Induction of Potent Immune Responses by Cationic Microparticles with Adsorbed Human Immunodeficiency Virus DNA Vaccines

Abstract

The effectiveness of cationic microparticles with adsorbed DNA at inducing immune responses was investigated in mice, guinea pigs, and rhesus macaques. Plasmid DNA vaccines encoding human immunodeficiency virus (HIV) Gag and Env adsorbed onto the surface of cationic poly(lactide-coglycolide) (PLG) microparticles were shown to be substantially more potent than corresponding naked DNA vaccines. In mice immunized with HIV gag DNA, adsorption onto PLG increased CD8 ؉ T-cell and antibody responses by ϳ100-and ϳ1,000-fold, respectively. In guinea pigs immunized with HIV env DNA adsorbed onto PLG, antibody responses showed a more rapid onset and achieved markedly higher enzyme-linked immunosorbent assay and neutralizing titers than in animals immunized with naked DNA. DNA vaccines have been shown to induce immune responses and protective immunity in many animal models of infectious disease (for a review, see reference 11). In mice, such responses can often be achieved with low doses (Ͻ1 g) of naked DNA. However, the immunogenicity of DNA vaccines in larger animals (e.g., guinea pigs, rabbits, and nonhuman primates) has been much lower than that observed in mice, even at higher doses of DNA. In human clinical trials, certain DNA vaccines have been shown to induce immune responses (5,19,30), but multiple immunizations of high doses of DNA were required. Therefore, in order to provide protective efficacy in humans, the potency of DNA vaccines needs to be increased. So far, it appears that DNA vaccines are more effective at priming T-cell responses than antibodies, as exemplified by induction of cytotoxic T lymphocytes (CTL) but no antibodies against malaria circumsporozoite protein in humans (30). Similarly, we show here that in mice, human immunodeficiency virus (HIV) gag DNA primed CD8 ϩ T-cell responses at doses of DNA 10-to 100-fold lower than that required for priming of antibody responses. Therefore, technologies aimed at increasing the potency of DNA vaccines need to be especially effective at boosting humoral responses.The technology described herein, formulation of DNA onto cationic poly(lactide-coglycolide) (PLG) microparticles, has been developed as a means to better target DNA to antigen-presenting cells (APCs). PLG microparticles are an attractive approach for vaccine delivery, since the polymer is biodegradable and biocompatible and has been used to develop several drug delivery systems (21). In addition, PLG microparticles have also been used for a number of years as delivery systems for entrapped vaccine antigens (24). More recently, PLG microparticles have been described as a delivery system for entrapped DNA vaccines (15,18). Nevertheless, recent observations have shown that DNA is damaged during microencapsulation, leading to a significant reduction in supercoiled DNA (2, 29). Moreover, the encapsulation efficiency is often low. Therefore, we developed a novel approach of adsorbing DNA onto the surface of PLG microparticles to avoid the problems associated with microencapsulation of DNA. This approach, ...

MIDGE/hNIS vaccination generates antigen‐associated CD8+IFN‐γ+ T cells and enhances protective antitumor immunity

“…[23][24][25] Many strategies have been used in an attempt to enhance the immunogenicity of DNA vaccines. [26][27][28][29][30][31] It is evident that the potencies of these vaccines depends on amount of the antigen expressed in transfected cells. 6 Therefore, a successful DNA vaccine strategy requires both the efficient delivery of DNA into somatic cells and the appropriate expression of the gene products in the targeted cells.…”

Induction in Humans of CD8+ and CD4+ T Cell and Antibody Responses by Sequential Immunization with Malaria DNA and Recombinant Protein

“…There is now an emerging body of data suggesting that combined vaccination regimens involving different vaccine vehicles or means of Ag presentation to the immune system induce immune responses more efficiently than vaccination with a single vehicle (11,38,39). Numerous data generated with prime-boost strategies in animal models have shown that priming with DNA and boosting with other delivery systems (e.g., recombinant poxviruses, recombinant protein, and recombinant adenovirus) can result in an increase in Ag-specific Ab and T cell responses and protective efficacy (40 -44).…”

Polylactide-co-glycolide (PLG) microparticles modify the immune response to DNA vaccination

“…In studies of DNA vaccination against human immunodeficiency virus (HIV) gag and env in rhesus macaques, PLG formulation increased CD8+ T cell responses up to 1000 fold while boosting total antibody responses. The magnitude of the response to DNA vaccination with PLG DNA microparticles was found to be equivalent to that induced by the highly immunogenic recombinant gp120 protein formulated with the strong adjuvant 16/11/2007 MF-59 [8]. However, the ability of PLG-DNA formulations to skew immune responses away from Th2 is less established and has not been tested in animal models of viral pulmonary infection.…”