Oral Cholera Vaccination as a Model to Assess Dietary Modulation of Gut Inflammation and Immunity

Abstract Objectives The aim was to develop a human challenge model in which modulation of immune and inflammatory response by food ingredients can be evaluated. We hypothesized that oral cholera vaccination, in addition to inducing a specific antibody response, induces a significant increase in gut inflammatory response. Methods Twenty healthy men (age 30.6 ± 1.8 y; BMI 24.9 ± 0.6) were enrolled in the study. Fecal and blood samples were collected at baseline. After a 2-week run-in period (D0-D14), subjects were vaccinated with oral cholera vaccine Dukoral (D15). After a period of 2 weeks, a second vaccination was administered (D29). Fecal samples were collected the day before (D14; D28) and the days (D16/D17; D30/D31) after each vaccination, as well as on D42. Blood samples were collected before vaccination (D15; D29), and on D16 and D17/D31, on D43. Primary outcome was fecal calprotectin concentration, secondary outcomes were serum levels of cholera toxin (CTB)-specific IgA and IgG. Other markers of local and systemic inflammatory response included beta-defensins, IP-10, IL-1 ra and hsCRP. Changes over time were tested by means of a linear mixed model. Outliers were identified with the 1.5xIQR rule and excluded from analysis. Results Fecal calprotectin did not increase after the first vaccination. After the second vaccination, a significant increase was observed: from 12.8 ± 2.5 μg/g feces (mean ± SEM) on day 29 to 18.0 ± 2.9 μg/g on day 31 (P = 0.017). Plasma CTB-specific IgA and IgG were strongly increased after the first vaccination, with a further increase after the second vaccination. Plasma CRP slightly decreased on D17, compared to D15 (P = 0.016). IL-1ra significantly decreased 2 days after the first vaccination (P = 0.011), whereas no change was observed after the second vaccination. Beta-defensin was significantly increased at D31 compared to D29 (from 42.7 ± 7.0 to 80.7 ± 16.1 (P = 0.014)). IP-10 did not show any response to vaccination. Conclusions In addition to the expected antibody response, oral cholera vaccination induces an increase in fecal calprotectin and beta defensin, pointing to vaccine induced intestinal inflammation. These readouts may be added to intervention studies with dietary compounds to evaluate the potential for modulating immune responsiveness. Funding Sources Bio&Medical Technol Developm Program of the Natl Res Foundation, Min Science & ICT of Rep Korea.