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Gabriel Gonzalez, Koki Aoki, Kanako O. Koyanagi, Nobuyoshi Kitaichi, Shigeaki Ohno, Hisatoshi Kaneko, Hiroaki Ishiko, Susumu Ishida, Hidemi Watanabe; Evolutionary Origin of Human Adenovirus 54. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3321.
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© ARVO (1962-2015); The Authors (2016-present)
Epidemic keratoconjunctivitis (EKC) is mainly caused by human adenovirus strains from species D (HAdV). It was recently reported that the cases where have been classified by serotyping and restriction enzyme patterns as caused by type 8 for the last 15 years should be re-diagnosed as caused by a new type named 54. The purpose of the present study was to examine the reasons behind type 54 spreading and its evolutionary origin as well as its relationship with type 8.
Whole sequenced genomes of two different type-54’s samples were compared against other sequences from HAdV-8, -9, -19, -22 and -37. We used Recombinant Detection Program (RDP) and SimPlot for identifying recombinant signals, also MAFFT and MEGA, for aligning and making phylogenetic inferences, respectively.
Type-8 was determined as the closest type to type-54 with a sequence difference of 4.3%. However, we also found putative recombinant signals on HAdV-54 in the regions coding penton base and hexon proteins from HAdV-22 and -9, respectively. A shared recombinant signal related to HAdV-19p was found in E3 region in both, HAdV-8 and -54. Removing the areas considered as sections of recombinant events on adenoviruses and highly variable among types (i.e. Penton, Hexon, E3 and Fiber), which accounts 28% of the genome, we got the sequence difference between -8 and -54 at 2.8%. This reduced difference offers an explanation to similar restriction enzyme patterns and confusing results on Neutralization Tests.
HAdV-54’s closest type after diverging from a common ancestor is type-8, but divergence was increased on the former by recombinant events, even though similarities in some genomic regions are conserved. This is the main cause of confusing diagnosis between both types, due to similarities on fiber and same restrictions patterns in these conserved genomic sections. However, recombinant events clearly distinguish both types on penton base and hexon.
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