Reona Sakemura

Target Antigen Density Governs the Efficacy of Anti–CD20-CD28-CD3 ζ Chimeric Antigen Receptor–Modified Effector CD8+ T Cells

The effectiveness of chimeric Ag receptor (CAR)–transduced T (CAR-T) cells has been attributed to supraphysiological signaling through CARs. Second- and later-generation CARs simultaneously transmit costimulatory signals with CD3ζ signals upon ligation, but may lead to severe adverse effects owing to the recognition of minimal Ag expression outside the target tumor. Currently, the threshold target Ag density for CAR-T cell lysis and further activation, including cytokine production, has not yet been investigated in detail. Therefore, we determined the threshold target Ag density required to induce CAR-T cell responses using novel anti-CD20 CAR-T cells with a CD28 intracellular domain and a CD20-transduced CEM cell model. The newly developed CD20CAR–T cells demonstrated Ag-specific lysis and cytokine secretion, which was a reasonable level as a second-generation CAR. For lytic activity, the threshold Ag density was determined to be ∼200 molecules per target cell, whereas the Ag density required for cytokine production of CAR-T cells was ∼10-fold higher, at a few thousand per target cell. CD20CAR–T cells responded efficiently to CD20-downregulated lymphoma and leukemia targets, including rituximab- or ofatumumab-refractory primary chronic lymphocytic leukemia cells. Despite the potential influence of the structure, localization, and binding affinity of the CAR/Ag, the threshold determined may be used for target Ag selection. An Ag density below the threshold may not result in adverse effects, whereas that above the threshold may be sufficient for practical effectiveness. CD20CAR–T cells also demonstrated significant lytic activity against CD20-downregulated tumor cells and may exhibit effectiveness for CD20-positive lymphoid malignancies.

A Tet-On Inducible System for Controlling CD19-Chimeric Antigen Receptor Expression upon Drug Administration

On-target/off-tumor effects can be problematic if the antigen target for CAR T-cell therapy is also expressed on normal tissue. An inducible CAR expression strategy was used that controlled CAR expression and shows promise in discriminating between tumor and B-cell expression of CD19. T cells genetically modified with a CD19 chimeric antigen receptor (CD19CAR) are remarkably effective against B-cell malignancies in clinical trials. However, major concerns remain regarding toxicities, such as hypogammaglobulinemia, due to B-cell aplasia or severe cytokine release syndrome after overactivation of CAR T cells. To resolve these adverse events, we aimed to develop an inducible CAR system by using a tetracycline regulation system that would be activated only in the presence of doxycycline (Dox). In this study, the second-generation CD19CAR was fused into the third-generation Tet-On vector (Tet-CD19CAR) and was retrovirally transduced into primary CD8+ T cells. Tet-CD19CAR T cells were successfully generated and had minimal background CD19CAR expression without Dox. Tet-CD19CAR T cells in the presence of Dox were equivalently cytotoxic against CD19+ cell lines and had equivalent cytokine production and proliferation upon CD19 stimulation, compared with conventional CD19CAR T cells. The Dox(+) Tet-CD19CAR T cells also had significant antitumor activity in a xenograft model. However, without Dox, Tet-CD19CAR T cells lost CAR expression and CAR T-cell functions in vitro and in vivo, clearly segregating the “On” and “Off” status of Tet-CD19CAR cells by Dox administration. In addition to suicide-gene technology, controlling the expression and the functions of CAR with an inducible vector is a potential solution for CAR T-cell therapy–related toxicities, and may improve the safety profile of CAR T-cell therapy. This strategy might also open the way to treat other malignancies in combination with other CAR or TCR gene–modified T cells. Cancer Immunol Res; 4(8); 658–68. ©2016 AACR. See related Spotlight by June, p. 643.

Integration of humoral and cellular HLA-specific immune responses in cord blood allograft rejection

In allo-stem cell transplantation (SCT), it is unclear whether donor-specific anti-HLA Abs (DSAs) can actually mediate graft rejection or if they are simply surrogate markers for the cellular immunity that causes graft rejection. Here, we first analyzed a case of cord blood allograft rejection in which DSA and cytotoxic T lymphocyte (CTL) specific for donor HLA-B*54:01 were detected at the time of graft rejection. Both the DSA and CTL inhibited colony formation by unrelated bone marrow mononuclear cells sharing HLA-B*54:01, suggesting that the humoral and cellular immune responses were involved in the graft rejection. Interestingly, the DSA and CTL were also detected in cryopreserved pre-transplant patient blood, raising a hypothesis that the presence of anti-HLA Abs could be an indicator for corresponding HLA-specific T cells. We then evaluated the existence of HLA-specific CD8+ T cells in other patient blood specimens having anti-HLA class I Abs. Interferon-γ enzyme-linked immunospot assays clearly confirmed the existence of corresponding HLA-specific T-cell precursors in three of seven patients with anti-HLA Abs. In conclusion, our data demonstrate that integrated humoral and cellular immunity recognizing the same alloantigen of the donor can mediate graft rejection in DSA-positive patients undergoing HLA-mismatched allo-SCT. Further studies generalizing our observation are warranted.

Programmed Death-Ligand 1 on Antigen-presenting Cells Facilitates the Induction of Antigen-specific Cytotoxic T Lymphocytes: Application to Adoptive T-Cell Immunotherapy.

Programmed death-ligand 1 (PD-L1) binds to programmed death-1 (PD-1) on activated T cells and contributes to T-cell exhaustion. PD-L1 expressed on antigen-presenting cells (APCs) could be thought to inhibit the induction of Ag-specific cytotoxic T lymphocytes (CTLs) by transducing negative signal into T cells; however, the roles of PD-L1 on APCs have not yet been well examined. Therefore, we evaluated the roles of PD-L1 on APCs in the induction of Ag-specific CTLs. CD3+ T cells isolated from cytomegalovirus (CMV)-seropositive healthy donors were stimulated with mature dendritic cells pulsed with CMV pp65-derived HLA-restricted peptides in the presence of anti-PD-L1 blocking antibody. Unexpectedly, PD-L1 blockade resulted in a less efficient induction of CMV-specific CTLs, suggesting that PD-L1 play a positive role in the induction of Ag-specific CTLs. For further evaluations and application to adoptive immunotherapy, we generated K562-based artificial APCs, which were retrovirally transduced with HLA class I molecules and various combinations of CD80/86 and PD-L1. K562/HLA+CD80/86+PD-L1 cells produced significantly higher induction of CMV-specific CTLs than K562/HLA or K562/HLA+CD80/86 cells without causing excessive differentiation or functional exhaustion of the induced CTLs, whereas PD-L1 itself did not have a stimulatory effect. Furthermore, only K562/HLA+CD80/86+PD-L1 cells pulsed with HLA-A*24:02-restricted Wilms tumor 1 (WT1) peptide clearly expanded WT1-specific CTLs from healthy donors. Our findings presumed that PD-L1 expressed on APCs along with CD80/86 enhanced the induction of Ag-specific CTLs probably depending on fine-tuning excessive stimulation of CD80/86, and that K562/HLA+CD80/86+PD-L1 cells has therapeutic potential as a novel type of artificial APCs for adoptive immunotherapy.

Simple and efficient generation of virus-specific T cells for adoptive therapy using anti-4-1BB antibody

Although recent studies of virus-specific T-cell (VST) therapy for viral infections after allogeneic hematopoietic stem cell transplantation have shown promising results, simple and less time-intensive and labor-intensive methods are required to generate VSTs for the wider application of VST therapy. We investigated the efficacy of anti-CD28 and anti-4-1BB antibodies, which can provide T cells with costimulatory signals similar in strength to those of antigen-presenting cells, in generating VSTs. When peripheral blood mononuclear cells were stimulated with viral peptides together with isotype control, anti-CD28, or anti-4-1BB antibodies, anti-4-1BB antibodies yielded the highest numbers of VSTs, which were on an average 7.9 times higher than those generated with isotype control antibody. The combination of anti-CD28 and anti-4-1BB antibodies did not result in increased numbers of VSTs compared with anti-4-1BB antibody alone. Importantly, the positive effect of anti-4-1BB antibody was observed regardless of the epitopes of the VSTs. In contrast, the capacity of dendritic cells (DCs) to generate VSTs differed considerably depending on the epitopes of the VSTs. Furthermore, the numbers of VSTs generated with DCs were at most similar to those generated with the anti-4-1BB antibody. Generation of VSTs with anti-4-1BB antibody did not result in excessive differentiation or deteriorated function of the generated VSTs compared with those generated with control antibody or DCs. In conclusion, VSTs can be generated rapidly and efficiently by simply stimulating peripheral blood mononuclear cells with viral peptide and anti-4-1BB antibody without using antigen-presenting cells. We propose using anti-4-1BB antibody as a novel strategy to generate VSTs for adoptive therapy.

High incidence of extensive chronic graft-versus-host disease in patients with the REG3A rs7588571 non-GG genotype

Regenerating islet-derived protein 3 alpha (REG3A) is a biomarker of lower gastrointestinal graft-versus-host disease (GVHD); however, the biological role of REG3A in the pathophysiology of GVHD is not understood. Here, we examined the association between a single nucleotide polymorphism in the REG3A gene, rs7588571, which is located upstream and within 2 kb of the REG3A gene, and transplant outcomes including the incidence of GVHD. The study population consisted of 126 adult Japanese patients who had undergone bone marrow transplantation from a HLA-matched sibling. There was no association between rs7588571 polymorphism and the incidence of acute GVHD. However, a significantly higher incidence of extensive chronic GVHD was observed in patients with the rs7588571 non-GG genotype than in those with the GG genotype (Odds ratio 2.6; 95% confidence interval, 1.1–6.0; P = 0.029). Semi-quantitative reverse transcription PCR demonstrated that the rs7588571 non-GG genotype exhibited a significantly lower REG3A mRNA expression level than the GG genotype (P = 0.032), and Western blot analysis demonstrated that the rs7588571 non-GG genotype exhibited a trend toward lower REG3A protein expression level than the GG genotype (P = 0.053). Since REG proteins have several activities that function to control intestinal microbiota, and since intestinal dysbiosis is in part responsible for the development of GVHD, our findings lead to the novel concept that REG3A could have some protective effect in the pathogenesis of GVHD through the regulation of gut microbiota.

Impact of T-cell chimerism on relapse after cord blood transplantation for hematological malignancies: Nagoya Blood and Marrow Transplantation Group study

Impact of T-cell chimerism on relapse after cord blood transplantation for hematological malignancies: Nagoya Blood and Marrow Transplantation Group study

Testicular invading refractory multiple myeloma during bortezomib treatment successfully treated with lenalidomide: a case report.

Dear Editor, A 64-year-old man was diagnosed with symptomatic multiple myeloma (MM) in June 2009. No extramedullary region including the testes was detected. Serum protein electrophoresis showed IgA-κmonoclonal protein. Durie-Salmon stagewas IIIA and International Staging System stage was II. Treatment was initiated with pulsed dexamethasone and bortezomib (1.3 mg/m) twice weekly with dexamethasone (20 mg on the day of bortezomib administration and the next day).Without any adverse events, he achieved very good partial response (VGPR) after three cycles of bortezomib therapy [1]. Subsequently, he received high-dose melphalan (200 mg/m) followed by autologous stem cell transplantation (ASCT) in November 2009. After ASCT, he was followed up without any therapeutic agents. However, in September 2010, he complained of hip pain, and serum IgA level was elevated to 2,014 mg/dl. As recurrence of MM was diagnosed, we started weekly bortezomib with dexamethasone. The patient soon experienced improvement of symptoms, and serum IgA decreased to normal levels. In July 2011, during weekly bortezomib and dexamethasone, the patient noticed enlargement of his scrotum. Magnetic resonance image revealed enlarged bilateral testes. Serum IgA levels and all other laboratory data were normal. Bilateral orchidectomy was performed in October 2011. Microscopic examination showed positive results for CD56, CD138, and IgA and κ light chain (Fig. 1a, b). The pathological diagnosis wasmetastasis of plasma cell myeloma to the bilateral testes, and the right spermatic cord had positive margins. In November 2011, serum IgA was elevated to 2,304 mg/dl. At relapse of systemicMM including spermatic margins after orchidectomy, a 28-day cycle of lenalidomide (25 mg on days 1–21) and dexamethasone (40 mg on days 1, 8, 15, and 22) was initiated [2]. Serum IgA levels decreased to 1,026 mg/dl and reached a plateau without stump recurrence of the spermatic cord. After 6 cycles of lenalidomide, the patient was treated with cyclophosphamide, vincristine, adriamycin, and dexamethasone (C-VAD) and achieved VGPR after two cycles of C-VAD therapy. In August 2012, he successfully underwent a second ASCT. Two months after ASCT, he started a 28-day cycle of lenalidomide maintenance therapy (10mg on days 1–21) [3]. As of the time of writing, the patient remains alive without recurrence.

Introduction of Genetically-Modified CD3ζ Improves Proliferation and Persistence of Antigen-specific CTLs

It may be safer to improve adoptive T-cell therapy through increased signaling rather than increased antigen affinity of the TCRs. Modifying intracellular signaling enhanced the proliferation and persistence of CTLs while improving antitumor efficacy. The clinical efficacy of T-cell therapies based on T cells transduced with genes encoding tumor-specific T-cell receptors (TCR-T) is related to the in vivo persistence of the T cells. To improve persistence without modifying TCR affinity, we instead modified intracellular signaling, using artificial T cell–activating adapter molecules (ATAM), generated by inserting the intracellular domain (ICD) of activating T-cell signaling moieties into CD3ζ. ATAMs with the ICD of either CD28 or 4-1BB were generated, assembled into the TCR complex as a part of CD3ζ, and enhanced downstream signaling from the supramolecular activation cluster. ATAMs were retrovirally introduced into human CMV-specific or NY-ESO-1–specific TCR-transduced CD8+ T lymphocytes, and downstream functionality was then examined. ATAM-transduced NY-ESO-1 TCR-T cells were also investigated using the U266-xenograft mouse model. ATAMs were successfully transduced and localized to the cell membrane. ATAM-transduced CMV-specific T cells retained their cytotoxic activity and cytokine production against peptide-pulsed target cells without altering antigen-specificity and showed resistance to activation-induced cell death. Upon both single and repeated stimulation, CD3ζ/4-1BB–transduced T cells had superior proliferation to the CD3ζ-transduced T cells in both the CMV-specific and the NY-ESO-1 TCR-T models and significantly improved antitumor activity compared with untransduced T cells both in vitro and in a mouse xenograft model. ATAM-transduced TCR-T cells demonstrated improved proliferation and persistence in vitro and in vivo. This strategy to control the intracellular signaling of TCR-T cells by ATAM transduction in combination with various tumor-specific TCRs may improve the efficacy of TCR-T therapy. Cancer Immunol Res; 6(6); 733–44. ©2018 AACR.

Quantitative assessment of T cell clonotypes in human acute graft-versus-host disease tissues

Owing to the difficulty in isolating T cells from human biopsy samples, the characteristics of T cells that are infiltratinghuman acute graft-versus-host disease (GVHD) tissues remain largely uninvestigated. In the present study, TCR-β deep sequencing of various GVHD tissue samples and concurrent peripheral blood obtained from transplant recipients was performed in combination with functional assays of tissue-infiltrating T cell clones. The T cell repertoire was more skewed in GVHD tissues than in the peripheral blood. The frequent clonotypes differed from tissue to tissue in the same patient, and the frequent clonotypes in the same tissue differed from patient to patient. Two T cell clones were successfully isolated from GVHD skin of a patient. In a cytotoxicity assay, both Tcell clones lysed patient peripheral blood mononuclear cells, but not donor-derived Epstein-Barr virus-transformed lymphoblastoid cells. Their clonotypes were identical to the most and second most frequent T cell clonotypes in the original GVHD skin and accounted for almost all of the skin-infiltrating T cells. These results suggest that human acute GVHD may result from only a few different alloreactive cytotoxic T cell clones, which differ from tissue to tissue and from patient to patient. The characterization of T cells infiltrating human GVHD tissues should be further investigated.