EFFECT OF RECOMBINANT BOVINE INTERLEUKIN-1-BETA ON VIRAL-BACTERIAL PNEUMONIA IN CATTLE

Bovine herpesvirus-1 (BHV-1) is an important pathogen of respiratory i nfections in cattle. Its continuing importance lies in its ability to predispose infected hosts to bacterial infections (e.g., Pasteurella h aemolytica). In this study we determined whether the immunoregulatory effects induced by recombinant bovine interleukin-1 (rbIL-1) could sti mulate appropriate host defense mechanisms to influence the course of BHV-1 and P. haemolytica infection in cattle. We first evaluated the e ffect of multiple doses (5 doses of 300 ng/kg) of rbIL-1 in normal cat tle. An increase in polymorphonuclear (PMN) cells, as well as monocyte s, in peripheral blood was observed during the course of IL-1 administ ration. In addition, the phagocytic activity of monocytes was increase d. Although the phagocytic and oxidative burst activities in PMN decre ased during the course of rbIL-1 treatment, no changes were observed i n the bactericidal capacity of these cells. Lymphocyte numbers in peri pheral blood remained unchanged; however, the functional activity of t hese cells, as measured by IFN-gamma production upon in vitro stimulat ion, was decreased. In the bovine respiratory disease model, multiple administration of IL-1 did not influence significantly the progression of BHV-1/P. haemolytica infection in cattle. Thus, our results demons trated that IL-1, although not therapeutically effective, could be adm inistered safely as an adjuvant, even during the course of BHV-1/P. ha emolytica infection.