Autoimmune diseases like lupus, rheumatoid arthritis, and type 1 diabetes are thought to affect as many as 50 million Americans. They can be chronic and, at times, even life-threatening, but because they are frequently "invisible" and understudied in comparison to conditions like, say, cancer, they are very often underdiagnosed.
While there are more than 100 different diseases that fall into this category, they all involve the same underlying mechanism. That of the body's own immune cells attacking healthy tissues, believing it is under threat. Researchers are starting to understand the genetic and environmental underpinnings of autoimmune disorders. However, current treatment plans tend to have one major problem – yes, they destroy the misfunctioning immune cells but they also inadvertently destroy healthy immune cells, leaving patients with a weakened immune system and vulnerable to infection.
Now, researchers from the University of Utah Health have come up with a new technique that targets the misfunctioning immune cells without affecting healthy cells. Although it has only been proven to work in mice, the results of a study published in Nature Biomedical Engineering look promising.
"We are really taking treatment for autoimmune disease in a new direction," Mingnan Chen, an assistant professor in Pharmaceutical Chemistry, said in a statement.
The technique rests on PD-1-expressing cells (including immune cells like the B and T lymphocytes) – which, in patients with autoimmune disease, ignore the checkpoint-like mechanism that prevents cells from attacking the body in healthy people.
The treatment Chen and colleagues devised involves an engineered protein molecule containing an anti-PD-1 antibody fragment, a toxin (Pseudomonas exotoxin), and a binder (albumin-binding domain), which drains misfunctioning PD-1-expressing cells from the body. The antibody fragment gains access to the PD-1-expressing cell (like a key opening a lock), while the toxin kills the cell. The binder, meanwhile, allows the specially engineered molecule to circulate for longer.
"This is the first time anyone has looked at the programmed cell death protein (PD-1) cells as a target to develop therapeutics for autoimmune disease," Chen added.
To put it to the test, researchers used a mouse model that looks like type 1 diabetes. With treatment, the team was able to delay disease onset in the mice by 29 weeks compared to 19 weeks in the control-treated group. Response to the treatment was even more impressive in mice genetically engineered to display symptoms of multiple sclerosis. It didn't just halt paralysis progression – it reversed it, enabling the mice to walk again. The team observed the mice for 25 days post-treatment and the paralysis did not return, suggesting one dose could be all it takes to stamp out autoimmunity.
Encouragingly, mice in both models showed signs of a normal immune response and no long-term damage. But, it is important to stress, it is mice and a successful mouse model does not necessarily translate to a sure-fire cure for humans.
Still, there are reasons to be hopeful, Chen says. "To make similar therapeutics for people, we would need to find the anti-human PD-1 antibody, like the anti-mouse PD-1 antibody," he explained. "If we can generate the human version of therapeutics, I think we could make a huge impact in treating autoimmune disease." We have our fingers crossed.