IgE-dependent humoral immune response in Echinococcus multilocularis infection: circulating and basophil-bound specific IgE against Echinococcus antigens in patients with alveolar echinococcosis.

Clinical symptoms of immediate-type hypersensitivity (ITH) and specific IgE against Echinococcus granulosus antigens are frequently present in patients with hydatid cysts. In alveolar echinococcosis (AE) due to E. multilocularis, clinical manifestations related to ITH have never been reported. The IgE-dependent humoral immune response was evaluated in 30 patients with AE. Circulating specific IgE (sIgE) were determined with two different methods of radio-allergo-sorbent test. Serum sIgE were determined sequentially in 18 patients over 15 months. Specific IgE bound to circulating basophils were assessed with two tests in vitro, measuring specific degranulation and histamine release. The respective abilities of E. granulosus and E. multilocularis antigens to reveal bound and circulating IgE antibodies were also assayed. Despite the absence of clinical symptoms of ITH and the frequent lack of circulating sIgE, an immunological response involving IgE was always present in human AE: basophil-bound sIgE were revealed in every patient by histamine release and degranulation tests; these tests were constantly negative in control subjects. Echinococcus granulosus extracts were more effective for detecting circulating sIgE; however E. multilocularis antigenic preparation induced a histamine release significantly higher than E. granulosus extracts. These results suggest that IgE-dependent humoral immune response could play a role in the host-parasite relationship in AE. Moreover, the sensitivity of the tests used to detect basophil-bound sIgE was higher than that of the usual serological tests, and the basophil degranulation test could be used to confirm diagnosis of AE in endemic countries.