Flavobacterium psychrophilum (Fp) is the causative agent of bacterial cold water disease (BCWD) which causes appreciable economic losses in rainbow trout aquaculture. We previously reported development of a genetic line, designated ARS-Fp-R that exhibits higher survival relative to a susceptible line, designated ARS-Fp-S, following either laboratory or natural on-farm challenge. The objectives of this study were to determine the temporal kinetics of gene expression between experimentally-challenged ARS-Fp-R and ARS-Fp-S fish and the correlation between gene expression and pathogen load. We developed a GeXP multiplex RT-PCR assay to simultaneously examine expression of immune-relevant genes, concentrating on tumor necrosis factor and interleukin-1 ligand/receptor systems and acute phase response genes. Spleen tissue was sampled at 6 h, 24 h, 48 h and 144 h post-challenge and pathogen load quantified by qPCR. Transcript abundance of cytokine genes tnfa1, tnfa2, tnfa3, il1b1, il1b2, il11a; acute phase response genes saa and drtp1; and putative cytokine receptors il1r1-like-b, il1r2, tnfrsf1a, tnfrsf9, tnfrsf1a-like-b increased following challenge while the transcript abundance of il1r-like-1 and tnfrsf1a-like-a decreased compared to PBS-injected line-matched control fish. Principal component analysis identified transcript levels of genes il1r-like-1 and tnfrsf1a-like-a as exhibiting differential expression between genetic lines. In summary, Fp i.p. injection challenge elicited a proinflammatory cytokine gene expression response in the spleen, with ARS-Fp-R line fish exhibiting modestly higher basal expression levels of several putative cytokine receptors. This study furthers the understanding of the immune response following Fp challenge and differences in gene expression associated with selective breeding for disease resistance.
Alveolar echinococcosis caused by Echinococcus multilocularis is an important zoonotic disease. In the infected mice, emu-miR-4989-3p is present in sera, but its role remains unknown. Using high-throughput sequencing and qPCR, emu-miR-4989-3p was herein confirmed to be encapsulated into E. multilocularis extracellular vesicles. In the transfected macrophages, emu-miR-4989-3p was demonstrated to significantly inhibit NO production compared to the control (p < 0.05). Moreover, transfection of emu-miR-4989-3p also gave rise to the increased expression of TNF-α (p < 0.01). Furthermore, emu-miR-4989-3p induced the dysregulation of several key components in the LPS/TLR4 signaling pathway compared with the control, especially TLR4 and NF-κB that both were upregulated. Conversely, the NO production and the expression of TNF-α, TLR4 and NF-κB tended to be increased and decreased in the mimics-transfected cells upon emu-miR-4989-3p low expression, respectively. These results suggest that emu-miR-4989-3p is one of ‘virulence’ factors encapsulated into the extracellular vesicles, potentially playing a role in the pathogenesis of E. multilocularis.
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