319 In Contrast to Vagus Stimulation, Vagotomy Increases the Severity of Food Allergy

Abstract

Background: Upon allergen encounter, food allergy typically leads to mast cell degranulation, an influx of Th2 immune cells together with increases in antigen specific antibodies. We showed that vagal nerve stimulation (VNS) increased Tregs and reduced mast cell activation in a mouse model of food allergy (DDW 2012). Here we aimed to test the hypothesis that, in contrast to VNS, vagotomy (VGX) would worsen food allergy. Methods: We sensitised balb/c mice to ovalbumin (OVA) adsorbed to aluminium-hydroxide (day 0&14) followed by intra-gastric gavages with OVA, from day 28 onwards. Sub-diaphragmatic VGX was performed at least one week prior to OVA gavage, together with pyloroplasty, where pyloroplasty alone served as control. Diarrhoea was scored for 1hr by analysing pellets, where 0 was normal faecal pellets, and 3 represents over diarrhoea. We determined serum mast cell proteases (mouse mast cell protease 1, MMCP-1), antibody titres (OVA specific IgG1 and IgG2a) and identified immune T-cell subsets in the mesenteric lymph nodes, lamina propria (LP) and Peyer's patches. Cytokines released upon OVA challenge from mesenteric lymph nodes were measured by cytometric bead array. Further, qPCR was used to determine cytokine mRNA. OVA-specific Treg proliferation was assessed by adoptive transfer of Naive DO11.10 T-cells. Results: VGX increased serum MMCP-1 levels from 1120 ± 136 vs 2841 ± 964 ng/mL (n=7, p,0.05) 1hr after the fourth OVA gavage, coinciding with increased diarrhoea scores (from 1.1 to 2.8 arbitrary score, P , 0.05) but no change in serum IgG1 or IgG2a. VGX did not change the population of Tregs (CD25+/foxp3+) in the MLN (14.2 ± 1.9 controls vs VGX 15.0 ± 2.0% of CD4+) or LP (45.4 ± 2.9 to 42.0 ± 8.0% of CD4+). Similarly, no change in Th1 (IFN γ+), Th17 (IL-17+) or Th2 (IL-4+/IL-5+) cells was found after VGX in the mesenteric lymph nodes as compared to control. OVA specific Tregs (CD25+/foxp3+% of CD4+/DO11.10+) in the mesenteric lymph nodes (4.6 ± 0.4 to 6.2 ± 0.7%), LP (81.1 ± 7.0 vs. 80.5 ± 4.2%) or Peyer's patches (24.5 ± 8.1 vs. 26.7 ± 6.4%) remained unchanged after VGX compared to controls (n=8-12). Jejunal mRNA levels (over RPL32 expression) for IL-13, IL-5, TNFα and IFNγ were not affected by VGX. Conclusion: As opposed to VNS, VGX increases the severity of food allergy, as shown by increased mast cell activation and diarrhoea scores compared to sham operated mice. CD4+ T cell skewing and cytokine production was however not affected by VGX. Our data indicate that reduced vagal tone renders mice more susceptible to develop food allergy further underscoring the role of the vagal innervation in modulating the mucosal immune system.