Abstract：Mycobacteriosis, caused by Mycobacterium species, affects nearly 160 fish species worldwide, including several species of sturgeon. It is difficult to detect this disease in the early stage of infection. In addition, there is no effective drug for treatment of the disease in the event of an outbreak. Therefore, an effective vaccine is urgently required. In this study, we evaluated the effects of two candidate vaccines in Dabry's sturgeon, namely, bacillus Calmette-Guérin (BCG) and formalin-killed cells of M.ulcerans ecovar Liflandii (MuLiflandii ASM001; FKC). Dabry's sturgeon injected with sterile phosphate-buffered saline (PBS) was used as a control. The vaccinated individual fish was challenged with MuLiflandii ASM001 to analyze the immunization efficacy of the vaccine. The cumulative mortality of PBS-injected, FKC and BCG vaccinated groups were 8.3%, 3.3%, and 6.7%, respectively. The relative percentage survival of the FKC-vaccinated group reached 60.2%, of the BCG-vaccinated group reached 19.3%. The histopathological assay with Ziehl–Neelsen staining showed that specimens of muscle and middle kidney tissues from the PBS group were positive for acid-fast bacilli. A total of 77,800 unigenes were assembled for transcriptome sequencing, with an average length of 1117 bp. In FKC/PBS and BCG/PBS pairwise comparisons, 1789 and 68 differentially expressed genes (DEGs) were detected, respectively. Twenty-six immune-related genes were differentially expressed among the three different treatment groups. The sequences of the DEGs were annotated and their enrichments were analyzed with Kyoto Encyclopedia of Genes and Genomes and Gene Ontology. FKC/PBS pairwise comparison revealed that the DEGs were significantly enriched in three immune-related pathways: “phagocytosis”,“antigen processing and presentation”, and “complement and coagulation cascades”. These data suggested that this inactivated vaccine induced an innate immune response to MuLiflandii ASM001 infection and may, therefore, be a potential candidate vaccine.

J. Huang, H. Zhang, J. Di, H. Du, Q.W. Wei*. Inactivated Mycobacterium vaccine induces innate immunity against M. ulcerans ecovar Liflandii (MuLiflandii ASM001) infection in Dabry’s sturgeon (Acipenser dabryanus). Aaquaculture, 512: 734312.