Reverse transcriptase activity in a case of ovine lymphoblastic leukaemia

Area of Science:

• Veterinary Pathology
• Oncology
• Virology

Background:

• Investigating the potential viral etiology of lymphoblastic leukaemia in sheep.
• Examining post-mortem tissues from a leukaemic sheep for specific retroviral markers.

Observation:

• Cultured bone marrow and lymph node cells from the leukaemic sheep released particles with densities of 1.16 and 1.21 g/ml.
• Cell-free supernatants exhibited poly rC-oligo dG templated reverse transcriptase (RT) activity.
• No similar particles or RT activity were detected in tissues from normal sheep.

Findings:

• Retroviral reverse transcriptase (RT) activity and specific particle densities were identified in leukaemic sheep tissues.
• Electron microscopy did not reveal retrovirus-like particles, despite RT activity.
• In vitro transmission studies showed low-efficiency transfer of RT activity to bovine kidney and mink lung cells, but not to sheep choroid plexus or lamb trachea cells.

Implications:

• Suggests a potential retroviral involvement in ovine lymphoblastic leukaemia.
• Highlights the utility of biochemical assays (RT activity) in detecting retroviral agents when morphology is unclear.
• Provides a basis for further research into the specific retrovirus and its pathogenesis in sheep.