IMMUNOGENICITY OF HILDA LIF EITHER IN A SOLUBLE OR IN A MEMBRANE-ANCHORED FORM EXPRESSED IN-VIVO BY RECOMBINANT VACCINIA VIRUSES

Insertion of various cDNAs in the genome of the vaccinia virus (VV) en ables the in vivo and in vitro study of the functional role and/or the immunogenicity of the virally encoded recombinant proteins. We have p repared a recombinant VV expressing the cDNA of the human cytokine HIL DA/LIF (human interleukin for DA cells/leukaemia inhibitory factor), a nd used this virus to immunize mice against this protein, which is ver y homologous to its murine counterpart (almost-equal-to 80% homology). We also constructed and expressed by the same system a chimeric gene encoding the HILDA/LIF protein fused to the 37 COOH-terminal amino-aci ds of the human decay accelerating factor (DAF). This sequence proved to be sufficient for the targeting of the fusion protein to the cell m embrane, where it is linked to the phosphatidylinositols. Both recombi nant VVs induced cytokine-specific antibodies in mice as analysed with an ELISA where the recombinant HILDA/LIF was plastic-coated and a cyt ofluorometric assay where the LIF-DAF molecule was present at the cell surface of stably transfected P815. In the latter case HILDA/LIF rema ined biologically active suggesting that it was expressed in its nativ e form. The LIF-DAF fusion protein was found to exhibit a better capac ity to elicit an antibody response against the native form of the cyto kine as detected in cytofluorometric assays. Whatever the recombinant virus used to immunize the mice, the MoAbs obtained were positive eith er in the ELISA or in the cytofluorometric assays but one, which sugge sted that the plastic coating induced a conformational change of HILDA /LIF.