Developmental and comparative immunology最新文献

ADP-ribosylation factor 6 (Arf6) is a small GTPase that coordinates membrane trafficking and cytoskeletal dynamics, processes essential for innate immune responses. However, its specific role in crustacean immunity remains largely unexplored. In this study, an Arf6 homolog from the Chinese mitten crab (Eriocheir sinensis), designated EsArf6, was identified and functionally characterized. EsArf6 encodes a 175-amino-acid protein that is highly conserved across vertebrate and invertebrate species. Quantitative real-time PCR analysis revealed that EsArf6 is ubiquitously expressed in crab tissues, with highest transcript levels detected in hemocytes and hepatopancreas. Following challenge with either Staphylococcus aureus or Vibrio parahaemolyticus, EsArf6 expression was significantly upregulated in hemocytes in a time-dependent manner. Functional analyses demonstrated that RNA interference (RNAi)-mediated silencing of EsArf6 markedly reduced the phagocytic capacity of hemocytes toward both Gram-positive and Gram-negative bacteria in vitro. Consistently, in vivo knockdown of EsArf6 resulted in elevated bacterial loads in the hemolymph and significantly decreased host survival following bacterial infection. These findings indicate that EsArf6 is required for efficient antibacterial defense in E. sinensis, primarily through the regulation of hemocyte-mediated phagocytosis. Overall, this study provides new insight into the conserved role of Arf6 in invertebrate innate immunity and expands current understanding of immune regulatory mechanisms in crustaceans.

As the primary defense against pathogen invasion, the dynamic equilibrium of the shrimp gut microbiome is recognized as a critical factor influencing pathogen colonization. In recent years, translucent post-larva disease (TPD) outbreaks during the early stages of shrimp farming have become a serious threat to the sustainable development of the shrimp industry. Compared with other vibriosis, TPD caused by certain Vibrio strains possessing drug resistance and high-virulence genes exhibits greater virulence in shrimp tissues, with mortality rates reaching up to 90%. However, no studies have yet explored the association between this pathogen and the gut microbiome. This study employed metagenomic sequencing technology to analyze differences in the axial distribution of the gut microbiome in shrimp at varying degrees of TPD infection. Histopathological sections revealed that multiple tissue lesions induced by TPD infection in shrimp were primarily concentrated in the midgut. Alpha diversity analysis indicated that the alpha diversity index of the shrimp gut microbiome showed an upward trend as pathogen load increased. Beta diversity analysis revealed the intestinal segment with the most significant microbial community changes during pathogen colonization. Within this region, the abundance of probiotics decreased, while that of pathogenic bacteria increased. Functional prediction results indicate that under TPD stress, the gut microbiome activates a multi-layered, synergistic defense adaptation program through nutritional metabolism shifts, biofilm reinforcement, and toxin efflux. This study elucidates the pathogenic mechanism of TPD from the perspective of pathogen-gut microbiome interactions, suggesting that controlling pathogen load and restoring targeted probiotics may serve as effective strategies for preventing and controlling TPD.

Highly pathogenic avian influenza (HPAI) virus outbreaks in poultry farming impose a substantial economic burden and present a significant threat to animal welfare, with the H5N1 subtype representing a potential candidate for a future pandemic strain. Advancing the current understanding of the host immune response and viral dynamics following HPAI H5N1 infection is critical for improving prevention and treatment strategies. Using the chicken embryo fibroblast DF-1 cell line, this study aimed to investigate the initial cell-intrinsic innate immune response and corresponding viral transcription following challenge with HPAI H5N1 through RNA sequencing. Significant enrichment of genes associated with interferon signalling and the p53 pathway was observed at four and 8 h post infection, with sustained upregulation of interferon regulatory factor 1 (chIRF1) observed throughout the time course. Leveraging this finding, the proximal promoter region of chIRF1 was functionally characterised to investigate its transcriptional regulation following exposure to viral stimuli. Motif-based analysis identified putative regulatory elements within the -200 bp proximal promoter region, including an NF-κB binding motif, an gamma interferon-activated site (GAS), a CCAAT box, and several GC boxes. Luciferase reporter assays employing 5' deletion constructs and targeted disruption of the GAS element demonstrated that this motif is required for full induction of the chIRF1 promoter in response to poly(I:C) stimulation and HPAI H5N1infection.

As a key therapeutic target for various diseases, Cyclophilin A (CypA) exhibits a dual nature in its biological functions. While the molecular mechanisms underlying its role in antiviral immunity have been well elucidated in vertebrates, research in invertebrates has merely been limited to expression responses induced by pathogens, and the underlying mechanisms through which CypA mediates immune regulation remain to be urgently deciphered. In this study, CypA expression was up-regulated in red swamp crayfish (Procambarus clarkii) following infection with white spot syndrome virus (WSSV). Functional analysis showed that CypA promote WSSV replication and reduce the survival rate of crayfish post-infection. Co-immunoprecipitation (Co-IP) assays showed that CypA interacted with WSSV VP28. Further studies have found that CypA inhibited the activity of transcription factor Dorsal, and then down-regulated the expression levels of Lysozyme-i1 (Lys-i1) and Lys-i2. Lys-i2 effectively inhibited WSSV replication and improved the survival of crayfish after WSSV infection. Pulldown and Co-IP assays confirmed the interaction between Lys-i2 and WSSV VP28. Collectively, these results suggest that WSSV hijacks CypA to inhibit Dorsal activity, thereby suppressing lysozyme expression and evading the host immune response in P. clarkii.

White spot syndrome virus (WSSV) severely threatens the sustainable cultivation of Procambarus clarkii and causes substantial economic losses. To develop safe strategies for controlling WSSV, the present study evaluated the protective effects and underlying mechanisms of baicalein in WSSV-infected P. clarkii. P. clarkii were randomly allocated into four experimental groups: Control (C), Baicalein immersion (B), WSSV infected (W), and WSSV infected plus Baicalein immersion (WB) for a 14-day experimental period. Intestinal microbiota, intestinal histopathology, and hepatopancreatic antioxidant enzyme activities were analyzed to evaluate baicalein's protective effects. WSSV infection exerted severe adverse effects on P. clarkii: the survival rate significantly decreased to 64.89%, intestinal microbiota composition was perturbed with decreased relative abundance of Proteobacteria and increased Bacteroidota, pathogenic taxa such as Bacteroides and Vibrio proliferated, intestinal epithelial exfoliation occurred, and hepatopancreatic antioxidant function was impaired with reduced GPX/CAT activities and elevated MDA content. Notably, 2.5 mg/L baicalein immersion mitigated these WSSV-induced adverse effects: the survival rate increased to 73.33%, intestinal microbiota composition was restored with increased Proteobacteria and decreased Bacteroidota, pathogenic taxa such as Bacteroides were inhibited, intestinal damage was alleviated, and hepatopancreatic antioxidant capacity was partially enhanced by targeting the T-SOD and GSH pathways, whereas GPX and CAT activities remained unaffected. Collectively, baicalein protects P. clarkii against WSSV through a "microbiota-immune-antioxidant axis" synergistic mechanism.

Cathelicidins, a diverse family of host defence peptides (HDPs) in vertebrates, are recognized for their potential in combating resistant microorganisms and their varied biological functions. While extensive studies have focused on mammalian cathelicidins, those in reptiles remain largely unexplored. In this study, we conducted a genome mining analysis that identified 287 cathelicidin genes across reptilian orders Testudines and Squamata. Of these genes, we identified 219 complete cathelicidin protein sequences and 68 cathelicidin-like gene copies that appear to be pseudogenes or gene fragments lacking intact open reading frames. We established for the first time a classification for reptile cathelicidins of the cited orders based on their sequence and structure, observing six types for Testudines and six for Squamata, suggesting a common ancestral lineage. Furthermore, we investigated the genomic arrangement of these cathelicidin genes, uncovering that they are grouped into clusters with variability in the gene number and in their organization. Cathelicidin derived mature peptides were classified into nine groups based on their sequences and physicochemical properties. This comprehensive study enhances the understanding of the cathelicidin family in reptiles, clarifying their genomic organization and describing the different types present. These classifications pave the way for future studies on the functions and specialization of each identified cathelicidin group. Moreover, they enable potential structure-activity studies of the peptides, establishing a foundation for differentiating their key features.