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.

[Pathological Diagnoses and Whole-genome Sequence Analyses of the Jaagsiekte Sheep Retrovirus in Xinjiang, China]

To carry out pathologic diagnoses and whole-genome sequence analyses of the Jaagsiekte sheep retrovirus (JSRV) in Xinjiang, China, we first observed sheep suspected to have the JSRV. Then, the extracted virus suspension was observed by transmission electron microscopy (TEM). Total RNAs from lungs of JSRV-infected sheep were extracted and reverse-transcribed using a cDNA synthesis kit. Six pairs of primers were designed according to the exogenous reference virus strain (AF105220). Reverse transcription-polymerase chain reaction was carried out from JSRV-infected tissue, and the whole genome of the JSRV sequenced. Our results showed: flow of nasal fluid ("wheelbarrow test"); different sizes of adenoma lesions in the lungs; papillary hyperplasia of alveolar epithelial cells; alveolar cavity filled with macrophages; dissolute nuclei in central lesions. TEM revealed JSRV particles with a diameter of 88 nm to 125. 4 nm. The full-length of the viral genome sequence was 7456 bp. BLAST analyses showed nucleotide homology of 96% and 95% compared with that of the representative strain from the USA (AF105220) and UK (AF357971). Nucleotide homology was 89.8% and 89.9% compared with the endogenous Jaagsiekte sheep retrovirus, Inner Mongolia strain (DQ838493) and USA strain (EF680300). The specific pathogenic amino-acid sequence "YXXM" was found in the TM district, similar to the exogenous JSRV: this gene has been reported to be oncogenic. This is the first report of the complete genomic sequence of the exogenous JSRV from Xinjiang, and could lay the foundation for study of the biological characteristics and pathogenic mechanisms of the pulmonary adenomatosis virus in sheep.

Diagnosis and phylogenetic analysis of ovine pulmonary adenocarcinoma in China

Ovine pulmonary adenocarcinoma (OPA) is a lung tumor of sheep caused by jaagsiekte sheep retrovirus (JSRV). OPA is common in sheep, and it is most commonly observed in China. Without preventative vaccines and serological diagnostic tools for assay of OPA, identification of JSRV based on reverse transcription polymerase chain reaction (RT-PCR) is very important for prevention and control measures for OPA in practice management. In this study, the diagnosis of OPA was made from analysis of clinical signs, pathological observations, JSRV-like particle discovery, and RT-PCR of the target env gene. The phylogenetic analysis showed that the China Shandong (SD) strain studied in this article belonged to exogenous JSRV, and it was very similar to 92k3, which was isolated from sheep in the Kenya (Y18305). The current study reported a severe outbreak of OPA in Shandong Province, China. The observations could offer a comparative view of the env gene of JSRV.

Endogenous retroviruses related to jaagsiekte sheep retrovirus

Ovine betaretroviruses consist of exogenous viruses [jaagsiekte sheep retrovirus (JSRV) and enzootic nasal tumor virus, (ENTV)] associated with neoplastic diseases of the respiratory tract and 15-20 endogenous viruses (enJSRV) stably integrated in the ovine and caprine genome. Phylogenetic analysis of this group of retroviruses suggests that the enJSRV can be considered as 'modern' endogenous retroviruses with active, exogenous counterparts. Sequence analysis of JSRV, ENTV and enJSRV suggests that enJSRV do not directly contribute to the pathogenesis of ovine pulmonary adenocarcinoma (OPA) or enzootic nasal tumor through large-scale recombination events, but small-scale recombination or complementation of gene function cannot be excluded; experiments involving enJSRV-free sheep, which have not been found, would be needed to investigate this possibility. Evidence of expression of enJSRV structural proteins in tissues of the reproductive tract and lung implies that they do not have a primary role in disease. However, experimental exploitation of exogenous/endogenous retrovirus sequence differences by producing chimeras has been useful in establishing the determinants of JSRV Env-induced transformation. Even if enJSRV do not have a direct role in OPA, their expression during ontogeny or in neonatal life may impact the likelihood of exogenous JSRV infection and disease outcome via the induction of immunological tolerance. Aside from any role in disease, enJSRV loci may serve as useful genetic markers in the sheep and their frequent expression in the reproductive tract of the ewe may portend an important physiologic role in sheep.