Synthesis and expression in Escherichia coli of DNA encoding the murine λ1 chain of a monoclonal antibody specific for Salmonella serotype B O-antigen

A 658 bp DNA sequence corresponding to the murine λ1 chain of a monoclonal antibody, Se 155-4, specific for the Salmonella serotype B O-antigen, was designed using Escherichia coli preferred codons and chemically synthesized by ligation of synthetic fragments into a linearized plasmid followed by transformation into E.coli. A synthetic signal peptide (ompA) was fused to express the L chain as a free polypeptide into the periplasm of E.coli cells. After isolation and purification, heterologous recombination of the E.coli L chain with mouse H chain gave an active antigen-binding protein. The activity was 15–20% when compared to protein created by an equivalent association of isolated natural mouse L and H chains as measured by a direct EIA assay. In inhibition experiments with the polysaccharide antigen, the two proteins showed identical titration curves and 50% inhibition points, indicating comparable KA values.