In this study, we demonstrate how encapsulating a conserved influenza ectodomain matrix-2 protein virus-like particle (M2e5x VLP) into a pre-crosslinked bovine serum albumin (BSA) polymeric matrix enhances in vitro antigen immunogenicity and in vivo efficacy. The spray-dried M2e5x VLP-loaded BSA microparticles (MPs) showed enhanced stimulation of antigen presenting cells (APCs), as confirmed through nitrite production and increased antigen-cell interactions seen in real time using live-cell imaging. Next, to further boost the immunogenicity of M2e5x VLP microparticles, M2e5x MPs were combined with Alhydrogel® and monophosphoryl lipid-A (MPL-A®) adjuvant microparticles. M2e5x VLP MPs and the combination VLP M2e5x VLP + Alhydrogel® + MPL-A® MPs elicited a significant increase in the expression of antigen-presenting molecules in dendritic cells compared to M2e5x VLP alone. Lastly, for preliminary evaluation of in vivo efficacy, the vaccine was administered in mice through the skin using an ablative laser. The M2e5x VLP + Alhydrogel® + MPL-A® MPs were shown to induce high levels of M2e-specific IgG antibodies. Further, a challenge with live influenza revealed heightened T-cell stimulation in immune organs of mice immunized with M2e5x VLP + Alhydrogel® + MPL-A® MPs. Hence, we utilized the advantages of both VLP and polymeric delivery platforms to enhance antigen immunogenicity and adaptive immunity in vivo.
Keywords: influenza; live-cell imaging; microparticle; vaccine; virus-like particle.