Transcription of interleukin 31 and its receptor by leukocytes after Culicoides sp stimulation is dose dependent but is not exaggerated in allergic horses or correlated with pruritus.

OBJECTIVE: Preliminary evidence supports a role for IL-31 in equine insect bite hypersensitivity (IBH) and pruritus. Our studies investigated IL-31 and IL-31 receptor-α (IL-31RA) transcription in leukocytes from normal and IBH horses in response to Culicoides nubeculosus. ANIMALS: 19 normal and 15 IBH horses were recruited in the summer of 2019 (low-dose study) and 8 normal and 10 IBH horses in the winter of 2022 to 2023 (high-dose study). Normal horses had no history or signs of allergic skin disease, while IBH horses had a history and clinical signs compatible with IBH. Pruritus was scored using a visual analog score or a 1 to 6 grading system. PROCEDURES: Whole blood leukocytes were incubated with saline (0.9% NaCl) solution or C nubeculosus (0.26 µg/mL [low dose]; 5 µg/mL [high dose]). Transcription of IL-31 and IL-31RA was measured by quantitative RT-PCR. RESULTS: Transcription of IL-31 and IL-31RA significantly increased in leukocytes from normal and IBH horses following high-dose C nubeculosus, and no differences were found between populations. Following low-dose C nubeculosus IL-31RA, transcription was increased in both normal and IBH horses, but IL-31 transcription was reduced in normal horses. No positive correlation was found between pruritus scores and IL-31 transcription after low- or high-dose C nubeculosus stimulation. CLINICAL RELEVANCE: Exaggerated IL-31 transcription was not identified in IBH horses, suggesting that dysregulation in IL-31 signaling occurs downstream or in localized tissues or involves regulation by yet unidentified receptor splice variants or IL-31-induced increased sensitivity to other pruritogens. Further studies to understand IL-31 signaling in equine allergic skin disease are needed.

Changes in protein expression in the sheep abomasum following trickle infection with Teladorsagia circumcincta.

Continual low-level exposure of sheep to the helminth Teladorsagia circumcincta elicits a temporary protective immunity, where factors in the immune abomasal mucosa prevent penetration of infective larvae, but which is essentially lost within 6 weeks of cessation of parasite challenge. Here, a proteomic approach was used to identify proteins that are differentially regulated in immune compared to naïve sheep, as potential key mediators of immunity. Six naïve sheep and 12 sheep trickle-infected with T. circumcincta were treated with anthelmintic, and the naïve (control) and 6 immune sheep were killed 7 days later. The remaining 6 sheep (immune waning) were killed 42 days after anthelmintic treatment. Abomasal tissue samples were subjected to 2D-gel electrophoresis and densitometric analysis. Selected spots (n=73) were identified by peptide mass fingerprinting and confirmatory Western blotting was carried out for 10 proteins. Spots selectively up-regulated in immune versus control, but not immune waning versus control sheep, included galectin-15 and thioredoxin, which were confirmed by Western blotting. In immune sheep, serum albumin was significantly down-regulated and albumin proteolytic cleavage fragments were increased compared to controls. Unexpectedly, albumin mRNA was relatively highly expressed in control mucosa, down-regulated in immune, and was immunolocalized to mucus-producing epithelial cells. Thus we have identified differential expression of a number of proteins following T. circumcincta trickle infection that may play a role in host protection and inhibition of parasite establishment.