EFFECT OF BOVINE HERPESVIRUS-1 ON EXPRESSION OF INTERLEUKIN-2 RECEPTORS AND EFFECT OF INTERLEUKIN-12 ON LYMPHOCYTE-PROLIFERATION

Expression of the interleukin-2 receptor alpha chain (IL-2R alpha) by peripheral blood mononuclear cells (PBMC) from Holstein calves, both e xperimentally-infected with bovine herpesvirus-l (BHV-1) and controls, was measured by flow cytometry. Expression of IL-2R alpha was 35% and 23% higher in infected calves than controls, on days 2 and 3 postinfe ction (PI), respectively. Concurrent with this increase in IL-2R alpha expression, a significant decrease (P < 0.001) was observed in the PH A-induced proliferative responses of PBMC from infected compared with control calves. In vitro treatment with recombinant human (rhu) IL-12 enhanced PHA-induced proliferative responses of PBMC from both infecte d and control calves. This rhuIL-12 enhancement of mitogen-induced pro liferative responses was significant (P < 0.001) in infected calves on day 2 PI and was sufficient to abrogate the decrease observed due to BHV-1 infection. Since the expression of the beta and gamma chains of IL-2R was not measured it is difficult to speculate as to the status o f high affinity receptor expression during BHV-1 infection. However re sults of the present study suggest that the decrease in proliferative responses observed during infection may not be due to a decrease in IL -2R cu expression but may possibly be hue to a selective down-regulati on of signal transduction through IL-2R and/or by modulation of the ex pression of other cytokines involved in lymphocyte activation and prol iferation.