Species-restricted antibody response against a DNA-construct coding for aspartic proteinase from Schistosoma japonicum

Abstract.

DNA-based vaccine technology was used to immunize against the schistosome digestive enzyme, cathepsin D aspartic proteinase. The cDNA coding for Schistosoma japonicum aspartic proteinase was cloned in a mammalian expression vector under control of the CMV promoter/enhancer and expressed for the first time in transfected mammalian cells as well as in mice immunized – by means of intra-ear pinna injection – with the aspartic proteinase-encoding DNA construct. Mice developed antibodies which recognized the native protein in homogenates of S. japonicum worms and reacted with the gut and, to a much lesser degree, with the parenchyma of the parasites in cryostat sections. It was noteworthy that the vaccinated mouse sera did not detectably cross-react with S. mansoni antigens either in homogenates or on cryostat sections. By contrast, infection sera of mice or humans strongly cross-reacted with both schistosome species. We conclude that DNA vaccination can induce species-restricted antibody responses against schistosome proteins. The implications of this previously unrecognized specificity are discussed.