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.

hNUDC promotes the cell proliferation and differentiation in a leukemic cell line via activation of the thrombopoietin receptor (Mpl).

We have recently identified a human homolog of a fungal nuclear migration protein (hNUDC) that binds specifically with the extracellular domain of thrombopoietin receptor (Mpl). Preliminary studies with human CD34(+) cells cultured in serum-free medium and normal mice showed that hNUDC appears to act as a cytokine, triggering many of the same responses as thrombopoietin (TPO). More intriguingly, recent data gained using a NIH 3T3 system have demonstrated that hNUDC exerts its biological activities through activation of Mpl. In this study, we further compared the biological functions of hNUDC with TPO in an EPO-dependent UT-7 cell line that was engineered to express the thrombopoietin receptor (Mpl). These Mpl-expressing cells following stimulation by either hNUDC or TPO exhibited overlapping patterns of megakaryocytic proliferation and differentiation, manifested by cell morphological change, polyploidy and expression of CD41(+). Similar with TPO, hNUDC induced a sustained activation of the extracellular signal-regulated protein kinases-1 and -2 (ERK1/2) as well as p38 mitogen-activated kinase (p38 MAPK) pathways and these activations were inhibited in the presence of PD98059 or SB203580. Further evidence is provided that PD98059 or SB203580 inhibited hNUDC- or TPO-induced cell proliferation and differentiation, suggesting that ERK1/2 and p38 MAPK pathways are necessary in megakaryocyte development.