Candidate: I have focused my clinical and laboratory training on developing a career as a physician/scientist with expertise in hematology/oncology, hematopoietic stem cell transplantation (HSCT) and human immunology. I completed clinical subspecialty training in hematology/oncology in Australia, and then obtained a PhD studying the biology of human dendritic cells (DCs) with Derek Hart with the goal of utilizing DCs to generate virus- and tumor-specific CD8+ T cell responses in patients with B cell malignancies. My postdoctoral training at the Fred Hutchinson Cancer Research Center (FHCRC) with Stanley Riddell has focused on studies of human CD8+ memory T cells, with the goal of understanding intrinsic qualities of different subsets of memory T cells that might predict their role in immune memory and inflammatory disease. In 2008, I began serving as an Attending Physician on the HSCT service, and in 2010 was appointed an Associate in Clinical Research in the Program in Immunology. Career Objectives: My objectives are to understand the mechanisms that regulate human CD161hi CD8+ memory T cells in normal and perturbed homeostasis and to investigate a role for these cells in graft versus host disease (GVHD) and autoimmunity. Research: In work recently published in Immunity, I investigated how human T cell memory is maintained during cytotoxic chemotherapy for acute leukemia, and identified a subset of self-renewing CD8+ T cells that expresses high levels of ABCB1, enabling them to efflux chemotherapy drugs and provide a persistent reservoir of memory T cells during chemotherapy induced lymphocytopenia. They also express genes, including RORC, and CD161 that are associated with production of IL-17, a highly pro-inflammatory cytokine implicated in the pathogenesis of many autoimmune and inflammatory diseases, including GVHD after HSCT. My work has revealed that the type 17-programmed CD161hi subset comprises a remarkably large, and previously unrecognized, proportion (~22%) of the human CD8+ memory T cell pool, and harbors the entire human Tc17 population. Despite their type 17- transcriptional program, only a minority secretes IL-17 or proliferates to 1CD3 mAb due to regulation of the TCR signaling pathway. TCR signaling pathway regulation can be overcome by provision of costimulation or inflammatory signals, and the nature of those signals dictates the fate of CD161hi cells, resulting in either expansion of cells in the type 17 programmed pool that maintain regulation of TCR signaling or differentiation into IFN-3 secreting Tc1-like effector cells that are no longer restrained by TCR regulation. These data suggest that the CD161hi CD8+ subset is an extraordinarily large reservoir of type 17-programmed memory cells that can be unleashed in a permissive inflammatory environment, potentially resulting in initiation of an inflammatory cascade. Inflammation induced by conditioning chemo-radiotherapy prior to HSCT could provide the necessary initiating signals that cause loss of TCR regulation or differentiation in CD161hi CD8+ T cells and allow them to contribute to the pathogenesis of GVHD.
The specific aims of this proposal are:
Aim 1. To characterize mechanisms regulating TCR signal transduction in CD161hi TCM and TEM CD8+ T cells. These studies will localize the sites of downregulation of TCR signaling in CD161hi CD8+ T cells in healthy individuals, thereby indicating potential sites of dysregulation in inflammatory diseases.
Aim 2. To characterize the recovery and function of CD161hi CD8+ T cells after myeloablative allogeneic HSCT, and determine if this T cell subset is implicated in GVHD. These studies will determine the kinetics of recovery of CD161hi and CD161lo TCM and TEM CD8+ cells after myeloablative allogeneic HSCT, and if CD161hi CD8+ cell numbers in blood or infiltrated tissue are associated with acute GVHD. I will then establish if TCR signaling pathway regulation is altered in HSCT patients compared to healthy individuals and if dysregulation of TCR signaling in CD161hi CD8+ cells from HSCT patients is correlated with GVHD. Career Development and Environment: The mentored K99 phase will allow me to build on the observations made in my preliminary studies of CD161hi CD8+ T cells. Specifically, during the K99 phase I will develop skills that are necessary to study TCR signaling in the uniquely regulated CD161hi subset using lentiviral vectors for gene reconstitution and knock-down studies in primary human T cells. I will complete the K99 studies with guidance from Dr. Riddell and the expert technical consultants, Drs. Tewari and Randolph-Habecker. The data and skills acquired the K99 phase will facilitate analysis of the regulation of CD161hi cells in GVHD in the R00 phase. The skills developed in the K99/R00 phase will lay the foundation for a future R01 application focused on further understanding the role of CD161hi T cells in human inflammatory responses, including autoimmunity. The scientific and clinical environment at FHCRC is ideal for career development and the transition to independence. The Program in Immunology is comprised of four Senior Faculty members, who have a history of productive collaboration within and outside the program. The FHCRC has outstanding scientific leadership, resources, and a superb clinical HSCT program, which will allow the acquisition of samples and enable research collaborations with HSCT clinicians and scientists, and ensure success of the research proposed in my K99/R00 application.
The applicant has identified a new way to isolate and study a large proportion of the immune memory cells that provide protection after vaccination or infection. The memory T cells that the applicant has identified in humans are resistant to chemotherapy, which allows them to survive in chemotherapy-treated patients and contribute to the reconstitution of immune memory to viruses after recovery from chemotherapy. The chemotherapy- resistant cells have the potential to cause profound inflammation, but do not do so in healthy individuals because of stringent regulation. Studies to identify mechanisms that cause a loss of this regulation might provide information on the causes and treatment of graft versus host disease (GVHD), a major complication of blood stem cell transplantation, and other inflammatory or autoimmune diseases. Additional research might allow the development of treatments to increase immunity to infections and cancer after chemotherapy or blood stem cell transplantation.
