In autoimmune diseases, the human body’s own defense system turns against itself, attacking healthy cells and their protein components.
Junior Christine Ausherman spent her summer at the Van Andel Research Institute as part of their Frederik and Lena Meijer Summer Internship Program, where she worked on a new method to pinpoint which proteins are being attacked.
Ausherman’s work focused on lupus, a disease in which the immune system’s antibodies — part of a defense mechanism that normally fights bacteria and viruses — fail to distinguish between foreign invaders and healthy tissue and attack the body’s own proteins.
This autoimmune response can cause a variety of symptoms ranging from fatigue and joint pain to kidney inflammation. As many as five million people worldwide have a form of lupus, and approximately 16,000 new cases are reported each year, according to the Lupus Foundation of America.
For her summer research, Ausherman worked with a specific tool called a peptide microarray, which allows researchers to test an antibody’s interaction with a variety of different proteins at once.
“Peptide microarrays are specialized glass microscope slides that display modified forms of proteins on the slide surface at very high density,” said Scott Rothbart, assistant professor in the Van Andel Research Institute’s Center for Epigenetics and lead investigator in the lab where Ausherman worked. “This allows us to monitor upward of 10,000 individual interactions simultaneously and comparatively on a single slide.”
To test for protein-antibody interaction, the glass slide is flooded with an antibody. If the antibody attacks a particular type of protein, it will bind to the protein on the slide, while proteins unaffected by the antibody will remain untouched. Attached to the antibodies are fluorescent molecules that allow the researchers to see which proteins attracted the antibodies.
“Then, we can look at the plate and see where the antibody binds,” Ausherman said. “The antibody is fluorescently labelled, so if the antibody binds, that area will light up under a fluorescent scanner.”
Ausherman’s microarrays focused on histones, a type of protein that helps package and store the cell’s DNA and can be attacked by antibodies in lupus patients.
“It’s been known for a while that antibodies against histone proteins are markers of autoimmune diseases like lupus and rheumatoid arthritis,” Rothbart said.
Using the histone peptide microarrays, Ausherman tested antibodies from lupus patients’ blood and commercial antibodies for their response to different histones.
While she focused on the four most common types of histones, these histones can be modified in many ways with different chemical tags, and the tags will affect their interactions with antibodies, Ausherman said.
By using antibodies from lupus patients, Ausherman was able to see if there was a common antibody response among the patients to particular modified forms of histone proteins.
“The goal of the project was to determine the utility of this new tool for the capture of antibodies from patients with lupus,” Rothbart said. “The histone peptide microarray is a platform we’ve helped develop over the last few years, and the capture of these antibodies is a new use for this tool.”
While Rothbart said more work is needed to establish this microarray technique as a way to screen patient samples, he is optimistic that further work will allow the technique to be used as a clinical diagnostic and staging tool or as a way to identify new biomarkers for autoimmune diseases such as lupus and rheumatoid arthritis. He said the technique may ultimately be applicable to cancer, too.
“Where we’d ultimately like to go is to explore the use of this technology in cancer,” Rothbart said. “We’re a cancer epigenetics lab, and so I think an unexplored space in this area is the prevalence of histone antibodies in patients with tumors. With proof-of-concept that this platform works with autoimmune cases, we’re excited for the prospect of applying this technology to other diseases as well.”