Physicochemical point of view in the evaluation of PR772 bacteriophage as a surrogate for human adenovirus
Résumé
Among pathogenic enteric viruses, human adenoviruses (HAdV) are characterized by numerous structural specificities. Indeed, the diameter of their icosahedral capsid is about 90 nm with projecting fibre of 30 nm at each vertex and their genome is a linear double stranded DNA of 35-36 kbp, whereas other pathogenic enteric viruses are RNA viruses with an icosahedral capsid of about 25 nm without fibre. But HAdV are also noteworthy by their high frequency from surface water to drinking water which is explained by their faecal excretion whatever the induced symptoms and by their resistance to environmental conditions and to some disinfection treatments such as UV and monochloramines. These particularities raise the question of the behaviour of HAdV in water. Because of their structural, genomic and replicative similarities, tectiviruses such as bacteriophages PRD1 and PR772 have been proposed as potential surrogate for HAdV. Thus, bacteriophage PR772 appeared as a promising surrogate in the understanding of HAdV type 2 inactivation by free chlorine. The aim of the present work was to compare the physicochemical characteristics of HAdV type 2 and bacteriophage PR772 in order to evaluate this phage as a surrogate to help understand the behaviour of HAdV in water networks. The isoelectric charge of both particles was monitored in different pH and ionic strength conditions. The values of the isoelectric point (pI) of HAdV type 2 and bacteriophage PR772 were between 3 and 4, meaning that these particles are negatively charged at neutral pH. Adhesion experiments on hydrophobic polystyrene beads were performed to compare the hydrophobicity of both particles. Hydrophobicity appeared as the main difference between HAdV type 2 and bacteriophage PR772. The role of hydrophobicity in the accumulation of viruses on surfaces might limit the use of bacteriophage PR772 as surrogate of HAdV in such experiments.
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