Identification of 10 cowpox virus proteins that are necessary for induction of 1 hemorrhagic lesions ( red pocks ) on chorioallantoic membranes 2

10 Cowpox viruses (CPXV) cause hemorrhagic lesions (“red pocks”) on infected 11 chorioallantoic membranes (CAM) of embryonated chicken eggs, while most other 12 members of the genus Orthopoxvirus produce non-hemorrhagic lesions (“white 13 pocks”). Cytokine response modifier A (CrmA) of CPXV strain Brighton Red (BR) is 14 necessary but not sufficient for the induction of red pocks. To identify additional viral 15 proteins involved in the induction of hemorrhagic lesions, a library of single gene 16 CPXV knockout mutants was screened. We identified 10 proteins that are required for 17 the formation of hemorrhagic lesions, which are encoded by CPXV060, CPXV064, 18 CPXV068, CPXV069, CPXV074, CPXV136, CPXV168, CPXV169, CPXV172 and 19 CPXV199. The genes are the homologs of F12L, F15L, E2L, E3L, E8R, A4L, A33R, 20 A34R, A36R and B5R of vaccinia virus (VACV). Mutants with deletions in CPXV060, 21 CPXV168, CPXV169, CPXV172 or CPXV199 induced white pocks with a comet-like 22 shape on the CAM. The homologues of these five genes in VACV encode proteins 23 that are involved in the production of extracellular enveloped viruses (EEV) and the 24 repulsion of superinfecting virions by actin tails. The homologue of CPXV068 in 25 VACV is also involved in EEV production but not related to actin tail induction. The 26 other genes encode immunomodulatory proteins (CPXV069 and crmA) and viral core 27 on July 9, 2017 by gest http/jvi.asm .rg/ D ow nladed fom