Novel Antiamoebic Tyrocidine-Derived Peptide against Brain-Eating Amoebae

Next generation imidazothiazole and imidazooxazole derivatives as potential drugs against brain-eating amoebae

Managing primary amoebic meningoencephalitis, induced by Naegleria fowleri poses a complex medical challenge. There is currently no specific anti-amoebic drug that has proven effectiveness against N. fowleri infection. Ongoing research endeavours are dedicated to uncovering innovative treatment strategies, including the utilization of drugs and immune modulators targeting Naegleria infection. In this study, we explored the potential of imidazo[2,1-b]thiazole and imidazooxazole derivatives that incorporate sulfonate and sulfamate groups as agents with anti-amoebic properties against N. fowleri. We assessed several synthesized compounds (1f, 1m, 1q, 1s, and 1t) for their efficacy in eliminating amoebae, their impact on cytotoxicity, and their influence on the damage caused to human cerebral microvascular endothelial (HBEC-5i) cells when exposed to the N. fowleri (ATCC 30174) strain. The outcomes revealed that, among the five compounds under examination, 1m, 1q, and 1t demonstrated notable anti-parasitic effects against N. fowleri (P ≤ 0.05). Compound 1t exhibited the highest anti-parasitic activity, reducing N. fowleri population by 80%. Additionally, three compounds, 1m, 1q, and 1t, significantly mitigated the damage inflicted on host cells by N. fowleri. However, the results of cytotoxicity analysis indicated that while 1m and 1q had minimal cytotoxic effects on endothelial cells, compound 1t caused moderate cytotoxicity (34%). Consequently, we conclude that imidazo[2,1-b]thiazole and imidazooxazole derivatives containing sulfonate and sulfamate groups exhibit a marked capacity to eliminate amoebae viability while causing limited toxicity to human cells. In aggregate, these findings hold promise that could potentially evolve into novel therapeutic options for treating N. fowleri infection.

The anti-amoebic potential of carboxamide derivatives containing sulfonyl or sulfamoyl moieties against brain-eating Naegleria fowleri

Naegleria fowleri is a free-living thermophilic flagellate amoeba that causes a rare but life-threatening infection called primary amoebic meningoencephalitis (PAM), with a very high fatality rate. Herein, the anti-amoebic potential of carboxamide derivatives possessing sulfonyl or sulfamoyl moiety was assessed against pathogenic N. fowleri using amoebicidal, cytotoxicity and cytopathogenicity assays. The results from amoebicidal experiments showed that derivatives dramatically reduced N. fowleri viability. Selected derivatives demonstrated IC50 values at lower concentrations; 1j showed IC50 at 24.65 μM, while 1k inhibited 50% amoebae growth at 23.31 μM. Compounds with significant amoebicidal effects demonstrated limited cytotoxicity against human cerebral microvascular endothelial cells. Finally, some derivatives mitigated N. fowleri-instigated host cell death. Ultimately, this study demonstrated that 1j and 1k exhibited potent anti-amoebic activity and ought to be looked at in future studies for the development of therapeutic anti-amoebic pharmaceuticals. Further investigation is required to determine the clinical relevance of our findings.

The Anti-Amoebic Activity of a Peptidomimetic against Acanthamoeba castellanii

Acanthamoeba is a free-living protozoan known to cause keratitis most commonly, especially among contact lens wearers. Treatment of Acanthamoeba keratitis is challenging as Acanthamoeba can encyst from the active form, a trophozoite, into a hibernating cyst that is refractory to antibiotics and difficult to kill; therefore, there is a need for more effective anti-amoebic strategies. In this study, we have evaluated the anti-amoebic activity of the antimicrobial peptide mimic RK-758 against Acanthamoeba castellanii. RK-758 peptidomimetic was subjected to biological assays to investigate its amoebicidal, amoebistatic, anti-encystation, and anti-excystation effects on A. castellanii. The anti-amoebic activity of the peptide mimic RK-758 was compared with chlorhexidine against the Acanthamoeba castellanii ATCC30868 and Acanthamoeba castellanii 044 (a clinical strain) with the concentrations of both ranging from 125 µM down to 7.81 µM. All experiments were performed in duplicate with three independent replicates. The data were represented as mean ± SE and analysed using a two-sample t-test and two-tailed distributions. A p < 0.05 was considered statistically significant. The peptidomimetic RK-758 had anti-Acanthamoeba activity against both trophozoites and cysts in a dose-dependent manner. The RK-758 had amoebicidal and growth inhibitory activities of ≥50% at a concentration between 125 µM and 15.6 µM against the trophozoites of both Acanthamoeba strains. Inhibitory effects on the cyst formation and trophozoite re-emergence from cysts were noted at similar concentrations. Chlorhexidine had 50% activity at 7.81 µM and above against the trophozoites and cysts of both strains. In the haemolysis assay, the RK-758 lysed horse RBCs at concentrations greater than 50 µM whereas lysis occurred at concentrations greater than 125 µM for the chlorhexidine. The peptidomimetic RK-758, therefore, has activity against both the trophozoite and cyst forms of Acanthamoeba and has the potential to be further developed as an anti-microbial agent against Acanthamoeba. RK-758 may also have use as an anti-amoebic disinfectant in contact lens solutions.