Molecular analysis of a serotype 8 human astrovirus genome

Human astroviruses are an important cause of gastroenteritis. As part of a molecular epidemiological study carried out in Mexico a human astrovirus is olate, Yuc-8, was adapted to grow in CaCo-2 cells, and its entire genome wa s sequenced. A 15 amino acid deletion in ORF1a, which has been associated w ith adaptation of astroviruses to grow in cells other than CaCo-2, was pres ent in Yuc-8. Comparative sequence analysis of the Yuc-8 ORF2 with reported human astrovirus sequences revealed that this isolate belongs to genotype (serotype) 8. Two distinct domains in ORF2 were observed:an amino-terminal domain (residues 1 to 415), with identities higher than 81% among the strai ns analysed, and a carboxy-terminal domain (residues 416 to 782) with ident ities between 36 and 60%. Two non-superimposable phylogenetic trees were ge nerated by separate analysis of these two domains, suggesting that a differ ential selective pressure is exerted along the structural polyprotein.