Mycobacterium PPE31 Contributes to Host Cell Death

Genome scale mutagenesis identifies many genes required for mycobacterial infectivity and survival, but their contributions and mechanisms of action within the host are poorly understood. Using CRISPR interference, we created a knockdown of ppe31(Mm) gene in Mycobacterium marinum (M. marinum), which reduced the resistance to acid medium. To further explore the function of PPE31, the ppe31 mutant strain was generated in M. marinum and Mycobacterium tuberculosis (M. tuberculosis), respectively. Macrophages infected with the ppe31(Mm) mutant strain caused a reduced inflammatory mediator expressions. In addition, macrophages infected with M. marinum Δppe31(Mm) had decreased host cell death dependent on JNK signaling. Consistent with these results, deletion of ppe31(Mtb) from M. tuberculosis increased the sensitivity to acid medium and reduced cell death in macrophages. Furthermore, we demonstrate that both ppe31 mutants from M. marinum and M. tuberculosis resulted in reduced survival in macrophages, and the survivability of M. marinum was deceased in zebrafish due to loss of ppe31(Mm). Our findings confirm that PPE31 as a virulence associated factor that modulates innate immune responses to mycobacterial infection.