COVID-19 Vaccination in Patients with Inborn Errors of Immunity Reduces Hospitalization and Critical Care Needs Related to COVID-19: a USIDNET Report

BACKGROUND

The CDC and ACIP recommend COVID-19 vaccination for patients with inborn errors of immunity (IEI). Not much is known about vaccine safety in IEI, and whether vaccination attenuates infection severity in IEI.

OBJECTIVE

To estimate COVID-19 vaccination safety and examine effect on outcomes in patients with IEI.

METHODS

We built a secure registry database in conjunction with the US Immunodeficiency Network to examine vaccination frequency and indicators of safety and effectiveness in IEI patients. The registry opened on January 1, 2022, and closed on August 19, 2022.

RESULTS

Physicians entered data on 1245 patients from 24 countries. The most common diagnoses were antibody deficiencies (63.7%). At least one COVID-19 vaccine was administered to 806 patients (64.7%), and 216 patients received vaccination prior to the development of COVID-19. The most common vaccines administered were mRNA-based (84.0%). Seventeen patients were reported to seek outpatient clinic or emergency room care for a vaccine-related complication, and one patient was hospitalized for symptomatic anemia. Eight hundred twenty-three patients (66.1%) experienced COVID-19 infection. Of these, 156 patients required hospitalization (19.0%), 47 required ICU care (5.7%), and 28 died (3.4%). Rates of hospitalization (9.3% versus 24.4%, p < 0.001), ICU admission (2.8% versus 7.6%, p = 0.013), and death (2.3% versus 4.3%, p = 0.202) in patients who had COVID-19 were lower in patients who received vaccination prior to infection. In adjusted logistic regression analysis, not having at least one COVID-19 vaccine significantly increased the odds of hospitalization and ICU admission.

CONCLUSION

Vaccination for COVID-19 in the IEI population appears safe and attenuates COVID-19 severity.

Factors Influencing Career Choice of Allergy and Immunology Fellows-in-Training: A Work Group Report of the AAAAI Program Directors Assembly Executive Committee

BACKGROUND

As the burden of allergic and immunologic disease continues to increase, there is increased demand for a larger Allergy and Immunology (AI) subspecialty workforce. The field must prioritize the expansion of our workforce and the recruitment of exceptional and diverse trainees to ensure the vitality of the specialty. Although the AI fellowship match has traditionally been competitive, recent trends in fellowship applications have demonstrated fewer applicants per fellowship position. This trend has made recruitment a priority on the agenda of the national AI societies.

OBJECTIVE

To elucidate key factors influencing the decision to choose the field of AI by querying fellows-in-training.

METHODS

A survey was created and distributed yearly to fellows-in-training from 2017 to 2021 to identify factors influencing a career choice in AI.

RESULTS

Approximately 59% of respondents rotated with AI in residency and 35% in both medical school and residency. Most respondents reported having a mentor in the field before fellowship, and many had their first exposures to AI during medical school (40%) or residency (32%). Most respondents decided to pursue AI during residency. The most common factors that influenced the decision to pursue AI were work/life balance, clinical aspects of the field, mentorship, and research opportunities.

CONCLUSIONS

Our data suggest that the decision to pursue a career in AI often occurs during residency training and is motivated primarily by work/life balance, clinical aspects of the field, and clinician mentorship. Our survey results could provide guidance to AI training programs on strategies to recruit exceptional and diverse trainees.

Evaluation of association of anti-PEG antibodies with anaphylaxis after mRNA COVID-19 vaccination

BACKGROUND

The mechanism for anaphylaxis following mRNA COVID-19 vaccination has been widely debated; understanding this serious adverse event is important for future vaccines of similar design. A mechanism proposed is type I hypersensitivity (i.e., IgE-mediated mast cell degranulation) to polyethylene glycol (PEG). Using an assay that, uniquely, had been previously assessed in patients with anaphylaxis to PEG, our objective was to compare anti-PEG IgE in serum from mRNA COVID-19 vaccine anaphylaxis case-patients and persons vaccinated without allergic reactions. Secondarily, we compared anti-PEG IgG and IgM to assess alternative mechanisms.

METHODS

Selected anaphylaxis case-patients reported to U.S. Vaccine Adverse Event Reporting System December 14, 2020-March 25, 2021 were invited to provide a serum sample. mRNA COVID-19 vaccine study participants with residual serum and no allergic reaction post-vaccination ("controls") were frequency matched to cases 3:1 on vaccine and dose number, sex and 10-year age category. Anti-PEG IgE was measured using a dual cytometric bead assay (DCBA). Anti-PEG IgG and IgM were measured using two different assays: DCBA and a PEGylated-polystyrene bead assay. Laboratorians were blinded to case/control status.

RESULTS

All 20 case-patients were women; 17 had anaphylaxis after dose 1, 3 after dose 2. Thirteen (65 %) were hospitalized and 7 (35 %) were intubated. Time from vaccination to serum collection was longer for case-patients vs controls (post-dose 1: median 105 vs 21 days). Among Moderna recipients, anti-PEG IgE was detected in 1 of 10 (10 %) case-patients vs 8 of 30 (27 %) controls (p = 0.40); among Pfizer-BioNTech recipients, it was detected in 0 of 10 case-patients (0 %) vs 1 of 30 (3 %) controls (p >n 0.99). Anti-PEG IgE quantitative signals followed this same pattern. Neither anti-PEG IgG nor IgM was associated with case status with both assay formats.

CONCLUSION

Our results support that anti-PEG IgE is not a predominant mechanism for anaphylaxis post-mRNA COVID-19 vaccination.

Predictors of Acute Care Reutilization in Pediatric Patients With Amoxicillin-Associated Reactions

BACKGROUND

Amoxicillin-associated reactions (AARs) contribute to substantial health care utilization, with a reutilization rate of 10% in pediatric emergency department (ED) and urgent care (UC) settings.

OBJECTIVE

To identify predictors of ED/UC reutilization by examining patients' clinical features and providers' management of AARs.

METHODS

Through a retrospective chart review of 668 patients presenting with AARs over 2 years to the pediatric ED/UC, we examined clinical features associated with ED/UC reutilization, including rash phenotype, systemic symptoms (fever, angioedema, joint involvement, gastrointestinal symptoms), and providers' management (pharmacologic treatment and counseling). We then constructed a statistical model to predict ED/UC reutilization using stepwise backward model selection.

RESULTS

ED/UC reutilizers were more likely to be male (P = .008) and have fever (P = .0001), angioedema (P < .0001), joint involvement (P < .0001), and gastrointestinal symptoms (P = .0001) during their AAR course. Rash phenotypes differed between groups (P < .0001), as ED/UC reutilizers more frequently exhibited urticaria. However, there were no differences in clinical management between groups, including pharmacologic recommendations, at the initial ED/UC encounter. In addition, our statistical model identified younger patients <2 years of age as more likely to reutilize ED/UC resources if providers did not document specific return precautions (odds ratio, 3.6; 95% confidence interval, 1.7-7.7).

CONCLUSION

Recognition of clinical features and treatment gaps associated with ED/UC reutilization will guide interventions to optimize care in children presenting with AARs, such as improved anticipatory guidance and early allergy consultation. Prospective studies are needed to determine whether these interventions will reduce ED/UC reutilization and facilitate timely allergy testing.

Distinct Characteristics and Chronology of Amoxicillin-Associated Reactions in Pediatric Acute Care Settings

BACKGROUND

Amoxicillin-associated reactions (AARs) in children presenting as rashes are common, and recent data suggest that >90% tolerate amoxicillin on re-exposure. However, additional data would help pediatricians and allergists gain confidence in referring and testing children who experienced systemic symptoms perceived as "worrisome," thus leading to urgent medical evaluations. By characterizing the entire spectrum of AAR symptoms in pediatric patients presenting to emergency department (ED)/urgent care (UC) settings, we sought to increase our diagnostic acumen to guide subsequent allergy evaluations.

OBJECTIVE

To fully characterize clinical features of rash and systemic symptoms in children presenting to the ED/UC with AARs.

METHODS

A retrospective chart review of children seen in the ED/UC from July 1, 2015, to June 30, 2017, was conducted. Clinical features, chronology, and seasonality were detailed, and cases were classified into 3 previously described AAR phenotypes: maculopapular exanthem (MPE), urticaria, and serum sickness-like reactions (SSLRs), if they experienced joint symptoms.

RESULTS

Children (n = 668; median age: 1.8 years) presented to the ED/UC with urticaria (44%), MPE (36%), and SSLRs (11%) typically on days 7 to 10 of amoxicillin. Although children with SSLRs were more frequently treated with corticosteroids (28%, P < .0001) and exhibited higher rates of "worrisome" features (fever, angioedema, or gastrointestinal symptoms; 73%, P < .0001), delayed-onset systemic symptoms were identified frequently in all 3 groups. ED/UC reutilization was unexpectedly high with 66 children (10%) returning to the ED/UC for re-evaluation.

CONCLUSION

"Worrisome" symptoms are common in children presenting to the ED/UC with AARs. Future studies are needed to determine the impact on subsequent referral and allergy testing.

Respiratory Infections in Patients with Primary Immunodeficiency

Recurrent and life-threatening respiratory infections are nearly universal in patients with primary immunodeficiency diseases (PIDD). Early recognition, aggressive treatment, and prophylaxis with antimicrobials and immunoglobulin replacement have been the mainstays of management and will be reviewed here with an emphasis on respiratory infections. Genetic discoveries have allowed direct translation of research to clinical practice, improving our understanding of clinical patterns of pathogen susceptibilities and guiding prophylaxis. The recent identification of inborn errors in type I interferon signaling as a basis for life-threatening viral infections in otherwise healthy individuals suggests another targetable pathway for treatment and/or prophylaxis. The future of PIDD diagnosis will certainly involve early genetic identification by newborn screening before onset of infections, with early treatment offering the potential of preventing disease complications such as chronic lung changes. Gene editing approaches offer tremendous therapeutic potential, with rapidly emerging delivery systems. Antiviral therapies are desperately needed, and specific cellular therapies show promise in patients requiring hematopoietic stem cell transplantation. The introduction of approved therapies for clinical use in PIDD is limited by the difficulty of studying outcomes in rare patients/conditions with conventional clinical trials.

Anaphylaxis knowledge gaps and future research priorities: A consensus report

BACKGROUND

Despite a better understanding of the epidemiology, pathogenesis, and management of patients with anaphylaxis, there remain knowledge gaps. Enumerating and prioritizing these gaps would allow limited scientific resources to be directed more effectively.

OBJECTIVE

We sought to systematically describe and appraise anaphylaxis knowledge gaps and future research priorities based on their potential impact and feasibility.

METHODS

We convened a 25-member multidisciplinary panel of anaphylaxis experts. Panelists formulated knowledge gaps/research priority statements in an anonymous electronic survey. Four anaphylaxis themed writing groups were formed to refine statements: (1) Population Science, (2) Basic and Translational Sciences, (3) Emergency Department Care/Acute Management, and (4) Long-Term Management Strategies and Prevention. Revised statements were incorporated into an anonymous electronic survey, and panelists were asked to rate the impact and feasibility of addressing statements on a continuous 0 to 100 scale.

RESULTS

The panel generated 98 statements across the 4 anaphylaxis themes: Population Science (29), Basic and Translational Sciences (27), Emergency Department Care/Acute Management (24), and Long-Term Management Strategies and Prevention (18). Median scores for impact and feasibility ranged from 50.0 to 95.0 and from 40.0 to 90.0, respectively. Key statements based on median rating for impact/feasibility included the need to refine anaphylaxis diagnostic criteria, identify reliable diagnostic, predictive, and prognostic anaphylaxis bioassays, develop clinical prediction models to standardize postanaphylaxis observation periods and hospitalization criteria, and determine immunotherapy best practices.

CONCLUSIONS

We identified and systematically appraised anaphylaxis knowledge gaps and future research priorities. This study reinforces the need to harmonize scientific pursuits to optimize the outcomes of patients with and at risk of anaphylaxis.

COVID-19 mRNA vaccine allergy

PURPOSE OF REVIEW

A known history of a severe allergic reaction (e.g., anaphylaxis) to any component of the vaccine is the only contraindication to coronavirus disease 2019 (COVID-19) mRNA vaccination. It is important for pediatricians to understand the likelihood of an allergic reaction to COVID-19 mRNA vaccines, including its excipients.

RECENT FINDINGS

Episodes concerning for anaphylaxis were immediately reported following early administration of COVID-19 mRNA vaccines to adults. Although allergic type symptoms were reported equally in recipients of placebos and test vaccines in phase 3 clinical trials, post-authorization prospective studies state that 0.2-2% of vaccine recipients have experienced allergic reactions. Subsequent allergy testing of affected individuals has focused largely on evaluation of allergic sensitization to a novel vaccine excipient, polyethylene glycol (PEG). PEG is a polymer incorporated in numerous pharmaceutical products because of its favorable, inert properties. The results of allergy testing in adults to date indicate that IgE mediated anaphylaxis to PEG allergy is rarely identified after COVID-19 mRNA vaccine reactions. Numerous individuals with presumed anaphylaxis have tolerated a second vaccine after evaluation and testing by an allergist, suggesting either misdiagnosis or a novel immune mechanism.

SUMMARY

Confirmed anaphylactic reactions to COVID-19 mRNA vaccines are rare, likely due to a lack of preexisting IgE against the vaccine components, including PEG.

Potential mechanisms of anaphylaxis to COVID-19 mRNA vaccines

Anaphylaxis to vaccines is historically a rare event. The coronavirus disease 2019 pandemic drove the need for rapid vaccine production applying a novel antigen delivery system: messenger RNA vaccines packaged in lipid nanoparticles. Unexpectedly, public vaccine administration led to a small number of severe allergic reactions, with resultant substantial public concern, especially within atopic individuals. We reviewed the constituents of the messenger RNA lipid nanoparticle vaccine and considered several contributors to these reactions: (1) contact system activation by nucleic acid, (2) complement recognition of the vaccine-activating allergic effector cells, (3) preexisting antibody recognition of polyethylene glycol, a lipid nanoparticle surface hydrophilic polymer, and (4) direct mast cell activation, coupled with potential genetic or environmental predispositions to hypersensitivity. Unfortunately, measurement of anti-polyethylene glycol antibodies in vitro is not clinically available, and the predictive value of skin testing to polyethylene glycol components as a coronavirus disease 2019 messenger RNA vaccine-specific anaphylaxis marker is unknown. Even less is known regarding the applicability of vaccine use for testing (in vitro/vivo) to ascertain pathogenesis or predict reactivity risk. Expedient and thorough research-based evaluation of patients who have suffered anaphylactic vaccine reactions and prospective clinical trials in putative at-risk individuals are needed to address these concerns during a public health crisis.

Severity grading system for acute allergic reactions: A multidisciplinary Delphi study

BACKGROUND

There is no widely adopted severity grading system for acute allergic reactions, including anaphylactic and nonanaphylactic reactions, thus limiting the ability to optimize and standardize management practices and advance research.

OBJECTIVE

The aim of this study was to develop a severity grading system for acute allergic reactions for use in clinical care and research.

METHODS

From May to September 2020, we convened a 21-member multidisciplinary panel of allergy and emergency care experts; 9 members formed a writing group to critically appraise and assess the strengths and limitations of prior severity grading systems and develop the structure and content for an optimal severity grading system. The entire study panel then revised the grading system and sought consensus by utilizing Delphi methodology.

RESULTS

The writing group recommended that an optimal grading system encompass the severity of acute allergic reactions on a continuum from mild allergic reactions to anaphylactic shock. Additionally, the severity grading system must be able to discriminate between clinically important differences in reaction severity to be relevant in research while also being intuitive and straightforward to apply in clinical care. Consensus was reached for all elements of the proposed severity grading system.

CONCLUSION

We developed a consensus severity grading system for acute allergic reactions, including anaphylactic and nonanaphylactic reactions. Successful international validation, refinement, dissemination, and application of the grading system will improve communication among providers and patients about the severity of allergic reactions and will help advance future research.

Persistent, refractory, and biphasic anaphylaxis: A multidisciplinary Delphi study

BACKGROUND

The use of inconsistent definitions for anaphylaxis outcomes limits our understanding of the natural history and epidemiology of anaphylaxis, hindering clinical practice and research efforts.

OBJECTIVE

Our aim was to develop consensus definitions for clinically relevant anaphylaxis outcomes by utilizing a multidisciplinary group of clinical and research experts in anaphylaxis.

METHODS

Using Delphi methodology, we developed agenda topics and drafted questions to review during monthly conference calls. Through online surveys, a 19-member panel consisting of experts in allergy and/or immunology and emergency medicine rated their level of agreement with the appropriateness of statements on a scale of 1 to 9. A median value of 1.0 to 3.4 was considered inappropriate, a median value of 3.5 to 6.9 was considered uncertain, and a median value of 7.0 to 9.0 was considered appropriate. A disagreement index was then calculated, with values less than 1.0 categorized as "consensus reached." If consensus was not reached after the initial survey, subsequent surveys incorporating the aggregate de-identified responses from prior surveys were sent to panel members. This process was repeated until consensus was reached or 4 survey rounds had been completed, after which the question was categorized as "no consensus reached."

RESULTS

The panel developed outcome definitions for persistent, refractory, and biphasic anaphylaxis, as well as for persistent and biphasic nonanaphylactic reactions. There was also consensus among panel members regarding the need to develop an anaphylaxis severity grading system.

CONCLUSION

Dissemination and application of these definitions in clinical care and research will help standardize the terminology used to describe anaphylaxis outcomes and serve as the foundation for future research, including research aimed at development of an anaphylaxis severity grading system.

SMAC mimetic in combination with HDACi effectively release brakes on cell death of chronic myeloid leukemia K562 cells accelerating ligand-mediated apoptosis

Enthusiasm for immunotherapy has reached an all-time high within the last year due to remarkable clinical outcomes using strategies directed at activating T cells. The mechanisms by which newly activated T cells execute tumor target cells have not been described; it is assumed that CD4 and CD8 T cells may utilize ligation of TNF receptor family members, Fas, TNF, and TRAIL. However, not all tumors are susceptible to T cell killing by death receptor ligands. Chronic myeloid leukemia K562 cells are notably resistant to pro-apoptotic, ligand-induced cell death; whereas, T cell leukemia Jurkat cells undergo rapid caspase 3/7 activation and cell death (within 4–6 hours) in response to pro-apoptotic death ligands Fas and TRAIL. We hypothesized that K562 cells may be sensitized to respond similarly by targeting the regulatory proteins controlling activation of executioner and/or initiator caspases, thus accelerating cell death. SMAC mimetic compounds (SMC) are a novel class of drugs that target pro-survival signaling molecules. Single agent treatment with SMC enhanced TRAIL- and TNF-induced caspase activation, but had only modest effects on cell death after 24 hours. Addition of histone deacetylase inhibitors (HDACi) in combination with SMC, accelerated TNF- and TRAIL- mediated caspase activation and led to rapid cell death in K562 cells. By relieving multiple levels of inhibition in the tumor targets, we achieved rapid and efficient killing of previously resistant tumor cells using recombinant death receptor ligands. Combination therapy with SMC and HDACi may enhance current immunotherapy approaches designed to 1) activate tumor specific T cells expressing death receptor ligands or 2) administer recombinant ligands such as TRAIL.

Real-time detection of CTL function reveals distinct patterns of caspase activation mediated by Fas versus granzyme B

Activation of caspase-mediated apoptosis is reported to be a hallmark of both granzyme B- and Fas-mediated pathways of killing by CTLs; however, the kinetics of caspase activation remain undefined owing to an inability to monitor target cell-specific apoptosis in real time. We have overcome this limitation by developing a novel biosensor assay that detects continuous, protease-specific activity in target cells. Biosensors were engineered from a circularly permuted luciferase, linked internally by either caspase 3/7 or granzyme B/caspase 8 cleavage sites, thus allowing activation upon proteolytic cleavage by the respective proteases. Coincubation of murine CTLs with target cells expressing either type of biosensor led to a robust luminescent signal within minutes of cell contact. The signal was modulated by the strength of TCR signaling, the ratio of CTL/target cells, and the type of biosensor used. Additionally, the luciferase signal at 30 min correlated with target cell death, as measured by a (51)Cr-release assay. The rate of caspase 3/7 biosensor activation was unexpectedly rapid following granzyme B- compared with Fas-mediated signal induction in murine CTLs; the latter appeared gradually after a 90-min delay in perforin- or granzyme B-deficient CTLs. Remarkably, the Fas-dependent, caspase 3/7 biosensor signal induced by perforin-deficient human CTLs was also detectable after a 90-min delay when measured by redirected killing. Thus, we have used a novel, real-time assay to demonstrate the distinct pattern of caspase activation induced by granzyme B versus Fas in human and murine CTLs.

Elevated Granzyme B in Cytotoxic Lymphocytes is a Signature of Immune Activation in Hemophagocytic Lymphohistiocytosis

Patients with hemophagocytic lymphohistiocytosis (HLH) exhibit immune hyper-activation as a consequence of genetic defects in secretory granule proteins of cytotoxic T lymphocytes (CTL) and natural killer (NK) cells. Murine models of HLH demonstrate significant activation of CTL as central to the disease pathogenesis, but evaluation of CTL and NK activation in children with HLH or inflammatory conditions is not well described. CD8 T cells only express granzyme B (GrB) following stimulation and differentiation into CTL; therefore, we reasoned that GrB expression may serve as a signature of CTL activation. It is unknown whether human NK cells are similarly activated in vivo, as marked by increased granule proteins. Perforin and GrB levels are measured in both CTL and NK cells by flow cytometry to diagnose perforin deficiency. We retrospectively compared GrB expression in blood samples from 130 children with clinically suspected and/or genetically defined HLH to age-matched controls. As predicted, CD8 expressing GrB cells were increased in HLH, regardless of genetic etiology. Remarkably, the GrB protein content also increased in NK cells in patients with HLH and decreased following immunosuppressive therapy. This suggests that in vivo activation of NK cells occurs in hyper-inflammatory conditions. We conclude that increased detection of GrB in CTL and NK are an immune signature for lymphocyte activation in HLH, irrespective of genetic subtype and may also be a useful measure of immune activation in other related conditions.

A rapid flow cytometric screening test for X-linked lymphoproliferative disease due to XIAP deficiency

BACKGROUND

Deficiency of X-linked inhibitor of apoptosis (XIAP), caused by BIRC4 gene mutations, is the second known cause of X-linked lymphoproliferative disease (XLP), a rare primary immunodeficiency that often presents with life-threatening hemophagocytic lymphohistiocytosis (HLH). Rapid diagnosis of the known genetic causes of HLH, including XIAP deficiency, facilitates the initiation of life-saving treatment and preparation for allogeneic hematopoietic cell transplantation (HCT). Until now, a rapid screening test for XIAP deficiency has not been available.

METHODS

To develop a flow cytometric screening test for XIAP deficiency, we first used lymphoblastic cell lines generated from controls and patients with BIRC4 mutations to identify two commercially available antibodies specific for native intracellular XIAP. Next, we used these antibodies to study control whole blood leukocyte XIAP expression. We then studied XIAP expression in leukocytes from patients with XLP due to BIRC4 mutations, maternal carriers, and patients following HCT.

RESULTS

XIAP was expressed by the majority of all whole blood nucleated cells in normal controls. In contrast, XIAP was absent or decreased in all lymphocyte subsets, monocytes and granulocytes from four unrelated patients with XLP due to BIRC4 mutations. Bimodal distribution of XIAP expression was evident in two maternal carriers, with significant skewing toward cells expressing normal XIAP. Bimodal distribution was also observed in a patient following HCT.

CONCLUSIONS

Flow cytometric analysis of intracellular XIAP provides a rapid screening test for XLP due to XIAP deficiency. It also allows carrier detection and can be used to monitor donor versus recipient reconstitution following HCT.

Patients with X-linked lymphoproliferative disease due to BIRC4 mutation have normal invariant natural killer T-cell populations

Human invariant natural killer T cells (iNKT cells) are a unique population of T cells that express an invariantly rearranged T-cell receptor (TCR) composed of TCRValpha24 and TCRVbeta11 chains which recognize glycosphingolipid antigens presented by the CD1d molecule. iNKT cells are absent in patients with X-linked lymphoproliferative disease (XLP) due to SH2D1A mutation, and are reported to be decreased in patients with XLP due to BIRC4 mutations. However, mice deficient in the BIRC4 gene product, X-linked Inhibitor of Apoptosis (XIAP), have normal iNKT cell populations. Because of this, we studied iNKT cell populations in 6 patients with XLP due to BIRC4 mutations, with comparison to 103 pediatric and adult normal control samples. We found that iNKT cells constitute 0.008%-1.176% of normal peripheral blood T cells, and that iNKT cell populations were normal or increased in patients with BIRC4 mutations. We conclude that XLP due to BIRC4 mutation is not associated with decreased populations of iNKT cells, and that XIAP is likely not a requirement for iNKT cell development.

Functional assessment of perforin C2 domain mutations illustrates the critical role for calcium-dependent lipid binding in perforin cytotoxic function

Perforin-mediated lymphocyte cytotoxicity is critical for pathogen elimination and immune homeostasis. Perforin disruption of target cell membranes is hypothesized to require binding of a calcium-dependent, lipid-inserting, C2 domain. In a family affected by hemophagocytic lymphohistiocytosis, a severe inflammatory disorder caused by perforin deficiency, we identified 2 amino acid substitutions in the perforin C2 domain: T435M, a previously identified mutant with disputed pathogenicity, and Y438C, a novel substitution. Using biophysical modeling, we predicted that the T435M substitution, but not Y438C, would interfere with calcium binding and thus cytotoxic function. The capacity for cytotoxic function was tested after expression of the variant perforins in rat basophilic leukemia cells and murine cytotoxic T lymphocytes. As predicted, cells transduced with perforin-T435M lacked cytotoxicity, but those expressing perforin-Y438C displayed intact cytotoxic function. Using novel antibody-capture and liposome-binding assays, we found that both mutant perforins were secreted; however, only nonmutated and Y438C-substituted perforins were capable of calcium-dependent lipid binding. In addition, we found that perforin-Y438C was capable of mediating cytotoxicity without apparent proteolytic maturation. This study clearly demonstrates the pathogenicity of the T435M mutation and illustrates, for the first time, the critical role of the human perforin C2 domain for calcium-dependent, cytotoxic function.

Interplay of adaptive th2 immunity with eotaxin-3/c-C chemokine receptor 3 in eosinophilic esophagitis

BACKGROUND

Pediatric eosinophilic esophagitis (EE) is a recently described disorder associated with atopy. Although studies of esophageal tissue suggest that Th2 cytokines and eotaxin-3 may be crucial in disease pathogenesis, little is known about the systemic immunological phenotypes of children with EE.

OBJECTIVES

To define the phenotypes of peripheral blood eosinophils and lymphocytes in EE and to examine for correlations between these parameters and tissue eosinophil numbers and disease severity.

PATIENTS AND METHODS

Blood was collected from children with EE, atopic control children without EE, and nonatopic control children without EE. Flow cytometry was used to measure eosinophil expression of chemokine receptor 3 (CCR3) and interleukin-5 receptor-alpha (IL-5Ralpha), and intracellular lymphocyte expression of IL-4, IL-5, IL-13, interferon-gamma, and tumor necrosis factor-alpha. Eosinophil numbers and eotaxin-3 mRNA levels were quantitated in esophageal biopsy specimens.

RESULTS

Compared with nonatopic control children, EE patients with active disease had increased peripheral blood eosinophil percentages, mean channel of fluorescence (MCF) of CCR3 on eosinophils, and percentage of CD4+ T cells expressing IL-5. Notably, these parameters positively correlated with esophageal eosinophil numbers. Eotaxin-3 tissue expression positively correlated with esophageal eosinophil numbers and peripheral blood eosinophil CCR3 MCF. The percentage of peripheral blood eosinophils, eosinophil CCR3 MCF, and CD4+ T cell expression of IL-5 were lower in EE patients in disease remission than in patients with active disease.

CONCLUSIONS

Collectively, these studies demonstrate cooperation between systemic CD4+ Th2-cell-mediated immunity and an enhanced eosinophil-CCR3/eotaxin-3 pathway in EE pathogenesis. Furthermore, the imbalanced Th2 immunity and increased CCR3 expression are reversible with disease remission.

A Kindred of Children With Interstitial Lung Disease

BACKGROUND

Childhood interstitial lung disease (ILD) is a spectrum of diseases including many different rare lung conditions. We present a family with an unusual presentation of ILD in association with rheumatologic and immunologic abnormalities.

METHODS

Eight children with a common father were evaluated for evidence of lung disease in association with rheumatologic findings. All underwent routine history and physical examination, hematologic evaluation, and chest radiography and/or CT scan of the chest. Seven children underwent a more extensive immunologic evaluation. Those who were able underwent pulmonary function testing, and four children underwent lung biopsy.

RESULTS

Six of eight children with a common father were found to have radiographic findings consistent with ILD. These children also had evidence of autoimmune disease with joint symptoms, alopecia, rheumatoid factor production, and hypergammaglobulinemia. Open-lung biopsy in four children revealed a spectrum of pulmonary lymphoid proliferations ranging from reactive lymphoid hyperplasia to lymphoid interstitial pneumonia.

CONCLUSION

The findings of ILD and autoimmunity in a kindred of children suggest a novel genetic disorder of autosomal dominant pattern and variable penetrance. Although the precise pathogenesis remains unclear, these cases provide valuable insight into childhood ILD.

Aberrant maturation of mutant perforin underlies the clinical diversity of hemophagocytic lymphohistiocytosis

Missense mutations in perforin, a critical effector of lymphocyte cytotoxicity, lead to a spectrum of diseases, from familial hemophagocytic lymphohistiocytosis to an increased risk of tumorigenesis. Understanding of the impact of mutations has been limited by an inability to express human perforin in vitro. We have shown, for the first time to our knowledge, that recombinant human perforin is expressed, processed appropriately, and functional in rat basophilic leukemia (RBL) cells following retroviral transduction. Subsequently, we have addressed how perforin missense mutations lead to absent perforin detection and impaired cytotoxicity by analyzing 21 missense mutations by flow cytometry, immunohistochemistry, and immunoblot. We identified perforin missense mutations with partial maturation (class 1), no apparent proteolytic maturation (class 2), and no recognizable forms of perforin (class 3). Class 1 mutations exhibit lytic function when expressed in RBL cells and are associated with residual protein detection and variable cytotoxic function in affected individuals, suggesting that carriers of class 1 alleles may exhibit more subtle immune defects. By contrast, class 3 mutations cause severely diminished perforin detection and cytotoxicity, while class 2 mutations have an intermediate phenotype. Thus, the pathologic mechanism of perforin missense mutation likely involves a protein dosage effect of the mature protein.

Pseudoacne of the nasal crease: a new entity?

In this article we describe a clinical entity appearing in seven preadolescent patients who presented with chronic red papules within a prominent nasal crease. Milia were also noted in the nasal crease, but there was no evidence of acne vulgaris. The duration of symptoms was 4 months to 2 years, and lesions ranged from inflamed red papules, which were treated with topical antiinflammatory medications, to scarred white papules requiring excision. Histologic evaluation of two lesions revealed keratin granulomas that were likely derived from ruptured, inflamed milia. Due to its similarity in appearance to acne vulgaris, but different pathogenesis and clinical course, we suggest naming this newly described entity "pseudoacne of the nasal crease."

V75R576 IL-4 receptor alpha is associated with allergic asthma and enhanced IL-4 receptor function

Asthma is a complex polygenic disease. Many studies have implicated the importance of IL-4R alpha in the development of allergic inflammation and its gene has been implicated in the genetics of asthma and atopy. In this study, we examined the functional consequences of two of the human IL-4R alpha allelic variants that have been found to associate with asthma and atopy. We examined the effects of each variant alone and in combination on IL-4-dependent gene induction. We found that neither the Q576R nor the I75V variants affected IL-4-dependent CD23 expression. However, the combination of V75R576 resulted in expression of an IL-4R alpha with enhanced sensitivity to IL-4. We next examined the genetics of five of the known IL-4R alpha allelic variants in asthmatic and nonatopic populations. Strikingly, the association of V75/R576 with atopic asthma was greater than either allele alone and the association of R576 with atopic asthma was dependent on the coexistence of V75. A haplotype analysis revealed a single IL-4R alpha haplotype that was associated with allergic asthma, VACRS, further confirming the importance of the V75 and R576 combination in the genetics of asthma. This is the first report demonstrating that a functional alteration in IL-4R alpha requires the coexistence of two naturally occurring single nucleotide polymorphisms (snps) in combination; neither snp alone is sufficient. These data illustrate the importance of studying snps in combination, because the functional significance of a given snp may only be evident in a specific setting of additional snps in the same or different genes.

Elevated luteinizing hormone in prepubertal transgenic mice causes hyperandrogenemia, precocious puberty, and substantial ovarian pathology

In women, chronically elevated androgens have been associated with polycystic ovarian syndrome and infertility. Recently, we described transgenic mice with elevated serum LH secondary to targeted expression of a transgene encoding a chimeric LH beta-subunit. Mature transgenic females exhibit elevated androgens, anovulation, and a range of ovarian phenotypes including cysts, widespread luteinization, and tumors. In the present study we have examined serum levels of LH and testosterone and the concurrent development of the reproductive system in prepubertal mice. Serum LH in prepubertal females was elevated despite increased serum testosterone and estradiol, indicating a relative insensitivity to steroid negative feedback. Elevated serum LH and hyperandrogenemia resulted in accelerated vaginal opening and ovarian follicular development in transgenic females. Precocious antral follicle formation and conspicuous hypertrophy of the theca-interstitium preceded the development of large cysts with marked hemorrhage. Based on these studies we conclude that chronic prepubertal elevation of serum LH results in gonadotropin-dependent hyperandrogenemia, leading to abnormal sexual development and significant ovarian pathology.

Overexpression of R domain eliminates cAMP-stimulated Cl- secretion in 9/HTEo- cells in culture

The intracellular hydrophilic region of the cystic fibrosis transmembrane conductance regulator (CFTR), the R domain, has been postulated to be a regulator of the Cl-channel. Under basal conditions R blocks the channel, but when phosphorylated, R undergoes conformational change to open the channel. Overexpression of R in 9/HTEo- cells, a human tracheal epithelial cell line with adenosine 3',5' -cyclic monophosphate (cAMP)-regulated Cl- conductance due to CFTR, caused reduced basal Cl- conductance and elimination of its response to isoproterenol, but ionomycin-stimulated Cl- efflux was preserved. Cells which overexpressed R showed no downregulation of endogenous CFTR mRNA and had normal cAMP production and protein kinase A (PKA) activity, so R did not act at these levels. Although the precise mechanism by which R affects CFTR conductance is undetermined, these cell lines could be useful in separating the cell biological consequences of impaired Cl- transport from those of mutant CFTR per se.

Targeted overexpression of luteinizing hormone in transgenic mice leads to infertility, polycystic ovaries, and ovarian tumors

Hypersecretion of luteinizing hormone (LH) is implicated in infertility and miscarriages in women. A lack of animal models has limited progress in determining the mechanisms of LH toxicity. We have recently generated transgenic mice expressing a chimeric LH beta subunit (LH beta) in gonadotropes. The LH beta chimera contains the C-terminal peptide of the human chorionic gonadotropin beta subunit. Addition of this peptide to bovine LH beta resulted in a hormone with a longer half-life. Furthermore, targeted expression of the LH beta chimera led to elevated LH levels and infertility in female transgenics. These mice ovulated infrequently, maintained a prolonged luteal phase, and developed pathologic ovarian changes such as cyst formation, marked enlargement of ovaries, and granulosa cell tumors. Testosterone and estradiol levels were increased compared to nontransgenic littermates. An unusual extragonadal phenotype was also observed: transgenic females developed hydronephropathy and pyelonephritis. The pathology observed demonstrates a direct association between abnormal secretion of LH and infertility and underscores the utility of the transgenic model for studying how excess LH leads to cyst formation, ovarian tumorigenesis, and infertility.