Cationic polymers that enhance the performance of HbsAg DNA in vivo

In this paper, different cationic polymers were investigated as a DNA delivery system both in vitro in dendritic and muscle cells and in vivo, in a murine model. Expression of the reporter gene β-galactosidase was used in order to determine the in vitro transfection efficiency of these polymer-DNA complexes (polyplexes) and both specific mRNA and protein expression were monitored in parallel with polyplex toxicity on the cells. Interestingly, the enhancing expression activities of the different polyplexes were tissue-dependent, implying that they may gain entrance to the cells through specific receptors. Subsequently, complexes of polymers and DNA plasmid (pCMV-S) encoding the human hepatitis B virus (HBV) surface antigen (HBsAg) were injected into the skeletal muscles of BALB/c mice. Higher levels of both HBsAg local expression in the tibial anterior muscles and systemic humoral immune responses were detected when the selected polymers complexed with pCMV-S were compared to those complexed with pCMV-S alone. Induction of immunoglobulin G2a (IgG2a) against HbsAg in the serum of pCMV-S-polyplex vaccinated mice varied with the polymer used, suggesting that polyplex-mediated DNA vaccination can potentially modulate the type of helper T cell immunity (Th). The effect of some polyplexes to switch the host immune response more towards a Th1 response may be associated with their differential efficiency to transfect dendritic cells and/or other antigen-presenting cells (APC) as was observed in vitro. These results suggest that the investigated cationic polymers can be effective as delivery/adjuvant compounds for DNA.