Phytosecretion of enteropathogenic Escherichia coli pilin subunit A in transgenic tobacco and its suitability for early life vaccinology.

A plant expression cassette system was engineered to efficiently target proteins to the default secretory pathway, allowing the expression of DNA inserts in three frames as fusion proteins containing a synthetic tobacco calreticulin cleavable signal peptide sequence, with the advantage of producing the recombinant proteins by phytosecretion. As one approach to develop a vaccine to enteropathogenic Escherichia coli (EPEC) infection, the oral immunogenicity of phytosecreted BfpA, the structural subunit A of the bundle-forming pilus, expressed at high levels (7.7% of soluble protein) in transgenic tobacco tissues, was demonstrated in BALB/c mice by the induction and detection of fecal anti-BfpA antibodies.