Virological markers in cerebrospinal fluid are predictive of ovine lentivirus-associated subclinical encephalomyelitis.

Encephalomyelitis is a sequela to ovine lentivirus (OvLV) and human immunodeficiency virus infections. Examination of autopsy tissue from 38 naturally infected asymptomatic sheep showed that 7 (18%) had subclinical neurological lesions characterized by perivascular and periventricular infiltrates of lymphocytes and histiocytes in the leptomeninges, cerebral white matter, choroid plexus, and/or cervical spinal cord. Intralesional histiocytes were shown to contain lentiviral capsid proteins or RNA. Infectious virus (2/7), viral proteins (4/7), and antiviral antibody (5/7) were only detected in cerebrospinal fluid (CSF) from animals with central nervous system (CNS) lesions associated with OvLV infection, suggesting that such virologic markers in CSF, when used concurrently, are predictive of pathologic changes specific to the CNS.

Ovine lentivirus expression and disease. Virus replication, but not entry, is restricted to macrophages of specific tissues.

To better define the relationship between lentivirus infection and lymphoproliferative or inflammatory disease, we studied postmortem specimens of 38 sheep naturally infected with ovine lentivirus (OvLV) and with different clinical manifestations of OvLV-associated disease. Immunohistochemistry, in situ hybridization, and virus isolation were used to localize viral protein, viral RNA, and infectious virus to specific cells and tissues. Viral protein or infectious virus was found in cells morphologically and histochemically compatible with macrophages (M phi s), but only in lung, bone marrow, mammary gland, lymph node, spleen, synovium, brain, and spinal cord, frequently in association with lymphocyte infiltrates. In contrast, viral RNA was found in a variety of cell types, including epithelium, M phi s, and M phi-like cells, and in a wider range of tissues, with or without OvLV-associated lesions. In summary, these findings suggest that in vivo: 1), OvLV can enter a variety of cell types, 2), productive infection is restricted to cells of M phi lineage, and 3), cells expressing viral proteins are limited to specific tissues, those associated with OvLV-induced diseases.

Raccoon poxvirus rabies virus glycoprotein recombinant vaccine in sheep.

Twenty sheep were divided into groups and inoculated by various routes with recombinant raccoon poxvirus expressing the CVS rabies virus glycoprotein (rRCNV-G) or with raccoon poxvirus (RCNV). The apparent innocuous pathologic responses to each virus coupled with development of high levels of rabies virus neutralizing antibodies in animals vaccinated with rRCNV-G intradermally or intramuscularly suggested that the recombinant is effective and that RCNV would be a suitable substrate for further development of sheep vaccines. Poor antibody response to rRCNV-G given orally implied that it would be relatively harmless if inadvertently ingested by sheep. Virus transmission between vaccinated and sentinel sheep was not observed or detected serologically.