Identifying Novel Helminth Immunomodulatory Molecules

Abstract

Helminth infections persist by influencing host immunity through molecular products, preventing immune ejection. The intestinal nematode Heligmosomoides polygyrus bakeri (Hpb) secretes several immunomodulatory molecules: HpARI and HpBARI antagonize the IL-33 pathway, while HpTGM induces Treg cells to mediate a regulatory response. These molecules share a structure of consecutive atypical Complement Control Protein (CCP) domains, leading to the hypothesis that CCP domain-containing proteins represent a family of immunomodulatory molecules used by Hpb to evade the host immune response.

Since current domain prediction tools do not classify HpARI and HpTGM as CCP domain proteins, a new atypical CCP motif was developed through sequence alignment analyses of HpARI, HpBARI, HpTGM, and all Hpb genes classified as conventional CCP domains (IPR000436). This motif was screened against an in-house Hpb transcriptome and genomic data from WormBase Parasite to identify novel atypical CCP domain-containing proteins. The CCP candidates were produced as recombinant proteins in a mammalian expression system and assessed for host immune protein-protein interactions using the AVEXIS assay.

This led to the identification of a novel CCP domain-containing protein, 61365, which binds to RELMβ, a protein secreted by intestinal goblet cells, and the interaction was validated using biophysical techniques. Subsequent functional studies focused on understanding RELMβ biology, aiming to block its effects by co-administering 61365. I tested RELMβ in published macrophage activation and bacterial killing assays, however my result called into doubt published findings on the effects of RELMβ. I then moved to testing 61365 in RELMβ-dependent parasite ejection. Although 61365 did not make an effective vaccine against Hpb infection, my findings indicated that it may block RELMβ in N. brasiliensis infection, tending to delay rejection of the parasite. Therefore, 61365 may be a novel immunomodulatory protein which blocks RELMβ’s effects, allowing Hpb to persist in the host.

Date of Award	2024
Original language	English
Supervisor	Henry McSorley (Supervisor), Ignacio Moraga Gonzalez (Supervisor), Hermelijn H. Smits (Supervisor) & Alasdair C. Ivens (Supervisor)