Deficiency in the glycosyltransferase Gcnt1 increases susceptibility to tuberculosis through a mechanism involving neutrophils

Abstract

Modulation of immunity and disease by glycans is increasingly recognized. However, how host glycosylation shapes and is shaped by tuberculosis remains poorly understood. We show that deficiency in the glucosaminyl (N-acetyl) transferase 1 (Gcnt1), a key enzyme for core-2 O-glycans biosynthesis, drives susceptibility to Mycobacterium tuberculosis infection. The increased susceptibility of Gcnt1 deficient mice was characterized by extensive lung immune pathology, mechanistically related to neutrophils. Uninfected Gcnt1 deficient mice presented bone marrow, blood and lung neutrophilia, which further increased with infection. Blood neutrophilia required Gcnt1 deficiency in the hematopoietic compartment, relating with enhanced granulopoiesis, but normal cellular egress from the bone marrow. Interestingly, for the blood neutrophilia to translate into susceptibility to M. tuberculosis infection, Gnct1 deficiency in the stroma was also necessary. Complete Gcnt1 deficiency associated with increased lung expression of the neutrophil chemoattractant CXCL2. Lastly, we demonstrate that the transcript levels of various glycosyltransferase-encoding genes were altered in whole blood of active tuberculosis patients and that sialyl Lewis x, a glycan widely present in human neutrophils, was detected in the lung of tuberculosis patients. Our findings reveal a previously unappreciated link between Gcnt1, neutrophilia and susceptibility to M. tuberculosis infection, uncovering new players balancing the immune response in tuberculosis.

Transcriptome-wide Association Study of Circulating IgE Levels Identifies Novel Targets for Asthma and Allergic Diseases

“…Interestingly, a recent knockout study found that GCNT1 deficient mice have neutrophilia and increased susceptibility to tuberculosis infection. The increased susceptibility of GCNT1 deficient mice to infection was largely driven by exacerbated neutrophil counts, which led to lung lesions, inflammation, and other pathologic features in the lungs of affected mice 31 . This link between GCNT1 and neutrophilia is relevant to studying the regulation of IgE as other studies have shown elevated serum IgE levels to be associated with neutrophilic asthma 32 .…”

Mycobacterium tuberculosis Infection Up-Regulates Sialyl Lewis X Expression in the Lung Epithelium

“…Mice were infected with M. tuberculosis H37Rv or HN878 strains via aerosol route using an inhalation exposure system (Glas-Col), following previously published protocols [ 15 ]. A murine model of active TB mimicking human TB was used, as described in Kroesen et al [ 24 ].…”

“…infection (4 × 10 4 –2 × 10 5 CFU/mL per mouse) with M. tuberculosis H37Rv Pasteur strain. At the experimental time points (15, 30, 60 and 90 days post-infection), the lungs of infected animals were harvested and the bacterial load determined by CFU enumeration, as previously described [ 15 , 25 , 26 ]. The data is presented in Supplementary Figure S1 .…”

“…In the case of H. pylori , we showed that infection results in increased expression of sialylated Lewis antigens in the gastric epithelium, which are recognized by the bacterial sialic acid binding adhesin (SabA), contributing to a close contact with the gastric mucosal cells and a tighter fit of the infection load with proficient transfer of virulence factors [ 12 , 13 ]. As for M. tuberculosis , a pathogen that causes over 1.4 million deaths and over 10 million new cases of tuberculosis (TB) per year [ 14 ], we have recently described a link between O -glycans and susceptibility to infection [ 15 ]. Briefly, the deficiency of Gcnt1 , a key enzyme acting on the initial biosynthetic steps of the core-2 O -glycans, was associated with increased susceptibility to M. tuberculosis infection, characterized by augmented lung immune pathology, with both hematopoietic and non-hematopoietic compartments being crucial for this process [ 15 ].…”

“…As for M. tuberculosis , a pathogen that causes over 1.4 million deaths and over 10 million new cases of tuberculosis (TB) per year [ 14 ], we have recently described a link between O -glycans and susceptibility to infection [ 15 ]. Briefly, the deficiency of Gcnt1 , a key enzyme acting on the initial biosynthetic steps of the core-2 O -glycans, was associated with increased susceptibility to M. tuberculosis infection, characterized by augmented lung immune pathology, with both hematopoietic and non-hematopoietic compartments being crucial for this process [ 15 ]. Previous studies had shown that a combined deficiency in fucosyltransferases 4 and 7 in the mouse model led to accelerated death following M. tuberculosis infection, which was not caused by increased bacterial proliferation, nor by exacerbated tissue pathology [ 16 ].…”