The preparation and characterization of PLG nanoparticles with an entrapped synthetic TLR7 agonist and their preclinical evaluation as adjuvant for an adsorbed DTaP vaccine.

The design of safe and potent adjuvants able to enhance and modulate antigen-specific immunity is of great interest for vaccine research and development. In the present study, negatively charged poly(lactide-co-glycolide) (PLG) nanoparticles have been combined with a synthetic immunepotentiator molecule targeting the Toll-like receptor 7. The selection of appropriate preparation and freeze-drying conditions resulted in a PLG-based adjuvant with well-defined and stable physico-chemical properties. The adjuvanticity of such nanosystem has later been evaluated in the mouse model with a diphtheria-tetanus-pertussis (DTaP) vaccine, on the basis of the current need to improve the efficacy of acellular pertussis (aP) vaccines. DTaP antigens were adsorbed onto PLG nanoparticles surface, allowing the co-delivery of TLR7a and multiple antigens through a single formulation. The entrapment of TLR7a into PLG nanoparticles resulted in enhanced IgG and IgG2a antibody titers. Notably, the immune potentiator effect of TLR7a was less evident when it was used in not-entrapped form, indicating that co-localization of TLR7a and antigens is required to adequately stimulate immune responses. In conclusion, the rational selection of adjuvants and formulation here described resulted as a highly valuable approach to potentiate and better tailor DTaP vaccine immunogenicity.

Combination adjuvants for the induction of potent, long-lasting antibody and T-cell responses to influenza vaccine in mice.

Influenza is controlled by protective titres of neutralizing antibodies, induced with the help of CD4 T-cells, and by antiviral T-cell effector function. Adjuvants are essential for the efficient vaccination of a naïve population against avian influenza. We evaluated a range of adjuvants for their ability to enhance, in naïve mice, protective hemagglutination inhibition (HI) titres, which represent the generally accepted correlate of protection, virus-neutralizing titres and T-cell responses to a new generation influenza vaccine produced in cell culture. The selected adjuvants include alum, calcium phosphate (CAP), MF59, the delivery system poly-(lactide co-glycolide) (PLG) and the immune potentiator CpG. MF59 was clearly the most potent single adjuvant and induced significantly enhanced, long-lasting HI and neutralizing titres and T-cell responses in comparison to all alternatives. The combination of alum, MF59, CAP or PLG with CpG generally induced slightly more potent titres. The addition of CpG to MF59 also induced a more potent Th1 cellular immune response, represented by higher IgG2a titres and the induction of a strongly enhanced IFN-gamma response in splenocytes from immunized mice. These observations have significant implications for the development of new and improved flu vaccines against pandemic and inter-pandemic influenza virus strains.