PRODUCTION AND CHARACTERIZATION OF A SET OF MOUSE-HUMAN CHIMERIC IMMUNOGLOBULIN-G (IGG) SUBCLASS AND IGA MONOCLONAL-ANTIBODIES WITH IDENTICAL VARIABLE REGIONS SPECIFIC FOR PSEUDOMONAS-AERUGINOSA SEROGROUP O6 LIPOPOLYSACCHARIDE

The heavy- and light-chain variable regions from a murine monoclonal a ntibody that recognize Pseudomonas aeruginosa serogroup O6 lipopolysac charide (LPS) were used to generate a series of chimeric mouse-human m onoclonal antibodies with identical variable regions. The murine varia ble-region gene segments were cloned into an immunoglobulin (Ig) cDNA expression vector that contained the human kappa light-chain and IgG1 constant regions. The IgG1 heavy-chain constant region was then replac ed with the human IgG2, IgG3, IgG4, or IgA1 heavy-chain constant regio n. The five different expression vectors were transfected into Chinese hamster ovary cells for antibody production. The chimeric antibodies exhibited immunoreactivity and affinity similar to that of the parenta l murine IgG antibody toward whole cells of a serogroup O6 strain. In vitro complement deposition assays demonstrated that the chimeric IgG4 and IgA antibodies did not mediate the deposition of complement compo nent C3 onto the surface of either purified LPS or whole bacteria. The chimeric IgG1 and IgG3 antibodies were similar in their ability to de posit C3 onto the surface of both bacteria and LPS, while IgG2 antibod y was more effective at depositing C3 onto the surface of bacteria tha n onto purified LPS. The pattern of opsonophagocytic activity of the c himeric monoclonal antibodies was similar to that of complement deposi tion onto bacterial cells in that the chimeric IgG1 and IgG3 had the h ighest opsonic activity. Although IgG2 deposited more C3 onto the bact erial surface than did IgG4 or IgA, all three of these isotypes had lo w opsonic activity against the serogroup O6 target strain. This series of related antibodies will help reveal functional differences in effi cacy among protective antibodies to P. aeruginosa and will be critical for defining the optimal formulation of either a vaccine for active i mmunization or a polyclonal intravenous IgG or monoclonal antibody coc ktail for passive immunotherapy.