Experimental transmission of enzootic intranasal tumors of goats

Tick-borne Rickettsia, Anaplasma, Theileria, and enzootic nasal tumor virus in ruminant, PET, and poultry animals in Pakistan

Introduction

Pakistan is an agricultural country; most of its income is based on livestock rearing. The increasing prevalence of tick-borne pathogens among animals may affect the animal production and livelihood of owners, which eventually derange the economy of a country.

Methodology

To further comprehend TBPs, 213 ticks were collected from different animals, including ruminants, pets, and poultry. After molecular and phylogenetic analysis identification, ticks were managed into different pools based on their species level (Hyalomma anatolicum = 80, Rhipicephalus microplus = 35, Hyalomma scupense = 23, Rhipicephalus turanicus = 70, and Rhipicephalus sanguineus = 5).

Results and discussion

After tick species identification, further molecular PCR amplification was carried out to screen out the pathogens for the presence of Theileria, Rickettsia, Anaplasma, and enzootic nasal tumor virus (ENTV). The following pathogens were detected: 11 (5.16%) for Anaplasma, 1 (0.47%) for Rickettsia, and 9 (4.23%) for Theileria. Nevertheless, other TBPs that had not been reported so far in Pakistan 3 (1.41%), were positive for enzootic nasal tumor virus (ENTV). Besides, phylogenetic analysis of the enzootic nasal tumor virus (ENTV) strain confirmed its resemblance to the Chinese strain, while Anaplasma has comparability with Pakistan and China, Rickettsia with Pakistan, China, and Iran, and Theileria with India, South Africa, United States, Japan, and Spain.

Conclusion

This study reveals that there is a considerably wider range of TBPs held in Pakistan that take in various contagious zoonotic pathogens than was previously thought. This information advances TBP epidemiology and will contribute to upgrade future control measure.

Research Progress on Emerging Viral Pathogens of Small Ruminants in China during the Last Decade

China is the country with the largest number of domestic small ruminants in the world. Recently, the intensive and large-scale sheep/goat raising industry has developed rapidly, especially in nonpastoral regions. Frequent trading, allocation, and transportation result in the introduction and prevalence of new pathogens. Several new viral pathogens (peste des petits ruminants virus, caprine parainfluenza virus type 3, border disease virus, enzootic nasal tumor virus, caprine herpesvirus 1, enterovirus) have been circulating and identified in China, which has attracted extensive attention from both farmers and researchers. During the last decade, studies examining the etiology, epidemiology, pathogenesis, diagnostic methods, and vaccines for these emerging viruses have been conducted. In this review, we focus on the latest findings and research progress related to these newly identified viral pathogens in China, discuss the current situation and problems, and propose research directions and prevention strategies for different diseases in the future. Our aim is to provide comprehensive and valuable information for the prevention and control of these emerging viruses and highlight the importance of surveillance of emerging or re-emerging viruses.

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.

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.

First detection and genotypic analysis of goat enzootic nasal tumor virus 2 in Chongqing, China

Enzootic nasal adenocarcinoma (ENA) of goats, characterized by transformation of epithelial cells of the ethmoid turbinates, is caused by enzootic nasal tumor virus 2 (ENTV-2). ENTV-2 belongs to the genus Betaretrovirus and has extended its distribution globally with a high prevalence; however, the genetic diversity and genotypic distribution for ENTV-2 have not been analyzed systematically due to the limited availability of sequence data. In this study, an infection by ENTV-2 was detected by RT-PCR in Chongqing in July 2018, and the complete sequence of one strain (CQ1) was determined. Phylogenetic analysis indicated a high degree of genetic heterogeneity among ENTV-2 sequences, with the existence of two main lineages. Lineage 1 and 2 were composed of ENTV-2 from China and the UK, respectively. Although CQ1 was closely related to recent ENTV-2 strains collected in the neighboring provinces of Chongqing (Shaanxi and Sichuan), it formed a separate sublineage of lineage 1 (sublineage 1.3). This report will enhance our understanding of the epidemiology of ENTV-2 in China.

Development of real-time PCR-based methods for the detection of enzootic nasal tumor virus 2 in goats

Enzootic nasal adenocarcinoma (ENA) is a contagious neoplasm of sheep and goats, associated with the oncogenic retroviruses enzootic nasal tumor virus (ENTV) 1 and 2, respectively. It appears to be common in countries with substantial small ruminant-production. ENA diagnosis in goats is based on autopsy and histopathology, and there is no real-time PCR method available for ENTV-2 detection. Here, a novel one-tube real-time RT-PCR (RT-qPCR) method for the detection and quantification of ENTV-2 in nasal swabs is presented. The method targets the env gene/U3 region. For the design of ENTV-2-specific oligonucleotides, molecular characterization of seven Greek ENTV-2 strains was performed. Phylogenetic analysis revealed three distinct phylogenetic clades of ENTV-2 that correlate with the country of sample collection. Evaluation of the analytical performance of the RT-qPCR revealed an amplification efficiency of 92.8% and a linear range of quantification between 2 × 10⁸ and 2 × 10² RNA transcripts. Analysis of nasal swabs from 23 histopathologically confirmed, naturally occurring ENA cases via RT-qPCR yielded positive results. Moreover, modification of the method for use in a real-time PCR (qPCR) assay enables detection of proviral DNA in tumor specimens. Both methods are highly specific and can be used for the confirmation of ENA-suspected cases. Future applications could include ante-mortem diagnosis, verification of the ENTV-2-free status in animal trade, disease surveillance, and control programs.

First case report of enzootic nasal adenocarcinoma in "Ouled Djellal" ewe in Algeria

We report clinical and pathological features of enzootic nasal adenocarcinoma (ENA) in one sheep in Algeria. A one-year-old Ouled Djellal sheep from a large herd (~1240 animals), located in Bordj Bou Arreridj, Algeria, was clinically diagnosed by the presence of persistent seromucous nasal discharge, head shaking, muzzle licking, dyspnoea, exophthalmia and frontal protrusion. The sheep was euthanized, and the necropsy was performed. Gross examination showed soft touch, pinkish-white tumour masses in the nasal cavities with distortion of the turbinates and of the medium septum. According to clinical and pathological findings, the tumour has been defined as a low grade mixed nasal adenocarcinoma, with the presence of tubular and papillary structures. This is, to our knowledge, the first report of ENA in Algeria known to be associated with enzootic nasal tumour virus (ENTV) infection. However, such association requires confirmation by direct and/or indirect viral investigation.

Identification of novel and differentially expressed MicroRNAs in goat enzootic nasal adenocarcinoma

Background

MicroRNAs (miRNAs) post-transcriptionally regulate a variety of genes involved in eukaryotic cell growth, development, metabolism and other biological processes, and numerous miRNAs are implicated in the initiation and progression of cancer. Enzootic nasal adenocarcinoma (ENA), an epithelial tumor induced in goats and sheep by enzootic nasal tumor virus (ENTV), is a chronic, progressive, contact transmitted disease.

Methods

In this work, small RNA Illumina high-throughput sequencing was used to construct a goat nasal miRNA library. This study aimed to identify novel and differentially expressed miRNAs in the tumor and para-carcinoma nasal tissues of Nanjiang yellow goats with ENA.

Results

Four hundred six known miRNAs and 29 novel miRNAs were identified. A total of 116 miRNAs were significantly differentially expressed in para-carcinoma nasal tissues and ENA (54 downregulated; 60 upregulated; two only expressed in control group); Target gene prediction and functional analysis revealed that 6176 non-redundancy target genes, 1792 significant GO and 97 significant KEGG pathway for 121 miRNAs (116 significant expression miRNAs and five star sequence) were predicted. GO and KEGG pathway analysis revealed the majority of target genes in ENA are involved in cell proliferation, signal transduction and other processes associated with cancer.

Conclusions

This is the first large-scale identification of miRNAs in Capra hircus ENA and provides a theoretical basis for investigating the complicated miRNA-mediated regulatory networks involved in the pathogenesis and progression of ENA.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3238-5) contains supplementary material, which is available to authorized users.

Genetic variability and in vitro transcriptional permissibility of primary ovine beta-retrovirus promoter isolates

OBJECTIVE

To assess genomic sequence conservation and variation in the proviral promoter of enzootic nasal tumor virus (ENTV) and Jaagsiekte sheep retrovirus (JSRV) in tissue samples from 3 sheep with nasal adenocarcinoma associated with ENTV and 3 sheep with pulmonary adenocarcinoma associated with JSRV and to identify a cell culture system that supports transcriptional activity of the ENTV and JSRV viral promoters.

ANIMALS

6 adult sheep.

PROCEDURES

Standard PCR procedures for detection of the ENTV and JSRV long terminal repeat (LTR) promoter region were performed on samples from the 3 nasal adenocarcinomas and 3 pulmonary adenocarcinomas, respectively. The LTRs were cloned into shuttle vectors, amplified, sequenced, and analyzed. The cloned LTR regions were transferred into reporter plasmids and multiple human and ruminant cell lines, and primary cells were transfected with the promoter-reporter plasmids. The viral promoter activity was evaluated by use of an in vitro β-galactosidase reporter assay.

RESULTS

Each isolate had a unique nucleotide sequence. Single nucleotide polymorphisms were the most common LTR mutation and rarely occurred at transcription factor binding sites. Relative to ENTV, the JSRV promoter isolates had a conserved 66-bp U3 insertion, including the lung-specific transcription factor HNF-3β binding site. Among the cell lines used, human embryonic kidney (293T) and goat synovial membrane cells supported promoter transcription.

CONCLUSIONS AND CLINICAL RELEVANCE

The LTRs of ENTV and JSRV have extensive blocks of sequence conservation. Human 293T and goat synovial membrane cell lines may be suitable in vitro cell culture systems for further research of viral promoter functions.

Development of an ante-mortem diagnostic test for enzootic nasal tumor virus and detection of neutralizing antibodies in host serum

Enzootic nasal adenocarcinoma (ENA) is a contagious neoplasm of the nasal mucosa of sheep and goats and is associated with enzootic nasal tumour virus (ENTV). As ENA is a common disease in North America and there are no vaccines against ENTV-1, diagnostic tests that can identify infected animals and assist with eradication and disease surveillance efforts are greatly needed. In this study, we endeavoured to develop a novel, non-invasive diagnostic tool that could be used not only to validate clinical signs of ENA but also to detect ENTV-1 infection prior to the onset of disease signs (i.e. pre-clinical diagnosis). Cytology, serology and reverse transcription (RT)-PCR-based diagnostic methods were investigated. Although the cytology-based assay was able to detect ENTV-1 infection in some animals, it had poor sensitivity and specificity and thus was not developed further as an ante-mortem diagnostic method. Three different assays, including ELISA, Western blotting and virus neutralization, were developed to detect the presence of ENTV-1-specific antibodies in sheep serum. Whilst a surprisingly large number of sheep mounted an antibody-mediated immune response against ENTV-1, and in some cases neutralizing, correlation with disease status was poor. In contrast, RT-PCR on RNA extracted from nasal swabs reliably detected exogenous ENTV-1 sequences, did not amplify endogenous ovine betaretroviral sequences, demonstrated high concordance with immunohistochemical staining for ENTV-1 envelope protein, and had perfect sensitivity and specificity. This report describes a practical and highly specific RT-PCR technique for the detection of clinical and pre-clinical ENA that may prove beneficial in future control or eradication programmes.

Experimental transmission of enzootic nasal adenocarcinoma in sheep

Enzootic nasal adenocarcinoma (ENA) is a contagious neoplasm of the secretory epithelial cells of the nasal mucosa of sheep and goats. It is associated with the betaretrovirus, enzootic nasal tumor virus (ENTV), but a causative relationship has yet to be demonstrated. In this study, 14-day-old lambs were experimentally infected via nebulization with cell-free tumor filtrates derived from naturally occurring cases of ENA. At 12 weeks post-infection (wpi), one of the five infected lambs developed clinical signs, including continuous nasal discharge and open mouth breathing, and was euthanized. Necropsy revealed the presence of a large bilateral tumor occupying the nasal cavity. At 45 wpi, when the study was terminated, none of the remaining infected sheep showed evidence of tumors either by computed tomography or post-mortem examination. ENTV-1 proviral DNA was detected in the nose, lung, spleen, liver and kidney of the animal with experimentally induced ENA, however there was no evidence of viral protein expression in tissues other than the nose. Density gradient analysis of virus particles purified from the experimentally induced nasal tumor revealed a peak reverse transcriptase (RT) activity at a buoyant density of 1.22 g/mL which was higher than the 1.18 g/mL density of peak RT activity of virus purified from naturally induced ENA. While the 1.22 g/mL fraction contained primarily immature unprocessed virus particles, mature virus particles with a similar morphology to naturally occurring ENA could be identified by electron microscopy. Full-length sequence analysis of the ENTV-1 genome from the experimentally induced tumor revealed very few nucleotide changes relative to the original inoculum with only one conservative amino acid change. Taken together, these results demonstrate that ENTV-1 is associated with transmissible ENA in sheep and that under experimental conditions, lethal tumors are capable of developing in as little as 12 wpi demonstrating the acutely oncogenic nature of this ovine betaretrovirus.

Full-length genome sequence analysis of enzootic nasal tumor virus reveals an unusually high degree of genetic stability

Enzootic nasal tumor virus (ENTV) is a betaretrovirus of sheep (ENTV-1) and goats (ENTV-2) associated with neoplastic transformation of epithelial cells of the ethmoid turbinate. Confirmation of the role of ENTV in the pathogenesis of enzootic nasal adenocarcinoma (ENA) has yet to be resolved due to the lack of an infectious molecular clone and the inability to culture the virus. Very little is known about the prevalence of this disease, particularly in North America, and only one full-length sequence is available for each of ENTV-1 and ENTV-2. In order to understand the molecular evolution of ENTV-1, the full-length genome sequence of ten ENTV-1 proviruses derived from clinical samples of ENA isolated from conventionally reared sheep in Canada and the United States was determined. The North American ENTV-1 (ENTV-1(NA)) genomes shared greater than 96% sequence identity with the European ENTV-1 sequence (ENTV-1(EU)). Most of the amino acid differences were found in Orf-x, which in the corresponding ENTV-1(EU) genome is truncated by 44 amino acids. Apart from Orf-x, the long terminal repeat (LTR) is where the majority of differences between ENTV-1(NA) and ENTV-1(EU) reside. Overall, there was an unusually high degree of amino acid conservation among the isolates suggesting that ENTV-1 is under stabilizing selection and K(a)/K(s) ratios calculated for each of the viral genes support this hypothesis. The unusually high degree of genetic stability of the ENTV-1 genome enabled us to develop a hemi-nested PCR assay for detection of ENTV-1 in clinical samples. Additionally, multiple nasal tumor cell clones were established and while most had lost the provirus by passage 5; one polyclonal line retained the provirus and attempts are being made to culture these cells. These tumor cells, the first of their kind, may provide a system for studying ENTV-1 in vitro. This work represents an important step in the study of ENTV and sets the foundation for the construction of an infectious molecular clone of ENTV-1.

Descriptive study of enzootic nasal adenocarcinoma in goats in southwestern China

This is the first report on enzootic nasal adenocarcinoma (ENA) in goats (Nanjiang Yellow goats and Jianyang Big-ear Black goats) in southwestern China. The clinical, histological and ultrastructural features of ENA in goats were described. From July 2007 to May 2009, 21 cases of ENA in goats, from 6 months to 8 years old, were diagnosed solely in one big herd. Clinically, the affected goats showed nasal discharge, facial swelling, sneezing, stertorous breathing and weight loss. Tumours that originated from the ethmoid area of the nasal cavity were unilateral (18/21) or bilateral (3/21). All tumours were classified as low grade adenocarcinomas by histopathological examination and were displayed a combination of tubular and papillary growth. No metastases were detected in regional lymph nodes, brain or other organs. Ultrastructurally, virus-like particles with an average diameter between 80 and 110 nm were observed in 5/7 examined tumours.

Enzootic nasal adenocarcinoma of sheep and goats

Enzootic nasal adenocarcinoma is a contagious tumour of the mucosal nasal glands affecting young adult sheep or goats. The disease occurs naturally in all continents except Australia and New Zealand. Clinical signs include continuous nasal discharge, respiratory distress, exophthalmos and skull deformations. The tumour is classified histologically as a low-grade adenocarcinoma. Nasal glands of both respiratory and olfactory muosal glands seem to be the origin of the neoplasia. It has been experimentally transmitted in sheep and goats using either tumour extracts or concentrated nasal fluids. Two distinct retroviruses are implicated in the aetiology of the neoplasia one in sheep (ONAV) and one in goats (CNAV). We suggest that jaagsiekte sheep retrovirus (JSRV), ONAV, CNAV, and their endogenous counterparts represent a unique family of retroviruses. The similarities between these viruses suggests that any control strategies, including vaccination, may be appropriate to both diseases. The differences, however, represent a unique resource for delineating the function of individual regions of the virus. It is intriguing that whilst ONAV and CNAV appear to be as different to each other as they are to JSRV, that they have very similar disease pathologies, distinct from that of OPA. Additionally, all three exogenous viruses manage to avoid instigating any apparent immune response. Whether this is indeed a result of tolerance induced by the endogenous counterparts or whether the viruses themselves have unique immunosuppressive properties will be an important finding.

Envelope-induced cell transformation by ovine betaretroviruses

Ovine betaretroviruses include Jaagsiekte sheep retrovirus (JSRV) and enzootic nasal tumor virus (ENTV). JSRV and ENTV represent a unique class of oncogenic retroviruses that induce tumors of the respiratory tract. JSRV and ENTV are highly related but induce different diseases. Expression of the JSRV envelope (Env) induces transformation of rodent fibroblasts in vitro and phosphorylation of Akt, a central player in the phosphatidylinositol 3-kinase (PI-3K)/Akt signal transduction pathway. However, little information is available on the molecular biology of ENTV. In this study, we initially assessed whether the ENTV Env has the same properties as the homologous JSRV protein. We performed entry and interference assays using retroviral vectors pseudotyped with either the JSRV or the ENTV Env and sheep choroid plexus cells, choroid plexus cells stably expressing the JSRV Env protein, human 293T cells, mouse NIH 3T3 cells, or NIH 3T3 cells expressing human hyaluronidase 2 (HYAL2), the cellular receptor for JSRV. The results obtained indicated that ENTV and JSRV share the same receptor in sheep cells and that they can use human HYAL2 as a cellular receptor in mouse cells. The ENTV Env induces transformation of rodent fibroblasts in vitro. As with the JSRV Env, the tyrosine at position 590 is critical for ENTV Env-induced cell transformation, and Akt is phosphorylated in ENTV Env-transformed cells but not in the parental cell lines. Thus, ovine betaretroviruses share a common mechanism of cell transformation. We further investigated the relevance of Akt activation in cells transformed by ovine betaretroviruses. A PI-3K inhibitor blocked Akt phosphorylation in JSRV Env-transformed cells, suggesting a possible involvement of PI-3K in JSRV and ENTV Env-induced cell transformation. In addition, phosphorylated Akt was detected in a cell line derived from a lung tumor of a sheep with naturally occurring ovine pulmonary adenocarcinoma.

Mechanism of cell entry and transformation by enzootic nasal tumor virus

Enzootic nasal tumor virus (ENTV) induces nasal epithelial cancer in infected sheep, but it is a simple retrovirus lacking a known oncogene. ENTV is closely related to jaagsiekte sheep retrovirus (JSRV), which also causes cancer in sheep but in the epithelial cells of the lower airways and alveoli. Here we show that as with JSRV, the envelope (Env) protein of ENTV can transform cultured cells and thus is likely to be responsible for oncogenesis in animals. In addition, the ENTV Env protein mediates virus entry using the same receptor as does JSRV Env, the candidate tumor suppressor Hyal2. However, ENTV Env mediates entry into cells from a more restricted range of species than does JSRV, and based on this finding we have identified amino acid regions in the Env proteins that are important for virus entry. Also, because ENTV does not efficiently use human Hyal2 as a receptor, we cloned the ovine Hyal2 cDNA and show that the encoded protein functions as an efficient receptor for both ENTV and JSRV. In summary, although ENTV and JSRV use the same cell surface receptor for cell entry and apparently transform cells by the same mechanism, they induce cancer in different tissues of infected sheep, indicating that oncogenesis is regulated at some other level. The transcriptional regulatory elements in these viruses are quite different, indicating that tissue-specific oncogenesis is likely regulated at the level of viral gene expression.

Origin of enzootic intranasal tumor in the goat (Capra hircus): a glycohistochemical approach

Enzootic intranasal tumor (EIT) appears glandular in type and has recently been classified as an adenocarcinoma of low malignancy. The aim of this study was to characterize the secretion of surface glycoconjugates (GCs) in EIT and in normal respiratory and olfactory mucosae of the goat by means of conventional and lectin histochemistry, in order to shed light on the histogenesis of EIT. Morphologic and ultrastructural investigations showed two growth types of EIT: i.e., tubular and papillary patterns. Conventional histochemistry revealed the presence of neutral and carboxylated GCs in the olfactory glands and in the tubular part of EIT, as well neutral and sulphated GCs in the respiratory glands and in the papillary part of EIT, suggesting that the papillary pattern tumor arises from the respiratory glands, whereas the tubular portion of EIT arises from the olfactory glands. Lectin histochemistry gave further information on the expressed GCs.

Lack of a specific immune response against a recombinant capsid protein of Jaagsiekte sheep retrovirus in sheep and goats naturally affected by enzootic nasal tumour or sheep pulmonary adenomatosis

Enzootic nasal tumour (ENT) and sheep pulmonary adenomatosis (SPA) are two contagious adenocarcinomas of the respiratory tract of sheep and goats. Both diseases are associated with related, but distinct, type-D-retroviruses (ENTV and JSRV respectively). No evidence of circulating antibodies has been described in animals affected by either ENT or SPA using antigens from natural sources. We evaluated the usefulness of a recombinant JSRV capsid protein (JSRV-CA) as antigen to study the antibody responses of animals naturally affected by ENT or SPA, using immunoblotting. Positive reactions were detected in the sera of both affected and unaffected sheep and goats. The reactivity was abolished completely by absorption with the GST fusion partner but not by JSRV-CA, suggesting that it was not specific. The results support prior observations indicating that sheep and goats infected by JSRV and ENTV do not develop specific humoral responses to these retroviruses.

Sheep pulmonary adenomatosis: a unique model of retrovirus-associated lung cancer

Sheep pulmonary adenomatosis (SPA) is a contagious bronchiolo-alveolar carcinoma of sheep associated with an exogenous type D/B retrovirus known as jaagsiekte sheep retrovirus (JSRV). SPA represents a unique model for lung cancer, and studies on its aetiopathogenesis can provide further insight into the mechanisms of epithelial neoplasms.

Retrovirus-associated neoplasms of the respiratory system of sheep and goats. Ovine pulmonary carcinoma and enzootic nasal tumor

As retrovirus-induced neoplasms of the respiratory epithelium of sheep and goats, OPC and ENT rank as economically important diseases in many countries of the world. They are also important as models of retroviral carcinogenesis of the secretory epithelium of the respiratory system. Control of both diseases is dependent on development and application of sensitive and specific assays for identification of carrier animals infected with the causative agents of these diseases. Recent progress in characterization of type D/B retroviruses associated with the diseases and development of new reagents for the immunologic or molecular detection of antiviral antibodies, viral proteins, or viral nucleic acids bodes well for improved control or prevention of these diseases.

PCR-based detection and partial characterization of a retrovirus associated with contagious intranasal tumors of sheep and goats

A type D-related retrovirus has been demonstrated in enzootic nasal tumors (ENTs) of sheep and goats. This retrovirus, ENT virus (ENTV), has antigenic cross-reactivity with the jaagsiekte sheep retrovirus (JSRV), which is associated with a contagious lung tumor of sheep (sheep pulmonary adenomatosis). Here, we present the first report of nucleic acid sequence from ENTV which confirms, at the nucleic acid level, that this retrovirus is related to JSRV yet apparently distinct from it. Reverse transcription-PCR followed by restriction enzyme digestion specifically identified ENTV. By this technique, ENTV was demonstrated exclusively in tumor tissues and exudates of animals with ENT. Thus, there is a unique and consistent association between ENT and the retrovirus, just as there is between JSRV and sheep pulmonary adenomatosis. This gives further weight to the hypothesis that these retroviruses are the etiologic agents of the tumors.

Retroviral aetiopathogenesis of ovine pulmonary carcinoma: a critical appraisal

Although it has long been thought that a retrovirus is the responsible agent for ovine pulmonary carcinoma (OPC), identification of a replicative viral agent has proven difficult. Recently, the genome of a new retrovirus, jaagsiekte sheep retrovirus (JSRV), found in the lung-wash of affected sheep lung, has been cloned and sequenced; characterization of this virus and its consistent presence in tumor cells argue for its role as the aetiologic agent of OPC. Analysis of the nucleic acid sequence of the JSRV genome, suggests a new class of retrovirus, one that is chimeric according to the morphological classification scheme used for retroviruses. The genome of this virus does not appear to contain an oncogene, and the mechanism by which it causes disease is still unknown. The presence of multiple copies of endogenous retroviruses related to JSRV in DNA of OPC-affected and unaffected sheep further complicates investigation of oncogenesis in OPC. This review examines the evidence for a retrovirus as the causative agent for OPC, with particular emphasis on the viruses studied to date. The significance of endogenous JSRV-related sequences is considered. The mechanisms by which a retrovirus such as JSRV might induce lung tumours in sheep, and which of these are most likely, are discussed in light of these developments, as are the prospects for new means of diagnosis and treatment of this disease.