10th European immunogenicity platform open symposium on immunogenicity of biopharmaceuticals.

Therapeutic proteins and emerging gene and cell-based therapies are attractive therapeutic tools for addressing unmet medical needs or when earlier conventional treatment approaches failed. However, the development of an immune response directed against therapeutic agents is a significant concern as it occurs in a substantial number of cases across products and indications. The specific anti-drug antibodies that develop can lead to safety adverse events as well as inhibition of drug activity or accelerated clearance, both phenomena resulting in loss of treatment efficacy. The European Immunogenicity Platform (EIP) is a meeting place for experts and newcomers to the immunogenicity field, designed to stimulate discussion amongst scientists across industry and academia, encourage interactions with regulatory agencies and share knowledge and the state-of-the-art of immunogenicity sciences with the broader scientific community. Here we report on the main topics covered during the EIP 10th Open Symposium on Immunogenicity of Biopharmaceuticals held in Lisbon, 26-27 February 2019, and the 1-d training course on practical and regulatory aspects of immunogenicity held ahead of the conference. These main topics included immunogenicity testing, clinical relevance of immunogenicity, immunogenicity prediction, regulatory aspects, tolerance induction as a mean to mitigate immunogenicity and immunogenicity in the context of gene therapy.

Anti-inflammatory activity of sublingual immunoglobulin (SLIG) in a murine model of allergen-driven airway inflammation.

AIM: Intravenous immunoglobulin (IVIG) displays anti-inflammatory activities in many diseases. Subcutaneous administration of anti-IgE in humans provides benefit in severe persistent allergic asthma. Given the well established efficacy of sublingual allergen immunotherapy in respiratory type I allergies, we investigated the therapeutic potential of sublingual immunoglobulin (SLIG), most particularly anti-IgE SLIG, in a murine model of allergen-driven airway inflammation. METHODS: BALB/c mice sensitized with ovalbumin (OVA) were treated sublingually with rat monoclonal IgG1 or IgG2a, either directed to mouse IgE or with no reported specificity. Airway hyperresponsiveness (AHR) was assessed by whole body plethysmography, and eosinophil infiltrates were characterized in bronchial alveolar lavages (BAL). OVA-specific antibody and T cell responses were analyzed in sera and saliva or lung and draining lymph nodes, by ELISA or CBA measurement of cytokine production, respectively. RESULTS: AHR and BAL eosinophil infiltrates were substantially decreased in mice treated sublingually with particulate OVA (positive control), as well as in animals receiving various rat IgG1, irrespective of their specificity for murine IgE. In contrast, no improvement was observed in mice treated with PBS (negative control) or various rat IgG2a. SLIG anti-inflammatory activity is not related to a downregulation of Th2, Th17 or an induction of Foxp3(+) CD4(+) regulatory T cell responses. Mass spectrometry analysis of glycan moieties, such as sialic acid, suggests that the differential efficacy of rat IgG1 and IgG2a is not related to their capacity to interact with lectins borne by oral immune cells. CONCLUSIONS: In a murine model of allergen-driven airway inflammation, SLIG exhibits an anti-inflammatory activity irrespective of the immunoglobulin specificity, and in the absence of allergen. As a noninvasive approach, SLIG deserves to be further studied as a treatment for other inflammatory diseases beyond allergic asthma.

Evaluation of therapeutic sublingual vaccines in a murine model of chronic house dust mite allergic airway inflammation.

BACKGROUND: Second generation therapeutic vaccines based upon recombinant allergens or natural extracts, potentially formulated in vector systems or adjuvants, are being developed. To this aim, preclinical studies in relevant animal models are needed to select proper allergens, formulations and administration schemes. OBJECTIVE: To develop a chronic house dust mite (HDM) allergy model to evaluate sublingual therapeutic vaccine candidates. METHODS: The BABL/c mice that were used were sensitized with Dermatophagoides pteronyssinus (Dpte) and Dermatophagoides farinae (Dfar) mite extracts by intraperitoneal injections followed by aerosol exposures. Animals subsequently underwent sublingual immunotherapy (SLIT) with either Dpte, Dfar or Dpte/Dfar extracts, twice a week for 8 weeks. SLIT efficacy was assessed by whole body plethysmography, lung histology and broncho-alveolar lavages cell counts. Specific T cell and antibody responses to major and minor HDM allergens were monitored in tissues and serum/saliva, respectively. RESULTS: Mice sensitized to Dpte and Dfar allergens exhibited strong airway hyperresponsiveness (AHR) and lung inflammatory infiltrates including eosinophils. Sensitized animals mounted Th2-biased cellular and humoral responses specific for group 1 and 2 major allergens, as well as group 5, 7 and 10 minor allergens. This phenotype was sustained for at least 2 months, allowing the evaluation of immunotherapeutic protocols with HDM extracts-based vaccines. In this model, SLIT decreased AHR and Th2 responses and induced HDM-specific IgAs in saliva. The Dpte/Dfar mix proved the most efficacious when compared to Dpte or Dfar extracts alone. CONCLUSIONS AND CLINICAL RELEVANCE: The efficacy of a sublingual vaccine based on a Dpte/Dfar allergen extract mix was demonstrated in a well standardized murine model of chronic allergic airway inflammation based on clinically relevant mite allergens. The latter will be used as a benchmark for evaluation of future vaccines, including recombinant allergens. This HDM allergic airway inflammation animal model is a useful tool to design and select candidate vaccines to be tested in humans.

Oral macrophage-like cells play a key role in tolerance induction following sublingual immunotherapy of asthmatic mice.

Sublingual allergen-specific immunotherapy (SLIT) is a safe and efficacious treatment for type 1 respiratory allergies. Herein, we investigated the key subset(s) of antigen-presenting cells (APCs) involved in antigen/allergen capture and tolerance induction during SLIT. Following sublingual administration, fluorochrome-labeled ovalbumin (OVA) is predominantly captured by oral CD11b⁺CD11c⁻ cells that migrate to cervical lymph nodes (CLNs) and present the antigen to naive CD4⁺ T cells. Conditional depletion with diphtheria toxin of CD11b⁺, but not CD11c⁺ cells, in oral tissues impairs CD4⁺ T-cell priming in CLNs. In mice with established asthma to OVA, specific targeting of the antigen to oral CD11b⁺ cells using the adenylate cyclase vector system reduces airway hyperresponsiveness (AHR), eosinophil recruitment in bronchoalveolar lavages (BALs), and specific Th2 responses in CLNs and lungs. Oral CD11b⁺CD11c⁻ cells resemble tolerogenic macrophages found in the lamina propria (LP) of the small intestine in that they express the mannose receptor CD206, as well as class-2 retinaldehyde dehydrogenase (RALDH2), and they support the differentiation of interferon-γ/interleukin-10 (IFNγ/IL-10)-producing Foxp3⁺ CD4⁺ regulatory T cells. Thus, among the various APC subsets present in oral tissues of mice, macrophage-like cells play a key role in tolerance induction following SLIT.

Mapping of the lingual immune system reveals the presence of both regulatory and effector CD4+ T cells.

BACKGROUND: Sublingual immunotherapy (SLIT) is safe and reduces both symptoms and medication requirements in patients with type I respiratory allergies. Nonetheless, immune mechanisms underlying SLIT need to be further documented. OBJECTIVE: A detailed characterization of the lingual immune system was undertaken in mice, to investigate the presence of tolerogenic and pro-inflammatory mechanisms. METHODS: Immune cells were characterized in lingual tissues from BALB/c mice using immunohistology and flow cytometry. Resident CD4(+) T cells were sorted and toll-like receptor (TLR) expression profiles as well as functional characterization were assessed by RT-PCR, T cell suppressive assays and cytokine gene expression, respectively. RESULTS: Eosinophils and mast cells were only detected in submucosal tissues. No NK, NK-T, gamma/delta, CD8(+) T cells, nor B-lymphocytes were detected. Potential antigen presenting cells include various subsets of dendritic cells (CD207(+) Langerhans cells, CD11b(+)CD11c(+) myeloid cells and 120G8(+) plasmacytoid DCs) together with F4/80(+) macrophages. Noteworthy, both CD103(-) and CD103(+) CD4(+) T cells expressing TLR2 and TLR4 receptors are present along the lamina propria, in vicinity of myeloid CD11b(+)CD11c(+/-) dendritic cells. Such resident lingual CD4(+) T lymphocytes comprise both suppressive T cells as well as cells with memory/effector functions (i.e. expressing IFN gamma, IL4, IL10 and IL17 genes following stimulation), irrespective of the presence of the mucosal addressing marker CD103. CONCLUSION: The sublingual route is pertinent to induce antigen-specific tolerance, due to (i) limited numbers of pro-inflammatory cells, rather located in submucosal tissues, (ii) co-localization of APCs and resident CD4(+) T cells with regulatory functions. Since the oral immune system can also elicit pro-inflammatory effector responses, the cytokine milieu in which allergens are presented by sublingual APCs needs to be controlled during immunotherapy (e.g. with adjuvants) in order to favour tolerance over inflammation.

Targeting the allergen to oral dendritic cells with mucoadhesive chitosan particles enhances tolerance induction.

BACKGROUND: Sublingual immunotherapy (SLIT) efficacy could be improved by formulations facilitating allergen contact with the oral mucosa and uptake by antigen-presenting cells (APCs). METHODS: Two types of chitosan microparticles, differing in size and surface charge, were tested in vitro for their capacity to improve antigen uptake and presentation by murine bone marrow-derived dendritic cells (BMDCs) or purified oral APCs. T-cell priming in cervical lymph nodes (LNs) was assessed by intravenous transfer of carboxyfluorescein diacetate succinimidyl ester-labelled ovalbumin (OVA)-specific CD4+ T cells and flow cytometry analysis. Ovalbumin-sensitized BALB/c mice were treated sublingually with soluble or chitosan-formulated OVA twice a week for 2 months. Airway hyperresponsiveness (AHR), lung inflammation and T-cell responses in cervical and mediastinal LNs were assessed by whole-body plethysmography, lung histology and Cytometric Bead Array technology, respectively. RESULTS: Only a mucoadhesive (i.e. highly positively charged) and microparticulate form of chitosan enhances OVA uptake, processing and presentation by murine BMDCs and oral APCs. Targeting OVA to dendritic cells with this formulation increases specific T-cell proliferation and IFN-gamma/IL-10 secretion in vitro, as well as T-cell priming in cervical LNs in vivo. Sublingual administration of such chitosan-formulated OVA particles enhances tolerance induction in mice with established asthma, with a dramatic reduction of both AHR, lung inflammation, eosinophil numbers in bronchoalveolar lavages, as well as antigen-specific Th2 responses in mediastinal LNs. CONCLUSIONS: Mucoadhesive chitosan microparticles represent a valid formulation for sublingual allergy vaccines.

Respiratory syncytial virus infection provokes airway remodelling in allergen-exposed mice in absence of prior allergen sensitization.

BACKGROUND: The mechanisms underlying exacerbation of asthma induced by respiratory syncytial virus (RSV) infection have been extensively studied in human and animal models. However, most of these studies focused on acute inflammation and little is known of its long-term consequences on remodelling of the airway tissue. OBJECTIVE: The aim of the study was to use a murine model of prolonged allergen-induced airway inflammation to investigate the effect of RSV infection on allergic airway inflammation and tissue remodelling. METHODS: We subjected mice to RSV infection before or during the chronic phase of airway challenges with OVA and compared parameters of airway inflammation and remodelling at the end-point of the prolonged allergen-induced airway inflammation protocol. RESULTS: RSV infection did not affect the severity of airway inflammation in any of the groups studied. However, RSV infection provoked airway remodelling in non-sensitized, allergen-challenged mice that did not otherwise develop any of the features of allergic airways disease. Increased collagen synthesis in the lung and thickening of the bronchial basal membrane was observed in non-sensitized allergen-challenged mice only after prior RSV infection. In addition, fibroblast growth factor (FGF)-2 but not TGF-beta(1) was increased in this group following RSV infection. CONCLUSION: Our data show for the first time that RSV infection can prime the lung of mice that are not previously systemically sensitized, to develop airway remodelling in response to allergen upon sole exposure via the airways. Moreover, our results implicate RSV-induced FGF-2 in the remodelling process in vivo.

Identification of HER-2/neu immunogenic epitopes presented by renal cell carcinoma and other human epithelial tumors.

HER-2/neu is a tumor-associated antigen overexpressed in a large variety of human tumors. Eight HER-2/neu peptides displaying HLA-A*0201 anchoring motifs were selected and tested for their binding affinity to HLA-A*0201 and their capacity to elicit cytotoxic T lymphocyte (CTL) responses in both HLA-A*0201 transgenic mice and in HLA-A*0201(+) healthy donors. Two high-affinity (p5 and p48) and one intermediate-affinity (p1023) peptides triggered CTL responses in both transgenic mice and humans, comparable to those observed for the well-known HER2/neu dominant peptide p369. CTL induced in transgenic mice lysed HLA-A*0201(+) RMA cells infected with recombinant HER-2/neu but not cells infected with wild-type vaccinia virus. Human CTL lysed HLA-A*0201(+) HER-2/neu(+) tumor cells of different origins (breast, colon, lung and renal cancer) irrespective of the expression levels of HER-2/neu. Importantly, primed CTL specific for these epitopes were detected in freshly isolated tumor-infiltrating lymphocytes from three renal cell carcinoma patients. Therefore, the HER-2/neu peptides p5, p48 and p1023 may be good candidates for immunotherapy of a broad spectrum of tumors, including renal cell carcinoma.

Design of a polyepitope construct for the induction of HLA-A0201-restricted HIV 1-specific CTL responses using HLA-A*0201 transgenic, H-2 class I KO mice.

HLA-A*0201 transgenic, H-2D(b)/mouse beta2-microglobulin double-knockout mice were used to compare and optimize the immunogenic potential of 17HIV 1-derived,HLA-A0201-restricted epitopic peptides. A tyrosine substitution in position 1 of the epitopic peptides, which increases both their affinity for and their HLA-A0201 molecule stabilizing capacity, was introduced in a significant proportion, having verified that such modifications enhance their immunogenicity in respect of their natural antigenicity. Based on these results, a 13-polyepitope construct was inserted in the pre-S2 segment of the hepatitis B middle glycoprotein and used for DNA immunization. Long-lasting CTL responses against most of the inserted epitopes could be elicited simultaneously in a single animal with cross-recognition in several cases of their most common natural variants.

A general strategy to enhance immunogenicity of low-affinity HLA-A2. 1-associated peptides: implication in the identification of cryptic tumor epitopes.

Low-affinity MHC class I-associated cryptic epitopes derived from self proteins overexpressed in a wide variety of human tumors or derived from antigens of viruses exhibiting a high mutation rate, could be interesting candidates for tumor and virus immunotherapy, respectively. However, identification of low-affinity MHC-associated epitopes comes up against their poor immunogenicity. Here we describe an approach that enhances immunogenicity of nonimmunogenic low-affinity HLA-A2.1-binding peptides. It consists of modifying their sequence by introducing a tyrosine in the first position (P1Y). P1Y substitution enhances affinity of HLA-A2.1-associated peptides without altering their antigenic specificity. In fact, P1Y variants of ten nonimmunogenic low-affinity peptides exhibited a 2.3- to 55-fold higher binding affinity and/or stabilized the HLA-A2.1 for at least 2 h more than the corresponding native peptides. More importantly, P1Y variants efficiently triggered in vivo native peptide-specific CTL which also recognized the corresponding naturally processed epitope. The possibility for generating CTL against any low-affinity HLA-A2.1-associated peptide provides us with the necessary tool for the identification of cryptic tumor and virus epitopes which could be used for peptide-based immunotherapy.

Allo-major histocompatibility complex-restricted cytotoxic T lymphocytes engraft in bone marrow transplant recipients without causing graft-versus-host disease.

Previous experiments in humans and mice have shown that allogeneic donors can serve as a source of cytotoxic T lymphocytes (CTL) specific for proteins, such as cyclin-D1 and mdm-2, expressed at elevated levels in tumor cells. In vitro, allo-major histocompatibility complex (MHC)-restricted CTL against these proteins selectively killed allogeneic tumor cells, including lymphoma, but not normal control cells. This suggested that these CTL may be useful for adoptive tumor immunotherapy, provided that they (1) survive in MHC-disparate hosts, (2) maintain their killing specificity, and (3) do not attack normal host tissues. Here, we used cloned allo-restricted CTL isolated from BALB/c mice (H-2(d)) that killed H-2(b)-derived tumor cells expressing elevated levels of the mdm-2 target protein. When these CTL were injected into bone marrow transplanted (BMT) C57BL/6 (H-2(b)) recipients, they consistently engrafted and were detectable in lymphoid tissues and in the bone marrow (BM). Long-term survival was most efficient in spleen and lymph nodes, where CTL were found up to 14 weeks after injection. The administration of CTL did not cause graft-versus-host disease (GVHD) normally associated with injection of allogeneic T cells. These data show that allo-restricted CTL clones are promising reagents for antigen-specific immunotherapy in BMT hosts, because they engraft and retain their specific killing activity without causing GVHD.

H-2 class I knockout, HLA-A2.1-transgenic mice: a versatile animal model for preclinical evaluation of antitumor immunotherapeutic strategies.

H-2 class I-negative, HLA-A2.1-transgenic HHD mice were used for a comparative evaluation of the immunogenicity of HLA-A2.1-restricted human tumor-associated cytotoxic T lymphocyte (CTL) epitopes. A hierarchy was established among these peptides injected into mice in incomplete Freund's adjuvant which correlates globally with their capacity to bind and stabilize HLA-A2.1 molecules. Co-injection of a helper peptide enhanced most CTL responses. In contrast, classical HLA class I-transgenic mice which still express their own class I molecules did not, in most cases, develop HLA-A2.1-restricted CTL responses under the same experimental conditions. Different monoepitope immunization strategies of acceptable clinical usage were compared in HHD mice. Recombinant Ty-virus-like particles, or DNA encoding epitopes fused to the hepatitis B virus middle envelope protein gave the best results. Using this latter approach and a melanoma-based polyepitope construct, CTL responses against five distinct epitopes could be elicited simultaneously in a single animal. Thus, HHD mice provide a versatile animal model for preclinical evaluation of peptide-based cancer immunotherapy.

Chimeric peptides: a new approach to enhancing the immunogenicity of peptides with low MHC class I affinity: application in antiviral vaccination.

Recruitment of the CTL repertoire specific for subdominant epitopes that have a low MHC class I-binding affinity could be the way to achieve an efficient protective immunity against spontaneous tumors and viruses with high mutation rate. However, we have reported recently that subdominant peptides of influenza A Puerto Rico/8/34 (flu PR8) nucleoprotein (NP) with low Db affinity are only partially able to protect mice against lethal influenza infection. This seems to be due to their inability to recruit the specific CTL repertoire, and suggests that subdominant peptides could be used for vaccination only if they become highly immunogenic. In this work, we describe an approach that allows enhancement of the immunogenicity of every low affinity peptide presented by the Db molecule. It consists in producing chimeric peptides composed by amino acids from a high Db affinity peptide (NP366) in positions that interact with the MHC, and amino acids from low Db affinity nonimmunogenic influenza NP-derived peptides (NP17, NP97, NP330, and NP469) in positions that are exposed to the TCR. All chimeric peptides tested exhibited a high Db affinity and efficiently recruited the CTL repertoire specific for the corresponding low Db affinity peptide. Furthermore, vaccination with chimeric peptides that corresponded to subdominant NP17 and NP97 peptides induced a very potent anti-flu PR8 protective immunity.

Protection against lethal viral infection by vaccination with nonimmunodominant peptides.

CTL response of H-2b mice to influenza PR8 virus is directed against the nucleoprotein (NP)-derived immunodominant 366-374 (NP366PR8) peptide presented by the Db molecule. However, NP has three nonimmunodominant peptides corresponding to the 17-25 (NP17), 55-63 (NP55), and 97-105 (NP97) sequences that have the Db consensus motifs and bind to the Db molecule with an intermediate (NP55) or low (NP17 and NP97) affinity. In a previous report, we have shown that NP55 peptide is naturally processed by infected cells. In the present work, we studied whether nonimmunodominant peptides can protect mice against viral infection. Antiviral protection was evaluated by measuring three parameters: survival after inoculation of a lethal dose of mouse-adapted PR8 virus, percentage of pulmonary lesions in surviving mice, and virus clearance from lungs of infected mice. Our results showed that immunization of B6 mice with nonimmunodominant peptides protected from PR8 virus infection, although less efficiently than immunization with the immunodominant NP366PR8 peptide. Protection was mediated by CD8 T cells. The efficacy of nonimmunodominant peptides correlated with their Db binding affinity; the low affinity binders NP17 and NP97 induced a weaker protection than the intermediate affinity binder NP55. A mixture of NP366PR8 and nonimmunodominant peptides gave a higher protection than NP366PR8 peptide alone. In conclusion, nonimmunodominant peptides protect against a viral infection with an efficacy that is proportional to their affinity for the restricting class I molecule.