Attenuated asthma phenotype in mice with a fetal-like antigen receptor repertoire

We hypothesized that the scarcity of N-nucleotides might contribute to the inability of the neonate to mount a robust allergic immune response. To test this, we used terminal deoxyribunucleotidyl Transferase deficient (TdT^-/-) mice, which express "fetal-like" T cell receptor and immunoglobulin repertoires with largely germline-encoded CDR3 regions. Intraperitoneal sensitization was followed by aerosol provocation with either PBS or the allergen OVA in both TdT^-/- mice and wild-type mice to develop allergic respiratory inflammation. The effects of this procedure were investigated by lung function test, immunological analysis of serum and brochoalveolar lavage. The local T_H2 cytokine milieu was significantly attenuated in TdT^-/- mice. Within this group, the induction of total IgE levels was also significantly reduced after sensitization. TdT^-/- mice showed a tendency toward reduced eosinophilic inflow into the bronchial tubes, which was associated with the elimination of respiratory hyperreactivity. In conclusion, in a murine model of allergic airway inflammation, the expression of fetal-like antigen receptors was associated with potent indications of a reduced ability to mount an asthma phenotype. This underlines the importance of somatically-generated antigen-receptor repertoire diversity in type one allergic immune responses and suggests that the fetus may be protected from allergic responses, at least in part, by controlling N addition.

Efficacy, Safety and Pharmacokinetic Results of a Phase III, Open-Label, Multicenter Study with a Plasma-Derived Von Willebrand Factor (VWF)/Factor VIII (FVIII) Concentrate in Pediatric Patients <12 Years of Age with Hemophilia A (SWIFTLY-HA Study)

Background

Plasma-derived von Willebrand factor/factor VIII (pdVWF/FVIII; VONCENTO^®, CSL Behring) is a high-concentration, low-volume, high-purity concentrate, with a high level of VWF high-molecular-weight multimers and a VWF/FVIII ratio of ~2.4:1.

Methods

This study (NCT01229007) investigated the pharmacokinetics (PK), efficacy and safety of pdVWF/FVIII in 35 previously treated (minimum 20 exposure days [EDs]) pediatric patients (<12 years) with severe hemophilia A. PK was evaluated with a single 50 IU FVIII/kg dose of pdVWF/FVIII. Efficacy and safety analyses were performed during on-demand treatment (n=17) or prophylaxis (n=18) for up to 100 EDs with a maximum study duration of 12 months.

Results

PK profiles were similar for patients aged <6 years and those aged 6–12 years, and, as expected, the youngest patients had an increased clearance. On-demand patients reported 320 non-surgical bleeding (NSB) events and received a median number of 29.0 infusions (median dose 34.2 IU FVIII/kg). Hemostatic efficacy was assessed by the investigator as excellent/good in all cases (24%/76%). The 18 patients in the prophylaxis arm experienced 173 NSB events (97 NSBs [56%] in three patients). Five patients (28%) had no NSB events. Overall, patients received a median number of 92 infusions (median dose 30.6 IU FVIII/kg). The majority of bleeds (92%) were successfully controlled with only one infusion. Hemostatic efficacy was assessed by the investigator as excellent (86%) or good (14%). Inhibitors occurred in three patients of which two were transient (low titer) and one persisted (high titer). These three patients had known risk factors for inhibitor development.

Conclusion

This study demonstrated comparable PK profiles for pediatric patients aged <6 years and aged 6–12 years, and an excellent efficacy and safety profile in this population. The adverse events reported were mostly mild to moderate with inhibitor rates within the expected incidence range.

Different Effects of Two Protocols for Pre-Procedural Analgosedation on Vital Signs in Neonates during and after Endotracheal Intubation

BACKGROUND

Analgosedation is often used for endotracheal intubation in neonates, but no consensus exists on the optimal pre-procedural medication.

AIMS

To compare the time to intubation and vital signs during and after intubation in 2 NICUs using different premedication protocols.

METHODS

Prospective observational study in 2 tertiary NICUs, comparing fentanyl and optional vecuronium for elective neonatal endotracheal intubation (NICU-1) with atropine, morphine, midazolam and optional pancuronium (NICU-2). Primary endpoints were: time to intubate and number of intubation attempts; secondary endpoints were: deviations of heart rate, oxygen saturation and blood pressure from baseline until 20 min post intubation.

RESULTS

45 and 30 intubations were analyzed in NICU-1 and NICU-2. Time to intubation was longer in NICU-1 (7 min) than in NICU-2 (4 min; p=0.029), but the mean number of intubation attempts did not differ significantly. Bradycardias (34 vs. 1, p<0.001) and hypoxemias (136 vs. 48, p<0.001) were more frequent in NICU-1, and tachycardias (59 vs. 72, p<0.001) more frequent in NICU-2. Mean arterial blood pressure (MAP) increased in NICU-1 (+6.18 mmHg) and decreased in NICU-2 (-5.83 mmHg), whereas mean heart rates (HR) decreased in NICU-1 (-19.29 bpm) and increased in NICU-2 (+15.93 bpm). MAP and HR returned to baseline 6-10 min after intubation in NICU-1 and after 11-15 min and 16-20 min in NICU-2, respectively.

CONCLUSIONS

The two protocols yielded significant differences in the time to intubation and in the extent and duration of physiologic changes during and post-intubation. Short acting drugs should be preferred and vital signs should be closely monitored at least 20 min post intubation. More studies are required to identify analgosedation protocols that minimize potentially harmful events during endotracheal intubation.

Detection of Volatile Organic Compounds as Potential Novel Biomarkers for Chorioamnionitis - Proof of Experimental Models

Background: Histologic chorioamnionitis is only diagnosed postnatally which prevents interventions. We hypothesized that volatile organic compounds (VOCs) in the amniotic fluid might be useful biomarkers for chorioamnionitis and that VOC profiles differ between amnionitis of different origins. Methods: Time-mated ewes received intra-amniotic injections of media or saline (controls), or live Ureaplasma parvum serovar 3 (Up) 14, 7 or 3d prior to c-section at day 124 gestational age (GA). 100 μg recombinant ovine IL-1α was instilled at 7, 3 or 1d prior to delivery. Headspace VOC profiles were measured from amniotic fluids at birth using ion mobility spectrometer coupled with multi-capillary columns. Results: 127 VOC peaks were identified. 27 VOCs differed between samples from controls and Up- or IL-1α induced amnionitis. The best discrimination between amnionitis by Up vs. IL-1α was reached by 2-methylpentane, with a sensitivity/specificity of 96/95% and a positive predictive value/negative predictive values of 96 and 95%. The concentration of 2-methylpentane in VOCs peaked 7d after intra-amniotic instillation of Up. Discussion: We established a novel method to study headspace VOC profiles of amniotic fluids. VOC profiles may be a useful tool to detect and to assess the duration of amnionitis induced by Up. 2-methylpentane was previously described in the exhalate of women with pre-eclampsia and might be a volatile biomarker for amnionitis. Amniotic fluids analyzed by ion mobility spectrometry coupled with multi-capillary columns may provide bedside diagnosis of amnionitis and understanding inflammatory mechanisms during pregnancy.

An Open-Label Extension Study to Assess the Long-Term Efficacy and Safety of a Plasma-Derived von Willebrand Factor (VWF)/Factor VIII (FVIII) Concentrate in Patients with von Willebrand Disease (SWIFT-VWDext Study)

Objective

Plasma-derived von Willebrand factor/factor VIII (pdVWF/FVIII; VONCENTO^®, CSL Behring) is a high-concentration, low-volume, high-purity concentrate, which contains a high level of high-molecular-weight multimers and a VWF/FVIII ratio of ~2.4:1. The SWIFT ("Studies with von Willebrand factor/Factor VIII") program is evaluating pdVWF/FVIII in patients with von Willebrand disease (VWD). The long-term efficacy and safety profile of pdVWF/FVIII was investigated in this multicenter, open-label, extension study.

Methods

Pediatric, adolescent, and adult patients with VWD who required treatment of non-surgical bleeds (NSBs), treatment during surgical events or who were receiving prophylaxis and who had completed one of two previous clinical trials of pdVWF/FVIII were included. Efficacy and safety analyses were performed for on-demand (n=10), prophylaxis (n=8), or on-demand and prophylaxis (n=2) treatment in patients pre-treated with pdVWF/FVIII for ≥12 months.

Results

Seven patients experienced a total of 402 NSBs in the on-demand arm, of which 77 required treatment and nine NSB events in three patients were considered major. Nine patients reported 118 NSBs in the prophylaxis arm, with 96 events requiring treatment and seven patients experiencing 12 major NSB events. Excellent or good hemostatic efficacy was reported by the investigator for 98.7% (on-demand) and 97.9% (prophylaxis) of NSB events treated with pdVWF/FVIII, without relevant differences between subgroups by age. pdVWF/FVIII was well tolerated, and the adverse events seen were mild-moderate and consistent with the safety profile for this product seen in other studies. There were no cases of anaphylactic reactions and angioedema, development of VWF/FVIII inhibitors, thromboembolic events, or viral infections.

Conclusion

This contemporary comprehensive development program evaluating pdVWF/FVIII across all ages demonstrates long-term safety and efficacy for treatment and prevention of bleeds in patients with severe VWD, supporting the benefit-risk profile of pdVWF/FVIII.

Pharmacokinetics and pharmacodynamics of a recombinant fusion protein linking activated coagulation factor VII with human albumin (rVIIa-FP) in patients with congenital FVII deficiency

Objectives: Recombinant fusion protein linking activated factor VIIa to human albumin (rVIIa-FP) is a therapeutic option designed to prevent and treat bleeding events in patients with congenital FVII deficiency with reduced infusion frequency compared to current FVII treatments. This study characterized the pharmacokinetics (PK) and pharmacodynamics (PD) of rVIIa-FP.Methods: A phase I multicenter, randomized, open-label, parallel-arm, single-dose study (NCT02470871) was conducted in nine patients with severe congenital FVII deficiency. Patients received their routine FVII product (30 IU/kg plasma-derived FVII [pdFVII] or 25 μg/kg recombinant activated FVII (rFVIIa) [eptacog alfa]), and were then randomly assigned to receive 100 or 300 μg/kg of rVIIa-FP. Blood samples for PK and PD assessments were drawn up to 48 hr after administration. FVIIa activity was determined using a one-stage clotting assay. PD parameters were derived from thrombin generation testing, using the Nijmegen hemostasis assay.Results: rVIIa-FP showed improved PK compared to rFVIIa, with 2- to 3-fold longer t_1/2 and 4- to 8-fold lower clearance. Analysis of PD data showed a sustained suppression of lag time below 4.5 min (upper limit of healthy people) for rVIIa-FP compared to rFVIIa. AUEC and EC_max were similar across the two dose groups of rVIIa-FP and rFVIIa.Discussion: rVIIa-FP was well tolerated in patients with congenital FVII deficiency, showed a longer half-life and lower clearance compared to rFVIIa, and lag time remaining within healthy ranges for ≥8 hr.Conclusion: These results warrant further investigation into the efficacy of rVIIa-FP to control and prevent bleeding in patients with FVII deficiency.

Pharmacokinetics, Efficacy and Safety of a Plasma-Derived VWF/FVIII Concentrate (Formulation V) in Pediatric Patients with von Willebrand Disease (SWIFTLY-VWD Study)

Purpose

Formulation V (VONCENTO^®) is a plasma-derived high-concentration/low-volume, high-purity von Willebrand factor (VWF)/factor VIII (FVIII) concentrate, originally indicated for von Willebrand disease (VWD) in adults and adolescents. This multicenter, open-label study (SWIFTLY-VWD) evaluated the pharmacokinetics (PK), as well as hemostatic efficacy and safety, of Formulation V in pediatric patients (<12 years) with severe VWD requiring treatment or prophylaxis of bleedings.

Methods

PK investigations were performed following one dose of Formulation V at Day 1 and 180. Nonsurgical bleeds were analyzed, while hemostatic efficacy was graded as excellent/good/moderate/none. Safety assessments included adverse events, and presence of VWF and/or FVIII inhibitors.

Results

Formulation V was administered as on-demand (N=13) or prophylaxis therapy (N=4) for 12 months (<6 years, N=9; 6 to <12 years, N=8). PK parameters for VWF markers were generally comparable to adults but showed lower VWF:ristocetin cofactor (RCo) exposure. Incidence of major bleeds was lower for prophylaxis (3.3%) than on-demand therapy (27.1%); joint bleeds were also lower (3.3% vs 11.5%, respectively). Investigator-reported excellent/good hemostatic efficacy against nonsurgical bleeds was 100%. No clinically relevant differences in PK, hemostatic efficacy, or safety were observed between age-groups (<6 years and 6 to <12 years). Formulation V was well tolerated. Adverse events were mild–moderate and consistent with the adult safety profile. No cases of anaphylactic reactions or angioedema, development of FVIII/VWF inhibitors, thromboembolic events, or viral infections were reported.

Conclusion

This study provides evidence for use of Formulation V to treat and prevent bleeding in pediatric patients with severe VWD, and led to the European approval of Formulation V in children.

TH17 Cell Frequency in Peripheral Blood Is Elevated in Overweight Children without Chronic Inflammatory Diseases

Background

The prevalence of obesity has dramatically increased in children in the last few decades and is associated with chronic inflammatory diseases. Fat tissue produces IL-6 and TNF-α, which are stimuli for T_H17 cell differentiation. These cells are characterized by expression of the transcription factor receptor-related orphan receptor C (RORC) and by IL-17A production. In murine models, obesity has been linked with elevated T_H17 cell frequencies. The aim of this study was to explore whether being overweight was associated with an elevated frequency of circulating T_H17 cells or elevated messenger RNA (mRNA)-levels of IL-17A and RORC in children without chronic inflammatory diseases.

Methods

We studied peripheral blood samples from 15 overweight and 50 non-overweight children without a history of autoimmune diseases, asthma, atopic dermatitis or allergic rhinoconjunctivitis. T_H17 cells were quantified in Ionomycin stimulated peripheral blood mononuclear cells by flow cytometry using intracellular IL-17A staining. RORC- and IL-17A expressions were measured by real-time PCR.

Results

We found significantly elevated T_H cell frequencies in overweight children compared then on-overweight controls with 34.7 ± 1.5% of CD3⁺CD4⁺ cells versus 25.4 ± 2.4% (mean ± SEM, p = 0.0023), respectively. Moreover, T_H cell frequencies correlated positively with body mass index (r = 0.42, p = 0.0005, respectively). The relative mRNA expression of RORC (p = 0.013) and IL-17A (p = 0.014) were upregulated in overweight compared to non-overweight children.

Conclusion

Childhood obesity is an independent factor that is associated with an elevated frequency of circulating T_H17 cells and higher expression of RORC- and IL-17A-mRNA after in vitro stimulation with Ionomycin. This might be due to the inflammatory activity of the fat tissue. Studies on T_H17 immunity should not only be adjusted for acute and chronic inflammatory diseases but also for overweight.

Mechanisms That Shape Human Antibody Repertoire Development in Mice Transgenic for Human Ig H and L Chain Loci

To determine the impact of the milieu on the development of the human B cell repertoire, we carried out a comprehensive analysis of productive and nonproductive Ig gene rearrangements from transgenic mice engineered to express single copies of the unrearranged human H chain and L chain Ig gene loci. By examining the nonproductive repertoire as an indication of the immediate product of the rearrangement machinery without an impact of selection, we discovered that the distribution of human rearrangements arising in the mouse was generally comparable to that seen in humans. However, differences between the distribution of nonproductive and productive rearrangements that reflect the impact of selection suggested species-specific selection played a role in shaping the respective repertoires. Although expression of some VH genes was similar in mouse and human (IGHV3-23, IGHV3-30, and IGHV4-59), other genes behaved differently (IGHV3-33, IGHV3-48, IGHV4-31, IGHV4-34, and IGHV1-18). Gene selection differences were also noted in L chains. Notably, nonproductive human VH rearrangements in the transgenic mice expressed shorter CDRH3 with less N addition. Even the CDRH3s in the productive rearrangements were shorter in length than those of the normal human productive repertoire. Amino acids in the CDRH3s in both species showed positive selection of tyrosines and glycines, and negative selection of leucines. The data indicate that the environment in which B cells develop can affect the expressed Ig repertoire by exerting influences on the distribution of expressed VH and VL genes and by influencing the amino acid composition of the Ag binding site.

Unlike in Children with Allergic Asthma, IgE Transcripts from Preschool Children with Atopic Dermatitis Display Signs of Superantigen-Driven Activation

The IgE repertoire in children with asthma reflects an adaptive B cell response, indicative of Ag-driven selection. However, the same might not apply to atopic dermatitis, which is often the first manifestation of atopy. The objective of our present study was to characterize the IgE repertoire of preschool children with atopic dermatitis with regard to signs of superantigen-like activation, clonal relationship, and indications of Ag selection. Total RNA was isolated from PBMCs of five children with atopic dermatitis. IgE transcripts were amplified, cloned, and sequenced using RT-PCR. We obtained 200 functional IgE sequences, which were compared with 1140 sequences from 11 children with asthma. Whereas variable gene segment of the H Ig chain (VH) gene usage in asthma reflected germline distribution, IgE transcripts from children with atopic dermatitis displayed a dominance of the otherwise scarcely expressed VH2 and VH4 family. Whereas IgE transcripts from children with asthma were highly mutated (7.2%), somatic mutation rate in atopic dermatitis was less than half as high (3.4%). Moreover, the proportion of transcripts that were indicative of Ag selection was reduced to 11% in atopic dermatitis (24% in asthma). In summary, IgE repertoires vary significantly between children with different atopic diseases. Compared with children with asthma, IgE transcripts from preschool children with atopic dermatitis are significantly less mutated, clonally less focused, and less indicative of Ag selection. We consider our data reconcilable with the hypothesis that a superantigen-like activation contributes to the maturation and selection of the IgE repertoire in atopic dermatitis.

The V gene repertoires of classical and atypical memory B cells in malaria-susceptible West African children

Immunity to Plasmodium falciparum malaria is naturally acquired in individuals living in malaria-endemic areas of Africa. Abs play a key role in mediating this immunity; however, the acquisition of the components of Ab immunity, long-lived plasma cells and memory B cells (MBCs), is remarkably inefficient, requiring years of malaria exposure. Although long-lived classical MBCs (CD19(+)/CD20(+)/CD21(+)/CD27(+)/CD10(-)) are gradually acquired in response to natural infection, exposure to P. falciparum also results in a large expansion of what we have termed atypical MBCs (CD19(+)/CD20(+)/CD21(-)/CD27(-)/CD10(-)). At present, the function of atypical MBCs in malaria is not known, nor are the factors that drive their differentiation. To gain insight into the relationship between classical and atypical IgG(+) MBCs, we compared the Ab H and L chain V gene repertoires of children living in a malaria-endemic region in Mali. We found that these repertoires were remarkably similar by a variety of criteria, including V gene usage, rate of somatic hypermutation, and CDR-H3 length and composition. The similarity in these repertoires suggests that classical MBCs and atypical MBCs differentiate in response to similar Ag-dependent selective pressures in malaria-exposed children and that atypical MBCs do not express a unique V gene repertoire.

IgG4 and IgE transcripts in childhood allergic asthma reflect divergent antigen-driven selection

The physiologic function of the "odd" Ab IgG4 remains enigmatic. IgG4 mediates immunotolerance, as, for example, during specific immunotherapy of allergies, but it mediates tissue damage in autoimmune pemphigus vulgaris and "IgG4-related disease." Approximately half of the circulating IgG4 molecules are bispecific owing to their unique ability to exchange half-molecules. Better understanding of the interrelation between IgG4 and IgE repertoires may yield insight into the pathogenesis of allergies and into potential novel therapies that modulate IgG4 responses. We aimed to compare the selective forces that forge the IgG4 and IgE repertoires in allergic asthma. Using an IgG4-specific RT-PCR, we amplified, cloned, and sequenced IgG4 H chain transcripts of PBMCs from 10 children with allergic asthma. We obtained 558 functional IgG4 sequences, of which 286 were unique. Compared with previously published unique IgE transcripts from the same blood samples, the somatic mutation rate was significantly enhanced in IgG4 transcripts (62 versus 83%; p < 0.001), whereas fewer IgG4 sequences displayed statistical evidence of Ag-driven selection (p < 0.001). On average, the hypervariable CDRH3 region was four nucleotides shorter in IgG4 than in IgE transcripts (p < 0.001). IgG4 transcripts in the circulation of children with allergic asthma reflect some characteristics of classical Ag-driven B2 immune responses but display less indication of Ag selection than do IgE transcripts. Although allergen-specific IgG4 can block IgE-mediated allergen presentation and degranulation of mast cells, key factors that influence the Ag-binding properties of the Ab differ between the overall repertoires of circulating IgG4- and IgE-expressing cells.

Differences in the composition of the human antibody repertoire by B cell subsets in the blood

The vast initial diversity of the antibody repertoire is generated centrally by means of a complex series of V(D)J gene rearrangement events, variation in the site of gene segment joining, and TdT catalyzed N-region addition. Although the diversity is great, close inspection has revealed distinct and unique characteristics in the antibody repertoires expressed by different B cell developmental subsets. In order to illustrate our approach to repertoire analysis, we present an in-depth comparison of V(D)J gene usage, hydrophobicity, length, D_H reading frame, and amino acid usage between heavy chain repertoires expressed by immature, transitional, mature, memory IgD⁺, memory IgD⁻, and plasmacytes isolated from the blood of a single individual. Our results support the view that in both human and mouse, the H chain repertoires expressed by individual, developmental B cell subsets appear to differ in sequence content. Sequencing of unsorted B cells from the blood is thus likely to yield an incomplete or compressed view of what is actually happening in the immune response of the individual. Our findings support the view that studies designed to correlate repertoire expression with diseases of immune function will likely require deep sequencing of B cells sorted by subset.

IgA response in preterm neonates shows little evidence of antigen-driven selection

After birth, contact to environmental Ags induces the production of IgA, which represents a first line of defense for the neonate. We sought to characterize the maturation of the repertoire of IgA H chain transcripts in circulating blood B cells during human ontogeny. We found that IgA H chain transcripts were present in cord blood as early as 27 wk of gestation and that the restrictions of the primary Ab repertoire (IgM) persisted in the IgA repertoire. Thus, B cells harboring more "mature" V(H) regions were not preferred for class switch to IgA. Preterm and term neonates expressed a unique IgA repertoire, which was characterized by short CDR-H3 regions, preference of the J(H) proximal D(H)7-27 gene segment, and very few somatic mutations. During the first postnatal months, these restrictions were slowly released. Preterm birth did not measurably accelerate the maturation of the IgA repertoire. At a postconceptional age of 60 wk, somatic mutation frequency of IgA H chain transcripts reached 25% of the adult values but still showed little evidence of Ag-driven selection. These results indicate that similar to IgG, the IgA repertoire expands in a controlled manner after birth. Thus, the IgA repertoire of the newborn has distinctive characteristics that differ from the adult IgA repertoire. These observations might explain the lower affinity and specificity of neonatal IgA Abs, which could contribute to a higher susceptibility to infections and altered responses to vaccinations, but might also prevent the development of autoimmune and allergic diseases.

Immunoglobulin analysis tool: a novel tool for the analysis of human and mouse heavy and light chain transcripts

Sequence analysis of immunoglobulin (Ig) heavy and light chain transcripts can refine categorization of B cell subpopulations and can shed light on the selective forces that act during immune responses or immune dysregulation, such as autoimmunity, allergy, and B cell malignancy. High-throughput sequencing yields Ig transcript collections of unprecedented size. The authoritative web-based IMGT/HighV-QUEST program is capable of analyzing large collections of transcripts and provides annotated output files to describe many key properties of Ig transcripts. However, additional processing of these flat files is required to create figures, or to facilitate analysis of additional features and comparisons between sequence sets. We present an easy-to-use Microsoft^® Excel^® based software, named Immunoglobulin Analysis Tool (IgAT), for the summary, interrogation, and further processing of IMGT/HighV-QUEST output files. IgAT generates descriptive statistics and high-quality figures for collections of murine or human Ig heavy or light chain transcripts ranging from 1 to 150,000 sequences. In addition to traditionally studied properties of Ig transcripts – such as the usage of germline gene segments, or the length and composition of the CDR-3 region – IgAT also uses published algorithms to calculate the probability of antigen selection based on somatic mutational patterns, the average hydrophobicity of the antigen-binding sites, and predictable structural properties of the CDR-H3 loop according to Shirai’s H3-rules. These refined analyses provide in-depth information about the selective forces acting upon Ig repertoires and allow the statistical and graphical comparison of two or more sequence sets. IgAT is easy to use on any computer running Excel^® 2003 or higher. Thus, IgAT is a useful tool to gain insights into the selective forces and functional properties of small to extremely large collections of Ig transcripts, thereby assisting a researcher to mine a data set to its fullest.

Antibody repertoires in humanized NOD-scid-IL2Rγ(null) mice and human B cells reveals human-like diversification and tolerance checkpoints in the mouse

Immunodeficient mice reconstituted with human hematopoietic stem cells enable the in vivo study of human hematopoiesis. In particular, NOD-scid-IL2Rγ^null engrafted mice have been shown to have reasonable levels of T and B cell repopulation and can mount T-cell dependent responses; however, antigen-specific B-cell responses in this model are generally poor. We explored whether developmental defects in the immunoglobulin gene repertoire might be partly responsible for the low level of antibody responses in this model. Roche 454 sequencing was used to obtain over 685,000 reads from cDNA encoding immunoglobulin heavy (IGH) and light (IGK and IGL) genes isolated from immature, naïve, or total splenic B cells in engrafted NOD-scid-IL2Rγ^null mice, and compared with over 940,000 reads from peripheral B cells of two healthy volunteers. We find that while naïve B-cell repertoires in humanized mice are chiefly indistinguishable from those in human blood B cells, and display highly correlated patterns of immunoglobulin gene segment use, the complementarity-determining region H3 (CDR-H3) repertoires are nevertheless extremely diverse and are specific for each individual. Despite this diversity, preferential D_H-J_H pairings repeatedly occur within the CDR-H3 interval that are strikingly similar across all repertoires examined, implying a genetic constraint imposed on repertoire generation. Moreover, CDR-H3 length, charged amino-acid content, and hydropathy are indistinguishable between humans and humanized mice, with no evidence of global autoimmune signatures. Importantly, however, a statistically greater usage of the inherently autoreactive IGHV4-34 and IGKV4-1 genes was observed in the newly formed immature B cells relative to naïve B or total splenic B cells in the humanized mice, a finding consistent with the deletion of autoreactive B cells in humans. Overall, our results provide evidence that key features of the primary repertoire are shaped by genetic factors intrinsic to human B cells and are principally unaltered by differences between mouse and human stromal microenvironments.

Novel bioactive metabolites of dipyrone (metamizol)

Dipyrone is a common antipyretic drug and the most popular non-opioid analgesic in many countries. In spite of its long and widespread use, molecular details of its fate in the body are not fully known. We administered dipyrone orally to mice. Two unknown metabolites were found, viz. the arachidonoyl amides of the known major dipyrone metabolites, 4-methylaminoantipyrine (2) and 4-aminoantipyrine (3). They were identified by ESI-LC-MS/MS after extraction from the CNS, and comparison with reference substances prepared synthetically. The arachidonoyl amides were positively tested for cannabis receptor binding (CB(1) and CB(2)) and cyclooxygenase inhibition (COX-1 and COX-2 in tissues and as isolated enzymes), suggesting that the endogenous cannabinoid system may play a role in the effects of dipyrone against pain.

Plasmapheresis prior to omalizumab administration in a 15-year-old boy with severe asthma and very high IgE levels: sustained effect over 2 years

BACKGROUND

Anti-IgE therapy with omalizumab is an innovative therapy option in patients with severe allergic asthma. However, many patients are excluded from this treatment due to very high serum IgE levels which lie above the weight-dependent cut-off for a reasonable omalizumab administration (700 kU/l).

OBJECTIVE

We sought to evaluate whether a preceding plasma exchange is suitable to establish the starting basis for a subsequent anti-IgE therapy in a 15 year-old boy with steroid-resistant unstable allergic asthma whose pretreatment serum IgE levels ranged between 3 000 and 8 000 kU/l.

METHODS

Our aim was to create a period with relatively low IgE serum concentrations, which could be overridden by a high dose of omalizumab. 3 sessions of plasmapheresis were performed and 3×3 000 ml plasma were exchanged against albumin solution.

RESULTS

We removed an absolute amount of 8 650 kU total IgE. During plasmapheresis, serum IgE levels markedly declined and fell below 500 kU/l. Immediately after the third plasma exchange, we started omalizumab therapy. As expected, total IgE levels began to rise again upon cessation of plasmapheresis, and after 2 months the pre-treatment values were reached. In contrast, serum concentrations of free IgE remained stable on a level of about 80 kU/l during the whole observation period. During this period, the boy displayed a considerable improvement of asthma control and an increase in quality of life. In addition, his previously poor lung function normalized.

CONCLUSIONS

Plasmapheresis prior to omalizumab administration is suitable to temporarily reduce grossly elevated serum IgE levels and might facilitate anti-IgE therapy in selected patients previously considered not suitable for this therapy.

A single DH gene segment is sufficient for the establishment of an asthma phenotype in a murine model of allergic airway inflammation

BACKGROUND

We have previously shown that the allergic sensitization to ovalbumin does not represent a superantigen-like immune response. In gene-targeted mice (ΔD-iD) with a single modified Diversity gene segment (D(H)) of the immunoglobulin heavy chain, enriched for charged amino acids, the asthma phenotype in a murine model was markedly alleviated compared to wild-type animals.

OBJECTIVE

We now sought to determine whether the confinement to a single D(H) gene segment alone leads to a reduced allergic phenotype.

METHODS

We examined another gene-targeted mouse strain (ΔD-DFL) with a single D(H) gene segment which encodes for neutral amino acids, thus reflecting the preferential repertoire in wild-type mice. Mice were sensitized intraperitoneally to ovalbumin.

RESULTS

Despite the constraint to a single D(H) gene segment, ΔD-DFL mice mounted high total and allergen-specific IgG(1) and IgE serum levels after sensitization to ovalbumin. The affinity constants of allergen-specific IgG(1) antibodies did not differ between ΔD-DFL and wild type. Following challenge with aerosolized allergen, a marked local T(H)2 cytokine response and an eosinophilic airway inflammation developed. Quantitative histology revealed increased mucus production and intense goblet cell metaplasia which were identical to those in wild type. Moreover, ΔD-DFL mice developed an airway hyperreactivity to methacholine and to the specific allergen, which both did not differ from those in wild-type animals.

CONCLUSION

A single D(H) gene segment is sufficient for the establishment of the asthma phenotype in a murine model of allergic airway inflammation. Thus, the allergic phenotype depends on the amino acid composition and not on the diversity of the classical antigen-binding site.

IgE transcripts in the circulation of allergic children reflect a classical antigen-driven B cell response and not a superantigen-like activation

Allergic asthma is the most frequent chronic disorder in childhood. Although IgE is a central effector molecule in allergic diseases, the nature of the IgE response is still under debate. The objective of our study was to clarify whether the IgE repertoire in the circulation of allergic children represents a classical Ag-driven and oligoclonal B cell response, a superantigen-like activation of a subset of B cells, or a polyclonal B-1 cell expansion. Using a highly sensitive RT-PCR method, we amplified, cloned, and sequenced IgE H chain transcripts from 13 children with allergic asthma. We gained 1366 functional IgE sequences, which currently represent the most extensive collection of human IgE transcripts. Compared to IgM transcripts from the same children, the somatic mutation rate was significantly enhanced in IgE transcripts (21 per thousand versus 72 per thousand; p < 0.001), which renders a polyclonal B-1 response unlikely. Moreover, IgE sequences displayed significantly enhanced Ag selection and hence were indicative of a classical Ag-driven immune response with affinity maturation (p < 0.001). In contrast to several recent studies, the usage pattern of variable gene segment of the H Ig chain in IgE transcripts followed the germline complexity, arguing against a superantigen-like interaction. We conclude that IgE transcripts in the circulation of children with allergic asthma reflect a classical adaptive B-2 cell response. This study provides reference data for a better characterization of the IgE response under immunomodulating therapies, such as anti-IgE therapy or allergen-specific immunotherapy.

Composition of the immunoglobulin classic antigen-binding site regulates allergic airway inflammation in a murine model of experimental asthma

BACKGROUND

When bound to mast cell FcepsilonRI, IgE serves as antigen receptor for allergic reactions, permitting specific identification of the allergen. Although the core of the classic antigen-binding site is heavy chain complementarity determining region 3 (CDR-H3), recent studies suggest that allergens might also bind IgE in a superantigen-like fashion outside the classic antigen-binding site.

OBJECTIVE

We sought to evaluate the contribution of the classic CDR-H3-centric antigen-binding site to the development of an allergic phenotype.

METHODS

Using a murine model of experimental asthma, we characterized a gene-targeted mouse strain expressing an altered range of CDR-H3s (DeltaD-iD mice) in response to the hydrophobic allergen ovalbumin (OVA). Mutant and wild-type (wt) mice were sensitized intraperitoneally with OVA; non-sensitized mice served as controls.

RESULTS

We found the composition of the classic CDR-H3-centric antigen-binding site to be critical for the development of characteristic aspects of allergic asthma. (i) Compared with wt animals, DeltaD-iD mice showed a significantly less pronounced OVA-induced rise in allergen-specific IgE levels and hence in total serum IgE levels. (ii) In addition, DeltaD-iD mice demonstrated a significant reduction in eosinophilic airway inflammation, as well as in interleukin-4 (IL-4), IL-5 and IL-13 levels in BAL fluids.

CONCLUSION

Allergic sensitization and airway inflammation depend on the composition of the predominant CDR-H3 repertoire, suggesting that the classic CDR-H3-centric antigen-binding site plays a crucial role in creating the immunological interface between allergen and IgE. Our results further emphasize a central role of IgE, not only in mediating but also in regulating the allergic immune response.

A classification of drug substances according to their mechanism of action

Different classification systems for therapeutic agents exist. The most commonly used one is the ATC Code (ATC: Anatomy, Therapeutic properties, Chemical, pharmacological properties). Here, an alternative classification system (TCAT: Target-Chemistry-Anatomy-Therapy) is proposed which refers to the molecular mechanism of action or rather, target. The main subgroups of targets are: enzymes; substrates, metabolies, proteins; receptors; ion channels; transporter molecules and systems; nucleic acids, ribosomes; physicochemical mechanisms; antigen-antibody reactions; unknown targets. This target-oriented approach may be particularly useful in teaching advanced medicinal chemistry.