People have been waiting a long time for a cure for Type 1 diabetes. Hannah Pizzato, PhD, is one of them.
Pizzato was diagnosed with Type 1 diabetes when she was 4 years old. She was too young to understand it is an autoimmune disease. She didn’t know her immune system was attacking cells in her pancreas that are responsible for producing insulin, a hormone that regulates blood sugar. But from an early age, she began to question why people become sick.
“My whole life I was told a cure is coming and that I won’t have to deal with this very long, but then a cure never came,” said Pizzato, a principal scientist at the University of Arizona Health Sciences Center for Advanced Molecular and Immunological Therapies. “I was always interested in the fundamentals of how the body works and adapts over time to keep us alive,” she said. “I was intrigued by how biology influences human development.”
It isn’t a surprise her educational and research trajectory focused on the immune system and Type 1 diabetes. As one of the first scientists working at CAMI, Pizzato is building upon research done under the mentorship of Deepta Bhattacharya, PhD, the inaugural executive director of CAMI, with the goal of one day using a stem cell therapy to finally cure Type 1 diabetes.
Since the first successful bone marrow transplant in 1956, scientists all over the world have been examining stem cells and their potential to fight diseases, regenerate damaged tissues and develop personalized treatments for patients. Today, hematopoietic stem cells found in bone marrow are used to treat blood cancers such as leukemia, lymphoma, multiple myeloma and more.
One of the fastest-growing areas of stem cell research utilizes pluripotent stem cells, which are cells that can turn into any cell type in the body. Pizzato’s goal is to turn them into insulin-producing beta cells to replace the ones lost to Type 1 diabetes.
The biggest challenge comes from the immune system, which fights off infections, diseases and, unfortunately, regenerative treatments including stem cells. Bhattacharya and Pizzato have spent years trying to find a solution to this problem. Now, they may be on the verge of a breakthrough.
Pizzato was the first author on a paper published in Stem Cell Reports that detailed how the research team genetically engineered stem cells to evade detection by the immune system.
T cells, a type of white blood cell, are key drivers of immune rejection. They constantly scan for anything that doesn’t belong in the body, such as viruses and bacteria, and perform security checks by looking for human leukocyte antigen, a protein found on the surface of most cells. If the protein isn’t a match to the body’s specific human leukocyte antigen, the T cell is triggered to kill that cell.
“To get around this problem, we used a genetic engineering tool to cut out the gene that encodes for that protein,” Pizzato said. “This acts as a camouflage to get our modified stem cells around any investigating T cells.”
The lack of human leukocyte antigen solved the T cell problem, but it didn’t address two other parts of the immune system: natural killer cells and complement deposition. Natural killer cells, like T cells, are always on the lookout to destroy damaged or diseased cells. The immune system also relies on a process called complement deposition, where certain proteins bind to the surface of invaders to help the immune system recognize threats.
Pizzato said that after removing human leukocyte antigen, the team added several other proteins, some of which sent inhibitory signals to hinder the natural killer cells and others preventing complement deposition.
“It’s like we took the stem cell’s glasses off, and then added a hat, fake moustache and coat to prevent recognition,” Pizzato said.
The modified stem cells were tested in mice with fully functioning immune systems, where they successfully dodged rejection by the immune system and persisted.
“These findings are very encouraging and give us confidence we are ready to move forward,” Pizzato said.
Advancing CAR T cell therapy with biomimetic design
Humans have a long history of borrowing from nature to advance technology. It is a concept that researchers Mark Lee and Michael Kuhns, PhD, at the University of Arizona Health Sciences, employ to study the natural mechanisms behind how immune cells function to generate immunological therapies.
“Our understanding of biology and the internal mechanisms that sustain life is ever increasing,” Lee said. “The idea that we can mimic some of what we know about nature to create new technologies and treatments is amazing to me.”
For more than a decade, Lee worked alongside Kuhns, a professor in the U of A College of Medicine – Tucson’s Department of Immunobiology, to improve CAR T cell therapy, an immunotherapy used to treat certain types of cancer.
CAR T cells are manufactured by collecting a patient’s T cells and engineering them to produce chimeric antigen receptors, or CARs, that are designed to bind to certain proteins on cancer cells. The CAR T cells are transfused back into the patient, where they can go to work killing cancer cells.
“CAR T cell therapy has been a breakthrough, but it can sometimes be ineffective and also runs the risk of a severe inflammatory response,” said Kuhns, who is CAMI’s senior scientific advisor. “Since the fundamental design of CARs is based on an early-1990s understanding of T cell biology, we think there is room for improvement. We’ve learned a lot more about these molecular machines since then.”
Today, scientists have a much more detailed understanding of what drives T cell activation. In nature, each T cell contains a receptor complex made up of five components: the antigen receptor module, three signaling modules, and a coreceptor module. These components convert information into instructions for the T cell to follow.
“Now that we’ve zeroed in on the building blocks that make up each module and the intricacies of how information is relayed through receptors and into the cell, there are even more opportunities to explore,” Lee said.
Several CAR T cell therapies are approved by the Food and Drug Administration to treat blood cancers, including lymphomas, some forms of leukemia and multiple myeloma. Using nature as a blueprint, Kuhns engineered a biomimetic receptor called a five-module chimeric antigen receptor, or 5MCAR, that can be added to T cells.
Kuhns and Lee are testing their engineered 5MCAR T cells against Type 1 diabetes. In 2020, they co-authored a paper that described the 5MCAR T cell and its effectiveness against Type 1 diabetes in a nonobese diabetic mouse model.
“Type 1 diabetes develops when overreactive immune cells infiltrate areas of the pancreas and kill beta cells. Beta cells are responsible for producing the blood sugar-regulating hormone insulin,” Kuhns said. “Our paper showed evidence that we can direct different immune cells to kill the overreactive immune cells. This stops the process before it really gets going.”
They are encouraged by their findings. Lee’s initial experiments at CAMI will test how updated versions of 5MCAR T cells might be able eliminate Type 1 diabetes after it has already developed.
Lee and Kuhns are also collaborating on future generations of 5MCAR T cells they hope to advance to clinical trials. The ultimate goal, Lee says, is to develop a product to prevent and treat Type 1 diabetes in humans.
“Engineering is an iterative process: you build, test, refine and repeat,” Kuhns said. “That’s why modern cars don’t look anything like the Model A Fords built in 1903. We’ll be doing the refining in my lab and then taking that work to CAMI, almost like a showroom floor.”
In addition to 5MCAR T cells, Kuhns and Lee are investigating CD4, a coreceptor that they found plays a more active role in regulating T cell receptor signaling than previously thought.
In a study published in eLife in July 2022, they examined the relationship between CD4 and T cell function through years of evolution in fish, reptiles, marsupials and mammals. They discovered sequences of amino acids, called motifs, on different parts of CD4 that seemed to strengthen or weaken its signaling power.
“The CD4 molecule has been evolving these motifs for millions of years, so we knew they must be important,” said Lee, who published a second paper about CD4 motifs in eLife in April. “This knowledge is likely to fuel future innovations.”
