In-vitro and in-vivo comparison of rSAG1-loaded PLGA prepared by encapsulation and adsorption methods as an efficient vaccine against Toxoplasma gondii

The emergence of delivery vehicles has revolutionized vaccine development. Although vaccination is the most effective approach to eradicate toxoplasmosis, there is nonetheless no commercially available human vaccine against Toxoplasma gondii. Here, we applied poly dl-lactide-co-glycolide (PLGA) nanoparticles loaded by recombinant surface antigen 1 (rSAG1) as vaccine delivery platform. In order to assess the influence of loading method on nanoparticle immunogenicity, rSAG1-PLGA nanoparticles were prepared by both adsorption and encapsulation approaches. BALB/c mice were subcutaneously vaccinated twice with a 3-week interval by rSAG1-encapsulated PLGA, rSAG1-adsorbed PLGA, two control groups received rSAG1 and PLGA and one group remained unvaccinated. Nanoparticles characterization, rSAG1 release, cellular and humoral immune responses and the survival time after challenge with T.gondii RH tachyzoite were investigated. Mice vaccinated with both rSAG1- PLGA nanoparticles elicited higher IFN-γ, specific anti-T.gondii IgG antibodies and longer survival time than controls. However, rSAG1-adsorbed PLGA stimulated significantly higher amount of IFN-γ and IgG2a titers compared to rSAG1-encapsulated PLGA. This study suggests adsorption as a more appropriate approach than encapsulation in antigen loading on PLGA as vaccine vehicle. It is the first report that the effects of preparation method of PLGA nanoparticles loaded by identical antigen on their characteristics and immunogenicity are evaluated and compared. [Display omitted]