Diagnosis of alveolar echinococcosis using immunoblotting with plural low molecular weight antigens

Alveolar echinococcosis (AE) is endemic to Hokkaido, Japan. For the past 20 years, detection of AE among inhabitants has involved serological screening using an enzyme-linked immunosorbent assay (ELISA) followed by Western blotting (WB). Between the years 1987 and 2000, antigens targeted on 66, 55 and 30-35 kDa bands were routinely used in the WB step of AE diagnosis. However, since 2001 diagnosis has been dependent on three smaller molecular weight antigens (26-28, 18 and 7-8 kDa). Due to its higher sensitivity, this improved WB approach has been used as a confirmation step in the screening process and also for the testing of suspected AE cases in hospital outpatients. Using the improved WB technique, a total of 1745 serum samples were examined in 2001-2006 with 81 patients detected and registered with AE. Interestingly, sera from 76 of the 81 diagnosed AE patients (93.8%) demonstrated reactivity with all three antigens. However, sera from the remaining five patients (6.2%) demonstrated no reactivity with the 18 kDa antigen, even though they exhibited clearly detectable levels of reactivity with the 26-28 and 7-8 kDa bands. These results suggest that medical practitioners need to pay particular attention to the specific reactions to some different diagnostic antigens to minimize the risk of misdiagnosing AE patients. In turn, these results may also provide important diagnostic information for cystic echinococcosis (CE).