Generation and characterization of a Cowpox virus mutant lacking host range factor CP77

► A vCPXVΔCP77 mutant was constructed by bacterial artificial chromosome mutagenesis. ► Integrity and functionality of the vCPXVΔCP77 mutant were confirmed. ► Host restriction of vCPXVΔCP77 in CHO cells could be complemented by expression of CP77. ► No other cell type or species origin mediating a CP77 dependent host range effect could be identified. ► The vCPXVΔCP77 mutant can be applied to determine additional functions of CP77.