Cloning and expression of porcine CD163: Its use for characterization of monoclonal antibodies to porcine CD163 and development of an ELISA to measure soluble CD163 in biological fluids

Abstract

CD163 is a member of the family of proteins with scavenger receptor cysteine-rich domains, whose expression is restricted to monocytes and macrophages. It functions as a receptor for haemoglobin/haptoglobin complexes and it has also been implicated in the regulation of inflammatory processes. Treatment of monocytes/macrophages with phorbol esters, LPS or cross-linking of Fc gamma receptors, causes shedding of CD163 from cell surface by a protease-dependent mechanism. The level of soluble CD163 (sCD163) in serum and other body fluids has been considered a useful marker of macrophage activation. In addition, porcine CD163 has been shown to play a role in the infection of monocytes/macrophages by the African swine fever virus. The porcine CD163 cDNA has been cloned, and expressed in transfected CHO cells. Clones of CHO cells stably expressing porcine CD163 have been used for the characterization of three new mAbs against porcine CD163. Using two of these mAbs, that bind to different epitopes on CD163 molecule, a sandwich enzyme-linked immunoassay (ELISA) has been developed to measure levels of sCD163 in porcine sera and biological fluids. The assay was calibrated using lysates of CD163 transfectants, showing a sensitivity of 105 cells mL-1, that allowed to detect sCD163 in sera and in culture supernatants of activated alveolar macrophages. This assay can be a useful method of monitoring the degree of activation of macrophages in a variety of inflammatory and infectious diseases of swine.