Self-assembling trivalent nanoparticle vaccine enables multivalent antigen display and potent cross-protection against fowl adenovirus serotypes 4, 8b, and 11

Abstract

Hepatitis-hydropericardium syndrome, caused by fowl adenovirus serotype 4(FAdV-4), and inclusion body hepatitis, caused by fowl adenovirus 8b and 11 (FAdV-8b and FAdV-11), have become widespread in China, resulting in substantial economic losses. Vaccination remains one of the most effective strategies for disease prevention and control. However, no trivalent subunit vaccine targeting FAdV-4, FAdV-8b, and FAdV-11 has been reported. Therefore, we developed a trivalent nanoparticle vaccine (4-8-11 NPs) by covalently conjugating the fiber knob domains of FAdV-4, FAdV-8b, and FAdV-11 to the surface of Mi3 nanoparticles using the SpyTag/SpyCatcher modular system. The safety and efficacy of the vaccine were evaluated through protein expression analysis, physicochemical characterization, and in vivo immune challenge experiments. The 4-8-11 NPs exhibited high biocompatibility and stability and were preferentially taken up by antigen-presenting cells, thereby promoting their maturation and cytokine production. In vivo studies confirmed that immunization with 4-8-11 NPs induced high titers of neutralizing antibodies and serotype-specific IgG, promoted lymphocyte proliferation, and elicited a balanced Th1/Th2 cytokine response, outperforming the corresponding monomeric antigen. In vivo imaging revealed that 4-8-11 NPs prolonged antigen retention at the injection site and enhanced antigen accumulation in the spleen. Challenge studies demonstrated complete protection against FAdV-4, FAdV-8b, and FAdV-11, with marked reductions in clinical signs, histopathological lesions, and viral load. These findings indicate that the Mi3-based trivalent nanoparticle vaccine elicits robust cross-serotype immune protection and represents a promising strategy for multivalent vaccine development against FAdV.