| Summary: | 碩士 === 國立中興大學 === 微生物暨公共衛生學研究所 === 103 === Orf virus (ORFV) infection causes pustule and ulceration around muzzle of small ruminants. Although it often occurs with low mobility and mortality, orf may be fatal in juvenile hosts. ORFV, belonging to genus parapoxvirus of the family Poxviridae, is an enveloped virus with double-stranded DNA genome. OV20.0 protein is produced from OV20.0L gene, an E3L ortholog, which is conserved in the genome of most members in Poxviridae. Vaccinia E3 (VV E3) has been studied extensively in these days; however sequences of VV E3 shares low identity with those of OV20.0. According to previous publication, OV20.0L could be translated into to two isoforms, full-length OV20.0 and N-terminal truncated one (sh20). Due to limited information of OV20.0 protein, our research focused on the translation mechanism of the isoform, comparative analysis of their cellular distribution and realizing their functions as well as their contribution to pathogenicity in mice model. First, we proved sh20 was translated from the third start codon of OV20.0L gene. In in vitro and in virus infection condition, both ORFV 20.0 and sh20 can hold the ability to bind double-stranded RNA (dsRNA), sequester the substrate of dsRNA-dependent protein kinase (PKR) that in turns inhibits the activity of downstream factor, eukaryotic initiation factor 2 (eIF2α), and influences cytokine releasing in different levels. Moreover, constructing recombinant virus and animal experiments clarify the role ORFV OV20.0 played in vivo. Although full-length OV20.0 and sh20 shared most functions in vitro, the ORFV recombinant virus which only expressed sh20, was attenuated in vivo. This data implied N-terminus of OV20.0 was required to induce intact pathogenicity in live animals.
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