A novel Escherichia coli lipid A mutant that produces an antiinflammatory lipopolysaccharide.

Abstract

A unique screen was used to identify mutations in Escherichia coli lipid A biosynthesis that result in a decreased ability to stimulate E-selectin expression by human endothelial cells. A mutation was identified in the msb B gene of E. coli that resulted in lipopolysaccharide (LPS) that lacks the myristoyl fatty acid moiety of the lipid A. Unlike all previously reported lipid A mutants, the msb B mutant was not conditionally lethal for growth. Viable cells or purified LPS from an msb B mutant had a 1000-10,000-fold reduction in the ability to stimulate E-selectin production by human endothelial cells and TNF ␣ production by adherent monocytes. The cloned msb B gene was able to functionally complement the msb B mutant, restoring both the LPS to its native composition and the ability of the strain to stimulate immune cells. Nonmyristoylated LPS acted as an antagonist for E-selectin expression when mixed with LPS obtained from the parental strain. These studies demonstrate a significant role for the myristate component of LPS in immune cell activation and antagonism. In addition, the msb B mutant allowed us to directly examine the crucial role that the lipid A structure plays when viable bacteria are presented to host defense cells. ( J. Clin. Invest. 1996. 97:359-365.)

Induction of TLR Tolerance in Human Macrophages by Adiponectin: Does LPS Play a Role?

“…(C) Cell viability as assessed by MTT. (D) Cells were maintained for 16 h in the presence of either media alone, Adpn at 10 lg ⁄ ml or LPS at 30 pg ⁄ ml in the presence or absence of 1 lg ⁄ ml antagonist LPS [34]. Induction of TNF-a was assayed by ELISA in the culture supernatants.…”

Function of Escherichia coli MsbA, an Essential ABC Family Transporter, in Lipid A and Phospholipid Biosynthesis

“…The msbB mutation (not shown in Fig. 4) blocks the last acylation of lipid A biosynthesis, resulting in the accumulation of the penta-acylated species (19,23). Five acyl chains on lipid A are sufficient to support growth (19,23).…”

“…Instead, msbA encodes an ABC family transporter with high amino acid sequence similarity to mammalian Mdr proteins (21). msbA is an essential gene (21), whereas msbB is not (20,23). When introduced on low copy plasmids, msbA complements most of the htrB mutant phenotypes, such as the morphological alterations, the overproduction of phospholipids, and the inability to grow above 32°C (21).…”

A killed, genetically engineered derivative of a wild-type extraintestinal pathogenic E. coli strain is a vaccine candidate

“…Third, adjuvants have the potential to enhance the immune response. Fourth, although lipidA toxicity should be less of an issue with mucosal immunization, if necessary, constructs can be generated in which the bioactive properties of lipidA have been minimized [56]. Lastly, if certain epitopes/proteins are shown in future studies to be critical in conferring protection against ExPEC infection, they can be over-expressed in the genetically engineered background that results in the optimal antibody response.…”