Overexpression of EspL inhibits autophagy and antigen presentation to promote the intracellular survival of Mycobacterium tuberculosis avirulent strains

Mycobacterium tuberculosis (Mtb) employs multiple mechanisms, such as phagocytosis and autophagy, to evade innate immune clearance and establish infection. In the present study, we identified the ESX-1 secretion-associated protein EspL, which promotes Mtb survival by inhibiting phagosome maturation and autophagy initiation. EspL knockout decreased Mtb intracellular survival, while EspL overexpression increased bacterial survival by interfering with phagocytosis and autophagy. EspL interacts with ULK1 and promotes its phosphorylation at Ser(757), leading to the inhibition of autophagy initiation. Additionally, overexpression of EspL reduced antigen presentation and T-cell responses both in vitro and in vivo. Our findings revealed that EspL interferes with autophagy and antigen presentation by suppressing ULK1 activation. These insights provide a novel understanding of Mtb pathogenicity.