Host species barriers to Jaagsiekte sheep retrovirus replication and carcinogenesis

Molecular detection of mixed infection with peste des petits ruminants and retroviruses in Egyptian sheep and goats

Peste des petits ruminants (PPR) is a contagious viral disease causing massive economic loss to animal industries in endemic countries including Egypt. Although a vaccine is available, coinfections can overwhelm the animal immune system and interfere with vaccine protection. Small ruminant retrovirus (SRR), including enzootic nasal tumor virus (ENTV) and Jaagsiekte sheep retrovirus (JSRV), is responsible for coinfections with PPR. Investigation of clinical cases in this study confirmed the presence of PPR virus by RT-PCR among four flocks. Sequence of five PPR amplicons revealed that all strains had 100% aa similarity and belonged to lineage IV. In addition, these strains had 98-99% nt similarity with all previous Egyptian and African strains from Sudan (MK371449) and Ethiopia (MK371449). Illumina sequencing of a representative sample showed a genome of 5753 nt compatible with ENT-2 virus with 98.42% similarity with the Chinese strain (MN564750.1). Four ORFs representing gag, pro, pol, and env genes were identified and annotated. Pro gene was highly stable while gag, pol, and env showed eight, two, and three aa differences with the reference strains. Sanger sequencing revealed that two amplicons were ENT-2 virus, and one was JSRV. ENT-2 sequences had 100% similarity with KU258870 and KU258871 reference strains while JSRV was 100% similar to the EF68031 reference strain. The phylogenetic tree showed a close relationship between the ENT of goats and the JSRV of sheep. This study highlights the complexity of PPR molecular epidemiology, with SRR that was not molecularly characterized previously in Egypt.

Enzootic nasal tumor virus type 2 envelope of goats acts as a retroviral oncogene in cell transformation

Enzootic nasal tumor virus type 1 (ENTV-1) (ovine nasal tumor virus) and ENTV-2 (caprine nasal tumor virus) are known to be causative agents of enzootic nasal adenocarcinoma (ENA) in sheep and goats, respectively. Although the nucleotide and amino acid sequences of ENTV-1 and ENTV-2 are quite similar, they are recognized as phylogenetically distinct viruses. The envelope protein of ENTV-1 functions as an oncoprotein in the in vitro transformation of epithelial cells and fibroblasts. Thus, it is the primary determinant of in vivo tumorigenesis in ENA. As per our knowledge, no previous studies have reported in detail the role of ENTV-2 in ENA tumorigenesis. Here, in order to investigate the molecular mechanism of caprine ENA oncogenesis by ENTV-2, we have attempted to identify the transforming potential of ENTV-2 envelope, and investigated the activation of cell signaling pathways in oncogenic transformation. Our findings confirmed that ENTV-2 envelope was capable of inducing oncogenic transformation of rat cell lines in vitro. Further, we found that MAPK, Akt, and p38 were constitutively activated in ENTV-2 envelope-transformed clone cells. In addition, inhibitor experiments revealed that MEK-MAPK and PI3K-Akt signaling pathways are involved in the ENTV-2 envelope-induced cell transformation. These data indicate that ENTV-2 envelope could induce oncogenic transformation by signaling pathways that are also utilized by ENTV-1 envelope.

Exogenous Jaagsiekte Sheep Retrovirus type 2 (exJSRV2) related to ovine pulmonary adenocarcinoma (OPA) in Romania: prevalence, anatomical forms, pathological description, immunophenotyping and virus identification

BACKGROUND

Ovine pulmonary adenocarcinoma (OPA) is a neoplastic disease caused by exogenous Jaagsiekte Sheep Retrovirus (exJSRV). The prevalence of JSRV-related OPA in Eastern European countries, including Romania is unknown. We aimed to investigate: the prevalence and morphological features of OPA (classical and atypical forms) in the Transylvania region (Romania), the immunophenotype of the pulmonary tumors and their relationships with exJSRV infection. A total of 2693 adult ewes slaughtered between 2017 and 2019 in two private slaughterhouses from Transylvania region (Romania) was evaluated. Lung tumors were subsequently assessed by cytology, histology, immunocytochemistry, immunohistochemistry, electron microscopy and DNA testing.

RESULTS

Out of 2693 examined sheep, 34 had OPA (1.26% prevalence). The diaphragmatic lobes were the most affected. Grossly, the classical OPA was identified in 88.24% of investigated cases and the atypical OPA in 11.76% that included solitary myxomatous nodules. Histopathology results confirmed the presence of OPA in all suspected cases, which were classified into acinar and papillary types. Myxoid growths (MGs) were diagnosed in 6 classical OPA cases and in 2 cases of atypical form. Lung adenocarcinoma was positive for MCK and TTF-1, and MGs showed immunoreaction for Vimentin, Desmin and SMA; Ki67 expression of classical OPA was higher than atypical OPA and MGs. JSRV-MA was identified by IHC (94.11%) in both epithelial and mesenchymal cells of OPA. Immunocytochemistry and electron microscopy also confirmed the JSRV within the neoplastic cells. ExJSRV was identified by PCR in 97.05% of analyzed samples. Phylogenetic analysis revealed the presence of the exJSRV type 2 (MT809678.1) in Romanian sheep affected by lung cancer and showed a high similarity with the UK strain (AF105220.1).

CONCLUSIONS

In this study, we confirmed for the first time in Romania the presence of exJSRV in naturally occurring OPA in sheep. Additionally, we described the first report of atypical OPA in Romania, and to the best of our knowledge, in Eastern Europe. Finally, we showed that MGs have a myofibroblastic origin.

A Novel Enzootic Nasal Tumor Virus Circulating in Goats from Southern China

Enzootic nasal tumor virus (ENTV) has two types, ENTV-1 in sheep and ENTV-2 in goats, respectively. In China, the incidence of ENTV-2 related diseases has increased year by year. In this study, we reported an outbreak of ENTV-2 in a commercial goat farm in Qingyuan city, Guangdong province, southern China. A full-length genome of ENTV-2 (designated GDQY2017), with 7479 base pairs, was sequenced. Although GDQY2017 shared the highest nucleotide identity with a Chinese ENTV-2 isolate (ENTV-2CHN4, GenBank accession number KU258873), it possesses distinct genome characteristics undescribed, including a non-continuous 21-nucleotide insertion in the gag gene and a non-continuous 12-nucleotide deletion in the env gene. Notably, most of these indel nucleotide sequences were originated from a Chinese jaagsiekte sheep retrovirus (JSRV) isolate (GenBank accession number DQ838494). In the gag and env genes, GDQY2017 was phylogenetically related to those Chinese ENTV-2 isolates and a Chinese JSRV isolate (DQ838494). For GDQY2017-like viruses, more surveillance work should be made to explain their pathogenicity in goat herds. To our knowledge, this study represents the first to demonstrate the circulating pattern of ENTV-2 in Guangdong province, China, which will help to better understand the epidemiology and genetic diversity of ENTV-2.

Ovine Pulmonary Adenocarcinoma: A Unique Model to Improve Lung Cancer Research

Lung cancer represents a major worldwide health concern; although advances in patient management have improved outcomes for some patients, overall 5-year survival rates are only around 15%. In vitro studies and mouse models are commonly used to study lung cancer and their use has increased the molecular understanding of the disease. Unfortunately, mouse models are poor predictors of clinical outcome and seldom mimic advanced stages of the human disease. Animal models that more accurately reflect human disease are required for progress to be made in improving treatment outcomes and prognosis. Similarities in pulmonary anatomy and physiology potentially make sheep better models for studying human lung function and disease. Ovine pulmonary adenocarcinoma (OPA) is a naturally occurring lung cancer that is caused by the jaagsiekte sheep retrovirus. The disease is endemic in many countries throughout the world and has several features in common with human lung adenocarcinomas, including histological classification and activation of common cellular signaling pathways. Here we discuss the in vivo and in vitro OPA models that are currently available and describe the advantages of using pre-clinical naturally occurring OPA cases as a translational animal model for human lung adenocarcinoma. The challenges and options for obtaining these OPA cases for research purposes, along with their use in developing novel techniques for the evaluation of chemotherapeutic agents or for monitoring the tumor microenvironment in response to treatment, are also discussed.

Use of Precision-Cut Lung Slices as an Ex Vivo Tool for Evaluating Viruses and Viral Vectors for Gene and Oncolytic Therapy

Organotypic slice cultures recapitulate many features of an intact organ, including cellular architecture, microenvironment, and polarity, making them an ideal tool for the ex vivo study of viruses and viral vectors. Here, we describe a procedure for generating precision-cut ovine and murine tissue slices from agarose-perfused normal and murine melanoma tumor-bearing lungs. Furthermore, we demonstrate that these precision-cut lung slices can be maintained up to 1 month and can be used for a range of applications, which include characterizing the tissue tropism of viruses that cannot be propagated in cell monolayers, evaluating the transducing properties of gene therapy vectors, and, finally, investigating the tumor specificity of oncolytic viruses. Our results suggest that ex vivo lung slices are an ideal platform for studying the tissue specificity and cancer cell selectivity of gene therapy vectors and oncolytic viruses prior to in vivo studies, providing justification for pre-clinical work.

Ovine pulmonary adenocarcinoma: a large animal model for human lung cancer

Lung cancer is the leading cause of cancer deaths worldwide. Recent progress in understanding the molecular pathogenesis of this disease has resulted in novel therapeutic strategies targeting specific groups of patients. Further studies are required to provide additional advances in diagnosis and treatment. Animal models are valuable tools for studying oncogenesis in lung cancer, particularly during the early stages of disease where tissues are rarely available from human cases. Mice have traditionally been used for studying lung cancer in vivo, and a variety of spontaneous and transgenic models are available. However, it is recognized that other species may also be informative for studies of cancer. Ovine pulmonary adenocarcinoma (OPA) is a naturally occurring lung cancer of sheep caused by retrovirus infection and has several features in common with adenocarcinoma of humans, including a similar histological appearance and activation of common cell signaling pathways. Additionally, the size and organization of human lungs are much closer to those of sheep lungs than to those of mice, which facilitates experimental approaches in sheep that are not available in mice. Thus OPA presents opportunities for studying lung tumor development that can complement conventional murine models. Here we describe the potential applications of OPA as a model for human lung adenocarcinoma with an emphasis on the various in vivo and in vitro experimental systems available.

Seroconversion of sheep experimentally infected with enzootic nasal tumor virus

BACKGROUND

Enzootic nasal tumor virus (ENTV-1) is an exogenous betaretrovirus of sheep that transforms epithelial cells lining the ethmoid turbinates leading to a disease called enzootic nasal adenocarcinoma (ENA). A unique feature of ENA is the apparent absence of a specific humoral immune response to the virus, despite the highly productive infection in nasal tumors. The sheep genome contains approximately 27 copies of endogenous ovine betaretroviral sequences (enJSRVs) and expression of enJSRVs in the ovine placenta and uterine endometrium throughout gestation is thought to induce immunological tolerance to exogenous ovine betaretroviruses, a factor that may influence the likelihood of exogenous ENTV infection and disease outcome. Nevertheless, we recently demonstrated the presence of neutralizing antibodies directed against the ENTV-1 envelope glycoprotein in sheep naturally exposed to ENTV-1.

FINDINGS

Here, we employed an ENTV-1 envelope glycoprotein surface subunit specific ELISA and a virus neutralization assay to monitor serum antibody responses to ENTV-1 in a group of lambs experimentally infected with ENTV-1 virus containing filtered ENA tumor homogenate. Seroconversion and development of neutralizing antibodies was detected in one of six experimentally infected lambs.

CONCLUSIONS

Our results demonstrate that sheep can respond immunologically and seroconvert following ENTV-1 infection suggesting that anti-viral immune responses may play a role in the development of ENA.

"Ménage à Trois": the evolutionary interplay between JSRV, enJSRVs and domestic sheep

Sheep betaretroviruses represent a fascinating model to study the complex evolutionary interplay between host and pathogen in natural settings. In infected sheep, the exogenous and pathogenic Jaagsiekte sheep retrovirus (JSRV) coexists with a variety of highly related endogenous JSRVs, referred to as enJSRVs. During evolution, some of them were co-opted by the host as they fulfilled important biological functions, including placental development and protection against related exogenous retroviruses. In particular, two enJSRV loci, enJS56A1 and enJSRV-20, were positively selected during sheep domestication due to their ability to interfere with the replication of related competent retroviruses. Interestingly, viruses escaping these transdominant enJSRVs have recently emerged, probably less than 200 years ago. Overall, these findings suggest that in sheep the process of endogenization is still ongoing and, therefore, the evolutionary interplay between endogenous and exogenous sheep betaretroviruses and their host has not yet reached an equilibrium.

Exploiting ovine immunology to improve the relevance of biomedical models

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Sheep make a valuable contribution to immunology research.

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Lessons to be learned from studying infections in the natural host.

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Factors to consider when selecting biomedical models.

Animal models of human disease are important tools in many areas of biomedicine; for example, in infectious disease research and in the development of novel drugs and medical devices. Most studies involving animals use rodents, in particular congenic mice, due to the availability of a wide number of strains and the ease with which they can be genetically manipulated. The use of mouse models has led to major advances in many fields of research, in particular in immunology but despite these advances, no animal model can exactly reproduce all the features of human disease. It is increasingly becoming recognised that in many circumstances mice do not provide the best model and that alternative species may be more appropriate. Here, we describe the relative merits of sheep as biomedical models for human physiology and disease in comparison to mice, with a particular focus on reproductive and respiratory pathogens.