Cholesterol glucosylation promotes immune evasion by Helicobacter pylori

Abstract

Helicobacter pylori infection causes gastric pathology such as ulcer and carcinoma. Because H. pylori is auxotrophic for cholesterol, we have explored the assimilation of cholesterol by H. pylori in infection. Here we show that H. pylori follows a cholesterol gradient and extracts the lipid from plasma membranes of epithelial cells for subsequent glucosylation. Excessive cholesterol promotes phagocytosis of H. pylori by antigen-presenting cells, such as macrophages and dendritic cells, and enhances antigen-specific T cell responses. A cholesterol-rich diet during bacterial challenge leads to T cell-dependent reduction of the H. pylori burden in the stomach. Intrinsic alpha-glucosylation of cholesterol abrogates phagocytosis of H. pylori and subsequent T cell activation. We identify the gene hp0421 as encoding the enzyme cholesterol-alpha-glucosyltransferase responsible for cholesterol glucosylation. Generation of knockout mutants lacking hp0421 corroborates the importance of cholesteryl glucosides for escaping phagocytosis, T cell activation and bacterial clearance in vivo. Thus, we propose a mechanism regulating the host-pathogen interaction whereby glucosylation of a lipid tips the scales towards immune evasion or response.

A supplemented soft agar chemotaxis assay demonstrates the Helicobacter pylori chemotactic response to zinc and nickel

“…Urea is one such chemoattractant (Cerda et al, 2003;Mizote et al, 1997;Worku et al, 2004), although H. pylori mucosal localization is not affected in vivo when the urea/ammonium gradient is altered (Schreiber et al, 2004). Other reported attractants include bicarbonate (Cerda et al, 2003;Mizote et al, 1997), NaCl (Mizote et al, 1997), cholesterol (Wunder et al, 2006), and the amino acids aspartate, serine and arginine (Cerda et al, 2003). H. pylori is repelled by NiCl 2 (Cerda et al, 2003), low pH (Croxen et al, 2006;Howitt et al, 2011;Rader et al, 2011) and autoinducer-2 (Rader et al, 2011), the latter two via the TlpB chemoreceptor.…”

Colonize, evade, flourish

“…Cholesterol affords the bacterium a number of advantages during the infection process; this steroid hormone has been shown to promote colonization, innate immune evasion, and antibiotic resistance. 80,81 It may also reinforce the bacterial membrane, promoting resistance to toxic host compounds. 82,83 Wunder et al 80 delivered a seminal set of data that helped define the role of membrane-incorporated cholesterol in promoting pathogenesis.…”

“…80,81 It may also reinforce the bacterial membrane, promoting resistance to toxic host compounds. 82,83 Wunder et al 80 delivered a seminal set of data that helped define the role of membrane-incorporated cholesterol in promoting pathogenesis. They find that H. pylori can sense and move toward cholesterol in its environment at levels as low as 250 μM, extract it from the cholesterol-rich lipid rafts of epithelial cells, glucosylate it by the action of a cholesterol-α-glucosyltransferase, Hp0421, and integrate it into the membrane.…”

“…They find that H. pylori can sense and move toward cholesterol in its environment at levels as low as 250 μM, extract it from the cholesterol-rich lipid rafts of epithelial cells, glucosylate it by the action of a cholesterol-α-glucosyltransferase, Hp0421, and integrate it into the membrane. 80 In the absence of Hp0421, H. pylori is more susceptible to phagocytosis and therefore triggers a strong T cell-mediated immune response. 84,85 Conversely, wild-type bacteria are phagocytosed to a limited extent and generate a weak immune response.…”

“…Further, high concentrations of cholesterol encourage phagocytosis, suggesting that cholesterol is steadily converted to cholesteryl-α-glucoside and this is required to evade phagocytosis. 80 Mice infected with the hp0421 mutant strain were able to rapidly clear the infection, suggesting that α-glucosylation of cholesterol is required for survival in vivo via evasion of phagocytosis and T-cell activation.…”