Universal open MHC-I molecules for rapid peptide loading and enhanced complex stability across HLA allotypes.

The polymorphic nature and intrinsic instability of class I major histocompatibility complex (MHC-I) and MHC-like molecules loaded with suboptimal peptides, metabolites, or glycolipids presents a fundamental challenge for identifying disease-relevant antigens and antigen-specific T cell receptors (TCRs), hindering the development of autologous therapeutics. Here, we leverage the positive allosteric coupling between the peptide and light chain (ß2 microglobulin, ß2m) subunits for binding to the MHC-I heavy chain (HC) through an engineered disulfide bond bridging conserved epitopes across the HC/ß2m interface, to generate conformationally stable, peptide-receptive molecules named "open MHC-I." Biophysical characterization shows that open MHC-I molecules are properly folded protein complexes of enhanced thermal stability compared to the wild type when loaded with low- to moderate-affinity peptides. Using solution NMR, we characterize the effects of the disulfide bond on the conformation and dynamics of the MHC-I structure, ranging from local changes in ß2m-interacting sites of the peptide-binding groove to long-range effects on the α2-1 helix and α3 domain. The interchain disulfide bond stabilizes MHC-I molecules in an open conformation to promote peptide exchange across multiple human leukocyte antigen (HLA) allotypes, covering representatives from five HLA-A supertypes, six HLA-B supertypes, and oligomorphic HLA-Ib molecules. Our structure-guided design, combined with conditional ß-peptide ligands, provides a universal platform to generate ready-to-load MHC-I systems of enhanced stability, enabling a range of approaches to screen antigenic epitope libraries and probe polyclonal TCR repertoires covering highly polymorphic HLA-I allotypes, as well as oligomorphic nonclassical molecules.

Optical control of cell-surface and endomembrane-exclusive ß-adrenergic receptor signaling.

Beta-adrenergic receptors (ßARs) are G protein-coupled receptors (GPCRs) that mediate catecholamine hormone-induced stress responses, such as elevation of heart rate. Besides those that are plasma membrane-bound, endomembrane ßARs are also signaling competent. Dysregulation of ßAR pathways underlies severe pathological conditions. Emerging evidence indicates pathological molecular signatures in deeper endomembrane ßARs signaling, likely contributing to conditions such as cardiomyocyte hypertrophy and apoptosis. However, the lack of approaches to control endomembrane ß1ARs has impeded linking signaling with pathology. Informed by the ß1AR-catecholamine interactions, we engineered an efficient photolabile proligand (OptoIso) to trigger ßAR signaling exclusively in endomembrane regions using blue light stimulation. Not only does OptoIso undergo blue light deprotection in seconds, but also efficiently enters cells and allows examination of G protein heterotrimer activation exclusively at endomembranes. OptoIso also allows optical activation of plasma membrane ßAR signaling in selected single cells with native fidelity, which can be reversed by terminating blue light. Thus, OptoIso will be a valuable experimental tool to elicit spatial and temporal control of ßAR signaling in user-defined endomembrane or plasma membrane regions in unmodified cells with native fidelity.

A Chicken Tapasin ortholog can chaperone empty HLA-B∗37:01 molecules independent of other peptide-loading components.

Human Tapasin (hTapasin) is the main chaperone of MHC-I molecules, enabling peptide loading and antigen repertoire optimization across HLA allotypes. However, it is restricted to the endoplasmic reticulum (ER) lumen as part of the protein loading complex (PLC), and therefore is highly unstable when expressed in recombinant form. Additional stabilizing co-factors such as ERp57 are required to catalyze peptide exchange in vitro, limiting uses for the generation of pMHC-I molecules of desired antigen specificities. Here, we show that the chicken Tapasin (chTapasin) ortholog can be expressed recombinantly at high yields in a stable form, independent of co-chaperones. chTapasin can bind the human HLA-B∗37:01 with low micromolar-range affinity to form a stable tertiary complex. Biophysical characterization by methyl-based NMR methods reveals that chTapasin recognizes a conserved ß2m epitope on HLA-B∗37:01, consistent with previously solved X-ray structures of hTapasin. Finally, we provide evidence that the B∗37:01/chTapasin complex is peptide-receptive and can be dissociated upon binding of high-affinity peptides. Our results highlight the use of chTapasin as a stable scaffold for protein engineering applications aiming to expand the ligand exchange function on human MHC-I and MHC-like molecules.

Impact of extrinsic incubation temperature on natural selection during Zika virus infection of Aedes aegypti and Aedes albopictus.

Arthropod-borne viruses (arboviruses) require replication across a wide range of temperatures to perpetuate. While vertebrate hosts tend to maintain temperatures of approximately 37°C-40°C, arthropods are subject to ambient temperatures which can have a daily fluctuation of > 10°C. Temperatures impact vector competence, extrinsic incubation period, and mosquito survival unimodally, with optimal conditions occurring at some intermediate temperature. In addition, the mean and range of daily temperature fluctuations influence arbovirus perpetuation and vector competence. The impact of temperature on arbovirus genetic diversity during systemic mosquito infection, however, is poorly understood. Therefore, we determined how constant extrinsic incubation temperatures of 25°C, 28°C, 32°C, and 35°C control Zika virus (ZIKV) vector competence and population dynamics within Aedes aegypti and Aedes albopictus mosquitoes. We also examined fluctuating temperatures which better mimic field conditions in the tropics. We found that vector competence varied in a unimodal manner for constant temperatures peaking between 28°C and 32°C for both Aedes species. Transmission peaked at 10 days post-infection for Aedes aegypti and 14 days for Aedes albopictus. Conversely, fluctuating temperature decreased vector competence. Using RNA-seq to characterize ZIKV population structure, we identified that temperature alters the selective environment in unexpected ways. During mosquito infection, constant temperatures more often elicited positive selection whereas fluctuating temperatures led to strong purifying selection in both Aedes species. These findings demonstrate that temperature has multiple impacts on ZIKV biology, including major effects on the selective environment within mosquitoes.

Combining iminium and supramolecular catalysis for the [4 + 2] cycloaddition of E-cinnamaldehydes.

Herein we describe a method for combining supramolecular catalysis with imininum-based organocatalysis in the Diels-Alder cycloaddition reaction. Both supramolecular host and L-proline are required for the reaction to occur, implying that encapsulation of the substrates and co-catalyst are necessary for the reaction to occur. We explore the substrate scope for a variety of E-cinnamaldehydes and dienes. Finally, we probe the supramolecular assembly processes responsible for the observed catalysis using NMR spectroscopic methods.

Palladium-Catalyzed γ,γ'-Diarylation of Free Alkenyl Amines.

The direct difunctionalization of alkenes is an effective way to construct multiple C-C bonds in one-pot using a single functional group. The regioselective dicarbofunctionalization of alkenes is therefore an important area of research to rapidly obtain complex organic molecules. Herein, we report a palladium-catalyzed γ,γ'-diarylation of free alkenyl amines through interrupted chain walking for the synthesis of Z-selective alkenyl amines. Notably, while 1,3-dicarbofunctionalization of allyl groups is well precedented, the present disclosure allows 1,3-dicarbofunctionalization of highly substituted allylamines to give highly Z-selective trisubsubstituted olefin products. This cascade reaction operates via an unprotected amine-directed Mizoroki-Heck (MH) pathway featuring a ß-hydride elimination to selectively chain walk to furnish a new terminal olefin which then generates the cis-selective alkenyl amines around the sterically crowded allyl moiety. This operationally simple protocol is applicable to a variety of cyclic, branched, and linear secondary and tertiary alkenylamines, and has a broad substrate scope with regard to the arene coupling partner as well. Mechanistic studies have been performed to help elucidate the mechanism, including the presence of a likely unproductive side C-H activation pathway.

One-Pot C-H Arylation/Lactamization Cascade Reaction of Free Benzylamines.

An efficient method has been developed for the synthesis of seven-membered biaryl lactams involving Pd-catalyzed, native amine-directed, ortho-arylation of benzylamines followed by in situ lactamization. This cascade sequence is enabled by the use of 2-iodobenzoates, which facilitates C-H arylation from the free amine under conditions that typically require an improved directing group approach. This reaction is characterized by a broad substrate scope with good functional group tolerance. The need for an ester versus carboxylic acid-functionalized coupling partner is also explored, as is the potential for synthesizing eight-membered biaryl lactams. Various applications are also investigated, including access to the aza-brassinolide core.

Carbon Dioxide-Mediated C( sp2)-H Arylation of Primary and Secondary Benzylamines.

C-C bond formation by transition metal-catalyzed C-H activation has become an important strategy to fabricate new bonds in a rapid fashion. Despite the pharmacological importance of ortho-arylbenzylamines, however, effective ortho-C-C bond formation of free primary and secondary benzylamines using PdII remains an outstanding challenge. Presented herein is a new strategy for constructing ortho-arylated primary and secondary benzylamines mediated by carbon dioxide (CO2). The use of CO2 with Pd is critical to allowing this transformation to proceed under relatively mild conditions, and mechanistic studies indicate that it (CO2) is directly involved in the rate-determining step. Furthermore, the milder temperatures furnish free amine products that can be directly used or elaborated without the need for deprotection. In cases where diarylation is possible, an interesting chelate effect is shown to facilitate selective monoarylation.

Endosidin2 targets conserved exocyst complex subunit EXO70 to inhibit exocytosis.

The exocyst complex regulates the last steps of exocytosis, which is essential to organisms across kingdoms. In humans, its dysfunction is correlated with several significant diseases, such as diabetes and cancer progression. Investigation of the dynamic regulation of the evolutionarily conserved exocyst-related processes using mutants in genetically tractable organisms such as Arabidopsis thaliana is limited by the lethality or the severity of phenotypes. We discovered that the small molecule Endosidin2 (ES2) binds to the EXO70 (exocyst component of 70 kDa) subunit of the exocyst complex, resulting in inhibition of exocytosis and endosomal recycling in both plant and human cells and enhancement of plant vacuolar trafficking. An EXO70 protein with a C-terminal truncation results in dominant ES2 resistance, uncovering possible distinct regulatory roles for the N terminus of the protein. This study not only provides a valuable tool in studying exocytosis regulation but also offers a potentially new target for drugs aimed at addressing human disease.

Carbon Dioxide-Mediated C(sp3)-H Arylation of Amine Substrates.

Elaborating amines via C-H functionalization has been an important area of research over the past decade but has generally relied on an added directing group or sterically hindered amine approach. Since free-amine-directed C(sp3)-H activation is still primarily limited to cyclization reactions and to improve the sustainability and reaction scope of amine-based C-H activation, we present a strategy using CO2 in the form of dry ice that facilitates intermolecular C-H arylation. This methodology has been used to enable an operationally simple procedure whereby 1° and 2° aliphatic amines can be arylated selectively at their γ-C-H positions. In addition to potentially serving as a directing group, CO2 has also been demonstrated to curtail the oxidation of sensitive amine substrates.

Impact of school peanut-free policies on epinephrine administration.

BACKGROUND: Children with food allergies spend a large proportion of time in school but characteristics of allergic reactions in schools are not well studied. Some schools self-designate as peanut-free or have peanut-free areas, but the impact of policies on clinical outcomes has not been evaluated. OBJECTIVE: We sought to determine the effect of peanut-free policies on rates of epinephrine administration for allergic reactions in Massachusetts public schools. METHODS: In this retrospective study, we analyzed (1) rates of epinephrine administration in all Massachusetts public schools and (2) Massachusetts public school nurse survey reports of school peanut-free policies from 2006 to 2011 and whether schools self-designated as "peanut-free" based on policies. Rates of epinephrine administration were compared for schools with or without peanut-restrictive policies. RESULTS: The percentage of schools with peanut-restrictive policies did not change significantly in the study time frame. There was variability in policies used by schools self-designated as peanut-free. No policy was associated with complete absence of allergic reactions. Both self-designated peanut-free schools and schools banning peanuts from being served in school or brought from home reported allergic reactions to nuts. Policies restricting peanuts from home, served in schools, or having peanut-free classrooms did not affect epinephrine administration rates. Schools with peanut-free tables, compared to without, had lower rates of epinephrine administration (incidence rate per 10,000 students 0.2 and 0.6, respectively, P = .009). CONCLUSIONS: These data provide a basis for evidence-based school policies for children with food allergies. Further studies are required before decisions can be made regarding peanut-free policies in schools.

Catalytic Coupling between Unactivated Aliphatic C-H Bonds and Alkynes via a Metal-Hydride Pathway.

We report a Rh(I)-catalyzed site-selective coupling between ketone ß-C(sp3)-H bonds and aliphatic alkynes using an in situ-installed directing group. Upon hydrogenation or hydration, various ß-alkylation or ß-aldol products of the ketones are obtained with broad functional group tolerance. Mechanistic investigations support the involvement of a Rh-H intermediate through oxidative addition of Rh(I) into the ß-C-H bonds. Thus, to the best of our knowledge, this transformation represents the first example of catalytic couplings between unsaturated hydrocarbons and unactivated aliphatic C-H bonds via a metal-hydride pathway.

Transition metal-catalyzed ketone-directed or mediated C-H functionalization.

Transition metal-catalyzed C-H functionalization has evolved into a prominent and indispensable tool in organic synthesis. While nitrogen, phosphorus and sulfur-based functional groups (FGs) are widely employed as effective directing groups (DGs) to control the site-selectivity of C-H activation, the use of common FGs (e.g. ketone, alcohol and amine) as DGs has been continuously pursued. Ketones are an especially attractive choice of DGs and substrates due to their prevalence in various molecules and versatile reactivity as synthetic intermediates. Over the last two decades, transition metal-catalyzed C-H functionalization that is directed or mediated by ketones has experienced vigorous growth. This review summarizes these advancements into three major categories: use of ketone carbonyls as DGs, direct ß-functionalization, and α-alkylation/alkenylation with unactivated olefins and alkynes. Each of these subsections is discussed from the perspective of strategic design and reaction discovery.

Catalytic C(sp(3) )-H Arylation of Free Primary Amines with an exo Directing Group Generated In†Situ.

Herein, we report the palladium-catalyzed direct arylation of unactivated aliphatic C-H bonds in free primary amines. This method takes advantage of an exo-imine-type directing group (DG) that can be generated and removed in situ. A range of unprotected aliphatic amines are suitable substrates, undergoing site-selective arylation at the γ-position. Methyl as well as cyclic and acyclic methylene groups can be activated. Furthermore, when aniline-derived substrates were used, preliminary success with δ-C-H arylation was achieved. The feasibility of using the DG component in a catalytic fashion was also demonstrated.

Taking the leap earlier: the timing of tolerance.

PURPOSE OF REVIEW: The paradigm for the primary prevention of peanut allergy was, until recently, strict avoidance of peanut during pregnancy, infancy, and early childhood. However, in countries that had these dietary guidelines, the prevalence of peanut allergy greatly increased in contrast to low prevalence rates of peanut allergy in countries where infant diets included peanut at an early age, suggesting the hypothesis that early introduction of peanut is superior to delayed introduction of peanut as a strategy for the primary prevention of food allergy. This review examines recent high-quality studies that support this hypothesis. RECENT FINDINGS: Publication of the Learning Early about Allergy to Peanut interventional trial showed that 17% of children avoiding peanut until 5 years of age developed peanut allergy compared with 3% of children who started eating peanut at ages of 4-11 months. Two birth cohort studies demonstrated that high maternal consumption of peanut during the pregnancy period reduced the risk of peanut allergy in offspring by 50-75%. SUMMARY: Recent studies indicate that early introduction of peanut enhances the development of tolerance to peanut, reducing the risk of childhood peanut allergy.

Dexmedetomidine as a Rapid Bolus for Treatment and Prophylactic Prevention of Emergence Agitation in Anesthetized Children.

BACKGROUND: Administration of dexmedetomidine (DEX) in the pediatric population for its sedative, analgesic, and anxiolytic properties has been widely reported, despite there being no label indication approved by the U.S. Food and Drug Administration for pediatric patients. Infusions of DEX, rather than bolus administration, are recommended to attenuate the hemodynamic response caused by the α2-adrenoreceptor agonist. In this prospective, double-blind, randomized study, we examined the effect of rapid IV bolus injection of DEX on emergence agitation and the hemodynamic response in a large sample of children undergoing tonsillectomy with or without adenoidectomy, with or without myringotomy, and/or tympanostomy tube insertion. METHODS: Four hundred patients, aged 4 to 10 years, undergoing tonsillectomy with or without adenoidectomy, with or without myringotomy, and/or tympanostomy tube insertion, were randomized at a 1:1 ratio into 1 of the 2 treatment groups in a double-blinded fashion. After a standardized anesthetic regimen and approximately 5 minutes before the end of surgery, patients in group DEX were administered a rapid IV bolus of 4 µg·mL DEX at a dose of 0.5 µg·kg, whereas patients in group saline received a rapid IV bolus of equivalent volume saline. Baseline measurements of heart rate, systolic blood pressure, diastolic blood pressure, respiratory rate, and blood oxygen saturation were collected immediately before study drug administration and every minute thereafter for 5 minutes. In the postanesthesia care unit, vital signs were measured, emergence agitation (EA) was assessed using the Pediatric Anesthesia Emergence Delirium scale, and postoperative opioid use and complications were recorded. RESULTS: The incidence of EA in group DEX was significantly lower than that in group saline, regardless of whether EA was defined as a Pediatric Anesthesia Emergence Delirium score >10 (36% vs 66%, respectively; P < 0.0001; relative risk [95% confidence interval] = 0.527 [0.421-0.660]; number needed to treat = 3.33) or >12 (30% vs 61%, respectively; P < 0.0001; relative risk [95% confidence interval] = 0.560 [0.458-0.684]; number needed to treat = 3.23). Both groups exhibited similar baseline vital signs before study drug injection (all P ≥ 0.602). After injection, group DEX experienced a significant decrease in heart rate for all time points in comparison with group saline (all P < 0.0001). A significant, biphasic blood pressure response was observed in group DEX, specifically, a transient increase in systolic blood pressure at 1 minute after injection (P < 0.0001) and a subsequent decrease below baseline for 3, 4, and 5 minutes (all P < 0.0001). No patients required treatment for bradycardia, hypertension, or hypotension. A significantly smaller percentage of patients in group DEX received postoperative, supplemental opioid medication compared with group saline (48% vs 73%, respectively; P < 0.0001). Group DEX appeared to experience fewer adverse events than group saline as well (9% vs 17%, respectively; P = 0.025). CONCLUSIONS: Rapid IV bolus administration of DEX in children improved their recovery profile by reducing the incidence of EA. A statistically significant change in hemodynamics was observed, but no patients required any intervention for hemodynamic changes. Furthermore, DEX reduced the incidence of postoperative opioid administration, and a trend of fewer adverse events was observed in group DEX.

Narcissistic self-sorting in self-assembled cages of rare Earth metals and rigid ligands.

Highly selective, narcissistic self-sorting can be achieved in the formation of self-assembled cages of rare earth metals with multianionic salicylhydrazone ligands. The assembly process is highly sensitive to the length of the ligand and the coordination geometry. Most surprisingly, high-fidelity sorting is possible between ligands of identical coordination angle and geometry, differing only in a single functional group on the ligand core, which is not involved in the coordination. Supramolecular effects allow discrimination between pendant functions as similar as carbonyl or methylene groups in a complex assembly process.

International survey of knowledge of food-induced anaphylaxis.

BACKGROUND: Studies show that anaphylaxis is under-recognized and epinephrine (adrenaline) is under-used by medical personnel as well as patients and their families. This study assesses the knowledge of food-induced anaphylaxis diagnosis and management across different populations of providers and caregivers and other interested respondents. METHODS: An online survey embedded in a case discussion of food-induced anaphylaxis was distributed by Medscape to registered members. RESULTS: A total of 7822 responders who started the activity chose to answer at least some of the questions presented (response rate 39.5%). Over 80% of responders in all groups correctly identified the case of anaphylaxis with prominent skin and respiratory symptoms; however, only 55% correctly recognized the case without skin symptoms as anaphylaxis. Only 23% of responders correctly selected risk factors for anaphylaxis, with physicians significantly more likely to choose the correct answers as compared to allied health, other health professionals, and medical students (p < 0.001). Ninety-five percent selected epinephrine (adrenaline) as the most appropriate treatment for anaphylaxis, and 81% correctly indicated that there are no absolute contraindications for epinephrine (adrenaline) in the setting of anaphylaxis. When presented a case of a child with no documented history of allergies who has symptoms of anaphylaxis, more physicians than any other group chose to administer stock epinephrine (adrenaline) (73% vs. 60%, p < 0.001). CONCLUSION: Specific knowledge deficits for food-induced anaphylaxis persist across all groups. Further educational efforts should be aimed not only at the medical community but also for the entire caregiver community and general public, to optimize care for food allergic individuals.

Anesthetic drugs and onset of malignant hyperthermia.

BACKGROUND: The time between the beginning of anesthetic administration and recognition of the first sign of malignant hyperthermia (MH) (MH onset time) could differ among anesthetic drugs. METHODS: We examined the time of the first signs of suspected MH, anesthetic drugs administered, subject age, and year of event in Adverse Metabolic/Musculoskeletal Reaction to Anesthesia reports in the North American Malignant Hyperthermia Registry. Inclusion criteria were judgment by the reporting clinician that the event was possible or fulminant MH, documentation of the time when anesthetic administration began, and the time when the first MH sign was noted. Descriptive statistics, Kruskal-Wallis analysis, and nonparametric correlation were used to assess the difference in MH onset times under different conditions. RESULTS: Four hundred seventy-seven cases met inclusion criteria; 58.5% were possible MH and 41.5% fulminant MH. Inhaled anesthetic and succinylcholine were given in 53.9% of cases, inhaled anesthetic only in 41.7%, and succinylcholine without inhaled anesthetics in 2.9%. No causative anesthetic drugs were reported in 7 MH cases. In 394 patients exposed to only 1 of the 4 inhaled anesthetics, without regard for subject age, MH onset time was shorter in the presence of halothane than any of the other anesthetics and shorter after succinylcholine in all anesthetics. If succinylcholine was not given, MH onset was shorter during sevoflurane anesthesia than during desflurane or isoflurane. In 322 cases, 1 rather than multiple first signs of MH were reported with masseter spasm as the earliest MH sign. In 339 cases in which masseter spasm was not reported, there was no difference in MH onset time with or without succinylcholine. In 146 cases in which masseter spasm was not reported and succinylcholine was not given, MH onset was shorter during halothane anesthesia, than during exposure to desflurane, or isoflurane. MH onset time during sevoflurane was shorter than during desflurane or isoflurane. MH was reported later in the course of anesthesia after 1998, when halothane and succinylcholine were less often reported. MH occurred after succinylcholine administration in the absence of inhaled anesthetics. We could not separate an effect of age from that of other variables. CONCLUSION: The onset of MH has been observed later during desflurane and isoflurane anesthesia than during exposure to sevoflurane. Since 1998, MH signs have more often appeared later, in the second or third hour of anesthesia, than they did before 1998.