<i>Granulibacter bethesdensis</i>, a Pathogen from Patients with Chronic Granulomatous Disease, Produces a Penta-Acylated Hypostimulatory Glycero-d-talo-oct-2-ulosonic Acid–Lipid A Glycolipid (Ko-Lipid A)

• Main Authors: Artur Muszyński, Kol A. Zarember, Christian Heiss, Joseph Shiloach, Lars J. Berg, John Audley, Arina Kozyr, David E. Greenberg, Steven M. Holland, Harry L. Malech, Parastoo Azadi, Russell W. Carlson, John I. Gallin
• Format: Article
• Language: English
• Published: MDPI AG 2021-03-01
• Series: International Journal of Molecular Sciences
• Subjects: lipopolysaccharide; lipid A; Gram-negative pathogen, immunodeficiency
• Online Access: https://www.mdpi.com/1422-0067/22/7/3303

<i>Granulibacter bethesdensis</i> can infect patients with chronic granulomatous disease, an immunodeficiency caused by reduced phagocyte NADPH oxidase function. Intact <i>G. bethesdensis</i> (<i>Gb</i>) is hypostimulatory compared to <i>Escherichia coli</i>, i.e., cytokine production in human blood requires 10–100 times more <i>G. bethesdensis</i> CFU/mL than <i>E. coli</i>. To better understand the pathogenicity of <i>G. bethesdensis</i>, we isolated its lipopolysaccharide (<i>Gb</i>LPS) and characterized its lipid A. Unlike with typical <i>Enterobacteriaceae</i>, the release of presumptive Gb lipid A from its LPS required a strong acid. NMR and mass spectrometry demonstrated that the carbohydrate portion of the isolated glycolipid consists of α-Man<i>p</i>-(1→4)-β-Glc<i>p</i>N3N-(1→6)-α-Glc<i>p</i>N-(1⇿1)-α-Glc<i>p</i>A tetra-saccharide substituted with five acyl chains: the amide-linked N-3′ 14:0(3-OH), N-2′ 16:0(3-O16:0), and N-2 18:0(3-OH) and the ester-linked O-3 14:0(3-OH) and 16:0. The identification of glycero-d-talo-oct-2-ulosonic acid (Ko) as the first constituent of the core region of the LPS that is covalently attached to GlcpN3N of the lipid backbone may account for the acid resistance of <i>Gb</i>LPS. In addition, the presence of Ko and only five acyl chains may explain the >10-fold lower proinflammatory potency of <i>Gb</i>Ko–lipidA compared to <i>E. coli</i> lipid A, as measured by cytokine induction in human blood. These unusual structural properties of the <i>G.bethesdensis</i> Ko–lipid A glycolipid likely contribute to immune evasion during pathogenesis and resistance to antimicrobial peptides.