Degradable emulsion as vaccine adjuvant reshapes antigen-specific immunity and thereby ameliorates vaccine efficacy

Abstract

This study describes the feasibility and adjuvant mechanism of a degradable emulsion for tuning adaptive immune responses to a vaccine antigen. We featured a mouse model with ovalbumin (OVA) as the antigen to deepen our understanding of the properties of a degradable emulsion-based adjuvant, dubbed PELC, interacting with immune cells and to elucidate their roles in vaccine immunogenicity in vivo. First, we demonstrated that the emulsion, which is stabilized by an amphiphilic bioresorbable polymer, shows degradation in mimic human body conditions and considerable tolerance in vivo. Then, we confirmed the model protein could be loaded into the emulsion and released from the matrix in a sustained manner, subsequently driving the production of antigen-specific antibodies. We also comprehended that PELC not only recruits antigen-presenting cells (APCs) to the injection site but also induces the activation of the recruited APCs and migration to the draining lymph nodes. As an adjuvant for cancer immunotherapy, PELC-formulated OVA could strongly enhance antigen-specific T-cell responses as well as anti-tumor ability with respected to non-formulated OVA, using OVA protein/EG7 cells as a tumor antigen/tumor cell model. Accordingly, our data paved the way for the clinical application of degradable emulsions based on amphiphilic bioresorbable polymers as vaccine adjuvants.

Nanoemulsion adjuvantation strategy of tumor-associated antigen therapy rephrases mucosal and immunotherapeutic signatures following intranasal vaccination

“…We have previously optimized a ready-to-use emulsion adjuvant dubbed PELC, which is cored by squalene (an isoprenoid hydrocarbon with six unsaturated double bonds) and emulsified by Span85 (sorbitan trioleate) and a bioresorbable polymer poly(ethylene glycol)block-poly(lactide-co-ε-caprolactone) (PEG-b-PLACL), suspending in phosphate-buffered saline (PBS). [4][5][6][7] Following parenteral injection, our results suggest that unsaturated squalene oil was more powerful than saturated squalane oil to induce reactive oxidative speciesmediated antigen uptake 8 ; moreover, adjuvantation with the aid of PELC may be a prospective strategy to manipulate antigen-specific immune responses and to build on rational vaccine design and fabrication in prophylactic and therapeutic applications. [5][6][7] However, intranasal vaccination with PELC in the absence of immunomodulatory agents does not elicit forceful immune responses, 4 5 and thus an appreciative condition for mucosal delivery should still be optimized.…”

“…For PELC@PE preparation, a mixture comprising 120 mg of diblock copolymer PEG-b-PLACL, 0.8 mL of PBS, 0.935 mL of squalene and 0.165 mL of Span85 was first emulsified by means of a homogenizer (Polytron PT 2500E, Kinematica, Swiss), as previously described. [5][6][7] Then, 200 µL of the stock emulsion was redispersed into 1800 µL of PBS in a test tube, and allowed to mix the emulsified suspension using a rotator at a mild condition (5 rpm) for 1 hour. Next, 10 µL aliquot of a specimen was added to 990 µL of PBS, rendering a final diluted sample (referred to as PELC@PE).…”

“…The sections were deparaffinized and rehydrated by sequentially immersing into xylene and ethanol as previously described. 6 For antigen retrieval, the hydrated slides of nasal mucosal and tumor tissues were immersed in Trilogy at 90°C for 30 min, followed with 3% hydrogen peroxide (H 2 O 2 ) for 15 min to block the endogenous peroxidase activity. After washing with PBS, the slides were further blocked with 2.5% normal horse serum for 1 hour.…”

“…The steady-state mRNA expression levels, T-bet and RORγt, were measured by reverse transcription PCR in a manner similar to our previous study. 6 The results are shown as the density ratio of the interest gene to the reference standard (β-actin). At 72 hours, the supernatants were collected from triplicate cultures and tested for interferon gamma (IFN-γ) and interleukin 17 (IL-17) concentrations (DueSet ELISA Development Kit, R&D Systems) following the manufacturer's instructions.…”

“…Emulsion adjuvants are a potent tool for effective vaccination against infectious disease and cancer. [3][4][5][6][7][8] Despite progress in this field, no intranasal vaccine or immunotherapy formulated with this type of adjuvants is currently registered for human use to protect against or treat disease. Potential safety concerns and low immunity generated in a manner suitable for patients remain major challenges.…”