Philip William Askenase MD
Professor of Medicine (Immunology)
Our focus is newly recognized extracellular nanovesicles called exosomes (100 nanometers across; one 500th the size of cells) that are made by all cells, present in all fluids and made in some form by all species down to and including bacteria and fungi. Remarkably, they transfer small RNAs between cells, particularly miRNAs, to then function genetically in the acceptor cells. Our system has been CD8+ suppressor T cells that make antigen specific exosomes due to a coating of immunoglobulin light chains that are induced by antigen high dose tolerance to suppress effector T cells. Our initial system was the mouse model of allergic cutaneous contact hypersensitivity dermatitis (poison ivy), but now has been extended to delayed-type hypersensitivity (DTH) to the protein antigen ovalbumin. A remarkable aspect of this system is that these tiny vesicles that contain only 0.2 attoliters carry miRNA at zeptomolar concentration to function in vivo in an endocrine manner to genetically alter the function of distant effector T cells at the site of active responses. This new cell to cell communication system, that seems fundamental to life, has led us to now investigate exosome treatment by the intranasal route where the vesicles cross the dorsal anterior sinus cribriform plate to then pass the blood barrier and strongly inhibit the mouse model of autoimmune multiple sclerosis. Further, we are contemplating use of healing mesenchymal stem cell exosomes for similar treatment of neuropsychiatric diseases, such as autism. It is interesting that basic allergy research on poison ivy has led to consideration of entirely new therapies for multiple sclerosis and autism.
Current ProjectsSeeking to link these basic findings in mice with conditions in humans (asthma, atopic dermatitis), and to dissect out recent discovery that serum complement components, a system of more than 9 labile enzymatic and fragmenting proteins in the blood, also participate in these critical interactions leading to T cell recruitment in cell mediated immunity in vivo; role of RNA in a T cell suppressor factor relevant to hematopoietic cancers--cDNA cloning and identification of the RNA portion of the TsF, determining the biological properties of the cloned TsF RNA, towards eventual therapy of malignancies
The dissection of crucial cellular and molecular interactions guiding the traffic and eventual recruitment of antigen-specific T cells, out of the blood vessels, and into the tissues, at specific sites of immune reactivity, such as allergic responses (asthma) or protective responses, expulsion of helminth worms from the GI tract, or ticks from the skin.
Have identified that micro-mediators, such as serotonin and leukotrienes, released by mediator-containing cells, such as mast cells or platelets, are of crucial importance in alteration of the local vasculature to allow penetration into the tissues by antigen-specific T cells, that arrive and interact with local antigen-presenting cells that present relevant peptides of antigens, causing release of cytokines by the T cells, to mediate local inflammation and allergy, or in contrast, immune protection and resistance.
Extensive Research Description
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 RNA that is a small, double-stranded RNA. We postulate it is a regulatory miRNA (likely in a pre-miRNA), that acts by being transported between cells; from the suppressive T cells to target effector T cells cells via exosomes [suppressor cell secreted nanovesicles (50-100nm) that contain proteins, RNA and miRNA] to suppress immune responses. The effect produced is systematic and thus endocrine in nature. Further, similar suppressive exosomes can be found in the blood serum of mice tolerized to induce the suppressive T cells that release supernatant of TsF RNA in exosomes, and clinically in the blood of patients with cancer, autoimunity, allergy etc. This cell to cell transfer, in a mammalian system. of active genetic information for immunoregulation 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 could act to reverse suppressive miRNA in cancer. This 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. Finally, detection and analysis of exosomes in the blood is a new method of determining the patient’s immune response.