N-glycomics analysis of Anisakis excretory/secretory products

Abstract text

Anisakis simplex is a parasitic aquatic nematode, which may cause mild-to-severe gastrointestinal allergic reactions (Anisakiasis) with clinical symptoms, such as rhinitis and urticaria in humans who accidentally consume raw or undercooked marine products contaminated with infective L3 Anisakis larvae. Several Anisakis excretory/secretory (ES) products and somatic proteins are known to be involved in IgE-mediated allergic reactions. In comparison to vertebrates, nematodes have a distinct machinery to glycosylate their proteins and unusual glycan structures have been reported previously, many of which play immunogenic and immunomodulatory roles in host-parasite interactions. While an early study indicated that O-glycans participate the cross-reactivity of antibodies in allergy patients to A. simplex somatic antigens, the N-glycosylation pattern of Anisakis and the potential role of N-glycans in allergic reactions remained unknown. The aim of this study was to characterise N-glycans from Anisakis ES products using mass spectrometry. We harvested ES products from larvae culture and released N-glycans from trypsinised proteins using PNGase A. Native glycans were pyridilaminated prior to HPLC separation and MALDI-TOF-MS/MS analysis. In addition, hydrofluoric acid and glycosidase digestions were performed to aid structural characterisation. MS data of 5h and 24h ES products indicated the presence of pauci-mannose and core fucosylated N-glycans as major species; tri-fucosylated and methylated glycans as well as complex-type and phosphorylcholine-substituted glycans were also detected. Our study provides the first insight into the N-glycosylation machinery of Anisakis and highlights the needs for investigating whether and which N-glycans are indubitably involved in the modulation of allergic responses.

Keywords: Anisakis simplex, parasitic nematodes, N-glycans, glycomics, allergens