Orf virus induces complete autophagy to promote viral replication via inhibition of AKT/mTOR and activation of the ERK1/2/mTOR signalling pathway in OFTu cells.

Orf virus (ORFV) is the causative agent of contagious ecthyma, which is an important zoonotic pathogen with a widespread distribution affecting sheep, goats and humans. Our previous research showed that autophagy can be induced in host cells by ORFV infection. However, the exact mechanism of ORFV-induced autophagy remains unknown. In this study, we investigated the underlying mechanisms of autophagy induced by ORFV in OFTu cells and the impact of autophagy on ORFV replication. By using specific autophagy inhibitors and activators, Western blotting, immunofluorescence and transmission electron microscopy imaging, we confirmed that ORFV infection triggered intracellular autophagosome accumulation and the activation of autophagic flux. Moreover, ORFV-induced autophagic activity was found to rely on an increase in the phosphorylation of tuberous sclerosis complex 2 (TSC2) and a decrease in the phosphorylation of mammalian target of rapamycin (mTOR), which is mediated by the suppression of the PI3K/AKT/mTOR signalling pathway and activation of the ERK1/2/mTOR signalling pathway. Furthermore, we investigated the role of mTOR-mediated autophagy during ORFV replication using pharmacological agents and demonstrated that ORFV-induced autophagy correlated positively with viral replication. Taken together, our data reveal the pathways of ORFV-induced autophagy and the impact of autophagy on ORFV replication, providing new insights into ORFV pathogenesis.

Complete genomic sequences and comparative analysis of two Orf virus isolates from Guizhou Province and Jilin Province, China.

Orf virus (ORFV, species Orf virus) belongs to the typical species of the Parapoxvirus genus of the family Poxviridae, which infects sheep, goats, and humans with worldwide distribution. Although outbreaks of Orf have been reported sequentially in several Chinese provinces, the epidemiology of Orf and genetic diversity of ORFV strains still needs to be further characterized. To further reveal the genomic organization of the ORFV-GZ18 and ORFV-CL18 isolates, the complete genome sequences of two recently obtained ORFV isolates were sequenced using the next-generation sequencing technology and analyzed, which had been deposited in the GenBank database under accession number MN648218 and MN648219, respectively. The complete genomic sequence of ORFV-CL18 was 138,495 bp in length, including 131 potential open reading frames (ORFs) flanked by inverted terminal repeats (ITRs) of 3481 bp at both ends, which has genomic structure typical Parapoxviruses. The overall genomic organization of the fully sequenced genome of ORFV-GZ18 was consistent with ORFV-CL18 genome, with a complete genome size of 138,446 nucleotides, containing 131 ORFs flanked by ITRs of 3469 bp. Additionally, the overall G + C contents of ORFV-GZ18 and ORFV-CL18 genome sequences were about 63.9% and 63.8%, respectively. The phylogenetic analysis showed that both ORFV-GZ18 and ORFV-CL18 were genetically closely related to ORFV-SY17 derived from sheep. In summary, the complete genomic sequences of ORFV-GZ18 and ORFV-CL18 are reported, with the hope it will be useful to investigate the host range, geographic distribution, and genetic evolution of the virus in Southern West and Northern East China.