COMPARISON OF BINDING-SPECIFICITY AND THE FUNCTION OF 2 HUMAN-IGM ANTI-LIPID-A MONOCLONAL-ANTIBODIES

The interactions of two anti-lipid A monoclonal antibodies (mAb)-HA-1A and SdJ5-1.17.15-with their antigenic sites on lipid A, were compared using a dot-blot assay and lipid A structural analogues, as well as l ipid A-high-density lipoprotein (HDL) complexes. The reactivities of b oth mAb were affected by the type of far, acid side chains and by the phosphate group on the glucosamine residue Il; however, the interactio n of SdJ5-1.17.15 appeared to be more markedly affected by the fatty a cid side chains. A determination of the biological significance of the se antigenic differences was made. Human peripheral blood mononuclear cells (hPBMC) challenged with Escherichia coli 055:B5 lipopolysacchari de (LPS) pre-incubated with SdJ5-1.17.15 released significantly less t umor necrosis factor-a (TNF-alpha) and interleukin-1 beta (IL-1 beta), compared to hPBMC exposed to vehicle preincubated LPS. HA-1A did not attenuate the in vitro release of either cytokine. The ability of both mAb to neutralize the in vivo toxicity of LPS was also evaluated. Rat s administered E. coli 055:B5 pre-incubated with SdJ5-1.17.15 had a si gnificantly reduced 24-hr mortality rate compared to vehicle controls. HA-1A did not attenuate the in vivo mortality rate. Therefore, the re activity of anti-lipid A mAb with the antigen is preferentially affect ed by different residues on the lipid A moiety. Thus, the differences in biological activity seen with SdJ5-1.17.15 and HA-1A may be due in part to differences in their recognition sites on lipid A. (C) 1995 Wi ley-Liss, Inc.