IgE immunotherapy

The importance of antibodies in activating immune responses against tumors is now better appreciated with the emergence of checkpoint blockade antibodies and with engineered antibody Fc domains featuring enhanced capacity to focus potent effector cells against cancer cells. Antibodies designed with Fc regions of the IgE class can confer natural, potent, long-lived immune surveillance in tissues through tenacious engagement of high-affinity cognate Fc receptors on distinct, often tumor-resident immune effector cells, and through ability to activate these cells under tumor-induced Th2-biased conditions. Here, we review the properties that make IgE a contributor to the allergic response and a critical player in the protection against parasites, which also support IgE as a novel anti-cancer modality. We discuss IgE-based active and passive immunotherapeutic approaches in disparate in vitro and in vivo model systems, collectively suggesting the potential of IgE immunotherapies in oncology. Translation toward clinical application is now in progress.     

Cytotoxic T-cells specific for natural IgE peptides downregulate IgE production

Immunoglobulin E (IgE) plays a central role in IgE-mediated immediate type hypersensitivity. Since production of IgE depends on Th2, efforts to block IgE production and control allergic reactions include tolerization of Th2 or deviating development of Th2. We hypothesized that cytotoxic T lymphocytes targeting natural IgE peptides/MHC I complexes can eliminate IgE-producing cells and inhibit centrally IgE production. CTL to self-IgE peptides were elicited in mice immunized with nonameric p109-117, p113-121, and p103-141 (CHepsilon2 domain), which encompass both peptides with an OVA helper peptide (OVAp restricted for H-2d/b) in liposomes and presented by dendritic cells (DC). CTL from BALB/c lysed IgE peptide-pulsed P815 target as well as IgE-producing 26.82 hybridomas (H-2d). Natural tolerance to self-IgE peptides was tested in IgE sufficient (IgE +/+) as well as IgE-deficient (IgE -/-) 129/SvEv mice (H-2b). Comparable magnitude of CTL responses was observed in both strains immunized with p109-117 or p103-141 concomitantly with CD4 T-cell costimulation. CTL from 129/SvEv lysed not only IgE peptide-pulsed EL-4 but also IgE-producing B4 hybridomas (H-2b). This observation strongly suggests a correspondence of epitope of immunogenic peptide to that of physiologically processed IgE peptides presented on IgE-producing cells. Moreover, CTL were generated in 129/SvEv, immunized with the recombinant antigenized antibody in liposomes encompassing p107-123, p109-117, and p113-121 expressed in CDR3 of VH62/human gamma1. Polyclonal IgE production was inhibited by coincubation with MHC I-restricted CTL in vitro. Furthermore, antigen-specific IgE responses were inhibited in mice, immunized with p109-117 and p103-141 while IgG responses were not suppressed. Since IgE peptide sequences of CHepsilon2 are ubiquitous to all murine IgE heavy chain, peptides made as such can serve as a universal IgE vaccine to prevent allergy for a myriad of allergens in rodents. This observation suggests that similar human IgE peptides should be identified and employed to downregulate human IgE production.     

IgE and chemotherapy

The nexus of chemotherapeutic intervention and the immunomodulation of IgE-related phenomena are not well understood. The relationship bears importance in better understanding the causal and/or resultant effects of one on the other and their collective role in the management and sequelae of the cancer patient. This review discusses the relationship of chemotherapy on immunoglobulins with a focus on IgE and other related biological processes including hypersensitivity reactions and proposes models toward effective management of the cancer patient in this regard.     

Mechanisms of IgE homeostasis. Sequestration of IgE by murine type II IgE Fc receptor-bearing B cell hybridomas.

Among all classes of Ig, IgE exhibits the highest rate of fractional catabolism of which the site and mechanisms is not understood. We construct a panel of murine B cell hybridomas to investigate the catabolism of IgE; one of these hybridomas, 17A11, constitutively expresses high levels of type II IgE FcR (Fc epsilon RII, CD23) (Kd:1.77 nM; B max: 1.65 x 10(5], and is capable of clearing receptor-bound IgE. Receptor-mediated endocytosis of IgE ligand ensues after binding monomeric and DNP-BSA:IgE immune complexes, and the binding is inhibited by treating 17A11 with anti-CD23. IgE ligands are sequestered and are not susceptible to acid stripping from the cell surface. The internalized IgE ligands redistributed into acid hydrolase containing high density lysosomal vesicles and were degraded; metabolic inhibitors such as chloroquine and monensin that elevate intracellular pH of 17A11 also prevent entry of IgE ligand into lysosomes. These observations raise the possibility that normal Fc epsilon RII-bearing mature B cells in the circulation and lymphoid tissues may function in sequestration and catabolic turnover of IgE molecules through IgE or IL-4 up-regulated Fc epsilon RII uptake; B cell Fc epsilon RII may perform an important role in determining the short biological half-life of IgE molecules, and contributes to IgE homeostasis.     

IgE peptide-specific CTL inhibit IgE production: a transient IgE suppression model in wild-type and HLA-A2.1 transgenic mice

Effect of IgE peptide-specific CTL on IgE antibody production was studied in mouse models. CTL elicited in B6.A2Kb tg mice against a human IgE peptide nonamer, pWV, lysed human IgE-secreting U266 myeloma cells and inhibit IgE production by these cells. U266 transfected with mouse A2Kb transgene (U266-A2Kb) were optimally lysed by these CTL, because the α3 domain of A2Kb interacts well with the CD8 co-receptors. The CTL generated were more effective in inhibiting IgE production by U266-A2Kb cells than lysing these cells. IgE production by and progression of U266 myeloma were suppressed in B6.A2Kb tg mice rendered tolerant to these cells and vaccinated with pWV along with CpG. We also studied the CTL response elicited in wild-type mice by a mouse nonameric IgE peptide, PI-1, along with CpG. This treatment caused a transient suppression of the IgE response in mice previously sensitized to an antigen. In mice treated with this regimen repeatedly, the IgE response was fully recovered 20 days after each treatment. Notably, while IgE peptide/CpG-treated mice remained unresponsive to antigen challenge in vivo, antigen-specific IgE production can be elicited by antigen in cultured splenocytes from these mice. Moreover, IgE peptide/CpG also inhibited an on-going IgE response, including IgE production by bone marrow cells. Taken together, these observations indicate that a CTL-based IgE peptide vaccine targeting IgE-secreting B/plasma cells may be safely employed as a therapeutic approach for suppressing IgE production.     

Convergent recognition of the IgE binding site on the high-affinity IgE receptor

Two structurally distinct classes of peptides were recently identified by phage display that bind the high-affinity IgE receptor, FcepsilonRI, and block IgE binding and subsequent receptor activation. Both classes adopt highly stable structures in solution, one forming a beta hairpin, with the other forming a helical "zeta" structure. Despite these differences, the two classes bind competitively to the same site on the receptor. Structural analyses of both peptide-receptor complexes by NMR spectroscopy and/or X-ray crystallography reveal that the unrelated peptide scaffolds have nevertheless converged to present a similar three-dimensional surface to interact with FcepsilonRI and that their modes of interaction share a key feature of the IgE-FcepsilonRI complex, the proline/tryptophan sandwich.     

IgE responses in human filariasis. II. Qualitative characterization of filaria-specific IgE

Crossed radioimmunoelectrophoresis (CRIE) was used to characterize human IgE antibody responses to filarial parasites by using antigens derived from Brugia malayi (Bm) adult worms. A reference pool of patient sera was initially used to determine the sensitivity and specificity of CRIE. Because IgG-blocking antibodies interfered with IgE binding in certain sera, all sera were preabsorbed with protein A-Sepharose. As little as 50 ng of specific IgE antibody (determined by quantitative radioallergosorbent test [RAST]) in the reference pool bound to 20 of the 35 antigen precipitates in crossed immunoelectrophoresis. Increasing IgE antibody concentration did not increase the number of IgE-binding precipitates. Six patients from each of the three major clinical groups in lymphatic filariasis (i.e., tropical pulmonary eosinophilia [TE], chronic lymphatic pathology [CP], or circulating microfilaremia [MF]) were studied by CRIE with the use of a constant amount of IgE antibody (50 ng IgE anti-BmA). Distinct patterns of allergen recognition were observed among the groups. Individuals with TE recognized both anodic and cathodic antigens as allergens, whereas the other two groups recognized predominantly anodic antigens. The greatest number of allergens was recognized by patients with TE; this number ranged from nine to 18, whereas patients with CP or circulating MF recognized from six to 11 allergens. Although potentiated IgE responses at a quantitative level in parasitic helminth infections is a well-established phenomenon, our studies showing the diversity of antigens recognized as allergens indicate for the first time potentiated IgE responses at a qualitative level as well.     

Microarrayed allergens for IgE profiling

Diagnosis of type I allergy is based on anamnesis, provocation testing, and serological determination of total and specific IgE. Currently, in vivo and in vitro diagnostic tests employ allergen extracts prepared from various allergen sources (e.g., pollen, mites, animal dander, moulds, foods, venoms, etc.). The application of recombinant DNA technology to the field of allergen characterization has allowed to reveal the molecular nature of the most common allergens. To date a continuously increasing number of allergen sequences has become available and panels of recombinant allergens-assembling the epitope complexity of natural allergens sources-can be produced. The use of recombinant allergens instead of crude, natural extracts for allergy diagnosis allows us to determine the individual IgE reactivity profile of each patient. To enable a comprehensive analysis of the patient's IgE binding pattern to a large number of individual allergens, a new type of serological test is required. In this paper, we applied microarray technology to create a multi-allergen test system, based on microarrayed recombinant allergens.     

Glycoproteomic studies of IgE from a novel hyper IgE syndrome linked to PGM3 mutation

Glycans serve as important regulators of antibody activities and half-lives. IgE is the most heavily glycosylated antibody, but in comparison to other antibodies little is known about its glycan structure function relationships. We therefore describe the site specific IgE glycosylation from a patient with a novel hyper IgE syndrome linked to mutations in PGM3, which is an enzyme involved in synthesizing UDP-GlcNAc, a sugar donor widely required for glycosylation. A two-step method was developed to prepare two IgE samples from less than 1 mL of serum collected from a patient with PGM3 mutation and a patient with atopic dermatitis as a control subject. Then, a glycoproteomic strategy was used to study the site-specific glycosylation. No glycosylation was found at Asn264, whilst high mannose glycans were only detected at Asn275, tri-antennary glycans were exclusively observed at Asn99 and Asn252, and non-fucosylated complex glycans were detected at Asn99. The results showed similar glycosylation profiles between the two IgE samples. These observations, together with previous knowledge of IgE glycosylation, imply that IgE glycosylation is similarly regulated among healthy control, allergy and PGM3 related hyper IgE syndrome.     

Construction of normal human IgE phage antibody library and the screening of the anti—trichosanthin IgE

Allergen specific IgE response is the major cause of immediate hypersensitivity.However the number of IgEproducing B cells and the amount of IgE,especially the specific IgE,are so low,it greatly impedes the study of the allergic-specifc antibody responses.Here we report the construction of a normal human IgE combinatorial library.The repertoire of IgE VH genes and of κ genes were separately amplified from normal human peripheral blood lymphocytes through RT-PCR,and were then constructed to form the phage surface display human Fab(IgEVH) library.A plant protein allergen,trichosanthin(TCS),was used to affinity-enrich and to screen the anti-TCS phage HuFab clones from the library.Human IgE(Fab) to TCS were detected.     

Inhibition of IgE production in B hybridomas by IgE class-specific suppressor factor from T hybridomas

The function of IgE class-specific suppressor factor (IgE-TsF) from T hybridomas was studied by employing IgE-producing B hybridomas. IgE-TsF was obtained from IgE class-specific T hybridomas, which had been established by the fusion of a phosphorylcholine-conjugated Mycobacterium-primed T cell population with the T lymphoma cell line BW5147. The absorption experiments showed that IgE-TsF from T hybridomas was composed of the binding site(s) for IgE and I region gene products as observed in conventional IgE-TsF. Incubation of IgE-producing B hybridomas with IgE-TsF for 1 hr at 37 degrees C resulted in the reduction of the number of IgE-secreting cells when assessed by a reverse plaque assay. The proportions of surface IgE-positive cells were concomitantly reduced. After 24 hr incubation with IgE-TsF, the number of cytoplasmic IgE-positive cells was reduced, showing that IgE synthesis was inhibited by IgE-TsF. Antigen-specific TsF from phosphorylcholine-specific T hybridomas did not show any inhibitory effect, and IgE-TsF did not block the antibody production of IgM-producing B hybridomas. Precapping of IgE receptors by anti-epsilon antibody or the simultaneous addition of soluble IgE with IgE-TsF abrogated the suppressive function, suggesting that IgE-TsF acted directly on B epsilon cells through binding with IgE receptors.     

Quantitation of serum IgE by using chimeras of human IgE receptor and avian immunoglobulin domains

Anti-IgE therapeutics represent an efficient approach in the management of IgE-mediated allergic asthma. However, monitoring the reduction of IgE levels into a therapeutically efficient range requires the determination of residual serum IgE. We established an analytical approach to distinguish free and anti-IgE complexed serum IgE based on soluble derivatives of the human high-affinity IgE receptor. Soluble receptor derivatives represent an ideal means to analyze receptor antagonism by any ligand or blocking antibody. Therefore, the FcεRI ectodomain was fused with avian IgY constant domains that circumvent susceptibility to interference phenomena and improve assay performance. After production in HEK293 cells, subsequent characterization by enzyme-linked immunosorbent assay and immunoblotting confirmed the suitability of avian IgY constant domains for immobilization and detection purposes. To provide further insights into the different IgE reactivities, free allergen-specific IgE was also determined. Monitoring of sera from omalizumab-treated patients during the course of therapy revealed the applicability for assessment of omalizumab-complexed versus noncomplexed serum IgE. These parameters may allow correlation to clinical responses during anti-IgE therapy with the perspective of biomonitoring.     

B1 Cell IgE Impedes Mast Cell-Mediated Enhancement of Parasite Expulsion through B2 IgE Blockade

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