Disclosed herein are polynucleotides encoding fusion proteins, the fusion proteins comprising a vaccinia virus envelope protein, such as A13 or part thereof and at least one complement regulatory protein, such as CD35, CD55, CD59, CD46, CR1, Factor H, VCP, MOPICE, SPICE and CCPH, or a functional fragment thereof. Modified vaccinia virus vectors and vaccinia virus virions are also disclosed, as are therapeutic uses and methods for treatment of cancers and/or proliferative diseases or disorders.