Highly modified and immunoactive N-glycans of the canine heartworm

Francesca Martini,Barbara Eckmair,Monika Garg,Shi Yan,Carmen Jiménez-Castells,Iain B H Wilson,Alba Hykollari,Daniel Varón Silva,Chunsheng Jin,Katharina Paschinger,Christine Neupert,Saša Štefanić,Luigi Venco

doi:10.1038/s41467-018-07948-7

Abstract

The canine heartworm (Dirofilaria immitis) is a mosquito-borne parasitic nematode whose range is extending due to climate change. In a four-dimensional analysis involving HPLC, MALDI-TOF–MS and MS/MS in combination with chemical and enzymatic digestions, we here reveal an N-glycome of unprecedented complexity. We detect N-glycans of up to 7000 Da, which contain long fucosylated HexNAc-based repeats, as well as glucuronylated structures. While some modifications including LacdiNAc, chitobiose, α1,3-fucose and phosphorylcholine are familiar, anionic N-glycans have previously not been reported in nematodes. Glycan array data show that the neutral glycans are preferentially recognised by IgM in dog sera or by mannose binding lectin when antennal fucose and phosphorylcholine residues are removed; this pattern of reactivity is reversed for mammalian C-reactive protein, which can in turn be bound by the complement component C1q. Thereby, the N-glycans of D. immitis contain features which may either mediate immunomodulation of the host or confer the ability to avoid immune surveillance.

Highlights

The canine heartworm (Dirofilaria immitis) is a mosquito-borne parasitic nematode whose range is extending due to climate change
In the case of D. immitis, there is fragmentary information regarding its glycomic capacity with data based on radiolabelling and lectin affinity indicating the potential presence of core and antennal fucose on tri- and tetra-antennary N-glycans, some of which are capped with N-acetyl-galactosamine[13], as well as of oligomannosidic structures[14]
For the first time, we test the ability of selected lectins, immunoglobulins, a pentraxin (C-reactive protein) and the complement component C1q to directly or indirectly bind natural parasitic nematode glycans in an array format, which paves the way for structure-informed functional studies

Summary

Introduction

The canine heartworm (Dirofilaria immitis) is a mosquito-borne parasitic nematode whose range is extending due to climate change. In the case of D. immitis, there is fragmentary information regarding its glycomic capacity (i.e. the range of possible glycan modifications) with data based on radiolabelling and lectin affinity indicating the potential presence of core and antennal fucose on tri- and tetra-antennary N-glycans, some of which are capped with N-acetyl-galactosamine[13], as well as of oligomannosidic structures[14]. Were the expected fucosylated and nonfucosylated forms of LacdiNAc (GalNAcβ1,4GlcNAc) motifs found, and high molecular weight N-glycans with long N-acetylhexosamine (HexNAc)-based repeat units with modifications by fucose (Fuc), phosphorylcholine (PC) or glucuronic acid (GlcA). For the first time, we test the ability of selected lectins, immunoglobulins, a pentraxin (C-reactive protein) and the complement component C1q to directly or indirectly bind natural parasitic nematode glycans in an array format, which paves the way for structure-informed functional studies

Methods

Results

Conclusion