Rayne H. Rouce

Regulatory B cells are enriched within the IgM memory and transitional subsets in healthy donors but are deficient in chronic GVHD

A subset of regulatory B cells (Bregs) in mice negatively regulate T-cell immune responses through the secretion of regulatory cytokines such as IL-10 and direct cell-cell contact and have been linked to experimental models of autoimmunity, inflammation, and cancer. However, the regulatory function of Bregs in human disease is much less clear. Here we demonstrate that B cells with immunoregulatory properties are enriched within both the CD19(+)IgM(+)CD27(+) memory and CD19(+)CD24(hi)CD38(hi) transitional B-cell subsets in healthy human donors. Both subsets suppressed the proliferation and interferon-γ production of CD3/CD28-stimulated autologous CD4(+) T cells in a dose-dependent manner, and both relied on IL-10 secretion as well as cell-cell contact, likely mediated through CD80 and CD86, to support their full suppressive function. Moreover, after allogeneic stem cell transplantation, Bregs from patients with chronic graft-versus-host disease (cGVHD) were less frequent and less likely to produce IL-10 than were Bregs from healthy donors and patients without cGVHD. These findings suggest that Bregs may be involved in the pathogenesis of cGVHD and support future investigation of regulatory B cell-based therapy in the treatment of this disease.

The Application of Natural Killer Cell Immunotherapy for the Treatment of Cancer.

Natural killer (NK) cells are essential components of the innate immune system and play a critical role in host immunity against cancer. Recent progress in our understanding of NK cell immunobiology has paved the way for novel NK cell-based therapeutic strategies for the treatment of cancer. In this review, we will focus on recent advances in the field of NK cell immunotherapy, including augmentation of antibody-dependent cellular cytotoxicity, manipulation of receptor-mediated activation, and adoptive immunotherapy with ex vivo-expanded, chimeric antigen receptor (CAR)-engineered, or engager-modified NK cells. In contrast to T lymphocytes, donor NK cells do not attack non-hematopoietic tissues, suggesting that an NK-mediated antitumor effect can be achieved in the absence of graft-vs.-host disease. Despite reports of clinical efficacy, a number of factors limit the application of NK cell immunotherapy for the treatment of cancer, such as the failure of infused NK cells to expand and persist in vivo. Therefore, efforts to enhance the therapeutic benefit of NK cell-based immunotherapy by developing strategies to manipulate the NK cell product, host factors, and tumor targets are the subject of intense research. In the preclinical setting, genetic engineering of NK cells to express CARs to redirect their antitumor specificity has shown significant promise. Given the short lifespan and potent cytolytic function of mature NK cells, they are attractive candidate effector cells to express CARs for adoptive immunotherapies. Another innovative approach to redirect NK cytotoxicity towards tumor cells is to create either bispecific or trispecific antibodies, thus augmenting cytotoxicity against tumor-associated antigens. These are exciting times for the study of NK cells; with recent advances in the field of NK cell biology and translational research, it is likely that NK cell immunotherapy will move to the forefront of cancer immunotherapy over the next few years.

The TGF-β/SMAD pathway is an important mechanism for NK cell immune evasion in childhood B-acute lymphoblastic leukemia.

Natural killer (NK) cells are key components of the innate immune system, providing potent antitumor immunity. Here, we show that the tumor growth factor-β (TGF-β)/SMAD signaling pathway is an important mechanism for NK cell immune evasion in childhood B-acute lymphoblastic leukemia (ALL). We characterized NK cells in 50 consecutive children with B-ALL at diagnosis, end induction and during maintenance therapy compared with age-matched controls. ALL-NK cells at diagnosis had an inhibitory phenotype associated with impaired function, most notably interferon-γ production and cytotoxicity. By maintenance therapy, these phenotypic and functional abnormalities partially normalized; however, cytotoxicity against autologous blasts remained impaired. We identified ALL-derived TGF-β1 to be an important mediator of leukemia-induced NK cell dysfunction. The TGF-β/SMAD signaling pathway was constitutively activated in ALL-NK cells at diagnosis and end induction when compared with healthy controls and patients during maintenance therapy. Culture of ALL blasts with healthy NK cells induced NK dysfunction and an inhibitory phenotype, mediated by activation of the TGF-β/SMAD signaling pathway, and abrogated by blocking TGF-β. These data indicate that by regulating the TGF-β/SMAD pathway, ALL blasts induce changes in NK cells to evade innate immune surveillance, thus highlighting the importance of developing novel therapies to target this inhibitory pathway and restore antileukemic cytotoxicity.

Recent advances in T-cell immunotherapy for haematological malignancies.

In vitro discoveries have paved the way for bench‐to‐bedside translation in adoptive T cell immunotherapy, resulting in remarkable clinical responses in a variety of haematological malignancies. Adoptively transferred T cells genetically modified to express CD19 CARs have shown great promise, although many unanswered questions regarding how to optimize T‐cell therapies for both safety and efficacy remain. Similarly, T cells that recognize viral or tumour antigens though their native receptors have produced encouraging clinical responses. Honing manufacturing processes will increase the availability of T‐cell products, while combining T‐cell therapies has the ability to increase complete response rates. Lastly, innovative mechanisms to control these therapies may improve safety profiles while genome editing offers the prospect of modulating T‐cell function. This review will focus on recent advances in T‐cell immunotherapy, highlighting both clinical and pre‐clinical advances, as well as exploring what the future holds.

Forecasting Cytokine Storms with New Predictive Biomarkers

T cells genetically modified with CD19 chimeric antigen receptors have produced impressive clinical responses in patients with refractory B-cell malignancies, but therapeutic responses are often accompanied by cytokine release syndrome (CRS), which can cause significant morbidity and mortality. Teachey and colleagues have identified predictive biomarkers for this complication that may allow testing of earlier intervention with agents such as the IL6 receptor blocker tocilizumab to evaluate whether CRS can be ameliorated without jeopardizing clinical responses. Cancer Discov; 6(6); 579-80. ©2016 AACR.See related article by Teachey et al., p. 664.

Recent advances in the risk factors, diagnosis and management of Epstein-Barr virus post-transplant lymphoproliferative disease

Fifty years after the first reports of Epstein-Barr virus (EBV)-associated endemic Burkitts lymphoma, EBV has emerged as the third most prevalent oncogenic virus worldwide. EBV infection is associated with various malignancies including Hodgkin and non-Hodgkin lymphoma, NK/T-cell lymphoma and nasopharyngeal carcinoma. Despite the highly specific immunologic control in the immunocompetent host, EBV can cause severe complications in the immunocompromised host (namely, post-transplant lymphoproliferative disease). This is particularly a problem in patients with delayed immune reconstitution post-hematopoietic stem cell transplant or solid organ transplant. Despite advances in diagnostic techniques and treatment algorithms allowing earlier identification and treatment of patients at highest risk, mortality rates remain as high as 90% if not treated early. The cornerstones of treatment include reduction in immunosuppression and in vivo B cell depletion with an anti-CD20 monoclonal antibody. However, these treatment modalities are not always feasible due to graft rejection, emergence of graft vs. host disease, and toxicity. Newer treatment modalities include the use of adoptive T cell therapy, which has shown promising results in various EBV-related malignancies. In this article we will review recent advances in risk factors, diagnosis and management of EBV-associated malignancies, particularly post-transplant lymphoproliferative disease. We will also discuss new and innovative treatment options including adoptive T cell therapy as well as management of special situations such as chronic active EBV and EBV-associated hemophagocytic lymphohistiocytosis.

Equal opportunity CAR T cells

In this issue of Blood , Gardner et al report results of a phase 1 trial of 45 children and young adults with relapsed or refractory B-lineage acute lymphoblastic leukemia (ALL) who received a T-cell product of defined CD4/CD8 composition that was genetically modified with a CD19-4-1BB:ζ chimeric antigen receptor (CAR) lentiviral vector. 1

513. Establishment of a Highly Characterized Third-Party Virus-Specific T Lymphocyte Bank for Treatment of EBV+ Lymphoma

Although autologous or donor-derived EBV-specific T cells (EBVSTs) have clinical efficacy for Hodgkin and non-Hodgkin lymphoma, the lengthy manufacturing process and anergy of patient tumor-specific T cells reduce the feasibility of widespread use. An alternative approach is establishment of a pre-made third party bank that can provide access to EBVSTs for almost any patient. We previously evaluated multivirus-specific third-party T cells for refractory viral infections after HSCT. Of 50 recipients, 74% responded, even when T cells were HLA-matched at only a single allele. Although established banks consist primarily of donors from national marrow registries or family members according to HLA genotype, there are many limitations to this approach, including the generation of lines with limited specificity for the targeted antigens. To circumvent these drawbacks, we have generated our bank from blood bank-eligible donors, initially chosen based on racial diversity thus predicted to have HLA haplotypes representative of our diverse patient population and then selected for high specificity for the viral antigens targeted. Donors were subsequently screened for specificity to the EBV Type 2 latency antigens (LMP1/2, EBNA1, and BARF1) with IFN-γ Elispot assays using overlapping peptide libraries (pepmixes) spanning each antigen. The challenge for our study will be the accurate identification of the HLA alleles that restrict the EBV antigen-specific activity of each line to allow optimal assignation to patients with EBV+ lymphoma. To ensure that the best EBVST line is chosen for each recipient, it is important to ensure antigen-specific activity restricted by the alleles shared between donor and recipient. To characterize HLA restriction we use peptides or pepmix-pulsed PHA blasts or LCLs that are HLA matched at a single class I or II allele as target cells in cytotoxicity assays. We then constructed a database in which the HLA restriction of the antigen specificity of each T cell line is listed. The EBVSTs exhibited significant specificity (with >50% of donors recognizing 3 of the 4 antigens) and cytotoxicity to both pepmix-pulsed autologous activated T cells and HLA-matched EBV-lymphoblastoid cell lines that naturally express viral antigens. Based on data from our third party trivirus-specific T cell study, we expect that our projected bank of 30 highly characterized EBVSTs will cover >95% of referred patients (with matching at ≥ 2 class I and/or class II alleles) since our screening strategy ensures that a wide range of HLA haplotypes is covered. Additionally, given the significantly increased virus specificity of our highly characterized donors, we expect to see significant anti-tumor activity. This study will therefore allow us to determine whether third-party T cells can be effective outside the HSCT setting in patients who are not immunocompromised.

Increasing the purity, potency and specificity of ebv-specific T cells to improve the treatment of EBV-positive lymphoma

Meeting abstracts Up to ~40 % of Hodgkin and non-Hodgkin lymphomas carry the Epstein-Barr virus (EBV) genome and express type 2 viral latency proteins (T2LPs) EBNA-1, LMP-1, LMP-2 and BARF-1. EBV specific T cells (EBVSTs) can be generated from the blood of EBV+ individuals, but are usually