Co encapsulation of antigens and adjuvants in polymeric nanoparticles for the development of an oral vaccine formulation.

PRADO, LINEIA; PASQUEVICH K; BRUNO LAURA; CORIA L.; CASSATARO JULIANA

Universidad Católica Argentina, Buenos Aires, Argentina

Congreso; 14th Latin American and Caribbean Congress of Immunology (ALACI 2024).; 2024

Oral vaccines are easy to administer but their development still faces many challenges, such as the hostile gastrointestinal environment. The protease inhibitor U-Omp19 from Brucella spp. was shown to be an oral vaccine adjuvant that protects co-delivered antigens from proteolysis in the gastrointestinal tract and increases antigen specific adaptive immune responses. In this work, we aim to protect vaccine formulation by encapsulating it in poly-(lactic-co glycolic)-acid (PLGA) nanoparticles. Eudragit, a polymer that dissolves at a pH higher than 7.4 was used to cover these nanoparticles and prevent antigen absorption in the duodenum where the response could be tolerogenic, and to deliver the vaccine to the large intestine where adaptive immune responses can be triggered. Nanoparticles encapsulating OVA or HbsAg as antigens were synthesized using the double emulsion- solvent evaporation (DE-SE) method, in both cases U-Omp19 was used as the adjuvant. Encapsulation efficiency was determined by SDS-PAGE. Characterization was carried out using DLS, SEM and z-potential. HT-29 and Caco-2 cell lines were utilized to evaluate antigen internalization using flow-cytometry. BALB/c mice were orally immunized with the antigen and adjuvant encapsulated in nanoparticles with control groups receiving the non-encapsulated vaccine formulation. Specific antibody responses were determined in stool samples by ELISA. Four weeks after the last immunization adaptive immune responses were evaluated in the Peyer Patches and spleen by flow cytometry. IFN-g was determined in splenocyte cell culture supernatants by ELISA. An increase in the internalization of the encapsulated antigen was observed compared with the non-encapsulated antigen in both cell lines. Mice immunized with nanoparticles (HbsAg+ U Omp19) showed a significant increase in both specific IgA response, follicular T cell population in the spleen and of B220+ CD19+ IgA+/IgG+ antigen specific cells in the Payer Patches in comparison to the control groups. Mice immunized with nanoparticles (OVA+ U Omp19), showed a significant increase in IFN-g in splenocyte cell culture supernatants after being stimulated with OVA. In conclusion, we developed polymeric nanoparticles that encapsulates both the antigen and the adjuvant increasing antigen internalization, IgA specific antibodies in feces, an increase in the immune response mediated by B cells in the Payer Patches, and Th1 response.