HIGH-LEVEL EXPRESSION OF BIOLOGICALLY-ACTIVE, SOLUBLE FORMS OF ICAM-1IN A NOVEL MAMMALIAN-CELL EXPRESSION SYSTEM

LFA-1/ICAM-1 interaction is important in facilitating a number of cell ular events including antigen-specific T-cell activation and leukocyte transendothelial migration. We are interested in defining residues an d contact sites that mediate ICAM-1 interaction with the integrin rece ptor, LFA-1. To provide sufficient material to facilitate study of the interaction of this ligand-receptor pair, we have developed a new hig h-level mammalian-cell expression system based on the use of the herpe s simplex virus (HSV) VP16 transactivator and the HSV IE175 promoter t o direct expression of foreign genes in BHK cells. In this system, the gene of interest is expressed as a fusion protein with a carboxyl ter minal decapeptide tail to aid in identification, quantitation, and aff inity purification of recombinant protein. This system allowed rapid g eneration of cell lines producing high levels of levels of soluble pro teins corresponding to the full-length extracellular (sICAM(453)) and the amino terminal two immunoglobulin domains (sICAM(185)) of ICAM-1. Both sICAM(453) and sICAM(185) were biologically active and were purif ied in a single step from conditioned media by antibody affinity chrom atography. (C) 1994 Academic Press, Inc.