ABSTRACT
The present study provides for the first time an extended investigation of individual genes located at the near-terminal right end of the genome of parapoxvirus bovis 1, Bovine papular stomatitis virus (BPSV) strain B177 and Orf virus (ORFV). Comparison of the respective DNA sequences of ORFV strain D1701 (9.9 kbp) and BPSV B177 (7.7 kbp) revealed a very similar organization of closely related genes transcribed in a rightward orientation. The most salient findings of this study were: (i) the absence of the ORFV-specific vascular endothelial growth factor (VEGF-E) gene in the BPSV isolate; (ii) the presence of an interleukin-10 (IL-10) orthologue; and (iii) the detection of three new genes encoding ankyrin-repeat-containing polypeptides. These results not only contribute to potential improvements of future molecular differentiation between the parapoxvirus species, but also shed new light on different pathobiologies among parapoxviruses.
Subject(s)
Genetic Variation , Genome, Viral , Orf virus/genetics , Parapoxvirus/genetics , Viral Proteins/genetics , Amino Acid Sequence , Animals , Cattle , Interleukin-10/chemistry , Interleukin-10/genetics , Interleukin-10/metabolism , Molecular Sequence Data , Sequence Analysis, DNA , Viral Proteins/chemistry , Viral Proteins/metabolismABSTRACT
Orf virus (OV) is an epitheliotropic poxvirus and belongs to the genus Parapoxvirus (PPV). PPV, especially OV, is regarded as a promising candidate for an expression vector. Among available live vaccines only strain D1701 represents a highly attenuated OV strain with clearly reduced pathogenicity. Therefore, we started to identify potentially non-essential genes or regions of D1701, which might be suitable for insertion and expression of foreign genes. The present contribution reviews some of the progress using the vegf-e (homologue of the mammalian vascular endothelial growth factor) gene locus for the generation of recombinant D1701. The vegf-e gene of D1701 is dispensable for virus growth in vitro and in vivo, and represents a major virulence determinant of OV. It is shown that foreign genes can be inserted and functionally expressed in the vegf-e locus, also leading to the induction of a specific immune response in the non-permissive host. Furthermore, it is reported that adaptation to VERO cells led to the deletion of three further regions of the OV D1701 genome, which seems to be combined with additional virus attenuation in sheep. Molecular analysis of this OV D1701 variant allows the identification of new, potentially non-essential sites in the viral genome.
