Orf virus (ORFV) OV20.0L is an ortholog of vaccinia virus (VACV) gene E3L. The function of VACV E3 protein as a virulence factor is well studied, but OV20.0 has received less attention. Here we show that like VACV E3L, OV20.0L encodes two proteins, a full-length protein and a shorter form (sh20). The shorter sh20 is an N-terminally truncated OV20.0 isoform generated when a downstream AUG codon is used for initiating translation. These isoforms differed in cellular localization, with full-length OV20.0 and sh20 found throughout the cell and predominantly in the cytoplasm, respectively. Nonetheless, both OV20.0 isoforms were able to bind double-stranded RNA (dsRNA)-activated protein kinase (PKR) and dsRNA. Moreover, both isoforms strongly inhibited PKR activation as shown by decreased phosphorylation of the translation initiation factor eIF2␣ subunit and protection of Sindbis virus infection against the activity of interferon (IFN). In spite of this apparent conservation of function in vitro, a recombinant ORFV that was able to express only the sh20 isoform was attenuated in a mouse model. IMPORTANCEThe OV20.0 protein of orf virus (ORFV) has two isoforms and contributes to virulence, but the roles of the two forms are not known. This study shows that the shorter isoform (sh20) arises due to use of a downstream initiation codon and is amino-terminally truncated. The sh20 form also differs in expression kinetics and cellular localization from full-length OV20.0. Similar to the full-length isoform, sh20 is able to bind dsRNA and PKR, inactivate PKR, and thus act as an antagonist of the interferon response in vitro. In vivo, however, wild-type OV20.0 could not be replaced with sh20 alone without a loss of virulence, suggesting that the functions of the isoforms are not simply redundant. Orf virus (ORFV), a member of the Parapoxvirus genus and the Poxviridae family, is the causative agent of contagious ecthyma in sheep, goats, and other ruminants. The disease is characterized by the development of pustular lesions around the nostrils and mouth with a high incidence rate and a low mortality rate in healthy adult animals. In contrast, infection in immunosuppressed animals or in lambs may be fatal (1). ORFV is also of concern as a source of zoonotic infection because it can cause cutaneous lesions in humans in contact with infected animals. Persistent infection with ORFV can be observed in goats and sheep, and while the severity of lesions is reduced compared with that seen in primary infection, this persistence suggests that the virus is able to evade host immunity (2-4). In line with this observation, ORFV has been shown to encode several proteins that modulate the host response to infection. These include viral homologues of ovine cytokines, such as vascular endothelial growth factor, interleukin-10 (IL-10), and a granulocyte-macrophage colony-stimulating factor (GM-CSF)-inhibiting protein, as well as an apoptosis inhibitor (5-7). ORFV also antagonizes interferon (IFN) signaling, and this is done by the product...
Background The objective of this study was to determine the sensitivity (Se) and specificity (Sp) of bovine tuberculosis (bTB) screening tests including a single intradermal tuberculin (SIT) test, interferon gamma (IFN-γ) assay, and a commercial ELISA test ( M. bovis Ab) in dairy cattle, under field conditions, using a Bayesian approach. Results The study population consisted of 128 dairy cows from 25 bTB-infected herds in Chiang Mai and Chiang Rai provinces, Thailand. A single-population Bayesian model was implemented assuming conditional dependence between the SIT test and IFN-γ assays. The 95% posterior probability interval (PPI) of the SIT test (severe interpretation) Se ranged from 75.3 to 95.2% (median = 87.6%), while the Sp was slightly lower (median = 83.6%, PPI = 74.2–92.8%). The IFN-γ assay Se was moderate and the 95% PPI ranged from 38.6 to 74.4% (median = 55.7%) with higher Sp (median = 93.5.4%, PPI = 87.0–98.1%). The M. bovis Ab ELISA Se was low, with 95% PPI ranging between 30.0 and 71.2% (median = 47.4%); however, the Sp was high (median = 90.9%, PPI = 84.5–95.5%). Conclusion The SIT test sensitivity was similar to that demonstrated in other regions and can, therefore, be used effectively as part of control programs in this area. The IFN-γ and M. bovis Ab ELISA assays can be applied as supplementary techniques. The test performance of these tests when used as single tests without confirmation, however, are expected to continue to challenge disease eradication efforts. Electronic supplementary material The online version of this article (10.1186/s12917-019-1905-x) contains supplementary material, which is available to authorized users.
Mouse mammary tumor virus (MMTV) has been speculated to be involved in human breast cancer. Companion animals, dogs, and cats with intimate human contacts may contribute to the transmission of MMTV between mouse and human. The aim of this study was to detect MMTV-like nucleotide sequences in canine and feline mammary tumors by nested PCR. Results showed that the presence of MMTV-like env and LTR sequences in canine malignant mammary tumors was 3.49% (3/86) and 18.60% (16/86), respectively. For feline malignant mammary tumors, the presence of both env and LTR sequences was found to be 22.22% (2/9). Nevertheless, the MMTV-like LTR and env sequences also were detected in normal mammary glands of dogs and cats. In comparisons of the MMTV-like DNA sequences of our findings to those of NIH 3T3 (MMTVpositive murine cell line) and human breast cancer cells, the sequence similarities ranged from 94 to 98%. Phylogenetic analysis revealed that intermixing among sequences identified from tissues of different hosts, i.e., mouse, dog, cat, and human, indicated the MMTV-like DNA existing in these hosts. Moreover, the env transcript was detected in 1 of the 19 MMTV-positive samples by reverse transcription-PCR. Taken together, our study provides evidence for the existence and expression of MMTV-like sequences in neoplastic and normal mammary glands of dogs and cats.Several environmental risk factors have been proposed for sporadic human breast cancer, including mouse mammary tumor virus (MMTV). MMTV is an oncogenic retrovirus that induces breast cancer in mice and that can be isolated either as an endogenous or exogenous virus (3). Possible links of MMTV to human breast cancer have been indicated. Previous studies have demonstrated that MMTV-like sequences, which share at least 95% identity with MMTV, are highly expressed in human breast cancer (7,(28)(29)(30). Furthermore, viral particles produced in primary cell cultures derived from breast cancer are similar to those of MMTV (18).In addition, geographical variations in the incidence of human breast cancer with the distribution map of the natural range of certain species of mice, particularly Mus domesticus, were correlated. The area where M. domesticus mice are endemic coincides to a large extent with the countries having a high prevalence of breast cancer (22). A previous study reported that MMTV-positive samples were found only in the Australian group (with high incidences of breast cancer and M. domesticus) but not in the Vietnamese group (low prevalence of breast cancer and M. domesticus) (10). These results suggest that M. domesticus harbors and transfers a human-tropic strain of MMTV. However, the contribution of MMTV to breast carcinogenesis was not endorsed by recent studies, which reported no evidence for the existence of MMTV-like sequences in human breast cancer of Germanic (11) and Japanese patients (12). The controversial finding could be explained by the fact that Mus domesticus is not widely distributed in Germany (11) or Japan (12).Moreover, besides human and...
BackgroundCanine distemper virus (CDV) is present worldwide and produces a lethal systemic infection of wild and domestic Canidae. Pre-existing antibodies acquired from vaccination or previous CDV infection might interfere the interpretation of a serologic diagnosis method. In addition, due to the high similarity of nucleic acid sequences between wild-type CDV and the new vaccine strain, current PCR derived methods cannot be applied for the definite confirmation of CD infection. Hence, it is worthy of developing a simple and rapid nucleotide-based assay for differentiation of wild-type CDV which is a cause of disease from attenuated CDVs after vaccination. High frequency variations have been found in the region spanning from the 3'-untranslated region (UTR) of the matrix (M) gene to the fusion (F) gene (designated M-F UTR) in a few CDV strains. To establish a differential diagnosis assay, an amplification refractory mutation analysis was established based on the highly variable region on M-F UTR and F regions.ResultsSequences of frequent polymorphisms were found scattered throughout the M-F UTR region; the identity of nucleic acid between local strains and vaccine strains ranged from 82.5% to 93.8%. A track of AAA residue located 35 nucleotides downstream from F gene start codon highly conserved in three vaccine strains were replaced with TGC in the local strains; that severed as target sequences for deign of discrimination primers. The method established in the present study successfully differentiated seven Taiwanese CDV field isolates, all belonging to the Asia-1 lineage, from vaccine strains.ConclusionsThe method described herein would be useful for several clinical applications, such as confirmation of nature CDV infection, evaluation of vaccination status and verification of the circulating viral genotypes.
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