Poxvirus A52 is a host range factor for modified vaccinia virus Ankara (MVA) and promotes viral replication by disturbing the formation of autolysosomes

Many members of the poxvirus family are important zoonotic pathogens that pose a significant threat to human and animal health worldwide. Autophagy is a multi-step degradation pathway within cells, and one of its primary biological functions includes the clearance of invading viruses. Nevertheless, the interplay between poxviruses and host cell autophagy has not been fully elucidated. Here, we demonstrate that vaccinia virus (VACV) and lumpy skin disease virus (LSDV) induce incomplete autophagy and inhibit the fusion of autophagosomes and lysosomes, while modified vaccinia virus Ankara (MVA), an attenuated strain of VACV unable to replicate in almost all human cells, does not. Additionally, we screened and identified the VACV protein A52 as a key factor that obstruct the formation of autolysosomes. Mechanistically, A52 interacts with SNAP29 and inhibits its interaction with STX17 and VAMP8, both of which are binding partners of SNAP29 and are essential for complete autophagy. Moreover, A52 promotes the proteasomal degradation of SNAP29, which facilitates viral replication. We further revealed that SNAP29 functions as a restriction factor for MVA, as the suppression of SNAP29 allowed the replication of MVA in human cells. In summary, our data present a molecular mechanism by which poxviruses manipulate the cellular autophagic machinery and provide additional explanation for the restriction of MVA in human cells.