Outer membrane vesicles secreted by avian pathogenic Escherichia coli promote intracellular survival in macrophages and systemic infection by regulating mitophagy through the MSTRG.11745.1/gga-miR-15b-5p/TNFAIP3 axis.

Avian pathogenic Escherichia coli (APEC) is a major extraintestinal pathogen responsible for severe systemic infections in poultry. It evades the immune system and establishes persistent infection by hijacking macrophages as its primary site of intracellular survival. During the pathogenic process, outer membrane vesicles (OMVs) secreted by APEC serve as key carriers for the delivery of virulence factors to host cells. However, the specific mechanisms by which OMVs disrupt macrophage defence mechanisms and promote the intracellular survival of APEC have not yet been fully elucidated. We demonstrated that APEC OMVs disrupt the mitochondrial structure of chicken macrophages (HD11) and lead to the collapse of the mitochondrial membrane potential. This injury-induced mitophagy contributes to a reduction in stress-related ROS levels, thereby promoting the intracellular survival of APEC and systemic infection. Furthermore, intervention with a mitophagy inhibitor significantly reduced the extent of intracellular survival resulting from mitophagy (P < 0.01) as well as the bacterial load in chick tissues (trachea: P < 0.001; lung: P < 0.001; liver: P < 0.001; spleen: P < 0.01). Furthermore, We identified a novel lncRNA-MSTRG.11745.1-associated with mitophagy through transcriptomic screening, and upregulated MSTRG.11745.1 acts as a competitive endogenous RNA (ceRNA), binding to gga-miR-15b-5p to regulate the TNFAIP3 expression, thereby promoting mitophagy and the intracellular survival of APEC. In summary, APEC-derived OMVs induce severe mitochondrial damage in host macrophages. They also activate the MSTRG.11745.1/gga-miR-15b-5p/TNFAIP3 ceRNA axis and promote mitophagy. This process contributes to APEC immune evasion and systemic infection. This study provides new insights into the core mechanisms by which OMVs enable APEC to evade innate immune surveillance by macrophages.