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Immunometabolic Circuits in Infection for Advancing Host Directed Therapies
Published on: September 13, 2024
Evaluation of synergy between host and pathogen-directed therapies against intracellular Leishmania donovani
M Shamim Hasan Zahid1, Monica M Johnson1, Robert J Tokarski2
1Division of Pharmacoengineering and Molecular Pharmaceutics, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.
Abstract:
Visceral leishmaniasis (VL) is associated with treatment complications due to the continued growth of resistant parasites toward currently available pathogen-directed therapeutics. To limit the emergence and combat resistant parasites there is a need to develop new anti-leishmanial drugs and alternative treatment approaches, such as host-directed therapeutics (HDTs). Discovery of new anti-leishmanial drugs including HDTs requires suitable in vitro assay systems. Herein, we modified and evaluated a series of resazurin assays against different life-stages of the VL causing parasite, Leishmania donovani to identify novel HDTs. We further analyzed the synergy of combinatorial interactions between traditionally used pathogen-directed drugs and HDTs for clearance of intracellular L. donovani. The inhibitory concentration at 50% (IC50) of the five evaluated therapies [amphotericin B (AMB), miltefosine, paromomycin, DNER-4, and AR-12 (OSU-03012)] was determined against promastigotes, extracellular amastigotes, and intracellular amastigotes of L. donovani via a resazurin-based assay and compared to image-based microscopy. Using the resazurin-based assay, all evaluated therapies showed reproducible anti-leishmanial activity against the parasite's different life-stages. These results were consistent to the traditional image-based technique. The gold standard of therapy, AMB, showed the highest potency against intracellular L. donovani, and was further evaluated for combinatorial effects with the HDTs. Among the combinations analyzed, pathogen-directed AMB and host-directed AR-12 showed a synergistic reduction of intracellular L. donovani compared to individual treatments. The modified resazurin assay used in this study demonstrated a useful technique to measure new anti-leishmanial drugs against both intracellular and extracellular parasites. The synergistic interactions between pathogen-directed AMB and host-directed AR-12 showed a great promise to combat VL, with the potential to reduce the emergence of drug-resistant strains.
Insights
New host-directed therapies (HDTs) combat drug-resistant visceral leishmaniasis (VL). A resazurin assay identified synergistic effects between amphotericin B and AR-12, offering a promising strategy against Leishmania donovani.
Area of Science:
- Parasitology
- Drug Discovery
- Infectious Diseases
Background:
- Visceral leishmaniasis (VL) presents treatment challenges due to drug-resistant Leishmania donovani parasites.
- Novel therapeutic strategies, including host-directed therapeutics (HDTs), are crucial for combating resistant strains.
- Development of effective in vitro assay systems is essential for identifying new anti-leishmanial drugs and HDTs.
Purpose of the Study:
- To modify and evaluate resazurin assays for assessing anti-leishmanial activity against various life stages of Leishmania donovani.
- To identify novel host-directed therapeutics (HDTs) with potential against VL.
- To investigate the synergistic interactions between existing drugs and HDTs for enhanced clearance of intracellular L. donovani.
Main Methods:
- Resazurin-based assays were developed and validated against promastigotes, extracellular amastigotes, and intracellular amastigotes of L. donovani.
- Five therapies, including amphotericin B (AMB), miltefosine, paromomycin, DNER-4, and AR-12, were evaluated for their inhibitory concentrations (IC50).
- Combinatorial effects of AMB with HDTs were analyzed for synergistic activity against intracellular L. donovani, with results compared to image-based microscopy.
Main Results:
- The resazurin assay demonstrated reproducible anti-leishmanial activity across different parasite life stages, consistent with image-based methods.
- Amphotericin B (AMB) exhibited the highest potency against intracellular L. donovani.
- A synergistic effect was observed when combining the pathogen-directed drug AMB with the host-directed therapeutic AR-12, leading to a greater reduction of intracellular L. donovani than individual treatments.
Conclusions:
- The modified resazurin assay is a valuable tool for evaluating new anti-leishmanial drugs against both intracellular and extracellular parasites.
- The combination of pathogen-directed AMB and host-directed AR-12 shows significant promise for treating VL and mitigating the development of drug resistance.
- This synergistic approach offers a potential new strategy to combat visceral leishmaniasis effectively.
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