Activated phosphoinositide 3-kinase δ syndrome: Update from the ESID Registry and comparison with other autoimmune-lymphoproliferative inborn errors of immunity

BACKGROUND

Activated phosphoinositide-3-kinase δ syndrome (APDS) is an inborn error of immunity (IEI) with infection susceptibility and immune dysregulation, clinically overlapping with other conditions. Management depends on disease evolution, but predictors of severe disease are lacking.

OBJECTIVES

This study sought to report the extended spectrum of disease manifestations in APDS1 versus APDS2; compare these to CTLA4 deficiency, NFKB1 deficiency, and STAT3 gain-of-function (GOF) disease; and identify predictors of severity in APDS.

METHODS

Data was collected from the ESID (European Society for Immunodeficiencies)-APDS registry and was compared with published cohorts of the other IEIs.

RESULTS

The analysis of 170 patients with APDS outlines high penetrance and early onset of APDS compared to the other IEIs. The large clinical heterogeneity even in individuals with the same PIK3CD variant E1021K illustrates how poorly the genotype predicts the disease phenotype and course. The high clinical overlap between APDS and the other investigated IEIs suggests relevant pathophysiological convergence of the affected pathways. Preferentially affected organ systems indicate specific pathophysiology: bronchiectasis is typical of APDS1; interstitial lung disease and enteropathy are more common in STAT3 GOF and CTLA4 deficiency. Endocrinopathies are most frequent in STAT3 GOF, but growth impairment is also common, particularly in APDS2. Early clinical presentation is a risk factor for severe disease in APDS.

CONCLUSIONS

APDS illustrates how a single genetic variant can result in a diverse autoimmune-lymphoproliferative phenotype. Overlap with other IEIs is substantial. Some specific features distinguish APDS1 from APDS2. Early onset is a risk factor for severe disease course calling for specific treatment studies in younger patients.

OS03.4.A In vivo dynamics and anti-tumor effects of EpCAM-directed CAR T-cells against brain metastases from lung cancer

Background

Lung cancer patients are at a particularly high risk for brain metastases, and a considerable number of affected patients succumb due to their intracranial disease. Chimeric Antigen Receptor (CAR) T-cells emerged as a powerful class of cell-based immunotherapy for hematological malignancies. However, it remains unclear whether CAR T-cells also represent a safe and effective therapeutic option for brain metastases.

Material and Methods

A fully syngeneic orthotopic cerebral metastasis model in mice was established by combining a chronic cranial window with repetitive intracerebral two-photon laser scanning microscopy. This approach enabled the in vivo characterization of red fluorescent CAR T-cells and tumor cells on a single-cell level over weeks. Intraparenchymal injection of Lewis lung carcinoma cells (expressing the tumor cell-antigen EpCAM) was performed, and CAR T-cells directed against EpCAM (EpCAMCAR T-cells) were injected into the adjacent brain parenchyma after solid brain tumors have formed.

Results

All mice had visible tumor take four days after the intracranial tumor cell injection, and rapid growth of solitary lesions was seen in the following days. No toxicities mediated by intracranially injected EpCAMCAR T-cells were encountered. In mice treated with EpCAMCAR T-cells, we initially observed substantial CAR T-cell accumulation within the tumor compared to controls (median number: 1700 versus 939 cells/mm2; p = 0.007). This was paralleled by lower velocities of EpCAMCAR T-cells, characterizing T-cell receptor (TCR)-mediated antitumor cytotoxicity due to long-lasting contacts between effector immune cells and tumor cells. Consequently, treatment with EpCAMCAR T-cells resulted in reduced tumorous growth as determined per in vivo microscopy (median tumor area on day 10: 1.8 versus 10.8 mm2; p = 0.001) and immunohistochemistry of excised brains (median tumor volume on day 10: 3.6 versus 33.2 mm3; p = 0.001). However, the number of EpCAM-directed CAR T-cells within the tumor markedly decreased during the observation period, pointing towards insufficient persistence of EpCAM-directed CAR T-cells. In line with these findings, survival was prolonged in mice receiving EpCAMCAR T-cells but long-lasting remission was rare (median survival: 15 versus 13 days; p = 0.012).

Conclusion

Our findings indicate that CAR T-cells injected into the cerebral parenchyma may induce relevant anti-tumor effects in brain metastases from lung cancer. Due to the translational nature of our study, prospective clinical cohorts appear warranted. Strategies improving the intratumoral persistence of CAR T-cells in brain metastases may be utilized to further boost the success of such promising therapy.

Characterization of the clinical and immunologic phenotype and management of 157 individuals with 56 distinct heterozygous NFKB1 mutations

BACKGROUND

An increasing number of NFKB1 variants are being identified in patients with heterogeneous immunologic phenotypes.

OBJECTIVE

To characterize the clinical and cellular phenotype as well as the management of patients with heterozygous NFKB1 mutations.

METHODS

In a worldwide collaborative effort, we evaluated 231 individuals harboring 105 distinct heterozygous NFKB1 variants. To provide evidence for pathogenicity, each variant was assessed in silico; in addition, 32 variants were assessed by functional in vitro testing of nuclear factor of kappa light polypeptide gene enhancer in B cells (NF-κB) signaling.

RESULTS

We classified 56 of the 105 distinct NFKB1 variants in 157 individuals from 68 unrelated families as pathogenic. Incomplete clinical penetrance (70%) and age-dependent severity of NFKB1-related phenotypes were observed. The phenotype included hypogammaglobulinemia (88.9%), reduced switched memory B cells (60.3%), and respiratory (83%) and gastrointestinal (28.6%) infections, thus characterizing the disorder as primary immunodeficiency. However, the high frequency of autoimmunity (57.4%), lymphoproliferation (52.4%), noninfectious enteropathy (23.1%), opportunistic infections (15.7%), autoinflammation (29.6%), and malignancy (16.8%) identified NF-κB1-related disease as an inborn error of immunity with immune dysregulation, rather than a mere primary immunodeficiency. Current treatment includes immunoglobulin replacement and immunosuppressive agents.

CONCLUSIONS

We present a comprehensive clinical overview of the NF-κB1-related phenotype, which includes immunodeficiency, autoimmunity, autoinflammation, and cancer. Because of its multisystem involvement, clinicians from each and every medical discipline need to be made aware of this autosomal-dominant disease. Hematopoietic stem cell transplantation and NF-κB1 pathway-targeted therapeutic strategies should be considered in the future.

Clinical and Laboratory Features of 184 Italian Pediatric Patients Affected with Selective IgA Deficiency (SIgAD): a Longitudinal Single-Center Study

PURPOSE

Selective IgA deficiency (SIgAD) is the most common humoral primary immunodeficiency. Long-term follow-up data in large cohort of pediatric patients are scarce.

METHODS

We report on a single-center cohort of 184 pediatric patients affected with selective IgA deficiency and describe the characteristics at diagnosis and during follow-up.

RESULTS

Respiratory infections were the most common clinical finding leading to the initial diagnosis (62%). Positive family history for antibody deficiencies (selective IgA deficiency, common variable immunodeficiency) led to SIgAD diagnosis in 16% of cases. During follow-up, while the incidence of respiratory infections was not particularly high, gastrointestinal symptoms were reported in 27% of patients. Allergic manifestations were found in 23% at diagnosis and an additional 16% of patients during follow-up, leading to a prevalence of atopy of 39% among SIgAD patients. Autoimmune manifestations, excluding celiac disease, were found in 9% of affected patients during follow-up. Celiac disease was found in a high prevalence (14%). Increase of serum IgA levels to partial deficiency (9%) and normal serum levels for age (4%) was observed during follow-up. A small percentage of patients (2%) progressed to common variable immunodeficiency (CVID).

CONCLUSIONS

In conclusion, this is the first study to describe a large single-center pediatric cohort of patients affected with SIgAD, revealing that overall most patients do well with regard to infections. Many develop CD, at a rate much higher than the general population. A few normalize their IgA levels. A few progress to CVID. Thus, careful follow-up is suggested to diagnose and treat potential complications earlier for avoiding potential morbidities.

Early B cell developmental impairment with progressive B cell deficiency in NFKB2 mutated CVID disease without autoimmunity

This study provides evidence for a novel role for NFKB2 in human B cell development in the bone marrow and in the periphery, leading to progressive peripheral B cell deficiency not always combined with autoimmune phenomena, broadening thus the clinical spectrum of NFKB2 mutated CVID disease and implying an essential role for NFKB2 in early human B cell development.

Vaccination in immunocompromised host: Recommendations of Italian Primary Immunodeficiency Network Centers (IPINET)

Infectious complications are a major cause of morbidity and mortality in patients with primary or secondary immunodeficiency. Prevention of infectious diseases by vaccines is among the most effective healthcare measures mainly for these subjects. However immunocompromised people vary in their degree of immunosuppression and susceptibility to infection and, therefore, represent a heterogeneous population with regard to immunization. To date there is no well- established evidence for use of vaccines in immunodeficient patients, and indications are not clearly defined even in high-quality reviews and in most of the guidelines prepared to provide recommendations for the active vaccination of immunocompromised hosts. The aim of this document is to issue recommendations based on published literature and the collective experience of the Italian primary immunodeficiency centers, about how and when vaccines can be used in immunocompromised patients, in order to facilitate physician decisions and to ensure the best immune protection with the lowest risk to the health of the patient.

[Biological risk in non-clinical biological and chemical laboratories]

The D.Lgs 626/94, regarding the improvement of workers safety in the workplace, introduces the necessity of the biological hazards assessment. In case of not sanitary chemical and biological laboratories, workers are subject to biological hazards due to potential exposure, because many biological agents could be present in the samples to be analysed, and also for deliberated use of micro organisms. However the assessment of the air and surfaces monitoring results in such environment is still difficult without Guidelines that indicate levels of acceptable exposure and contamination, and reference limits in order to judge "safe" the environment. The following report describes a microbiological monitoring into the Laboratories of HERA SpA and wants to underline the need to produce Guidelines dedicated to these particular workplaces environment, in order to standardize air quality sampling procedures and results assessment.

Homodimerization of erythropoietin receptor by a bivalent monoclonal antibody triggers cell proliferation and differentiation of erythroid precursors

Erythropoietin (EPO) stimulates proliferation and differentiation of erythroid progenitor cells. Several lines of evidence indicate that the most likely mechanism of EPO receptor (EPO-R) activation by EPO is homodimerization of the receptor on the surface of erythrocyte precursors. Therefore, we argued that it should be possible to raise EPO-R monoclonal antibodies (MoAbs) that would activate the receptor by dimerization and thus mimic EPO action. We have identified such an agonist MoAb (MoAb34) directed against the extracellular EPO binding domain of the EPO-R. This bivalent IgG antibody triggers the proliferation of EPO-dependent cell lines and induces differentiation of erythroid precursors in vitro. In contrast, the monovalent Fab fragment, which cannot dimerize the receptor, is completely inactive. The mechanism of receptor activation by homodimerization implies that at high ligand concentrations the formation of 1:1 receptor/ligand complexes is favored over 2:1 complexes, thereby turning the ligand agonist into an antagonist. Thus, EPO and MoAb34 should self-antagonize at high concentrations in both cell proliferation and differentiation assays. Our data indeed demonstrate that EPO and MoAb34 antagonize ligand-dependent cell proliferation with IC50 values of approximately 20 and 2 mumol/L, respectively. Erythroid colony formation (BFUe) is inhibited at MoAb34 concentrations above 1 mumol/L. Furthermore, we analyzed the MoAb34:EPO-R interaction using a mathematic model describing antibody-mediated receptor dimerization. The data for proliferation and differentiation activity were consistent with the receptor dimer formation on the cell surface predicted by the model.

Mapping of the active site of recombinant human erythropoietin

Recombinant human erythropoietin (rHuEPO) variants have been constructed to identify amino acid residues important for biological activity. Immunoassays were used to determine the effect of each mutation on rHuEPO folding. With this strategy, we could distinguish between mutations that affected bioactivity directly and those that affected bioactivity because the mutation altered rHuEPO conformation. Four regions were found to be important for bioactivity: amino acids 11 to 15, 44 to 51, 100 to 108, and 147 to 151. EPO variants could be divided into two groups according to the differential effects on EPO receptor binding activity and in vitro biologic activity. This suggests that rHuEPO has two separate receptor binding sites. Mutations in basic residues reduced the biologic activity, whereas mutations in acidic residues did not. This suggests that electrostatic interactions between rHuEPO and the human EPO receptor may involve positive charges on rHuEPO.

Activation of the erythropoietin (EPO) receptor by bivalent anti-EPO receptor antibodies

Oligomerization of cytokine receptors including the erythropoietin (EPO) receptor has been advanced as a model for activation. If homodimerization of the EPO receptor activates it, then bivalent antibodies raised to the extracellular domain of the EPO receptor should also homodimerize and activate. Mouse monoclonal antibodies (IgG) raised to the soluble, extracellular domain of the human EPO receptor (EPOR) were found that would stimulate thymidine uptake of an human EPO-dependent cell line, UT-7/EPO. Dose response curves showed bell shapes where activity was low at low and high concentrations. Monovalent (Fab) fragments bound to the receptor but did not stimulate thymidine uptake, which indicates that two antibody binding sites are required for activation. The anti-EPOR antibodies stimulated the formation of burst forming unit erythroid colonies from human CD34(+) cells purified from peripheral blood. This indicates that homodimerization of the EPO receptor by anti-EPOR antibodies is sufficient for both proliferation and differentiation of erythroid progenitor cells and that the constraints on dimerization necessary for activation are rather loose.

Isolation and characterization of conformation sensitive antierythropoietin monoclonal antibodies: effect of disulfide bonds and carbohydrate on recombinant human erythropoietin structure

We have isolated and characterized three anti-recombinant human erythropoietin (rHuEPO) monoclonal antibodies (MoAbs) that recognize nonoverlapping epitopes on rHuEPO. Anti-EPO MoAb D11 neutralizes rHuEPO activity whereas MoAbs F12 and 9G8A do not. This suggests that D11 may bind to the rHuEPO active site. MoAbs F12 and D11 recognize conformation dependent epitopes whereas 9G8A does not. Immunoassays were developed for each monoclonal. The 9G8A immunoassay was novel and useful because immunoreactivity increased when rHuEPO was denatured. Disruption of disulfide bonds or removal of carbohydrate increased 9G8A immunoreactivity, which suggests that these elements are important for rHuEPO structure or stability.

Fine-structure epitope mapping of antierythropoietin monoclonal antibodies reveals a model of recombinant human erythropoietin structure

We have isolated and mapped the rHuEPO epitopes for three noncompeting anti-EPO monoclonal antibodies (MoAbs). The MoAb 9G8A recognizes a linear epitope that includes amino acids 13, 16, and 17. MoAb F12 recognizes a conformational epitope that includes amino acids 31 through 33, 86 through 91, and 138. MoAb D11 recognizes a conformational epitope that includes amino acids 64 through 78 and 99 through 110. MoAb D11 neutralizes rHuEPO activity which suggests that its epitope may contain the receptor binding domain. Analysis of the effect of mutations on folding allowed the identification of buried residues, alpha-helical, and non alpha-helical regions. This data along with epitope mapping data of anti rHuEPO monoclonals was used to model rHuEPO protein structure. A model consistent with the data is a 4-helix bundle with short and long interconnecting loops.

Structural requirements for addition of O-linked carbohydrate to recombinant erythropoietin

To define the structural requirements for addition of O-linked glycosylation in vivo, recombinant erythropoietin (rEPO) variants were constructed. Thirty-three independent Ser or Thr substitutions were constructed and examined to see which were subject to O-linked carbohydrate addition. Variants with Thr mutations at positions 123 and 125, but not elsewhere, contained additional carbohydrate, which suggests that several positions around the existing O-linked glycosylation site (Ser126), but not elsewhere, contain the necessary information for O-linked carbohydrate addition. Two forms of the Thr125 variant were identified. One form was glycosylated only at residue 125, and a second form was glycosylated at both Thr125 and Ser126, the normal O-glycosylation site. We have also found that glycosylation is less efficient when rEPO is improperly folded and that prolines at -1 and +1 relative to the O-glycosylation site enhance glycosylation.

Role of glycosylation on the secretion and biological activity of erythropoietin

The erythropoietin (EPO) molecule contains four carbohydrate chains. Three contain N-linkages to asparagines at positions 24, 38, and 83, and one contains an O-linkage to a serine at position 126. We constructed human EPO variants that eliminated the three N-glycosylation sites by replacing the asparagines with glutamines singly or in combination. The O-linked carbohydrate chain was removed by replacing the serine with glutamine, valine, histidine, or alanine. A variant with a double mutation (Gln38,83) and another with a triple mutation (Gln24,38,83) were secreted poorly from COS1 and CHO cells even though RNA encoding these variants was present. All other variants with mutations in N-linked glycosylation sites were secreted normally. Removal of any of the N-glycosylation sites reduced the in vivo but not the in vitro biological activity of the EPO molecule. All the mutations at Ser126, the O-glycosylation site, were secreted normally. In vitro activity was also unaffected except for Ala126 which had a 50-fold decrease. The Val126 variant was tested in vivo, and its specific activity was only slightly less than that of the native EPO, which indicates that the O-linked carbohydrate is not essential for activity.