invariant Natural Killer T cell therapy as a novel therapeutic approach in hematological malignancies.

Invariant Natural Killer T cell therapy is an emerging platform of immunotherapy for cancer treatment. This unique cell population is a promising candidate for cell therapy for cancer treatment because of its inherent cytotoxicity against CD1d positive cancers as well as its ability to induce host CD8 T cell cross priming. Substantial evidence supports that iNKT cells can modulate myelomonocytic populations in the tumor microenvironment to ameliorate immune dysregulation to antagonize tumor progression. iNKT cells can also protect from graft-versus-host disease (GVHD) through several mechanisms, including the expansion of regulatory T cells (Treg). Ultimately, iNKT cell-based therapy can retain antitumor activity while providing protection against GVHD simultaneously. Therefore, these biological properties render iNKT cells as a promising "off-the-shelf" therapy for diverse hematological malignancies and possible solid tumors. Further the introduction of a chimeric antigen recetor (CAR) can further target iNKT cells and enhance function. We foresee that improved vector design and other strategies such as combinatorial treatments with small molecules or immune checkpoint inhibitors could improve CAR iNKT in vivo persistence, functionality and leverage anti-tumor activity along with the abatement of iNKT cell dysfunction or exhaustion.

Extracellular release of damaged mitochondria induced by prehematopoietic stem cell transplant conditioning exacerbates GVHD.

ABSTRACT: Despite therapeutic advancements, graft-versus-host disease (GVHD) is a major complication of hematopoietic stem cell transplantation (HSCT). In current models of GVHD, tissue injury induced by cytotoxic conditioning regimens, along with translocation of microbes expressing pathogen-associated molecular patterns, result in activation of host antigen-presenting cells (APCs) to stimulate alloreactive donor T lymphocytes. Recent studies have demonstrated that in many pathologic states, tissue injury results in the release of mitochondria from the cytoplasm to the extracellular space. We hypothesized that extracellular mitochondria, which are related to archaebacteria, could also trigger GVHD by stimulation of host APCs. We found that clinically relevant doses of radiation or busulfan induced extracellular release of mitochondria by various cell types, including cultured intestinal epithelial cells. Conditioning-mediated mitochondrial release was associated with mitochondrial damage and impaired quality control but did not affect the viability of the cells. Extracellular mitochondria directly stimulated host APCs to express higher levels of major histocompatibility complex II (MHC-II), costimulatory CD86, and proinflammatory cytokines, resulting in increased donor T-cell activation, and proliferation in mixed lymphocyte reactions. Analyses of plasma from both experimental mice and a cohort of children undergoing HSCT demonstrated that conditioning induced extracellular mitochondrial release in vivo. In mice undergoing MHC-mismatched HSCT, administration of purified syngeneic extracellular mitochondria increased host APC activation and exacerbated GVHD. Our data suggest that pre-HSCT conditioning results in extracellular release of damaged mitochondria, which increase alloreactivity and exacerbate GVHD. Therefore, decreasing the extracellular release of damaged mitochondria after conditioning could serve as a novel strategy for GVHD prevention.

Identification of unstable regulatory and autoreactive effector T cells that are expanded in patients with FOXP3 mutations.

Studies of the monogenic autoimmune disease immunodysregulation polyendocrinopathy enteropathy X-linked syndrome (IPEX) have elucidated the essential function of the transcription factor FOXP3 and thymic-derived regulatory T cells (Tregs) in controlling peripheral tolerance. However, the presence and the source of autoreactive T cells in IPEX remain undetermined. Here, we investigated how FOXP3 deficiency affects the T cell receptor (TCR) repertoire and Treg stability in vivo and compared T cell abnormalities in patients with IPEX with those in patients with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy syndrome (APECED). To study Tregs independently of their phenotype and to analyze T cell autoreactivity, we combined Treg-specific demethylation region analyses, single-cell multiomic profiling, and bulk TCR sequencing. We found that patients with IPEX, unlike patients with APECED, have expanded autoreactive T cells originating from both autoreactive effector T cells (Teffs) and Tregs. In addition, a fraction of the expanded Tregs from patients with IPEX lost their phenotypic and functional markers, including CD25 and FOXP3. Functional experiments with CRISPR-Cas9-mediated FOXP3 knockout Tregs and Tregs from patients with IPEX indicated that the patients' Tregs gain a TH2-skewed Teff-like function, which is consistent with immune dysregulation observed in these patients. Analyses of FOXP3 mutation-carrier mothers and a patient with IPEX after hematopoietic stem cell transplantation indicated that Tregs expressing nonmutated FOXP3 prevent the accumulation of autoreactive Teffs and unstable Tregs. These findings could be directly used for diagnostic and prognostic purposes and for monitoring the effects of immunomodulatory treatments.