Described are DNA sequences encoding an E6 or E7 fusionprotein of HPV, wherein said DNA sequences are characterized by a combination of the following features: original codons are exchanged by codons which lead to an enhanced translation in a mammalian cell, they contain a deletion resulting in the production of a truncated non-functional protein, and they encode a fusionpartner which is a highly immunogenic polypeptide capable of enhancing the immunogenicity of the E6 or E7 protein in the mammalian host. Furthermore, the modified E6 or E7 protein encoded by said DNA sequences as well as expression vectors containing said DNA sequences are described as well as several uses of the these compounds.