Antigenic proteins associated with calcareous corpuscules of Taenia solium: Partial characterization of a calcium-binding protein

Background. A protein fraction was isolated from calcareous corpuscles of Taenia solium cysticerci. The antigens in this fraction were recognized in ELISA and Western blot assays by all sera from a group of patients with active neurocysticercosis (NC) and were not recognized by the sera from patients with other neurological disorders. Western blot analysis also showed that several high molecular weight proteins were strongly recognized by antibodies in all the neurocysticercotic patient sera, suggesting a potential for serological diagnosis of neurocysticercosis. Methods. In order to characterize these antigenic proteins, we used a monoclonal antibody raised against a high MW calcium-binding protein associated with calcareous corpuscles of Echinococcus granulosus (EgCaBP1). Results. Western blot assays revealed the recognition of a protein band of about 260 kDa, appearing within the range of the high MW antigens recognized by the NC sera. Several cDNA clones were isolated through screening of a T. solium metacestode library with a DNA probe for EgCaBP1, containing partial coding sequences showing about 88% identity with the protein of E. granulosus. Moreover, a recombinant product expressed in bacteria from the partial coding sequence of T. solium showed the ability to bind Ca²⁺ and was recognized by the monoclonal antibody. This recombinant calcium-binding protein of T. solium was not recognized by the NC patient sera by ELISA and Western blot. Conclusions. Antigenic proteins in the calcareous corpuscles of T. solium metacestodes deserve further analysis as candidates in the development of diagnostic tools for neurocysticercosis.