Immunohistochemical study of S100-like protein in Eimeria brunetti and Eimeria acervulina

We have investigated the expression of a calcium-binding protein, the S100 protein, in Eimeria brunetti and Eimeria acervulina stages. For this purpos e, paraffin sections of distal ileum and bursa of Fabricius or duodenum fro m experimentally infected chickens were treated with anti-alpha-S100 (anti- alpha subunit of S100 protein) and anti-beta-S100 (anti-beta subunit of S10 0 protein) monoclonal antibodies and anti-S100 whole molecule polyclonal an tibody. The avidin-biotin peroxidase method was used to demonstrate immunor eactivity. In the ileum, our results reveal a positive immunoreaction for t he beta subunit and S100 whole molecule within the macrogametes of E. brune tti, whereas they were devoid of immunostaining after treatment of the para ffin sections with the anti-alpha-S100 antiserum. Schizonts and oocysts of E. brunetti and all the E. acervulina stages gave a negative reaction after treatment with any of the three antiserum used in the study. This result i ndicated that the S100 protein molecules within these stages were not recog nized by the antibodies, suggesting that these molecules are different from those identified in macrogametes of E. brunetti. By contrast, in the epith elial cells, lining the lumen of the bursa of Fabricius, macrogametes of E. brunetti were stained by the three antibodies used. These results may indi cate the existence of metabolic adaptations that enable the parasite to inv ade tissue sites different from those where the parasite usually develops. (C)2000 Elsevier Science B.V. All rights reserved.