Sean Studer

A review of lung transplant donor acceptability criteria

Abstract (A consensus report from The Pulmonary Council of the International Society for Heart and Lung Transplantation)

COPII and the regulation of protein sorting in mammals

Secretory proteins are transported to the Golgi complex in vesicles that bud from the endoplasmic reticulum. The cytoplasmic coat protein complex II (COPII) is responsible for cargo sorting and vesicle morphogenesis. COPII was first described in Saccharomyces cerevisiae, but its basic function is conserved throughout all eukaryotes. Nevertheless, the COPII coat has adapted to the higher complexity of mammalian physiology, achieving more sophisticated levels of secretory regulation. In this review we cover aspects of mammalian COPII-mediated regulation of secretion, in particular related to the function of COPII paralogues, the spatial organization of cargo export and the role of accessory proteins.

A 2010 working formulation for the standardization of definitions of infections in cardiothoracic transplant recipients

Shahid Husain, MD, MS, Martha L. Mooney, MD, MS, FACP, Lara Danziger-Isakov, MD, MPH, Frauke Mattner, MD, PhD, Nina Singh, MD, Robin Avery, MD, FIDSA, Michael Ison, MD, MS, Atul Humar, MD, MSc, Robert F. Padera, MD, PhD, Leo P. Lawler, MD, FRCR, Andy Fisher, PhD, FRCP, Richard J. Drew, MD, Kate F. Gould, MBBS, MRCP, FRCP, Amparo Sole, MD, PhD, Sean Studer, MD, MSc, Patricia Munoz, MD, Lianne G. Singer, MD, FRCPC, and Margaret Hannan, MD, FRCP, FRCPath, for the ISHLT Infectious Diseases Council Working Group on Definitions From the Division of Infectious Diseases, Transplant Infectious Diseases, University Health Network, University of Toronto, Toronto, Ontario, Canada; Eastern Virginia Medical School, Sentara Norfolk Transplant Center, Norfolk, Virginia; Center for Pediatric Infectious Diseases, Department of Infectious Disease, Medicine Institute, The Cleveland Clinic, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio; Infection Control and Hospital Epidemiology, Institute for Medical Microbiology, Hannover Medical School, Hannover, Germany; Division of Infectious Diseases, Veteran Affairs Hospital, University of Pittsburgh, Pittsburgh, Pennsylvania; Divisions of Infectious Diseases and Organ Transplantation, Northwestern University, Feinberg School of Medicine, Chicago, Illinois; Department of Medicine, Division of Infectious Diseases, University of Alberta, Edmonton, Alberta, Canada; Department of Pathology, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts; Respiratory Transplant Medicine, Newcastle University, Institute of Transplantation, Freeman Hospital, Newcastle Upon Tyne, UK; Mater Misericordiae University Hospital, Dublin, Ireland; Health Protection Agency Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle, UK; Hospital Universitario La Fe, Valencia, Spain; Division of Pulmonary & Critical Care, Newark Beth Israel Medical Center, Newark, New Jersey; and Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Maranon, Universidad Complutense, Madrid, Spain.

S1P signaling: new therapies and opportunities.

Development of sphingosine-1-phosphate receptor 1 (S1P1) modulators to dampen inflammation and its sequelae is becoming increasingly promising for treating medical conditions characterized by significant immunopathology. As shown by the non-selective S1P receptor modulator FTY720 (fingolimod [Gilenya®]) in the treatment of relapsing-remitting multiple sclerosis (MS), the ability to use S1P1 modulation to precisely block immune cell traffic—immunomodulation—while maintaining immunosurveillance, has opened therapeutic opportunities in various other immune-derived chronic pathologies, including inflammatory bowel disease (IBD), lupus, psoriasis, as well as, potentially, in early acute viral respiratory infection. Proof-of-concept studies across validated animal models with S1P receptor modulators highly selective for S1P1, such as BAF-312 (Siponimod), KRP-203, ONO-4641 (Ceralifimod), ponesimod and RPC-1063, and emerging clinical trials for safety and efficacy in humans, particularly in MS, ulcerative colitis (UC) and psoriasis, have set the stage for us to consider additional testing in various other autoimmune diseases.

Elevated Pulmonary Artery Pressure Is a Risk Factor for Primary Graft Dysfunction Following Lung Transplantation for Idiopathic Pulmonary Fibrosis

BACKGROUND Idiopathic pulmonary fibrosis (IPF) is often associated with elevations in pulmonary artery pressures. Although primary pulmonary arterial hypertension (PAH) has been associated with primary graft dysfunction (PGD), the role of secondary PAH in mediating PGD risk in patients with IPF is incompletely understood. The purpose of this study was to evaluate the relationship between mean pulmonary artery pressure (mPAP) and PGD among patients with IPF. METHODS We performed a multicenter prospective cohort study of 126 lung transplant procedures performed for IPF between March 2002 and August 2007. The primary outcome was grade 3 PGD at 72 h after lung transplant. The mPAP was measured as the initial reading following insertion of the right-sided heart catheter during lung transplant. Multivariable logistic regression was used to adjust for confounding variables. RESULTS The mPAP for patients with PGD was 38.5 ± 16.3 mm Hg vs 29.6 ± 11.5 mm Hg for patients without PGD (mean difference, 8.9 mm Hg [95% CI, 3.6-14.2]; P = .001). The increase in odds of PGD associated with each 10-mm Hg increase in mPAP was 1.64 (95% CI, 1.18-2.26; P = .003). In multivariable models, this relationship was independent of confounding by other clinical variables, although the use of cardiopulmonary bypass partially attenuated the relationship. CONCLUSIONS Higher mPAP in patients with IPF is associated with the development of PGD.

Five-year outcomes with alemtuzumab induction after lung transplantation

BACKGROUND Induction therapy with alemtuzumab, followed by lower than conventional intensity post-transplant immunosuppression (eg, tacrolimus monotherapy), has been associated with reduced morbidity and mortality in abdominal and heart transplantation. We examined 5-year outcomes in lung recipients receiving alemtuzumab in conjunction with reduced-intensity post-transplant immunosuppression (early lower-dose tacrolimus; lower-dose steroids, with or without mycophenolate mofetil), compared with lung recipients receiving other induction agents or no induction in association with post-transplant immunosuppression. METHODS A retrospective analysis was performed using prospectively collected data from a single-site clinical database of 336 lung recipients (aged ≥ 18) who received allografts between 1998 and 2005, classified by induction type: alemtuzumab, 127; Thymoglobulin, 43; daclizumab, 73; and none, 93. Survival analyses examined patient and graft survival, and freedom from acute cellular rejection (ACR), lymphocytic bronchiolitis, obliterative bronchiolitis (OB), bronchiolitis obliterans syndrome (BOS), and post-transplant lymphoproliferative disorder (PTLD). RESULTS Five-year patient and graft survival differed by group (p = 0.046, p = 0.038, respectively). Alemtuzumab patient/graft survival rates were 59%/59%. Survival rates were 60%/44% for Thymoglobulin, 47%/46% for no induction, and 44%/41% for daclizumab. Freedom from ACR, lymphocytic bronchiolitis, OB, and BOS differed by group (all values, p < 0.008); alemtuzumab recipients showed greater 5-year freedom from each outcome (30%/82%/86%/54%) than Thymoglobulin (20%/54%/62%/27%), daclizumab (19%/55%/70%/43%), and no-induction groups (18%/70%/69%/46%). The groups did not differ in PTLD rates (≥ 94% free of PTLD at 5 years; p = 0.864). Effects were unchanged after controlling for potential covariates. CONCLUSIONS Alemtuzumab induction may be associated with improved outcomes in lung transplantation. Randomized controlled trials are needed to establish any effects of this agent.

Understanding the impact of pulmonary arterial hypertension on patients' and carers' lives

Pulmonary arterial hypertension (PAH) is a rare, debilitating and rapidly progressive disease. Although there have been important medical advances in PAH management, the search for a cure continues. Despite an increased understanding of the disease, data on the wider effect of PAH on patients and carers, beyond the clinical symptoms, are still limited. In order to explore this, a large-scale international survey investigated four key areas affected by PAH (physical and practical, emotional, social, and information needs) and provides new insight into patients’ and carers’ experiences of living with the disease. The results from the survey highlight not only the limited ability of patients to carry out everyday tasks, but also the financial impact and social isolation experienced by both patients and carers. The study confirmed that a decline in a patient’s World Health Organization functional class, which indicates an increase in clinical severity of the disease, is associated with greater limitations. Results from the survey demonstrate the need for multidisciplinary PAH management and a comprehensive standard of care to assess and improve all aspects of well-being for both patients and carers. In addition, they underline the need for updated PAH guidelines that address these needs.

The use of an early alert system to improve compliance with sepsis bundles and to assess impact on mortality.

Introduction. Diagnostic and therapeutic guidelines, organized as sepsis bundles, have been shown to improve mortality, but timely and consistent implementation of these can be challenging. Our study examined the use of a screening tool and an early alert system to improve bundle compliance and mortality. Methods. A screening tool was used to identify patients with severe sepsis or septic shock and an overhead alert system known as Code SMART (Sepsis Management Alert Response Team) was activated at the physicians discretion. Data was collected for 6 months and compliance with bundle completion and mortality were compared between the Code SMART and non-Code SMART groups. Results. Fifty eight patients were enrolled −34 Code SMART and 24 non-Code SMART. The Code SMART group achieved greater compliance with timely antibiotic administration (P < 0.001), lactate draw (P < 0.001), and steroid use (P = 0.02). Raw survival and survival adjusted for age, leucopenia, and severity of illness scores, were greater in the Code SMART group (P < 0.05, P = 0.03, and P = 0.01). Conclusions. A screening tool and an alert system can improve compliance with sepsis bundle elements and improve survival from severe sepsis and septic shock.

S1PR1-mediated IFNAR1 degradation modulates plasmacytoid dendritic cell interferon-α autoamplification.

Significance The sphingosine 1-phosphate receptor (S1PR1) is known to act by multiple mechanisms: limiting lymphocyte egress from secondary lymphoid organs, suppressing proinflammatory endothelial cell function, and acting directly on neurons and astrocytes. Here, we report that sphingosine 1-phosphate (S1P)-S1PR1 signaling in plasmacytoid dendritic cells (pDCs) directly inhibits IFN-α autoamplification by induced degradation of the interferon alpha receptor 1 (IFNAR1) receptor and suppression of signal transducer and activator of transcription 1 (STAT1) signaling. An endosomal regulatory interaction of a lipid G-protein coupled receptor (GPCR) and IFNAR1 balances effective and detrimental components of immune responses and provides a previously unidentified pathway that contributes to significant and unexpected efficacy in clinical trials in multiple sclerosis, ulcerative colitis, psoriasis, and likely other diseases with aberrant IFN-α signatures. Blunting immunopathology without abolishing host defense is the foundation for safe and effective modulation of infectious and autoimmune diseases. Sphingosine 1-phosphate receptor 1 (S1PR1) agonists are effective in treating infectious and multiple autoimmune pathologies; however, mechanisms underlying their clinical efficacy are yet to be fully elucidated. Here, we uncover an unexpected mechanism of convergence between S1PR1 and interferon alpha receptor 1 (IFNAR1) signaling pathways. Activation of S1PR1 signaling by pharmacological tools or endogenous ligand sphingosine-1 phosphate (S1P) inhibits type 1 IFN responses that exacerbate numerous pathogenic conditions. Mechanistically, S1PR1 selectively suppresses the type I IFN autoamplification loop in plasmacytoid dendritic cells (pDCs), a specialized DC subset, for robust type I IFN release. S1PR1 agonist suppression is pertussis toxin-resistant, but inhibited by an S1PR1 C-terminal–derived transactivating transcriptional activator (Tat)-fusion peptide that blocks receptor internalization. S1PR1 agonist treatment accelerates turnover of IFNAR1, suppresses signal transducer and activator of transcription 1 (STAT1) phosphorylation, and down-modulates total STAT1 levels, thereby inactivating the autoamplification loop. Inhibition of S1P-S1PR1 signaling in vivo using the selective antagonist Ex26 significantly elevates IFN-α production in response to CpG-A. Thus, multiple lines of evidence demonstrate that S1PR1 signaling sets the sensitivity of pDC amplification of IFN responses, thereby blunting pathogenic immune responses. These data illustrate a lipid G-protein coupled receptor (GPCR)-IFNAR1 regulatory loop that balances effective and detrimental immune responses and elevated endogenous S1PR1 signaling. This mechanism will likely be advantageous in individuals subject to a range of inflammatory conditions.

The Structure of Sec12 Implicates Potassium Ion Coordination in Sar1 Activation

Background: Sec12 is a GEF responsible for the initiation of COPII vesicle budding. Results: The 1.36 Å crystal structure of yeast Sec12 is presented, together with in vitro and in vivo analysis of structure-guided mutants. Conclusion: A potassium-stabilized “K loop” plays an unprecedented and critical role in GEF activity. Significance: All of the key proteins for COPII vesicle budding have now been structurally characterized. Coat protein II (COPII)-coated vesicles transport proteins and lipids from the endoplasmic reticulum to the Golgi. Crucial for the initiation of COPII coat assembly is Sec12, a guanine nucleotide exchange factor responsible for activating the small G protein Sar1. Once activated, Sar1/GTP binds to endoplasmic reticulum membranes and recruits COPII coat components (Sec23/24 and Sec13/31). Here, we report the 1.36 Å resolution crystal structure of the catalytically active, 38-kDa cytoplasmic portion of Saccharomyces cerevisiae Sec12. Sec12 adopts a β propeller fold. Conserved residues cluster around a loop we term the “K loop,” which extends from the N-terminal propeller blade. Structure-guided site-directed mutagenesis, in conjunction with in vitro and in vivo functional studies, reveals that this region of Sec12 is catalytically essential, presumably because it makes direct contact with Sar1. Strikingly, the crystal structure also reveals that a single potassium ion stabilizes the K loop; bound potassium is, moreover, essential for optimum guanine nucleotide exchange activity in vitro. Thus, our results reveal a novel role for a potassium-stabilized loop in catalyzing guanine nucleotide exchange.