Abstract
BACKGROUND: B. mandrillaris is a free-living ameba that causes granulomatous amebic encephalitis (GAE), an infectious syndrome with a mortality rate of >90%. Treatment for GAE has been hampered by limited understanding of the molecular mechanisms of the pathogen and a lack of effective therapeutics. Recently, the quinolone nitroxoline (NTX) was identified in a drug screen as effective against B. mandrillaris, and successfully used to treat two US patients. [Figure: see text] [Figure: see text] METHODS: We used transcriptomics, growth assays, chemical complementation, cyst integrity assessments, and scanning electron microscopy to assess effects of NTX on B. mandrillaris. To support this work, we created a new draft B. mandrillaris genome, available at NCBI BioProject PRJNA1206197. [Figure: see text] RESULTS: Nitroxoline induced killing of B. mandrillaris was rescued by supplementation with copper and/or iron (Fig. 1). Nitroxoline treatment is associated with increased expression of DNA damage and repair genes (Fig. 2A), increased transposon transcription (Fig. 2B) and depressed global mRNA transcription (Fig. 2C), all consistent with parasite death. B. mandrillaris forms a tough, resistant cyst form under stress, but key encystment genes failed to upregulate in NTX-treated B. mandrillaris (Fig. 3A), and electron microscopy demonstrated disrupted cyst morphology in NTX-treated B. mandrillaris (Fig 3B). CONCLUSION: NTX sequesters iron and copper ions from B. mandrillaris, causing metabolic and genomic disarray, disrupting formation of the protective cyst, and ultimately leading to parasite death. These data contribute to a rational basis for including NTX in B. mandrillaris treatment regimens. Nitroxoline is now available for patients in the United States through an expanded-access Investigational New Drug protocol held by the Centers for Disease Control and Prevention. DISCLOSURES: All Authors: No reported disclosures