Blood-Based Genetic Test Could Help Select Best Treatment for Autoimmune Disease

Ankylosing spondylitis (AS) is an autoimmune condition that is estimated to affect 1 in 200 people. It primarily causes inflammation in the spine, joints, and ligaments, leading to pain and stiffness. In extreme cases, some of the spinal bones may fuse together, causing a loss of spinal flexibility and a permanent hunched posture. The onset of symptoms is generally between the ages of 17 and 45. Individuals with AS often have other autoimmune issues, such as inflammation of the eyes, inflammatory bowel disease, and psoriasis. The initial treatment usually involves over-the-counter pain relievers like naproxen or ibuprofen, followed potentially by corticosteroid injections and even joint replacement surgery in certain cases.

Another option for treating the inflammation is through biologics, lab-engineered protein-based treatments. Two types of biologics are available for treating AS, including one class known as IL-17 inhibitors, which target the interleukin-17 (IL-17) protein. However, determining which biologic will be effective for a given patient is currently a matter of trial and error, with biologics showing effectiveness only around 40% of the time. Using an ineffective biologic can be expensive, cause unwanted side effects, and allow the condition to deteriorate further. Now, the latest research sheds new light on the molecular processes involved in AS that could allow healthcare providers to do away with this guesswork while treating the condition

A team of researchers from the OHSU School of Medicine (Portland, OR, USA) have discovered that a specific form of AS treatment works well in patients with a particular genetic mutation. AS does not have a single cause, with multiple genes associated with the condition. Specifically, about 72% of AS patients have a mutation in their CARD9 gene, responsible for producing proteins that contribute to the body's immune response. This mutation tends to make the CARD9 gene hyperactive, causing immune cells like neutrophils to become overactive, which may result in attacking healthy cells. In their study, the researchers first removed the CARD9 gene in mice used for autoimmune disease research and found that these genetically altered mice did not develop AS, establishing that the CARD9 gene plays a role in the disease.

The researchers discovered that individuals with the mutated CARD9 genes had significantly higher levels of the IL-17 protein in their blood than those without the mutation. This led them to theorize that AS patients with this particular CARD9 mutation could be more responsive to IL-17 inhibitor biologics. The findings, published in the journal Annals of the Rheumatic Diseases, could pave the way for more precise and effective treatments for AS. Currently, the team is collaborating with clinicians to further investigate this connection in people with AS. If subsequent studies confirm these initial findings, healthcare providers might eventually use genetic tests to identify patients with the CARD9 gene mutation.

“This is the first time research has shown that we might be able to use genetic markers to determine which therapy ankylosing spondylitis patients should receive,” said the study’s senior researcher, Ruth Napier, Ph.D. “These promising findings are encouraging. This is the first time I can say that I’m on the cusp of making a difference for patients with ankylosing spondylitis who seek relief.”

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