Cationic microparticles: A potent delivery system for DNA vaccines

Abstract

An approach involving the preparation of biodegradable microparticles with a cationic surface was developed to improve the delivery of adsorbed DNA into antigen-presenting cells after i.m. injection. The microparticles released intact and functional DNA over 2 weeks in vitro. In addition, the microparticles induced higher levels of marker gene expression in vivo. After i.m. immunization, the microparticles induced significantly enhanced serum antibody responses in comparison to naked DNA. Moreover, the level of antibodies induced by the microparticles was significantly enhanced by the addition of a vaccine adjuvant, aluminum phosphate. In addition, in contrast to naked DNA, the cationic microparticles induced potent cytotoxic T lymphocyte responses at a low dose.

Figure 1

Agarose gel of DNA after release from the surface of PLG/CTAB microparticles at various time points, after incubation in vitro at 37°C. Lane 1 is a marker lane, lanes 2–5 are DNA released at days 1, 3, 7, and 14, respectively, and lane 6 is control unformulated p55 gag DNA.

Figure 2

Serum IgG titers in groups (n = 10) of BALB/c mice immunized with either PLG/CTAB p55 gag DNA microparticles at 1 and 10 μg, PLG-CTAB DNA microparticles combined with aluminum phosphate at 1 μg, or naked DNA alone at 1 and 10 μg. Antibody titers are geometric mean titers ± SE at each time point. The responses from formulated DNA at both doses was significantly higher (P < 0.05) at all time points.

Figure 3

Serum IgG titers in groups (n = 10) of BALB/c mice immunized with either PLG/CTAB-p55 gag DNA, blank PLG microparticles + DNA, or DNA alone at 1 μg dose. Antibody titers are geometric mean titers ± SE at 2 weeks post-second immunization (week 6) time point. The response from the PLG/CTAB-p55 DNA was significantly higher (P < 0.05) than other groups.

Figure 4

Serum IgG titers in groups (n = 10) of BALB/c mice immunized with either PLG/DOTAP, PLG/DDA, or PLG/CTAB p55 DNA microparticles or naked DNA alone at 1 μg dose. Antibody titers are geometric mean titers ± SE at 2 weeks post-second immunization (week 6) time point. The response from all three formulations was significantly higher (P < 0.05) than the naked DNA group.

Figure 5

Serum IgG titers in groups (n = 10) of BALB/c mice immunized with PLG/CTAB microparticles of three different mean sizes (300 nm, 1 μm, and 30 μm) with 1 μg of adsorbed p55 gag DNA. Antibody titers are geometric mean titers ± SE at 2 weeks post-second immunization (week 6) time point. The responses from PLG/CTAB (300 nm and 1 μm) were significantly higher (P < 0.05) than 30 μm and naked DNA group.