Department of Microbiology, University of Colorado School of Medicine, Aurora, Colorado, United States of America.
PLoS One. 2012;7(8):e42434. doi: 10.1371/journal.pone.0042434. Epub 2012 Aug 7.
The secreted colonization factor, TcpF, which is produced by Vibrio cholerae 01 and 0139, has generated interest as a potential protective antigen in the development of a subunit vaccine against cholera. This study evaluated immunogenicity/protective efficacy of a TcpF holotoxin-like chimera (TcpF-A2-CTB) following intraperitoneal immunization compared to TcpF alone, a TcpF+CTB mixture, or CTB alone. Immunization with the TcpF-A2-CTB chimera elicited significantly greater amounts of anti-TcpF IgG than immunization with the other antigens (P<0.05). Protective efficacy was measured using 6-day-old pups reared from immunized dams and orogastrically challenged with a lethal dose of El Tor V. cholerae 01 Inaba strain N16961. Protection from death, and weight loss analysis at 24 and 48 hours post-infection demonstrated that immunization with TcpF alone was poorly protective. However, immunization with TcpF+CTB was highly protective and showed a trend toward greater protection than immunization with CTB alone (82% vs 64% survival). Immunization with the TcpF-A2-CTB chimera demonstrated less protection (50% survival) than immunization with the TcpF+CTB mixture. The TcpF-A2-CTB chimera used for this study contained the heterologous classical CTB variant whereas the El Tor CTB variant (expressed by the challenge strain) was used in the other immunization groups. For all immunization groups that received CTB, quantitative ELISA data demonstrated that the amounts of serum IgG directed against the homologous immunizing CTB antigen was statistically greater than the amount to the heterologous CTB antigen (P≤0.003). This finding provides a likely explanation for the poorer protection observed following immunization with the TcpF-A2-CTB chimera and the relatively high level of protection seen after immunization with homologous CTB alone. Though immunization with TcpF alone provided no protection, the additive protective effect when TcpF was combined with CTB demonstrates its possible value as a component of a multivalent subunit vaccine against Vibrio cholerae 01 and 0139.
分泌的定植因子 TcpF 由霍乱弧菌 01 型和 0139 型产生，作为霍乱亚单位疫苗的潜在保护性抗原引起了关注。本研究评估了腹腔内免疫 TcpF 全长毒素样嵌合体（TcpF-A2-CTB）与单独的 TcpF、TcpF+CTB 混合物或 CTB 相比的免疫原性/保护效力。用 TcpF-A2-CTB 嵌合体免疫可诱导产生比用其他抗原免疫更高水平的抗 TcpF IgG（P<0.05）。通过用免疫母鼠饲养的 6 日龄幼仔进行攻毒，并向其口咽给予致死剂量的 El Tor 霍乱弧菌 01 型 Inaba 株 N16961，来测量保护效力。从死亡和感染后 24 小时和 48 小时的体重减轻分析表明，单独用 TcpF 免疫的保护作用较差。然而，用 TcpF+CTB 免疫具有高度保护作用，并且与单独用 CTB 免疫相比具有更大的保护趋势（82%的存活率）。用 TcpF-A2-CTB 嵌合体免疫的保护作用（50%的存活率）低于用 TcpF+CTB 混合物免疫的保护作用。用于本研究的 TcpF-A2-CTB 嵌合体含有异源经典 CTB 变体，而挑战株表达的 El Tor CTB 变体（expressed by the challenge strain）则用于其他免疫组。对于所有接受 CTB 的免疫组，定量 ELISA 数据表明，针对同源免疫 CTB 抗原的血清 IgG 数量在统计学上大于针对异源 CTB 抗原的数量（P≤0.003）。这一发现为用 TcpF-A2-CTB 嵌合体免疫后观察到的保护作用较差以及用同源 CTB 单独免疫后观察到的相对高水平保护作用提供了一个可能的解释。虽然单独用 TcpF 免疫不能提供保护，但 TcpF 与 CTB 联合使用的附加保护作用表明其作为霍乱弧菌 01 型和 0139 型多价亚单位疫苗的组成部分可能具有价值。
