral and intestinal immune cells using mass cytometry [CyTOF] in vedolizumab-naïve patients with IBD [N = 48]. We analysed whole-genome mucosal gene expression [GSE73661] from GEMINI I and GEMINI long-term safety [LTS] to determine the association between vitamin D receptor [VDR] and integrin alpha-4 [ITGA4] and beta-7 [ITGB7] genes. We estimated the odds of vedolizumab failure with low pre-treatment vitamin D in a combined retrospective and prospective IBD cohort [N = 252] with logistic regression. RESULTS: Immunophenotyping revealed that higher 25[OH]D was associated with decreased α4ß7+ peripheral blood mononuclear cells [R = -0.400, p <0.01] and α4ß7+ intestinal leukocytes [R = -0.538, p = 0.03]. Serum 25[OH]D was inversely associated with α4ß7+ peripheral B cells and natural killer [NK] cells and α4ß7+ intestinal B cells, NK cells, monocytes, and macrophages. Mucosal expression of VDR was inversely associated with ITGA4 and ITGB7 expression. In multivariate analysis, 25[OH]D <25 ng/mL was associated with increased vedolizumab primary non-response during induction (odds ratio [OR] 26.10, 95% confidence interval [CI] 14.30-48.90, p <0.001) and failure at 1-year follow-up [OR 6.10, 95% CI 3.06-12.17, p <0.001]. CONCLUSIONS: Low serum 25[OH]D is associated with α4ß7+ immunophenotypes and predicts future vedolizumab failure in patients with IBD. PODCAST: This article has an associated podcast which can be accessed at https://academic.oup.com/ecco-jcc/pages/podcast.

Effects of processing conditions on stability of immune analytes in human blood.

Minimizing variability in collection and processing of human blood samples for research remains a challenge. Delaying plasma or serum isolation after phlebotomy (processing delay) can cause perturbations of numerous analytes. Thus, a comprehensive understanding of how processing delay affects major endpoints used in human immunology research is necessary. Therefore, we studied how processing delay affects commonly measured cytokines and immune cell populations. We hypothesized that short-term time delays inherent to human research in serum and plasma processing impact commonly studied immunological analytes. Blood from healthy donors was subjected to processing delays commonly encountered in sample collection, and then assayed by 62-plex Luminex panel, 40-parameter mass cytometry panel, and 540,000 transcript expression microarray. Variance for immunological analytes was estimated using each individual's baseline as a control. In general, short-term processing delay led to small changes in plasma and serum cytokines (range - 10.8 to 43.5%), markers and frequencies of peripheral blood mononuclear cell phenotypes (range 0.19 to 3.54 fold), and whole blood gene expression (stable for > 20 K genes)-with several exceptions described herein. Importantly, we built an open-access web application allowing investigators to estimate the degree of variance expected from processing delay for measurements of interest based on the data reported here.

Mass cytometry reveals systemic and local immune signatures that distinguish inflammatory bowel diseases.

Inflammatory bowel disease (IBD) includes Crohn's disease and ulcerative colitis. Each disease is characterized by a diverse set of potential manifestations, which determine patients' disease phenotype. Current understanding of phenotype determinants is limited, despite increasing prevalence and healthcare costs. Diagnosis and monitoring of disease requires invasive procedures, such as endoscopy and tissue biopsy. Here we report signatures of heterogeneity between disease diagnoses and phenotypes. Using mass cytometry, we analyze leukocyte subsets, characterize their function(s), and examine gut-homing molecule expression in blood and intestinal tissue from healthy and/or IBD subjects. Some signatures persist in IBD despite remission, and many signatures are highly represented by leukocytes that express gut trafficking molecules. Moreover, distinct systemic and local immune signatures suggest patterns of cell localization in disease. Our findings highlight the importance of gut tropic leukocytes in circulation and reveal that blood-based immune signatures differentiate clinically relevant subsets of IBD.

The Distinct and Cooperative Roles of Toll-Like Receptor 9 and Receptor for Advanced Glycation End Products in Modulating In Vivo Inflammatory Responses to Select CpG and Non-CpG Oligonucleotides.

Antisense oligonucleotides (ASOs) are widely accepted therapeutic agents that suppress RNA transcription. While the majority of ASOs are well tolerated in vivo, few sequences trigger inflammatory responses in absence of conventional CpG motifs. In this study, we identified non-CpG oligodeoxy-nucleotide (ODN) capable of triggering an inflammatory response resulting in B cell and macrophage activation in a MyD88- and TLR9-dependent manner. In addition, we found the receptor for advance glycation end product (RAGE) receptor to be involved in the initiation of inflammatory response to suboptimal concentrations of both CpG- and non-CpG-containing ODNs. In contrast, dosing RAGE KO mice with high doses of CpG or non-CpG ODNs lead to a stronger inflammatory response than observed in wild-type mice. Together, our data provide a previously uncharacterized in vivo mechanism contingent on ODN-administered dose, where TLR9 governs the primary response and RAGE plays a distinct and cooperative function in providing a pivotal role in balancing the immune response.