Researchers Bill Robinson, P. J. Utz and Lawrence Steinman published results last year showing how microarrays - glass slides spotted with minute amounts of the proteins against which the body may be reacting - can provide a profile of the antibodies' targets. Their current work, which appears in the September issue of Nature Biotechnology, takes the technology a step further and shows that the pattern of antibody activation can be used to predict and treat animals suffering from a disease resembling M.S.
"Ultimately, we think the array can be used to guide patient-specific therapy," said Robinson, MD, PhD, assistant professor of medicine (immunology and rheumatology) and lead author of the study. For example, a blood sample from a patient thought to have M.S. could be profiled using the array to help identify whether the person is likely to progress to full-blown disease and whether the individual would benefit from therapy. The information obtained in the profile could then be used to personalize therapies.
The team, which included former Stanford researcher Hideki Garren, MD, PhD, showed that this strategy works in a mouse model of M.S. called experimental autoimmune encephalomyletis, or EAE. In both conditions, the immune system launches an attack against the myelin sheath, the fatty cells that insulate neurons from electricity and ensure the speedy transmission of nerve impulses. Neurons that have patches of myelin destroyed by M.S. or EAE short-circuit and can lead to a variety of neurological disorders, depending on the part of the brain affected.
"Looking at one M.S. marker at a time had previously not been terribly informative," said Robinson. "We thought that looking at thousands at once would be more fruitful." Thanks to a dozen or so labs around the world that shared their protein samples, the group rapidly produced a comprehensive array that covered hundreds of the myelin sheath proteins.
When they analyzed serum samples from EAE mice using the array, they found that each mouse had a unique pattern of reactivity. Based on their antibody profiles, mice whose immune systems were attacking more elements on the myelin sheath progressed to a more severe disease, while mice whose immune systems made more restricted responses did not progress and had fewer flare-ups. The group then designed a treatment to reverse the progression of the disease, treating mice that had already suffered an initial attack of paralysis.
Autoimmune responses are thought to develop when antibodies attack many different proteins in the organ being targeted, so Robinson and his colleagues wanted to find a therapy that specifically knocked out as many of the harmful responses as possible while leaving the rest of the immune system functional. To do so, they took advantage of a well-known but poorly understood process known as tolerization. In this process, the immune system is coaxed to tolerate an offending protein after injection of that same protein or pieces of it. Utz, MD, assistant professor of medicine (immunology and rheumatology), likens the process to allergy shots: the agent causing the allergic reaction is injected into muscle in order for the body to learn to ignore it.
Using the microarray information to guide them to the targets of the autoimmune response in the sickest mice, Garren and Steinman, MD, professor of neurology and neurological sciences, built on previous studies in Steinman's lab to create a tolerizing vaccine that delivered four of the targeted proteins. To make an effective delivery vehicle, they put the DNA sequence that encoded the proteins into a circular piece of DNA called a plasmid, creating a DNA vaccine. When these engineered plasmids were injected, they produced the desired proteins and a programmed tolerization process began.
One advantage of DNA vaccines over other methods of tolerization, Garren noted, is that it allows for multiple autoimmune targets to be tolerized simultaneously rather than one at a time. "We found that this approach broadly turns off autoimmune responses," said Robinson. "Clinically, the animals do better when receiving the vaccine. When we use our arrays to monitor the response, we see broad reductions in the progression of the disease."
The ability to profile which antibodies have gone awry has a number of implications for diagnosis and treatment of people with autoimmune diseases. "When we see these patients, we have no idea what is going to happen 10 years from now," Utz said. "It would be great to have a test that would let us know if a person is going to have a horrible outcome so we could treat aggressively, or if a person is going to be fine, or if a person is going to have a bad response to a therapy so we could avoid that."
Led by Steinman, the team plans to use their findings to help people with autoimmune diseases. To reach this goal, they co-founded Bayhill Therapeutics; Garren directs the scientific efforts of the company.
Using DNA vaccines to specifically turn off the immune system is a completely new way to immunize, said Steinman. "This is the opposite of what we try to do with traditional vaccines against bacteria and viruses, where we want to stimulate the immune system to attack the microbe," he added.
This study was funded by a number of sources, including funds from a $14.7 million contract from the National Institutes of Health, the Baxter Foundation and the Arthritis Foundation.
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