A polypeptide is provided that comprises an actinohivin variant polypeptide having an amino acid sequence selected from SEQ ID NOS: 4-12. The polypeptide can be provided as part of a fusion protein that includes the actinohivin variant polypeptide and either a fragment crystallizable domain of an antibody (Fc), a fragment antigen-binding domain of an antibody (Fab), or a single chain variable fragment of an antibody (scFv). Isolated nucleic acid molecules encoding the polypeptides are also provided along with vectors and plant cells capable of expressing the polypeptides. Methods of treating an infection of a subject by an enveloped virus are further provided and include administering an effective amount of the polypeptides to a subject.
