Epstein-Barr virus-transformed B cells, a potentially convenient source of autologous antigen-presenting cells for the propagation of certain human cytotoxic T lymphocytes

Development of TCR-T cell therapy targeting mismatched HLA-DPB1 for relapsed leukemia after allogeneic transplantation

Relapsed leukemia after allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains a significant challenge, with the re-emergence of the primary disease being the most frequent cause of death. Human leukocyte antigen (HLA)-DPB1 mismatch occurs in approximately 70% of unrelated allo-HSCT cases, and targeting mismatched HLA-DPB1 is considered reasonable for treating relapsed leukemia following allo-HSCT if performed under proper conditions. In this study, we established several clones restricted to HLA-DPB1*02:01, -DPB1*04:02, and -DPB1*09:01 from three patients who underwent HLA-DPB1 mismatched allo-HSCT using donor-derived alloreactive T cells primed to mismatched HLA-DPB1 in the recipient's body after transplantation. A detailed analysis of the DPB1*09:01-restricted clone 2A9 showed reactivity against various leukemia cell lines and primary myeloid leukemia blasts, even with low HLA-DP expression. T cell receptor (TCR)-T cells derived from clone 2A9 retained the ability to trigger HLA-DPB1*09:01-restricted recognition and lysis of various leukemia cell lines in vitro. Our study demonstrated that the induction of mismatched HLA-DPB1 specific T cell clones from physiologically primed post-allo-HSCT alloreactive CD4⁺ T cells and the redirection of T cells with cloned TCR cDNA by gene transfer are feasible as techniques for future adoptive immunotherapy.

Facts and Hopes in the Relationship of EBV with Cancer Immunity and Immunotherapy

Epstein-Barr virus (EBV), the first identified human tumor virus, infects and takes up residency in almost every human. However, EBV genome-positive tumors arise in only a tiny minority of infected people, presumably when the virus-carrying tumor cells are able to evade immune surveillance. Traditional views regard viral antigens as the principal targets of host immune surveillance against virus-infected cells. However, recent findings indicate that EBV-infected/-transformed B cells elicit both cytotoxic CD8+ and CD4+ T-cell responses against a wide range of overexpressed cellular antigens known to function as tumor-associated antigens (TAA), in addition to various EBV-encoded antigens. This not only broadens the ways by which the immune system controls EBV infection and prevents it from causing cancers, but also potentially extends immune protection toward EBV-unrelated cancers by targeting shared TAAs. The goal of this review is to incorporate these new findings with literature data and discuss future directions for improved understanding of EBV-induced antitumor immunity, as well as the hopes for rational immune strategies for cancer prevention and therapy.

Competition-Based Cell Assay Employing Soluble T Cell Receptors to Assess MHC Class II Antigen Processing and Presentation

Accurate assessment of antigen-specific immune responses is critical in the development of safe and efficacious biotherapeutics and vaccines. Endosomal processing of a protein antigen followed by presentation on major histocompatibility complex (MHC) class II constitute necessary steps in the induction of CD4+ T cell immune responses. Current preclinical methods for assessing immunogenicity risk consist of in vitro cell-based assays and computational prediction tools. Cell-based assays are time and labor-intensive while in silico methodologies have limitations. Here, we propose a novel cell-based assay capable of investigating an antigen's endosomal processing and MHC class II presentation capabilities. This novel assay relies on competition between epitopes for MHC class II binding and employs labeled soluble T cell receptors (sTCRs) as detectors of epitope presentation.

T Cell Receptor Engineered Lymphocytes for Cancer Therapy

T lymphocytes are capable of specific recognition and elimination of target cells. Physiological antigen recognition is mediated by the T cell receptor (TCR), which is an alpha beta heterodimer comprising the products of randomly rearranged V, D, and J genes. The exquisite specificity and functionality of T cells can be leveraged for cancer therapy: specifically, the adoptive transfer of T cells that express tumor-reactive TCRs can induce regression of solid tumors in patients with advanced cancer. However, the isolation and expression of a tumor antigen-specific TCRs is a highly involved process that requires identifying an immunogenic epitope, ensuring human cells are of the correct haplotype, performing a laborious T cell expansion process, and carrying out downstream TCR sequencing and cloning. Recent advances in single-cell sequencing have begun to streamline this process. This protocol synthesizes and expands upon methodologies to generate, isolate, and engineer human T cells with tumor-reactive TCRs for adoptive cell therapy. Though this process is perhaps more arduous than the alternative strategy of using chimeric antigen receptors (CARs) for engineering, the ability to target intracellular proteins using TCRs substantially increases the types of antigens that can be safely targeted. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Generation of human autologous dendritic cells from monocytes Basic Protocol 2: In vitro priming and expansion of human antigen-specific T cells Basic Protocol 3: Cloning of antigen-specific T cell receptors based on single-cell VDJ sequencing data Basic Protocol 4: Validation of T cell receptor expression and functionality in vitro Basic Protocol 5: Rapid expansion of T cell receptor-transduced T cells and human T cell clones.

Antibodies conjugated with viral antigens elicit a cytotoxic T cell response against primary CLL ex vivo

Chronic lymphocytic leukemia (CLL) is the most frequent B cell malignancy in Caucasian adults. The therapeutic armamentarium against this incurable disease has recently seen a tremendous expansion with the introduction of specific pathway inhibitors and innovative immunotherapy. However, none of these approaches is curative and devoid of side effects. We have used B-cell-specific antibodies conjugated with antigens (AgAbs) of the Epstein-Barr virus (EBV) to efficiently expand memory CD4⁺ cytotoxic T lymphocytes (CTLs) that recognized viral epitopes in 12 treatment-naive patients with CLL. The AgAbs carried fragments from the EBNA3C EBV protein that is recognized by the large majority of the population. All CLL cells pulsed with EBNA3C-AgAbs elicited EBV-specific T cell responses, although the intensity varied across the patient collective. Interestingly, a large proportion of the EBV-specific CD4⁺ T cells expressed granzyme B (GrB), perforin, and CD107a, and killed CLL cells loaded with EBV antigens with high efficiency in the large majority of patients. The encouraging results from this preclinical ex vivo study suggest that AgAbs have the potential to redirect immune responses toward CLL cells in a high percentage of patients in vivo and warrant the inception of clinical trials.

Biphasic Rapamycin Effects in Lymphoma and Carcinoma Treatment

mTOR drives tumor growth but also supports T-cell function, rendering the applications of mTOR inhibitors complex especially in T-cell malignancies. Here, we studied the effects of the mTOR inhibitor rapamycin in mouse EL4 T-cell lymphoma. Typical pharmacologic rapamycin (1-8 mg/kg) significantly reduced tumor burden via direct suppression of tumor cell proliferation and improved survival in EL4 challenge independent of antitumor immunity. Denileukin diftitox (DD)-mediated depletion of regulatory T cells significantly slowed EL4 growth in vivo in a T-cell-dependent fashion. However, typical rapamycin inhibited T-cell activation and tumor infiltration in vivo and failed to boost DD treatment effects. Low-dose (LD) rapamycin (75 μg/kg) increased potentially beneficial CD44hiCD62L⁺ CD8⁺ central memory T cells in EL4 challenge, but without clinical benefit. LD rapamycin significantly enhanced DD treatment efficacy, but DD plus LD rapamycin treatment effects were independent of antitumor immunity. Instead, rapamycin upregulated EL4 IL2 receptor in vitro and in vivo, facilitating direct DD tumor cell killing. LD rapamycin augmented DD efficacy against B16 melanoma and a human B-cell lymphoma, but not against human Jurkat T-cell lymphoma or ID8agg ovarian cancer cells. Treatment effects correlated with IL2R expression, but mechanisms in some tumors were not fully defined. Overall, our data define a distinct, biphasic mechanisms of action of mTOR inhibition at doses that are clinically exploitable, including in T-cell lymphomas. Cancer Res; 77(2); 520-31. ©2016 AACR.

Immunotherapeutic approaches for the treatment of childhood, adolescent and young adult non-Hodgkin lymphoma

With the introduction of the anti-CD20 monoclonal antibody rituximab, B-cell non-Hodgkin lymphoma was the first malignancy successfully treated with an immunotherapeutic agent. Since then, numerous advances have expanded the repertoire of immunotherapeutic agents available for the treatment of a variety of malignancies, including many lymphoma subtypes. These include the introduction of monoclonal antibodies targeting a variety of cell surface proteins, including the successful targeting of immunoregulatory checkpoint receptors present on T-cells or tumour cells. Additionally, cellular immunotherapeutic approaches utilize T- or Natural Killer-cells generated with chimeric antigen receptors against cell surface proteins or Epstein-Barr virus-associated latent membrane proteins. The following review describes the current state of immunotherapy for non-Hodgkin lymphoma including a summary of currently available data and promising agents currently in clinical development with future promise in the treatment of childhood, adolescent and young adult non-Hodgkin lymphoma.

A flow cytometry-based assay to assess minute frequencies of CD8+ T cells by their cytolytic function

Limited sample size and low sensitivity of currently used functional assays challenge direct analysis of cytotoxic CD8+ T lymphocyte activity to quantify antigen-specific immunity after infection or vaccination. Our flow cytometry-based assay reproducibly detects at least three epitope-specific CD8+ T lymphocytes by their cytolytic function. As exemplified for viral epitopes restricted to the human leukocyte antigen (HLA)-A2, the HLA-A2+ human somatic cell hybrid T2 provided an about 10-fold more sensitive readout as compared to autologous B-lymphoblastoid cells or the human erythroleukemia cell line K562 transfected to express HLA-A2 when used as target cells. We named our assay VITAL-FR assay, referring to Hermans et al. (2004) and indicating the modification of using Far Red (FR) dye instead of CMTMR. Under optimal conditions the VITAL-FR assay proved 30 times more sensitive than the 51chromium-release assay to assess epitope-specific target cell lysis. The high overall sensitivity of the VITAL-FR assay basically depended on the negligible spectral overlap of the emission of a stable Far Red fluorescent reporter with the green tracer for target cell labelling. It also profited from long co-incubation of effector and target cells of up to 72, from prior in-vitro culture increasing the frequency of epitope-specific CD8+ T cells and from generic, easily accessible standardized target cells that were used with only 10(3) specific and 10(3) control target cells per individual experimental reaction. Our functional approach with the VITAL-FR assay therefore ideally suits for monitoring CD8+ T cell-mediated cytotoxicity in e.g. vaccination studies with known MHC-restricted immunogenic peptides in scientific and diagnostic applications.

B lymphoblastoid cell lines as efficient APC to elicit CD8+ T cell responses against a cytomegalovirus antigen

Potent and readily accessible APC are critical for development of immunotherapy protocols to treat viral disease and cancer. We have shown that B lymphoblastoid cell lines (BLCL) that stably express CMV phosphoprotein 65 (BLCLpp65), as a result of retroviral transduction, can be used to generate ex vivo CTL cultures that possess cytotoxicity against CMV and EBV. In this report, we demonstrate that the EBV-specific cytotoxicity in the BLCLpp65-primed culture had a spectrum of EBV-Ag recognition similar to that of the BLCL-primed counterpart, suggesting that retroviral transduction and expression of the CMV Ag would not compromise the Ag-presenting capacity of BLCL. In addition, BLCLpp65 appeared to present multiple natural pp65 epitopes, because pp65-specific CTL, which recognized different CMV clinical isolates, were generated in BLCLpp65-primed cultures from individuals with various HLA backgrounds. Consistent with a polyclonal expansion of virus-specific CTL, T cell lines established from the BLCLpp65-primed CTL cultures expressed different TCR-Vbeta Although most of the virus-specific T cell isolates were CD8+, EBV-specific CD4+ lines were also established from BLCLpp65-primed cultures. Western blot analysis revealed that the CD8+ lines, but not the CD4+ line, expressed granzyme B, consistent with features of classic CTL. Thus, our results suggested that BLCL stably expressing a foreign Ag might be used as a practical APC to elicit CD8+ T cell responses.

Apoptosis in Porphyromonas gingivalis-specific T-cell lines

Fluorescence-activated cell sorter analysis and transmission electron microscopy were used to determine the presence of apoptotic cells in Porphyromonas gingivalis-specific T-cell lines established from the peripheral blood of 10 P. gingivalis-infected individuals. P. gingivalis outer membrane antigens were presented to the T cells by autologous Epstein-Barr virus-transformed B cells for 6, 24, 48 and 72 h. Transmission electron microscopy demonstrated the presence of typical apoptotic cells in all cultures. Annexin V-positive cells were present at low concentrations at all 4 four periods. A mean of approximately 2-3% of the CD4 cells and 1-3.5% of the CD8 cells were annexin V-positive, with an increase to around 5.5% positive CD4 cells at 6 h in wells containing P. gingivalis compared with cultures not containing antigen. This difference was not, however, significant at the 0.05 level (P = 0.073). The mean (+/- standard error) CD4:CD8 ratios of the T-cell lines when first established using peripheral blood mononuclear cells as antigen-presenting cells was significantly higher (5.2 +/- 1.1) than when transformed B cells were used as antigen-presenting cell (1.2 +/- 0.5). While this study has shown apoptosis occurring in the T-cell lines, it has not shown definitively that the reversion in the CD4:CD8 ratio in the P. gingivalis-specific T cells following antigen presentation by autologous Epstein-Barr virus-transformed B cells is due to apoptosis of a CD4 population. Alternatively, the reversion in the CD4:CD8 ratio could be due to a selective proliferation of the CD8 population which, in turn, could be relevant to the immunopathology of periodontal disease induced by P. gingivalis.