Abstract: A heteropentamer composed of a fusion monomer (32) comprising a fusion protein of an antigenic amino acid sequence and an amino acid sequence of a monomer of a mucous membrane-binding protein and a nonfusion monomer (20) of an amino acid sequence of a monomer of a mucous membrane-binding protein. A homopentamer composed of a fusion monomer including a fusion protein of an antigen derived from an envelope protein of Japanese encephalitis virus and an amino acid sequence of a monomer of a mucous membrane-binding protein. These heteropentamer and the homopentamer can be used as a vaccine.