Endotoxin and Mammalian Host Responses During Experimental Disease

Endotoxin is an integral component of the outer membrane of Gram-negative bacteria and a prime example of unique and highly conserved bacterial surface molecules that engage with the innate immune system of the mammalian host via pattern recognition receptors on a range of host cells. The results of this interaction, which may be beneficial or detrimental to the development and welfare of the host, are reviewed, focusing on the different sensitivities and consequences in a range of hosts of experimental exposure to endotoxin, the disease outcomes and recent developments in our understanding of the mechanisms involved.

Single chain antibodies specific for fatty acids derived from a semi-synthetic phage display library

The biological activities of many acylated molecules are lipid dependent. Lipids, however, are poorly immunogenic or non-immunogenic. We employed a phage display semi-synthetic human antibody library to isolate anti-lipid antibodies. Selection was done against methyl palmitate, a 16 carbon aliphatic chain, and a major component of bacterial glycolipids and lipoproteins in animal cells. The selected single chain variable fragment (scFv) bound specifically to a 16 carbon aliphatic chain and to a lesser extent to a 14 or 18 carbon aliphatic chain and poorly to either 12, 22 or 8 carbon aliphatic chains. Furthermore, the scFv prevented micelle formation of lipoteichoic acid from Gram-positive bacteria; inhibited lipopolysaccharide-induced tumor necrosis factor alpha release in mononuclear cells; bound to hydrophobic bacterial surfaces, especially those of Gram-positive bacteria, and bound to Lck, a mammalian palmitated lipoprotein. Our data suggest that the phage antibody library can be successfully employed to obtain human anti-aliphatic scFv human antibody fragment with potential therapeutic applications in neutralizing the deleterious effects of bacterial toxins as well as in structure--function analysis of lipoproteins in animal cells.

Anti-lipid A monoclonal antibody centoxin (HA-1A) binds to a wide variety of hydrophobic ligands

This note describes the binding specificities of four lipid A monoclonal antibodies (MAbs) including Centoxin (HA-1A); these MAbs display similar binding properties. MAbs reacted with lipid A and heat-killed smooth bacteria, whereas no reactivity was observed with smooth lipopolysaccharide (LPS). Immunoblotting of bacterial extracts separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the MAbs bound to many polypeptide bands including the molecular weight markers. Denaturation of bovine serum albumin (BSA) by boiling or dithiothreitol treatment unmasked antibody epitopes. In addition, binding both to a hydrophobic aliphatic C12 chain covalently coupled to BSA and to single-stranded DNA was observed. The polyreactivity of these clones is most likely mediated by a preferential reactivity with hydrophobic molecular patches.