Helicobacter pylori glycan biosynthesis modulates host immune cell recognition and response

IntroductionThe pathogenic bacterium Helicobacter pylori has evolved glycan-mediated mechanisms to evade host immune defenses. This study tests the hypothesis that genetic disruption of H. pylori glycan biosynthesis alters immune recognition and response by human gastric epithelial cells and monocyte-derived dendritic cells.MethodsTo test this hypothesis, human cell lines were challenged with wildtype H. pylori alongside an array of H. pylori glycosylation mutants. The relative levels of immune response were measured via immature dendritic cell maturation and cytokine secretion.ResultsOur findings indicate that disruption of lipopolysaccharide biosynthesis diminishes gastric cytokine production, without disrupting dendritic cell recognition and activation. In contrast, variable immune responses were observed in protein glycosylation mutants which prompted us to test the hypothesis that phase variation plays a role in regulating bacterial cell surface glycosylation and subsequent immune recognition. Lewis antigen presentation does not correlate with extent of immune response, while the extent of lipopolysaccharide O-antigen elaboration does.DiscussionThe outcomes of this study demonstrate that H. pylori glycans modulate the host immune response. This work provides a foundation to pursue immune-based tailoring of bacterial glycans towards modulating immunogenicity of microbial pathogens

Effects of PCSK9 Inhibition With Alirocumab on Lipoprotein Metabolism in Healthy Humans

BACKGROUND: Alirocumab, a monoclonal antibody to proprotein convertase subtilisin/kexin type 9 (PCSK9), lowers plasma low-density lipoprotein (LDL) cholesterol and apolipoprotein B100 (apoB). Although studies in mice and cells have identified increased hepatic LDL receptors as the basis for LDL lowering by PCSK9 inhibitors, there have been no human studies characterizing the effects of PCSK9 inhibitors on lipoprotein metabolism. In particular, it is not known whether inhibition of PCSK9 has any effects on very low-density lipoprotein or intermediate-density lipoprotein (IDL) metabolism. Inhibition of PCSK9 also results in reductions of plasma lipoprotein (a) levels. The regulation of plasma Lp(a) levels, including the role of LDL receptors in the clearance of Lp(a), is poorly defined, and no mechanistic studies of the Lp(a) lowering by alirocumab in humans have been published to date. METHODS: Eighteen (10 F, 8 mol/L) participants completed a placebo-controlled, 2-period study. They received 2 doses of placebo, 2 weeks apart, followed by 5 doses of 150 mg of alirocumab, 2 weeks apart. At the end of each period, fractional clearance rates (FCRs) and production rates (PRs) of apoB and apo(a) were determined. In 10 participants, postprandial triglycerides and apoB48 levels were measured. RESULTS: Alirocumab reduced ultracentrifugally isolated LDL-C by 55.1%, LDL-apoB by 56.3%, and plasma Lp(a) by 18.7%. The fall in LDL-apoB was caused by an 80.4% increase in LDL-apoB FCR and a 23.9% reduction in LDL-apoB PR. The latter was due to a 46.1% increase in IDL-apoB FCR coupled with a 27.2% decrease in conversion of IDL to LDL. The FCR of apo(a) tended to increase (24.6%) without any change in apo(a) PR. Alirocumab had no effects on FCRs or PRs of very low-density lipoproteins-apoB and very low-density lipoproteins triglycerides or on postprandial plasma triglycerides or apoB48 concentrations. CONCLUSIONS: Alirocumab decreased LDL-C and LDL-apoB by increasing IDL- and LDL-apoB FCRs and decreasing LDL-apoB PR. These results are consistent with increases in LDL receptors available to clear IDL and LDL from blood during PCSK9 inhibition. The increase in apo(a) FCR during alirocumab treatment suggests that increased LDL receptors may also play a role in the reduction of plasma Lp(a). CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01959971

Investigating the Impact of \u3ci\u3eHelicobacter pylori\u3c/i\u3e Glycan Biosynthesis on Host Immune Response

Helicobacter pylori is a pathogenic bacterium that utilizes its surface glycans to modulate its interactions with host cells. H. pylori incorporates Lewis blood group tetrasaccharide antigens at the terminus of its lipopolysaccharide to mimic mammalian glycans of a host cell and glycosylates specialized proteins to facilitate its adhesion to the epithelium. This study tests the hypothesis that genetic disruption of glycan biosynthesis will negate the modulatory effects of H. pylori’s glycans and reduce the bacterium’s pathogenicity. Namely, we test the hypothesis that phase variable expression of certain carbohydrate epitopes within H. pylori’s glycocalyx accounts for variable immune response to different glycosylation mutant strains. We additionally test the hypothesis that disrupted glycan biosynthesis will inhibit effective bacterial cell adhesion. These hypotheses were tested by investigating H. pylori’s phase variable glycan architecture in parallel with the induced immune response and adhesion of different glycosylation mutant strains compared to wildtype H. pylori. Our results suggest that LPS elaboration, rather than Lewis Y antigen expression, correlates with the induced immune response of gastric epithelial cells and dendritic cells. We additionally conclude that adhesion of H. pylori to gastric epithelial cells is mediated by the glycan biosynthetic pathway

Relationship Between Low‐Density Lipoprotein Cholesterol, Free Proprotein Convertase Subtilisin/Kexin Type 9, and Alirocumab Levels After Different Lipid‐Lowering Strategies

Background: Alirocumab undergoes target‐mediated clearance via binding of proprotein convertase subtilisin/kexin type 9 (PCSK9). Statins increase PCSK9 levels; the effects of nonstatin lipid‐lowering therapies are unclear. Every‐4‐weeks dosing of alirocumab may be appropriate for some patients in absence of background statin but is not yet approved. Methods and Results: Low‐density lipoprotein cholesterol (LDL‐C), PCSK9, and alirocumab levels were assessed in subjects (LDL‐C >130 mg/dL, n=24/group) after a 4‐week run‐in taking oral ezetimibe, fenofibrate, or ezetimibe placebo, when alirocumab 150 mg every 4 weeks (days 1, 29, and 57) was added. Maximal mean LDL‐C reductions from day −1 baseline (prealirocumab) occurred on day 71 in all groups: alirocumab plus placebo, 47.4%; alirocumab plus ezetimibe, 56.6%; and alirocumab plus fenofibrate, 54.3%. LDL‐C reductions were sustained through day 85 with alirocumab plus placebo (47.0%); the duration of effect was slightly diminished at day 85 versus day 71 with ezetimibe (49.6%) or fenofibrate combinations (43.2%). Free PCSK9 concentrations were lowest at day 71 in all groups, then increased over time; by day 85, free PCSK9 concentrations were higher, and alirocumab levels lower, with alirocumab plus fenofibrate, and to a lesser extent alirocumab plus ezetimibe, versus alirocumab plus placebo. Conclusions: Alirocumab 150 mg every 4 weeks produced maximal LDL‐C reductions of 47% in combination with placebo and 54% to 57% in combination with ezetimibe or fenofibrate. The oral lipid‐lowering therapies appear to increase PCSK9 levels, leading to increased alirocumab clearance. Although the duration of effect was modestly diminished with alirocumab plus ezetimibe/fenofibrate versus placebo, the effect was less than observed in trials with background statins, and it would not preclude the use of alirocumab every 4 weeks in patients taking these nonstatin lipid‐lowering therapies concomitantly. Clinical Trial Registration URL: http://www.Clinicaltrials.gov. Unique identifier: NCT01723735

SuppTable_Params – Supplemental material for A Quantitative Systems Pharmacology Platform to Investigate the Impact of Alirocumab and Cholesterol-Lowering Therapies on Lipid Profiles and Plaque Characteristics

<p>Supplemental material, SuppTable_Params for A Quantitative Systems Pharmacology Platform to Investigate the Impact of Alirocumab and Cholesterol-Lowering Therapies on Lipid Profiles and Plaque Characteristics by Jeffrey E Ming, Ruth E Abrams, Derek W Bartlett, Mengdi Tao, Tu Nguyen, Howard Surks, Katherine Kudrycki, Ananth Kadambi, Christina M Friedrich, Nassim Djebli, Britta Goebel, Alex Koszycki, Meera Varshnaya, Joseph Elassal, Poulabi Banerjee, William J Sasiela, Michael J Reed, Jeffrey S Barrett and Karim Azer in Gene Regulation and Systems Biology</p

Equations_v2 – Supplemental material for A Quantitative Systems Pharmacology Platform to Investigate the Impact of Alirocumab and Cholesterol-Lowering Therapies on Lipid Profiles and Plaque Characteristics

<p>Supplemental material, Equations_v2 for A Quantitative Systems Pharmacology Platform to Investigate the Impact of Alirocumab and Cholesterol-Lowering Therapies on Lipid Profiles and Plaque Characteristics by Jeffrey E Ming, Ruth E Abrams, Derek W Bartlett, Mengdi Tao, Tu Nguyen, Howard Surks, Katherine Kudrycki, Ananth Kadambi, Christina M Friedrich, Nassim Djebli, Britta Goebel, Alex Koszycki, Meera Varshnaya, Joseph Elassal, Poulabi Banerjee, William J Sasiela, Michael J Reed, Jeffrey S Barrett and Karim Azer in Gene Regulation and Systems Biology</p