The Activity of Polyhomoarginine against Acanthamoeba castellanii

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

Correction to: The Activity of Polyhomoarginine against Acanthamoeba castellanii (Biology, (2022), 11, 12, (1726), 10.3390/biology11121726)

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**. The correct legend appears below. **i. Figure 1: Change “(** p < 0.001 using a two-sample t-test and two-tailed distribution).” to “(** p < 0.001 using one way ANOVA).” ii. Figure 2: Change “(** p < 0.001, * p < 0.05 using a two-sample t-test and two-tailed distribution).” to “(** p < 0.001, * p < 0.05 using one way ANOVA).” iii. Figure 3: change “(** p < 0.001, * p < 0.05 using a two-sample t-test and two-tailed distribution).” to “(** p < 0.001, * p < 0.05 using one way ANOVA).” iv. Figure 4: change “(** p < 0.001, * p < 0.05 using a two-sample t-test and two-tailed distribution).” to “(** p < 0.001, * p < 0.05 using one way ANOVA).” ** There was an error in the original publication. **Full name of PHMB missing in Introduction**. A correction has been made to **Introduction**, **Paragraph Number—3**: i. Change “PHMB or chlorhexidine are widely used to treat this infection as monotherapies or in combination” to “Polyhexamethylene biguanide or chlorhexidine are widely used to treat this infection as monotherapies or in combination”. The authors state that the scientific conclusions are unaffected. This correction was approved by the Academic Editor. The original publication has also been updated

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

Subthreshold microsecond laser for proliferative diabetic retinopathy: a randomized pilot study

Mahima Jhingan,1 Abhilash Goud,1 Hari Kumar Peguda,1 Mitali Khodani,1 Jeffrey K Luttrull,2 Jay Chhablani1 1L V Prasad Eye Institute, Kallam Anji Reddy Campus, Hyderabad, India; 2Ventura County Retina Vitreous Medical Group, CA, USA Aim: To compare the outcomes of subthreshold microsecond (STM) and continuous-wave laser (CWL) panretinal photocoagulation (PRP).Methods: In this randomized, prospective, pilot study, 20 eyes of 10 subjects with symmetric severe non-proliferative (NPDR) or low-risk proliferative diabetic retinopathy (PDR) were included. Each eye of the subject was randomized into either CWL or STM PRP group. Patients were evaluated at baseline and at months 3, 6, and 9 with color fundus photographs and visual field tests at each visit; however, electroretinography (ERG) was conducted at baseline and at month 9. The primary outcome measure was the difference in disease progression between the groups. Secondary outcome measures included change in visual acuity, contrast visual acuity, retinal sensitivity on visual field test, and change in ERG parameters.Results: During the 9-month follow-up, one eye of the STM group progressed to vitreous hemorrhage at the month 6 follow-up and required rescue conventional laser. The CWL group showed a drop in low-contrast visual acuity, visual field index, and scotopic b/a ratio in comparison to the STM group, although the difference was statistically insignificant (p&gt;0.05).Conclusion: This prospective pilot study proposes microsecond PRP is non-inferior to CWL PRP and could be an alternative to CWL PRP to avoid associated complications in cases of severe NPDR and early PDR. Keywords: panretinal photocoagulation, diabetic retinopathy, proliferative diabetic retinopathy, micropulse laser, microsecond laser&nbsp