Philip Askenase, MD

T Cell Mediated Suppression via miRNA in Nanovesicle Exosomes Acting Between Cells.

An immensely exciting project in our laboratory stems from our recent discovery that a T cell suppressive factor (TsF) that inhibits effector Th1 and Th2 cells in vivo, contains an a small RNA. We postulated it that it is a regulatory miRNAthat acts by being transported between cells; from the suppressive/regulatory T cells to target effector T cells via carriage in exosomes. These are nanovesicles (50-150 nm) secreted by all cells, present in all fluids and made in some form by all species down to and including fungi and bacteria suppress immune responses. Remarkably, exosomes contain proteins and RNAsthat target other cells to pass signaling and genetic functional information. Subsequent study in our system, employing affinity columns, Solexa sequencing, knock out mice and bioinformatics, ascertained definitively that it is miRNA-150, that is know to participate in other elements of the immune system. The effect produced is systematic and thus endocrine in nature. Thus, suppressive exosomes can be found in the blood serum of mice tolerized to induce the suppressive T cells that release supernatant of miRNA containing exosomes.

Current clinical efforts are to isolate exosomes in the blood of patients, say with cancer to detect markers of particular tumors as part of “liquiddiagnosis” as adjunct or replacement of biopsies. This cell to cell transfer of active genetic information, here for systemic immune regulation in a mammalian system is unprecedented and paradigm breaking. It is likely that interference with this newly recognized mode of antigen-specific T cell suppression can be used therapeutically, or inhibited with antagomirs where indicated. Antagomirs that block the active Exosome-transferred miRNA could oppose oncogenes or reverse immunosuppression in cancer. Exosomes also could create a new pathway in specific immunotherapy that could compliment existing non-specific treatments, resulting in less toxic side effects, greater specificity, and safer use of higher doses of current non-specific drugs (steroids) and biologics (anti-TNF etc). Alternatively, in vitro alteration of syngeneic exosomes for in vivo therapeutic use to alter immune responses, opens an entirely new avenue of possible immunotherapy. In fact, we also are working with healing exosomes of mesenchymal stem cells for treatment of spinal cord injuries. Finally, detection and analysis of exosomes in the blood is a new method of determining the patient’s immune response.

Overall, the goals of these studies are to determine links between these basic findings in mice with diseases in humans, and to dissect out the participation of the recent discoveries that B1 B cells, serotonin, serum complement and iNKT cells, as well as intercellular nanovesicle exosomes passing regulatory miRNAs between cells, participate in critical interactions leading to T cell effector and regulatory functions that may be harnessed for diagnosis and therapy of a variety of diseases, including allergies, autoimmunity and cancer.