Orf virus infection and host immunity

Retrospective research: identifying and conducting phylogenetic analyses on four Orf virus strains isolated in Yunnan province between 2021 and 2023-revealing their significance and characteristic features

Contagious Eczema (CE), caused by ORFV, impacts sheep and goats globally, with severe symptoms and economic losses. The ORFV situation in Yunnan, China, was unclear before 2021-2023 study. Eleven scab samples from goats on small farms in three Yunnan municipalities were collected. Four ORFV strains were isolated and characterized using scanning electron microscopy, cytopathic effect observation, and PCR. Phylogenetic analyses of ORFV011 and ORFV059 genes showed significant results. For ORFV011, the nucleotide similarity of the four strains to D1701 strain was 98.4-99%. For ORFV059, it was 97.2-97.9% with OV-SA00 strain. These findings suggest gene rearrangements and interactions among strains during Yunnan's ORFV outbreak, forming a unique evolutionary lineage. Our study is the first comprehensive one on Yunnan's ORFV prevalence with in-depth phylogenetic analysis. It has important implications. In vaccine development, understanding genetic variances helps create better vaccines. For disease control, customized strategies like targeted quarantine and disinfection can be designed based on strain characteristics. From a public health aspect, as CE is zoonotic, closely monitoring ORFV in goats aids in predicting and preventing human infections, thus being significant for protecting goats against CE in Yunnan.

Preparation and characterization of a mouse polyclonal antibody against the truncated ORFV113 recombinant protein of Orf virus

Orf is a contagious zoonotic disease caused by Orf virus (ORFV), posing a threat to both animal and human health. The ORFV113 gene, located in the terminal variable region of the ORFV genome, has been demonstrated as a significant virulence gene, but its function remains largely unknown. In the study, we first amplified the truncated version of the ORFV113 gene (ORFV113t) by removing its transmembrane domain at the 5' end. We then constructed the pET-32a-ORFV113t recombinant plasmid and expressed the truncated ORFV113 recombinant protein in Escherichia coli (E.coli). The purified ORFV113t fusion protein was used to immunize mice and generate a polyclonal antibody. This polyclonal antibody was subsequently used to detect the expression and subcellular localization of the ORFV113 protein. Additionally, virus neutralization test was utilized to determine the neutralizing titer of the polyclonal antibody. The results demonstrated that we successfully expressed the ORFV113t recombinant protein in a prokaryotic expression system and generated a mouse-derived polyclonal antibody targeting the ORFV113t recombinant protein with a titer of 1:204,800. This antibody exhibited specificity for detecting the ORFV113 protein expressed in both prokaryotic and eukaryotic cells. The ORFV113 protein was found to be localized in the cytoplasm of infected Lamb testis (LT) cells. Notably, the polyclonal antibody demonstrated neutralizing activity against ORFV in vitro, with a neutralizing titer of 1:32. The prepared mouse anti-ORFV113t protein polyclonal antibody can be utilized for further study on potential functions of the ORFV113 protein in viral pathogenesis.

Pathogenicity and phylogenetic analysis of ovine contagious ecthyma virus isolated during a sheeppox outbreak in Morocco

Contagious ecthyma (CE), also known as ORF is a highly contagious zoonotic viral skin disease that affects humans, sheep, goats and other domesticated and wild animals. As reported here-in, the objective of this study was to investigate a suspected outbreak of both sheeppox and ORF diseases in a sheep herd during the winter of 2020 in Northwest Morocco. The affected sheep showed nodules and proliferative scabby skin lesions around the mouth and hairless area of the body. Samples of skin crust were collected for virus identification and isolation. A virus was isolated in Vero cells, lamb testis and heart cells and the cytopathic effect was characterized by cells aggregation, ballooning, and detachment. Initially, the suspensions of skin crust were positive for sheeppox virus (SPPV) by PCR. Subsequent testing of the isolated virus from skin crust of affected animals indicated that the virus was SPPV-negative and ORFV-positive by PCR. Furthermore, nucleotide sequences of the B2L aligned with reference ORFV isolates for genetic analysis. Phylogenetic analyses results confirmed that the isolated virus was ORFV and that the virus was closely related to ORFV strains isolated in Sudan and Malaysia. In conclusion, this study is the first reported detection of ORFV in Morocco, and therefore, poses as an imminent threat to the health of humans, domestic and wild animals.

Outbreak of Contagious Ecthyma in Free-Ranging Iberian Ibex (Capra pyrenaica) in the Montgrí Massif Natural Park, Catalonia, Northeastern Spain

Contagious ecthyma is a common, worldwide, and highly transmissible viral zoonotic skin disease caused by the orf virus (ORFV). It mainly affects farmed small ruminants, but it has also been described in a broad range of wild and domestic mammals, with Caprinae species most susceptible. Between November 2019 and January 2020, adults, juveniles, yearlings, and kids from an Iberian ibex (Capra pyrenaica) population established in the Montgrí Massif Natural Park (Catalonia, northeastern Spain) were observed with clinical signs and lesions compatible with ORFV infection. The carcass of an adult male with severe disease enabled sample collection for histopathology and molecular studies, confirming ORFV DNA in the skin lesions. Sequence analyses indicated that the ORFV strain detected had high homology (>98%) with strains previously obtained from other European wild ruminant species. The outbreak peaked in December 2019, with an estimated prevalence of 68.97% (95% confidence interval, 53.35-84.59). From February 2020 forward, no individuals with lesions were observed. The yearly counts for population monitoring corroborated the apparently negligible ORFV impact on the ibex population of the Montgrí Natural Park. There are no previous reports of contagious ecthyma in a free-ranging Iberian ibex population.

The cooperation between orf virus and Staphylococcus aureus leads to intractable lesions in skin infection

A large amount of evidence shows that different kinds of microorganisms can jointly cope with environmental pressures including cell hosts. For example, in many cases, it has been found that secondary or mixed infection of animals caused by ORFV (an epitheliophilic Parapoxvirus) and bacteria (such as Staphylococcus aureus or Streptococcus) shows a mutual aid mode that indirectly leads to the deterioration of the disease. However, the lack of research on the co-pathogenic mechanism, including how to hijack and destroy the cell host in the pathological microenvironment, has hindered the in-depth understanding of the pathogenic process and consequences of this complex infection and the development of clinical treatment methods. Here, we summarized the current strategies of trapping cell hosts together, based on the previously defined ORFV-Host (O-H) system. The opportunistic invasion of S. aureus destroyed the delicate dynamic balance of the O-H, thus aggravating tissue damage through bacterial products (mediated by Agr), even causing sepsis or inducing cytokine storms. In fact, the virus products from its adaptive regulatory system (VARS) weaken the immune attacks and block molecular pathways, so that S. aureus can settle there more smoothly, and the toxins can penetrate into local tissues more quickly. This paper focuses on the main challenges faced by cell hosts in dealing with mixed infection, which provides a starting point for us to deal with this disease in the future.

Next-generation sequencing approach to investigate genome variability of Parapoxvirus in Canadian muskoxen (Ovibos moschatus)

In 2016, the first orf virus, a double-stranded DNA (dsDNA) virus of the genus parapoxvirus, from a muskox was isolated on Victoria Island, Nunavut (NU), Canada. We used deep sequencing on DNA extracted from orf virus-positive tissues from wild muskoxen from locations on Victoria Island and the adjacent mainland. Orf virus sequence reads derived from four samples were nearly identical. The consensus sequences generated from pooled reads of MxOV comprises of a large contiguous sequence (contig) of 131,759 bp and a smaller right terminal contig of 3552 bp, containing all coding sequences identified as Parapoxvirus. Individual gene comparisons reveal that MxOV shares genetic characteristics with reference strains from both sheep and goat origin. Recombination analysis using Bootscan, MAXCHI, GENECONV, CHIMAERA, SISCAN, and RDP algorithms within the RDP4 software predicted recombination events in two virulence factors, and a large 3000 bp segment of the MxOV genome. Partial B2L nucleotide sequences from strains around the world and other North American isolates were compared to MxOV using MUSCLE alignments and RAxML phylogenetic trees. MxOV was identical to our previously characterized isolate, and shared similarity with orf virus isolated from sheep and goats. The phylogenetic grouping of partial B2L nucleotide sequences did not follow the sample geographic distribution. More full genomes of orf virus, or at least full B2L gene squences, in wildlife are needed especially in North America to better understand the epidemiology of the disease in muskoxen.

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.

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.

Detection of contagious ovine ecthyma (orf) and risk factors for infection in small ruminants in Iran

The primary cause of contagious ecthyma is the orf virus, the parapoxvirus prototype. It is a viral problem observed in goat and sheep flocks in Iran, causing economic loss. Orf is a zoonosis with little epidemiological investigation present in Iran. The current research aims at determining the status of this virus, and a PCR was used as a confirmatory instrument. We sampled 668 goats and sheep and various breeding systems. Besides, the orf prevalence was studied, and vaccination efficacy was determined. Moreover, the potential risk factors surveyed for infection with ecthyma were identified. Samples were taken from goat and sheep flocks in the present cross-sectional research, and PCR was used for testing orf DNA. A checklist including animals' general information was completed. Data were analyzed using univariate tests (chi-square and t-tests) and multivariable binary logistic regression analysis. Three hundred one (45%) goats and sheep detected orf DNA. The age of 70% of positive cases was below one month. Ecthyma infection was significantly higher in imported breeds (87.3%) than indigenous (39.3%). Ninety-six percent of infected goats and sheep in the present work were not vaccinated against ecthyma. The high prevalence of the orf virus was confirmed among goat and sheep flocks in Iran. It is necessary to train ranchers regarding sanitary actions, quarantine, and application of orf vaccination plans.

The novel ORFV protein ORFV113 activates LPA-p38 signaling

Viruses have evolved mechanisms to subvert critical cellular signaling pathways that regulate a wide range of cellular functions, including cell differentiation, proliferation and chemotaxis, and innate immune responses. Here, we describe a novel ORFV protein, ORFV113, that interacts with the G protein-coupled receptor Lysophosphatidic acid receptor 1 (LPA1). Consistent with its interaction with LPA1, ORFV113 enhances p38 kinase phosphorylation in ORFV infected cells in vitro and in vivo, and in cells transiently expressing ORFV113 or treated with soluble ORFV113. Infection of cells with virus lacking ORFV113 (OV-IA82Δ113) significantly decreased p38 phosphorylation and viral plaque size. Infection of cells with ORFV in the presence of a p38 kinase inhibitor markedly diminished ORFV replication, highlighting importance of p38 signaling during ORFV infection. ORFV113 enhancement of p38 activation was prevented in cells in which LPA1 expression was knocked down and in cells treated with LPA1 inhibitor. Infection of sheep with OV-IA82Δ113 led to a strikingly attenuated disease phenotype, indicating that ORFV113 is a major virulence determinant in the natural host. Notably, ORFV113 represents the first viral protein that modulates p38 signaling via interaction with LPA1 receptor.

A Review on Human Orf: A Neglected Viral Zoonosis

Orf virus (ORFV) is the etiologic agent of Orf or ecthyma contagiosum in humans but primarily affects different domestic and wild animals. The disease mostly affects sheep, goats and other small wild ruminants and spreads to humans through direct contact with infected animals or by way of contaminated fomites worldwide. ORFV is taxonomically classified as a member of the genus Parapoxvirus. It is known to have tolerance to inactivation in a drier environment, and it has been recovered from crusts after several months to years. Among immunocompetent people, the lesions usually resolve by its natural course within a maximum of 8 weeks. In immunosuppressed patients, however, it needs the use of various approaches including antiviral, immune modifier or minor surgical excisions. The virus through its association with divergent host ranges helps to develop a mechanism to evade the immune system. The relative emergence of Orf, diagnosed on clinical ground among human cases, in unusual frequencies in southwest Ethiopia between October 2019 and May 2020, was the driver to write this review. The objective was to increase health care providers' diagnostic curiosity and to bring the attentiveness of public health advisors for prevention, control and the development of schemes for surveillance of Orf zoonosis in a similar setting like Ethiopia.

Screening of Eurasian Tundra Reindeer for Viral Sequences by Next-Generation Sequencing

Reindeer husbandry is essential for the livelihood and culture of indigenous people in the Arctic. Parts of the herding areas are also used as pastures for farm animals, facilitating potential transmission of viruses between species. Following the Covid-19 pandemic, viruses circulating in the wild are receiving increased attention, since they might pose a potential threat to human health. Climate change will influence the prevalence of infectious diseases of both humans and animals. The aim of this study was to detect known and previously unknown viruses in Eurasian tundra reindeer. In total, 623 nasal and 477 rectal swab samples were collected from reindeer herds in Fennoscandia, Iceland, and Eastern Russia during 2016–2019. Next-generation sequencing analysis and BLAST-homology searches indicated the presence of viruses of domesticated and wild animals, such as bovine viral diarrhea virus, bovine papillomavirus, alcephaline herpesvirus 1 and 2, deer mastadenovirus B, bovine rotavirus, and roe deer picobirnavirus. Several viral species previously found in reindeer and some novel species were detected, although the clinical relevance of these viruses in reindeer is largely unknown. These results indicate that it should be possible to find emerging viruses of relevance for both human and animal health using reindeer as a sentinel species.

Orf virus ORFV112, ORFV117 and ORFV127 contribute to ORFV IA82 virulence in sheep

The parapoxvirus orf virus (ORFV) encodes several immunomodulatory proteins (IMPs) that modulate host innate and pro-inflammatory responses to infection. Using the ORFV IA82 strain as the parental virus, recombinant viruses with individual deletions in the genes encoding the IMPs chemokine binding protein (CBP; ORFV112), inhibitor of granulocyte-monocyte colony-stimulating factor and IL-2 (GIF, ORFV117) and interleukin 10 homologue (vIL-10; ORFV127) were generated and characterized in vitro and in vivo. The replication properties of the individual gene deletion viruses in cell culture was not affected comparing with the parental virus. To investigate the effect of the individual gene deletions in ORFV infection and pathogenesis, groups of four lambs were inoculated with each virus and were monitored thereafter. Lambs inoculated with either recombinant or with the parental ORFV developed characteristic lesions of contagious ecthyma. The onset, nature and severity of the lesions in the oral commissure were similar in all inoculated groups from the onset (3 days post-inoculation [pi]) to the peak of clinical lesions (days 11-13 pi). Nonetheless, from days 11-13 pi onwards, the oral lesions in lambs inoculated with the recombinant viruses regressed faster than the lesions produced by the parental virus. Similarly, the amount of virus shed in the lesions were equivalent among lambs of all groups up to day 15 pi, yet they were significantly higher in the parental virus group from day 16-21 pi. In conclusion, individual deletion of these IMP genes from the ORFV genome resulted in slight reduction in virulence in vivo, as evidenced by a reduction in the duration of the clinical disease and virus shedding.

Orf Virus-Based Vaccine Vector D1701-V Induces Strong CD8+ T Cell Response against the Transgene but Not against ORFV-Derived Epitopes

The potency of viral vector-based vaccines depends on their ability to induce strong transgene-specific immune response without triggering anti-vector immunity. Previously, Orf virus (ORFV, Parapoxvirus) strain D1701-V was reported as a novel vector mediating protection against viral infections. The short-lived ORFV-specific immune response and the absence of virus neutralizing antibodies enables repeated immunizations and enhancement of humoral immune responses against the inserted antigens. However, only limited information exists about the D1701-V induced cellular immunity. In this study we employed major histocompatibility complex (MHC) ligandomics and immunogenicity analysis to identify ORFV-specific epitopes. Using liquid chromatography-tandem mass spectrometry we detected 36 ORFV-derived MHC I peptides, originating from various proteins. Stimulated splenocytes from ORFV-immunized mice did not exhibit specific CD8+ T cell responses against the tested peptides. In contrast, immunization with ovalbumin-expressing ORFV recombinant elicited strong SIINFEKL-specific CD8+ T lymphocyte response. In conclusion, our data indicate that cellular immunity to the ORFV vector is negligible, while strong CD8+ T cell response is induced against the inserted transgene. These results further emphasize the ORFV strain D1701-V as an attractive vector for vaccine development. Moreover, the presented experiments describe prerequisites for the selection of T cell epitopes exploitable for generation of ORFV-based vaccines by reverse genetics.

Development and applications of a monoclonal antibody against caprine interferon-gamma

Background

Interferon-gamma (IFN-γ) is an important mediator of type I immune response and has antiviral, immunoregulatory and anti-tumor properties, plays a wide range of roles in inflammation and autoimmune diseases. The aim of this study was to obtain monoclonal antibody (mAb) against caprine IFN-γ by immunizing of BALB/c mice with the purified rIFN-γ.

Results

Recombinant caprine IFN-γ was expressed in Escherichia coli strain BL21 (DE3) and monoclonal antibodies against caprine IFN-γ were produced by immunizing of BALB/c mice with rIFN-γ. One hybridoma secreting mAb was screened by enzyme-linked immunosorbent assay (ELISA) which was designated as 2C. MAb secreted by this cell line were analyzed through ELISA, western blot and application of the mAb was evaluated by immunofluorescence analysis using goat lip tissues infected with Orf virus. ELISA analysis revealed that mAb 2C can specifically recognize rIFN-γ protein and culture supernatant of goat peripheral blood mononuclear cells (PBMCs) stimulated by concanavalin A (Con A) but cannot recognize the fusion tag protein of pET-32a. Western blot analysis showed that mAb 2C can specifically react with the purified 34.9 kDa rIFN-γ protein but does not react with the fusion tag protein of pET-32a. Immunofluorescence results demonstrated that mAb 2C can detect IFN-γ secreted in histopathological sites of goats infected with Orf virus.

Conclusions

A caprine IFN-γ-specific mAb was successfully developed in this study. Further analyses showed that the mAb can be used to detect IFN-γ expression level during contagious ecthyma in goats.

Establishment and characterization of transformed goat primary cells by expression of simian virus 40 large T antigen for orf virus propagations

Due to the limited host range of orf virus (ORFV), primary cells derived from its natural hosts, such as goats and sheep, are recommended for isolation and propagation of wild type ORFV. This situation limits the option for the study of virus-host interaction during ORFV infection since primary cells only support a few numbers of passages. SV40 T antigen is a viral oncoprotein that can abrogate replicative senescence, leading to an extended life span of cells. In this study, the transformation of two goat primary cells, fibroblast (FB) and testis (GT) cells, were achieved by stably expressing SV40 T antigen using the lentiviral technique. The presence of the gene encoding SV40 T antigen was validated by polymerase chain reaction (PCR) and western blot analyses. As evidenced by immunofluorescent microscopy, the two types of cells expressing SV40 T antigen (namely, FBT and GTT) were purified to homogeneity. Moreover, faster growth kinetics and a lower serum dependency were noticed in FBT and GTT, as compared with their counterpart parental cells. FBT and GTT remain permissive and can form plaque of ORFV, despite with different profiles; generally speaking, with SV40 T expression, ORFV forms plaques with smaller size and distinct margin. Most importantly, the prolonged life span of goat FBT and GTT serves as an ideal cell culture resource for ORFV isolation from the field, studies of ORFV pathogenesis and efficient vaccine development.

Identification of strain diversity and phylogenetic analysis based on two major essential proteins of Orf viruses isolated from several clinical cases reported in Malaysia

There is a little information on the characterization of Orf virus strains that are endemic in Malaysia. The relationship between the severity of disease and the molecular genetic profile of Orf virus strains has not been fully elucidated. This study documented the first confirmed report of contagious ecthyma causing by Orf virus in goats from a selected state of eastern peninsular Malaysia. The disease causes significant debilitation due to the inability of affected animals to suckle which brings a great economic loss to the farmers. A total of 504 animals were examined individually to recognize the affected animals with Orf lesion. Skin scrapping was used to collect the scab material from the infected animals. The presence of Orf virus was confirmed by combination of methods including virus isolation on vero cells, identification by Transmission Electron Microscopy (TEM) and molecular technique using PCR and Sanger sequencing. The results showed the successful isolation of four Orf virus strains with a typical cytopathic effects on the cultured vero cells line. The morphology was confirmed to be Orf virus with a distinctive ovoid and criss cross structure. The phylogenetic analysis revealed that these isolated strains were closely related to each other and to other previously isolated Malaysian orf viruses. In addition these Orf virus strains were closely related to Orf viruses from China and India. This study provides more valuable insight in terms of genotype of Orf virus circulating in Malaysia.

An association of Orf virus infection among sheep and goats with herd health programme in Terengganu state, eastern region of the peninsular Malaysia

BACKGROUND

Orf virus causes a scabby skin lesions which decreases productivity in small ruminants. The unknown status of this disease in the eastern region of Peninsular Malaysia warrants a study to determine sero-prevalence of orf with regards to farmers' compliance level towards the Herd Health Program (HHP) programme.

RESULTS

Out of 504 animals, 115 were positive for Orf-virus antibodies. An overall prevalence rate of 22.8% indicated a high prevalence of orf disease in this region. It was observed that 25.1% (92/367) of goats were positive and 16.8% (23/137) of sheep sero-converted for Orf virus antibody. Several factors were measured for their possible association with prevalence of Orf virus infection. The prevalence was higher in LY farm, JC breed, kid and female animals, and in the presence of disease lesion. Chi-square analysis showed a significant association of three risk factors which are species, age and sex of the animals (P < 0.05). Notwithstanding, all other variables showed no significant difference (P > 0.05). Farms surveyed usually practised intensive management system, keeping animals in the shade at all time, due to limited availability of suitable land as a free-range grazing area. An interview with small holder farmers revealed a lack of awareness of the main goals of herd health programme. An overall compliance level of 42.7% was observed for all HHP parameters. Among the 14 main components of HHP modules, animal identification had recorded highest compliance level (84.62%) while milking management recorded the least compliance (- 82.69%). That explained why there was a high sporadic prevalence of Orf infection in this region.

CONCLUSION

Good herd health supervision is a rehearsal target to prevent an outbreak and the spread of diseases thus reduces economic losses among farmers. Therefore, a good herd health programme should be in place, in order to prevent and control disease transmission as well as to improve herd immunity.

Outbreak of contagious ecthyma caused by Orf virus (Parapoxvirus ovis) in a vaccinated sheep flock in Uruguay

Orf virus (ORFV) causes contagious ecthyma (CE), a highly transmissible, zoonotic disease of small ruminants. CE most commonly affects lambs and unvaccinated sheep. This work reports epidemiologic, clinicopathologic, and virologic findings in a CE outbreak in a vaccinated sheep flock in Uruguay and failure to detect ORFV in a commercial vaccine.

Transcriptome analysis of sheep oral mucosa response to Orf virus infection

Contagious ecthyma is a highly contagious disease with worldwide distribution, which is caused by the Orf virus (ORFV) belonging to the Parapoxvirus. To study the alteration of host gene expression in response to ORFV infection at the transcriptional level, several young small-tailed Han sheep were inoculated with ORFV, and their oral mucosa tissue samples (T0, T3, T7 and T15) were collected on day 0, 3, 7 and 15 after ORFV infection respectively. RNA-seq transcriptome comparisons were performed, showing that 1928, 3219 and 2646 differentially expressed genes (DEGs) were identified among T3 vs. T0, T7 vs. T0, and T15 vs. T0 respectively. Gene Ontology (GO) analyses of the DEGs from these comparisons, revealed that ORFV might provoke vigorous immune response of the host cells during the early stage of infection. Moreover, GO and network analysis showed that positive and negative regulative mechanisms of apoptosis were integrated in the host cells through up or down-regulating the expression level of DEGs involved in apoptotic pathways, in order to reach a homeostasis of oral mucosa tissues during the exposure to ORFV infection. In conclusion, our study for the first time describes the direct effects of ORFV on the global host gene expression of its host using high-throughput RNA sequencing, which provides a resource for future characterizing the interaction mechanism between the mammalian host and ORFV.

A parapoxviral virion protein inhibits NF-κB signaling early in infection

Poxviruses have evolved unique proteins and mechanisms to counteract the nuclear factor κB (NF-κB) signaling pathway, which is an essential regulatory pathway of host innate immune responses. Here, we describe a NF-κB inhibitory virion protein of orf virus (ORFV), ORFV073, which functions very early in infected cells. Infection with ORFV073 gene deletion virus (OV-IA82Δ073) led to increased accumulation of NF-κB essential modulator (NEMO), marked phosphorylation of IκB kinase (IKK) subunits IKKα and IKKβ, IκBα and NF-κB subunit p65 (NF-κB-p65), and to early nuclear translocation of NF-κB-p65 in virus-infected cells (≤ 30 min post infection). Expression of ORFV073 alone was sufficient to inhibit TNFα induced activation of the NF-κB signaling in uninfected cells. Consistent with observed inhibition of IKK complex activation, ORFV073 interacted with the regulatory subunit of the IKK complex NEMO. Infection of sheep with OV-IA82Δ073 led to virus attenuation, indicating that ORFV073 is a virulence determinant in the natural host. Notably, ORFV073 represents the first poxviral virion-associated NF-κB inhibitor described, highlighting the significance of viral inhibition of NF-κB signaling very early in infection.

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

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.

Associação da ocorrência do ectima contagioso (ORF vírus) em ovinos com os cuidadores desses animais

RESUMO A enfermidade ectima contagioso está difundida em todo o estado de São Paulo. Foram amostrados 42 (8,64%) cuidadores de animais e 444 (91,36%) ovinos (n=486). A prevalência de reagentes para vírus-neutralização foi de 67% (IC95%=62-71%) nos ovinos, e em seus cuidadores de 76% (IC95%=63-89%), sendo P=0,22, ou seja, não houve diferença estatística significativa entre as espécies. A distribuição dos títulos teve diferença estatística significativa entre as espécies, com P=0,0048. As variações de titulação foram de 0,6 a 2,1 tanto nos ovinos quanto nos seus cuidadores. Dentre os 42 cuidadores de ovinos participantes do estudo, 32 apresentaram títulos de anticorpos expressos por log10 acima de 0,6.

Parapoxvirus orf virus infection induces an increase in interleukin-8, tumour necrosis factor-α, and decorin in goat skin fibroblast cells

Introduction: Orf virus (ORFV) is a prototype Parapoxvirus species in the Poxviridae family that causes serious zoonotic infectious disease. Goat skin fibroblast (GSF) cells are the major host targets of ORFV. Interleukin 8 (IL-8) and tumour necrosis factor (TNF)-α are known to play a vital role in immune response during viral infections. However, the manner of variation over time of their level of expression in GSF cells remains unclear.

Material and Methods: In this study, quantitative enzyme-linked immunosorbent assay chips were used to detect changes in the levels of these cytokines expressed and secreted in GSF cells after ORFV infection.

Results: Results showed that the expression of IL-8, TNF-α, and decorin was upregulated in the cell lysates, and that secreted decorin and IL-8 were significantly increased in cell supernatant.

Conclusion: The results provided possible approaches to elucidation of how ORFV infection initiates host cell immune response.

Orf Virus 002 Protein Targets Ovine Protein S100A4 and Inhibits NF-κB Signaling

Orf virus (ORFV), a member of Parapoxvirus, has evolved various strategies to modulate the immune responses of host cells. The ORFV-encoded protein ORFV002, a regulator factor, has been found to inhibit the acetylation of NF-κB-p65 by blocking phosphorylation of NF-κB-p65 at Ser²⁷⁶ and also to disrupt the binding of NF-κB-p65 and p300. To explore the mechanism by which ORFV002 regulates NF-κB signaling, the understanding of ORFV002 potential binding partners in host cells is critical. In this study, ovine S100 calcium binding protein A4 (S100A4), prolyl endopeptidase-like (PREPL) and NADH dehydrogenase (ubiquinone) 1 alpha subcomplex 8 (NDUFA8) were found to interact with ORFV002 based on the yeast two-hybrid (Y2H) assay using a cDNA library derived from primary ovine fetal turbinate cells (OFTu). GST pull-down and bidirectional co-immunoprecipitation assay results demonstrate that ORFV002 interacts with S100A4 directly. Following the pEGFP-ORFV002 (p002GFP) transfection, we found that cytoplasmic S100A4 translocates into the nucleus and co-localizes with ORFV002. Furthermore, the inhibitory effect of ORFV002 on NF-κB signaling was significantly restored by S100A4 knock-down phenotype, suggesting that ovine S100A4 participates in the ORFV002-mediated NF-κB signaling. These data demonstrate that ORFV002 inhibits the NF-κB activation through its interaction with S100A4 along with its nucleus translocation.

Development of a fluorescent probe-based recombinase polymerase amplification assay for rapid detection of Orf virus

Background

Orf virus (ORFV) is the causative agent of Orf (also known as contagious ecthyma or contagious papular dermatitis), a severe infectious skin disease in goats, sheep and other ruminants. The rapid detection of ORFV is of great importance in disease control and highly needed. A isothermal molecular diagnostic approach, termed recombinase polymerase amplification (RPA), is considered as an novel and rapid alternative techonology to PCR assay.

Results

In the present study, a novel fluorescent probe based on RPA assay (ORFV exo RPA assay) was developed. The developed ORFV exo RPA assay was capable of as low as 100 copies of ORFV DNA /reaction and was highly specific, with no cross-reaction with closely related viruses (capripox virus, foot-and-mouth disease virus or peste des petits ruminants virus). Further assessment with clinical samples showed that the developed ORFV exo RPA assay has good correlation with qPCR assays for detection of ORFV.

Conclusions

These results suggest that the developed ORFV exo RPA assay is suitable for rapid detection of ORFV.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-015-0440-z) contains supplementary material, which is available to authorized users.

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.

Orf Infection in a Patient with Stat1 Gain-of-Function

PURPOSE

Chronic Mucocutaneous Candidiasis (CMC) refers to a group of immunodeficiencies, characterized by persistent or recurrent infections of the skin, nails, and mucosae caused by Candida. It is typically caused by inborn errors of IL-17 immunity. Orf, also known as contagious ecthyma, is a zoonotic infection caused by a dermatotropic parapoxvirus that commonly infects sheep and goats; it is transmitted to humans through contact with an infected animal or fomites. While orf is usually a benign self-limiting illness, it can be progressive and even life-threatening in immune-compromised hosts.

METHODS AND RESULTS

A 34-year-old man with autosomal dominant CMC due to a heterozygous STAT1 gain-of-function (GOF) mutation cut his hand with a knife during slaughter. Giant orf infection developed in 2 weeks. He was successfully treated by cidofovir injections every other week for 4 months.

CONCLUSIONS

This is the first patient with severe orf in the context of a well-defined genetically identified PID: CMC and inborn error of IL-17 immunity due to a GOF STAT1 mutation.

Pathogenesis in lambs and sequence analysis of putative virulence genes of Brazilian orf virus isolates

The parapoxvirus orf virus (ORFV) is the agent of contagious ecthyma, an ubiquitous mucocutaneous disease of sheep and goats that may present variable clinical presentations. We herein studied the pathogenesis of ORFV infection in lambs and analyzed three putative virulence genes of four Brazilian ORFV isolates. Lambs inoculated in the labial commissures with each ORFV isolate (n=4, viral titer 10(5.6) TCID50/ml) developed classical orf lesions, characterized by a progressive course of erythema/macules, vesicles, pustules and proliferative scabs. Lesions lasted an average of 22.9 days (18-26) and virus shedding was detected for approximately 24.6 days (18-30). Two isolates (SV269/11 and SV820/10) produced more severe, long-lasting lesions resulting in highest clinical scores. Lambs inoculated with isolate SV581/11 developed lesions markedly milder (lower clinical scores [p<0.05]) and more limited than the other groups. Virus shedding by SV581/11 group, however, lasted similarly or even longer than the other groups. Sequence analysis of three virulence genes (VEGF, VIR and IL-10v) revealed amino acid deletions and mutations in VEGF and IL-10v genes of SV581/11 and SV252/11, the isolate(s) producing milder lesions. Additionally, the VEGF gene of isolate SV581/11 presented the lowest amino acid identity with the other isolates and with ORFV standard strain OV-IA82. Thus, these results demonstrate that ORFV isolates may display differential virulence in lambs and these differences might be associated with genetic changes in putative virulence genes.

Inactivated Parapoxvirus ovis induces a transient increase in the expression of proinflammatory, Th1-related, and autoregulatory cytokines in mice

The immunostimulatory properties of inactivated Parapoxvirus ovis (iPPVO) have long been investigated in different animal species and experimental settings. In this study, we investigated the effects of iPPVO on cytokine expression in mice after intraperitoneal inoculation. Spleen and sera collected from iPPVO-treated mice at intervals after inoculation were submitted to cytokine mRNA determination by real-time PCR (qPCR), serum protein concentration by ELISA, and interferon (IFN)-α/β activity by bioassay. The spleen of iPPVO-treated animals showed a significant increase in mRNA expression of all cytokines assayed, with different kinetics and magnitude. Proinflammatory cytokines interleukin (IL)-1β, tumor necrosis factor-alpha (TNF-α), and IL-8 mRNA peaked at 24 hours postinoculation (hpi; 5.4-fold increase) and 48 hpi (3- and 10-fold increases), respectively. A 15-fold increase in IFN-γ and 6-fold IL-12 mRNA increase were detected at 48 and 24 hpi, respectively. Increased expression of autoregulatory cytokines (Th2), mainly IL-10 and IL-4, could be detected at later times (72 and 96 hpi) with peaks of 4.7- and 4.9-fold increases, respectively. IFN-I antiviral activity against encephalomyocarditis virus was demonstrated in sera of treated animals between 6 and 12 hpi, with a >90% reduction in the number of plaques. Measurement of serum proteins by ELISA revealed increased levels of IL-1, TNF-α, IL-12, IFN-γ, and IL-10, with kinetics similar to those observed by qPCR, especially for IL-12 and IFN-γ. These data demonstrate that iPPVO induced a transient and complex cytokine response, initially represented by Th1-related cytokines followed by autoregulatory and Th2 cytokines.

New Orf virus (Parapoxvirus) recombinant expressing H5 hemagglutinin protects mice against H5N1 and H1N1 influenza A virus

Previously we demonstrated the versatile utility of the Parapoxvirus Orf virus (ORFV) as a vector platform for the development of potent recombinant vaccines. In this study we present the generation of new ORFV recombinants expressing the hemagglutinin (HA) or nucleoprotein (NP) of the highly pathogenic avian influenza virus (HPAIV) H5N1. Correct foreign gene expression was examined in vitro by immunofluorescence, Western blotting and flow cytometry. The protective potential of both recombinants was evaluated in the mouse challenge model. Despite adequate expression of NP, the recombinant D1701-V-NPh5 completely failed to protect mice from lethal challenge. However, the H5 HA-expressing recombinant D1701-V-HAh5n mediated solid protection in a dose-dependent manner. Two intramuscular (i.m.) injections of the HA-expressing recombinant protected all animals from lethal HPAIV infection without loss of body weight. Notably, the immunized mice resisted cross-clade H5N1 and heterologous H1N1 (strain PR8) influenza virus challenge. In vivo antibody-mediated depletion of CD4-positive and/or CD8-posititve T-cell subpopulations during immunization and/or challenge infection implicated the relevance of CD4-positive T-cells for induction of protective immunity by D1701-V-HAh5n, whereas the absence of CD8-positive T-cells did not significantly influence protection. In summary, this study validates the potential of the ORFV vectored vaccines also to combat HPAIV.

Animal poxvirus vaccines: a comprehensive review

The family Poxviridae includes several viruses of medical and veterinary importance. Global concerted efforts combined with an intensive mass-vaccination campaign with highly efficaceious live vaccine of vaccinia virus have led to eradication of smallpox. However, orthopoxviruses affecting domestic animals continue to cause outbreaks in several endemic countries. Different kinds of vaccines starting from conventional inactivated/attenuated to recombinant protein-based vaccines have been used for control of poxvirus infections. Live virus homologous vaccines are currently in use for diseases including capripox, parapox, camelpox and fowlpox, and these vaccines are highly effective in eliciting (with the exception of parapoxviruses) long-lasting immunity. Attenuated strains of poxviruses have been exploited as vectored vaccines to deliver heterologous immunogens, many of them being licensed for use in animals. Worthy of note are vaccinia virus, fowlpox virus, capripoxvirus, parapoxvirus and canary pox, which have been successfully used for developing new-generation vaccines targeting many important pathogens. Remarkable features of these vaccines are thermostability and their ability to engender both cellular and humoral immune responses to the target pathogens. This article updates the important vaccines available for poxviruses of livestock and identifies some of the research gaps in the present context of poxvirus research.

A Case of Contagious Ecthyma (Orf Virus) in a Nonmanipulated Laboratory Dorset Sheep (Ovis aries)

An approximately 5-month-old laboratory wether, originating from a local vendor with a closed flock and maintained on a preventative medicine plan, presented with a continuum of lesions from hemorrhagic papules, vesicles, and pustules, to multifocal necrotic scabs at the commissure of the lips, medial canthus of the left eye, and distal prepuce. A presumptive diagnosis of Orf virus (ORFV) was made and the sheep was euthanized. A full necropsy was performed, and histopathological evaluation of affected tissues revealed multifocal-to-coalescing necrotizing and proliferative cheilitis and dermatitis with eosinophilic intracytoplasmic inclusion bodies. Electron microscopy findings revealed degenerate keratinocytes containing numerous typical 200–300 nm wide cytoplasmic parapoxvirus virions, confirming the diagnosis of ORFV. We believe that this animal developed a clinical case of ORFV either due to an adverse reaction to an ORFV vaccine, or this animal had a case of preexisting ORFV which manifested after arrival at our facility.

A new rabies vaccine based on a recombinant ORF virus (parapoxvirus) expressing the rabies virus glycoprotein

The present study describes the generation of a new Orf virus (ORFV) recombinant, D1701-V-RabG, expressing the rabies virus (RABV) glycoprotein that is correctly presented on the surface of infected cells without the need of replication or production of infectious recombinant virus. One single immunization with recombinant ORFV can stimulate high RABV-specific virus-neutralizing antibody (VNA) titers in mice, cats, and dogs, representing all nonpermissive hosts for the ORFV vector. The protective immune response against severe lethal challenge infection was analyzed in detail in mice using different dosages, numbers, and routes for immunization with the ORFV recombinant. Long-term levels of VNA could be elicited that remained greater than 0.5 IU per ml serum, indicative for the protective status. Single applications of higher doses (10(7) PFU) can be sufficient to confer complete protection against intracranial (i.c.) challenge, whereas booster immunization was needed for protection by the application of lower dosages. Anamnestic immune responses were achieved by each of the seven tested routes of inoculation, including oral application. Finally, in vivo antibody-mediated depletion of CD4-positive and/or CD8-posititve T cell subpopulations during immunization and/or challenge infection attested the importance of CD4 T cells for the induction of protective immunity by D1701-V-RabG. This report demonstrates another example of the potential of the ORFV vector and also indicates the capability of the new recombinant for vaccination of animals.

Orf virus interferes with MHC class I surface expression by targeting vesicular transport and Golgi

BACKGROUND

The Orf virus (ORFV), a zoonotic Parapoxvirus, causes pustular skin lesions in small ruminants (goat and sheep). Intriguingly, ORFV can repeatedly infect its host, despite the induction of a specific immunity. These immune modulating and immune evading properties are still unexplained.

RESULTS

Here, we describe that ORFV infection of permissive cells impairs the intracellular transport of MHC class I molecules (MHC I) as a result of structural disruption and fragmentation of the Golgi apparatus. Depending on the duration of infection, we observed a pronounced co-localization of MHC I and COP-I vesicular structures as well as a reduction of MHC I surface expression of up to 50%. These subversion processes are associated with early ORFV gene expression and are accompanied by disturbed carbohydrate trimming of post-ER MHC I. The MHC I population remaining on the cell surface shows an extended half-life, an effect that might be partially controlled also by late ORFV genes.

CONCLUSIONS

The presented data demonstrate that ORFV down-regulates MHC I surface expression in infected cells by targeting the late vesicular export machinery and the structure and function of the Golgi apparatus, which might aid to escape cellular immune recognition.

Vacina experimental produzida em cultivo celular confere proteção parcial contra o ectima contagioso em ovinos

O ectima contagioso (também conhecido como orf), é uma doença debilitante de ovinos e caprinos causada pelo vírus do orf (ORFV). A vacinação tem sido usada com relativo sucesso no controle da doença. No entanto, as vacinas atuais contêm amostras virulentas do agente, são produzidas por escarificação cutânea de animais, e apresentam eficácia questionável. Assim, o presente trabalho teve como objetivo produzir e testar a eficácia de uma vacina experimental produzida em cultivo celular. A cepa IA-82 do ORFV foi submetida a 21 passagens em cultivo de células BHK-21 e usada para vacinar ovinos jovens (n=30), por escarificação cutânea na face interna da coxa. A vacinação produziu pústulas e crostas em 16 dos 30 ovinos vacinados, indicando imunização adequada. Noventa dias após a vacinação, ovinos vacinados (n=16) e controles (n=16) foram inoculados com uma cepa virulenta do ORFV (10(6,9)DICC50/mL) após escarificação na comissura labial. Todos os animais desenvolveram lesões típicas de ectima, incluindo hiperemia, vesículas, pústulas e crostas. No entanto, os animais vacinados desenvolveram lesões mais leves e passageiras do que os controles, e os escores clínicos foram estatisticamente diferentes (p<0,05) entre os dias 10 e 22 pós-desafio. Além disso, o tempo de duração da doença foi significativamente inferior (p<0,05) nos animais vacinados. Os animais vacinados também excretaram menor quantidade de vírus (p<0,05) e por um período significativamente mais curto do que os controles (13 dias versus 22 dias, p<0,001). Esses resultados demonstram a proteção parcial conferida pela vacina experimental e, dependendo da melhoria dos índices de imunização e proteção, são promissores no sentido da utilização de vacinas contra o ORFV produzidas em cultivo celular.

Virological and clinico-pathological features of orf virus infection in experimentally infected rabbits and mice

Many aspects of the biology of orf virus (ORFV) infection remain poorly understood and attempts to establish animal models have yielded conflicting and non-reproducible results. We herein describe the characterization of ORFV infection and disease in rabbits and mice. A protocol of intradermal inoculation was employed to inoculate 10(8.5)TCID₅₀/mL of ORFV strain IA-82 in the skin of ears, of the back and labial commissures. All inoculated rabbits presented a clinical course characterized by erythema, macules, papules/vesicles or pustules that eventually dried originating scabs. Local signs started around days 3 and 4 post-inoculation (pi) and lasted 3-10 days. Virus was recovered from lesions between days 2 and 14pi. Histological examination of lesions revealed focal proliferative dermatitis with ballooning degeneration and eosinophilic intracytoplasmic inclusion bodies in keratinocytes, histological hallmarks of contagious ecthyma in sheep. A similar, albeit milder clinical course occurred in 5/10 inoculated mice; virus was recovered from lesions from three animals. Inoculated lambs - used as controls - developed severe lesions of contagious ecthyma. VN tests performed at day 28pi failed to detect neutralizing antibodies in all inoculated animals. In contrast, convalescent rabbit sera were positive by ELISA at dilutions from 100 to 400. These results show that rabbits are susceptible to ORFV infection and thus may be used to study selected aspects of ORFV biology.

The chemokine-binding protein encoded by the poxvirus orf virus inhibits recruitment of dendritic cells to sites of skin inflammation and migration to peripheral lymph nodes

Orf virus (ORFV) is a zoonotic parapoxvirus that induces acute pustular skin lesions in sheep and humans. ORFV can reinfect its host and the discovery of several secreted immune modulatory factors that include a chemokine-binding protein (CBP) may explain this phenomenon. Dendritic cells (DC) are professional antigen presenting cells that induce adaptive immunity and their recruitment to sites of infection in skin and migration to peripheral lymph nodes is critically dependent on inflammatory and constitutive chemokine gradients respectively. Here we examined whether ORFV-CBP could disable these gradients using mouse models. Previously we established that ORFV-CBP bound murine inflammatory chemokines with high affinity and here we show that this binding spectrum extends to constitutive chemokines CCL19 and CCL21. Using cell-based chemotaxis assays, ORFV-CBP inhibited the movement of both immature and mature DC in response to these inflammatory and constitutive chemokines respectively. Moreover in C57BL/6 mice, intradermally injected CBP potently inhibited the recruitment of blood-derived DC to lipopolysaccharide-induced sites of skin inflammation and inhibited the migration of ex vivo CpG-activated DC to inguinal lymph nodes. Finally we showed that ORFV-CBP completely inhibited T responsiveness in the inguinal lymph nodes using intradermally injected DC pulsed with ovalbumin peptide and transfused transgenic T cells.

Conventional bone marrow-derived dendritic cells contribute to toll-like receptor-independent production of alpha/beta interferon in response to inactivated parapoxvirus ovis

Parapoxvirus ovis (PPVO) is a member of the Poxviridae family and belongs to the genus Parapoxvirus. It displays only limited homology with orthopoxviruses and has some molecular features such as an unusual high GC content distinct from orthopoxviruses. Inactivated PPVO (iPPVO) displays strong immunostimulatory capacities mediating antiviral activity in vivo. The role of dendritic cells (DC) and the pattern recognition receptors and signaling requirements responsible for immunostimulation by iPPVO are unknown. We demonstrate here that bone marrow-derived plasmacytoid DC (BM-pDC) and bone marrow-derived conventional DC (BM-cDC) secrete alpha/beta interferon (IFN-alpha/beta) in response to iPPVO. Furthermore, iPPVO induces tumor necrosis factor alpha (TNF-alpha) and interleukin-12/23p40 (IL-12/23p40) release and major histocompatibility complex class II (MHC-II), MHC-I, and CD86 upregulation by bone marrow-derived DC (BMDC). After engulfment, iPPVO is located in endosomal compartments and in the cytosol of BMDC. iPPVO elicits IFN-alpha/beta by Toll-like receptor (TLR)-independent pathways in BM-cDC, since IFN-alpha/beta release does not require myeloid differentiation primary response gene 88 (MyD88) or TIR-domain containing adaptor protein inducing interferon (TRIF). In contrast, iPPVO-induced TNF-alpha release and enhanced expression of MHC-I and CD86 but not of MHC-II by BMDC chiefly requires MyD88 but not TLR2 or TLR4. Induction of IFN-alpha by iPPVO in BM-cDC occurred in the absence of IFN regulatory factor 3 (IRF3) but required the presence of IRF7, whereas iPPVO-triggered IFN-beta production required the presence of either IRF7 or IRF3. These results provide the first evidence that iPPVO mediates its immunostimulatory properties by TLR-independent and TLR-dependent pathways and demonstrate an important role of cDC for IFN-alpha/beta production.

The structure of a putative scaffolding protein of immature poxvirus particles as determined by electron microscopy suggests similarity with capsid proteins of large icosahedral DNA viruses

Orf virus, the prototype parapoxvirus, is responsible for contagious ecthyma in sheep and goats. The central region of the viral genome codes for proteins highly conserved among vertebrate poxviruses and which are frequently essential for viral proliferation. Analysis of the recently published genome sequence of orf virus revealed that among such essential proteins, the protein orfv075 is an orthologue of D13, the rifampin resistance gene product critical for vaccinia virus morphogenesis. Previous studies showed that D13, arranged as "spicules," is necessary for the formation of vaccinia virus immature virions, a mandatory intermediate in viral maturation. We have determined the three-dimensional structure of recombinant orfv075 at approximately 25-A resolution by electron microscopy of two-dimensional crystals. orfv075 organizes as trimers with a tripod-like main body and a propeller-like smaller domain. The molecular envelope of orfv075 shows unexpectedly good agreement to that of a distant homologue, VP54, the major capsid protein of Paramecium bursaria Chlorella virus type 1. Our structural analysis suggests that orfv075 belongs in the double-barreled capsid protein family found in many double-stranded DNA icosahedral viruses and supports the hypothesis that the nonicosahedral poxviruses and the large icosahedral DNA viruses are evolutionarily related.