Methionyl-tRNA synthetase inhibitor has potentin vivoactivity in a novelGiardia lamblialuciferase murine infection model

AbstractObjectivesMethionyl-tRNA synthetase (MetRS) inhibitors are under investigation for the treatment of intestinal infections caused byGiardia lamblia. To properly analyze the therapeutic potential of the MetRS inhibitor1717, experimental tools including a robust cell-based assay and a murine model of infection were developed based on novel strains ofG. lambliathat employ luciferase reporter systems to quantify viable parasites.MethodsSystematic screening of Giardia-specific promoters and luciferase variants led to the development of a strain expressing the click beetle green luciferase. Further modifying this strain to express NanoLuc created a dual reporter strain capable of quantifying parasites in both the trophozoite and cyst stages. These strains were used to develop a high throughput cell assay and a mouse infection model. A library of MetRS inhibitors was screened in the cell assay and1717was tested for efficacy in the mouse infection model.ResultsCell viability inin vitrocompound screens was quantified via bioluminescence readouts while infection loads in mice were monitored with noninvasive whole-animal imaging and fecal analysis. Compound1717was effective in clearing mice ofGiardiainfection in 3 days at varying doses, which is supported by data from enzymatic and phenotypic cell assays.ConclusionsThe newin vitroandin vivoassays based on luciferase expression by engineeredG. lambliastrains are useful for the discovery and development of new therapeutics for giardiasis. MetRS inhibitors, as validated by1717, have promising anti-giardiasis properties that merit further study as alternative therapeutics.