Functional F11L and K1L genes in modified vaccinia virus Ankara restore virus-induced cell motility but not growth in human and murine cells.

Modified vaccinia virus Ankara (MVA) was generated by serial passaging in chicken embryo fibroblasts. During this attenuation, MVA lost the capacity to productively grow in human and most other mammalian cell lines, as well as acquiring a multitude of deletions and mutations in the MVA genome. This means that the precise molecular basis for the MVA host-range restriction is still unknown. The vaccinia virus (VACV) genes F11L and K1L are mutated or truncated in MVA. F11L was previously implicated in VACV-induced cell motility and virion maturation. Here, we demonstrate that the restoration of F11L gene expression in MVA rescued virus-induced cell motility, but had no impact on MVA virion maturation and host-range restriction. Additional insertion of the K1L gene, which restores MVA replication in RK-13 cells, was not sufficient to extend MVA growth capacity to other mammalian cells.