Self-assembling ferritin nanoparticles displaying glycoprotein B epitopes induce robust humoral and mucosal immunity...

Feline Herpesvirus 1 (FHV-1) poses a significant threat to feline health, yet current vaccines exhibit limited mucosal immunogenicity. Self-assembling nanoparticles (SANPs) present a novel strategy for enhancing mucosal immunization through efficient multivalent antigen display. In this study, epitopes from FHV-1 glycoprotein B (FHB₁ and FHB₂) were fused to ferritin to create FHB₁F and FHB₂F nanoparticles. Following expression and purification, SANPs were characterized using dynamic light scattering and transmission electron microscopy, then administered to mice via subcutaneous or mucosal routes in three doses. Immunogenicity was assessed by measuring serum antibody titers through ELISA and evaluating neutralizing activity via micro-neutralization assays. Cytokine secretion related to Th1 and Th2 responses was measured, and T-cell responses were analyzed using flow cytometry. Results showed that SANPs significantly enhanced cytokine secretion, elicited robust humoral immunity, and stimulated both CD4⁺ and CD8⁺ T-cell responses. Secretory IgA (sIgA) levels were detectable post-intranasal immunization with both formulations, indicating effective mucosal response. Notably, FHB₂F induced higher serum neutralizing antibody titers than FHB₁F across both administration routes. Twelve weeks post-immunization, antibody levels remained elevated in mice receiving any nanoparticle formulation. This study demonstrates that SANPs can generate significant and long-lasting humoral and cellular immune responses, with FHB₂F emerging as a promising vaccine candidate for controlling FHV-1 infections in felines.