*Article* **Insights into the Mechanisms of** *Lactobacillus acidophilus* **Activity against** *Entamoeba histolytica* **by Using Thiol Redox Proteomics**

**Lotem Sarid, Eva Zanditenas, Jun Ye , Meirav Trebicz-Geffen and Serge Ankri \***

Department of Molecular Microbiology, Ruth and Bruce Rappaport Faculty of Medicine, Technion, Haifa 31096, Israel; lotemsarid@campus.technion.ac.il (L.S.); zanditenas@campus.technion.ac.il (E.Z.); junye@campus.technion.ac.il (J.Y.); meiravg@technion.ac.il (M.T.-G.) **\*** Correspondence: sankri@technion.ac.il; Tel.: +972-4829-5453

**Abstract:** Amebiasis is an intestinal disease transmitted by the protist parasite, *Entamoeba histolytica*. *Lactobacillus acidophilus* is a common inhabitant of healthy human gut and a probiotic that has antimicrobial properties against a number of pathogenic bacteria, fungi, and parasites. The aim of this study was to investigate the amebicide activity of *L. acidophilus* and its mechanisms. For this purpose, *E. histolytica* and *L. acidophilus* were co-incubated and the parasite's viability was determined by eosin dye exclusion. The level of ozidized proteins (OXs) in the parasite was determined by resinassisted capture RAC (OX–RAC). Incubation with *L. acidophilus* for two hours reduced the viability of *E. histolytica* trophozoites by 50%. As a result of the interaction with catalase, an enzyme that degrades hydrogen peroxide (H2O2) to water and oxygen, this amebicide activity is lost, indicating that it is mediated by H2O2 produced by *L. acidophilus*. Redox proteomics shows that *L. acidophilus* triggers the oxidation of many essential amebic enzymes such as pyruvate: ferredoxin oxidoreductase, the lectin Gal/GalNAc, and cysteine proteases (CPs). Further, trophozoites of *E. histolytica* incubated with *L. acidophilus* show reduced binding to mammalian cells. These results support *L. acidophilus* as a prophylactic candidate against amebiasis.

**Keywords:** *Entamoeba histolytica*; *Lactobacillus acidophilus*; probiotic; redoxomics; cysteine proteases
