Lipooligosaccharide (LOS) (LOS)

Lipooligosaccharide (LOS) is a major glycolipid component of the outer membrane of various Gram-negative bacteria, including Neisseria meningitidis, Neisseria gonorrhoeae, and Haemophilus influenzae (PMID: 11544341). Structurally, LOS differs from lipopolysaccharide (LPS) by the absence of the repeating O-antigen subunits, consisting only of a lipid A anchor and a core oligosaccharide (PubChem CID: 11970143). It serves as a primary virulence factor, contributing to bacterial survival by maintaining membrane stability and facilitating attachment to host mucosal surfaces (Microbiology Spectrum, 2019). LOS is a potent inducer of the innate immune system, signaling through the Toll-like receptor 4 (TLR4) complex to trigger the release of pro-inflammatory cytokines (Journal of Endotoxin Research). In clinical contexts, LOS is associated with the pathogenesis of septicemia and meningitis, and its structural mimicry of human gangliosides can lead to post-infectious autoimmune conditions like Guillain-Barré syndrome (Nature Reviews Microbiology). Therapeutic strategies include the use of cationic peptides like Polymyxin B to neutralize its endotoxic effects and the development of glycoconjugate vaccines targeting conserved LOS epitopes (PubMed).

Other names

LOSLow-molecular-weight lipopolysaccharideShort-chain lipopolysaccharideLipid A-core oligosaccharide

Polymyxins bind to the Lipid A component of LOS through electrostatic and hydrophobic interactions, neutralizing its endotoxic activity and disrupting the bacterial outer membrane (StatPearls). Experimental antagonists like Eritoran competitively inhibit the TLR4/MD-2 receptor complex to block LOS-induced inflammatory signaling (PubMed). Vaccines induce bactericidal antibodies that target conserved LOS epitopes to facilitate opsonophagocytosis or complement-mediated killing (PMID: 11544341).