Biodegradable PLGA-b-PEG Nanoparticles Induce T Helper 2 (Th2) Immune Responses and Sustained Antibody Titers via TLR9 Stimulation

Abstract

Sustained immune responses, particularly antibody responses, are key for protection against many endemic infectious diseases. Antibody responses are often accompanied by T helper (Th) cell immunity. Herein we study small biodegradable poly (ethylene glycol)-b-poly (lactic-co-glycolic acid) nanoparticles (PEG-b-PLGA NPs, 25–50 nm) as antigen- or adjuvant-carriers. The antigen carrier function of PEG-b-PLGA NPs was compared against an experimental benchmark polystyrene nanoparticles (PS NPs, 40–50 nm), both conjugated with the model antigen ovalbumin (OVA-PS NPs, and OVA-PEG-b-PLGA NPs). The OVA-PEG-b-PLGA NPs induced sustained antibody responses to Day 120 after two immunizations. The OVA-PEG-b-PLGA NPs as a self-adjuvanting vaccine further induced IL-4 producing T-helper cells (Th2), but not IFN-γ producing T-cells (Th1). The PEG-b-PLGA NPs as a carrier for CpG adjuvant (CpG-PEG-b-PLGA NPs) were also tested as mix-in vaccine adjuvants comparatively for protein antigens, or for protein-conjugated to PS NPs or to PEG-b-PLGA NPs. While the addition of this adjuvant NP did not further increase T-cell responses, it improved the consistency of antibody responses across all immunization groups. Together these data support further development of PEG-b-PLGA NPs as a vaccine carrier, particularly where it is desired to induce Th2 immunity and achieve sustained antibody titers in the absence of affecting Th1 immunity.

Biocompatible Lipid Polymer Cationic Nanoparticles for Antigen Presentation

“…The search for cationic NPs with potential as adjuvants for vaccines yielded many examples of polymer lipid [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ], silica/cationic lipid [ 18 , 19 ], cationic polymer [ 20 , 21 , 22 ], gold/cationic polymer NPs [ 23 ], and iron-oxide/cationic polymer/antigen NPs [ 24 ]. Among the most important requirements of adjuvants for vaccines are biocompatibility and nanometric size [ 25 ].…”

Immunopotentiation by Lymph-Node Targeting of a Malaria Transmission-Blocking Nanovaccine

“…The UF6b construct, a dimer of a subdomain of the mosquito midgut protein, AnAPN1, was shown to focus the immune system response away from non-protecting immunodominant epitopes and towards neutralizing epitopes (8). To boost this neutralizing antibody titer, a biodegradable PLGA-b-PEG NP vaccine was leveraged to deliver antigenic (UF6b) and adjuvant (CpG ODN ISS 1018) stimuli directly to the lymph node as previously demonstrated and shown in this work (Supplemental Figure 2) (20,21). For ease of manufacture, UF6b-NPs and CpG-NPs were fabricated separately and then mixed to obtain the UF6b and CpG doses and ratios of interest.…”

“…NPs generated using the FNP method and subsequent conjugation with CpG-1018 and UF6b construct are reproducible from batch to batch (Figure 1 and Supplemental Table 1). The densities of UF6b antigen and CpG-1018 adjuvant were selected based off our previously published studies (20,21).…”

“…It has previously been demonstrated that synthesizing NPs in the size range of viruses enables their quick localization to the lymph nodes after s.c. or i.d. administration, making these vaccines more efficient at eliciting an immune response (19)(20)(21). In contrast, NPs larger than 100 nm will generally remain at the injection site (22)(23)(24)(25).…”

“…Given the proven record of CpG-1018 in the clinic for induction of high antigen-specific antibody titer, we selected CpG-1018 ISS as our adjuvant for further study with our UF6b AnAPN1 immunogen construct. Furthermore, previously published studies with and without model antigen ovalbumin have provided evidence to further test the efficiency of the immune response to the UF6b antigen with 30 nm NPs synthesized using flash nanoprecipitation (FNP) which produced well controlled size and narrow-size distribution particles (20,21).…”