Differential efficiency of expression of humanized antibodies in transienttransfected mammalian cells

Transient transfections are commonly used in the preliminary assessment of comparative levels of expression, biologic activity, and affinity of recomb inant antibody molecules, but apparent expression levels can vary up to 200 -fold. We have compared the expression levels of various humanized antibodi es and "mixed and matched" heavy and light chains in transiently transfecte d CHO cells using replicate, small-scale transfections within single or rep licate experiments to control for variation in transfection efficiency. We have found that each antibody is expressed with a characteristic efficiency , determined by a combination of factors including the level of light-chain synthesis, heavy- and light-chain "compatibility," and CDR/framework inter actions to provide a compact Fv module.