Case report: Successful treatment with daratumumab for pure red cell aplasia in a patient with mixed lymphoid chimerism after ABO-mismatched stem cell transplant for sickle cell disease

Pure red cell aplasia (PRCA) is a serious complication after ABO-mismatched allogeneic hematopoietic stem cell transplantation (HSCT). Following HSCT, persistent anti-donor isohemagglutinins against donor ABO antigens are considered the immunological cause of PRCA. Patients with post-transplant PRCA are at risk for graft rejection and prolonged red blood cell transfusion dependency. No standard treatment exists. Recently however, the anti-CD38 monoclonal antibody daratumumab has been reported to be an effective treatment for post-transplant PRCA in patients with complete donor chimerism. Here, we describe the first case of PRCA in a patient with mixed lymphoid patient/donor chimerism that was successfully treated with daratumumab. This is also the first report of a transplant recipient with sickle cell disease who was treated with this relatively new approach. Fourteen months post-transplantation and twelve months after treatment with daratumumab, our patient has a normal complete blood count and the anti-donor isohemagglutinins remain undetectable despite mixed lymphoid chimerism. Mixed chimerism is a common manifestation in adult patients with sickle cell disease transplanted with non-myeloablative conditioning and a matched sibling donor. The application of non-myeloablative HSCT for patients with sickle cell disease is steadily increasing. Therefore, the incidence of PRCA in this setting might also increase. As the risk of graft rejection due to PRCA can be especially high in patients with mixed chimerism, clinicians should be aware that daratumumab can be an effective treatment in the setting of mixed chimerism

Explaining the Statistical Properties of Salt Intrusion in Estuaries Using a Stochastic Dynamical Modeling Approach

Determining the statistical properties of salt intrusion in estuaries on sub-tidal time scales is a substantial challenge in environmental modeling. To study these properties, we here extend an idealized deterministic salt intrusion model to a stochastic one by including a stochastic model of the river discharge. In the river discharge model, two types of stochastic forcing are used: one independent (additive noise) and one dependent (multiplicative noise) on the river discharge state. Each type of forcing results in a non-Gaussian response in the salt intrusion length, which we consider here as the distance of the 2 psu isohaline contour to the estuary mouth. The salt intrusion model including both types of stochastic forcing in the river discharge provides a satisfactory explanation of the multi-year statistics of observed salt intrusion lengths in the San Francisco Bay estuary, in particular for the skewness of its probability density function

Estuarine Salinity Response to Freshwater Pulses

Freshwater pulses (during which river discharge is much higher than average) occur in many estuaries and strongly impact estuarine functioning. To gain insight into the estuarine salinity response to freshwater pulses, an idealized model is presented. With respect to earlier models on the spatiotemporal behavior of salinity in estuaries, it includes additional processes that provide a more detailed vertical structure of salinity. Simulation of an observed salinity response to a freshwater pulse in the Guadalquivir Estuary (Spain) shows that this is important to adequately simulate the salinity structure. The model is used to determine the dependency of the estuarine salinity response to freshwater pulses for different background discharge, tides, and different intensities and durations of the pulses. Results indicate that the change in salt intrusion length due to a freshwater pulse is proportional to the ratio between peak and background river discharge and depends linearly on the duration of the pulse if there is no equilibration during the pulse. The adjustment time, which is the time it takes for the estuary to reach equilibrium after an increase in river discharge, scales with the ratio of the change in salt intrusion length and the peak river discharge. The recovery time, that is, the time it takes for the estuary to reach equilibrium after a decrease in river discharge, does not depend on the amount of decrease in salt intrusion length caused by the pulse. The strength of the tides is of minor importance to the salt dynamics during and after the pulse

Salt intrusion and effective longitudinal dispersion in man-made canals, a simplified model approach

Salinization threatens coastal freshwater bodies, but little is known about this phenomenon in man-made canals. Here, salt intrusion and effective longitudinal dispersion in such canals are investigated, where the Ghent-Terneuzen Canal in Belgium-the Netherlands is used as a prototype example. A calibrated, width-averaged model is employed to quantify the sensitivity of these quantities to forcing conditions. This model performs better than a calibrated, cross-sectionally averaged model with a constant longitudinal dispersion coefficient, because density-driven advection of salt, which turns out to be important in man-made canals, is explicitly resolved. It is found that, in equilibrium, discharge at the upstream boundary is more important than exterior salinity for salt intrusion and effective longitudinal dispersion. Furthermore, the time-dependent salinity response to an increase in freshwater discharge is faster than that to a decrease in discharge. In contrast, the time it takes the system to adjust to a change in the exterior salinity does not depend on the sign of that change. From these results, a parametrization of the effective longitudinal dispersion coefficient is developed, which explicitly accounts for the horizontal salt transport by the density-driven current. A cross-sectionally averaged model that uses this effective longitudinal dispersion coefficient successfully simulates the salt dynamics of the width-averaged model

Health Outcomes and Cost-effectiveness of Monoclonal SARS-CoV-2 Antibodies as Pre-exposure Prophylaxis

Importance: Pre-exposure prophylaxis with neutralizing SARS-CoV-2 monoclonal antibodies (mAbs PrEP) prevents infection and reduces hospitalizations and the duration thereof for COVID-19 and death among high-risk individuals. However, reduced effectiveness due to a changing SARS-CoV-2 viral landscape and high drug prices remain substantial implementation barriers. Objective: To assess the cost-effectiveness of mAbs PrEP as COVID-19 PrEP. Design, Setting, and Participants: For this economic evaluation, a decision analytic model was developed and parameterized with health care outcome and utilization data from individuals with high risk for COVID-19. The SARS-CoV-2 infection probability, mAbs PrEP effectiveness, and drug pricing were varied. All costs were collected from a third-party payer perspective. Data were analyzed from September 2021 to December 2022. Main Outcomes and Measures: Health care outcomes including new SARS-CoV-2 infections, hospitalization, and deaths. The cost per death averted and cost-effectiveness ratios using a threshold for prevention interventions of $22000 or less per quality-adjusted life year (QALY) gained. Results: The clinical cohort consisted of 636 individuals with COVID-19 (mean [SD] age 63 [18] years; 341 [54$275 and 75% or higher effectiveness. With a 100% effectiveness mAbs PrEP can reduce ward admissions by 70%, ICU admissions by 97%, and deaths by 92%. Drug prices, however, need to reduce to $550 for cost-effectiveness ratios less than$22000 per QALY gained per death averted and to $2200 for ratios between$22000 and $88000. Conclusions and Relevance: In this study, use of mAbs PrEP for preventing SARS-CoV-2 infections was cost-saving at the beginning of an epidemic wave (high infection probability) with 75$275. These results are timely and relevant for decision-makers involved in mAbs PrEP implementation. When newer mAbs PrEP combinations become available, guidance on implementation should be formulated ensuring a fast rollout. Nevertheless, advocacy for mAbs PrEP use and critical discussion on drug prices are necessary to ensuring cost-effectiveness for different epidemic settings.</p

The role of tunneling in enzyme catalysis of C–H activation

AbstractRecent data from studies of enzyme catalyzed hydrogen transfer reactions implicate a new theoretical context in which to understand C–H activation. This is much closer to the Marcus theory of electron transfer, in that environmental factors influence the probability of effective wave function overlap from donor to acceptor atoms. The larger size of hydrogen and the availability of three isotopes (H, D and T) introduce a dimension to the kinetic analysis that is not available for electron transfer. This concerns the role of gating between donor and acceptor atoms, in particular whether the system in question is able to tune distance between reactants to achieve maximal tunneling efficiency. Analysis of enzyme systems is providing increasing evidence of a role for active site residues in optimizing the inter-nuclear distance for nuclear tunneling. The ease with which this optimization can be perturbed, through site-specific mutagenesis or an alteration in reaction conditions, is also readily apparent from an analysis of the changes in the temperature dependence of hydrogen isotope effects

Impairment of cerebrovascular hemodynamics in patients with severe and milder forms of sickle cell disease

In patients with sickle cell disease (SCD), cerebral blood flow (CBF) is elevated to counteract anemia and maintain oxygen supply to the brain. This may exhaust the vasodilating capacity of the vessels, possibly increasing the risk of silent cerebral infarctions (SCI). To further investigate cerebrovascular hemodynamics in SCD patients, we assessed CBF, arterial transit time (ATT), cerebrovascular reactivity of CBF and ATT (CVRCBF and CVRATT) and oxygen delivery in patients with different forms of SCD and matched healthy controls. We analyzed data of 52 patients with severe SCD (HbSS and HbS beta(0)-thal), 20 patients with mild SCD (HbSC and HbS beta(+)-thal) and 10 healthy matched controls (HbAA and HbAS). Time-encoded arterial spin labeling (ASL) scans were performed before and after a vasodilatory challenge using acetazolamide (ACZ). To identify predictors of CBF and ATT after vasodilation, regression analyses were performed. Oxygen delivery was calculated and associated with hemoglobin and fetal hemoglobin (HbF) levels. At baseline, severe SCD patients showed significantly higher CBF and lower ATT compared to both the mild SCD patients and healthy controls. As CBFpostACZ was linearly related to CBFpreACZ, CVRCBF decreased with disease severity. CVRATT was also significantly affected in severe SCD patients compared to mild SCD patients and healthy controls. Considering all groups, women showed higher CBFpostACZ than men (p < 0.01) independent of baseline CBF. Subsequently, post ACZ oxygen delivery was also higher in women (p < 0.05). Baseline, but not post ACZ, GM oxygen delivery increased with HbF levels. Our data showed that baseline CBF and ATT and CVRCBF and CVRATT are most affected in severe SCD patients and to a lesser extent in patients with milder forms of SCD compared to healthy controls. Cerebrovascular vasoreactivity was mainly determined by baseline CBF, sex and HbF levels. The higher vascular reactivity observed in women could be related to their lower SCI prevalence, which remains an area of future work. Beneficial effects of HbF on oxygen delivery reflect changes in oxygen dissociation affinity from hemoglobin and were limited to baseline conditions suggesting that high HbF levels do not protect the brain upon a hemodynamic challenge, despite its positive effect on hemolysis.Neuro Imaging Researc

Gall-bladder dysmotility - A risk factor for gall-stone formation in hypertriglyceridaemia and reversal on triglyceride-lowering therapy with bezafibrate and fish oil

Doel: Onderzoeken van de pathofysiologische mechanismen die de kans op galstenen verhogen bij hypertriglyceridemie (HTG) en het vergelijken van de effecten van triglycerideverlagende therapie met bezafibraat en visolie op determinanten van cholelithiasis (biliaire lipidesamenstelling en galblaasmotoriek) bij HTG-patiënten.Opzet: Gekruiste opzet met ‘random’-volgorde.Patiënten en methoden: De galblaasmotoriek werd postprandiaal en tijdens cholecystokinine(CCK)-infusie echografisch onderzocht. De determinanten van cholelithiasis en de serumlipiden werden vergeleken tussen 9 HTG-patiënten en 10 normolipidemische controlepersonen van hetzelfde geslacht, dezelfde leeftijd en ‘body mass’-index. Bij de HTG-patiënten werden de effecten van bezafibraat en gezuiverde omega-3-olie (‘visolie’) bepaald.Resultaten: De serumtriglyceride(TG)-spiegel van de HTG-patiënten was 14-voudig verhoogd, vergeleken met de controlepersonen. De lipidesamenstelling van de gal, de nuchtere galblaasvolumen en de serum-CCK-spiegels verschilden niet tussen HTG-patiënten en controlepersonen. De galblaaslediging was verminderd bij HTG-patiënten versus controlepersonen tijdens CCK-infusie (–22) en ook na een maaltijd (–37; beide p &lt; 0,001). De postprandiale serum-CCK-spiegels waren significant hoger bij HTG-patiënten. Zowel bezafibraat als visolie verlaagde de serum-TG-spiegel (–68 en –51 ten opzichte van de uitgangswaarde; beide: p &lt; 0,01). Nuchtere CCK-spiegels verschilden niet, terwijl de CCK-geïnduceerde galblaaslediging onder bezafibraat toenam met 29 (p &lt; 0,001) en met visolie met 13 (p = 0,07). De postprandiale galblaasmotoriek verbeterde tijdens zowel bezafibraat- (+47) als visoliebehandeling (+25; beide: p &lt; 0,02), waarschijnlijk gedeeltelijk door een toegenomen gevoeligheid van de galblaas voor CCK (voor beide: p &lt; 0,05 vergeleken met de uitgangsfase). Bezafibraat, in tegenstelling tot visolie, verhoogde de molaire cholesterol-galzuurratio (+40; p ≤ 0,05), terwijl beide behandelingen geen effect hadden op de cholesterolsaturatie-index.Conclusies: De verminderde galblaasmotoriek bij HTG-patiënten lijkt het gevolg te zijn van verminderde gevoeligheid voor CCK, wat kan bijdragen aan het verhoogde risico op galsteenvorming. Bij HTG-patiënten verbetert triglycerideverlagende therapie met visolie of bezafibraat de verminderde galblaasmotoriek zonder nadelig effect op de biliaire cholesterolverzadiging.Objective. To unravel the mechanisms responsible for the increased risk of gall-stone disease in hypertriglyceridaemia (HTG) and to compare the effects of triglyceride-lowering therapy with bezafibrate and fish oil on determinants of cholelithiasis (biliary-lipid composition and gall-bladder motility) in HTG patients. Design. Randomised cross over. Patients and methods. Gall-bladder motility (ultrasonography) was studied postprandially and during infusion of cholecystokinin (CCK). Determinants of cholelithiasis and serum lipids were compared between 9 HTG patients and 10 age, sex and body-mass index matched normolipidaemic controls. The effects of bezafibrate and purified omega-3-oil ('fish oil') in HTG patients were studied. Results. HTG patients showed 14-fold higher serum-triglyceride (TG) levels than controls. Biliary-lipid composition, fasting gall-bladder volumes, and CCK levels did not differ between HTG patients and controls. Gall-bladder emptying was reduced in HTG patients compared with controls during CCK infusion (-22%) as well as in response to a meal (-37%; both p &lt; 0.001). Postprandial CCK levels were significantly higher in HTG patients. Both bezafibrate and fish oil reduced serum TG levels (-68 and -51% versus baseline, respectively; both p &lt; 0.01). Fasting CCK levels were not affected whereas CCK-induced gall-bladder emptying increased during bezafibrate (+29%; p &lt; 0.001) and tended to increase upon fish-oil therapy (+13%; p = 0.07). Postprandial gall-bladder motility improved at least partly with bezafibrate and fish oil (+47 and +25% versus baseline, respectively; both p &lt; 0.02) due to increased gallbladder sensitivity to CCK (both p &lt; 0.05 versus baseline). Bezafibrate but not fish oil increased the molar ratio of cholesterol to bile acids (+40%; p ≤ 0.05), but no effects on the cholesterol-saturation index were seen with either treatment. Conclusions. We suggest that impaired gall-bladder motility occurs in HTG patients due to decreased sensitivity to CCK, which may add to the enhanced risk of gall-stone disease in HTG patients. Triglyceride-lowering therapy by both fish oil and bezafibrate improves gall-bladder dysmotility without adversely affecting biliary-cholesterol saturation.</p