Antigenic characterisation of monoclonal antibodies againstSarcocystis muris by Western blotting and immuno-electron microscopy

The antigenic specificities of 13 monoclonal antibodies (mAbs) raised againstSarcocystis muris cystozoites were examined by Western blotting and immuno-electron microscopy against homologousS. muris and heterologousS. gigantea, S. tenella, S. arieticanis, S. capracanis, S. miescheriana andToxoplasma gondii antigens. Four mAbs reacted in Western blots againstS. muris antigens: SM-4 and-17 recognized single antigenic bands (31000 and 34000 MW, respectively) and SM-2 and-3 reacted against multiple bands (ranging from 12500–30000 and 13000–50000 MW, respectively). Similar antigens were also recognized by polyclonal immune sera from chronically infected mice. None of the mAbs cross-reacted with heterologousSarcocystis spp. orT. gondii. Ultrastructural studies performed with colloidal-gold conjugates demonstrated that three mAbs reacted with specific antigenic elements inS. muris cystozoites: SM-3 and-4 labelled pellicular determinants and SM-19 labelled micronemes. None of the mAbs crossreacted with heterologousSarcocystis spp., whereas polyclonal immune sera from chronically infected sheep, goats and pigs cross-reacted with a variety of antigens in allSarcocystis spp. except the primary cyst-wall determinants.Abbreviations cz Cystozoite - fi tibril - gs ground substance - mi micronemes - pe pellicle - pw primary cyst wall - rh rhoptries