EFFECTS OF CO-EXPRESSING CHAPERONE BIP ON FUNCTIONAL ANTIBODY-PRODUCTION IN THE BACULOVIRUS SYSTEM

The assembly pathway of the insect cell Spodoptera frugiperda (Sf-9) w as engineered to include expression of the murine chaperone immunoglob ulin heavy chain binding protein (BiP) using the baculovirus vector. T he impact of BiP coexpression on the production and secretion of funct ional and soluble recombinant immunoglobulin IgG levels was evaluated. Recombinant BiP was found to associate specifically with immunoglobul ins in immunoprecipitation studies. Coinfection of insect cells with a BiP-containing baculovirus and baculoviruses coding for two different murine IgG proteins increased intracellular functional antibody activ ity levels substantially above the levels observed in the absence of B iP. Soluble intracellular immunoglobulin levels were found to increase as well. However, secreted functional antibody levels did not increas e significantly. Also, degradation of heavy chain immunoglobulin in in sect cells was indicated by the accumulation of lower molecular weight immunoglobulins at 4 days postinfection. Coexpression of light chains reduced the level of these lower molecular weight immunoglobulins whi le BiP coexpression led to enhanced levels. These findings suggest tha t coexpressed BiP can increase intracellular soluble and functional an tibody yields but that secretion in the baculovirus-insect cell system must be limited at some post-translational step. (C) 1994 Academic Pr ess, Inc.