Controlled release of inactivated influenza virus and -galactosylceramide from PLGA microparticles results in long-term protection against influenza infection

Abstract The objective of this study was to develop biodegradable microparticles with continuous release that can enhance and extend the long-term protection of single-dose vaccines. Several formulations of Poly (lactic-co-glycolic acid) (PLGA) microparticles were synthesized using a double emulsion solvent evaporation technique to encapsulate inactivated A/PR/8/34 (PR8) H1N1 influenza virus in combination with the invariant natural killer T (NKT) cell agonist α-galactosylceramide (α-GalCer). The most efficient controlled release particle formulations were injected into C57BL/6J mice. Additional control mice were injected with PBS alone, inactivated PR8 dissolved in PBS, or inactivated PR8 and α-GalCer dissolved in PBS. Thirty weeks after vaccination, mice were challenged with a lethal dose of live homologous virus. Mice immunized with the microparticle vaccine survived the infection and had reduced clinical disease and decreased weight loss compared to unvaccinated mice. After vaccination, mice injected microparticles presented a gradual increase production of PR8-specific IgGs that was dominated by IgG1 isotype that is usually produced by T helper (Th) 2 responses. In contrast, mice that received soluble vaccine presented a rapid antibody response that was dominated by antibodies of the Th1-associated IgG2a isotype. Collectively, these results demonstrate the potential of PLGA-based single-dose microparticle vaccines for providing long-term protection against influenza infection and potentially other pathogens. Supported by grants from USAMRAA (W81XWH-19-1-0005)