Epitope recognition in HLA-DR3 transgenic mice immunized to TSH-R protein or peptides

Immunoinformatic Risk Assessment of Host Cell Proteins During Process Development for Biologic Therapeutics

The identification and removal of host cell proteins (HCPs) from biologic products is a critical step in drug development. Despite recent improvements to purification processes, biologics such as monoclonal antibodies, enzyme replacement therapies, and vaccines that are manufactured in a range of cell lines and purified using diverse processes may contain HCP impurities, making it necessary for developers to identify and quantify impurities during process development for each drug product. HCPs that contain sequences that are less conserved with human homologs may be more immunogenic than those that are more conserved. We have developed a computational tool, ISPRI-HCP, that estimates the immunogenic potential of HCP sequences by evaluating and quantifying T cell epitope density and relative conservation with similar T cell epitopes in the human proteome. Here we describe several case studies that support the use of this method for classifying candidate HCP impurities according to their immunogenicity risk.

Thyrotropin Receptor-Specific Lymphocytes in Adenovirus-TSHR-Immunized Native and Human Leukocyte Antigen-DR3-Transgenic Mice and in Graves' Disease Patient Blood

Background: Antigen-specific lymphocytes are increasingly investigated in autoimmune diseases and immune therapies. We sought to identify thyrotropin receptor (TSHR)-specific lymphocytes in mouse models of Graves' disease, including Graves' patient-specific immunotype human leukocyte antigen (HLA)-DR3, and in frozen and thawed Graves' patient blood samples. Methods and Results: Splenic lymphocytes of adenovirus (Ad)-TSHR-immunized BALB/c mice were stimulated with TSHR-specific peptides C, D, or J. Furthermore, CD154-expressing cells were enriched, expanded in vitro, and analyzed for binding of peptide-major histocompatibility complex (MHC) II multimers ("tetramers," immunotype H2-IA^d). Only peptides C and J were able to elicit increased expression/secretion of CD154 and interferon-γ, and tetramers which were loaded with peptide C resulted in antigen-specific signals in splenic lymphocytes from Ad-TSHR-immunized mice. Accordingly, TSHR-specific HLA-DR3-MHC class II tetramers loaded with peptide p10 specifically bound to human HLA-DR3-(allele B1*03:01)-transgenic Bl/6 mouse splenic T lymphocytes. In addition, we fine-tuned a protocol to reliably measure thawed human peripheral blood mononuclear cells (PBMCs), which resulted in reliable recovery after freezing and thawing with regard to vitality and B and T cell subpopulation markers including regulatory T cells (CD3, CD4, CD25, FoxP3, CD25^high, CD127^low). TSHR-specific HLA-DR3-MHC class II tetramers loaded with peptide p10 identified antigen-specific T cells in HLA-DR3-positive Graves' patients' thawed PBMCs. Moreover, stimulation-dependent release of interleukin (IL)-1beta, IL-6, tumor necrosis factor-alpha from thawed PBMCs occurred at the expected levels. Conclusions: Novel MHC II tetramers identified TSHR-specific T lymphocytes in Ad-TSHR-immunized hyperthyroid BALB/c or HLA-DR3-transgenic mice and in thawed human PBMCs from patients with Graves' disease. These assays may contribute to measure both disease severity and effects of novel immune therapies in future animal studies and clinical investigations of Graves' disease.

Human leucocyte antigen alleles confer susceptibility and progression to Graves' ophthalmopathy in a Southern Chinese population

Purpose

To evaluate the contributions of human leucocyte antigen (HLA) class I and II genes in the development of Graves’ ophthalmopathy (GO) in a Southern Chinese population.

Methods

Eight HLA loci were genotyped and analysed in 272 unrelated patients with Graves’ disease (GD) or the proptosis and myogenic phenotypes of GO, and 411 ethnically matched control subjects.

Results

The allele frequencies of HLA-DRB1*16:02 and -DQB1*05:02 in the GD, proptosis and myogenic groups, HLA-B*38:02 and -DQA1*01:02 in the myogenic group were significantly higher than those in the control group, respectively (all corrected p values <0.05, OR >2.5). The haplotype frequencies of HLA-DRB1*16:02-DQA1*01:02-DQB1*05:02 and HLA-DRB1*16:02-DQA1*01:02-DQB1*05:02-DPA1*02:02-DPB1*05:01 in the proptosis and myogenic groups, and HLA-A*02:03-B*38:02-C*07:02 and HLA-A*02:03-B*38:02-C*07:02-DRB1*16:02-DQA1*01:02-DQB1*05:02-DPA1*02:02-DPB1*05:01 in the myogenic group were significantly higher than those in the control group respectively (all corrected p values <0.05, OR >2.5). The potential epitopes (‘FLGIFNTGL’ of TSHR, ‘IRHSHALVS’, ‘ILYIRTNAS’ and ‘FVFARTMPA’ of IGF-1R) were fitted exactly in the peptide-binding groove between HLA-DRA1-DRB1*16:02 heterodimer, and the epitopes (‘ILEITDNPY’ of THSR, ‘NYALVIFEM’ and ‘NYSFYVLDN’ of IGF-1R) were also fitted exactly in the peptide-binding groove between HLA-DQA1*01:02-DQB1*05:02 heterodimer.

Conclusions

The HLA-DRB1*16:02 and -DQB1*01:02 alleles might be risk factors for GD including the proptosis and myogenic phenotypes of GO. The alleles HLA-B*38:02, -DQA1*01:02, the HLA haplotypes consisting of HLA-B*38:02, -DRB1*16:02, -DQA1*01:02 and -DQB1*05:02 might be susceptibility risk factors for GO. Simultaneously, some epitopes of TSHR and IGF-1R tightly binding to groove of HLA-DRA1-DRB1*16:02 or HLA-DQA1*01:02-DQB1*05:02 heterodimers might provide some hints on presenting the pathological antigen in GO.

Cepharanthine blocks TSH receptor peptide presentation by HLA-DR3: Therapeutic implications to Graves' disease

We have previously identified a signature HLA-DR3 pocket variant, designated HLA-DRβ1-Arg74 that confers a high risk for Graves' Disease (GD). In view of the key role of HLA-DRβ1-Arg74 in triggering GD we hypothesized that thyroid-stimulating hormone receptor (TSHR) peptides that bind to the HLA-DRβ1-Arg74 pocket with high affinity represent key pathogenic TSHR peptides triggering GD, and that blocking their presentation to CD4⁺ T-cells can be used as a novel therapeutic approach in GD. There were several previous attempts to identify the major pathogenic TSHR peptide utilizing different methodologies, however the results were inconsistent and inconclusive. Therefore, the aim of our study was to use TSHR peptide binding affinity to HLA-DRβ1-Arg74 as a method to identify the key pathogenic TSHR peptides that trigger GD. Using virtual screening and ELISA and cellular binding assays we identified 2 TSHR peptides that bound with high affinity to HLA-DRβ1-Arg74 - TSHR.132 and TSHR.197. Peptide immunization studies in humanized DR3 mice showed that only TSHR.132, but not TSHR.197, induced autoreactive T-cell proliferation and cytokine responses. Next, we induced experimental autoimmune Graves' disease (EAGD) in a novel BALB/c-DR3 humanized mouse model we created and confirmed TSHR.132 as a major DRβ1-Arg74 binding peptide triggering GD in our mouse model. Furthermore, we demonstrated that Cepharanthine, a compound we have previously identified as DRβ1-Arg74 blocker, could block the presentation and T-cell responses to TSHR.132 in the EAGD model.

Comprehensive research on thyroid diseases associated with autoimmunity: autoimmune thyroid diseases, thyroid diseases during immune-checkpoint inhibitors therapy, and immunoglobulin-G4-associated thyroid diseases

Various thyroid diseases are associated with autoimmunity. Major autoimmune thyroid diseases are Graves' disease (GD) and Hashimoto's thyroiditis (HT). Thyrotropin receptor is an autoantigen in GD, and its immunogenicity has been examined. Immune-checkpoint inhibitor (ICI) is recently widely used for treatment of malignant tumors, but cases of thyroid diseases during ICI treatment have been increasing. Thyroid diseases during ICI therapy have been investigated in immunological and clinical aspects, and their Japanese official diagnostic guidelines were established. In addition, serum and tissue immunoglobulin-G4 levels have been examined in association with clinicopathological characteristics in GD, HT, and Riedel's thyroiditis. We review these diseases associated with thyroid autoimmunity and comprehensively discuss their potential application in future research and therapeutic options.

Comparative Assessment of Female Mouse Model of Graves' Orbitopathy Under Different Environments, Accompanied by Proinflammatory Cytokine and T-Cell Responses to Thyrotropin Hormone Receptor Antigen

We recently described a preclinical model of Graves' orbitopathy (GO), induced by genetic immunization of eukaryotic expression plasmid encoding human TSH receptor (TSHR) A-subunit by muscle electroporation in female BALB/c mice. The onset of orbital pathology is characterized by muscle inflammation, adipogenesis, and fibrosis. Animal models of autoimmunity are influenced by their environmental exposures. This follow-up study was undertaken to investigate the development of experimental GO in 2 different locations, run in parallel under comparable housing conditions. Functional antibodies to TSHR were induced in TSHR A-subunit plasmid-immunized animals, and antibodies to IGF-1 receptor α-subunit were also present, whereas control animals were negative in both locations. Splenic T cells from TSHR A-subunit primed animals undergoing GO in both locations showed proliferative responses to purified TSHR antigen and secreted interferon-γ, IL-10, IL-6, and TNF-α cytokines. Histopathological evaluation showed orbital tissue damage in mice undergoing GO, manifest by adipogenesis, fibrosis, and muscle damage with classic signs of myopathy. Although no inflammatory infiltrate was observed in orbital tissue in either location, the appearances were consistent with a "hit-and-run" immune-mediated inflammatory event. A statistically significant increase of cumulative incidence of orbital pathology when compared with control animals was shown for both locations, confirming onset of orbital dysimmune myopathy. Our findings confirm expansion of the model in different environments, accompanied with increased prevalence of T cell-derived proinflammatory cytokines, with relevance for pathogenesis. Wider availability of the model makes it suitable for mechanistic studies into pathogenesis and undertaking of novel therapeutic approaches.

Thyrotropin Receptor Epitope and Human Leukocyte Antigen in Graves' Disease

Graves' disease (GD) is an organ-specific autoimmune disease, and thyrotropin (TSH) receptor (TSHR) is a major autoantigen in this condition. Since the extracellular domain of human TSHR (TSHR-ECD) is shed into the circulation, TSHR-ECD is a preferentially immunogenic portion of TSHR. Both genetic factors and environmental factors contribute to development of GD. Inheritance of human leukocyte antigen (HLA) genes, especially HLA-DR3, is associated with GD. TSHR-ECD protein is endocytosed into antigen-presenting cells (APCs), and processed to TSHR-ECD peptides. These peptide epitopes bind to HLA-class II molecules, and subsequently the complex of HLA-class II and TSHR-ECD epitope is presented to CD4+ T cells. The activated CD4+ T cells secrete cytokines/chemokines that stimulate B-cells to produce TSAb, and in turn hyperthyroidism occurs. Numerous studies have been done to identify T- and B-cell epitopes in TSHR-ECD, including (1) in silico, (2) in vitro, (3) in vivo, and (4) clinical experiments. Murine models of GD and HLA-transgenic mice have played a pivotal role in elucidating the immunological mechanisms. To date, linear or conformational epitopes of TSHR-ECD, as well as the molecular structure of the epitope-binding groove in HLA-DR, were reported to be related to the pathogenesis in GD. Dysfunction of central tolerance in the thymus, or in peripheral tolerance, such as regulatory T cells, could allow development of GD. Novel treatments using TSHR antagonists or mutated TSHR peptides have been reported to be effective. We review and update the role of immunogenic TSHR epitopes and HLA in GD, and offer perspectives on TSHR epitope specific treatments.

B cell epitope spreading: mechanisms and contribution to autoimmune diseases

While a variety of factors act to trigger or initiate autoimmune diseases, the process of epitope spreading is an important contributor in their development. Epitope spreading is a diversification of the epitopes recognized by the immune system. This process happens to both T and B cells, with this review focusing on B cells. Such spreading can progress among multiple epitopes on a single antigen, or from one antigenic molecule to another. Systemic lupus erythematosus, multiple sclerosis, pemphigus, bullous pemphigoid and other autoimmune diseases, are all influenced by intermolecular and intramolecular B cell epitope spreading. Endocytic processing, antigen presentation, and somatic hypermutation act as molecular mechanisms that assist in driving epitope spreading and broadening the immune response in autoimmune diseases. The purpose of this review is to summarize our current understanding of B cell epitope spreading with regard to autoimmunity, how it contributes during the progression of various autoimmune diseases, and treatment options available.

CHOPPI: a web tool for the analysis of immunogenicity risk from host cell proteins in CHO-based protein production

Despite high quality standards and continual process improvements in manufacturing, host cell protein (HCP) process impurities remain a substantial risk for biological products. Even at low levels, residual HCPs can induce a detrimental immune response compromising the safety and efficacy of a biologic. Consequently, advanced-stage clinical trials have been cancelled due to the identification of antibodies against HCPs. To enable earlier and rapid assessment of the risks in Chinese Hamster Ovary (CHO)-based protein production of residual CHO protein impurities (CHOPs), we have developed a web tool called CHOPPI, for CHO Protein Predicted Immunogenicity. CHOPPI integrates information regarding the possible presence of CHOPs (expression and secretion) with characterizations of their immunogenicity (T cell epitope count and density, and relative conservation with human counterparts). CHOPPI can generate a report for a specified CHO protein (e.g., identified from proteomics or immunoassays) or characterize an entire specified subset of the CHO genome (e.g., filtered based on confidence in transcription and similarity to human proteins). The ability to analyze potential CHOPs at a genomic scale provides a baseline to evaluate relative risk. We show here that CHOPPI can identify clear differences in immunogenicity risk among previously validated CHOPs, as well as identify additional “risky” CHO proteins that may be expressed during production and induce a detrimental immune response upon delivery. We conclude that CHOPPI is a powerful tool that provides a valuable computational complement to existing experimental approaches for CHOP risk assessment and can focus experimental efforts in the most important directions. Biotechnol. Bioeng. 2014;111: 2170–2182.