Acid sphingomyelinase is essential for vacuolar development of A. phagocytophilum.

Obligate intracellular bacteria are significant causes of morbidity and mortality with over two hundred and fifty million infections worldwide annually. One such bacterium, Anaplasma phagocytophilum is the etiologic agent of human granulocytic anaplasmosis (HGA), a tick-transmitted febrile illness. Previous studies have shown that A. phagocytophilum lacks genes for cholesterol biosynthesis and solely relies on Niemann Pick protein type C (NPC)1-mediated low density lipoprotein (LDL)-derived cholesterol to complete its infection cycle.Acid sphingomyelinase (ASMase) is a lysosomal enzyme that is essential for diverse cellular processes including liberation of LDL-derived cholesterol from the lysosome. By first studying A. phagocytophilum, we found that functional inhibitors of acid sphinogmyelinase (FIASMAs) arrest the bacterium’s infection cycle in a dose-dependent manner. FIASMAs inhibit vacuole maturation, conversion to the infectious form, and eliminate the production of infectious progeny. NPC1-mediated LDL-derived cholesterol traffic to the ApV is abrogated in the presence of FIASMAs. Similar to the in vitro model, A. phagocytophilum cannot establish a productive infection in both ASMase-/-and FIASMA treated mice. Furthermore, we extended our studies to Coxiella burnetti (Q fever), and Chlamydia spp. (STD, infectious blindness, pneumonia). FIASMA treatment has a rapid bacteriocidal effect on C. burnettiwithin host cells. Additionally, FIASMA treatment inhibits C. trachomatis and C. pneumoniae inclusion expansion and infectious progeny generation, with C. pneumoniae being more severely impacted. These data highlight the critical, yet distinct roles that ASMase plays in these pathogens’ infection cycles. Furthermore, these results signify the therapeutic potential of FIASMAs for treating diseases caused by these pathogens