可诱导驯化免疫的屎肠球菌分离筛选及其抗感染效果评价

Isolation, screening, and anti-infectious evaluation of Enterococcus faecium capable of inducing trained immunity

摘要:

【背景】天然免疫应答作为机体的第一道免疫防御屏障，在动物抵抗病原微生物感染的初始阶段发挥着关键作用。从驯化免疫的角度，增强动物天然免疫，提高动物抗病能力是预防控制疾病的有效措施。【目的】从猪肠道菌群中筛选分离具有潜在驯化免疫作用的细菌，为挖掘新的免疫刺激物奠定基础。【方法】从健康猪粪便中分离纯化细菌，选择大蜡螟(Galleria mellonella)幼虫驯化免疫模型用于筛选肠道共生菌，对有潜在驯化免疫功能的细菌进行16S rRNA基因序列鉴定和生长曲线的测定，并利用小鼠模型对细菌进行体内驯化效果评价。【结果】通过使用大蜡螟幼虫模型，我们筛选出了一株具有诱导驯化免疫能力的屎肠球菌(Enterococcus faecium) SC-2；通过小鼠模型进一步证实菌株SC-2预刺激可以提高小鼠外周血与肺脏中的中性粒细胞和巨噬细胞占比，显著降低猪链球菌(Streptococcus suis)感染后其主要脏器中的菌载量，显著提高小鼠存活率。【结论】屎肠球菌SC-2具有诱导驯化免疫的作用，该菌株的分离鉴定为免疫调控新成分的挖掘提供了基础。

关键词:屎肠球菌;驯化免疫;大蜡螟;分离鉴定

Abstract:

[Background] The innate immune system is the first defense line and plays a key role in the host defense against microbial early infection. Enhancing the innate immunity from trained immunity is an effective way to improve the resistance of animals to diseases. [Objective] To isolate the bacteria capable of inducing trained immunity from healthy porcine intestinal flora and thus provide new insights for the prevention and control of microbial diseases by trained immunity. [Methods] Bacteria were isolated from healthy pig feces, and the strains capable of inducing trained immunity were screened with Galleria mellonella, a well-established model. The strain screened out was identified by 16S rRNA gene sequencing and characterized by growth curve. Its capability of inducing trained immunity was then evaluated in a mouse model. [Results] A strain SC-2 capable of inducing trained immunity in G. mellonella was identified as Enterococcus faecium. Administration of SC-2 significantly increased the percentages of neutrophils and macrophages in the peripheral blood and lung, decreased the bacteria loads in main organs, and increased the survival rate of mice infected by Streptococcus suis. [Conclusion] SC-2 had the effect of inducing trained immunity in mice. Our study provides new insights for immune regulation and disease treatment from the perspective of trained immunity.

Key words:Enterococcus faecium;trained immunity;Galleria mellonella;isolation and identification