Surfactant proteins A and D protect mice against pulmonary hypersensitivity induced by Aspergillus fumigatus antigens and allergens.

Allergic bronchopulmonary aspergillosis (ABPA) is an allergic disorder caused by an opportunistic fungal pathogen, Aspergillus fumigatus (AFU:). Lung surfactant proteins SP-A and SP-D can interact with the glycosylated antigens and allergens of AFU:, inhibit specific IgE binding to these allergens, and block histamine release from sensitized basophils. We have now examined the therapeutic effect of exogenous administration of human SP-A, SP-D, and a recombinant fragment of SP-D (rSP-D), in a murine model of pulmonary hypersensitivity induced by AFU: antigens and allergens, which resembles human ABPA immunologically. The ABPA mice exhibited high levels of AFU:-specific IgG and IgE, blood eosinophilia, extensive infiltration of lymphocytes and eosinophils in the lung sections, and a Th2 cytokine response. Treatment with SP-A, SP-D, and rSP-D lowered blood eosinophilia, pulmonary infiltration, and specific Ab levels considerably, which persisted up to 4 days in the SP-A-treated ABPA mice, and up to 16 days in the SP-D- or rSP-D-treated ABPA mice. The levels of IL-2, IL-4, and IL-5 were decreased, while the level of IFN-gamma was raised in the splenic supernatants of the treated mice, indicating a marked shift from Th2 to Th1 response. These results clearly implicate pulmonary SP-A and SP-D in the modulation of allergic reactions.