A method of efficiently expressing Plasmodium AMA-1 ectodomain or a functional part, derivative, and/or analogue thereof, in a eukaryotic expression system. Preferably, the Plasmodium AMA-1 ectodomain is Pf AMA-1 ectodomain. This protein may be expressed in yeast, such as Pichia pastoris. Efficient expression is possible using a method for producing mRNA encoding the Plasmodium AMA-1 ectodomain in a yeast cell, comprising providing the yeast cell with a nucleic acid encoding Plasmodium AMA-1 ectodomain, the nucleic acid being modified to utilize the yeast cells codon usage. Preferably, at least one putative yeast polyadenylation consensus sequence in the nucleic acid has been modified. More preferably, also at least one site in the protein that is generally glycosylated by eukaryotic expression systems, has been removed.
