Engineering Immune Cells To Stop Autoimmune Attacks
Todd Brusko, Ph.D. — University of Florida
Type 1 diabetes (T1D) occurs from a breakdown in immune tolerance, resulting in the loss of pancreatic β-cells by a persistent autoimmune attack.
Immunomodulatory agents that transiently deplete T cells (anti-CD3) or B cells (Rituximab) have shown only temporary efficacy. In addition, traditional vaccine strategies providing autoantigen alone, such as that employed in the DPT-1 trial failed to adequately block ongoing β-cell immunity. Thus, a new treatment strategy that is both potent and durable is needed to effectively halt the ongoing attack in T1D. Previous studies have focused on the capacity of regulatory T cells (Tregs) to restore tolerance in T1D. This notion is based on the principle that treatment with Tregs in animal models leads to the induction of long-term tolerance and preservation of endogenous β-cell mass. Here, we propose to develop a nanoparticle (NP) vaccine using the biomaterial poly(lactic co-glycolic acid) (PLGA) to be used in combination with a Treg adoptive cell therapy approach. We hypothesize that this modified Treg cell therapy product will augment the stability and efficacy of this cellular therapeutic. In turn, this bolstered therapy will directly combat the ongoing autoimmune response and lead to durable and long-term tolerance to coupled autoantigens through the process of infectious tolerance.
My project has been fully funded, but I invite you to watch my video!
This novel approach is interdisciplinary in nature (joining the fields of immunology and biomaterials engineering), and is designed with clinical translation in mind. Specifically, this project proposes to generate an autologous cell therapy product capable of restoring tolerance and averting autoimmune T1D. My laboratory has extensive experience in Tregs and within the field of immune regulation in autoimmunity. We expect this funding will provide essential proof-of-principal data regarding this vaccine approach.
My interest and connection to diabetes research was cultivated very early in my career by interactions with exceptional mentors (Mark Atkinson and Jeffrey Bluestone) who have spent their entire careers dedicated to finding a cure for type 1 diabetes. I am personally fascinated by the immune system and its capacity for both specificity and control. This fascination has led my studies to focus on what goes wrong in the immune system of individuals who develop type 1 diabetes.
Beyond my scientific interests, I have been fortunate to be actively engaged with patients and advocacy groups throughout my career. Interacting with patients and parents is the greatest motivator to have an impact on the disease process, whether that involves a prevention or cure. To this day, I still encourage all of my trainees and employees to engage in benefit walks, bike rides, lab tours, and educational activities. I feel incredibly fortunate to conduct research, teach, and work toward developing novel therapies to positively impact the lives of patients with type 1 diabetes.
I am a Gator – I bleed orange and blue. I spent my undergraduate and graduate years here at the University of Florida where I am currently faculty. I conducted my post-doctoral training at the University of California, San Francisco.
I grew up in Seminole, FL. Seminole is a small town close to the Tampa/St. Pete area about five minutes from the Gulf of Mexico and beaches.
I have four young children so they are the focus of much of my time outside of work. When, and if I get any spare time, I enjoy trying to stay active outside biking, golfing, and fishing.
For more information on me and my laboratory, please visit: http://bruskolab.diabetes.ufl.edu
Recent Status Updates
Submitted by Dr. Todd Brusko on Mon, 02/15/2016 – 04:59
Type 1 diabetes (T1D) results from the autoimmune destruction of pancreatic b cells. Prior animal model studies have demonstrated that a rare population of white blood cells, termed regulatory T cells (so called Tregs), can prevent and in certain contexts, even reverse the disease process immediately at onset. The field has addressed the challenges associated with how to isolate and grow these cells to therapeutic levels, yet there remain hurdles regarding how best to facilitate long-term engraftment of Tregs when returned to a patient.
The overall goal of our DRC supported project was to create a technology platform that would enable an optimized Treg cell therapy for the treatment of type 1 diabetes. Our technology involved the delivery of a key growth factor interleukin-2 (IL-2) to Treg. This growth factor was encapsulated in the form of nanoparticles (NP) to the surface of Tregs to facilitate extended release. Over the term of our award, we made significant progress toward the execution of our experimental aims. The key milestones achieved, and outline of areas that require further development are summarized below:
- Manufacturing of IL-2 loaded NP – We hypothesized that the localized delivery of IL-2 to Tregs would be advantageous over the high doses of IL-2 that would need to be given systemically to restore immune regulation and support Treg cell engraftment. Therefore, we set out to manufacture biodegradable nanoparticles that would release the Treg growth and survival factor IL-2 for binding to Treg cell surfaces. For this purpose, we effectively manufactured NPs from the same material that FDA-approved dissolvable surgical sutures are manufactured from (known as PLGA). This approach resulted in nearly uniform creation of NPs (of ~300 nanometers) that could be effectively loaded with Treg cell growth factors. Our studies measured the efficiency of drug loading and release from these NPs.
- Conjugation of NP to Tregs – Once we had effectively manufactured NPs with our desired properties, we next set out to find a method to bind these particles to the surface of a living cell. Using a series of different surface chemistries, we were able to effectively bind NPs to the Treg cell surface and visualize this with microscopy. When NP were loaded with a fluorescent dye, we were able to quantify the number of NPs bound to the cell surface.
- Demonstration of biological activity of encapsulated IL-2—We next set out to determine if the IL-2 growth factor was still functional when conjugated to the surface of Tregs. To address these questions, we looked for markers of cell viability and signaling from the specific receptor molecule. These studies resulted in several essential findings; 1) the IL-2 loaded is active and effectively binds to the receptor of interest leading to downstream signaling, and 2) binding of IL-2 NPs was optimal for cell survival in comparison to NPs loaded with an irrelevant control protein.
- Animal models to demonstrate therapeutic efficacy—The ultimate test of our technology is whether it can positively impact a disease process. For our studies, we chose two different disease models in which to test our therapy. First, we set to test the effectiveness of mouse Tregs conjugated with IL-2 NPs in the context of the animal model of T1D, the non-obese diabetic (NOD) mouse. At the time of this writing, these studies are still ongoing. Secondly, we set out to test the effectiveness of human IL-2 conjugated NPs in an animal model of graft versus host disease. In this model, an immunodeficient mouse is engrafted human immune cells. Eventually, the human immune system recognizes the mouse tissues as “foreign” and begins to mount an inflammatory immune response against the host. In this system, Tregs play an important role in controlling this inflammation and tissue damage. Thus, we tested if IL-2 NPs conjugated to human Tregs would be more effective at controlling inflammation than NPs loaded with an irrelevant control protein. Excitingly, our initial data do support the notion of improved engraftment and function of IL-2 conjugated Tregs. These findings offer critical proof-of-principle data that our approach warrants further study and optimizations for therapeutic testing.
- Challenges and Future Directions— Our technology is designed to target and correct the underlying cause of autoimmune disease by restoring immune tolerance. Therefore, it is intended to impact the disease process in those at risk for T1D or who are close to onset and exhibit some residual b cell mass and function. Given our success loading bioactive IL-2, this project raises the potential to load and conjugate additional compounds or growth factors that might restore b cell mass and function. In this manner, Tregs with their inherent tissue homing capabilities could be used as living “smart drugs” to deliver critical compounds needed to impact the disease process in the pancreas.
In sum, the funding provided by the DRC was essential in jump starting this project and for generating the proof-of-concept data that will be needed for the next steps toward validation and clinical translation. We wish to extend our deepest gratitude to the donors and the support staff of the DRC for making this project a reality.
Meet our staff and collaborators
Submitted by Dr. Todd Brusko on Thu, 01/08/2015 – 08:17
The Brusko lab is incredibly grateful for the donation we received to drive this exciting research project forward. Conducting research on this scale is a team effort. As we get started, I would like to begin by introducing some of the key staff and collaborators that will help us to reach our goals. Within the Brusko Laboratory, the project lead will be a PhD candidate within the UF College of Medicine Judit Cserny. http://bruskolab.diabetes.ufl.edu/staff-profiles/graduate-students/judit-cserny/ These studies are a joint collaboration with the UF Department of Biomedical Engineering. Please follow the link below to learn about our collaborator Dr. Benjamin Keselowsky http://www.bme.ufl.edu/people/keselowsky_benjamin
Lab Project Update
Submitted by Dr. Todd Brusko on Mon, 8/31/2015 – 07:00
In six months, my project has made remarkable progress. My lab isolated and expanded a rare population of regulatory T cells (Tregs) to a level that we believe may yield therapeutic efficacy. Importantly, the nanoparticle delivery approach appears to be working to sustain the activity of Tregs. This supports the notion that these cells will be functional and help restore balance in the immune system when re-infused into patients with type 1 diabetes.
Our project is currently progressing to the final stages of testing whether these cells are more effective at preventing disease in animal models. We are highly optimistic given our current results and hope to report our findings in the near future.