Multisystem Inflammatory Syndrome in Children: Two Years' Worth of Learning.

Multisystem inflammatory syndrome in children (MIS-C) is a life-threatening sequela of SARS-CoV-2 infection. Limited data are available regarding risk-stratification or long-term outcomes in MIS-C. This study sought to determine associations between serologic markers and severity of illness and understand long-term cardiac outcomes. This series includes 46 cases (mean age 8.1 years; 63.0% male) of MIS-C. Pearson's chi-squared analysis showed an erythrocyte sedimentation rate (ESR) greater than 30 mm/h and 50 mm/h were disproportionately associated with pediatric intensive care unit (PICU) admission (χ2 = 4.44, P = .04) and use of vasopressors (χ2 = 6.06, P = .01), respectively. Ferritin less than 175.6 ng/mL was associated with use of vasopressors (χ2 = 5.28, P = .02). There was a negative correlation between ESR and ejection fraction (EF) (r = -0.39, P = .009). Most patients with abnormal echocardiograms had resolution of abnormalities within 30 days. Therefore, inflammatory markers may be helpful in predicting which patients may require specific interventions or experience cardiac dysfunction, but MIS-C does not appear to be associated with complications at 1 year.

The Effects of Pulmonary Valve Replacement for Severe Pulmonary Regurgitation on Exercise Capacity and Cardiac Function.

Patients may develop hemodynamic abnormalities after right ventricular outflow tract (RVOT) repair. Re-intervention timing remains a dilemma. This study evaluates exercise capacity and RV function before and after intervention using age-related comparisons. Twenty-six patients with severe pulmonary regurgitation (PR) after initial repair scheduled for pulmonary valve replacement (PVR) were enrolled. Metabolic treadmill testing (EST) and MRI were obtained before and after surgery. EST results were compared with matched controls. Preoperative exercise time and peak oxygen consumption (VO2 max) were significantly diminished compared with controls but were not significantly different postoperatively. The patients were then split into age-related cohorts. When comparing pre-PVR and post-PVR exercise time and VO2 max among themselves, neither cohort showed significant differences. However, patients younger than 25 years had better postoperative results, an age-related difference not seen in the controls. Preoperative MRI showed significantly dilated RV, PR, and low normal function. After PVR, the right to left ventricular end-diastolic volume ratio (RVEDV:LVEDV) and pulmonary artery regurgitant fraction (RF) significantly decreased. There was no change in ventricular ejection fractions (EF). Severe PR, decreased RVEF, and RV dilation can significantly diminish exercise capacity. PVR improves RVEDV:LVEDV and RF, but not EF. Younger patients had better exercise capacity that was maintained postoperatively. This age-related difference was not seen in the controls, indicating that earlier intervention may preserve exercise capacity. Serial ESTs in patients with severe PR following RVOT repair may identify deteriorating exercise capacity as an early indicator for the need for PVR.

Gingival evaluation of the pediatric cardiac patient.

PURPOSE: Children with congenital cardiovascular diseases (CCDs) who suffer from dental diseases have an increased risk of infective endocarditis. In the light of recent evidence, oral inflammatory diseases may also increase the severity of their cardiovascular condition. The purpose of this study was to evaluate the gingival status of children with congenital cardiovascular diseases in comparison to healthy children. METHODS: Fifty 7- to 13-year-old children were included. The test group comprised 25 CCD children subdivided into three groups: (1) unrepaired ventricular septal defect; (2) aortic valve stenosis; and (3) coarctation of the aorta. The control group consisted of 25 healthy age- and gender-matched children. Gingivitis, plaque, calculus, and recession were measured on six sites per tooth on 12 teeth. RESULTS: CCD children had significantly more gingivitis (P<.001), plaque (P<.001), recession (P>.02), and calculus (P<.001) than controls. Among the CCDs groups, no statistically significant differences were found for gingivitis, plaque, or recession. CONCLUSIONS: Children with congenital cardiovascular diseases had a higher prevalence of periodontal disease, evidenced by gingivitis, plaque, calculus, and recession. These children should be evaluated periodontally and their oral health monitored on a 3-month basis to prevent disease development, benefit cardiovascular condition, prevent endocarditis, and improve quality and longevity of life.

The effects of aripiprazole on electrocardiography in children with pervasive developmental disorders.

OBJECTIVES: Psychotropic medications, including the atypical antipsychotics, have historically been scrutinized for cardiac effects and risk of sudden death. Aripiprazole is an atypical antipsychotic approved for pediatric use in schizophrenia, bipolar I disorder, and autistic disorder. Adult studies have evaluated aripiprazole's effects on electrocardiograms, but no pediatric studies have been published to date. METHODS: Electrocardiographic data were collected from children and adolescents participating in a 14-week, prospective, open-label study (n=25) of aripiprazole for irritability in pervasive developmental disorder not otherwise specified and Asperger's disorder. A 12-lead electrocardiogram was obtained at the baseline and end point visits. The electrocardiograms were evaluated for abnormal findings, and the PR, QRS, QT(c), and RR intervals were recorded. The QT interval was corrected using Bazett's, United States Food and Drug Administration (FDA) Pharmacology Division, and Fridericia's formulas. RESULTS: Twenty-four subjects received both baseline and posttreatment electrocardiograms. The mean age was 8.6 years (range 5-17 years). The average final aripiprazole dose was 7.8 mg/day (range 2.5-15 mg/day). There were no significant differences noted with the PR, QRS, RR, and QT(c) intervals after aripiprazole therapy. Also, there was no significant correlation between the dose given and the percent change in the QT(c). No post-treatment QT(c) exceeded 440 ms. CONCLUSIONS: To our knowledge, this is the first systematic evaluation of the cardiac effects of aripiprazole in children and adolescents. The results are consistent with previously published literature in adults that aripiprazole has no significant cardiac effects and can be deemed a low risk for causing sudden death. It will be important to confirm these findings in a randomized controlled trial.

Comparison between transthoracic echocardiography and cardiac magnetic resonance imaging in patients status post atrial switch procedure.

OBJECTIVES: This study compares image quality, cost, right ventricular ejection fraction analysis, and baffle visualization between transthoracic echocardiography and cardiac magnetic resonance imaging in those status post atrial switch for transposition of the great arteries. BACKGROUND: This population requires imaging for serial evaluations. Transthoracic echocardiography is often first line but has drawbacks, many of which are addressed by cardiac magnetic resonance imaging. METHODS: Twelve patients (mean age 25 years) with relatively concurrent (mean 157 days) studies were included. Three separate echocardiography and magnetic resonance imaging physicians independently analyzed baffles, image quality, and right ventricular ejection fractions. Institutional and Medicaid charges were compared. RESULTS: For right ventricular ejection fraction, echocardiography (36.1%) underestimated cardiac magnetic resonance imaging (47.8%, P = .002). Image quality for transthoracic echocardiography was significantly rated lower than cardiac magnetic resonance imaging (P = .002). Baffles were better seen in cardiac magnetic resonance imaging (transthoracic echocardiography vs. cardiac magnetic resonance imaging: superior vena cava 86% vs. 100% [P = .063]; inferior vena cava 33% vs. 97% [P = .002]; pulmonary vein 92% vs. 100% [P = .250]). Comparing hospital charges and Medicaid reimbursement, transthoracic echocardiography respectively costs 18% and 38% less than cardiac magnetic resonance imaging. CONCLUSIONS: In conclusion, transthoracic echocardiography underestimated right ventricular ejection fraction compared to cardiac magnetic resonance imaging. Cardiac magnetic resonance imaging had consistently higher image quality and better visualization of the baffles. Cost differences are minimal. We propose that cardiac magnetic resonance imaging be considered first line for imaging in certain patients' status post atrial switch procedure.

Carbohydrate recognition by Clostridium difficile toxin A.

Clostridium difficile TcdA is a large toxin that binds carbohydrates on intestinal epithelial cells. A 2-A resolution cocrystal structure reveals two molecules of alpha-Gal-(1,3)-beta-Gal-(1,4)-beta-GlcNAcO(CH(2))(8)CO(2)CH(3) binding in an extended conformation to TcdA. Residues forming key contacts with the trisaccharides are conserved in all seven putative binding sites in TcdA, suggesting a mode of multivalent binding that may be exploited for the rational design of novel therapeutics.

Crystal structure of receptor-binding C-terminal repeats from Clostridium difficile toxin A.

Clostridium difficile is a major nosocomial pathogen that produces two large protein toxins [toxin A (TcdA) and toxin B (TcdB)] capable of disrupting intestinal epithelial cells. Both belong to the family of large clostridial cytotoxins, which are characterized by the presence of a repetitive C-terminal repetitive domain (CRD). In TcdA, the CRD is composed of 39 repeats that are responsible for binding to cell surface carbohydrates. To understand the molecular structural basis of cell binding by the toxins from C. difficile, we have determined a 1.85-A resolution crystal structure of a 127-aa fragment from the C terminus of the toxin A CRD. This structure reveals a beta-solenoid fold containing five repeats, with each repeat consisting of a beta-hairpin followed by a loop of 7-10 residues in short repeats (SRs) or 18 residues in long repeats (LRs). Adjacent pairs of beta-hairpins are related to each other by either 90 degree or 120 degree screw-axis rotational relationships, depending on the nature of the amino acids at key positions in adjacent beta-hairpins. Models of the complete CRDs of toxins A and B suggest that each CRD contains straight stretches of beta-solenoid composed of three to five SRs that are punctuated by kinks introduced by the presence of a single LR. These structural features provide a framework for understanding how large clostridial cytotoxins bind to cell surfaces and suggest approaches for developing novel treatments for C. difficile-associated diseases by blocking the binding of toxins to cell surfaces.

Ligand-assisted aggregation of proteins. Dimerization of serum amyloid P component by bivalent ligands.

A comprehensive series of solution and crystallographic studies reveal how simple, achiral, bivalent ligands of the cyclic pyruvate of glycerol promote face-to-face complex formation of the pentraxin, serum amyloid P component (SAP) into decamers. SAP, a protein of the human innate immune system, is universally present in amyloids, including cerebral amyloid deposits found in the brain of Alzheimer disease patients. Removal of SAP through a specific aggregation mechanism mediated by multivalent ligands appears to provide therapeutic benefit in the progression of this disease. Crystallographic studies reveal that in our novel series of ligands only the methyl and carboxylate moieties of the pyruvate ketal directly interact with the protein, but the geometric constraints imposed by the tether dictate which of two chair conformations are adopted by the pyruvate dioxane ring. Solution studies, as interpreted through a simple thermodynamic model, account for the distribution of pentameric and decameric bound states at different ligand concentrations and indicate that differences in the flexibility of the tether determine the geometry and stability of the specific aggregates formed between SAP and two different bivalent ligands. The factors affecting the design of ligands promoting face-to-face protein dimerization as well as potential biological implications are discussed.

Estimating the potential refolding yield of recombinant proteins expressed as inclusion bodies.

Recombinant protein production in bacteria is efficient except that insoluble inclusion bodies form when some gene sequences are expressed. Such proteins must undergo renaturation, which is an inefficient process due to protein aggregation on dilution from concentrated denaturant. In this study, the protein-protein interactions of eight distinct inclusion-body proteins are quantified, in different solution conditions, by measurement of protein second virial coefficients (SVCs). Protein solubility is shown to decrease as the SVC is reduced (i.e., as protein interactions become more attractive). Plots of SVC versus denaturant concentration demonstrate two clear groupings of proteins: a more aggregative group and a group having higher SVC and better solubility. A correlation of the measured SVC with protein molecular weight and hydropathicity, that is able to predict which group each of the eight proteins falls into, is presented. The inclusion of additives known to inhibit aggregation during renaturation improves solubility and increases the SVC of both protein groups. Furthermore, an estimate of maximum refolding yield (or solubility) using high-performance liquid chromatography was obtained for each protein tested, under different environmental conditions, enabling a relationship between "yield" and SVC to be demonstrated. Combined, the results enable an approximate estimation of the maximum refolding yield that is attainable for each of the eight proteins examined, under a selected chemical environment. Although the correlations must be tested with a far larger set of protein sequences, this work represents a significant move beyond empirical approaches for optimizing renaturation conditions. The approach moves toward the ideal of predicting maximum refolding yield using simple bioinformatic metrics that can be estimated from the gene sequence. Such a capability could potentially "screen," in silico, those sequences suitable for expression in bacteria from those that must be expressed in more complex hosts.

The influence of molecular variation on protein interactions.

We investigated the influence of solvation forces on protein-protein interactions for two forms of lysozyme: hen egg white (HEWL) and turkey egg white (TEWL). Turkey egg white has more surface exposed hydrophobic residues than HEWL and the protein-protein interactions of TEWL are shown to be more attractive than those of HEWL, for the conditions studied. The importance of including a solvation term in the potential of mean force model, to account for molecular variation in protein surface characteristics, is highlighted. We also show that the magnitude of this solvation term can be estimated using readily available data.

The likelihood of aggregation during protein renaturation can be assessed using the second virial coefficient.

Protein aggregation is commonly observed during protein refolding. To better understand this phenomenon, the intermolecular interactions experienced by a protein during unfolding and refolding are inferred from second virial coefficient (SVC) measurements. It is accepted that a negative SVC is indicative of protein-protein interactions that are attractive, whereas a positive SVC indicates net repulsive interactions. Lysozyme denatured and reduced in guanidinium hydrochloride exhibited a decreasing SVC as the denaturant was diluted, and the SVC approached zero at approximately 3 M GdnHCl. Further dilution of denaturant to renaturation conditions (1.25 M GdnHCl) led to a negative SVC, and significant protein aggregation was observed. The inclusion of 500 mM L-arginine in the renaturation buffer shifted the SVC to positive and suppressed aggregation, thereby increasing refolding yield. The formation of mixed disulfides in the denatured state prior to refolding also increased protein solubility and suppressed aggregation, even without the use of L-arginine. Again, the suppression of aggregation was shown to be caused by a shift from attractive to repulsive intermolecular interactions as reflected in a shift from a negative to a positive SVC value. To the best of our knowledge, this is the first time that SVC data have been reported for renaturation studies. We believe this technique will aid in our understanding of how certain conditions promote renaturation and increase protein solubility, thereby suppressing aggregation. SVC measurements provide a useful link, for protein folding and aggregation, between empirical observation and thermodynamics.

Alpha(1)-adrenoceptor stimulation directly induces growth of vascular wall in vivo.

Previous studies suggesting that norepinephrine is directly trophic for the vascular wall have been confounded by concomitant hemodynamic disturbances. Herein, a microcatheter connected to an osmotic minipump was implanted adjacent to the rat carotid for 2-wk perivascular suffusion of agents at systemic levels ~1,000 times below the threshold for altering arterial pressure. Norepinephrine decreased lumen and adventitial areas and circumference by 10, 14, and 5%, respectively (all P < 0.05); a nonsubtype-specific alpha(1)-adrenoceptor (AR) antagonist had no effect. When begun at the time of balloon injury, 2-wk norepinephrine increased lumen loss by 45%, increased neointimal area by 64% and collagen content by 33%, and reduced vessel circumference by 5% (all P < 0.05). alpha(1)-AR antagonists decreased neointimal area by 33% (all P < 0.05). alpha(1)A-AR antagonist reduced lumen loss by 70%, neointimal area by 54%, circumference decline by 84%, and adventitial thickening by 87% (all P < 0.05), whereas alpha(1B)-, alpha(1D)-, alpha(2)- and beta-AR antagonists were without effect. These are the first in vivo studies demonstrating that norepinephrine is directly trophic for the vascular wall and augments injury-induced intimal lesion growth.