Submitted to: Journal of Virology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/24/2007
Publication Date: 7/26/2007
Citation: Jarosinski, K.W., Margulis, N.G., Kamil, J.P., Spatz, S.J., Nair, V.K., Osterrieder, N. 2007. Horizontal transmission of Marek’s disease virus requires US2, the UL13 protein kinase, and gC. Journal of Virology. Oct;81(19):10575-87. Interpretive Summary: Not required.
Technical Abstract: Marek’s disease virus (MDV), an Alphaherpesvirus, causes a general malaise in chickens that is mostly characterized by the development of lymphoblastoid tumors in multiple organs. The use of bacterial artificial chromosomes (BACs) for cloning and manipulation of the MDV genome has facilitated characterization of specific genes or regions. The development of most MDV BACs, including pRB 1B derived from a very virulent MDV strain, involved removing the US2 open reading frame that has been shown to be non-essential for virus replication. However, when recombinant viruses (rMDV) based on pRB-1B were used in pathogenicity studies, it was discovered that contact chickens housed with experimentally infected chickens did not contract Marek’s disease (MD), indicating a lack of horizontal transmission of pRB-1B-derived rMDV. Staining of feather follicle epithelial in the skins of infected chickens showed that virus was present, consistent with a recently published report, but was unable to be released and/or infect susceptible chickens. Restoration of US2 and removal of mini-F vector sequences within reconstituted MDV did not alter this characteristic, although in vivo viral replication was increased as evidenced by elevated viremia levels. Sequence analyses of pRB-1B revealed that the unique-long (UL) 13 (UL13) and UL44 genes encoding the UL13 serine/threonine protein kinase and glycoprotein (g) C, respectively, harbored mutations that caused frame-shift mutations. These mutations were repaired individually or in combination using two-step Red mutagenesis, and resulting viruses were tested for replication and their abilities to spread from infected to non-infected contact chickens. The experiments clearly showed that both UL13 and gC in combination are essential for horizontal transmission of MDV from chicken to chicken and that neither of the genes by itself was able to restore animal-to-animal spread.