[Lentivirus expression at the moment of lambing modifies the leukocyte number in the milk of multiparous ewes]. / L'expression des lentivirus au moment de l'agnelage modifie la formule leucocytaire du lait de brebis multipares.

Lambing in small ruminants is a time of high lentivirus expression; infected mononuclear phagocytes are frequent in colostrum and milk. We have studied mammary secretions in 5 multiparous ewes and shown that infected macrophages in milk are accompanied by an augmentation of leucocyte number. The lymphocyte CD8 subpopulation increased in size simultaneously with the onset of infected cell excretion. The udder infection by coagulase negative staphylococci did not modulate milk lymphocyte content. Although infected cell excretion was restricted to one half of the udder, virus-specific lesions were found in both udder halves. Milk leukocytes changes are a marker of infected macrophage presence; they do not control lentivirus spread.

[Development of lymphocyte subsets in milk from ewes excreting Maedi virus]. / Evolution des sous-populations lymphocytaires dans le lait de brebis au moment de l'excrétion du virus Maedi.

Milk is the most important route of lentivirus spread in sheep and goat. Blood and milk cell populations were characterised with specific monoclonal antibody at lambing time in 4 primiparous seropositive ewes. Two of the ewes (3/4 half udders) produced milk with infected cells. The cell number/ml was always higher in milk and blood from virus-producing animals. In ewes which spread infected macrophages CD8 lymphocyte number was increased in blood and milk. Serological tests are able to detect infected animals but virus production is reflected immediately by an increase of CD8 lymphocytes in milk.

[Expression of visna-maedi virus in the mammary secretions of a seropositive ewe during gestation and then an artificial induction of lactation]. / Expression du virus Visna-Maedi dans les sécrétions mammaires d'une brebis séropositive lors d'une gestation puis d'une induction artificielle de lactation.

Lentiviruses in small ruminants are specially harboured in the mononuclear phagocyte lineage. The virus expression in macrophages is strictly correlated with physiological events of the reproduction life of the host. In a pregnant ewe, Visna-Maedi seropositive, we cultivated infectious cells from mammary secretions, colostrum and milk. In the same animal, a hormonally induced artificial lactation produced the same increase of infectious macrophages in mammary secretions. The virus is more easily obtained by coculture of milk macrophages when the number of macrophages is higher in mammary secretions.