Overactivated complement is a high-risk feature in HSCT recipients with transplant associated thrombotic microangiopathy (TA-TMA), and untreated patients have dismal outcomes. We present our experience of 64 pediatric HSCT recipients with high risk TA-TMA and multi-organ injury treated with the complement blocker eculizumab. We demonstrate significant improvement in 1y post-HSCT survival to 66% in treated patients from our previously reported untreated cohort with same high-risk TA-TMA features that had 1y post-HSCT survival of 16.7%. Responding patients benefited from a brief but intensive eculizumab therapy course using PK/PD guided dosing, requiring a median of 11 doses of eculizumab (IQR 7-20). Therapy was discontinued due to resolution of TA-TMA at a median of 66 days (IQR 41-110). Subjects with higher complement activation measured by elevated blood sC5b-9 at the start of therapy were less likely to respond to treatment (OR =0.15, p-value 0.0014), and required more doses of eculizumab [r = 0.43, p-value = 0.0004]. Patients with intestinal bleeding had the fastest eculizumab clearance, required the highest number of eculizumab doses (20 vs 9, p=0.0015), and had lower 1y survival (44% vs 78%, p=0.01). Over 70% of survivors had proteinuria on long term follow up. The best GFR recovery in survivors was a median 20% lower (IQR 7.3-40.3%) than their pre-HSCT GFR. In summary, complement blockade with eculizumab is an effective therapeutic strategy for high risk TA-TMA, but some patients with severe disease lack a complete response, prompting us to propose early intervention strategies and search for additional targetable endothelial injury pathways.

Complementary cyclisation reactions of hex-2-ene-1,6-diamine derivatives were exploited in the synthesis of alternative molecular scaffolds. The value of the synthetic approach was analysed using LLAMA, an open-access computational tool for assessing the lead-likeness and novelty of molecular scaffolds.

Hematopoietic stem cell transplantation (HSCT)-associated thrombotic microangiopathy (TA-TMA) is an understudied complication of HSCT that significantly affects transplant-related morbidity and mortality. Over the past several decades, the cause of TA-TMA has remained unknown, limiting treatment options to non-specific therapies adapted from other diseases. Recent prospective studies dedicated to the study of TA-TMA have provided new insights into the pathogenesis of, and genetic susceptibility to TA-TMA, raising awareness of this important transplant complication and allowing for the identification of potentially novel therapeutic targets. Specifically, many patients with TA-TMA develop multi-organ tissue injury through endothelial damage mediated by the activation of the complement pathway, leading to rational therapeutic strategies including complement blockade. This new knowledge has the potential to favorably influence clinical practice and change the standard of care for how patients with TA-TMA are managed. In this review, we summarize novel approaches to the recognition and management of TA-TMA, using case examples to illustrate key clinical points that hopefully lead to improved short and long-term outcomes for these complex HSCT patients, who remain at significant risk for treatment-related morbidity and mortality.

The transverse (t-) tubules of cardiac ventricular myocytes are invaginations of the surface membrane that form a complex network within the cell. Many of the key proteins involved in excitation-contraction coupling appear to be located predominantly at the t-tubule membrane.Despite their importance, the fraction of cell membrane within the t-tubules remains unclear: measurement of cell capacitance following detubulation suggests ~32%, whereas optical measurements suggest up to ~65%. We have therefore investigated the factors that may account for this discrepancy. Calculation of the combinations of t-tubule radius, length and density that produce t-tubular membrane fractions of 32% or 56% suggest that the true fraction is at the upper end of this range. Assessment of detubulation using confocal and electron microscopy suggests that incomplete detubulation can account for some, but not all of the difference. High cholesterol, and a consequent decrease in specific capacitance, in the t-tubule membrane, may also cause the ttubule fraction calculated from the loss of capacitance following detubulation to be underestimated. Correcting for both of these factors results in an estimate that is still lower than that obtained from optical measurements suggesting either that optical methods overestimate the fraction of membrane in the t-tubules, or that other, unknown, factors, reduce the apparent fraction obtained by detubulation. A biophysically realistic computer model of a rat ventricular myocyte, incorporating a t-tubule network, is used to assess the effect of the altered estimates of t-tubular membrane fraction on the calculated distribution of ion flux pathways.

Objective: To determine if more widespread cognitive deficits are present in a narrowly defined group of patients with the amnestic form of mild cognitive impairment (MCI). Methods: From a larger sample of patients clinically diagnosed as meeting the criteria of Petersen et al. for amnestic MCI, we selected 22 subjects who had Clinical Dementia Rating scores of zero on all domains besides memory and orientation. These MCI subjects with presumably isolated memory impairments were compared to 35 age-matched normal controls and 33 very mild Alzheimer’s disease (AD) patients on a battery of neuropsychological tests. Result: In addition to the expected deficits in episodic memory, the amnestic MCI group performed less well than the controls but better than the AD group on design fluency, category fluency, a set shifting task and the Stroop interference condition. Over half the amnestic MCI group (vs. none of the normal controls) scored at least 1 standard deviation below control means on 4 or more of the nonmemory cognitive tasks. Conclusions: Isolated memory impairment may be fairly uncommon in clinically diagnosed amnestic MCI patients, even when the criteria for amnestic MCI are fairly narrow. Additional cognitive impairments are likely to include fluency and executive functioning. These more diffuse deficits argue for comprehensive cognitive assessments, even when the patient and family are reporting only memory decline, and are consistent with the increase in attention paid to the heterogeneity of MCI.

We describe our retrospective clinical experience with ruxolitinib for steroid-refractory acute graft-versus-host disease (GVHD) in pediatric allogeneic hematopoietic stem cell transplant (HSCT) patients. Ruxolitinib was administered orally at 5 mg twice daily for children ≥ 25 kg or 2.5 mg twice daily if <25 kg. We excluded patients who received new immune suppressive agents within 2 weeks before initiation of ruxolitinib from response analysis. Patients were called a treatment failure if ruxolitinib was stopped before completion of 4 weeks of therapy because of adverse effects and not because of progression of acute GVHD. Thirteen patients received ruxolitinib, and 11 patients were assessable for response. One patient achieved a complete response, 4 had a partial response, and 2 had no response at 4 weeks after the first ruxolitinib dose. Four patients were treatment failures. Overall response rate was 45%. Adverse effects (n = 13) included grades 3 to 4 elevated alanine transaminase (n = 7), grades 3 to 4 neutropenia (n = 5), and grade 4 thrombocytopenia (n = 3). Infectious complications in patients included for response analysis (n = 11) were Epstein-Barr viremia (n = 2), adenovirus (n = 2), BK (n = 3), bacterial infections (n = 6), and fungal infections (n = 1). Seven of 13 patients were alive at a median follow-up of 401 days (range, 219 to 969) after HSCT. We observed a high rate of reversible adverse effects in children with steroid-refractory acute GVHD and a fair overall response of ruxolitinib as a salvage therapeutic agent. Further pharmacokinetic studies are needed to determine the best-tolerated dose of ruxolitinib that will achieve efficacy without significant adverse effects.

Protein–protein interactions (PPIs) are vital to all biological processes. These interactions are often dynamic, sometimes transient, typically occur over large topographically shallow protein surfaces, and can exhibit a broad range of affinities. Considerable progress has been made in determining PPI structures. However, given the above properties, understanding the key determinants of their thermodynamic stability remains a challenge in chemical biology. An improved ability to identify and engineer PPIs would advance understanding of biological mechanisms and mutant phenotypes and also provide a firmer foundation for inhibitor design. In silico prediction of PPI hot-spot amino acids using computational alanine scanning (CAS) offers a rapid approach for predicting key residues that drive protein–protein association. This can be applied to all known PPI structures; however there is a trade-off between throughput and accuracy. Here we describe a comparative analysis of multiple CAS methods, which highlights effective approaches to improve the accuracy of predicting hot-spot residues. Alongside this, we introduce a new method, BUDE Alanine Scanning, which can be applied to single structures from crystallography and to structural ensembles from NMR or molecular dynamics data. The comparative analyses facilitate accurate prediction of hot-spots that we validate experimentally with three diverse targets: NOXA-B/MCL-1 (an α-helix-mediated PPI), SIMS/SUMO, and GKAP/SHANK-PDZ (both β-strand-mediated interactions). Finally, the approach is applied to the accurate prediction of hot-spot residues at a topographically novel Affimer/BCL-xL protein–protein interface.

Mucosal barrier injury laboratory-confirmed bloodstream infections (MBI-LCBIs) lead to significant morbidity, mortality, and healthcare resource utilization in hematopoietic stem cell transplant (HSCT) patients. Determination of the healthcare burden of MBI-LCBIs and identification of patients at risk of MBI-LCBIs will allow researchers to identify strategies to reduce MBI-LCBI rates. The objective of our study was to describe the incidence, risk factors, timing, and outcomes of MBI-LCBIs in hematopoietic stem cell transplant patients. We performed a retrospective analysis of 374 patients who underwent HSCT at a large free-standing academic children’s hospital to determine the incidence, risk factors, and outcomes of patients that developed a bloodstream infection (BSI) including MBI-LCBI, central line–associated BSI (CLABSI), or secondary BSI in the first year after HSCT. Outcome measures included nonrelapse mortality (NRM), central venous catheter removal within 7 days of positive culture, shock, admission to the pediatric intensive care unit (PICU) within 48 hours of positive culture, and death within 10 days of positive culture. One hundred seventy BSIs were diagnosed in 100 patients (27%): 80 (47%) MBI-LCBIs, 68 (40%) CLABSIs, and 22 (13%) secondary infections. MBI-LCBIs were diagnosed at a significantly higher rate in allogeneic HSCT patients (18% versus 7%, P = .007). Reduced-intensity conditioning (OR, 1.96; P = .015) and transplant-associated thrombotic microangiopathy (OR, 2.94; P = .0004) were associated with MBI-LCBI. Nearly 50% of all patients with a BSI developed septic shock, 10% died within 10 days of positive culture, and nearly 25% were transferred to the PICU. One-year NRM was significantly increased in patients with 1 (34%) and more than 1 (56%) BSIs in the first year post-HSCT compared with those who did not develop BSIs (14%) (P ≤ .0001). There was increased 1-year NRM in patients with at least 1 MBI-LCBI (OR, 1.94; P = .018) and at least 1 secondary BSI (OR, 2.87; P = .0023) but not CLABSIs (OR, 1.17; P = .68). Our data demonstrate that MBI-LCBIs lead to substantial use of healthcare resources and are associated with significant morbidity and mortality. Reduction in frequency of MBI-LCBI should be a major public health and scientific priority.