Tobias M. Nowacki

Translational 18F-FDG PET/CT Imaging to Monitor Lesion Activity in Intestinal Inflammation

In patients with inflammatory bowel disease (IBD) and in murine IBD models, mucosal disease activity is routinely assessed by endoscopy and histologic evaluation. This information is valuable for monitoring treatment response, with mucosal healing being a major treatment goal. The aim of this study was to evaluate the translational potential of noninvasive 18F-FDG PET/CT for the assessment of mucosal damage in murine dextran sodium sulfate (DSS) colitis and human IBD. Methods: After induction of DSS colitis, 18F-FDG uptake was serially assessed from colonic volumes of interest defined on PET/CT scans and intraindividually correlated to histologic findings and to infiltrating cell types. In addition, 18F-FDG PET/CT scans of 25 Crohn disease patients were analyzed, and colonic 18F-FDG uptake was correlated to endoscopically assessed damage. Results: At days 4 and 7 after DSS induction, colonic 18F-FDG uptake was significantly increased, with a distinct peak in the medial colon. 18F-FDG uptake strongly correlated with histologic epithelial damage. Additionally, 18F-FDG uptake increased in the bone marrow in the course of the disease, correlating with an increase in intestinal 18F-FDG uptake. Histology and fluorescence-activated cell sorting analysis of the bone marrow of DSS mice revealed an increased number of immature neutrophils, whereas mucosal polymerase chain reaction suggested a correlation of 18F-FDG uptake to T cell infiltration. In accordance with the results of 18F-FDG PET/CT in DSS colitis, an increased 18F-FDG uptake was found in 87% of deep mucosal ulcerations in IBD patients, whereas mild endoscopic lesions were detected only by 18F-FDG PET/CT in about 50% of patients assessed. Conclusion: 18F-FDG PET/CT is a noninvasive method for evaluation of both experimental colitis and Crohn disease patients and thereby offers promising translational potential.

Assessment of stricturing Crohn's disease: Current clinical practice and future avenues

Crohns disease (CD) is a chronic remittent idiopathic disease. Although the early phase of the disease is commonly characterized by inflammation-driven symptoms, such as diarrhea, the frequency of fibrostenotic complications in patients with CD increases over the long-term course of the disease. This review presents the current diagnostic options for assessing CD-associated strictures. In addition to the endoscopic evaluation of CD strictures, this review summarizes the currently available imaging modalities, including ultrasound and cross-sectional imaging techniques. In addition to stricture detection, differentiating between the primarily inflammatory strictures and the predominantly fibrotic ones is essential for selecting the appropriate treatment strategy (anti-inflammatory medical treatment vs endoscopical or surgical approaches). Therefore, recent imaging advances, such as contrast-enhanced ultrasound and ultrasound elastography, contribute to the development of non-invasive non-radiating imaging of CD-associated strictures. Finally, novel magnetic resonance imaging techniques, such as diffusion-weighted, motility and magnetization transfer imaging, as well as (18)F-FDG PET/CT, molecular imaging approaches and biomarkers, are critically reviewed with regard to their potential role in assessing stricturing CD.

Cytomegalovirus (CMV)-Specific Perforin and Granzyme B ELISPOT Assays Detect Reactivation of CMV Infection in Inflammatory Bowel Disease

The role of cytomegalovirus (CMV) infection in the pathogenesis and exacerbation of Inflammatory Bowel Disease (IBD) has been unresolved. Typically, the CMV genome remains dormant in infected cells, but a breakdown of immune surveillance can lead to re-activation of viral replication in the gut mucosa, which is not necessarily associated with viremia or changes in antibody titers. We hypothesized that the detection of CMV-specific CD8 effector T cells should permit the distinction between dormant and active CMV infection. As CD8 effector T cells, unlike memory CD8 T cells, have perforin (PFN) and granzyme B (GzB) preformed in their cytoplasmic granules, we employed single cell resolution ELISPOT assays to measure the CMV antigen-triggered release of these molecules by CD8 T cells isolated from subjects with IBD, and age-matched healthy controls. The frequencies of CMV-specific (GzB) and PFN-producing CD8 T cells were increased in IBD patients compared to healthy controls. Furthermore, the increased CMV reactivity was associated with active IBD disease and with longer disease duration. Notably, PCR on serum frequently failed to detect CMV DNA during flares. The data show that during active IBD there is a flare of CD8 T cell activity against CMV in a substantial proportion of IBD patients, suggesting CMV reactivation that serum PCR does not detect. While it remains open whether CMV reactivation is a cause or consequence of IBD, our data suggest that monitoring CMV antigen-specific effector CD8 T cells with GzB and PFN ELISPOT analysis can provide novel insights into the role of CMV infection in IBD. Additionally, our data have implications for the fields of transplantation, HIV, cancer, and autoimmune diseases, in all of which patient care critically depends on sensitive and reliable detection of a reactivation of CMV infection.

Murine endoscopy for in vivo multimodal imaging of carcinogenesis and assessment of intestinal wound healing and inflammation.

Mouse models are widely used to study pathogenesis of human diseases and to evaluate diagnostic procedures as well as therapeutic interventions preclinically. However, valid assessment of pathological alterations often requires histological analysis, and when performed ex vivo, necessitates death of the animal. Therefore in conventional experimental settings, intra-individual follow-up examinations are rarely possible. Thus, development of murine endoscopy in live mice enables investigators for the first time to both directly visualize the gastrointestinal mucosa and also repeat the procedure to monitor for alterations. Numerous applications for in vivo murine endoscopy exist, including studying intestinal inflammation or wound healing, obtaining mucosal biopsies repeatedly, and to locally administer diagnostic or therapeutic agents using miniature injection catheters. Most recently, molecular imaging has extended diagnostic imaging modalities allowing specific detection of distinct target molecules using specific photoprobes. In conclusion, murine endoscopy has emerged as a novel cutting-edge technology for diagnostic experimental in vivo imaging and may significantly impact on preclinical research in various fields.

Crohn's disease complicated by intestinal infection with methicillin-resistant Staphylococcus aureus.

We report on a 24-year-old male patient with history of bloody diarrhea, abdominal pain and vomiting. Endoscopy revealed massive ulcerative discontinuous proctosigmoiditis with deep, sharply demarcated epithelial denudations and enterotoxigenic methicillin-resistant Staphylococcus aureus (MRSA) was detected in mucosal biopsies. After treatment with linezolide and steroids, a significant amelioration of colitis was detected and testing for MRSA became negative. In face of the case presented here, we suggest that in patients with refractory inflammatory bowel disease (IBD), microbiological assessment should be performed to detect a possible Staphylococcus aureus infection in order to initiate an antimicrobial treatment in addition to IBD-specific treatment.

Nicotinamide treatment ameliorates the course of experimental colitis mediated by enhanced neutrophil-specific antibacterial clearance

SCOPE In previous studies, we could show that the B vitamin nicotinamide (NAM) enhanced antimicrobial activity of neutrophils. Here, we assessed the effects of NAM in two models of experimental colitis. METHODS AND RESULTS Colitis was induced in C57BL/6 mice either by oral infection with Citrobacter rodentium or by DSS (dextran sodium sulphate) administration, and animals were systemically treated with NAM. Ex vivo bacterial clearance was assessed in murine and human whole blood, as well as isolated human neutrophils. In C. rodentium-induced colitis, NAM treatment resulted in markedly decreased systemic bacterial invasion, histological damage and increased fecal clearance of C. rodentium by up to 600-fold. In contrast, NAM had no effect when administered to neutrophil-depleted mice. Ex vivo stimulation of isolated human neutrophils, as well as murine and human whole blood with NAM led to increased clearance of C. rodentium and enhanced expression of antimicrobial peptides in neutrophils. Moreover, NAM treatment significantly ameliorated the course of DSS colitis, as assessed by body weight, histological damage and myeloperoxidase activity. CONCLUSION Pharmacological application of NAM mediates beneficial effects in bacterial and chemically induced colitis. Future studies are needed to explore the clinical potential of NAM in the context of intestinal bacterial infections and human inflammatory bowel disease (IBD).

Direct peroral cholangioscopy with a new anchoring technique using the guide probe of Kautz – first clinical experiences

Background and study aims We present the first clinical results of a new tandem technique for direct peroral cholangioscopy using a standard ultraslim upper gastrointestinal endoscope and a guide probe that was originally developed for the non-transendoscopic placement of biliary endoprostheses (guide probe of Kautz; MTW, Wesel, Germany). Patients and methods Twenty direct peroral cholangioscopy procedures were performed with the new anchor-assisted method using the guide probe of Kautz in a single center and were retrospectively analyzed. Results  Indications for anchor-assisted cholangioscopy procedures included indeterminate bile duct strictures (n = 14), filling defects that remained after stone extraction (n = 4), and complex stone extractions (n = 2). Biliary access and visualization of the target region were achieved in 18/20 procedures (90 %). The interventional success rate was 85 % (11 /13 interventions). One case of postinterventional cholangitis occurred (5 %), along with one case of minor peri-interventional papillary bleeding (5 %). Conclusions The anchor-assisted cholangioscopy technique is feasible and safe for direct cholangioscopy and provides reliable success rates in clinical practice. This technique represents an alternative approach for direct cholangioscopy on a single-operator basis using standard endoscopes.

Safety, diagnostic accuracy and therapeutic efficacy of digital single-operator cholangioscopy:

Background Digital single-operator cholangioscopes (digital SOCs), equipped with an improved image quality, have been recently introduced. Objective The aim of this study is to evaluate the safety and diagnostic and therapeutic efficacy of digital SOCs (Spyglass™ DS). Methods Sixty-seven digital SOC procedures performed between 2015 and 2017 were retrospectively analyzed. Results The most frequent indications for examination were indeterminate biliary strictures (61.2%) and biliary stone disease (23.9%). In 25 patients (37.3), visual findings predicted malignancy with a sensitivity of 88.9%, a specificity of 97.6%, a positive predictive value (PPV) of 96.0% and a negative predictive value (NPV) of 92.9%. For histological analysis, forceps biopsies were performed in 29 patients (43.2%). Compared with visual findings, forceps biopsies yield a lower diagnostic efficacy in diagnosing malignancy (sensitivity 62.5%, specificity 90.0%, PPV 90.9%, NPV 60.0%). Therapeutic interventions were performed in 19 patients with a technical success rate of 89.4%. Adverse events were observed in 17 patients (25.4%). Of these, 11 patients (16.4%) suffered from severe adverse events (pancreatitis, cholangitis or major bleeding), which led to a prolonged hospital stay. Conclusion Digital SOCs have excellent diagnostic and therapeutic efficacies, but are accompanied by high rates of adverse events; therefore, physicians should use digital SOCs in carefully selected cases.

Direct Detection of T- and B-Memory Lymphocytes by ImmunoSpot® Assays Reveals HCMV Exposure that Serum Antibodies Fail to Identify

It is essential to identify donors who have not been infected with human cytomegalovirus (HCMV) in order to avoid transmission of HCMV to recipients of blood transfusions or organ transplants. In the present study, we tested the reliability of seronegativity as an indicator for the lack of HCMV exposure in healthy human blood donors. Eighty-two HCMV seronegative individuals were identified, and their peripheral blood mononuclear cells (PBMC) were tested in ImmunoSpot® assays for the presence of HCMV-specific T- and B-memory lymphocytes. Eighty-two percent (67 of 82) of these HCMV seronegative individuals featured at least one memory cell that was lineage specific for HCMV, with the majority of these subjects possessing CD4+ and CD8+ T cells, as well as B cells, providing three independent lines of evidence for having developed immunity to HCMV. Only 15 of these 82 donors (18%) showed neither T- nor B-cell memory to HCMV, consistent with immunological naïveté to the virus. The data suggest that measurements of serum antibodies frequently fail to reveal HCMV exposure in humans, which may be better identified by direct detection of HCMV-specific memory lymphocytes.

The 5A apolipoprotein A-I (apoA-I) mimetic peptide ameliorates experimental colitis by regulating monocyte infiltration

New therapies for inflammatory bowel disease (IBD) are highly desirable. As apolipoprotein (apo)A‐I mimetic peptides are beneficial in several animal models of inflammation, we hypothesized that they might be effective at inhibiting murine colitis.