Abstract: High expression levels and simple downstream processing are essential for the production of recombinant proteins at low cost. We report here a new expression vector which allows production of fusion proteins in Dictyostelium discoideum. We made use of the ability of Discoidin I to bind Sepharose-4B to set up a nearly single step purification procedure. The Discoidin I coding region was fused to several forms of the malaria parasite CSP gene in a Dictyostelium expression vector, allowing intracellular accumulation as well as partial secretion via a pathway unrelated to the endoplasmic reticulum and Golgi. The fusion proteins present in cell extracts were affinity-purified over Sepharose-4B columns. Addition of a signal peptide allowed endoplasmic reticulum targeting and glycosylation of the fusion protein. Inclusion of a thrombin cleavage site allowed to cleave Discoidin from the CSP protein. The use of stable and low cost Sepharose 4B as affinity matrix should allow large-scale preparations.

Abstract: A recombinant polypeptide comprising a polypeptide which has added thereto a glycoxyl-phosphatidylinositol anchor structure, said polypeptide demonstrating a greater immune response than the corresponding polypeptide without the anchor. The polypeptide may be a parasite antigen such as a Plasmodium falciparum polypeptide. Recombinant vectors comprising the DNA sequence encoding the polypeptide with a glycolipid anchor addition sequence and host cells based thereon are also disclosed as well as vaccines and methods of inducing an immune response based on the polypeptides.

Abstract: The invention relates to recombinant DNA molecules comprising a Dictyostelium discoideum homologous promoter region, a heterologous DNA sequence with a Dictyostelium discoideum homologous peptide sequence capable of functioning as a leader peptide sequence positioned upstream thereof and in proper reading frame therewith, and a Dictyostelium discoideum homologous termination region, the heterologous DNA sequence encoding the desired functional polypeptide or intermediate thereof, said DNA sequence being positioned downstream from the promoter region and said termination region being positioned downstream from the DNA sequence. The invention also provides recombinant dictyostelid hosts as well as methods for preparing recombinant DNA molecules of the invention and for expressing recombinant polypeptides encoded by said recombinant DNA molecules in dictyostelid hosts. The invention in particular relates to the expression of the CS protein of Plasmodium falciparum.