Genetic analysis of the capsid region of astroviruses

Eight serotypes of human astroviruses (HAstV-1 to HAstV-8) have been descri bed. To date, the entire genomes of HAstV-1 and HAstV-2 as well as the ORF2 sequences of HAstV-1-6 and 8 have been reported. In this study, the ORF2 s equences of seventeen strains of HAstVs originating from different countrie s were determined, as well as the sequence ORF2 of one porcine astrovirus ( PAstV) strain. Afterwards, comparison of the capsid protein precursors enco ded by ORF2 of 46 strains of HAstVs, PAstV, and feline astrovirus (FAstV) w as carried out. A phylogenetic tree showed eight genogroups of HAstVs that corresponded exactly to the serotypes, HAstV-3 and 7 were the most closely related, whereas HAstVs, FAstV, and PAstV segregated from each other. Compa red to a PAstV, a FAstV is closer to HAstVs. Furthermore, the capsid protei n precursors were divided into four regions (after amino acid residues 424, 688, and 776, respectively) based on sequence identity. Region I was the m ost conserved, and FAstV was very close in identity to HAstVs. Two amino ac id motifs in region 1 were predicted to contain the common antigenic epitop es. Region II was relatively variable. Deletions and insertions were charac teristic of region iii, and region IV was relatively conserved. To our know ledge, this is the first comparative sequence analysis of the capsid protei n precursors of eight serotypes of HAstVs as well as two animal astroviruse s (FAstV and PAstV). J. Med. Virol. 64:245-255, 2001. (C) 2001 Wiley-Liss, Inc.