PROLIFERATING CELL NUCLEAR ANTIGEN EXPRESSION IN SHEEP INFECTED WITH BOVINE LEUKEMIA-VIRUS

Proliferating cell nuclear antigen (PCNA) or cyclin (C), a major nucle ar protein, has been shown to be associated with human leukemia and ma lignancies. PCNA protein was quantitated in this study, in lymphocytes from bovine leukemia virus (BLV) infected and non-infected sheep, usi ng two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) and s ilver staining. The PCNA mean levels in lymphocytes of BLV-infected sh eep (27 months post-infection) was significantly (P < 0.001) higher th an in the lymphocytes of the non-infected sheep. The mean of PCNA leve ls in lymphocytes of sheep, 21 days after BLV infection, showed a two- fold increase compared with the non-infected sheep. Phytohemagglutinin (PHA) (3 days) treatment of lymphocytes from the non-infected and fro m the BLV-infected sheep resulted in a significant (P < 0.01) increase in the mean of PCNA levels only in the non-infected sheep. The mean l ymphocyte counts of the BLV-infected sheep were not significantly diff erent from the mean counts of the non-infected sheep at the time of ly mphocyte protein analysis. Thus, these findings showed, similar to hum an leukemia and malignancies, that high levels of PCNA were found in l ymphocytes from BLV-infected sheep compared with those from the non-in fected sheep, and this was independent of high cell count. Our results also suggest that PCNA protein may play a role in the process of lymp hoid transformation as a result of BLV infection of sheep.