The present invention concerns an universal polypeptidic carrier for targeting directly or indirectly a molecule to Gb3 receptor expressing cells and having the following formula STxB-Z(n)-Cys, wherein: STxB is the Shiga Toxin B subunit or a functional equivalent thereof, Z is an amino-acid devoided of sulfydryl group, n being 0, 1 or a polypeptide, Cys is the amino-acid Cysteine, and the use thereof for MHC class I and MHC class II presentation of antigens.