Divergence of binding, signaling, and biological responses to recombinant human hybrid IFN

Three human IFN-alpha hybrids, HY-1 [IFN-alpha 21a(1-75)/alpha 2c(76-165)], HY-2 [IFN-alpha 21a(1-95)/alpha 2c(96-165)], and HY-3 [IFN-alpha 2c(1-95)/ alpha 21a(96-166)], were constructed, cloned, and er;pressed, The hybrids h ad comparable specific antiviral activities on Madin-Darby bovine kidney (M DBK)(3) cells but exhibited very different antiproliferative and binding pr operties on human Daudi and WISH cells and primary human lymphocytes. Our d ata suggest that a portion of the N-terminal region of the molecule is impo rtant for interaction with components involved in binding of IFN-alpha 2b w hile the C-terminal portion of IPN is critical for antiproliferative activi ty, A domain affecting the antiproliferative activity was found within the C-terminal region from amino acid residues 75-166, The signal transduction properties of HY-2 and HY-3 were evaluated by ER ISA and RNase protection a ssays, Both HY-2 and HY-3 induced activation of STAT1 and 2, However, HY-2 exhibited essentially no antiproliferative effects at concentrations that a ctivated STAT1 and 2. Additionally, at concentrations where no antiprolifer ative activity was seen, HY-2 induced a variety of IFN-responsive genes to the same degree as HY-3. RNase protection assays also indicate that, at con centrations where no antiproliferative activity was seen for HY-2, this con struct retained the ability to induce a variety of IFN-inducible genes. The se data suggest that the antiproliferative response may not be solely direc ted by the activation of the STAT1 and STAT2 pathway in the cells tested.