Department of Microbiology, University of Colorado School of Medicine, Aurora, CO, USA.
PLoS One. 2013;8(2):e57269. doi: 10.1371/journal.pone.0057269. Epub 2013 Feb 28.
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.
霍乱毒素（CT）是导致严重霍乱的主要毒力因子。不能产生 CT 的霍乱弧菌菌株在动物和人类中表现出严重的毒力衰减。CT 的五聚体 B 亚基（CTB）包含被中和 CT 的抗体识别的免疫显性表位。尽管 CTB 是一种有效的免疫原，并且在动物模型中是一种有前途的保护性疫苗抗原，但用解毒 CT 免疫人类未能预防霍乱。然而，我们最近证明，用重组 CTB 经腹腔内（IP）免疫 3 剂的幼鼠可以很好地抵抗高致死性霍乱弧菌 N16961 挑战剂量的攻击。本研究探讨了 CTB 的免疫途径和次数如何影响幼鼠霍乱模型中的保护效力。为此，雌性小鼠经鼻内（IN）、腹腔内（IP）和皮下（SC）免疫 CTB。通过定量 ELISA 分析血清和粪便提取物中的抗 CTB 抗体，并用致死剂量的霍乱弧菌经口挑战免疫母亲所生的幼鼠。所有免疫组的幼鼠均能高度免受死亡（48 小时时 64-100%存活）。Cox 回归显示，24 小时时体重减轻的百分比预测到 48 小时时的死亡，但我们无法验证特定的体重减轻量作为保护的替代标志物。尽管 CTB 在所有方案中均具有高度保护作用，但三种肠外免疫方案显示出在感染后 24 小时时存活率更高和体重减轻更少的趋势。这些结果表明，通过几种途径和剂量方案免疫 CTB 可提供针对活霍乱弧菌攻击的保护，在幼鼠霍乱模型中。我们的数据扩展了先前研究的结果，并为在霍乱弧菌亚单位疫苗的开发中纳入 CTB 提供了额外的支持。
