Alpha-galactosylceramide enhances mucosal immunity to oral whole-cell cholera vaccines

Abstract

Cholera is a severe diarrheal disease caused by the bacterium Vibrio cholerae (V. cholerae) that results in 3-4 million cases globally with 100,000-150,000 deaths reported annually. Mostly confined to developing nations, current strategies to control the spread of cholera include the provision of safe drinking water and improved sanitation and hygiene, ideally in conjunction with oral vaccination. However, difficulties associated with the costs and logistics of these strategies have hampered their widespread implementation. Specific challenges pertaining to oral cholera vaccines (OCVs) include a lack of safe and effective adjuvants to further enhance gut immune responses, the complex and costly multicomponent vaccine manufacturing, limitations of conventional liquid formulation and the lack of an integrated delivery platform. Herein we describe the use of the orally active adjuvant α-Galactosylceramide (α-GalCer) to strongly enhance intestinal bacterium-and toxin-specific IgA responses to the OCV, Dukoral ® in C57BL/6 and BALB/c mice. We further demonstrate the mucosal immunogenicity of a novel multi-antigen, singlecomponent whole-cell killed V. cholerae strain and the enhancement of its immunogenicity by adding α-GalCer. Finally, we report that combining these components and recombinant cholera toxin B subunit in the SmPill ® minisphere delivery system induced strong intestinal and systemic antigen-specific antibody responses.

Technological Approaches for Improving Vaccination Compliance and Coverage

“…It was also shown that a novel whole-cell killed Vibrio cholerae strain and recombinant cholera toxin subunit B (CTB) could be successfully loaded as antigens in SmPill ® minispheres. Consistent with the previous findings, Davitt and colleagues demonstrated that combining these antigens and α-GalCer in SmPill ® minispheres enhanced intestinal lipopolysaccharide and CTB-specific IgA responses and induced intestinal antigen-specific Th1 responses ( Figure 2) [88].…”

“…Some iNKT cell agonists have been investigated as adjuvants to enhance immune responses in immunotherapy and vaccination strategies [86]. Lavelle and colleagues demonstrated the potential of the iNKT cell activator α-Galactosylceramide (α-GalCer) as an oral adjuvant to enhance intestinal immune responses induced by experimental whole-cell killed ETEC [87], Vibrio cholerae [88] and Helicobacter pylori [89] antigens in mouse models. In addition, a novel oral delivery-integrated system named Single Multiple Pill ® (SmPill ® ), containing oil-in-water emulsions formulated as 1 mm minispheres, was reported to effectively protect and enhance the release of various drugs in targeted intestinal regions [90].…”

An oral alpha-galactosylceramide adjuvanted Helicobacter pylori vaccine induces protective IL-1R- and IL-17R-dependent Th1 responses

“…The killing of mice and subsequent analysis of cellular responses were performed as previously described. 23 Splenocytes and MLN cells were plated at 1 × 10 6 cells/ml in complete Roswell Park Memorial Institute (cRPMI). Cells were stimulated for 72 h at 37 °C/5%CO 2 with the following stimuli: boiled Hel 305 lysate antigens (1 µg/ml) or purified MP305 (1 µg/ml).…”

“…Fecal pellet supernatants and serum samples were collected and prepared as previously described. 22,23 Mice were placed into individual cages and five fresh fecal pellets were collected in 500 µl of cold fecal pellet buffer (0.1 mg/ml Soybean trypsin inhibitor (Sigma Aldrich), 1% Bovine Serum Albumin (BSA), 25 mM ethylenediaminetetraacetic acid (EDTA) (Gibco), 1 mM PEFABloc (Sigma Aldrich), 50% Glycerol in 1× PBS)) and kept on ice for 4 h. Samples were then weighed, emulsified, centrifuged at 15,400 × g for 5 min at 4 °C and supernatants were stored at −20 °C until further use. Blood was obtained from mice by incision into the tail vein.…”

“…18,19 Indeed, promising results have been observed in mouse models of H. pylori infection using candidate vaccines in combination with the detoxified mutant adjuvants like double-mutant LT and multiple-mutated CT. 19,20 There is an urgent need to evaluate adjuvants that are potentially safe for human use and here we report promising results using the invariant natural killer T-cell (iNKT) activator, α-Galactosylceramide (α-GalCer) as an adjuvant in an inactivated WC vaccine against H. pylori . This adjuvant was previously found to potentiate mucosal immune responses induced by experimental Herpes simplex virus (HSV), 21 enterotoxigenic Escherichia coli 22 and oral cholera 23 vaccines. The goal of the current study was to evaluate the efficiency of the α-GalCer adjuvant compared with the “gold standard” CT when orally co-administered with WC killed H. pylori candidate vaccine with regard to protective efficacy as well as mucosal and systemic immunogenicity.…”