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Immunization with cholera toxin B subunit induces high-level protection in the suckling mouse model of cholera.

Price GA, McFann K, Holmes RK - PLoS ONE (2013)

Bottom Line: To this end female mice were immunized with CTB intranasally (IN), IP, and subcutaneously (SC).Pups from all immunized groups were highly protected from death by 48 hours (64-100% survival).Cox regression showed that percent body weight loss at 24 hours predicted death by 48 hours, but we were unable to validate a specific amount of weight loss as a surrogate marker for protection.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, University of Colorado School of Medicine, Aurora, CO, USA.

ABSTRACT
Cholera toxin (CT) is the primary virulence factor responsible for severe cholera. Vibrio cholerae strains unable to produce CT show severe attenuation of virulence in animals and humans. The pentameric B subunit of CT (CTB) contains the immunodominant epitopes recognized by antibodies that neutralize CT. Although CTB is a potent immunogen and a promising protective vaccine antigen in animal models, immunization of humans with detoxified CT failed to protect against cholera. We recently demonstrated however that pups reared from mice immunized intraperitoneally (IP) with 3 doses of recombinant CTB were well protected against a highly lethal challenge dose of V. cholerae N16961. The present study investigated how the route and number of immunizations with CTB could influence protective efficacy in the suckling mouse model of cholera. To this end female mice were immunized with CTB intranasally (IN), IP, and subcutaneously (SC). Serum and fecal extracts were analyzed for anti-CTB antibodies by quantitative ELISA, and pups born to immunized mothers were challenged orogastrically with a lethal dose of V. cholerae. Pups from all immunized groups were highly protected from death by 48 hours (64-100% survival). Cox regression showed that percent body weight loss at 24 hours predicted death by 48 hours, but we were unable to validate a specific amount of weight loss as a surrogate marker for protection. Although CTB was highly protective in all regimens, three parenteral immunizations showed trends toward higher survival and less weight loss at 24 hours post infection. These results demonstrate that immunization with CTB by any of several routes and dosing regimens can provide protection against live V. cholerae challenge in the suckling mouse model of cholera. Our data extend the results of previous studies and provide additional support for the inclusion of CTB in the development of a subunit vaccine against V. cholerae.

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Related in: MedlinePlus

Relative abundance of fecal CTB-specific IgA at 14 days following the final/only immunization via the intranasal (IN), subcutaneous (SC), or intraperitoneal (IP) route.For each fecal extract, the relative abundance of CTB-specific IgA is expressed as a percentage of the total IgA in that fecal extract. Each symbol represents an individual mouse, and horizontal bars represent the geometric mean for that group (n = 5). Statistical differences between groups were analyzed using ANOVA with Tukey-Kramer post-test analysis (# P<0.001 versus all other groups).
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pone-0057269-g003: Relative abundance of fecal CTB-specific IgA at 14 days following the final/only immunization via the intranasal (IN), subcutaneous (SC), or intraperitoneal (IP) route.For each fecal extract, the relative abundance of CTB-specific IgA is expressed as a percentage of the total IgA in that fecal extract. Each symbol represents an individual mouse, and horizontal bars represent the geometric mean for that group (n = 5). Statistical differences between groups were analyzed using ANOVA with Tukey-Kramer post-test analysis (# P<0.001 versus all other groups).

Mentions: Fecal extracts were analyzed for CTB-specific IgA levels 14 days after the final/only immunization. In an effort to eliminate sample-to-sample and/or mouse-to-mouse variation, we normalized fecal CTB-specific IgA values by presenting them as percentages of total IgA in the corresponding fecal extracts (Fig. 3). Intranasal immunization was the most potent route for induction of fecal CTB-specific IgA, with values ranging from just under 2% to over 6% of total IgA in samples from individual mice. The geometric mean for the IN group was 3.8% of total IgA, whereas the rest of the immunized groups had CTB-specific geometric means that were detectable but less than 1% of total IgA. The levels measured in the IN immunized group were significantly higher then in all other groups (Fig. 3; P<0.001). Total IgA levels in the IN group were not significantly different from total IgA levels in the other groups (data not shown).


Immunization with cholera toxin B subunit induces high-level protection in the suckling mouse model of cholera.

Price GA, McFann K, Holmes RK - PLoS ONE (2013)

Relative abundance of fecal CTB-specific IgA at 14 days following the final/only immunization via the intranasal (IN), subcutaneous (SC), or intraperitoneal (IP) route.For each fecal extract, the relative abundance of CTB-specific IgA is expressed as a percentage of the total IgA in that fecal extract. Each symbol represents an individual mouse, and horizontal bars represent the geometric mean for that group (n = 5). Statistical differences between groups were analyzed using ANOVA with Tukey-Kramer post-test analysis (# P<0.001 versus all other groups).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585264&req=5

pone-0057269-g003: Relative abundance of fecal CTB-specific IgA at 14 days following the final/only immunization via the intranasal (IN), subcutaneous (SC), or intraperitoneal (IP) route.For each fecal extract, the relative abundance of CTB-specific IgA is expressed as a percentage of the total IgA in that fecal extract. Each symbol represents an individual mouse, and horizontal bars represent the geometric mean for that group (n = 5). Statistical differences between groups were analyzed using ANOVA with Tukey-Kramer post-test analysis (# P<0.001 versus all other groups).
Mentions: Fecal extracts were analyzed for CTB-specific IgA levels 14 days after the final/only immunization. In an effort to eliminate sample-to-sample and/or mouse-to-mouse variation, we normalized fecal CTB-specific IgA values by presenting them as percentages of total IgA in the corresponding fecal extracts (Fig. 3). Intranasal immunization was the most potent route for induction of fecal CTB-specific IgA, with values ranging from just under 2% to over 6% of total IgA in samples from individual mice. The geometric mean for the IN group was 3.8% of total IgA, whereas the rest of the immunized groups had CTB-specific geometric means that were detectable but less than 1% of total IgA. The levels measured in the IN immunized group were significantly higher then in all other groups (Fig. 3; P<0.001). Total IgA levels in the IN group were not significantly different from total IgA levels in the other groups (data not shown).

Bottom Line: To this end female mice were immunized with CTB intranasally (IN), IP, and subcutaneously (SC).Pups from all immunized groups were highly protected from death by 48 hours (64-100% survival).Cox regression showed that percent body weight loss at 24 hours predicted death by 48 hours, but we were unable to validate a specific amount of weight loss as a surrogate marker for protection.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, University of Colorado School of Medicine, Aurora, CO, USA.

ABSTRACT
Cholera toxin (CT) is the primary virulence factor responsible for severe cholera. Vibrio cholerae strains unable to produce CT show severe attenuation of virulence in animals and humans. The pentameric B subunit of CT (CTB) contains the immunodominant epitopes recognized by antibodies that neutralize CT. Although CTB is a potent immunogen and a promising protective vaccine antigen in animal models, immunization of humans with detoxified CT failed to protect against cholera. We recently demonstrated however that pups reared from mice immunized intraperitoneally (IP) with 3 doses of recombinant CTB were well protected against a highly lethal challenge dose of V. cholerae N16961. The present study investigated how the route and number of immunizations with CTB could influence protective efficacy in the suckling mouse model of cholera. To this end female mice were immunized with CTB intranasally (IN), IP, and subcutaneously (SC). Serum and fecal extracts were analyzed for anti-CTB antibodies by quantitative ELISA, and pups born to immunized mothers were challenged orogastrically with a lethal dose of V. cholerae. Pups from all immunized groups were highly protected from death by 48 hours (64-100% survival). Cox regression showed that percent body weight loss at 24 hours predicted death by 48 hours, but we were unable to validate a specific amount of weight loss as a surrogate marker for protection. Although CTB was highly protective in all regimens, three parenteral immunizations showed trends toward higher survival and less weight loss at 24 hours post infection. These results demonstrate that immunization with CTB by any of several routes and dosing regimens can provide protection against live V. cholerae challenge in the suckling mouse model of cholera. Our data extend the results of previous studies and provide additional support for the inclusion of CTB in the development of a subunit vaccine against V. cholerae.

Show MeSH
Related in: MedlinePlus