The present invention relates to methods of inducing a T-cell response against a Plasmodium species antigen in a subject. These method comprise administering to a subject a composition comprising a bacterium which expresses one or more immunogenic polypeptides, the amino acid sequence of which comprise one or more amino acid sequences derived from wild-type Plasmodium LSA1, Ce1TOS, CSP, and/or TRAP sequences, wherein said amino acid sequences are derived by (i) codon optimization of the wild-type sequence for expression in said bacterium, (ii) deletion of at least one hydrophobic region present in the wild-type sequence, and/or (iii) in the case of LSA1 and CSP, minimization of repeat units present in the wild-type sequence.
