Nanoparticles Show Potential for Treating MS
Turning Down an Autoimmune Attack continued...
When dead or dying cells pass through the spleen, big white blood cells called macrophages gobble them up. As part of this process the macrophages send signals to other parts of the immune system, letting them know that the dying cells aren't dangerous, just routine bits of trash that need to go.
Years ago, researcher Stephen D. Miller, PhD, an immunologist in the Feinberg School of Medicine at Northwestern University in Chicago, figured that it might be possible to hijack this garbage removal system and get the body to recognize -- and then ignore -- proteins it was mistaking for threats.
"What we've done is simply tap into a system that the immune system was smart enough to evolve millions of years ago to get rid of dead and dying cells," Miller says.
He's already tried the approach in humans using white blood cells that were first collected and then killed. He then attached proteins to the dying cells and infused them into the body. In an early safety trial, Miller says that approach appeared to be well tolerated.
"There [were no side effects], there was no re-triggering of disease, and we actually showed that immune responses in patients were decreased," Miller says.
But other immune responses, such as protection against certain infections, remained strong. That suggests that patients treated this way wouldn't see the kind of general immune suppression that happens with current treatments for autoimmune diseases.
The problem with using whole cells, however, is that it's time consuming and expensive.
So Miller wondered if it might be possible to try the same thing with synthetic nanoparticles. First they tried tiny plastic beads. But since those don't break down in the body, he asked his Northwestern colleague Lonnie Shea, PhD, who is a biomedical engineer, for help finding another material that might be safer.
They decided on poly(lactide-co-glycolide), or PLG. It's a material that's used to make sutures, grafts, and other things that are meant to slowly dissolve in the body. By first dissolving PLG and then spinning the watery solution very rapidly, they were able to make tiny particles that could carry myelin proteins.