Development of atopy by severe paramyxoviral infection in a mouse model.

Background Atopic diseases have been increasing in prevalence, yet the initial inciting events that lead to atopy are not understood. Paramyxoviral infections have been suggested to play a role; however, much of these data are correlative. Objective To determine whether exposure to a nonviral antigen during a paramyxoviral infection is sufficient to drive IgE production against the bystander antigen and whether clinical disease against this antigen would result. Methods Wild-type C57BL6 mice or mice deficient in FceRIα (FceRIα −/− ) or IgE (IgE −/− ) were inoculated with Sendai virus (SeV) or UV-inactivated SeV (UV-SeV) and subsequently exposed to ovalbumin (OVA) intranasally. Mice were further challenged 3 times with intranasal OVA on days 20 to 22 after inoculation with SeV, and airway hyperreactivity and mucous cell metaplasia were determined. Results Exposure to OVA during SeV infection led to significant OVA specific IgE production (median, 548 vs 0 ng/mL; P = .03; SeV vs UV-SeV). This induction of OVA specific IgE production depended on FceRI because FceRIα −/− mice produced significantly less IgE (112 ng/mL; P = .03; vs wild-type mice). Furthermore, in wild-type mice OVA exposure and challenge significantly enhanced SeV-induced airway hyperreactivity and mucous cell metaplasia, but this failed to occur in either FceRIα −/− or IgE −/− mice. Conclusion A single exposure to a bystander allergen during a paramyxoviral infection is sufficient to drive allergen specific IgE production in a partial FceRI-dependent mechanism. These data begin to provide mechanistic insight into how viral infections might drive development of atopic disease.