Cholera is an acute dehydrating diarrheal disease caused by Vibrio cholerae O1 infection. The mechanisms of protection against cholera are not well known. MAIT cells are recently described innate-like T cells with adaptive capacity. We have previously shown that circulating MAIT cells are activated during cholera and associated with V. cholerae LPS-specific antibody responses.¹ The objective of this study was to characterize MAIT cells in the intestinal mucosa during cholera. We collected stool, peripheral blood, and duodenal biopsy specimens by endoscopy from adults with confirmed V. cholerae O1 infection at days 2 and 30 after onset of disease. We used multispectral fluorescence microscopy of frozen duodenal sections (n=5) to demonstrate that MAIT (CD3⁺IL-18Rα⁺Vα7.2⁺) cells are mostly present in the crypt of the duodenal lamina propria (LP) and are more abundant at day 2 post-illness (2.8 ± 0.8% of CD3⁺ cells) compared with day 30 (0.9 ± 0.1%; p < 0.05). Using flow cytometry of fresh duodenal tissue (n=10), we found that a greater percentage of duodenal MAIT (Vα7.2⁺CD161⁺) cells are activated (CD38⁺) than those in the periphery at both time points, and that duodenal MAITs are more activated at day 2 of infection (58 ± 21% CD38⁺ of all MAITs) than at day 30 (41 ± 16%; p=0.13). Stool alpha-1-antitrypsin, a marker of intestinal permeability, and stool myeloperoxidase, a marker of intestinal inflammation, were correlated with a loss of duodenal MAITs between time points (p = 0.03, and 0.003, respectively). Circulating MAIT cells from cholera patients stimulated with V. cholerae-fed monocytes secrete significantly higher IFN-γ compared with stimulated Vα7.2⁺CD161^- (non-MAIT) cells. In summary, we report the activation and loss of duodenal MAIT cells during human V. cholerae O1 infection, and the degree of loss was correlated with stool markers of intestinal permeability and inflammation.