IMMUNOLOCALIZATION OF EXCRETORY/SECRETORY ANTIGENS EXPRESSED ON DIFFERENT LIFE CYCLE STAGES AND IN DIFFERENT ORGANS OF FASCIOLA GIGANTICA INFECTED CATTLE

Abstract

In this study, polyclonal antibodies (pAb) were prepared against Fasciola gigantica excretory/secretory (E/S) products and purified to demonstrate the highly reactive epitopes on the differentlife cycle stages of F. gigantica and on blood cells and different organs of naturally infectedcattle, as well as to screen internal organs for localization of E/S antigens to find out a suitablemethod for diagnosing the disease as early as possible. Using anti-F. gigantica E/S IgG pAb,immunostaining of different life cycle stages of F. gigantica detected strong positive reactions inall stages except eggs. The reactions were along tegumental surface, gut region of cercariae,miracidiae, metacercariae and tail of cercariae. Besides, the tegument, spine surface, muscularisand gut region of the adults were also positive. Immunoperoxidase localization of E/S productsby anti-F. gigantica E/S IgG pAb showed that E/S antigens were located in many organs ofnaturally infected cattle. Examination of peripheral blood mononuclear cells (PBMNCs)represented a high positivity in the phagosomes and activated monocytes as well as in cytoplasmof lymphocytes. Compared to sections of normal uninfected hosts, liver sections of infectedbovine hosts showed collapsed hepatocytes, thickened portal tract and a highly positive reactionin the cytoplasm of the liver cells. Target epitopes were located inside the splenic cells, mainlylymphocytes. In the gall bladder, positive peroxidase reactions were found in the mucosa andmuscularis layers, and in the epithelial cells lining mucosal glands. A marked positivity was inother organs of the naturally infected animals, as in the epithelial layer lining the glomeruli andtubules of the kidney, in heart cardiac muscle fibres and in cells lining the alveoli of the lungs.