Authors

A Carpinteyro Sanchez²; FJ Scott¹; CW Roberts²;  ¹ University of Strathclyde, UK;  ² Sipbs University Of Strathclyde, UK

Discussion

Acanthamoeba spp. are causative agents of a painful and severe sight-threatening corneal infection that can lead to blindness known as Acanthamoeba keratitis and a subacute disease in the brain which is usually fatal known as granulomatous amoebic encephalitis. Over the last few years, there has been a notorious increase in the number of infections due to Acanthamoeba spp. Poor diagnosis, problems of side effects and toxicity of the current drug treatment contribute to a high mortality rate. Strathclyde Minor Groove Binders (S-MGBs), compounds that bind to the minor groove of the DNA that designed and synthesised at University of Strathclyde were evaluated as potential alternative inhibitors against Acanthamoeba infections. Through cell viability microplate alamarBlue assays 42 S-MGBs were screened from which a library of 6 showed potent active inhibitory effect with half maximal inhibitory concentration (IC₅₀) below 1 µM. S-MGB 235 showed the most potent inhibitory effect with IC₅₀ in the nanomolar range against five Acanthamoeba isolates after 24 h and 96 h incubation. Confocal microscopy of trophozoites labelled with fluorescent S-MGB 363 (analogue of S-MGB 235) showed this compound in the nucleus, nucleolus and distributed over the granuloplasm causing cell lysis, supporting the potent effect observed in vitro by S-MGB 235. Furthermore, conditions were standardised to establish Galleria mellonella larvae as a new in vivo infection model for A. castellanii Neff infections to assess the efficacy and toxicity of voriconazole, miltefosine and S-MGB 235. Voriconazole and miltefosine did not protect larvae from trophozoite infection, however S-MGB 235 significantly protected larvae when compared with the negative control. Given the above, we suggest S-MGB-235 as a relevant novel compound that might complement aromatic diamidines in the current combination therapies for Acanthamoeba spp. diseases.