PLGA nanoparticle-mediated delivery of tumor antigenic peptides elicits effective immune responses

Abstract

Abstract:The peptide vaccine clinical trials encountered limited success because of difficulties associated with stability and delivery, resulting in inefficient antigen presentation and low response rates in patients with cancer. The purpose of this study was to develop a novel delivery approach for tumor antigenic peptides in order to elicit enhanced immune responses using poly(DL-lactide-co-glycolide) nanoparticles (PLGA-NPs) encapsulating tumor antigenic peptides. PLGA-NPs were made using the double emulsion-solvent evaporation method. Artificial antigen-presenting cells were generated by human dendritic cells (DCs) loaded with PLGA-NPs encapsulating tumor antigenic peptide(s). The efficiency of the antigen presentation was measured by interferon-γ ELISpot assay (Vector Laboratories, Burlingame, CA). Antigenspecific cytotoxic T lymphocytes (CTLs) were generated and evaluated by CytoTox 96 ® Non-Radioactive Cytotoxicity Assay (Promega, Fitchburg, WI). The efficiency of the peptide delivery was compared between the methods of emulsification in incomplete Freund's adjuvant and encapsulation in PLGA-NPs. Our results showed that most of the PLGA-NPs were from 150 nm to 500 nm in diameter, and were negatively charged at pH 7.4 with a mean zeta potential of −15.53 ± 0.71 mV; the PLGA-NPs could be colocalized in human DCs in 30 minutes of incubation. Human DCs loaded with PLGA-NPs encapsulating peptide induced significantly stronger CTL cytotoxicity than those pulsed with free peptide, while human DCs loaded with PLGA-NPs encapsulating a three-peptide cocktail induced a significantly greater CTL response than those encapsulating a two-peptide cocktail. Most importantly, the peptide dose encapsulated in PLGA-NPs was 63 times less than that emulsified in incomplete Freund's adjuvant, but it induced a more powerful CTL response in vivo. These results demonstrate that the delivery of peptides encapsulated in PLGA-NPs is a promising approach to induce effective antitumor CTL responses in vivo.

Enhancement of DC-mediated anti-leukemic immunity in vitro by WT1 antigen and CpG co-encapsulated in PLGA microparticles

“…1C). This result was in agreement with extensive prior studies, which showed that PLGA particles from 50 nm to 3 μm in size could be effi ciently taken up by DCs (KovacsovicsBankowski and Rock, 1995;Ma et al, 2012).…”

“…(Kovacsovics-Bankowski and Rock, 1995;Zhang et al, 2011;Ma et al, 2012). PLGA particles can protect the antigen from enzymatic degradation (Kovacsovics-Bankowski and Rock, 1995), increase the effi ciency of antigenloading (Hanlon et al, 2011;Ma et al, 2012), facilitate cross-presentation of the antigen (Ma et al, 2011), and co-deliver adjuvant into DCs (Zhang et al, 2007). In agreement with these immune-modulating mechanisms of PLGA carriers, we also observed that PLGA MPs could be effectively taken into the cytoplasm of DCs (Fig.…”

“…Prior research has shown that poly (lactide-co-glycolide) (PLGA) nano/ microparticles (NPs/MPs) can enhance the immunogenicity of antigens. In animal studies, tumor antigens carried by PLGA particles signifi cantly improved the anticancer immune response Ma et al, 2012). So far, however, there is no report on utilizing PLGA particles to enhance the anti-leukemic immunity induced by WT1 antigen.…”

“…PLGA MPs carrying WT1 and/or CpG were formulated using the standard w/o/w approach (Ma et al, 2012). Confocal images revealed that the particles were spherical in shape (Fig.…”

“…The star indicates a statistically signifi cant difference. (Kovacsovics-Bankowski and Rock, 1995;Zhang et al, 2011;Ma et al, 2012). PLGA particles can protect the antigen from enzymatic degradation (Kovacsovics-Bankowski and Rock, 1995), increase the effi ciency of antigenloading (Hanlon et al, 2011;Ma et al, 2012), facilitate cross-presentation of the antigen (Ma et al, 2011), and co-deliver adjuvant into DCs (Zhang et al, 2007).…”