Deletion of the Chemokine Binding Protein Gene from the Parapoxvirus Orf Virus Reduces Virulence and Pathogenesis in Sheep

Abstract

Orf virus (ORFV) is the type species of the Parapoxvirus genus of the family Poxviridae and infects sheep and goats, often around the mouth, resulting in acute pustular skin lesions. ORFV encodes several secreted immunomodulators including a broad-spectrum chemokine binding protein (CBP). Chemokines are a large family of secreted chemotactic proteins that activate and regulate inflammation induced leukocyte recruitment to sites of infection. In this study we investigated the role of CBP in vivo in the context of ORFV infection of sheep. The CBP gene was deleted from ORFV strain NZ7 and infections of sheep used to investigate the effect of CBP on pathogenesis. Animals were either infected with the wild type (wt) virus, CBP-knockout virus or revertant strains. Sheep were infected by scarification on the wool-less area of the hind legs at various doses of virus. The deletion of the CBP gene severely attenuated the virus, as only few papules formed when animals were infected with the CBP-knock-out virus at the highest dose (107 p.f.u). In contrast, large pustular lesions formed on almost all animals infected with the wt and revertant strains at 107 p.f.u. The lesions for the CBP-knock-out virus resolved approximately 5–6 days p.i, at a dose of 107 pfu whereas in animals infected with the wt and revertants at this dose, lesions began to resolve at approximately 10 days p.i. Few pustules developed at the lowest dose of 103 p.f.u. for all viruses. Immunohistochemistry of biopsy skin-tissue from pustules showed that the CBP-knockout virus replicated in all animals at the highest dose and was localized to the skin epithelium while haematoxylin and eosin staining showed histological features of the CBP-knockout virus typical of the parent virus with acanthosis, elongated rete ridges and orthokeratotic hyperkeratosis. MHC-II immunohistochemistry analysis for monocytes and dendritic cells showed greater staining within the papillary dermis of the CBP-knock-out virus compared with the revertant viruses, however this was not the case with the wt where staining was similar. Our results show that the CBP gene encodes a secreted immunodulator that has a critical role in virulence and pathogenesis.

Orf virus (ORFV) infection in a three-dimensional human skin model: Characteristic cellular alterations and interference with keratinocyte differentiation

“…In addition, at the restricted CPE sites in OTC, a thickening of the stratum corneum was detected at ORFV-infected areas, as described in sheep experimental skin infection [19]. ORFV induces proliferative skin lesions characterized amongst others by epidermal hyperplasia.…”

“…The infection of OTC generated from ovine foreskin primary lamb keratinocytes with ORFV resulted in ballooning degeneration of cells in the superficial layers [1]. In the natural host ORFV uses a number of virus-specific escape proteins, including interferon resistance factor, chemokine binding protein (CBP), IL-2, granulocyte/macrophage growth inhibitory factor (GIF) and viral IL-10 [13–19] to counteract the immune response. An exceptional and unique feature of ORFV is the expression of vascular endothelial growth factor E (VEGF-E) promoting angiogenesis [20,21].…”

Orf Virus: A New Class of Immunotherapy Drugs

“…ORFV-CBP and CBP-II have high affinity to some CC chemokines, such as monocyte chemoattractant protein 1 (MCP1), macrophage inflammatory protein 1 (MIP1), and regulated on activation, normal T cell expressed and secreted (RANTES), which can produce chemotactic effects of both nucleus/macrophage and T lymphocyte toward inflammation. Although ORFV encodes a number of secreted anti-inflammatory factors, the deletion of the CBP gene severely attenuated viral virulence and pathogenesis [22].…”

Orf virus: A promising new therapeutic agent

“…By combining with chemokines, CBP also inhibits DC aggregation and migration in peripheral lymph nodes. Although ORFV encodes a number of secreted anti‐inflammatory factors, the deletion of the CBP gene severely attenuated viral virulence and pathogenesis . The GIF of ORFV, similar to CBP, is unique to poxvirus and inhibits the migration of murine monocytes into the skin, preventing inflammatory response …”

“…Although ORFV encodes a number of secreted anti-inflammatory factors, the deletion of the CBP gene severely attenuated viral virulence and pathogenesis. 46 The GIF of ORFV, similar to CBP, is unique to poxvirus and inhibits the migration of murine monocytes into the skin, preventing inflammatory response. 47 The functional activity of the ORFV007 gene and the ORFV007encoded dUTPase has been characterized by Cottone et al 48 The virulence of ORFV with the 007-gene deletion is significantly lower than that of natural ORFV.…”