Ornithine Decarboxylase as a Therapeutic Target in Leishmania: From Mechanism to Application - Project Summary/Abstract Leishmaniasis, a neglected tropical disease caused by Leishmania parasites, poses a significant global health burden, with over 12 million people currently affected, more than one billion at risk, and few treatment options available. Existing therapies are limited by toxicity, rising drug resistance, and the lack of a vaccine, underscoring the urgent need for safer, more effective interventions. This project targets parasite polyamine metabolism, an essential but underexplored pathway, as a foundation for novel therapeutic strategies. Our long-term goal is to understand how polyamines influence parasite function and resilience and to leverage this knowledge to develop combination treatments that improve clinical outcomes. Our prior work demonstrated that deletion of ornithine decarboxylase (∆odc) or spermidine synthase (∆spdsyn), two key enzymes in polyamine biosynthesis, severely impairs parasite survival and infectivity. Building on these findings, we propose three aims that integrate basic discovery with translational potential. In Aim 1, the role of elevated polyamine levels in promoting parasite persistence under nutrient starvation will be defined by comparing wild- type and polyamine-overproducing strains. Polyamine content, survival rates, and apoptotic markers will be analyzed to establish mechanistic links between polyamine levels and stress resistance. Aim 2 focuses on elucidating how polyamines support mitochondrial function by using ∆odc and ∆spdsyn mutants under both polyamine-supplemented and -depleted conditions. ATP and NADH production, electron transport chain activity, and oxidative stress will be assessed to clarify the role of polyamines in parasite bioenergetics. Aim 3 will evaluate the therapeutic potential of repurposing difluoromethylornithine (DFMO), an ornithine decarboxylase (ODC) inhibitor approved for African Sleeping Sickness and neuroblastoma, by investigating its use in combination therapies. Such combinations hold promise for improving treatment outcomes by enhancing efficacy, reducing drug resistance, and increasing safety in managing infectious diseases like leishmaniasis. EC50 values will be determined, drug synergy with FDA-approved anti-leishmanial drugs and mitochondrial-targeting agents will be evaluated, and mechanistic studies of parasite cell death will be initiated using assays that measure reactive oxygen species and apoptosis markers. This research will advance mechanistic understanding of parasite metabolism and persistence while establishing a rationale for DFMO- based combination therapies with strong translational promise. In alignment with the NIH NIAID mission, this project addresses a critical infectious disease threat and contributes to the development of safer, more effective treatments.
