An oral cholera vaccine in the prevention and/or treatment of inflammatory bowel disease

Abstract

The oral cholera vaccine WC-rBS consists of 4 different inactivated strains of Vibrio cholerae (LPS source) admixed with recombinant cholera toxin B subunit. Because of its unique composition and anti-inflammatory properties reported for both CTB and low doses of LPS from other Gram-negative bacteria, we speculated that WC-rBS might have anti-inflammatory potential in a chronic autoimmune disease such as inflammatory bowel diseases. First in vitro endotoxin tolerance experiments showed the surprising WC-rBS potential in the modulation of inflammatory responses on both PBMCs and THP1 cells. WC-rBS was further evaluated in the Dextran Sodium Sulfate colitis mouse model. Administrated orally at different dosages, WC-rBS vaccine was safe and showed immunomodulatory properties when administered in a preventive mode (before and during the induction of DSS colitis) as well as in a curative mode (after colitis induction); with improvement of disease activity index (from 27 to 73%) and histological score (from 65 to 88%). Interestingly, the highest therapeutic effect of WC-rBS vaccine was observed with the lowest dosage, showing even better anti-inflammatory properties than mesalamine; an approved 5-aminosalicylic acid drug for treating IBD patients. In summary, this is the first time that a prophylactic medicine, safe and approved for prevention of an infectious disease, showed a benefit in an inflammatory bowel disease model, potentially offering a novel therapeutic modality for IBD patients.

Fig 1. Suppression of TNFα response and enhancement of IL-10 response to LPS in THP-1 monocytes or PBMCs pretreated with WC-rBS vaccine.

THP-1 monocytes (A, C) or PBMCs (B, D) were pretreated for 16 to 24 h with media, rCTB (10 μg/mL), or WC-rBS vaccine (accordingly diluted to 10μg/mL rCTB) and then challenged with LPS (1 μg/mL). Supernatants were collected 6h post challenge to assess TNFα secretion from PBMCs (B) or 24 h post-challenge to assess TNFα (A) secretion from THP-1 cells and IL-10 secretion from THP-1 cells (C) and PBMCs (D). Bars represent mean ±SEM. Statistics: One-way ANOVA with Dunnett’s multiple comparison. ns: non-significant, * p-value < 0.05, *** p-value < 0.001.

Fig 2. Anti-inflammatory potential of WC-rBS vaccine in a colitis DSS model.

Mice were exposed to 2.5% DSS for 5 consecutive days (days 0 to 5) and orally administrated with WC-rBS 25, WC-rBS 5, or PBS on days -6, -3, 0, 3 and 6 (A). As a control, one group of mice received Mesalamine drug ad libitum over the whole experiment. One healthy control group (CTRL + PBS) was not exposed to DSS. Body weight was recorded individually throughout the entire experiment and percent change calculated (B). On day 12 mice were euthanized. DAI score(C), colon length (D) and global histological score (E) were determined and MPO quantified by ELISA on colonic sections (F). Bars represent mean ±SEM. Statistics: Permutation test. ns: non-significant, * p-value < 0.05, ** p-value < 0.01, *** p-value < 0.001.

Fig 3. Lower WC-rBS vaccine doses improved DSS colitis outcome.

Mice were exposed to 2.5% DSS for 5 consecutive days (days 0 to 5) and orally administrated with WC-rBS 5, WC-rBS 3, WC-rBS 1 or PBS on days -6, -3, 0, 3 and 6 (A). As a control, one group of mice received Mesalamine drug ad libitum over the whole experiment. One healthy control group (CTRL + PBS) was not exposed to DSS. Body weight was recorded individually throughout the entire experiment and percent change calculated (B). On day 12 mice were euthanized. DAI score (C), colon length (D) and global histological score (E) were determined and MPO quantified by ELISA on colonic sections (F). Bars represent mean ±SEM. Statistics: Permutation test. ns: non-significant, * p-value < 0.05, ** p-value < 0.01, *** p-value < 0.001.

Fig 4. WC-rBS vaccine doses improved histological damages.

Mice were exposed to 2.5% DSS for 5 consecutive days (0 to 5) and orally administered with WC-rBS 5, WC-rBS 3 or WC-rBS 1 as either preventive or curative treatments. Additional groups served as control groups, receiving no treatment nor DSS, or only DSS, or DSS plus ad libitum mesalamine drug. On day 12 mice were euthanized, sections of colonic tissues (4μm) were sampled and stained with May‐Grunwald‐Giemsa for histological evaluation of control groups (A), groups administered preventively with WC-rBS (B), and groups administered curatively with WC-rBS (C). Related histological scores are indicated below each picture.

Fig 5. WC-rBS vaccine also improved DSS colitis outcome when administered curatively.

Mice were exposed to 2.5% DSS for 5 consecutive days (0 to 5) and orally administrated with WC-rBS 5, WC-rBS 1, or PBS on days 3 and 6 (A). As controls, one group of mice received Mesalamine drug ad libitum over the whole experiment and one healthy control group was not exposed to DSS. Body weight was recorded individually over the entire experiment and percent change calculated (B). On day 12 mice were euthanized. DAI score (C), colon length (D) and global histological score (E) were determined and MPO quantified by ELISA on colonic sections (F). Bars represent mean ±SEM. Statistics: Permutation test. ns: non-significant, * p-value < 0.05, ** p-value < 0.01, *** p-value < 0.001.