RETROVIRUS-LIKE ACTIVITY IN AN IMMUNOSUPPRESSED DOG - PATHOLOGICAL AND IMMUNOLOGICAL FINDINGS

A putative retrovirus was isolated from a dog with a severe, acquired immunodeficiency-like syndrome. The haematological abnormalities and i mmunological deficiencies included anaemia, leucopenia (lymphopenia an d neutropenia), thrombocytopenia, decreased humoral immunity, and inef fective T-cell responses in-vitro. The necropsy findings included gene ralized lymphoid depletion, severe bone marrow hypoplasia, plasmacytic infiltrates in lymphoid and non-lymphoid organs, and severe secondary infections. Supernates of peripheral blood mononuclear cell cultures from the affected dog contained an agent with manganese-dependent reve rse transcriptase (RT) activity that sedimented at a density of 1.122 g/ml. RT activity was also found post-mortem in extracts prepared from the bone marrow, lymph nodes, and small intestine. The lymph nodes an d small intestine expressed a 3.8 kb mRNA that was recognized by a bov ine leukaemia virus (BLV) pol DNA probe by Northern blotting. DNA isol ated from the lymph nodes and small intestine from the affected dog sh owed distinct band patterns by Southern analysis, suggesting an exogen ous retrovirus. The retrovirus could be propagated in normal canine pe ripheral blood mononuclear cells or short-term canine lymphocyte cell lines in-vitro, and was cytopathogenic for cells of canine, but not hu man, origin. These results suggest the existence of a pathogenic canin e retrovirus capable of producing disease of the type associated with retroviruses in other species.