Humanized mice for immune checkpoint blockade in human solid tumors.

Immunotherapy, specifically research involving immune checkpoint blockers (ICBs), has become a popular trend in anticancer research over the last three years. Due to the difficulties and often poor translation of results from in-vitro models, in-vivo models have become more relevant than ever. With the discovery of NOD, Prkdcscid , and Il2rγ-/- mutations, patient-derived xenograft (PDX) mouse models were developed, providing an ideal environment for ICBs testing. By implanting a PDX with either CD34+ or peripheral blood mononuclear cells, we can create a human immune system capable of mounting a response against tumor burden. These animal models are currently being used to study molecular mechanisms, test drug efficacy, and trial drug combinations. Others have found use for these humanized mouse models as surrogates to represent otherwise uncommon diseases. Limitations remain with regards to what the models are capable of, but in the short amount of time between the development of these models and heightened interest in ICBs, these mice have already shown utility for future developments in the field of immunotherapy.

The Basics of Artificial Antigen Presenting Cells in T Cell-Based Cancer Immunotherapies.

Adoptive T cell transfer (ACT) can mediate objective responses in patients with advanced malignancies. There have been major advances in this field, including the optimization of the ex vivo generation of tumor-reactive lymphocytes to ample numbers for effective ACT therapy via the use of natural and artificial antigen presenting cells (APCs). Herein we review the basic properties of APCs and how they have been manufactured through the years to augment vaccine and T cell-based cancer therapies. We then discuss how these novel APCs impact the function and memory properties of T cells. Finally, we propose new ways to synthesize aAPCs to augment the therapeutic effectiveness of antitumor T cells for ACT therapy.

Antigen-specific T cell Redirectors: a nanoparticle based approach for redirecting T cells.

Redirection of T cells to target and destroy tumors has become an important clinical tool and major area of research in tumor immunology. Here we present a novel, nanoparticle-based approach to selectively bind antigen-specific cytotoxic T cells (CTL) and redirect them to kill tumors, termed ATR (Antigen-specific T cell Redirectors). ATR were generated by decorating nanoparticles with both an antigen-specific T cell binding moiety, either peptide loaded MHC-Ig dimer or clonotypic anti-TCR antibody, and a model tumor cell binding moiety, anti-CD19 antibody to engage CD19+ tumor cells. ATR stably bind tumor cells and CTL in a dose dependent fashion and stimulate antigen-specific conjugate formation between those cells. ATR induced redirected lysis of tumor cells in vitro, as demonstrated by 51Cr-release killing. In vivo ATR administration led to reduced tumor growth in a SCID/beige human lymphoma treatment model. In summary, ATR represent a novel, nanoparticle based approach for redirecting antigen-specific CTL to kill tumors.

CD47 Enhances In Vivo Functionality of Artificial Antigen-Presenting Cells.

PURPOSE: Artificial antigen-presenting cells, aAPC, have successfully been used to stimulate antigen-specific T-cell responses in vitro as well as in vivo. Although aAPC compare favorably with autologous dendritic cells in vitro, their effect in vivo might be diminished through rapid clearance by macrophages. Therefore, to prevent uptake and minimize clearance of aAPC by macrophages, thereby increasing in vivo functionality, we investigated the efficiency of "don't eat me" three-signal aAPC compared with classical two-signal aAPC. EXPERIMENTAL DESIGN: To generate "don't eat me" aAPC, CD47 was additionally immobilized onto classical aAPC (aAPC(CD47+)). aAPC and aAPC(CD47+) were analyzed in in vitro human primary T-cell and macrophage cocultures. In vivo efficiency was compared in a NOD/SCID T-cell proliferation and a B16-SIY melanoma model. RESULTS: This study demonstrates that aAPC(CD47+) in coculture with human macrophages show a CD47 concentration-dependent inhibition of phagocytosis, whereas their ability to generate and expand antigen-specific T cells was not affected. Furthermore, aAPC(CD47+)-generated T cells displayed equivalent killing abilities and polyfunctionality when compared with aAPC-generated T cells. In addition, in vivo studies demonstrated an enhanced stimulatory capacity and tumor inhibition of aAPC(CD47+) over normal aAPC in conjunction with diverging biodistribution in different organs. CONCLUSIONS: Our data for the first time show that aAPC functionalized with CD47 maintain their stimulatory capacity in vitro and demonstrate enhanced in vivo efficiency. Thus, these next-generation aAPC(CD47+) have a unique potential to enhance the application of the aAPC technology for future immunotherapy approaches.

Sprouty-2 regulates HIV-specific T cell polyfunctionality.

The ability of individual T cells to perform multiple effector functions is crucial for protective immunity against viruses and cancer. This polyfunctionality is frequently lost during chronic infections; however, the molecular mechanisms driving T cell polyfunctionality are poorly understood. We found that human T cells stimulated by a high concentration of antigen lacked polyfunctionality and expressed a transcription profile similar to that of exhausted T cells. One specific pathway implicated by the transcription profile in control of T cell polyfunctionality was the MAPK/ERK pathway. This pathway was altered in response to different antigen concentrations, and polyfunctionality correlated with upregulation of phosphorylated ERK. T cells that were stimulated with a high concentration of antigen upregulated sprouty-2 (SPRY2), a negative regulator of the MAPK/ERK pathway. The clinical relevance of SPRY2 was confirmed by examining SPRY2 expression in HIV-specific T cells, where high levels of SPRY2 were seen in HIV-specific T cells and inhibition of SPRY2 expression enhanced the HIV-specific polyfunctional response independently of the PD-1 pathway. Our findings indicate that increased SPRY2 expression during chronic viral infection reduces T cell polyfunctionality and identify SPRY2 as a potential target for immunotherapy.