The present invention is directed to a polymeric carrier cargo complex, comprising as a cargo at least one nucleic acid molecule and as a preferably non-toxic and non-immunogenic polymeric carrier disulfide-crosslinked cationic components for use as an immunostimulating agent or as an adjuvant, wherein the polymeric carrier cargo complex is administered in combination with at least one second nucleic acid molecule, which encodes a protein or peptide. The inventive polymeric carrier cargo complex administered in combination with the second nucleic acid molecule allows for both efficient transfection of nucleic acids into cells in vivo and in vitro and/or for induction of an innate and/or adaptive immune response, preferably dependent on the nucleic acid to be transported as a cargo and on the second nucleic acid molecule. The present invention also provides pharmaceutical compositions, particularly vaccines, comprising the inventive polymeric carrier cargo complex and the second nucleic acid molecule, as well as the use of the inventive polymeric carrier cargo complex and the second nucleic acid molecule for transfecting a cell, a tissue or an organism, as a medicament, for therapeutic purposes as disclosed herein, and/or as an immunostimulating agent or adjuvant, e.g. for eliciting an immune response for the treatment or prophylaxis of diseases as mentioned herein. Finally, the invention relates to kits containing the inventive polymeric carrier cargo complex and the second nucleic acid molecule, the inventive pharmaceutical composition and/or the inventive vaccine or any of its components in one or more parts of the kit.