Exploring Biomarkers for Atopic Dermatitis

Atopic dermatitis in dogs, also known as atopy or seasonal allergies, is a common and frustrating problem affecting up to 25% of dogs in the United States. The disease is characterized by an exaggerated immune system response to allergens in the environment. Intense itching is the most common clinical sign, accompanied by secondary skin and ear infections, hair loss, and skin thickening and discoloration. While we know that atopy is influenced by multiple factors including the environment, a genetic predisposition, immune system activation, and the production of various inflammatory molecules. However, we don’t fully understand how this disease develops in dogs, so we don’t know which molecules or pathways are useful for disease monitoring or worthy of study as new treatment targets. To fill this knowledge gap, AKC Canine Health Foundation (CHF) funded investigators at the University of Florida conducted a pilot study to explore potential biomarkers for canine atopic dermatitis (CHF Grant 02653-A: Evaluation of the Serum and Cutaneous Levels of Chemokines in Atopic Dogs).

Measuring cell signaling proteins may be useful to monitor disease progression in dogs with atopic dermatitis.

A biomarker is a molecule measurable in blood, other bodily fluids, or tissues that indicates a specific condition or disease. Biomarkers are helpful to diagnose disease before clinical signs are severe and can also be used to monitor disease progression and response to treatment.

Based on previous veterinary and human medicine studies of atopy, this study focused on four specific molecules, called chemokines, that might be useful biomarkers for canine atopy. Chemokines are signaling proteins that help regulate the immune system. Chemokine levels were measured circulating freely in the bloodstream, enclosed in exosomes (small vesicles that transport proteins between cells), and within the skin of atopic and healthy dogs. The genetic signal (mRNA) for each of the four chemokines was also measured. Finally, investigators assessed if chemokine levels correlated with disease severity in affected dogs.

Analysis showed that levels of the genetic signal for three of the four chemokines studied was higher in the skin of atopic dogs compared to healthy dogs. However, the actual chemokine levels were not significantly different in the blood, skin, or exosomes. One chemokine level did correlate with disease severity and may be useful as a biomarker for response to treatment.

These results provide some important lessons: protein levels don’t always match genetic signal levels, exosomes provide a viable option for measuring these biomarkers, and the four chemokines studied do play a role in canine atopy. Additional study is needed to further explore and refine these findings, but the validation of new biomarkers for canine atopy looks promising. Learn more about CHF-funded research into dermatology and allergic disease at akcchf.org/dermatologyRPA.