Investigating the role of Acanthamoeba polyphaga in protecting Human Adenovirus from water disinfection treatment

Human adenoviruses are responsible for a wide range of clinical infections and are present in aquatic environments, including river, seawater, drinking-water and sewage. Free-living amoebae (Acanthamoeba) in the same environments may internalize them and other microorganisms can act as a reservoir for the internalized viruses. In this study, we studied the interaction between Acanthamoeba polyphaga and Human Adenovirus type 5 (HAdV 5) to determine whether the amoeba played a role in protecting the internalized viruses from chemical disinfection. The efficacy of sodium hypochlorite disinfection against A. polyphaga and HAdV 5 either singly or in combination was assessed at three different concentrations. Individually, the amoeba were more resistant to chemical disinfection than HAdV 5 and remained alive after exposure to 5 mg/l of sodium hypochlorite. In contrast, HAdV 5 lost infectivity following exposure to 2.5 mg/l of sodium hypochlorite. When the amoeba and HAdV 5 were co-cultured, infectious virus was found in the cytoplasm of the amoeba at 5 mg/l disinfectant concentration. These findings suggest that the A. polyphaga is providing protection for the HAdV 5.