Development of a mAb library for the diagnosis of melioidosis.

Burkholderia pseudomallei, the causative agent of melioidosis, produces a high molecular weight capsular polysaccharide (CPS) comprised of an unbranched homopolymer of 1,3-linked 2-O-acetyl-6-deoxy-β-D-mannoheptopyranose residues. Our laboratory has previously produced a CPS specific IgG3 monoclonal antibody (mAb), 3C5, and determined that it is able to provide passive protection in a murine model of pulmonary melioidosis. In addition, the mAb was used to detect shed CPS in melioidosis patient samples and was successfully incorporated into a prototype Active Melioidosis DetectTM Lateral Flow Immunoassay (AMD LFI) through a collaboration with our laboratory and InBios International, Inc. While a successful prototype was produced using mAb 3C5, background issues attributed to IgG3 self association lead us to pursue making additional antibodies of alternate isotypes. We have recently isolated several murine IgG1 mAbs targeting CPS by immunizing BALB/c mice with a CPS glycoconjugate. The new library of mAbs show a range in CPS binding affinities, with one mAb in particular, 4C4, having a considerably higher affinity for CPS compared to our previous IgG3 mAb. An updated LFI incorporating a new CPS-specific IgG1 displays high CPS sensitivity with greatly reduced background signal, highlighting its potential as a sensitive and specific rapid diagnostic for melioidosis.