Autophagy Is a Defense Mechanism Inhibiting Invasion and Inflammation During High-Virulent Haemophilus parasuis Infection in PK-15 Cells

Abstract

Bacterial infections activate autophagy and autophagy restricts pathogens such as <i>Haemophilus parasuis</i> through specific mechanisms. Autophagy is associated with the pathogenesis of <i>H. parasuis</i>. However, the mechanisms have not been clarified. Here, we monitored autophagy processes using confocal microscopy, western blot, and transmission electron microscopy (TEM) and found that <i>H. parasuis</i> SH0165 (high-virulent strain) but not HN0001 (non-virulent strain) infection enhanced autophagy flux. The AMPK/mTOR autophagy pathway was required for autophagy initiation and ATG5, Beclin-1, ATG7, and ATG16L1 emerged as important components in the generation of the autophagosome during <i>H. parasuis</i> infection. Moreover, autophagy induced by <i>H. parasuis</i> SH0165 turned to fight against invaded bacteria and inhibit inflammation. Then we further demonstrated that autophagy blocked the production of the cytokines IL-8, CCL4, and CCL5 induced by SH0165 infection through the inhibition of NF-κB, p38, and JNK MAPK signaling pathway. Therefore, our findings suggest that autophagy may act as a cellular defense mechanism in response to <i>H. parasuis</i> and provide a new way that autophagy protects the host against <i>H. parasuis</i> infection.