Microneedle Delivery of an Adjuvanted Microparticulate Vaccine Induces High Antibody Levels in Mice Vaccinated against Coronavirus

Abstract

This ‘proof-of-concept’ study aimed to test the microparticulate vaccine delivery system and a transdermal vaccine administration strategy using dissolving microneedles (MN). For this purpose, we formulated poly(lactic-co-glycolic) acid (PLGA) microparticles (MP) encapsulating the inactivated canine coronavirus (iCCoV), as a model antigen, along with adjuvant MP encapsulating Alhydrogel® and AddaVax. We characterized the vaccine MP for size, surface charge, morphology, and encapsulation efficiency. Further, we evaluated the in vitro immunogenicity, cytotoxicity, and antigen-presentation of vaccine/adjuvant MP in murine dendritic cells (DCs). Additionally, we tested the in vivo immunogenicity of the MP vaccine in mice through MN administration. We evaluated the serum IgG, IgA, IgG1, and IgG2a responses using an enzyme-linked immunosorbent assay. The results indicate that the particulate form of the vaccine is more immunogenic than the antigen suspension in vitro. We found the vaccine/adjuvant MP to be non-cytotoxic to DCs. The expression of antigen-presenting molecules, MHC I/II, and their costimulatory molecules, CD80/40, increased with the addition of the adjuvants. Moreover, the results suggest that the MP vaccine is cross presented by the DCs. In vivo, the adjuvanted MP vaccine induced increased antibody levels in mice following vaccination and will further be assessed for its cell-mediated responses.

An Adjuvanted Inactivated SARS-CoV-2 Microparticulate Vaccine Delivered Using Microneedles Induces a Robust Immune Response in Vaccinated Mice

“…The heat-inactivated SARS-CoV-2 (iSARS-CoV-2) vaccine MP and adjuvant MP (Alhydrogel ® and AddaVax™) were prepared using a double emulsion method with solvent evaporation as described previously [ 9 , 33 , 34 , 35 ]. First, the inactivated SARS-CoV-2 antigen (1% loading) in a pH 7.4 phosphate buffer was added to PLGA in DCM solution (2% w / v ) and probe-homogenized at 17,000 RPM using a 30 s on/30 s off cycle for 2 min (primary emulsion).…”

“…Therefore, they are poorly recognized and are rapidly cleared by the host’ immune system [ 32 ]. In the past, we have demonstrated that encapsulating the vaccine antigen in a polymer matrix can enhance the immunostimulatory activity of the antigen [ 26 , 33 , 34 , 35 ]. In the present study, the vaccine antigen and adjuvants are encapsulated in polymer matrices using poly(lactic-co-glycolic acid) (PLGA) to form an effective carrier system.…”

“…AddaVax™ (MF59-like) is a squalene-based nano-emulsion that induces cytokines and chemokines involved in the recruitment, activation, and maturation of APCs [ 46 , 47 , 48 ]. Previously, we have tested the adjuvants Alhydrogel ® and AddaVax™, encapsulated in polymer matrices in a model microparticulate vaccine formulation [ 35 ]. We observed that adjuvants and an inactivated model antigen yielded increased antibody levels in vaccinated mice [ 35 ].…”

“…Previously, we have tested the adjuvants Alhydrogel ® and AddaVax™, encapsulated in polymer matrices in a model microparticulate vaccine formulation [ 35 ]. We observed that adjuvants and an inactivated model antigen yielded increased antibody levels in vaccinated mice [ 35 ]. Therefore, Alhydrogel ® and AddaVax™ were used in this study as adjuvants to enhance the immunogenicity of the inactivated SARS-CoV-2 antigen.…”

“…Previously, as a proof of concept, we demonstrated that MN administration of an inactivated microparticulate vaccine utilizing canine coronavirus (CCoV) as a model antigen increased antibody levels in vaccinated mice [ 35 ]. In this current follow-up study, we have summarized the results of testing an adjuvanted inactivated SARS-CoV-2 MP vaccine administered to mice using quick-dissolving MNs.…”