A fusion protein comprises a nanocage monomer； and an antibody or fragment thereof linked to the nanocage monomer, the antibody or fragment thereof comprising a first member of a binding pair； wherein a plurality of the fusion proteins self-assemble to form a nanocage in which a plurality of the antibodies or fragments thereof decorate the exterior surface of the nanocage, whereby the first member of the binding pair is exposed for interacting with a second member of a binding pair.
