Human astroviruses are an important cause of gastroenteritis. As part of a molecular epidemiological study carried out in Mexico a human astrovirus isolate, Yuc-8, was adapted to grow in CaCo-2 cells, and its entire genome was sequenced. A 15 amino acid deletion in ORF1a, which has been associated with adaptation of astroviruses to grow in cells other than CaCo-2, was present 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 strains analysed, and a carboxy-terminal domain (residues 416 to 782) with identities between 36 and 60 %. Two non-superimposable phylogenetic trees were generated by separate analysis of these two domains, suggesting that a differential selective pressure is exerted along the structural polyprotein.Human astroviruses are recognized as an important cause of infantile gastroenteritis around the world . Astrovirus virions are formed by a non-enveloped protein capsid which surrounds a genome consisting of a positive-sense, single-stranded RNA molecule of 6n8 to 7n2 kb in length . The genomic RNA has three open reading frames (ORFs) designated 1a, 1b and 2. ORF1a and ORF1b code apparently for the nonstructural proteins of the virus ; ORF1a contains viral serine protease and nuclear localization signal motifs ; ORF1b contains motifs suggestive of an RNA-dependent RNA polymerase

In the present investigation we characterized the antigenic diversity of the VP4 and VP7 proteins in 309 and 261 human rotavirus strains isolated during two consecutive epidemic seasons, respectively, in three different regions of Mexico. G3 was found to be the prevalent VP7 serotype during the first year, being superseded by serotype G1 strains during the second season. To antigenically characterize the VP4 protein of the strains isolated, we used five neutralizing monoclonal antibodies (MAbs) which showed specificity for VP4 serotypes P1A, P1B, and P2 in earlier studies. Eight different patterns of reactivity with these MAbs were found, and the prevalence of three of these patterns varied from one season to the next. The P genotype of a subset of 52 samples was determined by PCR. Among the strains characterized as genotype P[4] and P[8] there were three and five different VP4 MAb reactivity patterns, respectively, indicating that the diversity of neutralization epitopes in VP4 is greater than that previously appreciated by the genomic typing methods.