Characterization and expression of macrophage migration inhibitory factor (mif) in Chinese sturgeon (Acipenser sinensis).

The Chinese sturgeon (Acipenser sinensis) is one of the critically endangered aquatic species in China. It is also among the oldest extant actinopterygian fish species. To advance the characterization of the Chinese sturgeon immune system, we identified the gene encoding the macrophage migration inhibitory factor (MIF), a multifunctional cytokine that contributes to both innate and adaptive immune responses. Molecular and phylogenic analysis indicates the Chinese sturgeon (cs) MIF share a high degree of structural conservation with other MIF sequences and is closely related to other bony fish MIF. At steady state, cs-mif gene is expressed at relatively high levels in the brain, and to a lesser but significant level in liver, spleen, kidney, gut and skin. The spatial expression patterns determined by in situ hybridization indicates a preferential distribution of cs-mif transcripts in the cerebral cortex, the gut epithelium, hematopoietic tissues of kidney, spleen and liver parenchyma, and skin epidermis. Marked increase of cs-mif gene expression was induced by lipopolysaccharide (LPS) stimulation and Aeromonas hydrophila infection in all tested tissues. Furthermore, higher cs-mif transcript levels were detected in the liver, spleen, kidney, gut and skin during stress response resulting from hyperthermia. These results are not only consistent with the expected role of cs-mif gene in innate immunity but also suggest a potential role of this gene in stress response to hyperthermia in the Chinese sturgeon.

Proliferation dynamics of WSSV in crayfish, Procambarus clarkii, and the host responses at different temperatures.

The replication profile of white spot syndrome virus (WSSV) in crayfish, Procambarus clarkii, at different water temperature was investigated in this study. The WSSV detections were negative at 15 ± 1°C, and the natural infection ratio increased at 19 ± 1°C (24.2% ± 2.25%), reached 100% at 25 ± 1°C and decreased at 30 ± 1°C (93.2% ± 3.37%). The WSSV genome copies number was much higher at 25 ± 1°C (≥5 × 106.45 ± 0.35 /mg) than at 15 ± 1°C (≤5 × 101.13 ± 0.12 /mg), 19 ± 1°C (≤5 × 102.74 ± 0.48 /mg) and 32 ± 1°C (≤5 × 103.18 ± 0.27 /mg). Meanwhile, the significant transcription signals of immediate early gene ie1 and late gene vp28 and a large number of virus particles were detected in epitheliums of stomach, gut and gill, hepatopancreas, heart and muscle cells at 25 ± 1°C by using in situ hybridization (ISH) and transmission electron microscopy. The experimental infection of P. clarkii with WSSV infection showed reduced mortality and lower virus copies number at 19 ± 1°C (23.51% ± 0.84%, ≤5 × 103.41 ± 0.11 /mg) and 32 ± 1°C (38.42% ±  1.21%, ≤5 × 103.72 ± 0.13 /mg) compared to 25 ± 1°C (100%, ≥5 × 104.99 ± 0.24 /mg). The water temperature regulated the transcription of immune-related genes (crustin2, prophenoloxidase (proPO) and heat shock protein70 (Hsp70)), with some differences between WSSV treatments and control treatments. These results demonstrate that water temperature has effect on WSSV proliferation, which may due to transcriptional response of immune-related genes to temperature.