The development of stem cell-based gene therapies is inherently complex due to challenges in understanding and controlling both the therapeutic agents themselves and how the engineered cells interact with the host and pathogens. We are interested in developing and employing novel high-throughput, quantitative biology tools to investigate therapeutically engineered cells and their interactions with pathogens in the body. We use both “wet-lab” and “dry-lab” approaches to study the blood system and viral pathogenesis in gene therapy settings at the individual cell and entire system levels. The goal is to make stem cell therapy more predictable and efficacious.
Understanding Requirements for Curing HIV/AIDS with Stem Cell Gene Therapy
Anti-HIV gene therapy is a new treatment paradigm that can provide lifelong protection against HIV‑1 infection. The basic principle is to genetically modify stem cells such that the progeny of the engineered cells, including CD4+ T-cells and macrophages, are resistant to HIV-1 infection. The study of the “Berlin patient” – the only case so far cured of HIV after allogeneic transplantation with HIV resistant CCR5Δ32 donor cells (with a 32 bp deletion in the HIV-1 co-receptor, CCR5) – has generated tremendous hope for this new therapy: to date, the patient’s HIV remains completely undetectable. Multiple clinical trials for anti-HIV gene therapy are currently ongoing in the United States. The success of such therapy is dependent upon achieving sufficient levels of therapeutic gene modification to protect the immune system against HIV-1. From the Berlin patient case study, it appears that 100% repopulation by CCR5Δ32 cells cures HIV-1. However, the critical question of whether a less-than-maximal transplant repopulation level can provide full or partial protection from HIV-1 has not been addressed experimentally or theoretically. We are interested in investigating the temporal and spatial dynamics of anti-HIV-engineered hematopoietic stem cells (HSCs) and T-cells using nonhuman primate and murine models of anti-HIV gene therapy. We hypothesize that for HSC-based anti-HIV gene therapy, there exists a critical T-cell repopulation threshold that must be exceeded for the immune system to be fully protected from HIV infection. Establishing and understanding the parameters for determining this threshold is critical to the development of transplant protocols that make repopulation with gene-engineered cells therapeutically effective for preventing the progression of or curing HIV-1.
Understanding the Stem Cell-Like T-Cells in Anti-HIV Therapy Settings
Recent discoveries about the extensive self-renewal and multipotent properties of stem cell-like T-cells, including the T-memory stem cell (TSCM) and IL-17-secreting Th17, have opened new avenues for immunotherapy against HIV/AIDS and advanced cancers. Interestingly, research suggests that these potentially useful gene delivery vehicles may also be a major barrier to the elimination of HIV in patients insofar as they appear to serve as a long-term reservoir of latent HIV-1, a stubborn aspect of HIV infection that necessitates a life-long drug treatment. Thus these cells are emerging as a major therapeutic target in patients with HIV-1. The goal of investigating these cells in an anti-HIV therapy setting is twofold: (1) to understand the basic biology of TSCM and Th17 in the presence of HIV-1 and (2) to examine the safety and efficacy of these cells as a gene-delivery vehicle for long-term immunotherapy for HIV/AIDS or advanced cancers. We use animal models to study (i) the effects of integrated HIV-1 DNA molecules (both replication-competent and replication-incompetent forms) upon cellular functions, and (ii) behavior patterns of T-cells (HIV-1 protected and unprotected) and (iii) the inherited or predetermined factors underlying the cellular behaviors. We will analyze tissue samples from HIV-1 infected patients to characterize latently infected T-cells in various anatomic sites.
Multiscale Modeling – Connecting Genes to a Single Cell, Groups of Cells and Their Coordinated Behaviors in the Blood System.
The blood system is complex because it operates at multiple levels (or scales): molecular, cellular, tissue, and environmental. Physical and chemical laws have been applied to predict blood diseases and treatment outcomes, but limitations are frequently encountered because most current models work on a single scale (e.g., cellular or molecular) and are based on datasets that do not take the cellular heterogeneity and multicellular communications into account. We are interested in developing a new high-throughput genetic screening system that can quantify the cell/tissue-level consequences resulting from gene-level perturbations of stem cells. Individual genes will be tested in a high-throughput fashion using cellular barcoding technologies and transgenic animal models for clonal-level tracking of gene modified stem cells and their progeny cells over time in various tissues and organs. The ultimate goal is to develop a mutiscale, quantitative model of the blood system that will be useful for both basic biology and clinical studies.