A polyreactive human anti-lipid A monoclonal antibody having cross reactivity to polysaccharide portions of Pseudomonas aeruginosa lipopolysaccharides.

A hybridoma cell line producing a human anti-lipid A monoclonal antibody (mAb), FKF-IF3 (IgM (k)) was obtained by cell fusion of Epstein-Barr virus-transformed cells and mouse myeloma. The mAb bound to not only Gram-negative bacterial lipid A, but also to polysaccharide portions of Pseudomonas aeruginosa lipopolysaccharides (LPS). The mAb seemed to recognize two distinct regions of P. aeruginosa LPS other than lipid A, namely the outer core regions of some serotype strains and the O-polysaccharide region of serotype A strains. The mAb cross-reacted with N-acetyl-beta-glucosamine-conjugated bovine serum albumin, N-acetyl-beta-galactosamine-conjugated bovine serum albumin, myosin and actin, but not with other autoantigens such as ss- and ds-DNA, cardiolipin and glycosaminoglycans. The mAb conferred protective activity against a mouse pseudomonal infection model. The evidence suggested that the mAb was a naturally occurring polyspecific antibody that participated in defense against pseudomonal infections.