Targets for the diagnosis of Acanthamoeba eye infections include four cyst wall proteins and the mannose-binding domain of the trophozoite mannose-binding protein

Abstract

Free-living amoeba in the soil or water cause Acanthamoeba keratitis, which is diagnosed by identification of unlabeled cysts by in vivo confocal microscopy of the eye or calcofluor-white (CFW) labeled cysts by fluorescence microscopy of corneal scrapings. Alternatively, Acanthamoeba infections are diagnosed by the identification of trophozoites in eye cultures. Here, we showed that rabbit antibodies (rAbs) to four abundant cyst wall proteins (Jonah, Luke, Leo, and laccase) each efficiently identify CFW-labeled cysts of 10 of the 11 Acanthamoeba isolates tested. Further, laccase released into the medium by encysting Acanthamoebae was detected by an enzyme-linked immunoassay. We also showed that rAbs to the mannose-binding domain (ManBD) of the Acanthamoeba mannose-binding protein, which mediates adherence of trophozoites to keratinocytes, efficiently identify DAPI-labeled trophozoites of all 11 Acanthamoeba isolates tested. In summary, four wall proteins and the ManBD appear to be excellent targets for the diagnosis of Acanthamoeba cysts and trophozoites, respectively.