Mai Thao Thu, Kayansamruaj Pattanapon, Soontara Chayanit, Kerddee Pattarawit, Nguyen Dinh-Hung, Senapin Saengchan, Costa Janina Z, Del-Pozo Jorge, Thompson Kim D, Rodkhum Channarong, Dong Ha Thanh
Center of Excellence in Fish Infectious Diseases (CE FID), Department of Veterinary Microbiology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand.
The International Graduate Program of Veterinary Science and Technology (VST), Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand.
Vaccines (Basel). 2022 Jan 21;10(2):167. doi: 10.3390/vaccines10020167.
Tilapia lake virus (TiLV), a major pathogen of farmed tilapia, is known to be vertically transmitted. Here, we hypothesize that Nile tilapia () broodstock immunized with a TiLV inactivated vaccine can mount a protective antibody response and passively transfer maternal antibodies to their fertilized eggs and larvae. To test this hypothesis, three groups of tilapia broodstock, each containing four males and eight females, were immunized with either a heat-killed TiLV vaccine (HKV), a formalin-killed TiLV vaccine (FKV) (both administered at 3.6 × 10 TCID per fish), or with L15 medium. Booster vaccination with the same vaccines was given 3 weeks later, and mating took place 1 week thereafter. Broodstock blood sera, fertilized eggs and larvae were collected from 6-14 weeks post-primary vaccination for measurement of TiLV-specific antibody (anti-TiLV IgM) levels. In parallel, passive immunization using sera from the immunized female broodstock was administered to naïve tilapia juveniles to assess if antibodies induced in immunized broodstock were protective. The results showed that anti-TiLV IgM was produced in the majority of both male and female broodstock vaccinated with either the HKV or FKV and that these antibodies could be detected in the fertilized eggs and larvae from vaccinated broodstock. Higher levels of maternal antibody were observed in fertilized eggs from broodstock vaccinated with HKV than those vaccinated with FKV. Low levels of TiLV-IgM were detected in some of the 1-3 day old larvae but were undetectable in 7-14 day old larvae from the vaccinated broodstock, indicating a short persistence of TiLV-IgM in larvae. Moreover, passive immunization proved that antibodies elicited by TiLV vaccination were able to confer 85% to 90% protection against TiLV challenge in naïve juvenile tilapia. In conclusion, immunization of tilapia broodstock with TiLV vaccines could be a potential strategy for the prevention of TiLV in tilapia fertilized eggs and larvae, with HKV appearing to be more promising than FKV for maternal vaccination.
罗非鱼湖病毒（TiLV）是养殖罗非鱼的主要病原体，已知可垂直传播。在此，我们假设用TiLV灭活疫苗免疫的尼罗罗非鱼（）亲鱼能够产生保护性抗体反应，并将母源抗体被动转移至其受精卵和幼鱼。为验证这一假设，将三组罗非鱼亲鱼（每组包含4尾雄鱼和8尾雌鱼）分别用热灭活TiLV疫苗（HKV）、福尔马林灭活TiLV疫苗（FKV）（均按每尾鱼3.6×10 TCID给药）或L15培养基进行免疫。3周后用相同疫苗进行加强免疫，此后1周进行交配。在初次免疫后6至14周收集亲鱼血清、受精卵和幼鱼，以测定TiLV特异性抗体（抗TiLV IgM）水平。同时，将免疫雌亲鱼的血清用于对未免疫的罗非鱼幼鱼进行被动免疫，以评估免疫亲鱼诱导产生的抗体是否具有保护作用。结果显示，接种HKV或FKV的大多数雄、雌亲鱼均产生了抗TiLV IgM，且在接种亲鱼的受精卵和幼鱼中均可检测到这些抗体。与接种FKV的亲鱼相比，接种HKV的亲鱼所产受精卵中的母源抗体水平更高。在一些1至3日龄的幼鱼中检测到低水平的TiLV-IgM，但在接种亲鱼的7至14日龄幼鱼中未检测到，这表明TiLV-IgM在幼鱼中的持续时间较短。此外，被动免疫证明，TiLV疫苗接种诱导产生的抗体能够为未免疫的罗非鱼幼鱼提供85%至90%的TiLV攻毒保护。总之，用TiLV疫苗免疫罗非鱼亲鱼可能是预防罗非鱼受精卵和幼鱼感染TiLV的一种潜在策略，对于母源免疫而言，HKV似乎比FKV更具前景。
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