The present invention relates to a plant virus expression vector comprising a foreign peptide coding sequence, which is being in the correct orientation for transcription and having an amber stop read through sequence at the beginning of the foreign peptide coding sequence insertion site (End of the segment of foreign DNA), wherein said plant virus expression vector is cucumber green mottle mosaic virus. Further, the vector of the present invention for expression of immunogenic polypeptides, including HBSAG, is provided. The plant expression vector can be used to produce immunogenic polypeptides, including HBSAG, in edible plant tissues. The edible plant tissues can be used to elicit an immune response in humans and animals when the plant tissues are consumed.