Exogenous Small Ruminant Betaretrovirus Envelope Protein Is Detected in Draining Lymph Nodes in Contagious Respiratory Tumors of Sheep and Goats

Abstract

Contagious respiratory tumors of sheep and goats are epithelial neoplasms of the lung and nasal cavities. They are associated with oncogenic betaretroviruses known as jaagsiekte sheep retrovirus and enzootic nasal tumor retrovirus of sheep and goats. We investigated the presence of the envelope protein (ENV) of these retroviruses in retropharyngeal and mediastinal lymph nodes using a specific monoclonal antibody by immunohistochemistry methods, single-labeled or combined with ovine B or T lymphocytes or macrophage cell markers. Samples of lymph nodes, fixed in formalin and zinc fixative, were obtained from paraffin-embedded material. Four groups of samples were used: 24 natural cases of ovine pulmonary adenocarcinoma (OPA), 13 of enzootic nasal adenocarcinoma of sheep (ENAS), 19 of enzootic nasal adenocarcinoma of goats (ENAG), and 14 control samples. ENV was detected by single labeling in cortical lymphoid follicles. Six of 24 OPA samples were positive and only in those from sheep with extensive neoplasia. Immunolabeling was detected in 5/13 ENAS and 10/19 ENAG samples. Positive labeling was found either in the intercellular spaces, membranes, or cytoplasm of cells in follicles. Control samples were not correspondingly labeled. Double immunohistochemistry demonstrated co-labeling of ENV and CD21 (B cells and follicular dendritic cells) in all samples, CD14 (macrophage) in OPA samples, and Pax-5 (B cells) in ENAG samples, but not with CD8 or CD4 (T lymphocytes). These results demonstrate the presence of betaretrovirus ENV proteins in nontumor cells in regional lymph nodes in sheep and goats with contagious respiratory tumors.

Adenocarcinoma pulmonar ovino en México

“…The primary target cells for JSRV in the lung are the bronchiolar Club cells (formerly Clara cells) and the pneumonocytes Type II in the alveolar wall (1,9,13) . This virus also infects B-lymphocytes, T-lymphocytes (CD4+ and CD8+), macrophages and has been detected in peripheral blood monocytes (9,11,14) .…”

“…Histologic features are those of a well-differentiated lepidic or papillary carcinoma (3,12,15) . OPA requires laboratory confirmation by identifying JSRV or associated proteins in affected tissues by immunolabelling or PCR (4,14,16) . It was described the gross, microscopic and immunohistochemical changes in the lungs of a sheep infected with JSRV, which evolved to OPA in Colima, Mexico.…”

“…Infection with JSRV is distributed globally in all continents, with the notable exception of Australia and New Zealand (9,13,14) . In some countries, JSRV infection is endemic and affects 80 % of the ovine population, although only 4-30 % of the infected sheep go onto developing OPA (8,17) .…”