Characteristics of a lipid preparation (lipid A) from Haemophilus influenzae type a lipopolysaccharide

Abstract

Mild hydrolysis of Haemophilus influenzae type a lipopolysaccharide by ion exchangers yielded a lipid A extracted by chloroform. It contained phosphorus, glucosamine, and fatty acids. Myristic, palmitic, 3-hydroxymyristic, and oleic acids and two other unidentified long-chain fatty acids were found. The free lipid A was not toxic for mice at doses of up to 50 mg/kg and did not provoke a Shwartzman reaction. The Limulus test activity was positive up to 10(-12) g/ml, but the pyrogenicity in rabbits was lower than with the original lipopolysaccharide. However, the lipid A did induced a mitogenic response and polyclonal B-cell activation in mouse spleen cell cultures. Complexing lipid A with bovine serum albumin gave a nontoxic preparation which lost these immunological activities. Immunochemical studies showed that the major reactive determinants of this lipid-protein complex were altered after such a linkage. Consequently, the nontoxic and mitogenic lipid A isolated from H. influenzae type a did not exhibit all of the classical activities of lipid A preparations.

In vitro immunological activities of the polysaccharide fraction from Haemophilus influenzae type a endotoxin

“…Trinitrophenyl (TNP)-substituted sheep erythrocytes, prepared according to Rittenberg and Pratt (18), were used as targets. Collected cells were counted in a Coulter Counter and the results were expressed as AFC per 106 collected cells (13). Gel filtration of PS IV and PS II on Sephadex G200 showed a single peak and confirmed their molecular weights.…”

Genomics, Transcriptomics, and Metabolomics Reveal That Minimal Modifications in the Host Are Crucial for the Compensatory Evolution of ColE1-Like Plasmids

“…The results suggest that an underlying biological process involving the myristic acid is selectively regulated upon the coevolution of H. influenzae with pB1000. Notably, lipopolysaccharide (LPS) modifications have been associated with a decreased susceptibility to phage predation ( 49 ), and myristoyl substitutions in the lipid A of H. influenzae have been described as a major lipid A residue ( 50 ), which is critical factor involved in the endotoxic activity of Gram-negative bacteria ( 51 ). This finding implies that further nongenomic and nontranscriptomic modifications mediate the plasmid-host coadaptation, whose consequences could even extend to the phage resistance and virulence of the bacteria.…”