Enhancement of T helper type 1 immune responses against hepatitis B virus core antigen by PLGA nanoparticle vaccine delivery

Currently, there is a need for therapeutic vaccines that are effective in inducing robust T helper type 1 (Th1) immune responses capable of mediating viral clearance in chronic hepatitis B infection. Hepatitis B therapeutic vaccines were designed and formulated by loading the hepatitis B core antigen (HBcAg) into poly(d,l-lactic-acid-co-glycolic acid) (PLGA) nanoparticles with or without monophospholipid A (MPLA), a Th1-favoring immunomodulator. These particles were around 300 nm in diameter, spherical in shape and had approximately 50% HBcAg encapsulation efficiency. A single immunization with a vaccine formulation containing (MPLA+HBcAg) coformulated in PLGA nanoparticles induced a stronger Th1 cellular immune response with a predominant interferon-γ (IFN-γ) profile than those induced by HBcAg alone, free (HBcAg+MPLA) simple mixture or HBcAg-loaded nanoparticles in a murine model. More importantly, the level of HBcAg-specific IFN-γ production could be increased further significantly by a booster immunization with the (HBcAg+MPLA)-loaded nanoparticles. In summary, these results demonstrated that codelivery of HBcAg and MPLA in PLGA nanoparticles promoted HBcAg-specific Th1 immune responses with IFN-γ production. These findings suggest that appropriate design of the vaccine formulation and careful planning of the immunization schedule are important in the successful development of effective HBV therapeutic vaccines.