The challenge of co-existence : from graft-versus-host disease to stable mixed chimerism after allogeneic hematopoietic stem cell transplantation

The only curative treatment strategy for many hematologic and inborn immunodeficiency disorders is an allogeneic hematopoietic stem cell transplantation (HSCT). The treatment involves replacing the entire hematopoietic system of the recipient. If successful, the underlying condition of the patient is resolved, the donor hematopoietic system engrafts and a tolerance between donor- and patient-derived cells is developed. Though the procedure of HSCT has been refined for decades, there are still several severe complications associated to it. Graft-versus-host disease (GVHD) is one of the most common and most feared complications post-HSCT, and is a result of donor graft-derived cells attacking recipient tissue. Despite improved GVHD treatment strategies, severe grade GVHD is still associated with high morbidity and mortality rates. A condition known as mixed chimerism (MC), where recipient hematopoietic cells co-exist with donor hematopoietic cells, may also be considered an adverse event early post-HSCT. This is certainly the case for patients with malignancies as it indicates a potential relapse. However, in rare cases where HSCT is performed due to non-malignant disorders, long-term stable MC may develop without any apparent signs of unfavourable symptoms. The papers in this thesis aim to provide a better understanding of the co-existence of graftand host-derived cells from an immunological perspective. I will focus on GVHD and longterm stable MC post-HSCT particularly. In Paper I, I aimed to identify predictive markers for acute GVHD development. Acute GVHD occurs relatively shortly post-HSCT with potential devastating effects. In this paper, I observed a reduced frequency in mucosal-associated-invariant T (MAIT) cells in donor grafts, given to patients who later developed acute GVHD. Moreover, I could identify a predictive role for high PD-1 and low CD127-expressing T cell frequencies in the donor grafts. Together with increased levels of TNFa in both the donor graft and in patient plasma prior to HSCT, these findings may putatively be used to predict acute GVHD development in patients at time of transplantation. In Paper II, I focused on chronic GVHD, a complication that usually develops later postHSCT presenting with symptoms from several organs. Patients may suffer from chronic GVHD for years, resulting in a diminished quality of life. In this paper, I was able to identify novel cellular subsets via mass cytometry that could be linked to the severity of chronic GVHD. These subsets could also be identified by conventional flow cytometry panels more suitable for routine laboratories. Additionally, similar to the study on acute GVHD, patients with more pronounced chronic GVHD were found to have fewer MAIT cells in their blood. Thus, Paper I and II indicate a potential role for MAIT cells in both acute and chronic GVHD. In Paper III and IV, the focus was long-term stable MC, which is defined as the presence of 5-95% recipient-derived cells, after ≥5 years post-HSCT in this study. Interestingly, patients with long-term stable MC had a similar quality of life, infectious disease burden and response to vaccines compared to patients with full donor chimerism (DC). Fluctuations in recipient chimerism tended to decrease and reach stable levels after around two to five years post-HSCT. Moreover, patients with MC appear to retain functional recipient-derived cells in multiple cellular subsets. Patients with MC also displayed increased levels of IgG3 and reduced lymphocyte expression of ZAP-70, though they were found to be similar to patients with DC in overall immune phenotype

Wolven en zwijnen, acceptabel risico?

Wolven keren terug naar Nederland. De vraag is niet of, maar wanneer ze vanuit Duitsland hier naartoe migreren. In die context is het belangrijk om te weten hoe Nederlanders reageren op het risico van grote wilde dieren. Zien we de aanwezigheid van de wolf als een groot risico, of valt er wel mee te leven? En hoe zit dat voor het eveneens gevaarlijke wilde zwijn. Welke factoren spelen een rol bij risicoperceptie en -acceptatie van groot wild

Simulating progressive motor neuron degeneration and collateral reinnervation in motor neuron diseases using a dynamic muscle model based on human single motor unit recordings

Objective.To simulate progressive motor neuron loss and collateral reinnervation in motor neuron diseases (MNDs) by developing a dynamic muscle model based on human single motor unit (MU) surface-electromyography (EMG) recordings.Approach.Single MU potentials recorded with high-density surface-EMG from thenar muscles formed the basic building blocks of the model. From the baseline MU pool innervating a muscle, progressive MU loss was simulated by removal of MUs, one-by-one. These removed MUs underwent collateral reinnervation with scenarios varying from 0% to 100%. These scenarios were based on a geometric variable, reflecting the overlap in MU territories using the spatiotemporal profiles of single MUs and a variable reflecting the efficacy of the reinnervation process. For validation, we tailored the model to generate compound muscle action potential (CMAP) scans, which is a promising surface-EMG method for monitoring MND patients. Selected scenarios for reinnervation that matched observed MU enlargements were used to validate the model by comparing markers (including the maximum CMAP and a motor unit number estimate (MUNE)) derived from simulated and recorded CMAP scans in a cohort of 49 MND patients and 22 age-matched healthy controls.Main results.The maximum CMAP at baseline was 8.3 mV (5th-95th percentile: 4.6 mV-11.8 mV). Phase cancellation caused an amplitude drop of 38.9% (5th-95th percentile, 33.0%-45.7%). To match observations, the geometric variable had to be set at 40% and the efficacy variable at 60%-70%. The Δ maximum CMAP between recorded and simulated CMAP scans as a function of fitted MUNE was -0.4 mV (5th-95th percentile = -4.0 - +2.4 mV).Significance.The dynamic muscle model could be used as a platform to train personnel in applying surface-EMG methods prior to their use in clinical care and trials. Moreover, the model may pave the way to compare biomarkers more efficiently, without directly posing unnecessary burden on patients.</p

Diagnostic accuracy of nerve excitability and compound muscle action potential scan-derived biomarkers in amyotrophic lateral sclerosis

BACKGROUND AND PURPOSE: The lack of reliable early biomarkers still causes substantial diagnostic delays in amyotrophic lateral sclerosis (ALS). The aim was to assess the diagnostic accuracy of a novel electrophysiological protocol in patients with suspected motor neuron disease (MND). METHODS: Consecutive patients with suspected MND were prospectively recruited at our tertiary referral centre for MND in Utrecht, The Netherlands. Procedures were performed in accordance with the Standards for Reporting of Diagnostic Accuracy. In addition to the standard diagnostic workup, an electrophysiological protocol of compound muscle action potential (CMAP) scans and nerve excitability tests was performed on patients' thenar muscles. The combined diagnostic yield of nerve excitability and CMAP scan based motor unit number estimation was compared to the Awaji and Gold Coast criteria and their added value was determined. RESULTS: In all, 153 ALS or progressive muscular atrophy patients, 63 disease controls and 43 healthy controls were included. Our electrophysiological protocol had high diagnostic accuracy (area under the curve [AUC] 0.85, 95% confidence interval [95% CI] 0.80-0.90), even in muscles with undetectable axon loss (AUC 0.78, 95% CI 0.70-0.85) and in bulbar-onset patients (AUC 0.85, 95% CI 0.73-0.95). Twenty-four of 33 (73%) ALS patients who could not be diagnosed during the same visit were correctly identified, as well as 8/13 (62%) ALS patients not meeting the Gold Coast criteria and 49/59 (83%) ALS patients not meeting the Awaji criteria during this first visit. CONCLUSIONS: Our practical and non-invasive electrophysiological protocol may improve early diagnosis in clinically challenging patients with suspected ALS. Routine incorporation may boost early diagnosis, enhance patient selection and generate baseline measures for clinical trials

Simulating progressive motor neuron degeneration and collateral reinnervation in motor neuron diseases using a dynamic muscle model based on human single motor unit recordings

Objective.To simulate progressive motor neuron loss and collateral reinnervation in motor neuron diseases (MNDs) by developing a dynamic muscle model based on human single motor unit (MU) surface-electromyography (EMG) recordings. Approach.Single MU potentials recorded with high-density surface-EMG from thenar muscles formed the basic building blocks of the model. From the baseline MU pool innervating a muscle, progressive MU loss was simulated by removal of MUs, one-by-one. These removed MUs underwent collateral reinnervation with scenarios varying from 0% to 100%. These scenarios were based on a geometric variable, reflecting the overlap in MU territories using the spatiotemporal profiles of single MUs and a variable reflecting the efficacy of the reinnervation process. For validation, we tailored the model to generate compound muscle action potential (CMAP) scans, which is a promising surface-EMG method for monitoring MND patients. Selected scenarios for reinnervation that matched observed MU enlargements were used to validate the model by comparing markers (including the maximum CMAP and a motor unit number estimate (MUNE)) derived from simulated and recorded CMAP scans in a cohort of 49 MND patients and 22 age-matched healthy controls. Main results.The maximum CMAP at baseline was 8.3 mV (5th-95th percentile: 4.6 mV-11.8 mV). Phase cancellation caused an amplitude drop of 38.9% (5th-95th percentile, 33.0%-45.7%). To match observations, the geometric variable had to be set at 40% and the efficacy variable at 60%-70%. The Δ maximum CMAP between recorded and simulated CMAP scans as a function of fitted MUNE was -0.4 mV (5th-95th percentile = -4.0 - +2.4 mV). Significance.The dynamic muscle model could be used as a platform to train personnel in applying surface-EMG methods prior to their use in clinical care and trials. Moreover, the model may pave the way to compare biomarkers more efficiently, without directly posing unnecessary burden on patients

Revisiting distinct nerve excitability patterns in patients with amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a devastating neurodegenerative disease, characterized by loss of central and peripheral motor neurons. Although the disease is clinically and genetically heterogeneous, axonal hyperexcitability is a commonly observed feature that has been suggested to reflect an early pathophysiological step linked to the neurodegenerative cascade. Therefore, it is important to clarify the mechanisms causing axonal hyperexcitability and how these relate to the clinical characteristics of patients. Measures derived directly from a nerve excitability recording are frequently used as study end points, although their biophysical basis is difficult to deduce. Mathematical models can aid in the interpretation but are reliable only when applied to group-averaged recordings. Consequently, model estimates of membrane properties cannot be compared with clinical characteristics or treatment effects in individual patients, posing a considerable limitation in heterogeneous diseases, such as amyotrophic lateral sclerosis. To address these challenges, we revisited nerve excitability using a new pattern analysis-based approach (principal component analysis). We evaluated disease-specific patterns of excitability changes and established their biophysical origins. Based on the observed patterns, we developed new compound measures of excitability that facilitate the implementation of this approach in clinical settings. We found that excitability changes in amyotrophic lateral sclerosis patients (n = 161, median disease duration = 11 months) were characterized by four unique patterns compared with controls (n = 50, age and sex matched). These four patterns were best explained by changes in resting membrane potential (modulated by Na+/K+ currents), slow potassium and sodium currents (modulated by their gating kinetics) and refractory properties of the nerve. Consequently, we were able to show that altered gating of slow potassium channels was associated with, and predictive of, the rate of progression of the disease on the amyotrophic lateral sclerosis functional rating scale. Based on these findings, we designed four composite measures that capture these properties to facilitate implementation outside this study. Our findings demonstrate that changes in nerve excitability in patients with amyotrophic lateral sclerosis are dominated by four distinct patterns, each with a distinct biophysical origin. Based on this new approach, we provide evidence that altered slow potassium-channel function might play a role in the rate of disease progression. The magnitudes of these patterns, quantified using a similar approach or our new composite measures, have potential as efficient measures to study membrane properties directly in amyotrophic lateral sclerosis patients, and thus aid prognostic stratification and trial design

Motor Unit Integrity in Multifocal Motor Neuropathy: A Systematic Evaluation with CMAP Scans

Introduction/Aims: Progressive axonal loss in multifocal motor neuropathy (MMN) is often assessed with nerve conduction studies (NCS), by recording maximum compound muscle action potentials (CMAPs). However, reinnervation maintains the CMAP amplitude until a significant portion of the motor unit (MU) pool is lost. Therefore, we performed more informative CMAP scans to study MU characteristics in a large cohort of patients with MMN. Methods: We derived the maximum CMAP amplitude (CMAP max), an MU number estimate (MUNE), and the largest MU amplitude stimulus current required to elicit 5%, 50%, and 95% of CMAP max (S5, S50, S95) and relative ranges ([S95 − S5] × 100 / S50) from the scans. These metrics were compared with clinical, laboratory, and NCS results. Results: Forty MMN patients and 24 healthy controls were included in the study. CMAP max and MUNE were reduced in MMN patients (both P <.001). Largest MU amplitude as a percentage of CMAP max was increased in MMN patients (P <.001). Disease duration and treatment duration were not associated with MUNE. Relative range was larger in patients with anti-GM1 antibodies than in those without anti-GM1 antibodies (P =.016) and controls (P <.001). The largest MU amplitudes were larger in patients without anti-GM1 antibodies than in patients with anti-GM1 antibodies (P =.037) and controls (P =.044). Discussion: We found that MU loss is common in MMN and accompanied by enlarged MUs. Presence of anti-GM1 antibodies was associated with increased relative range of MU thresholds and reduction in largest MU amplitude. Our findings indicate that CMAP scans complement routine NCS, and may have potential for practical monitoring of treatment efficacy and disease progression

Feasibility and tolerability of multimodal peripheral electrophysiological techniques in a cohort of patients with spinal muscular atrophy

Objective: Electrophysiological techniques are emerging as an aid in identifying prognostic or therapeutic biomarkers in patients with spinal muscular atrophy (SMA), but electrophysiological assessments may be burdensome for patients. We, therefore, assessed feasibility and tolerability of multimodal peripheral non-invasive electrophysiological techniques in a cohort of patients with SMA. Methods: We conducted a single center, longitudinal cohort study investigating the feasibility and tolerability of applying multimodal electrophysiological techniques to the median nerve unilaterally. Techniques consisted of the compound muscle action potential scan, motor nerve excitability tests, repetitive nerve stimulation and sensory nerve action potential. We assessed tolerability using the numeric rating scale (NRS), ranging from 0 (no pain) to 10 (worst possible pain), and defined the protocol to be tolerable if the NRS score ≤ 3. The protocol was considered feasible if it could be performed according to test and quality standards. Results: We included 71 patients with SMA types 1–4 (median 39 years; range 13–67) and 63 patients at follow-up. The protocol was feasible in 98% of patients and was well-tolerated in up to 90% of patients. Median NRS score was 2 (range 0–6 at baseline and range 0–4 at follow-up (p < 0.01)). None of the patients declined follow-up assessment. Conclusions: Multimodal, peripheral, non-invasive, electrophysiological techniques applied to the median nerve are feasible and well-tolerated in adolescents and adults with SMA types 1–4. Significance: Our study supports the use of non-invasive multimodal electrophysiological assessments in adolescents and adults with SMA types 1–4