bluuebunny/crossref_metadata_2025_split huggingface dataset:
Implication of Telomerase in Functions Besides Telomere Elongation in Human Cells
Authors: Gazzaniga Francesca , Lin Jue , Blackburn Elizabeth 
Published: October 2019

Abstract
Abstract SCI-40
The ribonucleoprotein enzyme telomerase, which counteracts telomere shortening by adding telomeric DNA repeats to the 3’ ends of chromosomes, contains a core protein reverse transcriptase (called hTERT in humans), the essential template-containing RNA (hTER) and associated factors. Thus, telomerase is capable of circumventing the limit on cell division imposed by telomere attrition. Telomerase enzymatic activity is readily detectable in stem and progenitor cell populations, but is largely downregulated in most adult somatic human cells. In contrast, telomerase is highly active in the large majority (∼80%–90%) of cancer cells. While telomerase is essential for telomere maintenance in cells in vitro and in vivo, several studies now also indicate that telomerase may have telomere-independent functions. We previously showed that lowering the level of the telomerase ribonucleoprotein (RNP) enzyme complex causes rapid changes in cell cycle program in human and mouse cancer cells: partial reduction of telomerase induced by directly lowering telomerase RNP component levels causes altered transcriptional profiles and reduced glucose metabolism in human cancer cells, yet bulk telomere shortening or detectable telomere uncapping are not required for these effects. Work by others has shown that reduction of telomerase core protein component level reduced Wnt signaling and caused Wnt-mutant like developmental defects in Xenopus and mouse and aberrant hematopoiesis in zebrafish embryos. We acutely depleted telomerase RNA components in cultured T cells from healthy human adults using shRNAs targeting both the telomerase protein and the RNA component of telomerase (hTR), delivered immediately after in vitro stimulation. Cell proliferation and telomerase activity levels were quantified through the first and second stimulation cycles. Effects of such telomerase RNP reduction on cell proliferation were observed in time frames too short to be accounted for by bulk telomere attrition. Models to account for these findings will be discussed.

Disclosures:
Lin: Telome Health, Inc.: Consultancy, Equity Ownership. Blackburn:Telome Health, Inc: Equity Ownership, Membership on an entity’s Board of Directors or advisory committees.
Challenges in Design and Development of PAR Inhibitors
Authors: Andrade-Gordon Patricia 
Published: October 2019

Abstract
Abstract SCI-45
Inappropriate and sustained activation of platelets is a major cause of vascular occlusive diseases such as angina, myocardial infarction, and stroke. The development of thrombi within blood vessels results from the formation of platelet aggregates and fibrin deposits, and heavily depends on the actions of α-thrombin. It is now well recognized that human platelet responses to α-thrombin are mediated by the protease-activated receptors PAR1 and PAR4. Protease-activated receptors (PARs) represent a unique family of seven-transmembrane G-protein-coupled receptors, which are enzymatically cleaved to expose a new extracellular N-terminus that acts as a “tethered” activating ligand. Since the discovery of PAR1 as the major contributor to human platelet aggregation, there has been a keen interest to develop antagonist as potential antithrombotics. However, there have been many issues and challenges in this endeavor. One crucial challenge to the discovery of potent antagonists is the strong entropy advantage offered by the intramolecular binding mechanism of PARs activation, which presents a great disadvantage to a circulating small molecule antagonist. To be an effective therapeutic agent, a PAR1 antagonist not only should bind tightly to the receptor but also possess suitable binding kinetics. Another issue for the discovery of PAR1 antagonists is the preclinical logistics associated with species variability of PAR1 on platelets. Despite these challenges, PAR1 has been an attractive drug target and there has been considerable activity and progress in the discovery and development of PAR1 antagonist as therapeutic agents. The promise of these novel therapeutics is reflected by two antiplatelet PAR1 antagonists in advanced clinical trials. The clinical benefits derived from these agents will be determined by the tight balance between delivering efficacy in the context of thrombotic disease and controlling the bleeding risk. The discussion will focus on the challenges from discovery to development of these great potential opportunities in the prevention of atherothrombotic disease.

Disclosures:
Andrade-Gordon: Johnson & Johnson: Employment.
Genetics of Intestinal Graft-Versus-Host Disease
Authors: van den Brink Marcel R.M. 
Published: October 2019

Abstract SCI-51
Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an important therapy with curative potential for a variety of malignant and nonmalignant diseases. Despite standard prophylactic regimens, graft-versus-host disease (GVHD) continues to limit the success of outcomes in allo-HSCT patients. Gastrointestinal (GI) GVHD is the predominant contributor to acute GVHD-related mortality. The pathophysiology of GI GVHD has unique features that are related to the important interactions between the donor allograft (especially donor alloreactive T cells), mucosal adaptive and innate intestinal immunity, intestinal epithelial homeostasis, and the intestinal microbial flora. The pathophysiology of intestinal GVHD has many similarities with inflammatory bowel disease (IBD), such as Crohn’s disease and ulcerative colitis (UC). At last count, 99 susceptibility loci/genes for Crohn’s and UC have been published. Multiple genes are involved in IL-23/Th17 signaling, defective processing of intracellular bacteria involving autophagy and innate immunity (including NOD2 and ATG16L1), and defects in barrier function and shared susceptibility with other autoimmune diseases (such as type 1 and 2 DM). Early studies in mice and in patients suggested a link between an individual’s intestinal microbial flora and his/her propensity for GVHD resulting in varying protocols for gut decontamination, which continue at some centers to this date. We will discuss the latest data regarding the role in intestinal GVHD of genetic changes in the before-mentioned pathways and genes in the donor and host, as well as its interactions with the intestinal flora.

Disclosures:
No relevant conflicts of interest to declare.
Hydroxyurea Is Associated with Lower Prevalence of Albuminuria in Adults with Sickle Cell Disease
Authors: Laurin Louis-Philippe , Nachman Patrick H. , Desai Payal C. , Ataga Kenneth I. , Derebail Vimal K. 
Published: October 2019

Abstract
Abstract 3211

Background:
Albuminuria is an early manifestation of sickle cell disease (SCD) nephropathy, denoting glomerular injury. Minimal clinical data exist on the association of hydroxyurea (HU) use with albuminuria in adults with SCD.

Methods:
A cross-sectional study was performed to evaluate the association of HU with the prevalence of albuminuria among adults with SCD using clinical data collected from 2000 to 2011. HU exposure was defined as ≥3 months of therapy prior to assessment of albuminuria. Albuminuria was defined as a urinary albumin-to-creatinine ratio (UACR) ≥30 mg/g and/or ≥1+ proteinuria on two dipstick measurements at least 2 months apart. A multivariate logistic regression model was constructed from univariate analyses and with covariates previously identified to be associated with albuminuria in SCD, including history of acute chest syndrome, angiotensin-converting enzyme inhibitor/angiotensin receptor blocker (ACEi/ARB) use, age, and elevated tricuspid regurgitation jet velocity (TRV). Backward elimination of covariates was used to produce the most parsimonious model.

Results:
149 adult patients (mean age 38±13 years; 113 with HbSS, 10 HbSß0, 7 HbSß1, 18 HbSC, and 1 HbSD) were included. The prevalence of albuminuria was lower among patients on HU therapy than those not on HU [26/75 (34.7%) vs. 41/74 (55.4%); p=0.01]. Among 112 patients with a measured UACR, median albumin excretion was lower in patients on HU [17.9 (6.0–53.0) vs. 40.5 (7.0–204.9) mg/g; p=0.04]. In univariate analyses, ACEi/ARBuse, hemoglobin level and percent reticulocytes were also related to albuminuria. By multivariate logistic regression model, HU use was associated with a lower risk of albuminuria (odds ratio 0.31, 95% CI 0.12 to 0.81; p=0.02), adjusting for age, ACEi/ARB use, TRV ≥2.5 m/s, systemic hypertension and history of acute chest syndrome.

Conclusion:
The use of HU was associated with lower prevalence of albuminuria, after controlling for age, ACEi/ARB use, TRV ≥2.5 m/s, systemic hypertension and history of acute chest syndrome. Based upon these findings, the potential of HU to prevent overt nephropathy or the progression of SCD nephropathy to end-stage renal disease merits further investigation.

Disclosures:
No relevant conflicts of interest to declare.
An Elevated TRV Is Associated with Venous Thromboembolism in Sickle Cell Disease
Authors: Adams Rachel M , Kopel Lianne S , Bland Demedrick Anton , Klings Elizabeth S 
Published: October 2019

Abstract
Abstract 3222

Objective:
An elevated tricuspid regurgitant jet velocity (TRV) by echocardiography, used to screen for pulmonary hypertension (PH) and mortality in sickle cell disease (SCD), likely has a multi-factorial etiology. SCD is a hyper-coagulable state, yet, the contribution of venous thromboembolic disease (VTE) to an elevated TRV is unknown. Based on the known association between VTE and PH, we hypothesized that SCD patients with an elevated TRV will have an increased prevalence of VTE.

Methods:
We reviewed data collected prospectively as part of the PH in SCD study conducted at Boston University/Boston Medical Center from 2004–2010. Subjects were included if they underwent both echocardiography and testing for VTE. An elevated TRV was defined as > 2.5 m/sec or the presence of PH on right heart catheterization. A history of VTE was defined by a positive CT/angiogram, ventilation/perfusion scan or Duplex ultrasound of an extremity (not catheter-related). Data were analyzed using a Chi-Square test and an odds ratio for VTE was calculated.

Results:
We reviewed the records of 162 patients enrolled in the PH of SCD study; 97 underwent both echocardiography and an evaluation for VTE.5/53 patients (9.4%) with normal echocardiography had a history of VTE, compared with 13/44 (29.5%) in the elevated TRV group. SCD patients with an elevated TRV were four times more likely to have a history of VTE compared to those with a normal echocardiogram (OR: 4.03, 95% CI 1.31–12.41, p=0.011). There was no significant difference in age, gender, history of asthma, hemoglobin genotype, hematologic profiles or renal function between patient groups.

Conclusion:
An elevated TRV and PH are associated with a history of VTE in SCD patients. This suggests a role for thrombosis in disease modulation and underscores the need for a complete evaluation for VTE in SCD patients with an elevated TRV.

Disclosures:
No relevant conflicts of interest to declare.
Characterization of the Two Populations of NK-Like CD56+ T Cells and KIR+ T Cells in Human
Authors: Chan Wing Keung , Rujkijyanont Piya , Neale Geoffrey A. , Yang Jie , Bari Rafijul , Gupta Neha Das , Holladay Martha , Rooney Barbara , Wendt Susanne , Leung Wing 
Published: October 2019

Abstract
Abstract 3292
Previous studies have demonstrated that many T cell subsets possess NK-like features, including the CD56+ and KIR+ populations. Collectively, these studies showed that these NK-like T cells are predominantly αβ+ CD8+ with memory phenotype and could recognize HLA-E associated viral peptides after expansion upon TCR engagement. However, their clonality, transcriptome, regulation, specificity, and memory response in human have not been fully elucidated. We hypothesize that these NK-like T cells are phenotypically and functionally distinct from conventional T and NK cells and they play unique roles in virus and cancer control. Herein, we extensively characterized the CD56+ T cells and the KIR+ T subset by analysis of TREC, TCRVβ spectrum, telomere length, surface biomarkers, genome-wide transcriptome, multi-analyte cytokine profiling, cancer cell susceptibility, tetramer staining, and real-time response to CMV reactivation in stem cell transplant recipients. In contrast to CD56– T cells, CD56+ T cells are limited in TREC, TCRVβ, telomere length, cytokine secretion, transcription of metabolic genes stx6, nnt, galnt2, hvcn1, tyms, rpa1 tmf1, ecop, and tspan3, and are mostly KIR+, CD8+, DNAM1+, NKG2D+, CD44+, NKp46– and CD25–. Compared to KIR– CD56+ T cells, KIR+ CD56+ T cells are even more limited in TREC, TCRVβ, telomere length, and cytokine secretion, but have elevated transcription of NK cytotoxicity-related genes arrb1, ppp3cc, and lamc3, higher degranulation after activation by IL-2/IL-15 and CD3/CD28 antibodies, better killing of cancer cells after cytokine priming, and are mostly KIR2DL2/3+, NKG2D+, NKp46+, CD16+, NKG2C+, CD57+, and 2B4+. Importantly during CMV reactivation after stem cell transplantation, the percentage of KIR+ CD56+ T cells in the patient's blood increased dramatically and was significantly higher (p=0.0021) than in those without viral reactivation. Ex vivo, KIR+ CD56+ T cells demonstrate CMVpp65 tetramer staining, memory response to CMV peptides, and potent lysis of CMVpp65-pulsed target cells dependent on both KIR and TCR specificity. Furthermore, we identified for the first time that KIR– CD56+ T cells are Rorc+ IL-13-secretor. In conclusion, both CD56+ and KIR+ NK-like T-cell subsets are unique in biological and clinical properties and have distinct roles in cancer and infection control.

Disclosures:
No relevant conflicts of interest to declare.
Role of PDGF/PDGFR in Regulation of Thrombopoiesis: A Possible Explanation for Imatinib Mesylate-Induced Thrombocytopenia in the Treatment of CML
Authors: Yang Mo , Meng Fanyi , Ye Jie yu , Xu Yue , Xiao Bin , Chong Beng 
Published: October 2019

Abstract
Abstract 3348
Platelet-derived growth factor (PDGF), a platelet alpha-granule molecule, imply their potential effect in the regulation of megakaryocytopoiesis and thrombopoiesis, which also intimates the existence of an autocrine and/or paracrine loop constructed by megakaryocytes/platelets and their granular constituents. Our previous studies demonstrated the presence of functional PDGF receptors (PDGFR) on human megakaryocytes and platelets (Yang et al, Thromb Haemastasis, 1997) and CD34+ cells, and their ability to mediate a mitogenic response. PDGF promoted the ex vivo expansion of human hematopoietic stem (CD34+) and progenitor (CD41+ CD61+) cells. More significantly, PDGF enhanced the engraftment of human CD45+ cells and their myeloid subsets (CD33+, CD14+ cells) in NOD/SCID mice. PDGF stimulated in vitro megakaryocytopoiesis via PDGFR and/or the indirect effect on bone marrow microenvironment to produce TPO and other cytokines. It also showed a direct stimulatory effect of PDGF on c-Fos, GATA-1 and NF-E2 expressions in megakaryocytes. We speculate that these transcription factors might be involved in the signal transduction of PDGF on the regulation of megakaryocytopoiesis. PDGF also enhanced platelet recovery in mice model with radiation-induced thrombocytopenia. Studies showed that PDGF, like thrombopoietin (TPO), significantly promoted platelet recovery and the formation of bone marrow colony-forming unit-megakaryocyte (CFU-MK) in this irradiated-mouse. An increased number of hematopoietic stem/progenitor cells and a reduction of apoptosis were found in the bone marrow histology sections. In the M-07e apoptotic model, PDGF had a similar anti-apoptotic effect as TPO on megakaryocytes. We also demonstrated that PDGF activated the PI3k/Akt signaling pathway, while addition of imatinib mesylate reduced p-Akt expression. Our findings suggested that the PDGF-initiated radioprotective effect is likely to be mediated via PDGF receptors with subsequent activation of the PI3k/Akt pathway. The study provides a possible explanation that blockage of PDGFR may reduce thrombopoiesis and play a role in imatinib mesylate-induced thrombocytopenia in the treatment of CML.

Disclosures:
No relevant conflicts of interest to declare.
Development of a Factor VIII-Specific Immunotherapy for Hemophilia A
Authors: Naumann Anja , Kahle Jörg , Reiss Nadia , Schwabe Dirk , Heller Christine , Klingebiel Thomas , Königs Christoph 
Published: October 2019

Abstract
Abstract 3361
The development of neutralizing allo-antibodies against coagulation factor VIII (FVIII) is currently the most serious complication for hemophilia A patients that undergo FVIII replacement therapy. Non-hemophiliacs can spontaneously develop inhibitory auto-antibodies to FVIII, which results in a condition called acquired hemophilia A. The control of the allo- or autoimmune response to FVIII apparently includes the elicitation of an anti-idiotypic immune response. Immune tolerance induction (ITI) by frequent administration of high doses of FVIII is successful in most patients. The remaining up to 20% failing ITI face increased morbidity and mortality.
To elucidate the capacity of single-chain variable antibody fragments (scFvs) for neutralization of inhibitory anti-FVIII antibodies (FVIII inhibitors), scFvs that specifically interact with strong inhibitory murine monoclonal anti-human FVIII antibodies (anti-hFVIII mAbs) were selected by screening synthetic scFv phage displayed libraries. Since the majority of inhibitory anti-hFVIII mAbs are directed against the FVIII A2 or C2 domain, selection of scFvs was performed for two anti-A2 and two anti-C2 mAbs. Affinity selection identified several specific, potential anti-idiotypic scFvs for each anti-hFVIII mAb, which were further analyzed. ScFvs expressed as IgG fusion protein bind to mAbs with affinities up to 0,1nM. Binding of mAbs to immobilized FVIII was inhibited via specific scFvs by more than 90%. In the functional Bethesda Assay FVIII activity was fully restored when corresponding anti-idiotypic scFvs were added to plasma spiked with FVIII-specific mAbs. In addition, the cross-reactivity of scFvs with heterologous mAbs specific for A2 and C2 was tested and confirmed the exclusive interaction of the selected scFvs with their respective mAb.
Overall, anti-idiotypic scFvs specific for anti-hFVIII mAbs can be successfully selected from phage displayed libraries and efficiently neutralize FVIII inhibitors. ScFv anti-idiotypes may therefore facilitate the development of specific immunotherapies for hemophilia patients with inhibitors.

Disclosures:
No relevant conflicts of interest to declare.
F8 and HLA-II Haplotypes in the Hispanic Population: Implications for Inhibitor Risk Development in Hispanic Hemophilia A Patients
Authors: Kim Benjamin , Sauna Zuben E. , Carless Melanie A. , Curran Joanne E. , Viel Kevin R. , Cole Shelley S. , Raja Rajalingam , Blangero John , Howard Tom E. 
Published: October 2019

Abstract
Abstract 3365

Background:
A recent study suggested an increased rate of inhibitor development among Hispanic compared to White hemophilia A (HA) patients; however, a possible mechanism was not proposed or explored. In light of findings implicating a role for race-specific distributions of factor VIII (F8) and class-II human-leukocyte antigen (HLA-II) haplotypes on the disparate risk of inhibitor development in the Black HA population, we sought to determine the distributions of F8 and HLA-II haplotypes among Hispanic Americans and compare them to that of Black and White Americans.

Methods:
Using archived genomic DNA samples from the 194 unrelated founders of the San Antonio Family Heart Study (SAFHS), a collection of 1431 people from 41 large Mexican American families, we re-sequenced all exons of F8 to genotype the known nonsynonymous-single nucleotide polymorphisms (ns-SNPs) and identify any novel ns-SNPs. We then performed high-resolution HLA-II genotyping to identify each founders' pair of HLA-DRB1 alleles to compare them against those found in other ethnic groups.

Results:
Among the 291 potentially distinct Mexican American X-chromosomes evaluated, we identified the H2 F8 haplotype, defined by D1241E, in 25.0% of the subjects, which is in between that observed in the White (7.4%) and Black (37.4%) populations. We also found H3 F8, defined by D1241E and M2238V, in two subjects, who represent the first non-Black individuals reported to carry this haplotype. Furthermore, we discovered a previously unreported ns-SNP (H1919N), whose minor allele was found in only one male and defines a ninth wild-type F8 haplotype (H9). Regarding HLA-II alleles, the distribution among Mexican Americans in the present study was quite different from those found in Black and White individuals in the National Marrow Donor Program registry (see Figure). Three of the 4 most common HLA-II alleles in the Mexican Americans (DRB1*0802, DRB1*0407 and DRB1*1406) were seen in < 1% of both Blacks and Whites.

Discussion:
This is the first study to report the haplotypic prevalence of F8 and HLA-II alleles in Mexican Americans, the largest Hispanic ethnic group in the United States. By informing specific wild-type factor VIII (FVIII) peptides for use in HLA-II binding and T-cell stimulation assays, these results may help to identify high risk combinations of FVIII therapeutics and individual HLA-II repertoires that contribute to the higher rate of inhibitor development observed in Mexican versus Caucasian American HA patients.

Disclosures:
Viel: Histonis, Incorporated: Employment. Howard:Haplomics, Inc.: Equity Ownership.