Bruce Blazar, MD

1. Graft-versus-host disease (GVHD) . GVHD is a multi-organ system disorder in which donor T cells recognize host alloantigens present on antigen-presenting cells and tissues in the context of an inflammatory response. Studies are directed toward identifying and modifying signals that drive or inhibit acute and chronic GVHD generation. These include the analysis of positive costimulatory molecules and negative regulators of the immune response that counterbalance positive costimulation as well as intracellular signaling and metabolic pathways that regulate these responses at the level of the GVHD target organ. We are examining cell-based therapies such as regulatory T cells (see below) in mice and in patients and myeloid-derived suppressor cells (see below). We have also used a newly developed model of chronic GVHD that results from T:B cooperativity, leading to alloantibody and subsequently, collagen deposition, culminating in multi-organ system injury and pulmonary and liver fibrosis. We have tested drugs and cell populations that affect this interaction, many of which have been brought into the clinic, one of which has received FDA approval. For approaches that reduce acute or chronic GVHD in mice, we are assessing their immune competency to malignant cells (to assess graft-versus-leukemia, GVL) and to pathogens.
2. Regulatory cells. A) regulatory T cells (Treg) . Using phosphoproteomics, metabolomics, micro-RNA/mRNA binding partners and flow cytometry, we have identified pathways that can be targeted to upregulate Treg potency in mice and humans. Proof-of-principle has been demonstrated in allogeneic and xenogeneic mouse models . Other studies are focused on genome engineering approaches that should optimize GVHD and autoimmune disease treatment. Knockout, transgenic and conditional inducible strains of mice are utilized along with 2-photon microscopy to identify mechanisms of in vivo suppression. B) Myeloid-derived suppressor cells (MDSC). We have developed techniques to differentiation and active MDSCs from normal hematopoietic sources in mice and humans. Our studies have shown in murine allogeneic GVHD systems that inflammasome activation converts MDSCs into immune stimulatory cells. Knockout of inflammasome components or inflammasome inducers have ameliorated this loss of function. Ongoing studies are examining the production of human MDSCs from inducible pluriopotent stem cells, with or without genome engineering approaches, for mechanistic purposes and potential future clinical trials.
3. T cell generation from induced pluripotent stem cells (IPSCs). In order to understand the optimal requirements for T cell anti-cancer or anti-pathogen responses, we have focused on reprogramming various human cell populations into thymic progenitor cells and mature T cells. Transcriptomics and epigenetics are investigated. Genome modification of IPSCs readily induces chimeric antigen receptor (CAR) expression that directs T cells to lymphoma cells. Using a model that incorporates a CAR used in the clinic for treating B cell malignancies and a transgenic strain that expresses human B cell antigens, cytokine release syndrome and neurotoxicity have been shown. Studies are being examined to explore different approaches to mitigate these side-effects.