Exploration of the regulatory mechanism of the vasoactive intestinal peptide-eosinophil axis in sheep resistance to Moniezia benedeni infection.

The enteric neuro - mucosal immune network serves as the core defense line for hosts against intestinal parasitic infections, and the vasoactive intestinal peptide (VIP) - eosinophil (Eos) axis plays a critical regulatory role in anti - parasitic immunity. In this study, special staining, ELISA, immunohistochemistry, and multiplex immunofluorescence techniques were employed to systematically explore the regulatory mechanism of the VIP - Eos axis in sheep resistance to Moniezia benedeni (M. benedeni) infection. The results showed that: VIP+ nerve fibers were mainly localized in the muscular layer and lamina propria of the sheep small intestine; after infection, the VIP expression level in each intestinal segment was extremely significantly increased by 234.43% - 276.93%, and there was a close spatial interaction with the synaptic regulatory protein SNAP - 25; eosinophils were widely distributed around VIP+ nerve fibers, and their distribution density was extremely significantly increased by 91.38% - 216.44% post-infection; some eosinophils expressed VIP receptor 1 (VIPR1), and the density of VIPR1+ eosinophils was significantly increased by 81.21% - 115.79% after infection; furthermore, VIPR1+ eosinophils expressed the high-affinity IgE receptor (FcεRI), suggesting that they exert anti-parasitic effects through IgE - mediated inflammatory responses. This study demonstrated that the VIP - Eos axis exerts an important regulatory role in sheep resistance to M. benedeni infection, revealed the signal integration mechanism of the enteric neuro-mucosal immune network, and provided a crucial theoretical basis for the precise prevention and control of sheep cestodiasis.