PATHOGENESIS OF LYMPHOID INTERSTITIAL PNEUMONIA IN NATURAL AND EXPERIMENTAL OVINE LENTIVIRUS INFECTION

Ovine lentivirus (OvLV), as a member of the lentivirinae subfamily of Retroviridae, shares morphological, genomic, and cytopathic features w ith human immunodeficiency virus (HIV). Although OvLV infection does n ot induce profound immune deficiency in sheep, it has many similaritie s with HIV infection. such as the capacity to infect macrophages, unde rgo antigenic variation in vivo, and induce slow progressive diseases involving the pulmonary, lymphoid, and central nervous systems. Studie s of the pathogenesis of disease in sheep naturally or experimentally infected by OvLV are providing clues to the pathogenesis of HIV infect ion, including the significance of viral load, the emergence of cytopa thic variants, the mechanisms and significance of viral antigenic vari ation, and viral neutralization, and mechanisms of lymphoproliferation and tissue destruction induced by the virus. Preliminary evidence sug gests that infection by other microbial agents, including Mycoplasma s pecies, may play a cofactor role in the pathogenesis of lentivirus-ass ociated lymphoid interstitial pneumonia in sheep, but further studies are required to address this issue.