CD8 T cell tolerance to a tumor-associated self-antigen is reversed by CD4 T cells engineered to express the same T cell receptor

Ag receptors used for cancer immunotherapy are often directed against tumor-associated Ags also expressed in normal tissues. Targeting of such Ags can result in unwanted autoimmune attack of normal tissues or induction of tolerance in therapeutic T cells. We used a murine model to study the phenotype and function of T cells redirected against the murine double minute protein 2 (MDM2), a tumor-associated Ag that shows low expression in many normal tissues. Transfer of MDM2-TCR-engineered T cells into bone marrow chimeric mice revealed that Ag recognition in hematopoietic tissues maintained T cell function, whereas presentation of MDM2 in nonhematopoietic tissues caused reduced effector function. TCR-engineered CD8(+) T cells underwent rapid turnover, downmodulated CD8 expression, and lost cytotoxic function. We found that MDM2-TCR-engineered CD4(+) T cells provided help and restored cytotoxic function of CD8(+) T cells bearing the same TCR. Although the introduction of the CD8 coreceptor enhanced the ability of CD4(+) T cells to recognize MDM2 in vitro, the improved self-antigen recognition abolished their ability to provide helper function in vivo. The data indicate that the same class I-restricted TCR responsible for Ag recognition and tolerance induction in CD8(+) T cells can, in the absence of the CD8 coreceptor, elicit CD4 T cell help and partially reverse tolerance. Thus MHC class I-restricted CD4(+) T cells may enhance the efficacy of therapeutic TCR-engineered CD8(+) T cells and can be readily generated with the same TCR

Differences in systemic adaptive immunity contribute to the 'frequent exacerbator' COPD phenotype

Contains fulltext : 165954.pdf (publisher's version ) (Open Access)BACKGROUND: Some COPD patients are more susceptible to exacerbations than others. Mechanisms underlying these differences in susceptibility are not well understood. We hypothesized that altered cell mediated immune responses may underlie a propensity to suffer from frequent exacerbations in COPD. METHODS: Peripheral blood mononuclear cells (PBMCs) were obtained from 24 stable COPD patients, eight frequent exacerbators (>/=3 diary-card exacerbations/year) and 16 infrequent exacerbators (< 3 diary-card exacerbations/year). Detailed multi-parameter flow cytometry was used to study differences in innate and adaptive systemic immune function between frequent and infrequently exacerbating COPD patients. RESULTS: The 24 COPD patients had a mean (SD) age of 76.3 (9.4) years and FEV1 1.43 (0.60)L, 53.3 (18.3)% predicted. PBMCs of frequent exacerbators (FE) contained lower frequencies of CD4+ T central memory cells (CD4+ Tcm) compared to infrequent exacerbators (IE) (FE = 18.7 %; IE = 23.9 %; p = 0.035). This observation was also apparent in absolute numbers of CD4+ Tcm cells (FE = 0.17 x 10^6/mL; IE = 0.25 x 10^6/mL; p = 0.035). PBMCs of FE contained a lower frequency of CD8+ T effector memory cells expressing HLA-DR (Human Leukocyte Antigen - D Related) compared to IE COPD patients (FE = 22.7 %; IE = 31.5 %; p = 0.007). CONCLUSION: Differences in the adaptive systemic immune system might associate with exacerbation susceptibility in the 'frequent exacerbator' COPD phenotype. These differences include fewer CD4+ T central memory cells and CD8+ T effector memory cells. TRIAL REGISTRATION: Not applicable

Induction of unresponsiveness limits tumor protection by adoptively transferred MDM2-specific cytotoxic T lymphocytes.

There is evidence showing that high avidity CTLs can be more effective than low avidity CTLs for adoptive tumor immunotherapy. Because many T cell-recognized tumor antigens are nonmutated self-proteins, tolerance mechanisms are likely to render high avidity T cells unresponsive or cause T cell elimination by clonal deletion. We recently used the allo-restricted strategy to circumvent immunologic tolerance to a ubiquitously expressed tumor-associated protein, MDM2, and raised high avidity CTLs in humans and in mice. In this study, we investigated whether high avidity MDM2-specific CTLs can mediate tumor protection without causing damage to normal tissues in mice. Although the CTLs prolonged survival of tumor-bearing mice without causing damage to normal tissues, tumor protection was incomplete. We show that tumor growth occurred despite the continued presence of MDM2-specific CTLs and the continued susceptibility of tumor cells to CTL killing. However, analysis of the CTLs revealed that they had been rendered unresponsive in vivo because they did not produce interferon \u3b3 in response to antigen-specific stimulation. These experiments suggest that induction of unresponsiveness may be an important mechanism limiting the efficacy of adoptive CTL therapy

CD8alpha/alpha homodimers fail to function as co-receptor for a CD8-dependent TCR

In this study, we have started to dissect the molecular basis of CD8 dependence of a high and low avidity CTL clone specific for the same peptide epitope. Using anti-CD8alpha and anti-CD8beta antibodies, we found that cytotoxicity and IFN-gamma production by high but not by low avidity CTL was strongly CD8 dependent. We isolated the TCR genes of both types of CTL clones and used retroviral gene transfer to analyse the function of these TCR in primary T cells of wild-type and CD8beta-deficient mice. Both TCR triggered antigen-specific killing in wild-type T cells, and blocking experiments showed that CD8 dependence/independence co-transferred with the TCR into primary T cells, indicating that it was dictated by the TCR itself. Gene transfer experiments into CD8beta-deficient T cells revealed that only the TCR derived from the CD8-independent CTL clone elicited antigen-specific cytotoxicity, while the CD8-dependent TCR was non-functional in the absence of the CD8beta-chain. These data indicate a striking difference between CD8alpha/beta heterodimers and CD8alpha/alpha homodimers as only the former were able to provide co-receptor function for the CD8-dependent TCR

Use of B cell-bound HLA-A2 class I monomers to generate high avidity, allo-restricted CTLs against the leukemia-associated protein Wilms tumor antigen.

Recent studies have detected Wilms tumor antigen (WT1)-specific cytotoxic T lymphocytes (CTLs) in patients with acute myelogenous leukemia (AML) and chronic myelogenous leukemia (CML) and demonstrated that most of these CTLs were low avidity. Although HLA-mismatched donors can mount high-avidity CTLs against HLA-A2-presented peptides of WT1, a dominant anti-alloimmune response usually obscures detection of peptide-specific CTLs. Here we explored the feasibility of using recombinant HLA-A2 monomers containing single peptide epitopes as immunogens to generate peptide-specific CTLs from allogeneic donors. We demonstrate that the coating of HLA-A2(-) B lymphocytes with A2/peptide monomers provides a strong stimulus for autologous peptide-specific CTLs. After 3 to 5 rounds of stimulation a population of CD8(+) T cells binding A2/peptide tetramers is easily detectable by fluorescence-activated cell sorting analysis. Furthermore, sorted A2/WT1 tetramer-positive CTLs display strong cytotoxic activity against leukemia cells expressing WT1 endogenously but not against WT1(-) human tumor cells. Thus, HLA/peptide monomers may be useful to isolate peptide-specific donor lymphocytes for treatment of patients with leukemia after HLA-mismatched transplantation

Elimination of human leukemia cells in NOD/SCID mice by WT1-TCR gene transduced human T cells

Cytotoxic T lymphocytes (CTLs) specific for an HLA-A2-presented peptide epitope of the Wilms tumor antigen-1 (WT1) can selectively kill immature human leukemia progenitor and stem cells in vitro. In this study we have used retroviral gene transfer to introduce a WT1-specific T-cell receptor (TCR) into T lymphocytes obtained from patients with leukemia and from healthy donors. TCR-transduced T cells kill leukemia cells in vitro and display WT1-specific cytokine production. Intravenous injection of TCR-transduced T cells into nonobese diabetic-severe combined immunodeficiency (NOD/SCID) mice harboring human leukemia cells resulted in leukemia elimination, whereas transfer of control T cells transduced with an irrelevant TCR was ineffective. The data suggest that adoptive immunotherapy with WT1-TCR gene-modified patient T cells should be considered for the treatment of leukemia

CD27 is required for protective lytic EBV antigen specific CD8+ T cell expansion.

Primary immunodeficiencies in the co-stimulatory molecule CD27 and its ligand CD70 predispose for pathologies of uncontrolled Epstein Barr virus (EBV) infection in nearly all affected patients. We demonstrate that both depletion of CD27 positive cells and antibody blocking of CD27 interaction with CD70 causes uncontrolled EBV infection in mice with reconstituted human immune system components. While overall CD8+ T cell expansion and composition is unaltered after antibody blocking of CD27, only some EBV specific CD8+ T cell responses, exemplified by early lytic EBV antigen BMLF1 specific CD8+ T cells are inhibited in their proliferation and killing of EBV transformed B cells. This suggests that CD27 is not required for all CD8+ T cell expansions and cytotoxicity, but for a subset of CD8+ T cell responses that protect us from EBV infection

An immunodominant NP_105-113-B*07:02 cytotoxic T cell response controls viral replication and is associated with less severe COVID-19 disease.

NP105-113-B*07:02-specific CD8+ T cell responses are considered among the most dominant in SARS-CoV-2-infected individuals. We found strong association of this response with mild disease. Analysis of NP105-113-B*07:02-specific T cell clones and single-cell sequencing were performed concurrently, with functional avidity and antiviral efficacy assessed using an in vitro SARS-CoV-2 infection system, and were correlated with T cell receptor usage, transcriptome signature and disease severity (acute n = 77, convalescent n = 52). We demonstrated a beneficial association of NP105-113-B*07:02-specific T cells in COVID-19 disease progression, linked with expansion of T cell precursors, high functional avidity and antiviral effector function. Broad immune memory pools were narrowed postinfection but NP105-113-B*07:02-specific T cells were maintained 6 months after infection with preserved antiviral efficacy to the SARS-CoV-2 Victoria strain, as well as Alpha, Beta, Gamma and Delta variants. Our data show that NP105-113-B*07:02-specific T cell responses associate with mild disease and high antiviral efficacy, pointing to inclusion for future vaccine design