Lc-pPG-612-OmpU-CTB: A promising oral vaccine for protecting Carassius auratus against Vibrio mimicus infection.

Vibrio mimicus (V. mimicus) is known to cause severe bacterial diseases with high mortality rates in fish, resulting in significant economic losses in the global aquaculture industry. Therefore, the objective of this study was to develop a safe and effective vaccine for protecting Carassius auratus (C. auratus) against V. mimicus infection. Recombinant Lactobacillus casei (L. casei) strains, Lc-pPG-612-OmpU and Lc-pPG-612-OmpU-CTB (surface-displayed), were constructed using a L. casei strain (ATCC 393) as an antigen delivery carrier and the cholera toxin B subunit (CTB) as an adjuvant. The two recombinant strains of L. casei were administered to C. auratus via oral immunization, and the protective efficacy of the oral vaccines was assessed. The results demonstrated that oral immunization with the two strains significantly increased the levels of nonspecific immune indicators in C. auratus, including alkaline phosphatase (AKP), lysozyme (LYS), acid phosphatase (ACP), complement 3 (C3), complement 4 (C4), lectin, and superoxide dismutase (SOD). Moreover, the experiment groups exhibited significant increases in specific immunoglobulin M (IgM) antibodies against OmpU, as well as the transcription of immune-related genes (ie., IL-1ß, TNF-α, IL-10, and TGF-ß), when compared to the control groups. Following infection of C. auratus with V. mimicus, the mortality rate of the recombinant L. casei-treated fish was observed to be lower compared to the control group. This finding suggests that recombinant L. casei demonstrates effective protection against V. mimicus infection in C. auratus. Furthermore, the addition of the immune adjuvant CTB was found to induce a more robust adaptive and innate immune response in C. auratus, resulting in reduced mortality after infection with V. mimicus.

Detection and genetic characterization of Toxoplasma gondii in market-sold mussels (Mytilus edulis) in certain provinces of China.

Mussels, randomly collected from fish markets in China, were analyzed by a semi-nested PCR to detect B1 gene of Toxoplasma gondii. Out of the 2215 samples, fifty-five (2.48%) were detected T. gondii-positive. The prevalence in Shandong province, Liaoning province and Zhejiang province were 2.51%, 2.26% and 2.69%, respectively. T. gondii oocysts were more frequently detected in digestive glands (1.04%) and haemolymph (1.49%) when compared with gills (0.23%). Of the 55 positive DNA, only two samples showed complete genotype at 11 locus and were authenticated as ToxoDB Genotype #9. To our knowledge, the present study is the first to confirm the presence of T. gondii in market-sold mussels in China. The findings point to the risk of humans acquiring T. gondii infection by consuming mussels bought in the aquatic product market.