The Activity of Polyhomoarginine against Acanthamoeba castellanii

Abstract

Arginine-rich peptides can have broad-spectrum anti-bacterial and anti-fungal activities. Polyhomoarginine consists of highly cationic residues which can act on the negatively charged microbial cell membranes. Acanthamoeba is a free-living protozoan known to cause a rare corneal infection which is difficult to diagnose and treat. This study evaluated the activity of the polyhomoarginines against Acanthamoeba castellanii. Acanthamoeba amoebicidal, amoebistatic, encystation and excystment assays were performed using protocols described in the literature. The activity of polyhomoarginines (PHAs) of different lengths (10 to 400 residues) was measured against the trophozoites and cysts of Acanthamoeba castellanii ATCC30868 in concentrations ranging from 0.93 µM to 15 µM. Data were represented as mean ± SE and analysed using one-way ANOVA. Overall, PHAs demonstrated good anti-acanthamoeba activity against both trophozoites and cysts. PHA 30 reduced the number of viable trophozoites by 99%, inhibited the formation of cysts by 96% and the emergence of trophozoites from cysts by 67% at 3.75 μM. PHA 10 was similarly active, but at a slightly higher concentration of 15 µM, reducing the numbers of viable trophozoites by 98%, inhibiting cyst formation by 84% and preventing the emergence of trophozoites from cysts by 99%. At their greatest anti-amoeba concentrations, PHA 10 gave only 8% haemolysis at 15 μM while PHA 30 gave <40 % haemolysis at 3.75 μM. Polyhomoarginine 10 showed excellent anti-amoebic activity against both forms of Acanthamoeba castellanii and was non-toxic at its most active concentrations. This implies that polyhomoarginines can be developed into a potential therapeutic agent for Acanthamoeba keratitis. However, there is a need to carry out further pre-clinical and then in vivo experiments in the AK animal model.

The amoebicidal effect of Torreya nucifera extract on Acanthamoeba lugdunensis

“…A total volume of 90 μL of A. lugdunensis were seeded in duplicate on a 96-well black wall microtiter plate from a stock solution of 1 X 10 4 cells/mL. Twentyfive μg/ mL and 50 μg/mL T. nucifera solutions were prepared and added into each different well (a negative control with PYG and positive control with 2.5% of Triton X-100 [Sigma Aldrich; St. Louis, Missouri, USA]), as previously described [16][17][18]. After incubation for 24 h at 26˚C, SYTOX Green reagent was added at a final concentration of 1 μM for 15 min under dark conditions.…”

Correction: Peguda et al. The Activity of Polyhomoarginine against Acanthamoeba castellanii. Biology 2022, 11, 1726

“…In the original publication [ 1 ] , there was a mistake in the legend for ** Figure 1—4 ** . **Using a two-sample t -test and two-tailed distribution** .…”