Construction of an Expression Vector Containing Mouse-Rat Chimeric Genes Encoding a Therapeutic Antibody against CD81

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CD81 belongs to thetetraspanin family of cell-surface proteins, which contain four transmembrane domains and two outer-membrane loops. CD81 has been shown to be up-regulated in synoviocytes in rheumatoid arthritis (RA) and to promote synoviolin expression in the progression of RA. Recently, we showed that a small interfering RNA (CD81siRNA) targeting the gene encoding CD81 ameliorates arthritis in collagen-induced arthritic (CIA) rats. CD81 siRNA also decreased the expression of TNF-α in SW982 cells. Additionally, we established hybridoma cell lines producing monoclonal antibodies (MAbs) against CD81 and demonstrated that some of these MAbs impaired the proliferation of C6 glioma cells. Here, we report cloning of the cDNA encoding one such MAb (H chain and L chain) from hybridoma cells and construction of mouse-rat chimeric genes for expression of the chimeric antibody. This chimeric antibody, as expressed by CHO cells, bound to CD81 at the target’s outer-membrane loop (LEL).