Abstract
As a group, poxviruses have been shown to infect a wide variety of animal species. However, there is individual variability in the range of species able to be productively infected. In this study, we observed that ectromelia virus (ECTV) does not replicate efficiently in cultured rabbit RK13 cells. Conversely, vaccinia virus (VACV) replicates well in these cells. Upon infection of RK13 cells, the replication cycle of ECTV is abortive in nature, resulting in a greatly reduced ability to spread among cells in culture. We observed ample levels of early gene expression but reduced detection of virus factories and severely blunted production of enveloped virus at the cell surface. This work focused on two important host range genes, named E3L and K3L, in VACV. Both VACV and ECTV express a functional protein product from the E3L gene, but only VACV contains an intact K3L gene. To better understand the discrepancy in replication capacity of these viruses, we examined the ability of ECTV to replicate in wild-type RK13 cells compared to cells that constitutively express E3 and K3 from VACV. The role these proteins play in the ability of VACV to replicate in RK13 cells was also analyzed to determine their individual contribution to viral replication and PKR activation. Since E3L and K3L are two relevant host range genes, we hypothesized that expression of one or both of them may have a positive impact on the ability of ECTV to replicate in RK13 cells. Using various methods to assess virus growth, we did not detect any significant differences with respect to the replication of ECTV between wild-type RK13 compared to versions of this cell line that stably expressed VACV E3 alone or in combination with K3. Therefore, there remain unanswered questions related to the factors that limit the host range of ECTV.
Highlights
Ectromelia virus (ECTV; referred to as “mousepox virus”) is a double-stranded DNA virus in the Poxviridae family
To better understand the discrepancy in replication capacity of these viruses, we examined the ability of ECTV to replicate in wild-type RK13 cells compared to cells that constitutively express E3 and K3 from Vaccinia virus (VACV)
The role these proteins play in the ability of VACV to replicate in RK13 cells was analyzed to determine their individual contribution to viral replication and protein kinase R (PKR) activation
Summary
Ectromelia virus (ECTV; referred to as “mousepox virus”) is a double-stranded DNA virus in the Poxviridae family. ECTV typically infects mice through abrasions in the skin [1]. Following initial replication at the site of infection, the virus disseminates to multiple organs over the course of several days [2]. Among the mice that survive the initial infection, characteristic pock lesions manifest on the skin [2,3] in a similar fashion to the disease manifestations of humans infected with variola virus (VARV), the causative agent of smallpox [4]. Vaccinia virus (VACV) is the best studied of all identified poxviruses and was used successfully in the global effort to eliminate circulating VARV. Replication of VACV is restricted to the site of infection after cutaneous inoculation of mice [10], which is quite dissimilar from the infection course of ECTV
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