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Recent studies have demonstrated that [CD4.sup.+] T cells can efficiently reject MHC-II-negative tumors. This requires indirect presentation of tumor-associated antigens on surrounding antigen-presenting cells. We hypothesized that intercellular transfer of proteins is not the sole consequence of cell death-mediated protein release, but depends on heat-shock cognate protein 70 (HSC70) and its KFERQ-like binding motif on substrate proteins. Using human Y chromosome antigen DBY, we showed that mutation of one of its 2 putative binding motifs markedly diminished T cell activation after indirect presentation and reduced protein-protein interaction with HSC70. Intercellular antigen transfer was shown to be independent of cell-cell contact, but relied on engulfment within secreted microvesicles. In vivo, alterations of the homologous KFERQ-like motif in murine DBY hampered tumor rejection, T cell activation, and migration into the tumor and substantially impaired survival. Collectively, we show that intercellular antigen transfer of DBY is tightly regulated via binding to HSC70 and that this mechanism influences recognition and rejection of MHC-II-negative tumors in vivo., Introduction [CD4.sup.+] T cells play a central role in orchestrating innate and adaptive immune responses. Upon recognition of their cognate antigen in MHC-II molecules, [CD4.sup.+] T cells become activated and [...]

Patients with hematological malignancies can be successfully treated with HLA-matched T cell-depleted allogeneic stem cell transplantation (alIoSCT) and subsequent donor lymphocyte infusions (DLIs). The efficacy of DLI is mediated by donor T cells recognizing minor histocompatibility antigens (mHags) on malignant recipient cells. Because HLA class II molecules are predominantly expressed on hematopoietic cells, mHag-specific [CD4.sup.+] T cells may selectively mediate graft versus leukemia (GvL) reactivity without graft versus host disease (GvHD). In this study, we used a recombinant bacteria cDNA library for the identification of the first autosomal HLA class II (HLA-DQBl*0603)-restricted mHag LBPI4K2B-1S encoded by the broadly expressed phosphatidylinositol 4-kinase type II [beta] gene. A polyclonal [CD4.sup.+] T cell response against LB-PI4K2B-1S was demonstrated in a patient with relapsed chronic myeloid leukemia (CML) who responded to DLI after HLA-matched alIoSCT. LB-PI4K2B-1S-specific [CD4.sup.+] T cells recognized and lysed the [CD34.sup.+] CML cells of the patient and other leukemic cells as well as high HLA-DQ-expressing normal hematopoietic cells. HLA-DQ expression on normal cells of nonhematopoietic origin was moderately up-regulated by IFN-[gamma], and not sufficient for T cell recognition. We hypothesize that LB-PI4K2B-1S-specific [CD4.sup.+] T cells contributed to the antitumor response by both directly eliminating malignant cells as effector cells and stimulating [CD8.sup.+] T cell immunity as helper cells. donor lymphocyte infusions | hematological malignancies | immunotherapy | stem cell transplantation | T lymphocytes

Since December 2019, Coronavirus disease‐19 (COVID‐19) has spread rapidly throughout the world, leading to a global effort to develop vaccines and treatments. Despite extensive progress, there remains a need for treatments to bolster the immune responses in infected immunocompromised individuals, such as cancer patients who recently underwent a haematopoietic stem cell transplantation. Immunological protection against COVID‐19 is mediated by both short‐lived neutralizing antibodies and long‐lasting virus‐reactive T cells. Therefore, we propose that T cell therapy may augment efficacy of current treatments. For the greatest efficacy with minimal adverse effects, it is important that any cellular therapy is designed to be as specific and directed as possible. Here, we identify T cells from COVID‐19 patients with a potentially protective response to two major antigens of the SARS‐CoV‐2 virus, Spike and Nucleocapsid protein. By generating clones of highly virus‐reactive CD4+ T cells, we were able to confirm a set of nine immunodominant epitopes and characterize T cell responses against these. Accordingly, the sensitivity of T cell clones for their specific epitope, as well as the extent and focus of their cytokine response was examined. Moreover, using an advanced T cell receptor (TCR) sequencing approach, we determined the paired TCR‐αβ sequences of clones of interest. While these data on a limited population require further expansion for universal application, the results presented here form a crucial first step towards TCR‐transgenic CD4+ T cell therapy of COVID‐19. [ABSTRACT FROM AUTHOR]

Clinical studies have indicated that HLA-DPB1 functions as a classical transplantation antigen in allogeneic stem cell transplantation. Mismatching for HLA-DPB1 was associated with an increased risk of graft-versus-host disease (GVHD), but also a decreased risk of disease relapse. However, specific HLA-DPB1 mismatches were associated with poor clinical outcome. It was suggested that this unfavorable effect was caused by a difference in immunogenicity between HLA-DPB1 alleles. To analyze whether immunogenicity of HLA-DPB1 mismatches could be predicted based on the presence or absence of specific amino acid sequences we developed a model to generate allo-HLA-DPB1 responses in vitro. We tested in total 48 different stimulator/responder combinations by stimulating CD4+ T cells from 5 HLA-DPB1 homozygous individuals with the same antigen-presenting cells transduced with different allo-HLA-DPB1 molecules. HLA-DPB1 molecules used for stimulation comprised 76% to 99% of HLA-DPB1 molecules present in different ethnic populations. We show that all HLA-DPB1 mismatches as defined by allele typing resulted in high-frequency immune responses. Furthermore, we show that crossrecognition of different HLA-DPB1 molecules is a broadly observed phenomenon. We confirm previously described patterns in crossrecognition, and demonstrate that a high degree in similarity between HLA-DPB1 molecules is predictive for crossrecognition, but not for immunogenicity. [ABSTRACT FROM AUTHOR]

Since December 2019, Coronavirus disease-19 (COVID-19) has spread rapidly throughout the world, leading to a global effort to develop vaccines and treatments. Despite extensive progress, there remains a need for treatments to bolster the immune responses in infected immunocompromised individuals, such as cancer patients who recently underwent a haematopoietic stem cell transplantation. Immunological protection against COVID-19 is mediated by both short-lived neutralizing antibodies and long-lasting virus-reactive T cells. Therefore, we propose that T cell therapy may augment efficacy of current treatments. For the greatest efficacy with minimal adverse effects, it is important that any cellular therapy is designed to be as specific and directed as possible. Here, we identify T cells from COVID-19 patients with a potentially protective response to two major antigens of the SARS-CoV-2 virus, Spike and Nucleocapsid protein. By generating clones of highly virus-reactive CD4 + T cells, we were able to confirm a set of nine immunodominant epitopes and characterize T cell responses against these. Accordingly, the sensitivity of T cell clones for their specific epitope, as well as the extent and focus of their cytokine response was examined. Moreover, using an advanced T cell receptor (TCR) sequencing approach, we determined the paired TCR-αβ sequences of clones of interest. While these data on a limited population require further expansion for universal application, the results presented here form a crucial first step towards TCR-transgenic CD4 + T cell therapy of COVID-19., (© 2021 The Authors. Clinical & Experimental Immunology published by John Wiley & Sons Ltd on behalf of British Society for Immunology.)

It is well known that allo-reactive T cells play a crucial role in graft-versus-leukemia and graft-versus-host disease after allogeneic hematopoietic stem cell transplantation (alloSCT). Allo-reactive CD4(+) T cells can mediate direct cytolysis, but may also stimulate production of IgG antibodies as helper cells. Immune complexes may subsequently be processed and presented by professional antigen presenting cells and stimulate induction of specific CD8(+) T cells. As such, proteins targeted in coordinated T- and B-cell responses may represent a class of immunodominant antigens in clinical responses after alloSCT. We previously identified LB-PTK2B-1T as HLA class II restricted polymorphic antigen in a patient treated with donor lymphocyte infusion for relapsed chronic myeloid leukemia after HLA-matched alloSCT. Since PTK2B has also been described as antibody target, we here investigated whether a coordinated T- and B-cell response against PTK2B was induced. Patient serum before and after alloSCT and donor lymphocyte infusion (DLI) was screened for antibodies, and we indeed observed development of a humoral immune response against PTK2B. Antibodies against PTK2B were only found after DLI and, in contrast to the CD4(+) T cells, recognized a monomorphic region of the protein. To our knowledge, this is the first description of a coordinated allo-reactive CD4(+) T-cell and auto-reactive antibody response against an autosomal antigen.

Background: Patients with hematologic malignancies can be successfully treated with donor lymphocyte infusion after HLA-matched allogeneic hematopoietic stem cell transplantation. The effect of donor lymphocyte infusion is mediated by donor T cells recognizing minor histocompatibility antigens. T cells recognizing hematopoietic restricted minor histocompatibility antigens may induce selective graft-versus-leukemia reactivity, whereas broadly-expressed antigens may be targeted in graft-versus-host disease., Design and Methods: We analyzed in detail CD8(+) T-cell immunity in a patient with relapsed chronic myelogenous leukemia who responded to donor lymphocyte infusion with minimal graft-versus-host disease of the skin. CD8(+) T-cell clones specific for 4 HLA-B*40:01 restricted minor histocompatibility antigens were isolated which were identified by screening a plasmid cDNA library and whole genome association scanning. Detailed T-cell reactivity and monitoring experiments were performed to estimate the clinical and therapeutic relevance of the novel antigens., Results: Three antigens were demonstrated to be expressed on primary leukemic cells of various origins as well as subtypes of non-malignant hematopoietic cells, whereas one antigen was selectively recognized on malignant hematopoietic cells with antigen presenting cell phenotype. Skin derived fibroblasts were only recognized after pre-treatment with IFN-γ by two T-cell clones., Conclusions: Our data show evidence for different roles of the HLA-B*40:01 restricted minor histocompatibility antigens in the onset and execution of the anti-tumor response. All antigens may have contributed to a graft-versus-leukemia effect, and one minor histocompatibility antigen (LB-SWAP70-1Q) has specific therapeutic value based on its in vivo immunodominance and strong presentation on leukemic cells of various origins, but absence of expression on cytokine-treated fibroblasts.