CLONING AND EXPRESSION OF BOVINE AND PORCINE INTERLEUKIN-2 IN BACULOVIRUS AND ANALYSIS OF SPECIES CROSS-REACTIVITY

The cDNAs encoding bovine and porcine interleukin-2 (IL-2) have been e xpressed using the baculovirus Autographa californica nuclear polyhedr osis virus as a vector in insect cells. Insect cells infected with rec ombinant viruses secreted bovine and porcine IL-2 into the culture med ium, with biological activities for maintaining the proliferation of h omologous cells. When the activities of these two IL-2 proteins and co mmercially available human IL-2 were tested on heterologous cells diff erences were found. Recombinant bovine (rb)IL-2 only supported the gro wth of bovine lymphocytes and was not active on human, mouse or porcin e lymphocytes. Recombinant porcine (rp)IL-2 and recombinant human (rh) IL-2 supported the proliferation of human, bovine, porcine and murine cells. However, the proliferative response of human lymphocytes to rpI L-2 was only 50% of that seen with rhIL-2. Sequence differences at the predicted p55 and p75 contact binding sites may explain this.