Comparison of in vitro translation products of Sarcocystis gigantea and Sarcocystis tenella

Abstract

RNA was purified from cystozoites of Sarcocystis gigantea and Sarcocystis tenella and used to in vitro translate polypeptides in a wheat germ and a rabbit reticulocyte translation system. The in vitro translated polypeptides were compared by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The S. tenella mRNA translated at least two polypeptides (mol. wt about 80,000 and 21,500) in both translation systems that were not translated by the S. gigantea mRNA. To study co-translational and initial post-translational processing in Sarcocystis, the poly(A) + RNA preparations were in vitro translated in the rabbit reticulocyte translation system in the presence or absence of canine microsomal membranes. Based on electrophoresis, there appeared to be modification of at least some Sarcocystis polypeptides in the mol. wt range 17,000–30,000. In addition, the translation products were immunoprecipitated with a homologous and a heterologous antiserum. The immunoprecipitated polypeptides were compared by electrophoresis and the S. tenella translation products contained at least one unique antigenic polypeptide with a mol. wt of about 34,700 that was not processed by the microsomal membranes. These results suggest that there is at least one polypeptide that is a candidate for use as an antigen for the differentiation of S. gigantea and S. tenella infections in sheep.