Antiarrhythmic medication for atrial fibrillation (AIM-AF) study: a physician survey of antiarrhythmic drug (AAD) treatment practices and guideline adherence in Europe

Background

The 2020 European Society of Cardiology (ESC) guidelines provide detailed recommendations for the management of patients with atrial fibrillation (AF). In symptomatic patients, AADs are advised for rhythm control.

Purpose

This study was designed to investigate AAD treatment practices and adherence to guidelines in four European countries.

Methods

An online survey (n=321) of cardiologists or cardiac electrophysiologists (CDs) and interventional electrophysiologists (EPs) was conducted in Germany (DE; n=83), Italy (IT; n=95), Sweden (SE; n=60) and the UK (n=83). Respondents were actively treating ≥10 patients with AF.

Results

(1) The majority of physicians considered guidelines to be the most important non-patient factor influencing their AF management practices (pooled: 65%; range: 55–72%), with 96%

(range: 89–100%) following ESC guidelines. Although amiodarone use was most frequent in heart failure with reduced left ventricular (LV) ejection fraction (pooled: 91%; range: 88–93%) where it is a recommended first-line option, non-adherent AAD selection was common. Amiodarone was frequently selected as a typical treatment choice for minimal/no structural heart disease (SHD) where it is not recommended for initial therapy; this was particularly common in the UK versus SE (Figure 1). Other deviations included use of class 1C drugs in those with coronary artery disease (CAD) (with the exception of SE; Figure 1) and other SHD, as well as use of sotalol in LV hypertrophy (pooled: 30%) and renal impairment (Figure 1). Furthermore, absence of inpatient initiation of sotalol was generally high, with the exception of SE (Figure 1).

(2) Sotalol and dronedarone use in CAD varied between country (pooled: 28% [range: 16–41%] and pooled: 19% [range: 10–54%], respectively).

(3) CDs and EPs used rhythm control as initial therapy in most patients with paroxysmal AF (PAF); however, other than SE, this was not the case for persistent AF (Figure 2).

(4) AADs were preferred over ablation as initial therapy for individuals with infrequent, mildly symptomatic PAF (pooled: 61%), with the exception of SE (48%). Ablation was favoured for most patients with frequent, symptomatic PAF; however, in SE, AADs were preferred for infrequent, highly symptomatic PAF (53%) and frequent, symptomatic PAF (53%).

(5) Rhythm control therapies were selected for asymptomatic or subclinical AF; AADs were used more often (average: 41% [range: 22–60%]; ablation was used less frequently (average: 11% [range: 2–18%]).

Conclusion

Despite assertion that guidelines are the primary determinant for rhythm control treatment decisions, non-adherence was notable in European practice. While deviation may be reasonable in select individual patients, in general, non-adherence could compromise patient safety. As such, establishing the drivers of non-adherent practices is key, and education directed at clinicians to improve optimal and safe use of AADs is warranted in Europe.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Sanofi

Single cell multiomic analysis of T cell exhaustion in vitro

T-cell activation is a key step in the amplification of an immune response. Over the course of an immune response, cells may be chronically stimulated, with some proportion becoming exhausted; an enormous number of molecules are involved in this process. There remain a number of questions about the process, namely: 1) what degree of heterogeneity and plasticity do T-cells exhibit during stimulation? 2) how many unique cell states define chronic stimulation? and 3) what markers discriminate activated from exhausted cells? We addressed these questions by performing single-cell multiomic analysis to simultaneously measure expression of 38 proteins and 399 genes in human T cells expanded in vitro. This approach allowed us to study - with unprecedented depth - how T cells change over the course of chronic stimulation. Comprehensive immunophenotypic and transcriptomic analysis at day 0 enabled a refined characterization of T-cell maturational states and the identification of a donor-specific subset of terminally differentiated T-cells that would have been otherwise overlooked using canonical cell classification schema. As expected, activation downregulated naïve-cell markers and upregulated effector molecules, proliferation regulators, co-inhibitory and co-stimulatory receptors. Our deep kinetic analysis further revealed clusters of proteins and genes identifying unique states of activation, defined by markers temporarily expressed upon 3 days of stimulation (PD-1, CD69, LTA), markers constitutively expressed throughout chronic activation (CD25, GITR, LGALS1), and markers uniquely up-regulated upon 14 days of stimulation (CD39, ENTPD1, TNFDF10); expression of these markers could be associated with the emergence of short-lived cell types. Notably, different ratios of cells expressing activation or exhaustion markers were measured at each time point. These data reveal the high heterogeneity and plasticity of chronically stimulated T cells. Our study demonstrates the power of a single-cell multiomic approach to comprehensively characterize T-cells and to precisely monitor changes in differentiation, activation, and exhaustion signatures during cell stimulation.

Abstract 715: Flow cytometry analysis of immune response to COVID-19 vaccine candidates using an in vitro stimulation model

T cell immunity is vital for the control of viral infections. Cytotoxic CD8 T cells play a crucial role in eliminating virus-infected cells while CD4 helper T cells mediate host immune responses and promote B cells to secrete antibodies. For both, T cell recognition of viral antigens in the form of short peptides presented by HLA complexes is a prerequisite for T cell activation. Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), has become a global pandemic that has disrupted economies and resulted in an enormous burden on health care systems. Despite the worldwide intensive efforts on development of COVID-19 therapeutics, a safe and effective COVID-19 treatment or vaccine is not yet available. In this study, we established an in vitro stimulation system in which peripheral blood mononuclear cells were treated with putative SARS-CoV-2 immunogenic peptides. T cell immune responses were measured using different quantitative flow cytometry panels that were designed for evaluating cytokine production or identifying T cell subsets. Evaluation of host immune responses with a suite of flow cytometric panels may prove to be useful in the study of COVID-19.

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Citation Format: Xiaoshan Shi, Scott J. Bornheimer, Suraj Saksena, Stephanie Widmann, Aaron Tyznik. Flow cytometry analysis of immune response to COVID-19 vaccine candidates using an in vitro stimulation model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 715.

Factors predicting adverse cardiovascular outcomes in patients with atrial fibrillation and heart failure with preserved ejection fraction

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): Electrophysiology Research Foundation

Introduction

Atrial fibrillation (AF) is known to impact cardiovascular(CV) mortality in heart failure (HF) patients (pts) with preserved ejection fraction (pEF) but its exact causes are unknown.

Methods

 We analyzed demographic, clinical, ECG and AF presentation as predictors of CV mortality, sudden death( SCD) and pump failure death(PFD) in HFpEF pts in the TOPCAT AMERICAS trial. We analyzed two AF presentations 1. Pts in sinus rhythm (SR, n = 1319) compared to AF  on ECG (n = 446) at entry or 2. Pts with no AF event by history or ECG ( n = 1007 ) to those with any AF event (n = 760 ).

Results (Table): 5 year (yr) CV mortality was higher in pts with AF on ECG (30%) than SR (18%, p = 0.014) but 5 yr SCD was (10% in AF on ECG & 7% in any AF) & comparable to SR (7% & 9% respectively, p = ns). 5 yr PFD was higher in AF on ECG  (13%) than SR (5%, p = 0.007) 

Conclusions

: 1. CV death risk in HFpEF pts increased with AF on ECG.. 2. SCD was not more frequent with both AF presentations 3. PFD in HFpEF increased with age, ECG recorded AF & elevated heart rate. 4. The recording of AF on ECG was more strongly associated with CV death & PFD, possibly due to greater AF burden . Predictors of adverse outcomes in HFpEF AF on ECG* Any AF* Endpoint Covariate HR (95% CI) p-value HR (95% CI) p-value Time to cardiovascular death Atrial Fibrillation* 1.44 (1.08, 1.92) 0.014 1.15 (0.87, 1.51) 0.338 Age (years) 1.03 (1.02, 1.05) <.001 1.03 (1.02, 1.05) <.001 Black/AA (vs. White) 0.97 (0.65, 1.46) 0.002 0.96 (0.64, 1.44) 0.004 Other race (vs. White) 2.41 (1.46, 3.99) 2.32 (1.41, 3.83) Smoking 2.62 (1.63, 4.20) <.001 2.60 (1.62, 4.17) <.001 Diabetes 1.47 (1.12, 1.94) 0.006 1.45 (1.10, 1.91) 0.009 Systolic BP (mmHg) 0.99 (0.98, 1.00) 0.022 0.99 (0.98, 1.00) 0.014 Heart rate (bpm) 1.02 (1.00, 1.03) 0.012 1.02 (1.01, 1.03) 0.006 Time to Any sudden cardiac death Atrial Fibrillation* 1.17 (0.69, 1.96) 0.563 0.85 (0.53, 1.35) 0.484 Female (vs. Male) 0.46 (0.28, 0.75) 0.002 0.46 (0.28, 0.74) 0.002 Black/AA (vs. White) 1.57 (0.87, 2.82) 0.194 1.49 (0.83, 2.69) <.001 Other race (vs. White) 1.76 (0.70, 4.41) 1.70 (0.68, 4.25) Diabetes 1.70 (1.07, 2.70) 0.024 1.65 (1.04, 2.62) 0.033 Time to pump failure death Atrial Fibrillation* 2.04 (1.22, 3.42) 0.007 1.62 (0.96, 2.75) 0.074 Age (years) 1.06 (1.03, 1.10) <.001 1.06 (1.03, 1.10) <.001 Heart rate (bpm) 1.03 (1.00, 1.05) 0.034 1.03 (1.01, 1.05) 0.015 Cox model of covariates associated with outcomes adjusted for baseline imbalances

Antiarrhythmic Medication for Atrial Fibrillation (AIM-AF) study: A physician survey of antiarrhythmic drug (AAD) treatment practices and guideline adherence in the EU and USA

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Sanofi

Introduction

The 2020 European Society of Cardiology and the 2019 USA (AHA/ACC/HRS) guidelines recommend the use of AADs for rhythm control in patients with symptomatic AF. This study sought to understand AAD treatment practices and adherence to guidelines across the EU and the USA.

Method

An online physician survey of cardiologists, cardiac electrophysiologists and interventional electrophysiologists (N = 569) was conducted in the USA, Germany, Italy and the UK. All respondents were actively treating ≥10 AF patients who received drug therapy and/or who had received or were referred for ablation. This extensively detailed survey explored questions on physician demographics, AF types, and drug treatment and ablation practices.

Results: Of the responses obtained

(1) Amiodarone was used frequently across co-morbidity categories (highest use in those with heart failure with reduced left ventricular ejection fraction [LVEF] [80%]), including in those in which it is not indicated for initial therapy (minimal or no structural heart disease: 26%). Other deviations from guideline recommendations, include: class 1C drugs were used with structural heart disease, including coronary artery disease (CAD) (average class 1C use in CAD-related comorbidities: 6%); sotalol was used with renal dysfunction (22%); and drugs such as sotalol and dofetilide were initiated out of hospital (56% and 17% of respondents, respectively). (2) Nonetheless, a majority of respondents (53%) considered guidelines as the most important non-patient factor in influencing their choice of AF management. (3) Rhythm control was selected more frequently as primary therapy for paroxysmal AF (PAF) (59% of patients) while rate control was used more often for persistent AF (53%). (4) For PAF, AADs were preferred as 1st line more often than ablation, especially if PAF was infrequent and mildly symptomatic (59% of respondents) while ablation was preferred more if frequent symptomatic PAF and for recurrent persistent AF. (5) Rhythm control (AAD or ablation) was chosen in notable numbers for asymptomatic AF and subclinical AF (AADs: 36% and 37%, respectively; ablation: 9% and 14%, respectively). (6) AAD use for those with a first or recurrent episodes of symptomatic AF was 60% or 47%, respectively. (7) Efficacy and safety were chosen as the most important considerations for choice of specific rhythm control therapy (49% and 33%, respectively), and reduction of mortality and cardiovascular hospitalisation (23%) were as important as maintaining sinus rhythm (26%) for rhythm therapy goals.

Conclusions

Although surveyed clinicians consider guidelines important, deviations in patient types and treatments chosen that compromise safety or were not indicated were common. Findings suggest a lack of understanding of the pharmacology and safe use of AADs, highlighting an important need for further education. Abstract Figure.

Flow cytometry analysis of immune response to COVID-19 vaccine candidates using an in vitro stimulation model

T cell immunity is vital for the control of viral infections. Cytotoxic CD8 T cells play a crucial role in eliminating virus-infected cells while CD4 helper T cells mediate host immune responses and promote B cells to secrete antibodies. For both, T cell recognition of viral antigens in the form of short peptides presented by HLA complexes is a prerequisite for T cell activation. Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), has become a global pandemic that has disrupted economies and resulted in an enormous burden on health care systems. Despite the worldwide intensive efforts on development of COVID-19 therapeutics, a safe and effective COVID-19 treatment is not yet available. In this study, we established an in vitro stimulation system in which peripheral blood mononuclear cells were treated with putative SARS-CoV-2 immunogenic peptides. T cell immune responses were measured using different quantitative flow cytometry panels that were designed for evaluating cytokine production or identifying T cell subsets. Evaluation of host immune responses with a suite of flow cytometric panels may prove to be useful in the study of COVID-19.

For Research Use Only. Not for use in diagnostic or therapeutic procedures.

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BD-23276 (v1.0) 1120

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Illuminating the immunopathology of SARS-CoV-2

Over a remarkably short period of time, a great deal of knowledge about severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) infection has been acquired, through the focused and cooperative effort of the international scientific community. Much has become known about how the immune response is coordinated to fight infection, and how it becomes dysregulated in severe disease. In this review, we take an in-depth look at the many immune features associated with the host response to SARS-CoV2, as well as those that appear to mark severe disease.

Abstract 3301: Immune monitoring for immuno-oncology applications

The immunotherapy revolution has spurred the development of many new drugs and drug regimens for patient treatment. A key challenge is to identify the factors that drive patient toxicities and responses to treatment, with a particularly acute need for predictive biomarkers that can discriminate patients destined to respond and fail treatment. Technologies to interrogate immune cells are now readily available, but important gaps remain in their application, which limit full realization of the promise of precision oncology.

One such technology, high parameter flow cytometry, represents a gold-standard for immune monitoring; however, antibody panel design and lack of standardization represent important application gaps that hinder broader use. Here, we present a new tool for panel design, Color Wheel, which builds antibody panels optimized for performance on the user's instrument. We used Color Wheel to develop six panels (cell lineage, immune checkpoint, checkpoint ligand, regulatory T-cell, B-cell, cytokine) that comprehensively interrogate the tumor microenvironment. We demonstrate the value of these panels in identifying differences between disease types, treatment responses, and patient groups in a variety of cancer settings. Furthermore, we have developed the immune checkpoint panel into a dried, ready to use (single test-per-tube) format to lower the barriers to access high parameter flow cytometry technology, and to drive workflow efficiency and assay standardization. We demonstrate excellent concordance between the dried and liquid (wet) versions of the high parameter multicolor panel.

A second technology, molecular cytometry, represents an exciting new approach to high dimensional immune analysis. The technology is capable of measuring at least 102 proteins simultaneously per cell, alongside 400 mRNA targets. An important application gap for this technology is lack of data indicating the sequencing depth needed to resolve cell types in an experiment. Here, we present results from a molecular cytometry experiment sequenced deeply, and then bioinformatically sub-sampled at different levels to identify the minimum level of sequencing needed for clear identification of cells, which can serve as a reference guide for users to save time and cost in their experiments. From the perspective of workflow efficiency, we also present preliminary performance data generated using a dried version of molecular cytometry panel(s).

Finally, our presentation includes an analysis of the rationale for choosing an immune monitoring technology, providing some guidelines that match study type and goals, cost, timelines, complexity, and labor with various single cell technologies.

Citation Format: Woodrow E. Lomas, Guo-Jian Gao, Na Li, Suraj Saksena, Pratip K. Chattopadhyay. Immune monitoring for immuno-oncology applications [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3301.

Abstract 3310: Resolving the heterogeneity of human circulating innate lymphoid cells via simultaneous, high-dimensional analysis of protein and gene expression

Cancer treatment has been revolutionized with the development of immunomodulatory therapies. These therapies have primarily focused on enhancing T-cell responses: whether it is unleashing T cells through blockade of regulatory checkpoint inhibitors or generation of chimeric antigen receptor (CAR) T cells. However, there has been recent interest in harnessing the immunotherapeutic potential of other cytotoxic cells such as Natural Killer (NK) cells. Similar to NK cells, innate lymphoid cells (ILCs) may offer another target of these immunotherapy approaches. Before the potential of these cells can be realized, there is a need for better understanding of these recently described cell populations. ILCs act as the immune system's first responders and have been shown to play a key role in tissue homeostasis, chronic inflammation and cancer. Three main groups of non-cytotoxic ILCs (ILC1, ILC2 and ILC3) have been broadly defined based on developmental trajectories and function, driven by expression of specific transcription factors. Deeper characterization of these cells through either high parameter protein analysis or single-cell RNA sequencing has revealed a more complex and heterogeneous nature of ILCs across different tissues and donors. Therefore, the identity of ILCs is still elusive and controversial.

In this study, we developed a comprehensive approach to further refine the signatures of human circulating ILC subsets. Total ILCs (Lineage- CD127+ cells) were enriched from 4 normal donors by flow sorting using the BD FACSAria™ Fusion cell sorter and processed for downstream single-cell multiomic characterization. BD® AbSeq reagents and a targeted BD Rhapsody™ Immune Response Panel were used to enable simultaneous detection of 42 proteins and 399 genes using the BD Rhapsody™ Single-Cell Analysis System. Differential protein and gene expression analysis in addition to combinatorial expression of CD294 and CD117 confirmed 3 conventional ILC populations as well as the signatures of three distinct subsets within ILC1. This discovery approach provided information about relative expression of a small selection of proteins or surface marker-coding genes that enable the discrimination of these ILC subsets. These data were used to design high-parameter flow cytometry panels for high-throughput analysis of different healthy donors. ILC subsets differentially distributed across donors were detected and defined using unsupervised computational analysis confirming the result of multiomic analysis, while the functional and biological relevance of the identified subsets remains to be assessed.

For Research Use Only. Not for use in diagnostic or therapeutic procedures.

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Citation Format: Aaron J. Tyznik, Mirko Corselli, Gisle V. Baracho, Chip Lomas, Silin Sa, Stephanie Widmann, Suraj Saksena, Smita Ghanekar. Resolving the heterogeneity of human circulating innate lymphoid cells via simultaneous, high-dimensional analysis of protein and gene expression [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3310.

Abstract 2166: Deep characterization of in vitro chronically stimulated T cells via single-cell multiomic analysis

A key step in the clinical production of CAR T cells is the expansion of engineered T cells. To generate enough cells for viable adoptive cell therapy, cells must be robustly stimulated, which raises the risk of inducing T-cell exhaustion and reducing therapeutic efficacy. As protocols for T-cell expansion are being developed to optimize CAR T-cell yield, function and persistence, fundamental questions about the impact of in vitro manipulation on T-cell identity are important to answer. Namely: 1) what types of cells are generated during chronic stimulation? 2) how many unique cell states can be defined during chronic stimulation? We sought to answer these fundamental questions by performing single-cell multiomic analysis using BD® AbSeq and BD Rhapsody™ Single-Cell Analysis system to simultaneously measure expression of 38 proteins and 399 genes in human T cells expanded in vitro. This approach allowed us to study - with unprecedented depth - how T cells change throughout chronic stimulation. Human PBMCs from three healthy donors were stimulated for 14 days in the presence of CD3/CD28 antibody-coated beads and recombinant human IL-2. This model system resembles culture conditions that may be used for CAR T-cell expansion. Cells were collected at different time points (day 0, 3, 7 and 14) prior to downstream analysis. Comprehensive immunophenotypic and transcriptomic analysis at day 0 enabled a refined characterization of T-cell maturational states (from naïve to TEMRA cells) and the identification of a donor-specific subset of terminally differentiated T cells that would have been otherwise overlooked using canonical cell classification schema. As expected, T-cell activation induced downregulation of naïve-associated markers and upregulation of effector molecules, proliferation regulators, co-inhibitory and co-stimulatory receptors. Our deep kinetic analysis further revealed clusters of proteins and genes identifying unique states of activation defined by markers temporarily expressed upon 3 days of stimulation (PD-1, CD69, LTA), markers constitutively expressed throughout chronic activation (CD25, GITR, LGALS1), and markers uniquely up-regulated upon 14 days of stimulation (CD39, ENTPD1, TNFSF10). Notably, different ratios of cells expressing activation or exhaustion markers were measured at each time point. These data indicate heterogeneity and plasticity of chronically stimulated T cells in response to different kinetics of activation. We demonstrate the power of a single-cell multiomic approach to comprehensively characterize T cells and to precisely monitor changes in differentiation, activation and exhaustion signatures in response to different activation protocols. For Research Use Only. Not for use in diagnostic or therapeutic procedures. BD, the BD Logo, and Rhapsody are trademarks of Becton, Dickinson and Company or its affiliates. © 2019 BD. All rights reserved.

Citation Format: Mirko Corselli, Suraj Saksena, Margaret Nakamoto, Woodrow E. Lomas, Ian Taylor, Pratip K. Chattopadhyay. Deep characterization of in vitro chronically stimulated T cells via single-cell multiomic analysis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2166.

Abstract 4271: Standardized approach for monitoring plasma cell disorders

Multi-color flow cytometry using consensus surface markers (CD138, CD38, CD19, CD45, CD27, CD56, CD81, and CD117), intracellular kappa and lambda, as well as other auxiliary markers is routinely being used for the identification and characterization of plasma cells. Here, we describe the development of a modular 10-color plasma cell panel for immunophenotyping of the plasma cell compartment. The panel was developed as an 8-color dried backbone, which can be supplemented with 2 liquid (drop in) reagents.

Lyophilized or dried reagent cocktails in a unit test format are known to drive workflow efficiency in clinical settings by eliminating the need for manual cocktailing (of reagents), and frequent batch to batch verification procedures. Longer shelf life and room temperature storage are additional appealing features for lyophilized and dried products. We have developed a dried-down 8-color plasma cell panel, which is manufactured in a single test-per-tube, ready to use format, and can be supplemented with liquid (drop in) reagents. The flexibility of being able to add 2 liquid reagents to the dried backbone provides the option of using intracellular kappa and lambda to examine clonality or using CD38-multi-epitope and/or anti-p63 (VS38c) reagent(s). The single test-per-tube format is ideally suited for MRD applications, where sample size is limited and there is a need for acquiring a large number of events for data analysis. Also, the dried reagent panel is comprised of multiple high performing polymer dyes, which are brighter than conventional dyes, and afford high resolution of the relevant cell populations. Furthermore, the dried reagent tubes have a long shelf life (12 months) and significantly enhance the workflow efficiency.

Comparison of the liquid and dried versions of the 10-color plasma cell panel using peripheral blood from healthy donors (as well as control cell lines) showed similar staining patterns, comparable population statistics, and fluorochrome brightness. The dried plasma cell tube(s) were also tested on bone marrow samples from healthy and diseased subjects in conjugation with intracellular staining for kappa and lambda. Our results demonstrate that the 10-color plasma cell panel can be used for identification of the plasma cell compartment (based on CD38 & CD138 expression), assessment of aberrant marker expression (CD19, CD27, CD81, CD117, CD45, CD56) for the identification of normal and abnormal plasma cells, and examining clonality in multiple patient samples.

Citation Format: Ulrika Johansson, Na Li, Suraj Saksena, Natalie Golts, Brent Gaylord. Standardized approach for monitoring plasma cell disorders [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4271.

Lymphocyte Subset Counts in COVID-19 Patients: A Meta-Analysis

A reduced peripheral blood absolute lymphocyte count with an elevated neutrophil count has been a consistent observation in hospitalized coronavirus disease 2019 (COVID‐19) patients. In this brief meta‐analysis, the reduction of lymphocyte subset counts in COVID‐19 patients was investigated across 20 peer‐reviewed studies meeting criteria for reporting lymphocyte subset counts and COVID‐19 disease severity. CD4+ T cell, CD8+ T cell, B cell, NK cell, and total lymphocyte cell counts all showed statistically significant reduction in patients with severe/critical COVID‐19 disease compared to mild/moderate disease. T‐cell subsets showed the largest standardized magnitude of change. In some studies, multivariate analysis has shown that CD4 and/or CD8 T‐cells counts are independently predictive of patient outcomes. © 2020 International Society for Advancement of Cytometry

Standardized Approach for Monitoring Plasma Cell Disorders

Multi-color flow cytometry using consensus surface markers (CD138, CD38, CD19, CD45, CD27, CD56, CD81, and CD117), intracellular kappa and lambda, as well as other auxiliary markers is routinely used for the identification and characterization of plasma cells. Here, we describe the development of a modular 10-color plasma cell panel for immunophenotyping of the plasma cell compartment. The panel was developed as an 8-color dried backbone, manufactured in a single test-per-tube, ready to use format. The dried backbone can be supplemented with liquid (drop in) reagents, which provides the flexibility of using intracellular kappa and lambda to examine clonality or using CD38-multi-epitope and/or anti-p63 (VS38c) reagent(s). The single test-per-tube format is ideally suited for MRD applications, where sample size is limited and acquisition of millions of events is needed for data analysis. In addition, the dried reagent tubes have a long shelf life (12 months at 20–25°C vs. 24 hours for liquid cocktails with multiple BV dyes in BSB buffer at 2–8°C). Furthermore, utilization of multiple high-performing polymer dyes in the panel affords high resolution of the relevant cell populations.

The dried plasma cell tube(s) were tested on bone marrow samples from healthy and diseased subjects in conjunction with intracellular staining for kappa and lambda. Our results demonstrate that the 10-color plasma cell panel can be used for identification of the plasma cell compartment (based CD38 and CD138 expression), assessment of aberrant marker expression (CD19, CD27, CD81, CD117, CD45, and CD56) for the identification of normal and abnormal plasma cells, and examining clonality in multiple patient samples (Kappa and Lambda).

Deep characterization of in vitro chronically stimulated T cells via single-cell multiomic analysis

To generate enough cells for viable adoptive cell therapy, cells must be robustly stimulated, which raises the risk of inducing T-cell exhaustion and reducing therapeutic efficacy. To comprehensively characterize in vitro chronically expanded human T cells, we performed single-cell multiomic analysis using BD® AbSeq and BD Rhapsody™ Single-Cell Analysis system for simultaneous measurement of the expression of 38 proteins and 399 genes. Comprehensive immunophenotypic and transcriptomic analysis at day 0 enabled a refined characterization of T-cell maturational states. T-cell activation induced by anti-CD3/CD28 beads and recombinant human IL-2 led to downregulation of naïve-associated markers and upregulation of effector molecules, proliferation regulators, co-inhibitory and co-stimulatory receptors. Our deep kinetic analysis further revealed clusters of proteins and genes identifying unique states of activation defined by markers temporarily expressed upon 3 days of stimulation, markers constitutively expressed throughout chronic activation, and markers uniquely up-regulated upon 14 days of stimulation. These data indicate heterogeneity and plasticity of chronically stimulated T cells in response to different kinetics of activation. We demonstrate the power of a single-cell multiomic approach to comprehensively characterize T cells and to precisely monitor changes in differentiation, activation and exhaustion signatures in response to different activation protocols.

For Research Use Only. Not for use in diagnostic or therapeutic procedures.

BD, the BD Logo, and Rhapsody are trademarks of Becton, Dickinson and Company or its affiliates. © 2019 BD. All rights reserved.

A Performance-Optimized Multicolor Flow Cytometry Dried-Reagent Cocktail for Memory T-Cell Analysis

The reliance on flow cytometry for phenotypical and functional analyses of immune components in both research and clinical laboratories has increased the need flow cytometric assay standardization. Dried-down reagent cocktails pre-optimized with regards to fluorophore choice for each specificity as well as concentration of each conjugate can improve standardization. Use of a pre-optimized dried-down cocktail provides an efficient assay workflow which can minimize operator error in addition to offering enhanced reagent stability and reduced variability across instruments and sites.

We developed a dried-down reagent cocktail for the identification and characterization of CD4+ and CD8+ T-cell memory and naïve subsets, including stem cell memory populations. The BD Horizon™ Dri Memory T cell panel contains optimized antibody-fluorophore conjugates against CD3, CD4, CD8, CD45RA, CD197, CD27 and CD95. Additional markers can be accommodated as drop-ins for a more comprehensive analysis.

This cocktail was optimized for stain index in all channels of a red, blue, violet laser flow cytometer (BD FACSLyric™) in liquid format, then converted to dry format. The performance of the dried-down cocktail, with regards to MFI and % positivity of T-cell subsets, is comparable to that of its optimized liquid equivalents. Additionally, results are consistent across FACSLyric instruments and similarly when acquired on a BD LSRFortessa™.

The comparable performance of the dried-down cocktail tube, along with the advantages offered by using a dried reagent cocktail, and the convenience of adding liquid drop-in reagents, reveal the BD Horizon Dri Memory T cell panel tube to be a valuable option for memory T-cell flow cytometry analysis.

Resolving the heterogeneity of human circulating innate lymphoid cells via simultaneous, high-dimensional analysis of protein and gene expression

Cancer treatment has been revolutionized with the development of immunomodulatory therapies. While these therapies have primarily focused on enhancing T-cell responses, there has been interest in harnessing the potential of other cytotoxic cells such as Natural Killer (NK) cells. Similar to NK cells, innate lymphoid cells (ILCs) may offer another target of these immunotherapy approaches. However, there is a need for better understanding of these recently described cells.

In this study, we developed a comprehensive approach to further refine the signatures of human circulating ILC subsets. Total ILCs were enriched using the BD FACSAria™ Fusion cell sorter and processed for downstream single-cell multiomic characterization. BD® AbSeq reagents and a targeted BD Rhapsody™ Immune Response Panel enabled simultaneous detection of 42 proteins and 399 genes using the BD Rhapsody™ Single-Cell Analysis System. Differential protein and gene expression analysis in addition to combinatorial expression of CD294 and CD117 confirmed 3 conventional ILC populations as well as the signatures of 3 distinct subsets within ILC1. This discovery approach provided information about relative expression of a small selection of proteins or surface marker-coding genes that enable the discrimination of these ILC subsets. These data were used to design high-parameter flow cytometry panels for high-throughput analysis. ILC subsets differentially distributed across donors were detected and defined using unsupervised computational analysis confirming the result of multiomic analysis.

For Research Use Only.

Class 1 laser product.

BD, the BD Logo, and Rhapsody are trademarks of Becton, Dickinson and Company or its affiliates. © 2019 BD. All rights reserved.

Immune monitoring for immuno-oncology applications

The immunotherapy revolution has spurred the development of many new drugs and drug regimens for patient treatment. A key challenge is to identify the factors that drive patient toxicities and responses to treatment, with a particularly acute need for predictive biomarkers that can discriminate patients destined to respond and fail treatment. Technologies to interrogate immune cells are now readily available, but important gaps remain in their application, which limit the full realization of the promise of precision oncology.

High parameter flow cytometry is a gold-standard but is limited by difficulty of panel design and lack of standardization. We present Color Wheel, a panel design tool, which builds optimized antibody panels based on the user’s instrument. These optimized panels have been manufactured in a dried, ready to use format to drive workflow and assay standardization. Initial results demonstrate excellent concordance between the dried and liquid versions of the high parameter multicolor panel(s).

Molecular cytometry represents an exciting new approach to high dimensional immune analysis because it can measure at least 102 proteins and 400 mRNA targets simultaneously per cell. An important application gap for this technology is lack of data indicating the sequencing depth needed for adequate resolution. Here, we present results from a molecular cytometry experiment sequenced deeply, and then bioinformatically sub-sampled at different levels to identify the minimum level of sequencing needed for clear identification of cells, which can serve as a reference guide for users to save time and cost in their experiments. We also present preliminary data generated using dried version of molecular cytometry panel(s).

Abstract B90: Deep characterization of in vitro chronically stimulated T cells through single-cell multiomic analysis

A key step in the clinical production of CAR T cells is the expansion of engineered T cells. To generate enough cells for a therapeutic product, cells must be robustly stimulated, which raises the risk of inducing T-cell exhaustion and reducing therapeutic efficacy. As protocols for T-cell expansion are being developed to optimize CAR T cell yield, function, and persistence, fundamental questions about the impact of in vitro manipulation on T-cell identity are important to answer. Namely: 1) What types of cells are generated during chronic stimulation? 2) How many unique cell states can be defined during chronic stimulation? We sought to answer these fundamental questions by performing single-cell multiomic analysis to simultaneously measure expression of 38 proteins and 399 genes in human T cells expanded in vitro. This approach allowed us to study—with unprecedented depth—how T cells change over the course of chronic stimulation. Human PBMCs from three healthy donors were continuously stimulated for 14 days in the presence of CD3/CD28 antibody-coated beads and recombinant human IL-2. This model system was developed to resemble culture conditions that may be used for CAR T cell expansion. Cells were collected at different time points (day 0, 3, 7, and 14) prior to downstream analysis. Comprehensive immunophenotypic and transcriptomic analysis at day 0 enabled a refined characterization of T-cell maturational states (from naive to TEMRA cells) and the identification of a donor-specific subset of terminally differentiated T-cells that would have been otherwise overlooked using canonical cell classification schema. As expected, T-cell activation induced downregulation of naive-associated markers and upregulation of effector molecules, proliferation regulators, coinhibitory and costimulatory receptors. Our deep kinetic analysis further revealed clusters of proteins and genes identifying unique states of activation defined by markers temporarily expressed upon 3 days of stimulation (PD-1, CD69, LTA), markers constitutively expressed throughout chronic activation (CD25, GITR, LGALS1), and markers uniquely upregulated upon 14 days of stimulation (CD39, ENTPD1, TNFSF10). Notably, different ratios of cells expressing activation or exhaustion markers were measured at each time point. These data indicate high heterogeneity and plasticity of chronically stimulated T cells in response to different kinetics of activation. In this study, we demonstrate the power of a single-cell multiomic approach to comprehensively characterize T cells and to precisely monitor changes in differentiation, activation, and exhaustion signatures in response to different activation protocols.

Citation Format: Mirko Corselli, Margaret Nakamoto, Chip Lomas, Ian Taylor, Suraj Saksena, Tariq Arshad, Pratip K. Chattopadhyay. Deep characterization of in vitro chronically stimulated T cells through single-cell multiomic analysis [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr B90.

NCEPOD and alcohol-related liver disease, what are the views of those who deliver the service? A survey of consultants and trainees in North Eastern England

BACKGROUND

National Confidential Enquiry into Patient Outcome and Death (NCEPOD) 'Measuring the Units' (June 2013) identified significant organisational and attitudinal deficits in hospital care of patients with alcohol-related liver disease (ARLD), care being recognised as good in less than 50% of patients.

METHOD

We surveyed over 700 consultants and trainees in acute medical and intensive therapy specialties to examine their perceptions of the NCEPOD findings.

RESULTS

A total of 178 responded. In keeping with the NCEPOD findings, their perception was of lack of 24-hour access to specialty advice for patients with liver disease and inequity of access to high-dependency units. Their explanations include lack of resources, therapeutic nihilism and prejudicial judgements that would not be made of other patient groups.

CONCLUSION

There is an urgent need for robust mechanisms to ensure equity of access to specialist liver advice and intensive therapy unit resources, and to counter negative and prejudicial attitudes to these patients.

An integrated enrichment system to facilitate isolation and molecular characterization of single cancer cells from whole blood

Circulating tumor cells (CTCs) carry valuable biological information. While enumeration of CTCs in peripheral blood is an FDA-approved prognostic indicator of survival in metastatic prostate and other cancers, analysis of CTC phenotypic and genomic markers is needed to identify cancer origin and elucidate pathways that can guide therapeutic selection for personalized medicine. Given the emergence of single-cell mRNA sequencing technologies, a method is needed to isolate CTCs with high sensitivity and specificity as well as compatibility with downstream genomic analysis. Flow cytometry is a powerful tool to analyze and sort single cells, but pre-enrichment is required prior to flow sorting for efficient isolation of CTCs due to the extreme low frequency of CTCs in blood (one in billions of blood cells). While current enrichment technologies often require many steps and result in poor recovery, we demonstrate a magnetic separator and acoustic microfluidic focusing chip integrated system that enriches rare cells in-line with FACS™ (fluorescent activated cell sorting) and single-cell sequencing. This system analyzes, isolates, and index sorts single cells directly into 96-well plates containing reagents for Molecular Indexing (MI) and transcriptional profiling of single cells. With an optimized workflow using the integrated enrichment-FACS system, we performed a proof-of-concept experiment with spiked prostate cancer cells in peripheral blood and achieved: (i) a rapid one-step process to isolate rare cancer cells from lysed whole blood; (ii) an average of 92% post-enrichment cancer cell recovery (R² = 0.9998) as compared with 55% recovery for a traditional benchtop workflow; and (iii) detection of differentially expressed genes at a single cell level that are consistent with reported cell-type dependent expression signatures for prostate cancer cells. These model system results lay the groundwork for applying our approach to human blood samples from prostate and other cancer patients, and support the enrichment-FACS system as a flexible solution for isolation and characterization of CTCs for cancer diagnosis. © 2018 International Society for Advancement of Cytometry.

Abstract 4118: Molecular cytometry for immunotherapy trials

The ability to simultaneously query both protein and mRNA expression on tens of thousands of single cells has emerged only recently, with the development of CITE-seq, REAP-seq, and Ab-seq platforms. Each technology relies on antibodies conjugated to oligonucleotide tags, followed by capture of antibody-stained cells for single cell RNA-sequencing. The technologies have important advantages over flow cytometry, chiefly in that they allow study of a limitless number of parameters, and single cell RNA sequencing, which cannot identify cell populations with as much verity as protein/antibody-based analysis. We characterized the newest molecular cytometry technique (Ab-seq, BD Biosciences) by titrating nearly 100 antibodies (in a single staining experiment and sequencing run), and demonstrated that oligonucleotide antibodies exhibit the same staining characteristics and patterns as flow cytometry antibodies. We also comprehensively examined cells discordant for protein and mRNA expression, in order to discriminate true features of immune cell biology from artifacts caused by drop-out in sequencing assays. Importantly, we also found that mRNA expression could guide the discrimination of cells expressing a protein versus those lacking expression, and define a remarkably low limit of detection for the technology: 1-5 molecules. This remarkable sensitivity will allow detection of cells expressing even the lowest levels of immune exhaustion and checkpoint molecules in cancer immunotherapy trials, and could enable better biomarker discovery than existing technologies. Moreover, this approach allows more detailed characterization of the tumor microenvironment and periphery than ever before. Indeed, in a lymphoma patient, we show that cells expressing both PD1 and CTLA4 carry a unique and specific signature that includes markers never revealed by flow cytometry or other technologies, which might represent new targets for immunotherapy. In sum, this presentation will characterize this new technology and demonstrate the power and promise of new molecular cytometry tools.

Citation Format: Woodrow E. Lomas, Aidan F. Winters, Jason Alexandre, Jody Martin, Nidhanjali Bansal, Margaret Nakamoto, Brent Gaylord, Suraj Saksena, Pratip K. Chattopadhyay. Molecular cytometry for immunotherapy trials [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4118.

Single cell multiomic analysis of chronically stimulated T cells displaying hallmarks of T-cell exhaustion

T-cell exhaustion is a dysfunctional state caused by persistent antigen stimulation mediated by chronic infections or cancer. Current immunotherapy approaches focus on reinvigorating exhausted T cells through immune-receptor-blocking antibodies. A deeper understanding of the exhausted T-cell state is crucial for identification of new therapeutic targets. Single cell RNA-sequencing (scRNA-seq) is a powerful tool for resolving heterogeneity in complex systems like these; however the lack of protein information for the same cells can make it difficult to identify cells of interest or detect cellular responses. To resolve both mRNA and protein information in the same assay, we utilized DNA-conjugated BD™ AbSeq antibodies to profile protein and mRNA expression, using high-throughput sequencing analysis at the single cell level. Sorted T cells that had been transiently and chronically stimulated were multiplexed using the BD™ Single-Cell Multiplexing Kit and pooled before undergoing cell partitioning and cDNA capture on the BD Rhapsody™ system; this minimized batch effects and saved time and reagents. A panel of 400 mRNA targets alongside the 39-plex antibody panel was used for the study. We showed that cell-type resolution increased with higher protein plex, and the addition of mRNA information alongside protein markers revealed candidate protein markers for specific cell states. This study showcased the power of multiomics in analyzing heterogenous cell populations and cell states and answering complex biological questions.

Research Use Only. Not for use in diagnostic or therapeutic procedures.

BD, the BD Logo, and Rhapsody are trademarks of Becton, Dickinson and Company. © 2019 BD and its subsidiaries. All rights reserved.

Mapping leucocyte populations in mouse lymphoid tissues and blood using a 28-color panel on the BD FACSymphonyTM System

Multiparameter flow cytometric analysis of single cells allows the enumeration and characterization of heterogeneous cell populations in a variety of infections, blood cancers, immunodeficiencies and other disorders. Supported by advances in reagent development and instrumentation, this approach has increased dimensionality in single-cell data collection, and accelerated the discovery and testing of new therapies. Here we show a broad immunophenotyping panel that identifies the major leucocyte populations and various sub-populations from different mouse tissues. The panel can also be divided into focused modules for specific analysis of T cell, B cell or myeloid/natural killer cell lineages. BD FACSymphony combined with BD Horizon Brilliant Dyes allowed for high resolution identification of known leucocyte populations. Dimensionality reduction with t-SNE and automated clustering algorithms simplified cell analysis, enabling a faster and more efficient comparison of cell phenotypes across the tissues. Importantly, automated cell clustering analyses, while recognizing the predicted cell populations, also identified cell subsets missed during supervised analysis of the dataset. Thus, we describe a comprehensive single-cell profiling application capable of identifying well-characterized leucocyte populations and that has the potential to discover unique cell phenotypes.

Evaluation of activation and homing markers on regulatory T cells using a modular flow cytometry approach on the BD FACSLyric™ flow cytometer

Advancements in cell analysis capabilities have significantly expanded our understanding of the complexity of immunological systems. As the need for deeper analysis has increased, many laboratories have employed a set of lineage markers to define a cell population, followed by the addition of unique markers specific to their biological question. Utilizing regulatory T cells (Treg) as a model population, we describe the design of an 8-color backbone panel on a 12-Color BD FACSLyric™ flow cytometer that can be supplemented with 4 drop-in markers (colors) to characterize two critical facets of Treg biology: activation and homing. Intelligent panel design enabled identification of human naïve and activated Treg cells utilizing established Treg markers (CD3, CD4, CD25, CD127, FoxP3, CD45RA). CD15s and CD161 were included in the 8-color backbone panel to identify functionally suppressive effector and/or pro-inflammatory cytokine secreting Tregs. Importantly, addition of a 4-color drop-in activation panel (PI16, CD147, CD39 and HLA-DR) or a 4-color drop-in homing panel (CCR4, CCR6, CXCR3 and CD31) did not impact resolution of the backbone Treg population(s), while providing new and interesting insights into Treg biology. We highlight the utility of a modular panel design approach that provides an efficient, scalable, and standardized solution for complex analysis of essentially any cell population of interest.

Diffusion Tensor Imaging of the Normal Cervical and Thoracic Pediatric Spinal Cord

BACKGROUND AND PURPOSE

DTI data of the normal healthy spinal cord in children are limited compared with adults and are typically focused on the cervical spinal cord. The purpose of this study was the following: to investigate the feasibility of obtaining repeatable DTI parameters along the entire cervical and thoracic spinal cord as a function of age in typically developing pediatric subjects; to analyze the DTI parameters among different transverse levels of the cervical and thoracic spinal cord; and to examine the sex differences in DTI parameters along the cervical and thoracic spinal cord.

MATERIALS AND METHODS

Twenty-two subjects underwent 2 identical scans by using a 3T MR imaging scanner. Axial diffusion tensor images were acquired by using 2 overlapping slabs to cover the cervical and thoracic spinal cord. After postprocessing, DTI parameters were calculated by using ROIs drawn on the whole cord along the entire spinal cord for both scans.

RESULTS

An increase in fractional anisotropy and a decrease in mean diffusivity, axial diffusivity, and radial diffusivity were observed with age along the entire spinal cord. Significantly lower fractional anisotropy and higher mean diffusivity values were observed in the lower cervical cord compared with the upper cervical cord. Axial diffusivity values in the cervical cord were higher compared with the thoracic cord. No statistically significant sex differences were observed for all DTI parameters. There was a moderate-to-strong repeatability for all DTI parameters.

CONCLUSIONS

This study provides an initial understanding of DTI values of the spinal cord relevant to age and sex and shows that obtaining repeatable DTI values of the entire cord in children is feasible.

Permeability estimates in histopathology-proved treatment-induced necrosis using perfusion CT: can these add to other perfusion parameters in differentiating from recurrent/progressive tumors?

BACKGROUND AND PURPOSE

Differentiating treatment effects from RPT is a common yet challenging task in a busy neuro-oncologic practice. PS probably represents a different aspect of angiogenesis and vasculature and can provide additional physiologic information about recurrent/progressive enhancing lesions. The purpose of the study was to use PS measured by using PCT to differentiate TIN from RPT in patients with previously irradiated brain tumor who presented with a recurrent/progressive enhancing lesion.

MATERIALS AND METHODS

Seventy-two patients underwent PCT for assessment of a recurrent/progressive enhancing lesion from January 2006 to November 2009. Thirty-eight patients who underwent surgery and histopathologic diagnosis were included in this analysis. Perfusion parameters such as PS, CBV, CBF, and MTT were obtained from the enhancing lesion as well as from the NAWM.

RESULTS

Of 38 patients, 11 were diagnosed with pure TIN and 27 had RPT. Patients with TIN showed significantly lower mean PS values than those with RPT (1.8 ± 0.8 versus 3.6 ± 1.6 mL/100 g/min; P value=.001). The TIN group also showed lower rCBV (1.2 ± 0.3 versus 2.1 ± 0.7; P value<.001), lower rCBF (1.2 ± 0.5 versus 2.6 ± 1.7; P value=.004), and higher rMTT (1.4 ± 0.4 versus 1.0 ± 0.4; P value=.018) compared with the RPT group.

CONCLUSIONS

PCT and particularly PS can be used in patients with previously treated brain tumors to differentiate TIN from RPT. PS estimates can help increase the accuracy of PCT in differentiating these 2 entities.

Brain MR imaging and 1H-MR spectroscopy changes in patients with extrahepatic portal vein obstruction from early childhood to adulthood

BACKGROUND AND PURPOSE

MR imaging and (1)H-MR spectroscopy changes are well reported in cirrhotic patients, whereas they are inadequately reported in EHPVO. The aim of this study was to investigate age-related changes in brain MR imaging and metabolite profile in EHPVO with and without MHE and to explore any correlation of imaging and (1)H-MR spectroscopy parameters with blood ammonia.

MATERIALS AND METHODS

Sixty-three patients with EHPVO (children, 7-12 years [n = 22], adolescents, 13-18 years [n = 15] and adults, 19-41 years [n = 26]) and 47 healthy age/sex-matched volunteers were studied. Neuropsychological tests, MR imaging, (1)H-MR spectroscopy, and blood ammonia estimation were performed in all subjects.

RESULTS

Of 63 EHPVO patients, 25 (40%) who had MHE showed significantly increased MD, Glx, and blood ammonia in all 3 age groups; however, myo-inositol was significantly lower only in adults when compared with controls. MD positively correlated with blood ammonia and Glx in all age groups. Brain choline levels were normal in all patients with different age groups.

CONCLUSIONS

Increases in brain MD, Glx, and blood ammonia were associated with MHE in all age groups. Normal brain choline in EHPVO signifies healthy liver and may serve as a diagnostic marker for its differentiation from cirrhosis-induced encephalopathy. Significant decrease of myo-inositol in adults is probably due to cellular osmoregulation secondary to long-standing hyperammonemia.

ESCRT-II coordinates the assembly of ESCRT-III filaments for cargo sorting and multivesicular body vesicle formation

The sequential action of five distinct endosomal-sorting complex required for transport (ESCRT) complexes is required for the lysosomal downregulation of cell surface receptors through the multivesicular body (MVB) pathway. On endosomes, the assembly of ESCRT-III is a highly ordered process. We show that the length of ESCRT-III (Snf7) oligomers controls the size of MVB vesicles and addresses how ESCRT-II regulates ESCRT-III assembly. The first step of ESCRT-III assembly is mediated by Vps20, which nucleates Snf7/Vps32 oligomerization, and serves as the link to ESCRT-II. The ESCRT-II subunit Vps25 induces an essential conformational switch that converts inactive monomeric Vps20 into the active nucleator for Snf7 oligomerization. Each ESCRT-II complex contains two Vps25 molecules (arms) that generate a characteristic Y-shaped structure. Mutant 'one-armed' ESCRT-II complexes with a single Vps25 arm are sufficient to nucleate Snf7 oligomerization. However, these oligomers cannot execute ESCRT-III function. Both Vps25 arms provide essential geometry for the assembly of a functional ESCRT-III complex. We propose that ESCRT-II serves as a scaffold that nucleates the assembly of two Snf7 oligomers, which together are required for cargo sequestration and vesicle formation during MVB sorting.

High performance tangential flow filtration

Conventional tangential flow filtration (TFF) has traditionally been limited to separation of solutes that differ by about ten-fold in size. Wide pore-size distributions, membrane fouling, and concentration polarization phenomena have commonly been cited as reasons for this limitation. The use of TFF in the biotechnology industry has therefore been restricted to cell-protein, virus-protein, and protein-buffer separations. A multi-disciplinary team with industrial and academic members was formed to overcome these limitations and enable protein-protein separations using High Performance TFF (HPTFF) systems. Pore-size distributions have been improved with the development of new membrane formulation and casting techniques. Membrane fouling has been controlled by operating in the transmembrane pressure-dependent regime of the filtrate flux curve and by carefully controlling fluid dynamic start-up conditions. Concentration polarization was exploited to enhance, rather than limit, the resolution of solutes. Concentration polarization has also been controlled by operating a co-current filtrate stream that maintains transmembrane pressure constant along the length of the TFF module. High yields and purification factors were obtained even with small differences in protein sieving. IgG-BSA and BSA monomer-oligomer mixtures have successfully been separated with these systems. HPTFF technology provides a competitive purification tool to complement chromatographic processing of proteins.

Protein fractionation using electrostatic interactions in membranel filtration

One of the critical factors limiting the development of membrane systems for protein fractionation has been the poor selectivity that has generally been obtained with these membrane devices. We have demonstrated that it is possible to dramatically improve the selectivity of available membrane systems by exploiting the different electrostatic interactions between the two proteins and the membrane. The separation factor for the albumin-hemoglobin system could be increased to more than 70 simply by reducing the salt concentration and adjusting the pH to around 7 (near the isoelectric point of hemoglobin). This very high selectivity was a direct result of the strong electrostatic exclusion of the charged albumin from the membrane pores under these conditions. This high selectivity makes it possible to very effectively separate these albumin-hemoglobin mixtures using membrane filtration, and this was demonstrated experimentally using both a simple batch filtration process and a continuous diafiltration system. The hemoglobin recovery in the diafiltration experiment was greater than 70% after a 3-diavolume filtration, with the Hb purification factor being around 100 under these conditions. These results clearly demonstrate the potential of membrane systems for the fractionation of proteins even with very similar molecular weights.

Functional reconstitution of ESCRT-III assembly and disassembly

Receptor downregulation in the MVB pathway is mediated by the ESCRT complexes. ESCRT-III is composed of four protein subunits that are monomeric in the cytosol and oligomerize into a protein lattice only upon membrane binding. Recent studies have shown that the ESCRT-III protein Snf7 can form a filament by undergoing homo-oligomerization. To examine the role of membrane binding and of interactions with other ESCRT components in initiating Snf7 oligomerization, we used fluorescence spectroscopy to directly detect and characterize the assembly of the Snf7 oligomer on liposomes using purified ESCRT components. The observed fluorescence changes reveal an obligatory sequence of membrane-protein and protein-protein interactions that generate the active conformation of Snf7. Also, we demonstrate that ESCRT-III assembly drives membrane deformation. Furthermore, using an in vitro disassembly assay, we directly demonstrate that Vps24 and Vps2 function as adaptors in the ATP-dependent membrane disassembly of the ESCRT-III complex by recruiting the AAA ATPase Vps4.

Structure and disassembly of filaments formed by the ESCRT-III subunit Vps24

The ESCRT machinery mediates sorting of ubiquitinated transmembrane proteins to lysosomes via multivesicular bodies (MVBs) and also has roles in cytokinesis and viral budding. The ESCRT-III subunits are metastable monomers that transiently assemble on membranes. However, the nature of these assemblies is unknown. Among the core yeast ESCRT-III subunits, Snf7 and Vps24 spontaneously form ordered polymers in vitro. Single-particle EM reconstruction of helical Vps24 filaments shows both parallel and head-to-head subunit arrangements. Mutations of regions involved in intermolecular assembly in vitro result in cargo-sorting defects in vivo, suggesting that these homopolymers mimic interactions formed by ESCRT-III heteropolymers during MVB biogenesis. The C terminus of Vps24 is at the surface of the filaments and is not required for filament assembly. When this region is replaced by the MIT-interacting motif from the Vps2 subunit of ESCRT-III, the AAA-ATPase Vps4 can both bundle and disassemble the chimeric filaments in a nucleotide-dependent fashion.

Ordered assembly of the ESCRT-III complex on endosomes is required to sequester cargo during MVB formation

The sequential action of the Vps27/HRS complex, ESCRT-I, -II, and -III is required to sort ubiquitinated transmembrane proteins to the lumen of lysosomes via the multivesicular body (MVB) pathway. While Vps27/HRS, ESCRT-I, and -II are recruited to endosomes as preformed complexes, the ESCRT-III subunits Vps20, Snf7, Vps24, and Vps2 only assemble into a complex on endosomes. We have addressed the pathway and the regulation for ESCRT-III assembly. Our findings indicate the ordered assembly of a transient 450 kDa ESCRT-III complex on endosomes. Despite biochemical and structural similarity, each subunit contributes a specific function. Vps20 nucleates transient oligomerization of Snf7, which appears to sequester MVB cargo. Vps24 terminates Snf7 oligomerization by recruiting Vps2, which subsequently engages the AAA-ATPase Vps4 to dissociate ESCRT-III. We propose that the ordered assembly and disassembly of ESCRT-III delineates an MVB sorting domain to sequester cargo and complete the last steps of MVB sorting.

Assessment of therapeutic response in brain tuberculomas using serial dynamic contrast-enhanced MRI

AIM

To assess the most useful dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) index in the evaluation of the therapeutic response in brain tuberculoma (BT) patients.

SUBJECTS AND METHODS

Twenty-three patients with 25 BT lesions were serially evaluated using DCE MRI. All lesions were classified into two groups: group I (n=15) included patients who showed clinical, as well as imaging, improvement; and group II (n=10) included patients with either clinical or radiological deterioration. The group I and group II lesions were examined for up to 12 months at 4 monthly intervals. However, the lesions in five patients of group II were excised following clinical deterioration after 4 months of therapy. The perfusion indices, i.e., relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF), permeability (k(trans)), and leakage (v(e)), were quantified at each time point. The cellular, necrotic, and total volumes of lesion, together with the oedema volume, were also calculated.

RESULTS

All patients in group I and three in group II showed a significant decrease in all perfusion indices, together with the oedema volume, after 1 year. In these three patients in group II, increase in rCBV was associated with increased cellular volume fraction whereas the k(trans), v(e), and oedema volume decreased significantly after 4 months. In five patients in group II who underwent excision of the lesion after 4 months of therapy due to clinical deterioration, the decrease in rCBV was associated with significant increase in k(trans) and oedema volume without any significant change in lesion volume. The rCBV correlated significantly with the cellular volume, whereas k(trans) showed a significant correlation with the v(e) and oedema volume at each time point.

CONCLUSION

In BT, changes in k(trans) and oedema volume are associated with a therapeutic response at 4 months, even when there is a paradoxical increase in the lesion volume.

Novel Ist1-Did2 complex functions at a late step in multivesicular body sorting

In Saccharomyces cerevisiae, integral plasma membrane proteins destined for degradation and certain vacuolar membrane proteins are sorted into the lumen of the vacuole via the multivesicular body (MVB) sorting pathway, which depends on the sequential action of three endosomal sorting complexes required for transport. Here, we report the characterization of a new positive modulator of MVB sorting, Ist1. We show that endosomal recruitment of Ist1 depends on ESCRT-III. Deletion of IST1 alone does not cause cargo-sorting defects. However, synthetic genetic analysis of double mutants of IST1 and positive modulators of MVB sorting showed that ist1Delta is synthetic with vta1Delta and vps60Delta, indicating that Ist1 is also a positive component of the MVB-sorting pathway. Moreover, this approach revealed that Ist1-Did2 and Vta1-Vps60 compose two functional units. Ist1-Did2 and Vta1-Vps60 form specific physical complexes, and, like Did2 and Vta1, Ist1 binds to the AAA-ATPase Vps4. We provide evidence that the ist1Delta mutation exhibits a synthetic interaction with mutations in VPS2 (DID4) that compromise the Vps2-Vps4 interaction. We propose a model in which the Ist1-Did2 and Vta1-Vps60 complexes independently modulate late steps in the MVB-sorting pathway.

New component of ESCRT-I regulates endosomal sorting complex assembly

The endosomal sorting complex required for transport (ESCRT) complexes play a critical role in receptor down-regulation and retroviral budding. Although the crystal structures of two ESCRT complexes have been determined, the molecular mechanisms underlying the assembly and regulation of the ESCRT machinery are still poorly understood. We identify a new component of the ESCRT-I complex, multivesicular body sorting factor of 12 kD (Mvb12), and demonstrate that Mvb12 binds to the coiled-coil domain of the ESCRT-I subunit vacuolar protein sorting 23 (Vps23). We show that ESCRT-I adopts an oligomeric state in the cytosol, the formation of which requires the coiled-coil domain of Vps23, as well as Mvb12. Loss of Mvb12 results in the disassembly of the ESCRT-I oligomer and the formation of a stable complex of ESCRT-I and -II in the cytosol. We propose that Mvb12 stabilizes ESCRT-I in an oligomeric, inactive state in the cytosol to ensure that the ordered recruitment and assembly of ESCRT-I and -II is spatially and temporally restricted to the surface of the endosome after activation of the MVB sorting reaction.

Importin-alpha-16 is a translocon-associated protein involved in sorting membrane proteins to the nuclear envelope

A viral inner nuclear membrane-sorting motif sequence (INM-SM) was used to identify proteins that recognize integral membrane proteins destined for the INM. Herein we describe importin-alpha-16, a membrane-associated isoform of Spodoptera frugiperda importin-alpha that contains the C-terminal amino acid residues comprising armadillo helical-repeat domains 7-10. In the endoplasmic reticulum (ER) membrane, importin-alpha-16 is adjacent to the translocon protein Sec61alpha. Importin-alpha-16 cross-links to the INM-SM sequence as it emerges from the ribosomal tunnel and remains adjacent to the INM-SM after INM-SM integration into the ER membrane and release from the translocon. Cross-linking results suggest that importin-alpha-16 discriminates between INM- and non-INM-directed proteins. Thus, it seems that during and after cotranslational membrane integration, importin-alpha-16 is involved in the trafficking of integral membrane proteins to the INM.

Immune response towards lipid peroxidation products as a predictor of progression of non-alcoholic fatty liver disease to advanced fibrosis

AIMS

Factors responsible for the progression of non-alcoholic fatty liver disease (NAFLD) to more severe liver injury are poorly understood. In the present study, we investigated the association between immune reactions triggered by oxidative stress and stage of NAFLD.

METHODS

Titres of IgG against human serum albumin adducted with malondialdehyde (MDA-HSA) or arachidonic acid hydroperoxide (AAHP) and against oxidised cardiolipin (Ox-CL) were measured in 167 NAFLD patients with steatosis only (n = 79), steatohepatitis (n = 74), or steatosis plus cirrhosis (n = 14), and in 59 age and sex matched controls.

RESULTS

Circulating IgG against lipid peroxidation products was significantly higher (p<0.001) in NAFLD patients than in controls. Oxidative stress dependent immune responses were not associated with obesity, type 2 diabetes, or with serum cholesterol, ferritin, or aminotransferase levels. Titres of lipid peroxidation related antibodies were also independent of the extent of steatosis and were similarly distributed in patients with and without necroinflammation. In contrast, the same antibodies were significantly increased in patients with advanced fibrosis or cirrhosis. Logistic regression analysis confirmed that anti-MDA antibodies were independently associated with progression of NALFD and that NAFLD patients with titres of anti-MDA-HSA antibodies above the control threshold value had a threefold (relative risk 2.82 (95% confidence interval 1.35-5.90); p = 0.007) higher risk of having advanced fibrosis/cirrhosis than patients whose antibody titres were within the control range.

CONCLUSIONS

These results indicate that the presence of immune reactions triggered by oxidative stress can be an independent predictor of progression of NAFLD to advanced fibrosis.

Double-spanning plant viral movement protein integration into the endoplasmic reticulum membrane is signal recognition particle-dependent, translocon-mediated, and concerted

The current model for cell-to-cell movement of plant viruses holds that transport requires virus-encoded movement proteins that intimately associate with endoplasmic reticulum membranes. We have examined the early stages of the integration into endoplasmic reticulum membranes of a double-spanning viral movement protein using photocross-linking. We have discovered that this process is cotranslational and proceeds in a signal recognition particle-dependent manner. In addition, nascent chain photocross-linking to Sec61alpha and translocating chain-associated membrane protein reveal that viral membrane protein insertion takes place via the translocon, as with most eukaryotic membrane proteins, but that the two transmembrane segments of the viral protein leave the translocon and enter the lipid bilayer together.

Cotranslational integration and initial sorting at the endoplasmic reticulum translocon of proteins destined for the inner nuclear membrane

The current diffusion-retention model for protein trafficking to the inner nuclear membrane (INM) proposes that INM proteins diffuse laterally from the membrane of the endoplasmic reticulum into the INM and are then retained in the INM by binding to nuclear proteins or DNA. Because some data indicate that the sorting of baculovirus envelope proteins to the INM is protein-mediated, we have examined the early stages of INM protein integration and sorting by using photocrosslinking. Both viral and host INM-directed proteins were integrated cotranslationally through the endoplasmic reticulum translocon, and their nonrandom photocrosslinking to two translocon proteins, Sec61alpha and translocating chain-associated membrane protein (TRAM), revealed that the first transmembrane sequence (TMS) of each viral and host INM-directed protein occupied a very similar location within the translocon. Because few TMSs of non-INM-directed membrane proteins photocrosslink to TRAM, it seems that the INM-directed TMSs occupy different sites within the translocon than do non-INM-directed TMSs. The distinct proximities of translocon components to INM-directed TMSs strongly suggest that such TMSs are recognized and initially sorted within the translocon. Taken together, these data indicate that membrane protein sorting to the INM is an active process involving specific nonnuclear proteins.

Trafficking of ODV-E66 is mediated via a sorting motif and other viral proteins: facilitated trafficking to the inner nuclear membrane

The N-terminal 33 aa of the envelope protein ODV-E66 are sufficient to traffic fusion proteins to intranuclear membranes and the ODV envelope during infection with Autographa californica nucleopolyhedrovirus. This sequence has two distinct features: (i) an extremely hydrophobic sequence of 18 aa and (ii) positively charged amino acids close to the C-terminal end of the hydrophobic sequence. In the absence of infection, this sequence is sufficient to promote protein accumulation at the inner nuclear membrane. Covalent cross-linking results show that the lysines of the motif are proximal to FP25K and/or BV/ODV-E26 during transit from the endoplasmic reticulum to the nuclear envelope. We propose that the 33 aa comprise a signature for sorting proteins to the inner nuclear membrane (sorting motif) and that, unlike other resident proteins of the inner nuclear membrane, ODV-E66 and sortingmotif fusions do not randomly diffuse from their site of insertion at the endoplasmic reticulum to the nuclear envelope and viral-induced intranuclear membranes. Rather, during infection, trafficking is mediated by protein-protein interactions.

Regulation of butyrate uptake in Caco-2 cells by phorbol 12-myristate 13-acetate

Butyrate and the other short-chain fatty acids (SCFAs) are the most abundant anions in the colonic lumen. Also, butyrate is the preferred energy source for colonocytes and has been shown to regulate colonic electrolyte and fluid absorption. Previous studies from our group have demonstrated that the HCO(3)(-)/SCFA(-) anion exchange process is one of the major mechanisms of butyrate transport across the purified human colonic apical membrane vesicles and the apical membrane of human colonic adenocarcinoma cell line Caco-2 and have suggested that it is mainly mediated via monocarboxylate transporter-1 (MCT-1) isoform. However, little is known regarding the regulation of SCFA transport by various hormones and signal transduction pathways. Therefore, the present studies were undertaken to examine whether hydrocortisone and phorbol 12-myristate 13-acetate (PMA) are involved in a possible regulation of the butyrate/anion exchange process in Caco-2 cells. The butyrate/anion exchange process was assessed by measuring a pH-driven [(14)C]butyrate uptake in Caco-2 cells. Our results demonstrated that 24-h incubation with PMA (1 microM) significantly increased [(14)C]butyrate uptake compared with incubation with 4alphaPMA (inactive form). In contrast, incubation with hydrocortisone had no significant effect on butyrate uptake in Caco-2 cells compared with vehicle (ethanol) alone. Induction of butyrate uptake by PMA appeared to be via an increase in the maximum velocity (V(max)) of the transport process with no significant changes in the K(m) of the transporter for butyrate. Parallel to the increase in the V(max) of [(14)C]butyrate uptake, the MCT-1 protein level was also increased in response to PMA incubation. Our studies demonstrated that the butyrate/anion exchange was increased in response to PMA treatment along with the induction in the level of MCT-1 expression in Caco-2 cells.