CAR-engineered lymphocyte persistence is governed by a FAS ligand/FAS auto-regulatory circuit.

Chimeric antigen receptor (CAR)-engineered T and NK cells can cause durable remission of B-cell malignancies; however, limited persistence restrains the full potential of these therapies in many patients. The FAS ligand (FAS-L)/FAS pathway governs naturally-occurring lymphocyte homeostasis, yet knowledge of which cells express FAS-L in patients and whether these sources compromise CAR persistence remains incomplete. Here, we constructed a single-cell atlas of diverse cancer types to identify cellular subsets expressing FASLG, the gene encoding FAS-L. We discovered that FASLG is limited primarily to endogenous T cells, NK cells, and CAR-T cells while tumor and stromal cells express minimal FASLG. To establish whether CAR-T/NK cell survival is regulated through FAS-L, we performed competitive fitness assays using lymphocytes modified with or without a FAS dominant negative receptor (ΔFAS). Following adoptive transfer, ΔFAS-expressing CAR-T and CAR-NK cells became enriched across multiple tissues, a phenomenon that mechanistically was reverted through FASLG knockout. By contrast, FASLG was dispensable for CAR-mediated tumor killing. In multiple models, ΔFAS co-expression by CAR-T and CAR-NK enhanced antitumor efficacy compared with CAR cells alone. Together, these findings reveal that CAR-engineered lymphocyte persistence is governed by a FAS-L/FAS auto-regulatory circuit.

Blockade of LAG-3 in PD-L1-Deficient Mice Enhances Clearance of Blood Stage Malaria Independent of Humoral Responses.

T cells expressing high levels of inhibitory receptors such as PD-1 and LAG-3 are a hallmark of chronic infections and cancer. Checkpoint blockade therapies targeting these receptors have been largely validated as promising strategies to restore exhausted T cell functions and clearance of chronic infections and tumors. The inability to develop long-term natural immunity in malaria-infected patients has been proposed to be at least partially accounted for by sustained expression of high levels of inhibitory receptors on T and B lymphocytes. While blockade or lack of PD-1/PD-L1 and/or LAG-3 was reported to promote better clearance of Plasmodium parasites in various mouse models, how exactly blockade of these pathways contributes to enhanced protection is not known. Herein, using the mouse model of non-lethal P. yoelii (Py) infection, we reveal that the kinetics of blood parasitemia as well as CD4+ T follicular helper (TFH) and germinal center (GC) B cell responses are indistinguishable between PD-1-/-, PD-L1-/- and WT mice. Yet, we also report that monoclonal antibody (mAb) blockade of LAG-3 in PD-L1-/- mice promotes accelerated control of blood parasite growth and clearance, consistent with prior therapeutic blockade experiments. However, neither CD4+ TFH and GC B cell responses, nor parasite-specific Ab serum titers and capacity to transfer protection differed. We also found that i) the majority of LAG-3+ cells are T cells, ii) selective depletion of CD4+ but not CD8+ T cells prevents anti-LAG-3-mediated protection, and iii) production of effector cytokines by CD4+ T cells is increased in anti-LAG-3-treated versus control mice. Thus, taken together, these results are consistent with a model in which blockade and/or deficiency of PD-L1 and LAG-3 on parasite-specific CD4+ T cells unleashes their ability to effectively clear blood parasites, independently from humoral responses.

Where Do Soldiers Really Come From? A Faculty Development Workshop on Veteran-Centered Care.

PROBLEM: Addressing the medical concerns of veterans in both civilian health care systems and the Veterans Affairs (VA) health care system, where staff are familiar with issues of military reintegration, remains difficult but is increasingly important. APPROACH: In 2013, the authors developed and implemented a faculty development workshop for practicing clinicians using the documentary Where Soldiers Come From. The workshop included topics on unconscious bias, the service member trajectory, health care disparities, and strategies for overcoming barriers to treating veterans with posttraumatic stress disorder and traumatic brain injury. The workshop engaged faculty in the following active-learning techniques: images in education; trigger video; critical thinking and reflective writing; think-pair-share; and large-group discussion. The workshop has been conducted at three locations with 46 health care professionals. OUTCOMES: Thirty-one of 37 (84%) participants who completed the workshop evaluation were VA employees. The evaluation results show 25/32 (78.1%) participants indicated the workshop activities changed their knowledge, attitudes, and/or skills; 22/34 (64.7%) stated they had a better understanding of how to develop a care plan for veterans; and 27/34 (79.4%) stated they gained a better understanding of how to prepare for issues around returning veterans. NEXT STEPS: To address the issue of veteran-centered care education more broadly, the authors have developed a massive open online course for health professionals, using most of the content from this workshop, which will be offered in spring 2016. Another important next step will be to deliver this workshop to and collect evaluation data from non-VA providers.

BTLA is a lymphocyte inhibitory receptor with similarities to CTLA-4 and PD-1.

During activation, T cells express receptors for receiving positive and negative costimulatory signals. Here we identify the B and T lymphocyte attenuator (BTLA), an immunoglobulin domain-containing glycoprotein with two immunoreceptor tyrosine-based inhibitory motifs. BTLA is not expressed by naive T cells, but it is induced during activation and remains expressed on T helper type 1 (T(H)1) but not T(H)2 cells. Crosslinking BTLA with antigen receptors induces its tyrosine phosphorylation and association with the Src homology domain 2 (SH2)-containing protein tyrosine phosphatases SHP-1 and SHP-2, and attenuates production of interleukin 2 (IL-2). BTLA-deficient T cells show increased proliferation, and BTLA-deficient mice have increased specific antibody responses and enhanced sensitivity to experimental autoimmune encephalomyelitis. B7x, a peripheral homolog of B7, is a ligand of BTLA. Thus, BTLA is a third inhibitory receptor on T lymphocytes with similarities to cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) and programmed death 1 (PD-1).