Distribution of ancient α1 and α2 domain lineages between two classical MHC class I genes and their alleles in grass carp

The antiviral efficacy of andrographolide against grass carp reovirus in vitro and in vivo

Grass carp reovirus (GCRV), which causes hemorrhagic disease in grass carp (Ctenopharyngodon idella), poses a significant threat to grass carp aquaculture. To develop effective treatments against GCRV infection, this study evaluated the antiviral efficacy of natural compounds derived from Chinese herbs on GCRV-infected grass carp kidney cells (CIK). Among the various compounds examined, in CIK cells, Andrographolide (Andro) at 25 mg/L exhibited the highest inhibition rates against GCRV-I and GCRV-II infections (83.27 % and 87.40 %, respectively). In vitro experiments showed that Andro significantly reduced the cytopathic effect, alleviated the apoptosis of GCRV-I-infected cells, inhibited the increase of mitochondrial membrane potential, and blocked CIK cell adsorption of GCRV-I and GCRV-II. Addition time studies revealed that Andro chiefly wielded its antiviral impact in the initial phase of viral replication (0-4 h). In vivo studies demonstrated that in both prevention and treatment experiments, 50 mg/kg Andro in the feed increased the survival rates of grass carp infected with GCRV-Ⅱ by 46.66 % and 40 %, respectively. Moreover, this compound significantly reduced the viral loads and upregulated antiviral gene expression in various organs, indicating its potential for immune modulation. In conclusion, Andro displayed significant antiviral properties that are effective to both prevent and treat GCRV infections, thus holding promise as a novel therapeutic agent for this virus.

Molecular polymorphism and expression of MHC I α, II α, II β and II invariant chain in the critically endangered Dabry's sturgeon (Acipenser dabryanus)

The major histocompatibility complex (MHC) is a key player in the regulation of immune responses through presenting foreign antigens to T lymphocytes. In this study, three MHC genes, namely, MHC I α, II α, II β and the II invariant chain (Ii), were identified and characterized in the critically endangered Dabry's sturgeon (Acipenser dabryanus). A tissue distribution study showed that the MHC and Ii transcripts were widely expressed in various tissues. The highest expression levels of MHC I α, II α and Ii were found in the gill, while MHC II β was primarily expressed in the spleen. Challenge of A. dabryanus with a pathogenic bacterium in vivo resulted in significant upregulation of both MHC and Ii expression, indicating potential roles of these genes in immune response. Phylogenetic analysis showed that A. dabryanus MHC grouped with other teleost MHC genes and sequences from Polyodon spathula and A. dabryanus had an intermingling of alleles. According to the split time between paddlefishes and sturgeons, this result indicated that trans-species MHC lineages in Chondrostei were much older than those in tetrapods. The molecular polymorphisms of the complete open reading frame regions of the MHC genes were analysed in several A. dabryanus individuals. MHC II α and II β were highly polymorphic in different individuals, while MHC I α was more conserved. The ratio of non-synonymous substitution occurred at a significantly higher frequency than synonymous substitution in peptide-binding regions (PBR) of MHC II α and II β, demonstrating the existence of positive selection at peptide-binding sites. Our study suggested potential roles of the MHC chains in immune response to pathogen microbial infection, and the numerous alleles identified in this study will help further genetic management and molecular marker-assisted selective breeding programmes in A. dabryanus.