Immune modulation to improve stem cell engraftment

Funding Type: 
Transplantation Immunology
Grant Number: 
RM1-01711
ICOC Funds Committed: 
$0
Stem Cell Use: 
Embryonic Stem Cell
Cell Line Generation: 
Embryonic Stem Cell
Public Abstract: 
Stem cells can give rise to many different types of cells and tissues in our body. Therefore, stem cell transplantation has been considered as a promising alternative to current therapeutic approaches in treating cancer and autoimmune diseases. The premise upon which stem cell treatment is based is that replenishment of diseased or destroyed tissues with cells derived from transplanted stem cells would prevent the progression of or potentially cure disease. However, similar to what occurs in organ transplantation, most if not all available sources for stem cells are from individuals of distinct genetic background. Consequently, the patient receiving stem cell transplantation typically develops a harmful immune response that attacks and destroys the transplanted stem cells or their derivatives. The development of novel methods to overcome such harmful immune responses becomes necessary before a successful stem cell based therapy for diseases, such as cancer or autoimmune diseases, can be applied clinically. Recent developments in research suggest that development of cancer or autoimmune diseases could be due to an imbalance in the immune system. As such, (re)establishing the balance in the immune system may hold great promise for prevention, intervention and cure of disease. Important findings in immunology in the past few years showed that a specialized population of immune cells, called regulatory T cells, functions by regulating other immune cells and, in turn, the body’s immune response. We hypothesize that these cells can potentially be used to modulate both immunity and autoimmunity, and consequently the direction of the body’s immune responses. We and others have shown that regulatory T cells may inhibit autoimmune diseases such as type 1 diabetes and participate in the regulation of tumor development. The purpose of our proposed studies is to determine whether regulatory T cells can also be used to overcome the immunological barriers imposed by patients receiving treatment, and re-balance the immune system in order to provide an environment that is much more suitable for stem cell grafts. It is expected that, for cell replacement therapy, regulatory T cells can induce immune tolerance to promote acceptance of stem cells allowing their growth and replacement of damaged cells in patients and leading to disease cure.
Statement of Benefit to California: 
More than 1 million Californians have a history of cancer, and an estimated nearly 150,000 new cases will be diagnosed in 2010. In addition, autoimmune diseases such as type 1 diabetes and multiple sclerosis, also affect hundreds of thousands of Californians every year. These life-threatening diseases result in deteriorating health conditions and have devastating effects in terms of patient quality of life. While the heavy emotional, physical and financial impact of these diseases is felt by patients and their families, a significant economic burden is also felt by the State, as treatment and care of these patients costs California billions of dollars every year. Additional losses are incurred by the private and public sectors resulting from reduced worker productivity, absence from work and loss of future earnings. The rising cost of medical care is an additional factor underscoring the critical need to develop novel therapies to prevent and treat patients with on-going autoimmune disease. Stem cell transplantation is a promising alternative to current therapeutic approaches in treating cancer and autoimmune disease patients, due to the potential for stem cells to develop into many different types of cells and tissues in the body. Although promising, engraftment of stem cells, as well as cells or tissues derived from stem cells, still suffer from immune or autoimmune attacks and subsequent destruction from the patient’s own immune system, resulting in potential treatment failure or the need for extended patient care. Recent developments in research have suggested that development of cancer or autoimmune diseases could be due to an imbalance in the immune system. It is likely that (re)establishing the balance of the immune system may hold great promise in both prevention and intervention of the diseases. The proposed studies using T cells with potent regulatory function are expected to achieve this goal by inducing active immune tolerance in patients. Should our proposed studies be successful, our results will provide a solid base to facilitate rapid translation of our findings from laboratory to clinics, overcoming the immunological barriers imposed by host patients, with significant medical and economic benefits to Californians in terms of effective treatment of cancer and autoimmune diseases.
Progress Report: 
  • A key limitation in transplanting human embryonic stem cell (hESC)-derived cells remains their potential to elicit a host immune response with subsequent graft rejection due to immune mismatch between host and donor cells. In order to realize the enormous clinical promise of hESCs, novel cell lines capable of evading immune rejection by immunocompetent hosts are desperately needed. Our team has been focused on addressing this critical unmet need, and has had preliminary success in developing and validating an immune override mechanism for human adult stem cells and somatic cells. In the first year of this 3-year project, our main objective was to create a novel non-viral-based gene delivery construct that contains an enhanced red fluorescent protein in combination with an engineered tolerogenic molecule that confers immune protection to cells expressing it on their extracellular membranes. In Q3 of the first budget period, we succeeded in developing the full non-viral-based gene constructs. In total, we have 5 control and 5 tolerogenic gene constructs in our inventory. In the remaining portion of the first budget period, we proceeded to introduce this gene construct into hESCs utilizing a special technique called nucleofection. Through this process, we have developed 11 control cell lines, at least 2 of which appear positive for the fluorescent marker. Expression of this marker ensures that we can track microscopically those hESCs which have integrated the delivered gene constructs into their genome. Moreover, we have succeeded in developing 6 hESC tolerogenic lines, at least 3 of which appear positive for the fluorescent marker. In budget period 2, we will continue to characterize the clones to determine their viability as stably expressing hESC lines as well as whether the engineered override mechanism leads to immune tolerance in a series of in vitro studies. We believe that the progress achieved in the first budget period provides the basis for creating a platform immune tolerant hESC technology that can be employed for the future development of regenerative medicine and curative therapies.
  • A key limitation in transplanting human embryonic stem cell (hESC)-derived cells remains their potential to elicit a host immune response with subsequent graft rejection due to immune mismatch between host and donor cells. In order to realize the enormous clinical promise of hESCs, novel cell lines capable of evading immune rejection by immunocompetent hosts are desperately needed. Our team has been focused on addressing this critical unmet need, and has had preliminary success in developing and validating an immune override mechanism for human adult stem cells and somatic cells. In the second year of this 3-year project, our main objective was to assess the efficacy of our novel non-viral-based gene delivery construct containing an engineered tolerogenic molecule that confers immune protection to cells expressing it on their extracellular membranes. Herein, we report that expression of our tolerogenic molecule was stable through upto 40 passages in human embryonic stem cells and that hESCs retained an immunoprivileged phenotype in vitro as evidenced by their ability to avoid natural killer cytotoxicity and reduce T cell alloproliferation. Furthermore, expression of the construct was stable during differentiation of hESCs into epidermal progenitor cells. These cells also showed an impressive dampending of natural killer cytotoxicity and T cell alloproliferation. This confirms that our approach is robust in vitro during pluripotent division and during differentiation, both of which are required for creation of a clinical product. We believe that the progress achieved in the second budget period provides the basis for creating a platform immune tolerant hESC technology that can be employed for the future development of regenerative medicine and curative therapies.
  • In this period, we were able to transplant engineered human embryonic stem cells expressing an immune tolerance gene into mice with a human immune system to determine whether they survive immune rejection. We observed no rejection of these engineered human embryonic stem cells. The engineered hESCs also were observed to maintain their pluripotency into all 3 germ layers. Histological studies showed that the engineered gene is expressed in all 3 germ layers within the teratomas that formed. Current experiments remain underway to answer whether epidermal stem cells derived from these engineered cells will be rejected in the same animal model.

© 2013 California Institute for Regenerative Medicine