大菱鲆抗鳗弧菌急性感染家系的筛选和免疫表达分析

    Screening of acute Vibrio anguillarum-resistant turbot (Scophthalmus maximus) families and integrated immune expression profiling

    • 摘要:背景】鳗弧菌(Vibrio anguillarum)是大菱鲆(Scophthalmus maximus)的重要病原,其发病迅速,致死率高。感染鳗弧菌的大菱鲆幼苗在2~3 d内的死亡率可达80%以上,严重影响了大菱鲆养殖产业的发展。【目的】筛选出大菱鲆抗鳗弧菌免疫相关基因和抗病家系。【方法】本研究选取8个不同家系(A~H)的大菱鲆,通过人工感染实验,比较不同家系感染鳗弧菌后的成活率,并分析12个大菱鲆免疫相关基因(il-mxnkeftnf-αil8rtlr5mhc-mhc-IgMtcrcd4cd8)和3个免疫因子补体C3(C3)、溶菌酶(LZM)和酸性磷酸酶(ACP)在鳗弧菌感染前期的作用。【结果】攻毒结果显示,大部分感染鳗弧菌的大菱鲆在2~3 d内死亡;在感染10 d后,A家系生存率为13.15%,G家系生存率为10.52%,其余家系全部死亡。免疫因子测定结果显示,在攻毒24 h时,D、F家系补体C3含量显著升高(P<0.05),A、G家系ACP活性显著升高(P<0.05)。免疫相关基因实时荧光定量-聚合酶链式反应(qRT-PCR)结果显示,在攻毒24 h后,A家系tnf-αtlr5tcrcd4cd8基因显著上调,其中tlr5基因上调约7倍,cd8基因上调约20倍;G家系mxtnf-αtlr5tcrcd4cd8基因显著上调,其中tlr5基因上调约2倍,tcr基因上调约8倍。整体来说,攻毒后A、G家系免疫系统强协同响应,预示其能快速识别病原、募集免疫细胞并启动特异性杀伤;结合攻毒后两家系的群体存活率结果来看,A、G家系对鳗弧菌感染的抵抗能力最强,可作为鳗弧菌的高抗病潜力家系。C、E家系il-tcrcd8基因显著上调,F家系补体C3含量和il-mxtnf-α基因显著上调,H家系il-tlr5tnf-α基因显著上调,但其他通路(如il8r、cd4)应答平缓,免疫激活呈现局部通路优势;在鳗弧菌感染前期,C、E和F家系依赖单一、局部通路抵御感染,其免疫应答的广度与深度弱于A、G家系,推测其对鳗弧菌的抗病性为中度。B、D家系在攻毒后仅少数基因(如D家系il-)微弱响应,免疫通路激活整体滞后,对鳗弧感染的抵抗力最弱。【结论】综上所述,A、G家系更适合作为抗鳗弧菌急性感染的家系群体,并从这些家系中初步筛选出6个对鳗弧菌感染较为敏感的免疫基因(mxtnf-αtlr5tcrcd4cd8),并可作为大菱鲆抗鳗弧菌家系选育的标记基因,为选育大菱鲆抗性品种提供理论数据。

       

      Abstract: Background Vibrio anguillarum is a significant pathogen of turbot (Scophthalmus maximus), characterized by rapid disease progression and high mortality rates. Infection in juvenile turbot can result in mortality exceeding 80% within 2-3 days, posing a severe threat to the turbot aquaculture industry. Objective Screening protocol development for Edwardsiellosis resistance in S. maximus pedigrees.Methods This study selected eight different families of turbot (S. maximus) (A-H) and compared their survival rates after artificial infection with V. anguillarum. Additionally, the roles of 12 immune-related genes (il-, mx, tnf-α, tnf-α, il8r, tlr5, mhc-, mhc-, IgM,tcr, cd4, cd8) and three immune factors (complement C3, LZM, ACP) in the early stages of V. anguillarum infection were analyzed. Results The pathogen challenge results revealed that the majority of infected fish died within 2-3 days. By 10 days post-infection with V. anguillarum, Family A exhibited a survival rate of 13.15%, Family G showed 10.52% survival, while all other families suffered complete mortality. Immunological factor analysis demonstrated that at 24 hours post-challenge: Families D and F showed significant increases in complement C3 levels (P<0.05). Families A and G displayed significantly elevated acid phosphatase (ACP) activity (P<0.05). qRT-PCR analysis of immune-related genes at 24 hours post-challenge showed followings, Family A: Significant upregulation of tnf-α, tlr5, tcr, cd4, and cd8, with tlr5 showing 7-fold increase and cd8 exhibiting 20-fold increase; Family G: Marked upregulation of mx, tnf-α, tlr5, tcr, cd4 and cd8, with tlr5 increasing 2-fold and tcr rising ~8-fold. In summary, the robust synergistic response of the immune systems in pedigrees A and G following challenge suggests their capacity to swiftly recognize pathogens, recruit immune cells, and initiate specific cytotoxicity. Integrating with the group survival rate data post-challenge, pedigrees A and G exhibit the highest resistance to V anguillarum infection, qualifying them as high disease-resistant potential pedigrees against V anguillarum. For pedigrees C and E, significant upregulation of il-, tcr, and cd8 was observed; pedigree F showed notable elevation in C3 content, il-, mx,and tnf-α; pedigree H presented significant upregulation of il-, tlr5, and tnf-α genes. However, other pathways (e.g., il8r, cd4) displayed mild responses, indicating that immune activation in these pedigrees was characterized by local pathway dominance. Relying on single or local pathways to combat infection during the early stage of V anguillarum challenge, these pedigrees exhibited immune responses with narrower breadth and shallower depth compared to pedigrees A and G, suggesting moderate disease resistance to V anguillarum. Pedigrees B and D showed only feeble responses in a few genes (e.g., il- in pedigree D) post-challenge, with overall delayed activation of immune pathways, demonstrating the lowest resistance to V anguillarum infection. Conclusion In conclusion, Families A and G demonstrate superior suitability as candidate populations for resistance against acute V. anguillarum infection. Through this study, we have preliminarily identified six immune resistance-related genes (mx, tnf-α, tlr5, tcr, cd4, cd8) that show particular sensitivity to V. anguillarum infection in these families. These genes may serve as valuable molecular markers for selective breeding of V. anguillarum-resistant turbot (S. maximus) strains, providing critical theoretical data to support the development of disease-resistant varieties in aquaculture.

       

    /

    返回文章
    返回