Pertussis adjuvant prolongs intestinal hypersensitivity

Background: Immediate hypersensitivity reactions are a hallmark of allergic disease, and result in the clinical features of food allergy, hayfever, an d atopic asthma. The mechanism by which an individual becomes sensitized to an ingested or airborne allergen is not clear, however exposure to bacteri a or bacterial products that act as adjuvants may be a contributing factor. The purpose of this study was to examine the role of pertussis toxin (PT) in inducing intestinal hypersensitivity reactions, particularly the ability of the adjuvant to prolong the sensitization. Methods: Rats were sensitize d to ovalbumin (OA) by injection of OA alone or with 50 ng PT. Secretory re sponses to OA challenge and nerve stimulation were assessed in jejunal tiss ues mounted in Ussing chambers. Results: Jejunal segments from rats sensiti zed to OA alone responded to antigen challenge with ion secretion, but sens itization was transient in that specific IgE titers and responses to lumina l antigen disappeared by 14 days. In contrast, co-administration of 50 ng P T with OA resulted in long-lasting sensitization. Secretory responses to bo th luminal and serosal OA challenge were present 8 months after primary imm unization. Enhanced secretory responses to nerve stimulation, increased muc osal mast cell numbers, as well as elevated IgE titers were also induced an d may have contributed to the overall responsiveness of the intestine to an tigen challenge. Conclusions: Our findings indicate nanogram quantities of PT, when administered with a food protein, result in long-term sensitizatio n to the antigen, and altered intestinal neuroimmune function. These data s uggest that exposure to bacterial pathogens may prolong the normally transi ent immune responsiveness to inert food antigens.