The present invention relates to a method for producing a DNA vaccine for cancer immunotherapy comprising at least the steps of (a) transforming an attenuated strain of Salmonella with at least one DNA molecule comprising at least one expression cassette encoding at least one antigen or at least one fragment thereof； (b) characterizing at least one transformed cell clone obtained in step (a)； and (c) selecting at least one of the transformed cell clone(s) characterized in step (b) and further characterizing said at least one selected transformed cell clone. The present invention further relates to a DNA vaccine obtainable by the method according to the present invention.
