A New Approach to Treating Cat Allergies

Researchers at the Luxembourg Institute of Health have developed a new therapeutic approach to treat severe cat allergies. Based on modulating the immune system through injections of the primary cat allergen, this immunotherapy increases tolerance to the allergenic protein and reduces the main associated clinical signs.   Between 2.5 and 3 percent of the population is believed to be potentially allergic to pets. Cat allergies, in particular, are on the rise. They are characterized by hypersensitivity and an excessive immune response to certain allergens secreted by cats. The protein Fel d 1, found in their saliva, on their skin, and in their fur, is the primary allergen responsible. Rhinitis, conjunctivitis, and skin rashes are among the clinical manifestations of cat allergy; in the most severe cases, these can progress to asthma or even life-threatening respiratory distress. Only specific immunotherapy (allergy immunotherapy or AIT), also known as desensitization or allergen vaccination, can treat this condition. It generally involves the subcutaneous injection of increasing amounts of the problematic allergen until a dose is reached that induces long-term immune tolerance. It is the only effective and potentially long-lasting treatment for the allergy. However, at present, specific immunotherapy is far from foolproof in treating cat allergies. It still requires some improvements, particularly in terms of efficacy and safety. Researchers have proposed a new adjuvant, CpG, to optimize the response to this therapy and enhance its anti-inflammatory activity. The idea is to optimize the immune response to induce the production of antibodies against the Fel d 1 protein, while minimizing inflammation, and thereby increase tolerance to this allergen. When tested in mice, specific immunotherapy against Fel d 1, combined with a high dose of the CpG adjuvant, showed very promising results. Treated animals exhibited significantly reduced signs of inflammation and airway hyperreactivity. Physiologically, a decrease in pro-allergic molecules (cytokines) and antibodies (immunoglobulin E, IgE) commonly associated with allergic responses was observed, correlating with an increase in protective antibodies (IgA and IgG). The researchers also noted, very shortly after the injection, an increase in the number of immune cells involved in regulation and tolerance (plasmacytoid dendritic cells, natural killer cells, T cells, and regulatory B cells). These cells act as a brake on the immune system and thus prevent an allergic reaction. The study highlights the utility of a safe variant of the Fel d 1 allergen which, when combined with a dose of CpG that is well-tolerated in humans as part of specific immunotherapy, helps modulate the allergic response. Collectively, these results demonstrate the powerful anti-inflammatory and anti-allergic effect of this therapy, in conjunction with CpG. Based on these data, the researchers believe that CpG should be considered an effective adjuvant in the context of specific immunotherapy in humans. It could form the basis for new immunotherapeutic treatments for allergies.