The poxvirus C7L host range factor superfamily

Host range factors, expressed by the poxvirus family, determine the host tropism of species, tissue, and cell specificity. C7L family members exist in the genomes of most sequenced mammalian poxviruses, suggesting an evolutionarily conserved effort adapting to the hosts. In general, C7L orthologs influence the host tropism in mammalian cell culture, and for some poxviruses it is essential for the complete viral life cycle in vitro and in vivo. The C7L family members lack obvious sequence homology with any other known viral or cellular proteins. Here we review recent findings from an evolutionary perspective and summarize recent progress that broadens our view on the role of C7L family members in mediating poxvirus host range and antagonizing the host defense system.

► C7L family members have evolved to adapt to their corresponding hosts.
► Not all C7L family members function via the same mechanism.
► Some C7L members can overcome host restriction and inhibit type I IFN induced antiviral activities.
► MYXV-M062 binds to antagonize host SAMD9, providing clues on other C7L orthologs’ functions.