Bacterial magnetic particles as a novel and efficient gene vaccine delivery system.

DNA vaccination is an attractive approach for eliciting antigen-specific immunity. In this study, we used magnetosomes (bacterial magnetic particles, BMPs) as carriers of a recombinant DNA composed of a secondary lymphoid tissue chemokine, human papillomavirus type E7 (HPV-E7) and Ig-Fc fragment (pSLC-E7-Fc) to generate a gene vaccine (BMP-V) for tumour immunotherapy. The results indicate that BMPs linked to DNA more efficiently in phosphate-buffered saline (pH=4-5) than in physiological saline. Efficient transfection of BMP-V in vitro and in vivo was achieved when a 600-mT static magnetic field was applied for 10 min. In a mouse tumour model, subcutaneous injection of BMP-V (5 µg, × 3 at 4-day intervals) plus magnetic exposure elicited systemic HPV-E7-specific immunity leading to significant tumour inhibition. The treated mice tolerated BMP-V immunisation well with no toxic side effects, as shown by histopathological examinations of major internal organs. Taken together, these results suggest that BMP can be used as a gene carrier to elicit a systemic immune response.