In this proof-of-concept study, we first demonstrated that the fusion of viral HA1 antigen, with either Fc alone or both Fd and Fc, was able to induce cross-neutralizing antibodies strong enough against various subtypes of H5N1 virus, which, in turn, could provide cross-protection against infections of different clades of H5N1 virus in cell cultures in vitro and in mouse models in vivo. Here, ELP1 is linked to infection.