Vaccination is a promising strategy to trigger and boost immune responses against cancer or infectious disease.
We have designed, synthesized and characterized aliphatic-polyester (poly(lactic-co-glycolic acid) (PLGA)
nanoparticles (NP) to investigate how the nature of protein association (adsorbed versus entrapped) and
polymer/surfactant concentrations impact on the generation and modulation of antigen-specific immune
The ability of the NP formulations to target dendritic cells (DC), be internalized and activate the T cells was
characterized and optimized in vitro and in vivo using markers of DC activation and co-stimulatory molecules.
Ovalbumin (OVA) was used as a model antigen in combination with the engraftment of CD4+ and CD8+ T cells,
carrying a transgenic OVA-responding T cell receptor (TCR), to trace and characterize the activation of antigenspecific
CD4+ and CD8+ lymph node T cells upon NP vaccination. Accordingly, the phenotype and frequency of
immune cell stimulation induced by the NP loaded with OVA, isolated or in combination with synthetic
unmethylated cytosine-phosphate-guanine (CpG) oligodeoxynucleotide (ODN) motifs, were characterized.
DC-NP interactions increased with incubation time, presenting internalization values between 50 and 60%
and 30–40%, in vitro and in vivo, respectively. Interestingly, animal immunization with antigen-adsorbed NP upregulated
major histocompatibility complex (MHC) class II (MHCII), while NP entrapping the antigen upregulated
MHCI, suggesting a more efficient cross-presentation. On the other hand, rather surprisingly, the
surfactant used in the NP formulation had a major impact on the activation of antigen presenting cells (APC). In
fact, DC collected from lymph nodes of animals immunized with NP prepared using poly(vinil alcohol) (PVA), as
a surfactant, expressed significantly higher levels of CD86, MHCI and MHCII. In addition, those NP prepared
with PVA and co-entrapping OVA and the toll-like receptor (TLR) ligand CpG, induced the most profound
antigen-specific T cell response, by both CD4+ and CD8+ T cells, in vivo.
Overall, our data reveal the impact of NP composition and surface properties on the type and extension of
induced immune responses. Deeper understanding on the NP-immune cell crosstalk can guide the rational
development of nano-immunotherapeutic systems with improved and specific therapeutic efficacy and avoiding