Abstract: The present invention relates to a protein composition suitable for inducing an immune response in a vertebrate comprising 2 to 10 protein variants of a single antigen, which is the APICAL MEMBRANE ANTIGEN 1 (PfAMA1 OR AMA1) of a Plasmodium species. The antigen comprises a plurality of variable amino acid positions, wherein the amino acid sequences of said protein variants, in combination, represent both the frequency of occurrence of each amino acid at said variable amino acid positions and the linkage between the variable amino acid positions, and wherein said frequency of occurrence is at least between 10% to 20% such as 10%, 11%, 12%, 13%, . . . , 20% in the single antigen, and wherein at least 75% of the linkages between the variable amino acid position is presented by the combination of protein variants.

Abstract: 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 cell's 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.

Abstract: The present invention relates to a protein composition suitable for inducing an immune response in a vertebrate comprising 2 to 10 protein variants of a single antigen, which is the APICAL MEMBRANE ANTIGEN 1 (PfAMA1 OR AMA1) of a Plasmodium species. The antigen comprises a plurality of variable amino acid positions, wherein the amino acid sequences of said protein variants, in combination, represent both the frequency of occurrence of each amino acid at said variable amino acid positions and the linkage between the variable amino acid positions, and wherein said frequency of occurrence is at least between 10% to 20% such as 10%, 11%, 12%, 13%, . . . , 20% in the single antigen, and wherein at least 75% of the linkages between the variable amino acid position is presented by the combination of protein variants.

Abstract: 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 said 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's 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.