Phenotypic and ultrastructural characteristics of bronchoalveolar lavage cells of lentivirus-infected lambs treated with recombinant ovine IFN-tau

Ovine lentivirus (OvLV) belongs to the family Retroviridae and closely rese mbles the human immunodeficiency virus (HIV). Pulmonary lesions in OvLV-inf ected sheep consist of lymphoid interstitial pneumonia (LIP) and lymphocyti c alveolitis. Similar pulmonary lesions occur in up to 40% of HIV-infected children and in some adults with AIDS. Interferon-tau (IFN-tau), a type I I FN, is produced by trophectoderm of ruminant conceptuses and is the pregnan cy recognition signal in these species. To evaluate changes in phenotypes o f bronchoalveolar lavage (BAL) cells of OvLV-infected lambs treated with re combinant ovine IFN-tau (rOvIFN-tau), 24 lambs were randomly allocated to o ne of four groups (n = 6 per group): 1, no virus + placebo (NVP); 2, no vir us + rOvIFN-tau (NVI); 3, virus + placebo (VP); 4, virus + rOvIFN-tau (VI). The BAL cells from 3 lambs in each group were labeled with monoclonal anti bodies (mAb) to cell surface markers at 16 weeks of treatment, and cells fr om the remaining 3 lambs in each group were labeled with mAb at 34 weeks of treatment. After labeling, BAL cells were analyzed by flow cytometry. The morphology of BAL cells from all experimental lambs was examined by transmi ssion electron microscopy (TEM). At week 16, no differences in the relative proportions of BAL cell phenotypes were detected among the experimental gr oups. At week 34, VI lambs had higher proportions of CD8(+), gamma delta (), MHC class II+, and L-selectin (LS+) BAL cells compared with VP lambs. Hi gher proportions of CD14(+) and CD44(+) cells were found in VP lambs compar ed with NVP lambs at 34 weeks. OvLV-like particles were detected only in br onchoalveolar macrophages of VP lambs. In this study, rOvIFN-tau increased the proportions of primary antiviral gamma delta (+) and CD8(+) immune cell s in OvLV-infected lambs. This may represent a cellular mechanism to explai n the antiviral and therapeutic efficacy of this cytokine, in addition to i ts direct antiviral effect. However, because the actual number of cells lab eled with mAb CD8 was low and some subsets of gamma delta cells may coexpre ss the CD8 marker, further studies are necessary to better define the role of rOvIFN-tau in the modulation of these cells in vivo.