Gut-associated lymphoid tissue attrition associates with response to anti-α4β7 therapy in ulcerative colitis

Vedolizumab (VDZ) is a first-line treatment in ulcerative colitis (UC) that targets the α4β7- mucosal vascular addressin cell adhesion molecule 1 (MAdCAM-1) axis. To determine the mechanisms of action of VDZ, we examined five distinct cohorts of patients with UC. A decrease in naïve B and T cells in the intestines and gut-homing (β7+) plasmablasts in circulation of VDZ-treated patients suggested that VDZ targets gut-associated lymphoid tissue (GALT). Anti-α4β7 blockade in wild-type and photoconvertible (KikGR) mice confirmed a loss of GALT size and cellularity because of impaired cellular entry. In VDZ-treated patients with UC, treatment responders demonstrated reduced intestinal lymphoid aggregate size and follicle organization and a reduction of β7+IgG+ plasmablasts in circulation, as well as IgG+ plasma cells and FcγR-dependent signaling in the intestine. GALT targeting represents a previously unappreciated mechanism of action of α4β7-targeted therapies, with major implications for this therapeutic paradigm in UC.

Extracellular Vesicle-Encapsulated Adeno-Associated Viruses for Therapeutic Gene Delivery to the Heart

BACKGROUND

Adeno-associated virus (AAV) has emerged as one of the best tools for cardiac gene delivery due to its cardiotropism, long-term expression, and safety. However, a significant challenge to its successful clinical use is preexisting neutralizing antibodies (NAbs), which bind to free AAVs, prevent efficient gene transduction, and reduce or negate therapeutic effects. Here we describe extracellular vesicle-encapsulated AAVs (EV-AAVs), secreted naturally by AAV-producing cells, as a superior cardiac gene delivery vector that delivers more genes and offers higher NAb resistance.

METHODS

We developed a 2-step density-gradient ultracentrifugation method to isolate highly purified EV-AAVs. We compared the gene delivery and therapeutic efficacy of EV-AAVs with an equal titer of free AAVs in the presence of NAbs, both in vitro and in vivo. In addition, we investigated the mechanism of EV-AAV uptake in human left ventricular and human induced pluripotent stem cell-derived cardiomyocytes in vitro and mouse models in vivo using a combination of biochemical techniques, flow cytometry, and immunofluorescence imaging.

RESULTS

Using cardiotropic AAV serotypes 6 and 9 and several reporter constructs, we demonstrated that EV-AAVs deliver significantly higher quantities of genes than AAVs in the presence of NAbs, both to human left ventricular and human induced pluripotent stem cell-derived cardiomyocytes in vitro and to mouse hearts in vivo. Intramyocardial delivery of EV-AAV9-sarcoplasmic reticulum calcium ATPase 2a to infarcted hearts in preimmunized mice significantly improved ejection fraction and fractional shortening compared with AAV9-sarcoplasmic reticulum calcium ATPase 2a delivery. These data validated NAb evasion by and therapeutic efficacy of EV-AAV9 vectors. Trafficking studies using human induced pluripotent stem cell-derived cells in vitro and mouse hearts in vivo showed significantly higher expression of EV-AAV6/9-delivered genes in cardiomyocytes compared with noncardiomyocytes, even with comparable cellular uptake. Using cellular subfraction analyses and pH-sensitive dyes, we discovered that EV-AAVs were internalized into acidic endosomal compartments of cardiomyocytes for releasing and acidifying AAVs for their nuclear uptake.

CONCLUSIONS

Together, using 5 different in vitro and in vivo model systems, we demonstrate significantly higher potency and therapeutic efficacy of EV-AAV vectors compared with free AAVs in the presence of NAbs. These results establish the potential of EV-AAV vectors as a gene delivery tool to treat heart failure.

Myeloid cell influx into the colonic epithelium is associated with disease severity and non-response to anti-Tumor Necrosis Factor Therapy in patients with Ulcerative Colitis

Ulcerative colitis (UC) is an idiopathic chronic inflammatory disease of the colon with sharply rising global prevalence. Dysfunctional epithelial compartment (EC) dynamics are implicated in UC pathogenesis although EC-specific studies are sparse. Applying orthogonal high-dimensional EC profiling to a Primary Cohort (PC; n=222), we detail major epithelial and immune cell perturbations in active UC. Prominently, reduced frequencies of mature BEST4+OTOP2+ absorptive and BEST2+WFDC2+ secretory epithelial enterocytes were associated with the replacement of homeostatic, resident TRDC+KLRD1+HOPX+ γδ+ T cells with RORA+CCL20+S100A4+ TH17 cells and the influx of inflammatory myeloid cells. The EC transcriptome (exemplified by S100A8, HIF1A, TREM1, CXCR1) correlated with clinical, endoscopic, and histological severity of UC in an independent validation cohort (n=649). Furthermore, therapeutic relevance of the observed cellular and transcriptomic changes was investigated in 3 additional published UC cohorts (n=23, 48 and 204 respectively) to reveal that non-response to anti-Tumor Necrosis Factor (anti-TNF) therapy was associated with EC related myeloid cell perturbations. Altogether, these data provide high resolution mapping of the EC to facilitate therapeutic decision-making and personalization of therapy in patients with UC.

Gut-associated lymphoid tissue attrition associates with response to anti-α4β7 therapy in ulcerative colitis

Targeting the α4β7-MAdCAM-1 axis with vedolizumab (VDZ) is a front-line therapeutic paradigm in ulcerative colitis (UC). However, mechanism(s) of action (MOA) of VDZ remain relatively undefined. Here, we examined three distinct cohorts of patients with UC (n=83, n=60, and n=21), to determine the effect of VDZ on the mucosal and peripheral immune system. Transcriptomic studies with protein level validation were used to study drug MOA using conventional and transgenic murine models. We found a significant decrease in colonic and ileal naïve B and T cells and circulating gut-homing plasmablasts (β7+) in VDZ-treated patients, pointing to gut-associated lymphoid tissue (GALT) targeting by VDZ. Murine Peyer's patches (PP) demonstrated a significant loss cellularity associated with reduction in follicular B cells, including a unique population of epithelium-associated B cells, following anti-α4β7 antibody (mAb) administration. Photoconvertible (KikGR) mice unequivocally demonstrated impaired cellular entry into PPs in anti-α4β7 mAb treated mice. In VDZ-treated, but not anti-tumor necrosis factor-treated UC patients, lymphoid aggregate size was significantly reduced in treatment responders compared to non-responders, with an independent validation cohort further confirming these data. GALT targeting represents a novel MOA of α4β7-targeted therapies, with major implications for this therapeutic paradigm in UC, and for the development of new therapeutic strategies.

Limited intestinal inflammation despite diarrhea, fecal viral RNA and SARS-CoV-2-specific IgA in patients with acute COVID-19

Gastrointestinal symptoms are common in COVID-19 patients but the nature of the gut immune response to SARS-CoV-2 remains poorly characterized, partly due to the difficulty of obtaining biopsy specimens from infected individuals. In lieu of tissue samples, we measured cytokines, inflammatory markers, viral RNA, microbiome composition, and antibody responses in stool samples from a cohort of 44 hospitalized COVID-19 patients. SARS-CoV-2 RNA was detected in stool of 41% of patients and more frequently in patients with diarrhea. Patients who survived had lower fecal viral RNA than those who died. Strains isolated from stool and nasopharynx of an individual were the same. Compared to uninfected controls, COVID-19 patients had higher fecal levels of IL-8 and lower levels of fecal IL-10. Stool IL-23 was higher in patients with more severe COVID-19 disease, and we found evidence of intestinal virus-specific IgA responses associated with more severe disease. We provide evidence for an ongoing humeral immune response to SARS-CoV-2 in the gastrointestinal tract, but little evidence of overt inflammation.

Intestinal Host Response to SARS-CoV-2 Infection and COVID-19 Outcomes in Patients With Gastrointestinal Symptoms

BACKGROUND & AIMS

Given that gastrointestinal (GI) symptoms are a prominent extrapulmonary manifestation of COVID-19, we investigated intestinal infection with SARS-CoV-2, its effect on pathogenesis, and clinical significance.

METHODS

Human intestinal biopsy tissues were obtained from patients with COVID-19 (n = 19) and uninfected control individuals (n = 10) for microscopic examination, cytometry by time of flight analyses, and RNA sequencing. Additionally, disease severity and mortality were examined in patients with and without GI symptoms in 2 large, independent cohorts of hospitalized patients in the United States (N = 634) and Europe (N = 287) using multivariate logistic regressions.

RESULTS

COVID-19 case patients and control individuals in the biopsy cohort were comparable for age, sex, rates of hospitalization, and relevant comorbid conditions. SARS-CoV-2 was detected in small intestinal epithelial cells by immunofluorescence staining or electron microscopy in 15 of 17 patients studied. High-dimensional analyses of GI tissues showed low levels of inflammation, including down-regulation of key inflammatory genes including IFNG, CXCL8, CXCL2, and IL1B and reduced frequencies of proinflammatory dendritic cells compared with control individuals. Consistent with these findings, we found a significant reduction in disease severity and mortality in patients presenting with GI symptoms that was independent of sex, age, and comorbid illnesses and despite similar nasopharyngeal SARS-CoV-2 viral loads. Furthermore, there was reduced levels of key inflammatory proteins in circulation in patients with GI symptoms.

CONCLUSIONS

These data highlight the absence of a proinflammatory response in the GI tract despite detection of SARS-CoV-2. In parallel, reduced mortality in patients with COVID-19 presenting with GI symptoms was observed. A potential role of the GI tract in attenuating SARS-CoV-2-associated inflammation needs to be further examined.

Effectiveness and safety of dolutegravir two-drug regimens in virologically suppressed people living with HIV: a systematic literature review and meta-analysis of real-world evidence

Objectives

Dolutegravir (DTG) is widely recommended within three‐drug regimens. However, similar efficacy and tolerability have also been achieved with DTG within two‐drug regimens in clinical trials. This study evaluated the real‐world effectiveness and discontinuations in people living with HIV‐1 (PLHIV) switching to DTG with lamivudine (3TC) or rilpivirine (RPV).

Methods

This was a one‐arm meta‐analysis utilizing data from a systematic literature review. Data from real‐world evidence studies of DTG + RPV and DTG + 3TC were extracted, pooled and analysed. The primary outcome was the proportion of patients with viral failure (VF; ≥ 50 copies/mL in two consecutive measurements and/or ≥ 1000 copies/mL in a single measurement) at week 48 (W48) and week 96 (W96). Other outcomes included virological suppression (VS; < 50 copies/mL) and discontinuations (W48 and W96). Estimates were calculated for VF, VS as per snapshot (VSS) and on treatment analysis (VSOT), and discontinuations.

Results

Pooled mean estimates of VF for DTG + 3TC and DTG + RPV were 0.8% [95% confidence interval (CI): 0.4–1.3] and 0.6% (95% CI: 0.0–1.6), respectively, at W48. VSS rate at W48 was 85.0% (95% CI: 82.3–87.5) for DTG + 3TC regimen and 92.4% (95% CI: 85.0–97.7) in the DTG + RPV regimen. The DTG + 3TC and DTG + RPV regimens led to discontinuations in 13.6% (95% CI: 11.1–16.2) and 7.2% (95% CI: 2.1–14.4) of patients, respectively, at W48. Similar results were observed at W96.

Conclusions

Treatment with DTG + 3TC or DTG + RPV in clinical practice provides a low rate of VF and a high rate of VS when initiated in virologically suppressed PLHIV with diverse backgrounds.

Evolution of Antibody Immunity to SARS-CoV-2

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has infected 78 million individuals and is responsible for over 1.7 million deaths to date. Infection is associated with development of variable levels of antibodies with neutralizing activity that can protect against infection in animal models. Antibody levels decrease with time, but the nature and quality of the memory B cells that would be called upon to produce antibodies upon re-infection has not been examined. Here we report on the humoral memory response in a cohort of 87 individuals assessed at 1.3 and 6.2 months after infection. We find that IgM, and IgG anti-SARS-CoV-2 spike protein receptor binding domain (RBD) antibody titers decrease significantly with IgA being less affected. Concurrently, neutralizing activity in plasma decreases by five-fold in pseudotype virus assays. In contrast, the number of RBD-specific memory B cells is unchanged. Memory B cells display clonal turnover after 6.2 months, and the antibodies they express have greater somatic hypermutation, increased potency and resistance to RBD mutations, indicative of continued evolution of the humoral response. Analysis of intestinal biopsies obtained from asymptomatic individuals 4 months after coronavirus disease-2019 (COVID-19) onset, using immunofluorescence, or polymerase chain reaction, revealed persistence of SARS-CoV-2 nucleic acids and immunoreactivity in the small bowel of 7 out of 14 volunteers. We conclude that the memory B cell response to SARS-CoV-2 evolves between 1.3 and 6.2 months after infection in a manner that is consistent with antigen persistence.

Intestinal Inflammation Modulates the Expression of ACE2 and TMPRSS2 and Potentially Overlaps With the Pathogenesis of SARS-CoV-2-related Disease

BACKGROUND AND AIMS

The presence of gastrointestinal symptoms and high levels of viral RNA in the stool suggest active severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) replication within enterocytes.

METHODS

Here, in multiple, large cohorts of patients with inflammatory bowel disease (IBD), we have studied the intersections between Coronavirus Disease 2019 (COVID-19), intestinal inflammation, and IBD treatment.

RESULTS

A striking expression of ACE2 on the small bowel enterocyte brush border supports intestinal infectivity by SARS-CoV-2. Commonly used IBD medications, both biologic and nonbiologic, do not significantly impact ACE2 and TMPRSS2 receptor expression in the uninflamed intestines. In addition, we have defined molecular responses to COVID-19 infection that are also enriched in IBD, pointing to shared molecular networks between COVID-19 and IBD.

CONCLUSIONS

These data generate a novel appreciation of the confluence of COVID-19- and IBD-associated inflammation and provide mechanistic insights supporting further investigation of specific IBD drugs in the treatment of COVID-19. Preprint doi: https://doi.org/10.1101/2020.05.21.109124.

Limited intestinal inflammation despite diarrhea, fecal viral RNA and SARS-CoV-2-specific IgA in patients with acute COVID-19

We sought to characterize the role of the gastrointestinal immune system in the pathogenesis of the inflammatory response associated with COVID-19. We measured cytokines, inflammatory markers, viral RNA, microbiome composition and antibody responses in stool from a cohort of 44 hospitalized COVID-19 patients. SARS-CoV-2 RNA was detected in stool of 41% of patients and more frequently in patients with diarrhea. Patients who survived had lower fecal viral RNA than those who died. Strains isolated from stool and nasopharynx of an individual were the same. Compared to uninfected controls, COVID-19 patients had higher fecal levels of IL-8 and lower levels of fecal IL-10. Stool IL-23 was higher in patients with more severe COVID-19 disease, and we found evidence of intestinal virus-specific IgA responses associated with more severe disease. We provide evidence for an ongoing humeral immune response to SARS-CoV-2 in the gastrointestinal tract, but little evidence of overt inflammation.

Gastrointestinal involvement attenuates COVID-19 severity and mortality

Given that gastrointestinal (GI) symptoms are a prominent extrapulmonary manifestation of coronavirus disease 2019 (COVID-19), we investigated intestinal infection with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and its effect on disease pathogenesis. SARS-CoV-2 was detected in small intestinal enterocytes by immunofluorescence staining or electron microscopy, in 13 of 15 patients studied. High dimensional analyses of GI tissues revealed low levels of inflammation in general, including active downregulation of key inflammatory genes such as IFNG, CXCL8, CXCL2 and IL1B and reduced frequencies of proinflammatory dendritic cell subsets. To evaluate the clinical significance of these findings, examination of two large, independent cohorts of hospitalized patients in the United States and Europe revealed a significant reduction in disease severity and mortality that was independent of gender, age, and examined co-morbid illnesses. The observed mortality reduction in COVID-19 patients with GI symptoms was associated with reduced levels of key inflammatory proteins including IL-6, CXCL8, IL-17A and CCL28 in circulation but was not associated with significant differences in nasopharyngeal viral loads. These data draw attention to organ-level heterogeneity in disease pathogenesis and highlight the role of the GI tract in attenuating SARS-CoV-2-associated inflammation with related mortality benefit.

ONE SENTENCE SUMMARY

Intestinal infection with SARS-CoV-2 is associated with a mild inflammatory response and improved clinical outcomes.

FTO-Dependent N6-Methyladenosine Regulates Cardiac Function During Remodeling and Repair

BACKGROUND

Despite its functional importance in various fundamental bioprocesses, studies of N⁶-methyladenosine (m6A) in the heart are lacking. Here, we show that the FTO (fat mass and obesity-associated protein), an m6A demethylase, plays a critical role in cardiac contractile function during homeostasis, remodeling, and regeneration.

METHODS

We used clinical human samples, preclinical pig and mouse models, and primary cardiomyocyte cell cultures to study the functional role of m6A and FTO in the heart and in cardiomyocytes. We modulated expression of FTO by using adeno-associated virus serotype 9 (in vivo), adenovirus (both in vivo and in vitro), and small interfering RNAs (in vitro) to study its function in regulating cardiomyocyte m6A, calcium dynamics and contractility, and cardiac function postischemia. We performed methylated (m6A) RNA immunoprecipitation sequencing to map transcriptome-wide m6A, and methylated (m6A) RNA immunoprecipitation quantitative polymerase chain reaction assays to map and validate m6A in individual transcripts, in healthy and failing hearts, and in myocytes.

RESULTS

We discovered that FTO has decreased expression in failing mammalian hearts and hypoxic cardiomyocytes, thereby increasing m6A in RNA and decreasing cardiomyocyte contractile function. Improving expression of FTO in failing mouse hearts attenuated the ischemia-induced increase in m6A and decrease in cardiac contractile function. This is performed by the demethylation activity of FTO, which selectively demethylates cardiac contractile transcripts, thus preventing their degradation and improving their protein expression under ischemia. In addition, we demonstrate that FTO overexpression in mouse models of myocardial infarction decreased fibrosis and enhanced angiogenesis.

CONCLUSIONS

Collectively, our study demonstrates the functional importance of the FTO-dependent cardiac m6A methylome in cardiac contraction during heart failure and provides a novel mechanistic insight into the therapeutic mechanisms of FTO.

Numerical simulations of NMR relaxation in chalk using local Robin boundary conditions

The interpretation of nuclear magnetic resonance (NMR) data is of interest in a number of fields. In Ögren (2014) local boundary conditions for random walk simulations of NMR relaxation in digital domains were presented. Here, we have applied those boundary conditions to large, three-dimensional (3D) porous media samples. We compared the random walk results with known solutions and then applied them to highly structured 3D domains, from images derived using synchrotron radiation CT scanning of North Sea chalk samples. As expected, there were systematic errors caused by digitalization of the pore surfaces so we quantified those errors, and by using linear local boundary conditions, we were able to significantly improve the output. We also present a technique for treating numerical data prior to input into the ESPRIT algorithm for retrieving Laplace components of time series from NMR data (commonly called T-inversion).

Abstract 326: FTO-mediated mRNA Demethylation Regulates Cardiac Contractile Protein Expression and Function

Background: Exciting new discoveries in RNA biology underscore the importance of post-transcriptional chemical modifications to mRNAs (epitranscriptome) in regulating RNA stability, nuclear export, cellular compartmentalization, splicing, translation and degradation. The most abundant and functionally relevant modification in RNA, N6-methyladenosine (m6A) is reversibly demethylated by one of the m6A demethylases, fat mass and obesity-associated protein (FTO) whose function in the mammalian heart remains incompletely understood.

Materials and Methods: We used clinical human samples, preclinical pig and mouse models and primary cardiomyocytes to study m6A and FTO in the heart and in cardiomyocytes. We modulated FTO expression using AAV9 (in vivo), adenovirus (in vivo and in vitro) and siRNAs (in vitro). We investigated m6A-induced changes to contractile protein expression using m6A RNA immunoprecipitation sequencing (MeRIP-seq) and stable isotope labeling of amino acids in cell culture (SILAC).

Results: We discovered in human heart failure that reduced FTO expression is associated with aberrant increase in m6A mRNA methylation, which is conserved in swine and mouse models of myocardial ischemia (MI). AAV9-mediated FTO gene delivery in mouse MI attenuated m6A increase and improved cardiac function with enhanced contractility, angiogenesis and reduced fibrosis. At the molecular level, FTO-mediated mRNA demethylation serves to increase contractile protein expression in mouse hearts as well as in isolated primary cardiomyocytes. By comparing human and mouse transcriptome-wide m6A maps with SILAC proteomic profiling from cardiomyocytes, we identified FTO-mediated m6A demethylation is transcript-specific and leads to altered protein expression of several key contractile, angiogenic and regenerative proteins.

Conclusion: Using new RNA-based investigations, we uncovered a novel regulatory layer beyond the genome working at the level of epitranscriptome governing cardiac function. Our findings on the dynamic nature of the cardiac m6A-epitranscriptome will lead to deeper understanding of the mechanism of cardiac remodeling on one hand and innovative therapeutic interventions on the other.

Abstract 170: Exosomal AAV-mediated SERCA2a Gene Transfer Improves Cardiac Function in a Mouse Model of Heart Failure

Adeno-associated viruses (AAVs) are promising therapeutic tools for gene delivery to the heart. However, pre-existing antibodies (NAbs) to many cardiotropic AAV serotypes naturally present in humans pose a critical challenge for the translation of gene therapies to clinical applications. Here, we describe the use of exosomal AAVs (eAAV) as a robust heart gene delivery system that improves transduction efficiency while protecting from pre-existing immunity to the viral capsid. To obtain eAAV specimens from conditioned medium from AAV-producing HEK-293T cells, we have developed a state-of-the-art multi-step ultracentrifugation strategy. We demonstrated through electron microscopy-based visualization, size distribution measurements and distribution of AAV genomes in post-centrifugation iodixanol gradients, that our purification process enables isolation of eAAVs with high purity and minimal contamination with standard AAVs. Efficiency of heart targeting was then evaluated for eAAV9 or eAAV6 and standard AAV9 or AAV6 in human cardiomyocytes (hCMs) in vitro and in passive immunity nude mouse model in vivo . Regardless of the presence or absence of NAbs, we demonstrated that eAAVs are more efficient in transduction of cells in the same titer ranges as standard AAVs. To test the therapeutic efficacy, eAAV9-SERCA2a or AAV9-SERCA2a were injected intramyocardially in post-myocardial infarction (MI) mice preinjected with NAbs. Remarkably, eAAV9-SERCA2a outperformed standard AAVs 6 weeks post-MI, significantly improving cardiac function in the presence of NAbs (%EF 55.14 ± 3.50 vs. 27.31 ± 1.63, respectively). Additionally, we demonstrated in vivo that eAAV9-mediated gene delivery is more specific to CMs than to other cell types present in the heart, which suggests that eAAVs preserve cardiotropic properties of AAV9 serotype. With examination of colocalization of eAAVs and markers specific for endosomes (Rab5 and Rab7) in hCMs in vitro , our preliminary data indicated that eAAV infectious entry potentially involves trafficking via endocytic compartments. In conclusion, these results underline the therapeutic potential of eAAVs to evade NAbs, and to facilitate the clinical translation of AAV-based gene therapies to a larger human population.

Bifunctionally engineered polyethylenimines as efficient DNA carriers and antibacterials against resistant pathogens

In this study, we have designed and developed two series of bifunctional conjugates by tethering polyethylenimine with streptomycin. By varying the amount of streptomycin, conjugates, polyethylenimine-streptomycin, have been synthesized and characterized spectroscopically. Gel electrophoresis assay revealed a slight decrease in the cationic charge density on the conjugates as these retarded the mobility of pDNA at higher w/w ratios. Further, transfection studies showed that both the series of conjugates transfected the mammalian cells efficiently with low-molecular weight polyethylenimine-streptomycin conjugates were more competent (∼9-fold enhancement with respect to native bPEI) exhibiting high cell viability too. Besides, both the series of conjugates displayed excellent antibacterial activity on pathogenic bacteria, even better than native streptomycin on resistant strains. Altogether, these results ensure the promising potential of the projected bifunctional conjugates as safe and efficient gene delivery vectors as well as antibacterials for future biomedical applications.

Abstract 584: FTO-Dependent m6A Regulates Cardiomyocyte and Cardiac Function During Remodeling and Repair

Background: Despite its functional importance in various fundamental bioprocesses, the studies of N6-methyladenosine (m6A) in the heart are lacking. In this study, we investigated the role of fat mass and obesity-associated (FTO), an m6A demethylase, in cardiac contractile function during homeostasis and remodeling.

Methods: We used clinical human samples, preclinical pig and mouse models and primary cardiomyocyte cell cultures to study the functional role of m6A and FTO in the heart and in cardiomyocytes. We modulated expression of FTO using AAV9 (in vivo), adenovirus (both in vivo and in vitro) and siRNAs (in vitro). We performed methylated (m6A) RNA immunoprecipitation sequencing (MeRIP-seq) to map transcriptome-wide m6A, and MeRIP qPCR assays to map and validate m6A in individual transcripts, in healthy and failing hearts and myocytes. We performed proteomics analysis using stable isotope labeling with amino acids in cell culture to study m6A role in mRNA to protein translation.

Results: We discovered that FTO has decreased expression in failing mammalian hearts and hypoxic cardiomyocytes, thereby increasing m6A in RNA and decreasing cardiomyocyte contractile function. Improving expression of FTO in failing mouse hearts attenuated the ischemia-induced increase in m6A and decrease in cardiac contractile function. This is carried out by the demethylation activity of FTO, which selectively demethylates cardiac contractile transcripts, thus preventing their degradation and improving their protein expression under ischemia.

Conclusion: Collectively, our study demonstrates the functional importance of FTO-dependent cardiac m6A methylome in cardiac contraction during heart failure and provides a novel mechanistic insight into the therapeutic mechanisms of FTO.

Abstract 104: AAV-Exosomes: A Novel Platform for Myocardial Gene Delivery for Cardioprotection

Introduction: Adeno-associated viruses (AAVs) are viral vectors of choice for delivering genes for long-term expression due to their safety in clinics. However, pre-existing immunity to AAVs from naturally present neutralizing antibodies (NAbs, present in between 60% and 90% of population) poses a significant challenge for AAV-mediated gene delivery. NAbs prevent AAVs from infecting target cells, greatly reducing transduction efficiency and, therefore, the clinical efficacy. Thus, it is essential to develop novel AAV-based vectors that circumvent the effect of NAbs.

Objectives: We aimed to investigate the ability of exosome-encapsulated AAVs (AAVExo) to evade NAbs and serve as a highly efficient gene transfer tool for cardiovascular therapeutics.

Methods and Results: We developed a multi-step purification strategy using iodixanol density gradient to isolate AAVExo with minimal contamination from free AAVs (AAV1, 6 or 9). Biochemical assays, flow cytometry, IVIS Spectrum in vivo optical imaging and echocardiography were used to detect AAV-mediated gene delivery and evaluate cardiac function. AAV6Exo-mCherry and AAV9Exo-FLuc were resistant to NAbs and significantly improved expression of mCherry and firefly luciferase (FLuc) both in mouse and human (iPSC-derived) cardiomyocytes in vitro , and in murine hearts in vivo (in nude mice preinjected with NAbs), compared to free AAVs. To test the therapeutic efficacy of AAVExo-mediated gene delivery in the presence of NAbs, we injected AAV9-SERCA2a or AAV9Exo-SERCA2a into post-MI hearts of nude mice preinjected with IVIg (human intravenous immunoglobulin) preparation. Hearts treated with AAV9Exo-SERCA2a had significantly improved cardiac function compared to those treated with free AAV9-SERCA2a (%EF 62.6 ± 9.8 vs. 28.4 ± 5.3, respectively; 2 weeks after surgery).

Conclusion: Delivery of AAVs protected by carrier exosomes is a promising approach to circumvent the issue of NAbs in AAV-based gene therapy, which can be used in the entire population of patients and may result in higher gene delivery efficacy.

Abstract 301: An m6A Demethylase, FTO Mediates Post-transcriptional mRNA Modifications to Regulate Cardiac and Cardiomyocyte Function

Background: Post-transcriptional modifications in the form of m6A (N6-methyladenosine) regulate mRNA fate and translation, miRNA biogenesis, lncRNA function and several cellular processes. However, m6A mechanisms in the mature post-mitotic tissues such as the mammalian heart remain unexplored. Here, we investigated the role of transcriptome-wide m6A in cardiac protein expression as well as lncRNA function.

Methods: Using biochemical assays, we investigated the spatiotemporal gene expression patterns of m6A regulators in non-failing, failing (ischemic) human hearts, in mouse and pig MI models. In mouse heart, we mapped transcriptome-wide m6A by developing state-of-the-art MeRIP-seq coupled with novel bioinformatics analysis. To investigate the functional relevance of m6A to cardiac proteome, we used SILAC-LC-MS. By silencing (siRNA) m6A-reader proteins, we investigated the role of m6A in cardiomyocyte mRNA stability, decay and nuclear export. For in vivo myocardial gene delivery, we used AAV9 and adenovirus vectors. Finally, we performed immunohistology in cardiomyocytes and mouse heart tissues to study nuclei size, fibrosis and angiogenesis.

Results: We discovered that the expression of m6A demethylase, FTO is decreased in ischemic myocardium and cardiomyocytes, thus in vivo FTO gene delivery resulted in attenuation of ischemia-induced increase in m6A and decrease in cardiac contractile function post-MI. FTO overexpression in mouse heart and human cardiomyocytes revealed selective demethylation (MeRIP-seq) of cardiac contractile transcripts resulting in induced contractile protein expression (SILAC-LC-MS) thus rescuing heart function post-MI. Mechanistically, we demonstrate that the cardioprotective mechanism of FTO is mediated by selective demethylation of cardiac contractile transcripts under ischemia, which prevents mRNA degradation as well as enhanced nuclear compaction. Finally, we demonstrate that FTO overexpression in mouse models of MI resulted in decreased fibrosis and enhanced angiogenesis.

Conclusion: Our study provides the first description of a cardiac active m6A demethylase working at post-transcriptional level as a critical regulator of cardiac contractile function, fibrosis and angiogenesis.

Sun-Smart Practices Amongst School Students (Grades 5, 7, and 9) in Alberta, Canada

Objectives:

The aim of this study was to assess the current knowledge children possess on melanoma and sun-protective behaviour.

Methods:

A one-page survey was administered to students in grades 5, 7, and 9.

Results:

Three hundred ninety-two students from 11 schools in Edmonton were surveyed. Seventy-one percent of students knew that sun exposure can cause skin cancers. Sixty-nine percent were taught by their parents about sun protection, but only 44% of students received similar instructions from teachers. Twenty percent of students indicated that they never or rarely wore sunscreen. Twenty-five percent of students had experienced painful sunburns, and only 46% were willing to use sunscreen if it were available at school. More Caucasian students reported painful or peeling sunburns in each grade level than their non-Caucasian peers (for grade 5, P = .003; for grade 7, P < .0001; for grade 9, P = .001). For all grade levels, the percentage of Caucasian students who indicated that they would not wear sunscreen when going out in the sun was greater than among their non-Caucasian peers (for grade 5, P < .001; for grade 7, P = .003; for grade 9, P = .015).

Conclusions:

A comprehensive and focused approach to sun-smart education is recommended for students.

Recovery of bioactive protein from bacterial inclusion bodies using trifluoroethanol as solubilization agent

Background

Formation of inclusion bodies poses a major hurdle in recovery of bioactive recombinant protein from Escherichia coli. Urea and guanidine hydrochloride have routinely been used to solubilize inclusion body proteins, but many times result in poor recovery of bioactive protein. High pH buffers, detergents and organic solvents like n-propanol have been successfully used as mild solubilization agents for high throughput recovery of bioactive protein from bacterial inclusion bodies. These mild solubilization agents preserve native-like secondary structures of proteins in inclusion body aggregates and result in improved recovery of bioactive protein as compared to conventional solubilization agents. Here we demonstrate solubilization of human growth hormone inclusion body aggregates using 30 % trifluoroethanol in presence of 3 M urea and its refolding into bioactive form.

Results

Human growth hormone was expressed in E. coli M15 (pREP) cells in the form of inclusion bodies. Different concentrations of trifluoroethanol with or without addition of low concentration (3 M) of urea were used for solubilization of inclusion body aggregates. Thirty percent trifluoroethanol in combination with 3 M urea was found to be suitable for efficient solubilization of human growth hormone inclusion bodies. Solubilized protein was refolded by dilution and purified by anion exchange and size exclusion chromatography. Purified protein was analyzed for secondary and tertiary structure using different spectroscopic tools and was found to be bioactive by cell proliferation assay. To understand the mechanism of action of trifluoroethanol, secondary and tertiary structure of human growth hormone in trifluoroethanol was compared to that in presence of other denaturants like urea and guanidine hydrochloride. Trifluoroethanol was found to be stabilizing the secondary structure and destabilizing the tertiary structure of protein. Finally, it was observed that trifluoroethanol can be used to solubilize inclusion bodies of a number of proteins.

Conclusions

Trifluoroethanol was found to be a suitable mild solubilization agent for bacterial inclusion bodies. Fully functional, bioactive human growth hormone was recovered in high yield from inclusion bodies using trifluoroethanol based solubilization buffer. It was also observed that trifluoroethanol has potential to solubilize inclusion bodies of different proteins.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-016-0504-9) contains supplementary material, which is available to authorized users.

Comparative attitude and plans of the medical students and young Nepalese doctors

INTRODUCTION

Many doctors are leaving Nepal to work abroad. To understand this problem better, we decided to study the attitude and plans of young doctors and medical students.

MATERIALS AND METHODS

This cross-sectional study was conducted at Kathmandu Medical College involving 65 first year medical students, 100 interns and 100 house officers. The data collected was entered in Microsoft excel and analysed by SPSS (Statistical Package for Social Sciences) programme. Chi-square test was used to compare two proportions. Significance level was set at 5%.

RESULTS

Only 2% house officers said that their job prospects were excellent as compared to 22.4% of students, whereas 20% house officers as compared to 9% students thought job prospects in Nepal were poor (p= 0.003). Eighty two percent of students thought that a doctor's service to his country was very important as compared to 51% of interns (p= 0.001) and 58% of house officers. Forty percent of students, 58% of interns and 48% of house officers (no statistical significance between the three groups) planned to migrate to a developed country after graduation. Eighty eight percent of students, 89% interns and 74% of house officers (no statistical significant differences between the three groups) were of the opinion that improving career opportunities or working environment of the doctor could make the profession more attractive.

CONCLUSION

Although majority of students, interns and house officers were of the opinion that a doctor's service to his community/country was very important, almost half of them still planned to migrate to a developed country after graduation. Improving the chances of professional advancement and professional working environment can make the profession more attractive, and therefore, may decrease this tendency for brain drain from our country.

Variation in salinity tolerance and shoot sodium accumulation in Arabidopsis ecotypes linked to differences in the natural expression levels of transporters involved in sodium transport

Salinity tolerance can be attributed to three different mechanisms: Na+ exclusion from the shoot, Na+ tissue tolerance and osmotic tolerance. Although several key ion channels and transporters involved in these processes are known, the variation in expression profiles and the effects of these proteins on Na+ transport in different accessions of the same species are unknown. Here, expression profiles of the genes AtHKT1;1, AtSOS1, AtNHX1 and AtAVP1 are determined in four ecotypes of Arabidopsis thaliana. Not only are these genes differentially regulated between ecotypes, the expression levels of the genes can be linked to the concentration of Na+ in the plant. An inverse relationship was found between AtSOS1 expression in the root and total plant Na+ accumulation, supporting a role for AtSOS1 in Na+ efflux from the plant. Similarly, ecotypes with high expression levels of AtHKT1;1 in the root had lower shoot Na+ concentrations, due to the hypothesized role of AtHKT1;1 in retrieval of Na+ from the transpiration stream. The inverse relationship between shoot Na+ concentration and salinity tolerance typical of most cereal crop plants was not demonstrated, but a positive relationship was found between salt tolerance and levels of AtAVP1 expression, which may be related to tissue tolerance.

Changes in matrix phosphorylation during bovine dentin development

Phosphorylation of the organic matrix proteins of dentin is important for the initiation of mineralization, but its relevance in later mineralization stages is controversial. The objective of this study was to analyze changes in the total matrix phosphate content during dentin development and to identify their origin. Amino acid and total matrix phosphate analyses of microdissected developing mantle and circumpulpal fetal bovine dentin specimens were performed. The amino acid composition showed few changes during mantle and circumpulpal dentin maturation. However, the total matrix phosphate content showed a significant, positive correlation with tissue maturation in both mantle and circumpulpal dentin, with a two- and a three-fold increase, respectively, being observed. The data indicate that changes occur in the pattern of phosphorylation of matrix proteins during dentin maturation, which we suggest may play a functional role in later stages of tooth mineralization.

Inability of laser and rotary instrumentation to eliminate root canal infection

BACKGROUND

The authors evaluated the antibacterial effectiveness of laser instrumentation and rotary instrumentation of anterior, single-rooted teeth infected with Enterococcus faecalis.

METHODS

The authors divided 35 infected samples into five groups: Group A: inoculation, laser, 17 percent ethylene-diamine-tetra-acetate (EDTA), 2.5 percent sodium hypochlorite (NaOCl) (n=10); Group B: inoculation, laser, 17 percent EDTA, sterile saline (n = 10); Group C: inoculation, rotary, 17 percent EDTA, 2.5 percent NaOCl (n=10); Group D: inoculation, no instrumentation (positive control) (n=5); Group E: no inoculation, no instrumentation (negative control) (n=5). They sampled and incubated dentin shavings from each canal for bacterial growth.

RESULTS

In Group A, eight tubes were positive for bacterial growth. In Group B, 10 tubes were positive for bacterial growth. In Group C, six tube were positive for bacterial growth. In Group D, all of the tubes were positive for bacterial growth. In Group E, no tubes showed bacterial growth. The Fisher exact test showed no significant differences among groups A, E and C.

CONCLUSION

Neither the laser nor the rotary instrumentation was able to eliminate endodontic infection.

CLINICAL IMPLICATIONS

Although lasers have been presented as high-tech tools for disinfecting root canals, the laser was ineffective in this study.

Neuro-endoscopic surgery--experience and outcome analysis of 102 consecutive procedures in a busy neurosurgical centre of India

BACKGROUND

Neuro-endoscopic surgery is finding increasing application for various clinical conditions. We present our experience of 100 cases of diverse intracranial lesions, including infections, managed by neuro-endoscopy in a busy neurosurgical department in the developing world.

MATERIAL AND METHODS

One hundred patients treated from March 1996 to February 2002 formed the study group. Management of hydrocephalous by Endoscopic third ventriculostomy (ETV) was the aim in 75 patients with or without diagnostic biopsy. Excision or resection was attempted in 25 patients with juxtaventricular or intraventricular lesions. Endoscopic procedures included total tumour resection, partial resection, biopsy, stent placement, Monroplasty, septostomy and third ventriculostomy. Outcomes of endoscopic surgery were evaluated with respect to clinical and/or radiological improvement, complications and need for additional therapy.

FINDINGS

Endoscopy was the only surgical treatment in 59 patients. Intermittent lumbar drainage for cerebrospinal fluid leak, shunt, microsurgery and/or repeat endoscopic surgery were additional treatments needed in 39 patients, who subsequently had increased hospital stay, postoperative morbidity and a higher cost of treatment. Peroperative bleeding due to distorted anatomy and obscured vision in 2 patients with post-infective loculated hydrocephalus (LH) resulted in two fatalities (2%) in the early post-operative period.

INTERPRETATION

Neuro-endoscopic surgery cuts down operative time and hospital stay, reduces cost and results in a faster turnover of the patients. It is a versatile and useful tool for a busy neurosurgical department.

Differentiation of tuberculous from pyogenic brain abscesses with in vivo proton MR spectroscopy and magnetization transfer MR imaging

BACKGROUND AND PURPOSE

MR imaging features are nonspecific with respect to the causative organism for patients with brain abscesses. On the basis of the hypothesis that the biochemical environment depends on the infecting organism and might be different in tuberculous compared with pyogenic brain abscesses, this study attempted to determine whether pyogenic brain abscesses can be differentiated from tuberculous brain abscesses by use of magnetization transfer (MT) MR imaging and in vivo proton MR spectroscopy.

METHODS

Twenty-seven patients with a total of 33 pyogenic brain abscesses and three patients with a total of 12 tuberculous abscesses were evaluated with in vivo MR spectroscopy and MT MR imaging. The diagnosis in all cases was based on the culture of the causative organisms and histopathology whenever done as a part of clinical management.

RESULTS

All 27 patients with pyogenic brain abscesses had lipid and lactate levels of 1.3 ppm and amino acid levels of 0.9 ppm with or without the presence of succinate, acetate, alanine, and glycine, while the three patients with tuberculous abscesses showed only such lipid and lactate levels. The MT ratio from the wall of the pyogenic abscesses was significantly higher (P <.001) than that from the tuberculous abscess wall.

CONCLUSION

It might be possible to differentiate tuberculous abscesses from pyogenic abscesses by using MT MR imaging and in vivo MR spectroscopy, which could be of value in influencing the management of such cases.

Congenital supraglottic cyst: a rare cause of stridor

Congenital laryngeal cysts are very rare and if mismanaged, lead to a high incidence of morbidity and mortality. The case may present as severe stridor and emergent management can obviate a tracheostomy, achieving cure in the process. We report here a case of supraglottic cyst, which was completely occluding the airway and was managed in the emergency setting.

Epidemiology of meningococcal carrier state amongst recruits of a military training centre

An epidemiological study was carried out to determine meningococcal carrier state amongst recruits of a military training centre. 360 recruits with divergent socioeconomic, ethnic backgrounds were studied. Epidemiological factors such as age, religion, educational status, housing conditions, family structure were considered. The overall carrier rate was 11.94%. Carrier rate was higher amongst recruits from poor background and joint families. No association was found between carrier state and smoking as well as those suffering from upper respiratory tract infection. Carrier rate was aslo studied in relation to age, marital status, educational back ground and region.