Atopic manifestations of inborn errors of immunity.

PURPOSE OF REVIEW: Allergy and atopic features are now well recognized manifestations of many inborn errors of immunity (IEI), and indeed may be the hallmark in some, such as DOCK8 deficiency. In this review, we describe the current IEI associated with atopy, using a comprehensive literature search and updates from the IUIS highlighting clinical clues for underlying IEI such as very early onset of atopic disease or treatment resistance to enable early and accurate genetic diagnosis. RECENT FINDINGS: We focus on recently described genes, their categories of pathogenic mechanisms and the expanding range of potential therapies. SUMMARY: We highlight in this review that patients with very early onset or treatment resistant atopic disorders should be investigated for an IEI, as targeted and effective therapies exist. Early and accurate genetic diagnosis is crucial in this cohort to reduce the burden of disease and mortality.

Phase 2 Trial of Rituximab in Acetylcholine Receptor Antibody-Positive Generalized Myasthenia Gravis: The BeatMG Study.

OBJECTIVE: To determine whether rituximab is safe and potentially beneficial, warranting further investigation in an efficacy trial for acetylcholine receptor antibody-positive generalized MG (AChR-Ab+ gMG). METHODS: The B-Cell Targeted Treatment in MG (BeatMG) study was a randomized, double-blind, placebo-controlled, multicenter phase-2 trial that utilized a futility design. Individuals 21-90 years of age, with AChR-Ab+ gMG (MG Foundation of America Class II-IV) and receiving prednisone ≥15 mg/day were eligible. The primary outcome was a measure of steroid-sparing effect, defined as the proportion achieving ≥75% reduction in mean daily prednisone dose in the 4-weeks prior to week 52 and with clinical improvement or no significant worsening as compared to the 4-week period prior to randomization. The co-primary outcome was safety. Secondary outcomes included MG-specific clinical assessments. Fifty-two individuals were randomized (1:1) to either a two-cycle rituximab/placebo regimen, with follow-up through 52-weeks. RESULTS: Of the 52 participants included, mean (±SD) age at enrollment was 55.1 (±17.1) years; 23 (44.2%) were female, and 31 (59.6%) were MGFA Class II. The mean (±SD) baseline prednisone dose was 22.1 (±9.7) mg/day. The primary steroid-sparing outcome was achieved in 60% of those on rituximab vs. 56% on placebo. The study reached its futility endpoint (p=0.03) suggesting that the pre-defined clinically meaningful improvement of 30% due to rituximab over placebo was unlikely to be achieved in a subsequent, larger trial. No safety issues identified. CONCLUSIONS: While rituximab was safe and well-tolerated, these results suggest that there is a low probability of observing the defined clinically meaningful steroid-sparing effect over a 12-month period in a phase-3 trial of mild-moderately symptomatic AChR-Ab+ gMG. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that for mild-to-moderate AChR-Ab+ gMG, compared with placebo, rituximab is safe but unlikely to reduce steroid use by an absolute difference of at least 30% at 1 year. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02110706.

Characterization of pepsin from rabbit gastric extract, its action on ß-casein and the effects of lipids on proteolysis.

Rabbit gastric extract (RGE) is a source of gastric enzymes for in vitro digestion studies. While its gastric lipase activity has been characterized and compared to other lipases, its pepsin activity has not been studied. We measured pepsin activity in RGE using both hemoglobin and azocoll as substrates, and identified the protein separated by SDS-PAGE as a type II-4 mature pepsin of 328 amino acid residues using Edman sequencing, LC-MS/MS analysis and intact mass measurement. As a proof-of-concept that RGE was suitable for in vitro digestion of both proteins and lipids, it was used for studying the proteolysis of ß-casein under conditions mimicking the early stages of intragastric digestion. ß-Casein was displayed either in solution or at the surface of a ß-casein-stabilized rapeseed oil emulsion to investigate the impact of lipids and lipolysis on proteolysis. Proteolysis of ß-casein was quantified based on the kinetics of ß-casein disappearance, the identification of various peptides generated upon digestion and their variation with time. The results obtained with RGE were highly similar to those obtained with equivalent amounts of porcine pepsin used as a reference standard. Digestion of ß-casein was slower when it was displayed at the oil-water interface and some degradation peptides were transiently observed at higher levels and for a longer time than with ß-casein in solution, or accumulated upon digestion. N-terminal sequencing of the main isolated peptides revealed a sequential action of pepsin starting from the hydrophobic C-terminal end of ß-casein, which was impaired by the interaction of ß-casein with lipids.

Constitutive expression of human gastric lipase in Pichia pastoris and site-directed mutagenesis of key lid-stabilizing residues.

The cDNA encoding human gastric lipase (HGL) was integrated into the genome of Pichia pastoris using the pGAPZα A transfer vector. The HGL signal peptide was replaced by the yeast α-factor to achieve an efficient secretion. Active rHGL was produced by the transformed yeast but its levels and stability were dependent on the pH. The highest activity was obtained upon buffering the culture medium at pH5, a condition that allowed preserving enzyme activity over time. A large fraction (72±2%) of secreted rHGL remained however bound to the yeast cells, and was released by washing the cell pellet with an acid glycine-HCl buffer (pH2.2). This procedure allowed establishing a first step of purification that was completed by size exclusion chromatography. N-terminal sequencing and MALDI-ToF mass spectrometry revealed that rHGL was produced in its mature form, with a global mass of 50,837±32Da corresponding to a N-glycosylated form of HGL polypeptide (43,193Da). rHGL activity was characterized as a function of pH, various substrates and in the presence of bile salts and pepsin, and was found similar to native HGL, except for slight changes in pH optima. We then studied by site-directed mutagenesis the role of three key residues (K4, E225, R229) involved in salt bridges stabilizing the lid domain that controls the access to the active site and is part of the interfacial recognition site. Their substitution has an impact on the pH-dependent activity of rHGL and its relative activities on medium and long chain triglycerides.

Relevant pH and lipase for in vitro models of gastric digestion.

The development of in vitro digestion models relies on the availability of in vivo data such as digestive enzyme levels and pH values recorded in the course of meal digestion. The variations of these parameters along the GI tract are important for designing dynamic digestion models but also static models for which the choice of representative conditions of the gastric and intestinal conditions is critical. Simulating gastric digestion with a static model and a single set of parameters is particularly challenging because the variations in pH and enzyme concentration occurring in the stomach are much broader than those occurring in the small intestine. A review of the literature on this topic reveals that most models of gastric digestion use very low pH values that are not representative of the fed conditions. This is illustrated here by showing the variations in gastric pH as a function of meal gastric emptying instead of time. This representation highlights those pH values that are the most relevant for testing meal digestion in the stomach. Gastric lipolysis is still largely ignored or is performed with microbial lipases. In vivo data on gastric lipase and lipolysis have however been collected in humans and dogs during test meals. The biochemical characterization of gastric lipase has shown that this enzyme is rather unique among lipases: (i) stability and activity in the pH range 2 to 7 with an optimum at pH 4-5.4; (ii) high tensioactivity that allows resistance to bile salts and penetration into phospholipid layers covering TAG droplets; (iii) sn-3 stereospecificity for TAG hydrolysis; and (iv) resistance to pepsin. Most of these properties have been known for more than two decades and should provide a rational basis for the replacement of gastric lipase by other lipases when gastric lipase is not available.

The structure of infant formulas impacts their lipolysis, proteolysis and disintegration during in vitro gastric digestion.

Milk lipids supply most of the calories necessary for newborn growth in maternal milk or infant formulas. The chemical composition of infant formulas has been optimized but not the structure of the emulsion. There is still a major difference between the native emulsions of milk fat globules and processed submicronic emulsions in infant formulas. This difference may modify the kinetics of digestion of emulsions in newborns and influence lipid metabolism. To check this, semi-dynamic gastric in vitro digestions were conducted on three matrices: a standardized milk emulsion containing native milk fat globules referred to as minimally-processed emulsion and two processed model infant formulas (homogenized or homogenized/pasteurized). Gastric conditions mimicked those reported in newborns. The minimally-processed emulsion was lipolyzed and proteolyzed slower than processed formulas. The difference in initial structure persisted during digestion. The surface of the droplets was the key parameter to control gastric lipolysis kinetics, the pattern of released fatty acids and proteolysis by faster hydrolysis of adsorbed proteins.

Influence of the dietary fibre levels on faecal hair excretion after 14 days in short and long-haired domestic cats.

Hairballs are a common problem in cats and may result in intestinal obstruction. Dietary fibre has been recommended to stimulate hair faecal excretion. The objective of this study was to assess the influence of psyllium and different levels of total dietary fibre (6% vs. 11% vs. 15% TdF) on hair faecal excretion in short and long-haired (LH) domestic cats. Twenty-one adult cats were divided into three panels: shedding panel, short-haired (SH) panel and LH panel. Shedding panel was used to assess shedding throughout the study with a normalized brushing. In parallel, SH panel and LH panel were used to evaluate the impact of the diets on faecal hair excretion. They were fed a low-fibre diet during phase 1 (diet 6, 6.0% TdF). In phase 2, panels were fed either diet 11 (11% TdF) or diet 15 (15% TdF). In phase 3, cats returned to diet 6 before a crossover on the other diet in phase 4. Those diets were fed to cats for 14 days. Faecal hair excretion was quantified daily. Data were analysed using a generalized linear model procedure. The assessment of shedding showed that the study did not occur during moulting season. In the LH panel, diet 11 and diet 15 increased (P < 0.001) faecal hair excretion by 81% and 113% respectively, compared to the control diet. In the SH panel, no influence of the diets was observed. This study supports that fibre affects faecal hair excretion in LH cats, suggesting that a diet with psyllium and 11% or 15% TdF might minimize hairball formation in 14 days and between shedding periods. In SH cats, 11% and 15% fibre levels had no effect on faecal hair excretion. This could be explained by the low quantity of hair ingested outside the shedding season or by the short duration of the study.

Time to diagnosis in the National Registry of Veterans with Amyotrophic Lateral Sclerosis.

Our objective was to determine the interval from symptom onset to diagnosis, and to evaluate associated factors in a cohort of U.S. Veterans with motor neuron diseases. We retrospectively evaluated 1359 patients enrolled in the National Registry of Veterans with Amyotrophic Lateral Sclerosis (ALS). The main outcome measures were time from symptom onset to first diagnosis and to second opinion. Predictor variables included age at symptom onset, year of symptom onset, race, onset site, final diagnosis, number of diagnostic tests performed and clinical sites visited. Median time to first diagnosis was 11 months; median time to second opinion was two months. In a multivariable model, more recent calendar year of symptom onset, younger age, bulbar onset and a diagnosis of ALS versus non-ALS motor neuron disease were all significantly associated with a shorter time to first diagnosis. Later year of symptom onset and white race were significantly associated with a shorter time to second opinion. While the interval from symptom onset to diagnosis, and many of the associated factors are similar between our large cohort of U.S. Veterans with ALS and other smaller published cohorts, we found that the diagnostic interval among U.S. Veterans has significantly decreased over time.

Factors associated with survival in the National Registry of Veterans with ALS.

The clinical course of patients with ALS is highly variable. While the median survival time from symptom onset is 2-4 years, there are reports of survival ranging from less than a year to more than 40 years. Such variability makes planning difficult for patients and physicians, and complicates clinical trial design. We sought to validate previous predictors of survival and search for new ones using a large group of ALS patients in the National Registry of Veterans with ALS. We were especially interested in how various aspects of military service might affect survival. Subjects were those in the National Registry of Veterans with ALS who had probable or definite ALS (according to El Escorial criteria). A multivariable Cox proportional hazard regression model was used to examine variables for statistical association with ventilator-free survival time (determined from date of first diagnosis). Subjects who had not died or started ventilation by 31 October 2006 were censored. Our group of 1085 US military veterans with ALS was primarily male (98%) and white (94%), with mostly sporadic (95%) and extremity-onset (76%) ALS. Symptom onset occurred at a mean age of 59.3 years (60.6 years for diagnosis). Median survival time from symptom onset was 4.7 years (3.3 years from diagnosis). In our multivariable model, older age at diagnosis (HR 1.41 (95% CI 1.27-1.55) per 10-year increase), non-extremity site of onset (HR 1.55 (1.24-1.94)), and past deployment to Vietnam (HR 1.73 (1.36-2.19)) were all associated with shortened survival. A longer time to diagnosis was associated with better survival (HR 0.77 (0.70-0.84) per one year increase in diagnosis time). In this unique cohort of veterans with ALS, traditional factors of reduced survival remained important. In addition, past deployment to Vietnam was found to be associated with shortened survival as well. This finding could be due to a common exposure, a shared characteristic, an unmeasured confounder, or an enrollment bias. More research will be needed to understand the reasons behind this new finding.