Annette M. Marleau

Exosome removal as a therapeutic adjuvant in cancer

Exosome secretion is a notable feature of malignancy owing to the roles of these nanoparticles in cancer growth, immune suppression, tumor angiogenesis and therapeutic resistance. Exosomes are 30–100 nm membrane vesicles released by many cells types during normal physiological processes. Tumors aberrantly secrete large quantities of exosomes that transport oncoproteins and immune suppressive molecules to support tumor growth and metastasis. The role of exosomes in intercellular signaling is exemplified by human epidermal growth factor receptor type 2 (HER2) over-expressing breast cancer, where exosomes with the HER2 oncoprotein stimulate tumor growth and interfere with the activity of the therapeutic antibody Herceptin®. Since numerous observations from experimental model systems point toward an important clinical impact of exosomes in cancer, several pharmacological strategies have been proposed for targeting their malignant activities. We also propose a novel device strategy involving extracorporeal hemofiltration of exosomes from the entire circulatory system using an affinity plasmapheresis platform known as the Aethlon ADAPT™ (adaptive dialysis-like affinity platform technology) system, which would overcome the risks of toxicity and drug interactions posed by pharmacological approaches. This technology allows affinity agents, including exosome-binding lectins and antibodies, to be immobilized in the outer-capillary space of plasma filtration membranes that integrate into existing kidney dialysis systems. Device therapies that evolve from this platform allow rapid extracorporeal capture and selective retention of target particles < 200 nm from the entire circulatory system. This strategy is supported by clinical experience in hepatitis C virus-infected patients using an ADAPT™ device, the Hemopurifier®, to reduce the systemic load of virions having similar sizes and glycosylated surfaces as cancer exosomes. This review discusses the possible therapeutic approaches for targeting immune suppressive exosomes in cancer patients, and the anticipated significance of these strategies for reversing immune dysfunction and improving responses to standard of care treatments.

T cell homeostasis in tolerance and immunity.

The size of the peripheral T cell pool is remarkably stable throughout life, reflecting precise regulation of cellular survival, proliferation, and apoptosis. Homeostatic proliferation refers to the process by which T cells spontaneously proliferate in a lymphopenic host. The critical signals driving this expansion are “space,” contact with self‐major histocompatibility complex (MHC)/peptide complexes, and cytokine stimulation. A number of studies have delineated an association between T cell lymphopenia, compensatory homeostatic expansion, and the development of diverse autoimmune syndromes. In the nonobese diabetic mouse model of type 1 diabetes, lymphopenia‐induced homeostatic expansion fuels the generation of islet‐specific T cells. Excess interleukin‐21 facilitates T cell cycling but limited survival, resulting in recurrent stimulation of T cells specific for self‐peptide/MHC complexes. Indeed, data from several experimental models of autoimmunity indicate that a full T cell compartment restrains homeostatic expansion of self‐reactive cells that could otherwise dominate the repertoire. This review describes the mechanisms that govern T cell homeostatic expansion and outlines the evidence that lymphopenia presents a risk for development of autoimmune disease.

Cord blood in regenerative medicine: do we need immune suppression?

Cord blood is currently used as an alternative to bone marrow as a source of stem cells for hematopoietic reconstitution after ablation. It is also under intense preclinical investigation for a variety of indications ranging from stroke, to limb ischemia, to myocardial regeneration. A major drawback in the current use of cord blood is that substantial morbidity and mortality are associated with pre-transplant ablation of the recipient hematopoietic system. Here we raise the possibility that due to unique immunological properties of both the stem cell and non-stem cell components of cord blood, it may be possible to utilize allogeneic cells for regenerative applications without needing to fully compromise the recipient immune system. Issues raised will include: graft versus host potential, the immunogeneicity of the cord blood graft, and the parallels between cord blood transplantation and fetal to maternal trafficking. The previous use of unmatched cord blood in absence of any immune ablation, as well as potential steps for widespread clinical implementation of allogeneic cord blood grafts will also be discussed.

Autologous stromal vascular fraction therapy for rheumatoid arthritis: rationale and clinical safety

Advancements in rheumatoid arthritis (RA) treatment protocols and introduction of targeted biological therapies have markedly improved patient outcomes, despite this, up to 50% of patients still fail to achieve a significant clinical response. In veterinary medicine, stem cell therapy in the form of autologous stromal vascular fraction (SVF) is an accepted therapeutic modality for degenerative conditions with 80% improvement and no serious treatment associated adverse events reported. Clinical translation of SVF therapy relies on confirmation of veterinary findings in targeted patient populations. Here we describe the rationale and preclinical data supporting the use of autologous SVF in treatment of RA, as well as provide 1, 3, 6, and 13 month safety outcomes in 13 RA patients treated with this approach.

Therapeutic use of Aldara™ in chronic myeloid leukemia

The potent clinical responses seen in patients with chronic myeloid leukemia (CML) after administration of donor-specific lymphocytes, as well as the correlation between the presence of antigen specific T cells and prolonged remission in these patients, suggests a role for the immunological control of CML. Here we propose Aldara™, a clinically used formulation of imiquimod, as an agent for augmenting immune responses to CML antigens. Our proposition is based upon 3 tenets: 1) Endogenous dendritic cells (DC) of CML patients, which are known to be derived from the malignant clone, express and present various leukemic antigens; 2) CML-antigen reactive T cell clones exist in the patient but in many situations are ineffectively stimulated to cause significant hematological responses; and 3) Antigen presentation by mature, activated DC, which endogenously express CML-antigens may endow the pre-existing ineffective T cell responses with ability to control CML progression. The practical use of Aldara™ as a localized activator of DC in the context of present day leukemic therapeutics, as well as various properties of this unique immune modulator will be discussed.