The Carbohydrate-linked Phosphorylcholine of the Parasitic Nematode Product ES-62 Modulates Complement Activation

Umul Kulthum Ahmed, N Claire Maller, Asif Jilani Iqbal, Lamyaa Al-Riyami, William Harnett, John G Raynes

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


Parasitic nematodes manufacture various carbohydrate-linked phosphorylcholine (PCh)-containing molecules, including ES-62, a protein with an N-linked glycan terminally substituted with PCh. The PCh component is biologically important because it is required for immunomodulatory effects. We showed that most ES-62 was bound to a single protein, C-reactive protein (CRP), in normal human serum, displaying a calcium-dependent, high-avidity interaction and ability to form large complexes. Unexpectedly, CRP binding to ES-62 failed to efficiently activate complement as far as the C3 convertase stage in comparison with PCh-BSA and PCh-containing Streptococcus pneumoniae cell wall polysaccharide. C1q capture assays demonstrated an ES-62-CRP-C1q interaction in serum. The three ligands all activated C1 and generated C4b to similar extents. However, a C2a active site was not generated following ES-62 binding to CRP, demonstrating that C2 cleavage was far less efficient for ES-62-containing complexes. We proposed that failure of C2 cleavage was due to the flexible nature of carbohydrate-bound PCh and that reduced proximity of the C1 complex was the reason that C2 was poorly cleaved. This was confirmed using synthetic analogues that were similar to ES-62 only in respect of having a flexible PCh. Furthermore, ES-62 was shown to deplete early complement components, such as the rate-limiting C4, following CRP interaction and thereby inhibit classical pathway activation. Thus, flexible PCh-glycan represents a novel mechanism for subversion of complement activation. These data illustrate the importance of the rate-limiting C4/C2 stage of complement activation and reveal a new addition to the repertoire of ES-62 immunomodulatory mechanisms with possible therapeutic applications.

Original languageEnglish
Pages (from-to)11939-53
Number of pages15
JournalJournal of Biological Chemistry
Issue number22
Early online date4 Apr 2016
Publication statusPublished - 27 May 2016


  • Binding Sites
  • C-Reactive Protein
  • Carbohydrate Conformation
  • Complement Activation
  • Complement C2
  • Complement C3-C5 Convertases
  • Complement C4
  • Complement Pathway, Classical
  • Helminth Proteins
  • Humans
  • Phosphorylcholine
  • Surface Plasmon Resonance
  • Journal Article
  • Research Support, Non-U.S. Gov't


Dive into the research topics of 'The Carbohydrate-linked Phosphorylcholine of the Parasitic Nematode Product ES-62 Modulates Complement Activation'. Together they form a unique fingerprint.

Cite this