Poly(propyleneimine) dendrimer and dendrosome mediated genetic immunization against hepatitis B

The purpose of the present research work is to explore the potential of dendrosomes in genetic immunization against hepatitis B. Plasmid DNA encoding pRc/CMV-HBs[S] (5.6 kb), encoding the small region of the hepatitis B surface antigen, was complexed with 5th generation poly(propyleneimine) dendrimer (PPI) in different ratios. Transfection of CHO cells revealed that a ratio of 1:50 for pDNA:PPI was optimum for transfection. Results of cytotoxicity studies showed that the toxicity of PPI-DNA complex was significantly (p<0.05) higher for PPI 75 and PPI 100 as compared to the other PPI-DNA complexes. PPI 50 was employed for preparation of dendrosomes by reverse phase evaporation method. The dendrosomal formulation DF3 was found to possess optimum vesicle size, zeta potential and entrapment efficiency. In vitro production of HBsAg in CHO cells showed that DF3 possess maximum transfection efficiency. In vivo immunization studies were carried out by giving a single intramuscular injection of 10 microg of plasmid DNA (pDNA) or its dendrimeric or dendrosomal formulation to female Balb/c mice, followed by estimation of total IgG, IgG(1), IgG(2a), IgG(2b), biweekly. DF3 was found to elicit maximum immune response in terms of total IgG and its subclasses under study as compared to PPI 50 and pDNA at all time points. Animals immunized with DF3 developed very high cytokine level. Higher level of IFN-gamma suggests that the immune response was strictly Th1 mediated. Our observations clearly prove the superiority of dendrosomes over PPI-DNA complex and pDNA for genetic immunization against hepatitis B.