Effects of Inosine-5′-monophosphate Dehydrogenase (IMPDH/GuaB) Inhibitors on <i>Borrelia burgdorferi</i> Growth in Standard and Modified Culture Conditions
<i>Borrelia burgdorferi</i>’s inosine-5′-monophosphate dehydrogenase (IMPDH, GuaB encoded by the <i>guaB</i> gene) is a potential therapeutic target. GuaB is necessary for <i>B. burgdorferi</i> replication in mammalian hosts but not in standard laboratory culture...
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2024-10-01
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| author | Eric L. Siegel Connor Rich Sanchana Saravanan Patrick Pearson Guang Xu Stephen M. Rich |
| author_facet | Eric L. Siegel Connor Rich Sanchana Saravanan Patrick Pearson Guang Xu Stephen M. Rich |
| author_sort | Eric L. Siegel |
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| description | <i>Borrelia burgdorferi</i>’s inosine-5′-monophosphate dehydrogenase (IMPDH, GuaB encoded by the <i>guaB</i> gene) is a potential therapeutic target. GuaB is necessary for <i>B. burgdorferi</i> replication in mammalian hosts but not in standard laboratory culture conditions. Therefore, we cannot test novel GuaB inhibitors against <i>B. burgdorferi</i> without utilizing mammalian infection models. This study aimed to evaluate modifications to a standard growth medium that may mimic mammalian conditions and induce the requirement of GuaB usage for replication. The effects of two GuaB inhibitors (mycophenolic acid, 6-chloropurine riboside at 125 μM and 250 μM) were assessed against <i>B. burgdorferi</i> (<i>guaB</i>+) grown in standard Barbour–Stoenner–Kelly-II (BSK-II) medium (6% rabbit serum) and BSK-II modified to 60% concentration rabbit serum (BSK-II/60% serum). BSK-II directly supplemented with adenine, hypoxanthine, and nicotinamide (75 μM each, BSK-II/AHN) was also considered as a comparison group. In standard BSK-II, neither mycophenolic acid nor 6-chloropurine riboside affected <i>B. burgdorferi</i> growth. Based on an ANOVA, a dose-dependent increase in drug effects was observed in the modified growth conditions (F = 4.471, <i>p</i> = 0.001). Considering higher drug concentrations at exponential growth, mycophenolic acid at 250 μM reduced spirochete replication by 48% in BSK-II/60% serum and by 50% in BSK-II/AHN (<i>p</i> < 0.001 each). 6-chloropurine riboside was more effective in both mediums than mycophenolic acid, reducing replication by 64% in BSK-II/60% serum and 65% in BSK-II/AHN (<i>p</i> < 0.001 each). These results demonstrate that modifying BSK-II medium with physiologically relevant levels of mammalian serum supports replication and induces the effects of GuaB inhibitors. This represents the first use of GuaB inhibitors against <i>Borrelia burgdorferi</i>, building on tests against purified <i>B. burgdorferi</i> GuaB. The strong effects of 6-chloropurine riboside indicate that <i>B. burgdorferi</i> can salvage and phosphorylate these purine derivative analogs. Therefore, this type of molecule may be considered for future drug development. Optimization of this culture system will allow for better assessment of novel Borrelia-specific GuaB inhibitor molecules for Lyme disease interventions. The use of GuaB inhibitors as broadcast sprays or feed baits should also be evaluated to reduce spirochete load in competent reservoir hosts. |
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| spelling | doaj-art-7bb017b274d144ec9df0f8afa065b1fb2025-08-20T02:11:00ZengMDPI AGMicroorganisms2076-26072024-10-011210206410.3390/microorganisms12102064Effects of Inosine-5′-monophosphate Dehydrogenase (IMPDH/GuaB) Inhibitors on <i>Borrelia burgdorferi</i> Growth in Standard and Modified Culture ConditionsEric L. Siegel0Connor Rich1Sanchana Saravanan2Patrick Pearson3Guang Xu4Stephen M. Rich5Laboratory of Medical Zoology, Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USALaboratory of Medical Zoology, Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USALaboratory of Medical Zoology, Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USALaboratory of Medical Zoology, Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USALaboratory of Medical Zoology, Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USALaboratory of Medical Zoology, Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA<i>Borrelia burgdorferi</i>’s inosine-5′-monophosphate dehydrogenase (IMPDH, GuaB encoded by the <i>guaB</i> gene) is a potential therapeutic target. GuaB is necessary for <i>B. burgdorferi</i> replication in mammalian hosts but not in standard laboratory culture conditions. Therefore, we cannot test novel GuaB inhibitors against <i>B. burgdorferi</i> without utilizing mammalian infection models. This study aimed to evaluate modifications to a standard growth medium that may mimic mammalian conditions and induce the requirement of GuaB usage for replication. The effects of two GuaB inhibitors (mycophenolic acid, 6-chloropurine riboside at 125 μM and 250 μM) were assessed against <i>B. burgdorferi</i> (<i>guaB</i>+) grown in standard Barbour–Stoenner–Kelly-II (BSK-II) medium (6% rabbit serum) and BSK-II modified to 60% concentration rabbit serum (BSK-II/60% serum). BSK-II directly supplemented with adenine, hypoxanthine, and nicotinamide (75 μM each, BSK-II/AHN) was also considered as a comparison group. In standard BSK-II, neither mycophenolic acid nor 6-chloropurine riboside affected <i>B. burgdorferi</i> growth. Based on an ANOVA, a dose-dependent increase in drug effects was observed in the modified growth conditions (F = 4.471, <i>p</i> = 0.001). Considering higher drug concentrations at exponential growth, mycophenolic acid at 250 μM reduced spirochete replication by 48% in BSK-II/60% serum and by 50% in BSK-II/AHN (<i>p</i> < 0.001 each). 6-chloropurine riboside was more effective in both mediums than mycophenolic acid, reducing replication by 64% in BSK-II/60% serum and 65% in BSK-II/AHN (<i>p</i> < 0.001 each). These results demonstrate that modifying BSK-II medium with physiologically relevant levels of mammalian serum supports replication and induces the effects of GuaB inhibitors. This represents the first use of GuaB inhibitors against <i>Borrelia burgdorferi</i>, building on tests against purified <i>B. burgdorferi</i> GuaB. The strong effects of 6-chloropurine riboside indicate that <i>B. burgdorferi</i> can salvage and phosphorylate these purine derivative analogs. Therefore, this type of molecule may be considered for future drug development. Optimization of this culture system will allow for better assessment of novel Borrelia-specific GuaB inhibitor molecules for Lyme disease interventions. The use of GuaB inhibitors as broadcast sprays or feed baits should also be evaluated to reduce spirochete load in competent reservoir hosts.https://www.mdpi.com/2076-2607/12/10/2064<i>Borrelia burgdorferi</i>inosine-5′-monophosphate dehydrogenaseGuaBLyme disease |
| spellingShingle | Eric L. Siegel Connor Rich Sanchana Saravanan Patrick Pearson Guang Xu Stephen M. Rich Effects of Inosine-5′-monophosphate Dehydrogenase (IMPDH/GuaB) Inhibitors on <i>Borrelia burgdorferi</i> Growth in Standard and Modified Culture Conditions Microorganisms <i>Borrelia burgdorferi</i> inosine-5′-monophosphate dehydrogenase GuaB Lyme disease |
| title | Effects of Inosine-5′-monophosphate Dehydrogenase (IMPDH/GuaB) Inhibitors on <i>Borrelia burgdorferi</i> Growth in Standard and Modified Culture Conditions |
| title_full | Effects of Inosine-5′-monophosphate Dehydrogenase (IMPDH/GuaB) Inhibitors on <i>Borrelia burgdorferi</i> Growth in Standard and Modified Culture Conditions |
| title_fullStr | Effects of Inosine-5′-monophosphate Dehydrogenase (IMPDH/GuaB) Inhibitors on <i>Borrelia burgdorferi</i> Growth in Standard and Modified Culture Conditions |
| title_full_unstemmed | Effects of Inosine-5′-monophosphate Dehydrogenase (IMPDH/GuaB) Inhibitors on <i>Borrelia burgdorferi</i> Growth in Standard and Modified Culture Conditions |
| title_short | Effects of Inosine-5′-monophosphate Dehydrogenase (IMPDH/GuaB) Inhibitors on <i>Borrelia burgdorferi</i> Growth in Standard and Modified Culture Conditions |
| title_sort | effects of inosine 5 monophosphate dehydrogenase impdh guab inhibitors on i borrelia burgdorferi i growth in standard and modified culture conditions |
| topic | <i>Borrelia burgdorferi</i> inosine-5′-monophosphate dehydrogenase GuaB Lyme disease |
| url | https://www.mdpi.com/2076-2607/12/10/2064 |
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