Vet. Res. 37 (2006) 133-144
DOI: 10.1051/vetres:2005048

Maedi-visna virus infection of ovine mammary epithelial cells

Rosa Bolea^a, Eva Monleón^a, Librado Carrasco^b, Antonia Vargas^a, Damián de Andrés^c, Beatriz Amorena^c, Juan José Badiola^a and Lluís Luján<sup>a

a</sup>  Department of Animal Pathology, University of Zaragoza, Veterinary Faculty, Miguel Servet 177, 50013 Zaragoza, Spain
^b  Department of Anatomy and Comparative Pathology, University of Córdoba, Veterinary Faculty, Campus de Rabanales, 14014 Córdoba, Spain
^c  Instituto de Agrobiotecnología y Recursos Naturales, Spanish Council for Scientific Research (C.S.I.C.), Public University of Navarra 31192, Mutilva Baja, Spain

(Received 10 March 2005; accepted 29 August 2005; published online 13 December 2005)

Abstract - The aim of this work was to perform a complete study of maedi-visna virus (MVV) infected mammary glands of naturally-infected sheep, and to determine if cells other than macrophages undergo a productive viral infection in this organ. Fifteen seropositive and two seronegative ewes were selected from MVV-infected flocks on the basis of clinical indurative mastitis and three sheep from an MVV-free flock. Within the mammary gland, MVV-positive cells were located by immunohistochemistry in the stroma and the epithelial alveolar barrier, most likely the ovine mammary epithelial cells (OMEC) of the acini. In situ hybridization confirmed these findings. Ultrastructural studies showed the presence of lentivirus-like particles budding off the cell surface in the alveolar barrier and also free in the acinar lumen. The presence of mammary histopathological lesions and MVV together with clear indications of productive infection (demonstration of a cytopathic effect in OMEC cultures and infection of co-cultures) were observed in the 15 seropositive and one of the seronegative sheep from the infected flock. These findings demonstrate that the OMEC were infected in vivo and probably underwent productive infection when studied ex-vivo. The OMEC of MVV-free sheep, which had subsequently been infected in vitro with MVV, also showed productive infection when challenged in vitro, confirming the replication of MVV in OMEC in vitro. The presence of MVV-infected OMEC in the mammary gland from infected animals, the productive infection in these OMEC and the release of lentiviral particles to the acinar lumen may have relevance in the pathogenesis and transmission of MVV infection.

Key words: maedi-visna / mammary gland / epithelial cells / indurative mastitis / ovine

Corresponding author: Rosa Bolea rbolea@unizar.es

© INRA, EDP Sciences 2005