鳗弧菌O1/O2二价灭活疫苗免疫大菱鲆的抗体持续期和免疫保护期

本研究分析了鳗弧菌(Vibrio anguillarum)O1/O2血清型二价灭活疫苗免疫大菱鲆后的抗体持续期和免疫保护期。以鳗弧菌O1血清型VAM003株和O2血清型VAM007株为抗原制备了福尔马林灭活二价疫苗,将疫苗按照三种剂量(10~7 cells/尾、10~8 cells/尾、10~9 cells/尾)以腹腔注射途径免疫大菱鲆,在免疫后3 d、7 d、14 d、30 d、60 d、90 d、120 d、150 d,用血清凝集实验检测了免疫鱼血清的VAM003和VAM007抗体效价,用攻毒实验检测了疫苗的免疫保护率(RPS)。结果显示,在免疫后7 d三个剂量组的大菱鲆均产生了特异抗体,并获得27%～60%的RPS。三个剂量组大菱鲆的O1血清型抗体持续期分别90 d (10~7 cells/尾组)、150 d (10~8 cells/尾组)、150 d (10~9cells/尾组),而三个剂量组大菱鲆的O2血清型抗体持续期均150 d。三个剂量组的大菱鲆获得的免疫保护持续期均150 d;以RPS75%为有效免疫保护,各剂量组大菱鲆抵抗O1血清型病原感染的有效免疫保护期为:14～120d(10~7 cells组)、14～120 d (10~8 cells/尾)、14～150 d (10~9 cells/尾),抵抗O2血清型病原感染的有效免疫保护期为:14～60 d (10~7 cells组)、14～120 d (10~8 cells/尾)、14～120 d (10~9 cells/尾)。研究结果表明鳗弧菌二价灭活疫苗可为大菱鲆提供有效而稳定的免疫保护,获得的抗体持续期和免疫保护期为该疫苗的临床中试研究提供了基础。

Antibody persistence and immune protection duration in turbot vaccinated by a Vibrio anguillarum inactivated bivalent vaccine based on O1 and O2 serotype strains

Vibrio anguillarum is an important bacterial fish pathogen that can cause vibriosis extensively in economically-important fish including Scophthalmus maximus, Paralichthys olivaceus, Anguilla anguilla, and Lateolabrax japonicus in China. In our previous studies, we have carried out the epidemiological work of V. anguillarum in China, and demonstrated that V. anguillarum O1, O2, and O3 serotype strains are prevalent in marine fish farms. Vaccination is proven to be a safe and efficient route to prevent and control vibriosis. However, no commercial V. anguillarum vaccine is available in China. In this study, the antibody persistence and immune protection duration of a V. anguillarum inactivated bivalent vaccine based on O1 and O2 serotype strains were evaluated in turbot (Scophthalmus maximus). The V. anguillarum formalin-inactivated bivalent vaccine was prepared using O1 serotype VAM003 and O2 serotype VAM007 strains. Groups of turbot were injected intraperitoneally with three dosages of vaccine preparation, i.e, 10⁷ cells/ind, 10⁸ cells/ind, and 10⁹ cells/ind. At 3 d, 7 d, 14 d, 30 d, 60 d, 90 d, 120 d, and 150 d after injection, each immunized fish group was evaluated for their serum-antibody titers against VAM003 and VAM007 using a serum-agglutination test, and the relative percent survival (RPS) was evaluated by challenge with a 10 LD₅₀ (50% lethal dose) of VAM003 or VAM007. The results showed that specific antibodies against VAM003 and VAM007 were noticeably induced in the immunized fish as early as 7 d post-immunization, and an RPS of 27%-60% was detected in these fish. Specifically, the induced VAM003 antibody persisted in three dosage fish groups for at least 90 d for 10⁷ cells/ind, 150 d for 10⁸ cells/ind, and 150 d for 10⁹ cells/ind, respectively, while anti-VAM007 persisted in each of three dosage fish groups for more than 150 d. The immune protection duration for each of the three dosage groups all exceeded 150 d. With an RPS of more than 75% as an effective immune protection, the effective immune protection duration against O2 serotype V. anguillarum was 14-120 d for 10⁷ cells/ind fish group, 14-120 d for 10⁸ cells/ind group, and 14-150 d for 10⁹ cells/ind group, respectively, while the effective immune protection duration against O2 serotype were 14 d-60 d for 10⁷ cells/ind group, 14-120 d for 10⁸ cells/ind group, and 14-120 d for 10⁹ cells/ind group, respectively. We also analyzed the relationship between serum antibody titer and RPS of bivalent vaccine. When the serum antibody titer was over 1:40 for the O1 serotype and 1:160 for the O2 serotype, the corresponsive RPS to V. anguillarum O1 or O2 serotype were all over 75%. These results suggest that the V. anguillarum inactivated bivalent vaccine could provide effective immune protection for turbot, and the data of antibody persistence and immune protection duration obtained in this study will provide support for clinical trials of this vaccine.