Warm-water piscine francisellosis is a granulomatous bacterial disease caused by Francisella orientalis (Fo). The disease has been detected in a wide range of fish species globally, causing mortalities as high as 90% and significant economic losses. Currently there are no commercially available vaccines and few treatment options exist. In the current study, two novel recombinant vaccines were prepared using diatom-expressed IglC or bacterial-expressed GroEL proteins. The vaccine antigens were emulsified with either nanoparticles or a commercially available oil-based adjuvant. Nile tilapia, Oreochromis niloticus, fingerlings were immunized intracoelomically (I.C.) with the recombinant IglC or GroEL vaccines, diatoms alone or phosphate buffer saline (PBS). Approximately 840-degree days post-vaccination, fish were challenged via immersion with 10⁶ CFU/mL of wild-type Fo. Twenty-one days post challenge (dpc), the highest relative percent survival (RPS) was recorded in the IglC-Montanide group (75%), compared to 53%, 50%, 22%, 19% and 16% in the IglC-nanoparticles, GroEL-Montanide, GroEL-nanoparticles, diatoms-Montanide and diatoms-nanoparticles groups, respectively. Protection correlated with significantly higher specific antibody responses in the IglC-Montanide group. Moreover, a significantly lower bacterial load was detected in spleen samples from the IglC-Montanide survivor tilapia compared to the other experimental groups. This is the first report of recombinant vaccines against piscine francisellosis in tilapia. The Fo vaccines described in our study may facilitate development of a safe, cost-effective and highly protective vaccine against francisellosis in farmed tilapia.

温水鱼francisellosis是引起的肉芽肿细菌性疾病弗朗西斯侧柏（佛）。该病已在全球范围广泛的鱼类中被发现，致死率高达90％，并造成重大经济损失。当前没有市售疫苗，并且几乎没有治疗选择。在当前的研究中，使用硅藻表达的IglC或细菌表达的GroEL蛋白制备了两种新型重组疫苗。用纳米颗粒或市售的油基佐剂乳化疫苗抗原。尼罗罗非鱼，尼罗罗非鱼，鱼苗用重组IglC或GroEL疫苗，单独的硅藻或磷酸盐缓冲液（PBS）进行腔内免疫（IC）。疫苗接种大约840天后，将鱼用10 ⁶  CFU / mL野生型Fo浸没来攻击。攻击后21天（dpc），IglC-Montanide组的相对存活率（RPS）最高（75％），而IglC组为53％，50％，22％，19％和16％ -纳米粒子，GroEL-Montanide，GroEL-纳米粒子，硅藻-Montanide和硅藻-纳米粒子组。在IglC-Montanide组中，保护与明显更高的特异性抗体反应相关。此外，与其他实验组相比，在IglC-Montanide幸存者罗非鱼的脾脏样品中检测到的细菌含量明显降低。这是针对罗非鱼中鱼败血症的重组疫苗的首次报道。该佛 我们的研究中描述的疫苗可能有助于开发一种安全，具有成本效益和高度保护性的疫苗，以应对养殖罗非鱼的囊肿病。