Molecular Detection and Characterization of the First Cowpox Virus Isolate Derived from a Bank Vole

Abstract

Cowpox virus (CPXV) is a zoonotic orthopoxvirus (OPV) that infects a wide range of mammals. CPXV-specific DNA and antibodies were detected in different vole species, such as common voles (Microtus arvalis) and bank voles (Myodes glareolus). Therefore, voles are the putative main reservoir host of CPXV. However, CPXV was up to now only isolated from common voles. Here we report the detection and isolation of a bank vole-derived CPXV strain (GerMygEK 938/17) resulting from a large-scale screening of bank voles collected in Thuringia, Germany, during 2017 and 2018. Phylogenetic analysis using the complete viral genome sequence indicated a high similarity of the novel strain to CPXV clade 3 and to OPV “Abatino” but also to Ectromelia virus (ECTV) strains. Phenotypic characterization of CPXV GerMygEK 938/17 using inoculation of embryonated chicken eggs displayed hemorrhagic pock lesions on the chorioallantoic membrane that are typical for CPXV but not for ECTV. CPXV GerMygEK 938/17 replicated in vole-derived kidney cell lines but at lower level than on Vero76 cell line. In conclusion, the first bank vole-derived CPXV isolate provides new insights into the genetic variability of CPXV in the putative reservoir host and is a valuable tool for further studies about CPXV-host interaction and molecular evolution of OPV.

In Vivo Characterization of a Bank Vole-Derived Cowpox Virus Isolate in Natural Hosts and the Rat Model

“…Along with a previous study, we concluded that in vitro assays could not predict in vivo properties or virulence differences [39]. The same was observed in a recent study for the new CPXV strain GerMygEK 938/17 in comparison to Brighton Red and CPXV FM2292 on different cell lines (bank vole-and common vole-derived kidney cells and Vero76 cells) [32].…”

“…In 2018, we successfully isolated the first bank vole-derived CPXV strain, GerMygEK 938/17 [32]. This new isolate provided the possibility to test the susceptibility of bank voles by experimental infection with a bank vole-derived strain.…”

“…This has to be taken into consideration for the evaluation of the absence of any clinical signs. It can be also speculated that sequence variation of the two related CPXV-like 3 strains in previously identified relevant genes like vCCl, CrmB, CPXV0022, and CPXV194 are the reason of differences in virulence [32], and further studies will be necessary for clarification.…”

“…CPXV strain GerMygEK 938/17 was isolated from the nasal septum of a bank vole collected during the project "Population dynamics of rodent hosts of zoonotic disease: interaction of climate, landuse and biodiversity" on a forest plot in the federal state of Thuringia, Germany, in spring 2017 [32]. CPXV Ger2010MKY has been isolated from cutaneous lesions of cotton-top tamarins housed in a animal park in Thuringia, Germany and has been already characterized by experimental inoculation of Wistar rats before [10].…”

“…That changed in 2017 and 2018, when bank voles were trapped in Thuringia, Germany and 509 nasal septa were screened for OPV-DNA via quantitative PCR (qPCR) [32]. Five samples tested positive for OPV-DNA, and one bank vole-derived virus isolate (CPXV GerMygEK 938/17) could be obtained.…”