Transcriptomic and Proteomic Analyses Show Minimal Role for ST2 on MCPT5-Expressing Mast Cells in Primary...

The IL-33/ST2 pathway is important as part of the type 2 immune response against helminth infections. Mast cells express the highest levels of the IL-33 receptor subunit ST2 of any immune cell, and mast cells can mediate type 2 immune inflammation; however, the role of IL-33-driven mast cell responses in helminth infection is poorly understood. We sought to determine the role of mast cell ST2 expression during Heligmosomoides polygyrus bakeri (Hpb) infection by generating mast cell conditional ST2 knockout (MCPT5^Cre × ST2^f/f, cKO) mice. These mice have normal frequencies of mast cells at steady state but show specific and strong (albeit incomplete) knockdown of ST2 expression on mast cells. On Hpb infection, faecal egg and adult worm burden were similar between cKO and littermate controls, as were mast cell degranulation markers, serum IgE and goblet cell hyperplasia. Therefore, we conclude that mast cell ST2 does not play a dominant role in Hpb infection. To further investigate the immune response to infection in cKO and littermate controls, transcriptomic and proteomic changes were assessed in duodenal tissues in infected versus naïve mice in cKO and control mice. Minimal transcriptomic and proteomic changes were seen between genotypes, whereas substantial changes were seen between naïve and infected mice, regardless of genotype. Hpb infection induced local increases at the transcript and protein level for mast cell proteases (MCPT1 and MCPT2), resistin-like molecules (RELMα and RELMβ) and markers such as the phospholipase PLA2G4C and the pore-forming protein gasdermin C. Bulk proteomic analysis was also searched against the Hpb genome to identify Hpb proteins present in the duodenal tissues. A list of 60 Hpb proteins of interest was identified in infected duodenal samples, of which 18 contain a signal peptide and are present in the excretory/secretory products of Hpb (HES) (likely secretory products including immunomodulatory proteins); 28 proteins are present in HES but do not contain a signal peptide (likely excretory products); and 14 proteins are not present in HES (likely proteins present in the remnants of Hpb within the duodenum). This work thus provides datasets for changes in the mouse intestine due to Hpb infection, at both the transcript and protein level, as well as a dataset of Hpb proteins detectable in the mouse duodenum at day 14 of infection.