Immunogenicity of norovirus VP1-expressing silkworm (Bombyx mori) pupae as an edible vaccine candidate

Norovirus (NV) gastroenteritis remains a global health challenge, particularly affecting infants and the elderly. Despite its significant clinical impact, no licensed vaccine is currently available. This study explores a novel approach to NV vaccine development using the silkworm-baculovirus expression vector system (silkworm-BEVS), focusing on non-purified VP1-expressing silkworm pupae as a potential edible vaccine candidate. We assessed the immunogenicity of orally administered VP1-expressing silkworm pupae in mice using two delivery formats: crude pupal suspensions administered by oral gavage and freeze-dried whole pupae provided by free-feeding. Oral gavage induced dose- and time-dependent antigen-specific IgG in serum and IgA in intestinal lavage fluid (ILF). The serum antibodies also showed HBGA-blocking activity. Importantly, free-feeding also elicited robust antigen-specific IgG and IgA responses. Pooled sera and ILF from free-fed mice showed neutralizing activity against NV in a human induced pluripotent stem cell (iPSC)-derived intestinal epithelial cell-based assay. Our findings demonstrate that oral administration of VP1-expressing silkworm pupal preparations induces both systemic and mucosal immune responses, which may be relevant to protective immunity against NV. Collectively, these results support the potential of non-purified VP1-expressing silkworm pupae as an edible vaccine candidate and provide a foundation for further development of silkworm-BEVS-based edible vaccines.