Orf virus (ORFV) ANK-1 protein mitochondrial localization is mediated by ankyrin repeat motifs

Unique ankyrin repeat proteins in the genome of poxviruses-Boon or Wane, a critical review

Ankyrin repeat is a 33-amino acid motif commonly observed in eukaryotes and, to a lesser extent, in prokaryotes and archaea and rarely in viruses. This motif plays a crucial role in regulating various cellular processes like the cell cycle, transcription, cell signaling, and inflammatory responses through interactions between proteins. Poxviruses exhibit a distinctive feature of containing multiple ankyrin repeat proteins within their genomes. All the genera of poxviruses possess these proteins except molluscipox virus, crocodylidpox virus, and red squirrel poxvirus. An intriguing characteristic has generated notable interest in studying the functions of these proteins within poxvirus biology. Within poxviruses, ankyrin repeat proteins exhibit a distinct configuration, featuring ankyrin repeats in the N-terminal region and a cellular F-box homolog in the C-terminal region, which enables interactions with the cellular Skp, Cullin, F-box containing ubiquitin ligase complex. Through the examination of experimental evidences and discussions from current literature, this review elucidates the organization and role of ankyrin repeat proteins in poxviruses. Various research studies have highlighted the significant importance of these proteins in poxviral pathogenesis and, acting as factors that enhance virulence. Consequently, they represent viable targets for developing genetically altered viruses with decreased virulence, thus displaying potential as candidates for vaccines and antiviral therapeutic development contributing to safer and more effective strategies against poxviral infections.

Efficient and scalable clarification of Orf virus from HEK suspension for vaccine development

The Orf virus (ORFV) is a promising vector platform for the generation of vaccines against infectious diseases and cancer, highlighted by its progression to clinical testing phases. One of the critical steps during GMP manufacturing is the clarification of crude harvest because of the enveloped nature and large size of ORFV. This study presents the first description of ORFV clarification process from a HEK suspension batch process. We examined various filter materials, membrane pore sizes, harvest timings, and nuclease treatments. Employing the Ambr® crossflow system for high-throughput, small-volume experiments, we identified polypropylene-based Sartopure® PP3 filters as ideal. These filters, used in two consecutive stages with reducing pore sizes, significantly enhanced ORFV recovery and addressed scalability challenges. Moreover, we demonstrated that the time of harvest and the use of a nuclease play a decisive role to increase ORFV yields. With these findings, we were able to establish an efficient and scalable clarification process of ORFV derived from a suspension production process, essential for advancing ORFV vaccine manufacturing.

Recombinant Orf virus induced antibody production against capsid protein of porcine circovirus type 3 in mice

The emerging worldwide distributed porcine circovirus type 3 (PCV3) infection poses a serious threat to swine herds. An important means of preventing and controlling PCV3 infection is the development of the vaccine, while, the inability to cultivate in vitro has become the biggest obstacle. Orf virus (ORFV), the prototypic member of the Parapoxviridae, has been proven to be a novel valid vaccine vector for preparing various candidate vaccines. Here, recombinant ORFV expressing capsid protein (Cap) of PCV3 was obtained and proved its favorable immunogenicity inducing antibody against Cap in BALB/c mice. Based on the enhanced green fluorescent protein (EGFP) as a selectable marker, the recombinant rORFVΔ132-PCV3Cap-EGFP was generated. Then, recombinant ORFV expressing Cap only, rORFVΔ132-PCV3Cap, was obtained based on rORFVΔ132-PCV3Cap-EGFP using a double homologous recombination method by screening single non-fluorescent virus plaque. Results of the western blot showed that the Cap can be detected in rORFVΔ132-PCV3Cap infected OFTu cells. The results of immune experiments in BALB/c mice indicated that a specific antibody against Cap of PCV3 in serum was induced by rORFVΔ132-PCV3Cap infection. The results presented here provide a candidate vaccine against PCV3 and a feasible technical platform for vaccine development based on ORFV.

The orf virus 129 protein can inhibit immune responses by interacting with host complement C1q binding protein in goat turbinate bone cells

OBJECTIVE

Contagious ecthyma is a severe and highly contagious disease caused by an orf virus (ORFV). The virus is responsible for substantial economic losses in the goat industry and threatens humans. We previously determined the role of ORFV129 protein, one of the five ankyrin-repeat proteins coded by the orf genome, in suppressing the transcription of pro-inflammatory cytokines IL-6, IL-1β and IFN-γ. In the present study, we identified 14 cellular proteins (complement C1q binding protein [C1QBP], MCM7, EIF5A, PKM, SLC6A, TSPAN6, ATP6AP2, GPS1, MMADHC, HSPB6, SLC35B1, MTF1, P3H4, and IL15RA) that interact with ORFV129 using a yeast two-hybrid system in goat turbinate bone cells (GFTCs). The interaction between ORFV129 and (C1QBP), an immune-related protein, was confirmed using immunofluorescence co-localization and co-immunoprecipitation assays. C1QBP overexpression inhibited ORFV replication, whereas the knockdown of C1QBP promoted ORFV replication in GFTCs. Furthermore, ORFV or ORFV129 increased C1QBP expression in GFTCs, indicated that ORFV129-C1QBP interaction might contribute to the ORFV-induced host immune process. In addition, our research showed that ORFV increased the expression of ORFV129, cytokine IL-6, IL-1β and IFN-γ. C1QBP overexpression induced IFN-γ production and reduced IL-6 and IL-1β production. Conversely, C1QBP knockdown induced IL-1β production and reduced IFN-γ and IL-1β production. Moreover, augmentation of ORFV129 expression enhanced the inhibition of the secretion of cytokines IL-6, IL-1β, and IFN-γ induced by the altered expression of C1QBP. These findings suggest different downstream pathways might be involved in regulating different cytokines induced by ORFV129 expression in GFTCs.

The OH system: A panorama view of the PPV-host interaction

Poxviruses are a family of specialized cytoplasm-parasitic DNA viruses that replicate and assembly in virus factory. In Parapoxvirus (PPV) genus, with the orf virus (ORFV) as a representative species of this genus, their behaviors are significantly different from that of Orthopoxvirus, and the plots of viral practical solutions for evading host immunity are intricate and fascinating, particularly to anti-host and host's antiviral mechanisms. In order to protect the virus factory from immune elimination caused by infection, PPVs attempt to interfere with multiple stress levels of host, mainly by modulating innate immunity response (IIR) and adaptive immunity response (AIR). Given that temporarily constructed by virus infection, ORFV-HOST (OH) system accompanied by viral strategies is carefully managed in the virus factory, thus directing many life-critical events once undergoing the IIR and AIR. Evolutionarily, to reduce the risk of system destruction, ORFV have evolved into a mild-looking mode to avoid overstimulation. Moreover, the current version of development also focus on recognizing and hijacking more than eight antiviral security mechanisms of host cells, such as the 2',5'-oligoadenylate synthetase (OAS)/RNase L and PKR systems, the ubiquitin protease system (UPS), and so on. In summary, this review assessed inescapable pathways as mentioned above, through which viruses compete with their hosts strategically. The OH system provides a panoramic view and a powerful platform for us to study the PPV-Host interaction, as well as the corresponding implications on a great application potential in anti-virus design.

Orf Virus Encoded Protein ORFV119 Induces Cell Apoptosis Through the Extrinsic and Intrinsic Pathways

Apoptosis, a significant form of cell death, has a leading role in the host cell defense against virus infection. Viruses have evolved a series of strategies that block apoptosis during the early stage of viral infection to enhance viral replication, and induce apoptosis in the late stages to facilitate viral particle release from the cells. Here we show that orf virus (ORFV), the causative agent of orf, encodes an apoptosis-inducing protein ORFV119. ORFV119 targets the mitochondria in host cells, inhibits cell proliferation, and induces cell apoptosis. Protein array data indicated that ORFV119 could induce apoptosis via up-regulation of Smac, Bak, and Bax and down-regulation of anti-apoptotic proteins Bcl-2 and cIAP-2. Activation of caspase-9 and caspase-3, and consequent PARP cleavage, ultimately lead to apoptosis. ORFV119 could also directly activate caspase-8 and induce Bid, involved in the extrinsic pathway, to achieve cell death. Furthermore, sequence analysis and experiments with mutants of ORFV119 introduced revealed that ORFV119 contains a key N-terminal domain that is necessary and sufficient to direct the protein to the mitochondria. Together, we report, for the first time, the identification of the novel apoptosis-inducing protein ORFV119 encoded by a parapoxvirus. This provides an important reference for the study of pathogenesis, identification of immunomodulation mechanisms of ORFV, and may lead to new strategies for orf disease control.

Poxviral ankyrin proteins

Multiple repeats of the ankyrin motif (ANK) are ubiquitous throughout the kingdoms of life but are absent from most viruses. The main exception to this is the poxvirus family, and specifically the chordopoxviruses, with ANK repeat proteins present in all but three species from separate genera. The poxviral ANK repeat proteins belong to distinct orthologue groups spread over different species, and align well with the phylogeny of their genera. This distribution throughout the chordopoxviruses indicates these proteins were present in an ancestral vertebrate poxvirus, and have since undergone numerous duplication events. Most poxviral ANK repeat proteins contain an unusual topology of multiple ANK motifs starting at the N-terminus with a C-terminal poxviral homologue of the cellular F-box enabling interaction with the cellular SCF ubiquitin ligase complex. The subtle variations between ANK repeat proteins of individual poxviruses suggest an array of different substrates may be bound by these protein-protein interaction domains and, via the F-box, potentially directed to cellular ubiquitination pathways and possible degradation. Known interaction partners of several of these proteins indicate that the NF-κB coordinated anti-viral response is a key target, whilst some poxviral ANK repeat domains also have an F-box independent affect on viral host-range.