Myxoma virus M063R is a host range gene essential for virus replication in rabbit cells

Abstract

The myxoma virus M063R gene product exhibits some sequence similarity to the poxvirus host range gene, C7L, of vaccinia virus. To address the potential host range function of the M063R gene product in rabbits, a deletion mutant of myxoma virus (vMyx63KO) was generated and characterized. vMyx63KO replicated to normal titre levels and produced foci that were indistinguishable from those produced by MV in vitro in a monkey kidney cell line (BGMK) that are permissive for wild type MV. However, vMyx63KO failed to replicate in all rabbit cell lines tested, including both primary and established cells lines, as well as cells derived from a variety of tissues. M063R expression was not required for myxoma virus binding, entry or early gene expression, whereas DNA replication was aborted and late genes were not expressed in vMyx63KO infected rabbit cells. Thus, the replication block for vMyx63KO in rabbit cells preceded the stage of late gene expression and DNA replication. Finally, an in vivo pathogenesis study indicated that vMyx63KO failed to cause any signs of classic myxomatosis in infected rabbits, but functioned as a non-replicating vaccine and provided protection for subsequent challenge by wild type myxoma virus. Altogether, these observations demonstrate that M063R plays a critical role in determining the host specificity of myxoma virus in rabbit cells.

Proteomic screening of variola virus reveals a unique NF-κB inhibitor that is highly conserved among pathogenic orthopoxviruses

“…For control purposes, cells were also cotransfected with the NF-B1 expression plasmid along with either an empty pANT7_cGST plasmid or a control pANT7_cGST plasmid expressing an irrelevant control protein, M063 (MYXV-M063) from myxoma virus (27). As seen in Fig.…”

Construction and testing of a novel host-range defective myxoma virus vaccine with the M063 gene inactivated that is non-permissive for replication in rabbit cells

“…The myxoma virus early gene M063 is a host-range gene essential for productive replication of the virus in primary rabbit cells and in all rabbit cell lines tested in vitro [3]. Targeted deletion of this gene by insertional inactivation produces a tropism-defective virus that can be propagated in non-rabbit cells lines but cannot complete its replication in rabbit cells in vitro or infected rabbits in vivo.…”

“…Targeted deletion of this gene by insertional inactivation produces a tropism-defective virus that can be propagated in non-rabbit cells lines but cannot complete its replication in rabbit cells in vitro or infected rabbits in vivo. The M063 deletion virus enters rabbit cells and expresses early viral genes but the infection aborts prior to the expression of late genes [3]. Protection following challenge with virulent myxoma virus has been demonstrated at 16 days after infection of laboratory rabbits with an M063 knock-out virus [3].…”

“…The M063 deletion virus enters rabbit cells and expresses early viral genes but the infection aborts prior to the expression of late genes [3]. Protection following challenge with virulent myxoma virus has been demonstrated at 16 days after infection of laboratory rabbits with an M063 knock-out virus [3]. Thus it has the potential to be a completely safe vaccine for rabbits since it cannot complete its replication in this host and therefore cannot disseminate within an immunized rabbit or be transmitted to other rabbits.…”

“…M063 is one of a number of identified hostrange genes in poxviruses including the C7L and K1L genes of vaccinia virus [3,21,24]. Host-range mutant viruses such as Modified Vaccinia Ankara (MVA) and NYVACC, which cannot complete their replication in human cells, are potential candidates for safe vaccines against smallpox [19].…”