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Haval Shirwan, Ph.D.
Intro | Research
Interests | Biosketch
| Selected Publications | Staff
| Positions Available |
PROGRAM SUMMARY
The long-term objective of Dr. Shirwan's program is to develop novel biologics and clinically applicable protocols for the use of these agents as immunomodulators to i) downregulate the immune system in an antigen-specific manner for the prevention/treatment of autoimmune diseases, and rejection of cell, tissue, and solid organ grafts of allogeneic and xenogeneic origin, ii) upregulate the immune system to combat/destroy infections and tumors.
Effective immune responses are initiated as a result of coordinated interactions among various receptors and ligands on the surface of immune cells. Thus, the ability to express immunological molecules of interest on the surface of cells, tissues, or organs using gene therapy holds great potential as an immunomodulatory approach for the treatment and/or prevention of various immune-based disorders. However, DNA-based therapeutic approaches have several limitations, including, but not limited to, the inefficient expression of proteins of interest, inadvertent genetic modifications in the host by the introduced recombinant DNA, and lack of specificity of expression. Furthermore, DNA-based therapeutic approaches are labor intensive and time consuming. Dr. Shirwan in collaboration with Dr. Yolcu pioneered a novel approach designated as ProtEx™ as an effective and practical alternative to DNA-based gene expression for immunomodulation.
The ProtEx™ technology involves; i) generation of chimeric molecules consisting of core streptavidin (SA) and functional domains of desired immunological ligands, ii) modification of the cell membrane, tissue and/or organ surfaces with biotin, and iii) engineering of biotinylated cells, tissues and/or organs, with SA-chimeric molecules. ProtEx™ is rapid (performed in <2 hrs), efficient (all targeted cells display the protein(s) of interest), safe (does not involve genetic manipulation of the target cells), and allows for the durable (weeks) display of chimeric proteins on the cell surface. In addition, there are three other important technological advances to the ProtEx™ technology. First, chimeric proteins have potent immunomodulatory activities in soluble forms or when displayed on the cell membrane, owing to their ability to exist as oligomers and crosslink their receptors on the surface of immune cells for the transduction of effective immunological signals. Second, several immunological proteins with synergistic functions can be simultaneously displayed on the cell surface at desired levels without impeding cellular functions, thereby augmenting the efficacy of immunomodulation. Third, chimeric proteins can be used as delivery vehicle to target proteins of interest to selected immune cells in vivo for the generation of effective immune responses. Proof-of-principle for the application of ProtEx™ to transplantation and cancer immunotherapy has recently been obtained in preclinical models and human ex vivo studies. The ProtEx™ technology and selected applications are protected by various issued and pending patents.
PROJECTS
A. ENGINEERING CELLS AND TISSUES WITH EXOGENOUS IMMUNOMODUALTORY PROTEINS FOR TOLERANCE INDUCTION TO AUTOANTIGENS, ALLOANTIGENS, AND XENOANTIGENS
Transplantation of cells, tissues, and organs has become an important and effective therapeutic alternative for patients with selected genetically inherited and acquired diseases. The transplantation of grafts between genetically different individuals, however, is limited by our ability to control immunological recognition and rejection of the graft by the recipient. Thus, pharmacological agents are commonly used in immunosuppressive regimens for the prevention of foreign graft rejection. Although these drugs are effective in reducing the severity of rejection episodes, they fail to create a state of permanent graft-specific tolerance. Furthermore, life-long administration of these immunosuppressive agents is associated with end-organ toxicity and increased risk of opportunistic infections and malignancies. The development of clinically applicable approaches that are capable of inducing transplantation tolerance in a donor-specific manner is a prerequisite for life without immunosuppression for graft recipients. The major focus of our research in this area is to engineer donor cells and tissues to display on their surface immunoregulatory proteins for the induction of effective and donor-specific immune tolerance. We are particularly interested in inducing tolerance to solid organ allografts, such as heart, allogeneic and xenogeneic pancreatic islets for the treatment of type 1 diabetes, and hematopoietic stem cells for the establishment of mixed chimerism.
Project 1. Tolerance induction to heart allografts
The major focus of this project is to induce transplantation tolerance using donor cells engineered to display on their surface FasL as an immunoregulatory protein. FasL-induced apoptosis plays a central role in immune homeostasis and in the establishment of central and peripheral tolerance and dysregulation of this system results in a series of pathogenic conditions, including autoimmunity. Consequently, the Fas/FasL system may have great potential for modulating the immune system to induce tolerance to auto, allo, and xeno-antigens for the purpose of preventing/treating autoimmune diseases and transplant rejection. We have recently demonstrated that donor splenocytes engineered to display on their surface a chimeric FasL with streptavidin (SA-FasL) were effective in inducing tolerance to cardiac allografts in a rat model and tolerance was associated with physical elimination of alloreactive T cells followed by induction of CD4+CD25+FoxP3+ Treg cells. The major focus of this project is to delineate molecular and cellular bases of the inducted tolerance, and test the efficacy of this approach in inducing tolerance to solid organs in a nonhuman primate model as a prelude to Phase I clinical trials in humans. We are also generating immunomodulatory proteins with different mechanisms of action from FasL so that they can be used with FasL to further improve the efficacy of this approach for the induction of tolerance.
Project 2. Tolerance to allogeneic and xenogeneic islet grafts for the treatment of Type 1 diabetes
This research project aims to use immunoregulatory proteins, such as SA-FasL, to prevent and/or treat Type 1 diabetes (T1D) using NOD as a model system of the human disease. T1D is a chronic autoimmune disease that targets the insulin-producing b cells in pancreatic islets of Langerhans for destruction, leading to insulin deficiency and hyperglycemia. The pathogenesis of the disease is multifactorial and characterized by the interaction of environmental factors with predisposing genes, most of which are associated with the HLA-DR and DQ loci. The NOD mouse is a widely used animal model for T1D since it shares many features with human T1D. The immunology of T1D is characterized by a spontaneous loss of immunological tolerance to unique pancreatic b cell antigens manifested by the appearance of autoantibodies and T cells reactive to specific islet antigens. Failure to regulate these immunological responses to self-antigens results in infiltration of islets with mononuclear cells (insulitis) which eventually leads to the complete destruction of insulin-producing b cells (diabetes).
Insulin dependence may be treated by pancreas or pancreatic islet transplantation. However, both forms of transplantation confer a relatively poor clinical outcome. Allogeneic islet transplantation to treat diabetes suffers not only from alloreactive, but also autoreactive immunological responses. Both of these reactions have to be overcome for successful allogeneic islet transplantation. The aim of this project is to engineer pancreatic islets to display on their surface immunomodulatory molecules and use the engineered islets alone or in combination with donor cells to induce both allo and auto tolerance for the treatment of T1D. Due to the paucity of donor grafts for human transplantation, we are also focusing on the induction of tolerance to xenogeneic islets using rat-to-mouse and porcine-to-nonhuman primate models.
B. Vaccines
Prophylactic vaccines to various infections agents have been the medical miracle of the 20th century. However, irrespective of significant advances in immunology, the development of effective therapeutic vaccines against cancer and various chronic infections remain to be realized. Unlike prophylactic vaccines, therapeutic vaccines not only need to generate new responses and/or boost the existing responses, but also overcome various immune evasion mechanisms employed by tumors and chronic infections. This may require vaccine formulations that incorporate immunomodulators having pleiotropic functions on cells of innate, adaptive, and regulatory immunity. Although various immunomodulators, such as TLR agonists, heat-shock proteins, and alum, have been used as components of therapeutic cancer vaccines, their efficacy in the clinic has yet to be realized . Given the paramount role costimulation plays in modulating innate, adaptive, and regulatory immunity , we hypothesized that vaccine formulations incorporating costimulatory ligands as immunomodulators may have therapeutic efficacy in cancer and chronic infection settings. Consistent with this notion is the demonstrated therapeutic efficacy of agonistic Abs to costimulatory receptors in various preclinical cancer settings . Although effective, the use of agonistic Abs is associated with severe toxicity in mice and humans. We hypothesize that signaling by natural ligands may have better efficacy and safety as compared to agonistic Abs and focused on 4-1BBL and OX-40L, two members of the TNF family. These two ligands play critical role in augmenting primary immunity and are essential in the establishment of long-term immunological memory. Importantly, these molecules also play critical role in modulating regulatory immunity, such as T regulatory cells, clonal anergy, and ignorance, that serve as a major obstacle for the therapeutic efficacy of the vaccines. Inasmuch as these costimulatory ligands function as membranous proteins and have no/minimal function in soluble forms, we used our ProtEx™ technology to generate recombinant SA-4-1BBL and SA-OX-40L proteins. These molecules are presently being tested as the immunomodulatory component of various vaccine formulations in preclinical models.
Project 3. Therpaeutic vaccine against cancer
Therapeutic vaccines represent attractive alternatives to conventional treatments for the management of cancer, primarily because of their specificity, preventing collateral damage to the host, and ability to induce long lasting immunological memory, which is important for controlling recurrences. In particular, therapeutic vaccines based on well-defined universal tumor associated antigens (TAAs) are attractive because of their ease of manufacturing, storage, transportation, and administration to patients as well as targeting a broad range of cancer types. Regardless of the many advances in vaccinology, the therapeutic potential of cancer vaccines remains to be realized primarily due to three major obstacles. First, TAAs, except virally derived ones, are weakly immunogenic due to self tolerance. Second, tumors evade immunosurveillance by a complex set of immune evasion mechanisms that target innate, adaptive, and regulatory immunity . Third, therapeutic vaccines are generally administered into patients with advanced stage cancer in conjunction with conventional cancer treatments that may have negative impact on the vaccine efficacy. Therefore, the therapeutic efficacy of TAAs-based cancer vaccines will depend on their ability to break tolerance to TAAs, overcome various immune evasion mechanisms, and be compatible with conventional treatments. In this context, vaccine formulations incorporating immunomodulators that target innate, adaptive, and regulatory immunity for the induction of a robust anti-tumor immune response in cancer patients with standard treatments stand the best chance as therapeutic vaccines.
We recently generated a chimeric 4-1BBL with streptavidin (SA-4-1BBL) and demonstrated its potent pleiotropic immune activities in soluble form as component of various vaccines. SA-4-1BBL was more effective than two bench mark toll like receptor agonists and an agonistic antibody to 4-1BB in generating immune responses as the immunomodulatory component of various vaccines and in eradicating established tumors in preclinical settings. Importantly, the efficacy of SA-4-1BBL was realized without sever toxicity associated with the use of agonistic antibody to 4-1BB. These preclinical data served as the basis of a phase I clinical trial for cervical cancer in humans presently being pursued by ApoImmune, Inc., that has exclusive rights to this platform vaccine technology. We are presently testing the efficacy of TAA and SA-4-1BBL-based vaccines in various transplantable and spontaneous preclinical cancer models and investigating cellular and molecular mechanisms responsible for their efficacy.
Project 4. prophylactic/Therpaeutic vaccines against tuberclosis
Tuberculosis is the second leading cause of infectious disease mortality worldwide behind HIV and the leading cause of death in the HIV-infected population. Currently, the only approved vaccine for tuberculosis is Bacillus Calmette-Guerin (BCG), and although fairly effective in reducing disseminated infections in children, successful delivery to more than 3 billion people has clearly failed to halt the escalating modern pandemic. The focus of this NIH-funded project is to use SA-4-1BBL as the immunomodulatory component of a subunit vaccine consisting of TB proteins expressed in acute and chronic phases of the bacteria and test the efficacy of the vaccine for the prevention and treatment of TB in a preclinical rodent model.
Project 5. Universal vaccine against influenza
The potential threat of an influenza pandemic and the use of the virus for bioterrorism are of great. However, despite the likelihood of an emerging pandemic for avian or swine influenza, vaccine stocks are limited and current vaccines may not be effective against newly emerging influenza strains due to genetic alterations in virus genes serving as targets for the immune system. These fears as well as the knowledge that the next pandemic is imminent urges the development of novel vaccines. To be effective, current influenza vaccines must be used prophylactically as they prevent infections by eliciting neutralizing antibodies blocking viral entry and spreading. Therefore, the development of universal vaccines that have cross-protective efficacy against various influenza strains is of a great interest. The focus of this project is to generate subunit vaccines based on conserved viral proteins and SA-4-1BBL as adjuvant. This vaccine concept is aimed at generating both cellular and humoral immune responses with not only prophylactic and therapeutic efficiencies but also cross-reactivity against various influenza strains, including human, swine, and avian.