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The present study aimed to investigate an effective, sustainable and accessible way to inactivate chlorine-resistant microorganisms, such as Acanthamoeba castellanii, through the photolysis of sodium chloride (NaCl) and sodium hypochlorite (NaOCl) in the water matrix. The trophozoites and cysts (2 × 107 per 8 mL) were exposed for 30, 60, 90, 120 and 150 min to the photolysis effect of NaOCl (1.0, 2.0, 4.0 and 8.0 mg/L) or NaCl (5.0, 10, 20 and 40 g/L) by ultraviolet light C (243 μW·cm2), then the viability was analyzed. The inactivation of all trophozoites was achieved by exposure to the photolysis effect of 2.0 mg/L of NaOCl or 20 g/L of NaCl, in 150 or 120 min, respectively. Inactivation of all cysts was achieved by double exposure to the photolysis effect of 1.0 mg/L NaOCl or 5.0 g/L NaCl from 90 min of each exposure round. The exposure time was a strong determinant in the inactivation of A. castellanii trophozoites or cysts. The photolysis of NaOCl or NaCl is an effective method to eliminate A. castellanii in water. These findings expand the list of chlorine-resistant microorganisms that can be inactivated by NaOCl photolysis and show that NaCl photolysis is a new and promising method for treating swimming pool water and wastewater.

ABSTRACT Acanthamoeba is the most common free-living environmental amoeba, it may serve as an important vehicle for various microorganisms living in the same environment, such as viruses, being pathogenic to humans. This study aimed to detect and quantify human adenoviruses (HAdV) in Acanthamoebas isolated from water samples collected from swimming pools in the city of Porto Alegre, Southern Brazil. Free-living amoebae of the genus Acanthamoeba were isolated from water samples, and isolates (n=16) were used to investigate the occurrence of HAdVs. HAdV detection was performed by quantitative real-time polymerase chain reaction (qPCR). HAdVs were detected in 62.5% (10/16) of Acanthamoeba isolates, ranging from 3.24x103 to 5.14x105 DNA copies per milliliter of isolate. HAdV viral loads found in this study are not negligible, especially because HAdV infections are associated with several human diseases, including gastroenteritis, respiratory distress, and ocular diseases. These findings reinforce the concept that Acanthamoeba may act as a reservoir and promote HAdV transmission through water.

Cryptococcus gattii is a basidiomycetous yeast that can be found in the environment and is one of the agents of cryptococcosis, a life-threatening disease. During its life cycle, cryptococcal cells take hold inside environmental predators such as amoebae. Despite their evolutionary distance, macrophages and amoebae share conserved similar steps of phagocytosis and microbial killing. To evaluate whether amoebae also share other antifungal strategies developed by macrophages, we investigated nutritional immunity against cryptococcal cells. We focused on zinc homeostasis modulation in Acanthamoeba castellanii infected with C. gattii. The intracellular proliferation rate (IPR) in amoebae was determined using C. gattii R265 and mutants for the ZIP1 gene, which displays defects of growth in zinc-limiting conditions. We detected a reduced IPR in cells lacking the ZIP1 gene compared to wild-type strains, suggesting that amoebae produce a low zinc environment to engulfed cells. Furthermore, flow cytometry analysis employing the zinc probe Zinpyr-1 confirmed the reduced concentration of zinc in cryptococcal-infected amoebae. qRT-PCR analysis of zinc transporter-coding genes suggests that zinc export by members of the ZnT family would be involved in the reduced intracellular zinc concentration. These results indicate that amoebae may use nutritional immunity to reduce fungal cell proliferation by reducing zinc availability for the pathogen.

Gene therapy is a promising tool for the treatment of ocular diseases. Nevertheless, there are some import limitations, especially related to the ocular route and the characteristics of nucleic acids that must be overcome to ensure the success of the therapy. In this context, nanotechnology-based carriers such as nanoemulsions, nanoparticles, dendrimers and liposomes have risen as a promising vehicle for the protection of genetic material for vectoring the target cells. The success of such approach is closely related to the judicious selection of the biomaterial, where chemical structure and intermolecular interactions play a major role. So, this manuscript reviews some of the most important biomaterials, lipid and polymeric origin, employed in the manufacture of nanotechnologic carriers for ocular gene therapy involving interfering RNA (siRNA), antisense oligonucleotide (AS-ON) and plasmid DNA (pDNA).