Authors

V Shek¹; DJ Smyth¹; HJ McSorley¹;  ¹ University of Dundee, UK

Discussion

Helminth infections persist by influencing host immunity through their molecular products, thereby preventing immune ejection. In addition, the immunomodulatory properties of these molecules can prove useful in suppressing immune-mediated diseases. The intestinal nematode Heligmosomoides polygyrus bakeri (Hpb) secretes many immunomodulatory molecules, notably: HpARI and HpBARI, which antagonise the IL-33 pathway, and HpTGM which mediates a regulatory response by inducing Treg cells. All three molecules are structurally similar, consisting of a string of consecutive atypical Complement Control Protein (CCP) domains. This led to the hypothesis that CCP domain-containing proteins may represent a family of immunomodulatory molecules used by Hpb to evade the host immune response. 

HpARI and HpTGM are not classified as CCP domain-containing proteins by current protein domain prediction tools, prompting the development of a new atypical CCP motif. Through sequence alignment analyses of HpARI, HpBARI, HpTGM and all Hpb genes classified as conventional CCP domains defined by InterPro IPR000436, a novel atypical CCP motif was generated. To identify CCP domain-containing proteins like the Hpb immunomodulators, this motif was screened against an in-house Hbp transcriptome and genomic data from WormBase ParasSite. Selected candidates were produced as recombinant proteins using the Expi293 expression system and assessed for interactions with host immune proteins using the Avidity-based Extracellular Interaction Screening (AVEXIS) assay. 

We confirmed known parasite-host interactions using this technique, including HpARI-IL-33, HpBARI-ST2 and HpTGM-TGFβR. Additionally, we have identified a novel interaction between the Hpb-secreted CCP-domain protein “61365” with host RELM-β, a cysteine-rich secretory cytokine predominantly expressed in the gastrointestinal tract. RELM-β is involved in regulating intestinal homeostasis, promoting airway inflammation, and driving antiparasitic activity, making RELM-β an interesting target. Current work involves elucidating the mechanism in which 61365 modulates RELM-β. 

Taken together, this approach has identified a novel parasite-host interaction pair which will be further explored. The methods and analyses described here may assist the development of a larger pipeline in identifying, producing, and characterising new helminth immunomodulatory molecules which may prove beneficial for the development of novel anthelminthics or therapeutics for immune-mediated diseases