Intraperitoneal Administration of Calcium Phosphate Nanoparticles Encapsulating pSVβgal Elicits Immune Response to Encoded Protein

Calcium Phosphate (CAP) nanoparticles encapsulating a marker plasmid, pSVβgal, has been administered intraperitonially to six to eight-week old female Swiss albino mice having body weight of around 20–25 g. As a consequence of pDNA expression, high concentration of β-gal protein has been observed which depicts calcium phosphate nanoparticles to be an efficient non-viral vector for delivering pDNA to cells and its intracellular trafficking to the nucleus. A 10-fold increase in the antibody titers in the 6th week predominated by IgG2a over intraperitoneal injections of naked pSV gal alone. IgG2a antibody titers elevation was found to be continued in animals from 6th to 8th week duration also, and the kinetics of the anti β-gal response induced by gene transfection showed about 30-fold higher antibody titers at the end of the 8th week after last immunization. Highly restricted IgG2a antibody response to the encoded antigen together with Type I cytokines secretion from in vitro β-gal stimulated splenic CD4⁺ T cells from mice immunized with encapsulated plasmid demonstrated that immunization with CAP nanoparticles encapsulated plasmid DNA encoding protein is a powerful tool for initiating a Th1 response to that antigen. The rise in the circulating immune complex in serum of the experimental animals when compared to the control animals also supported this fact. By intraperitoneally administering pSVβgal loaded CAP nanoparticles into the mice did not show any adverse local or systemic reactions in response to calcium phosphate and even after repeated doses they were very well tolerated. The total amount of pDNA administered in the animal in the present experiment for significant level of immune response was as small as 1 μg only which is much lower than that administered through other carriers.