DETECTION AND GENETIC DIFFERENTIATION OF HUMAN ASTROVIRUSES - PHYLOGENETIC GROUPING VARIES BY CODING REGION

Astroviruses are single-stranded, positive-sense RNA viruses that are associated with gastroenteritis in humans and animals. We describe a r everse transcription-polymerase chain reaction (RT-PCR) assay using pr imers targeted to a nonstructural protein coding region that allowed s ensitive detection and genetic typing of representative strains of sev en astrovirus serotypes. Phylogenetic analysis of the nucleotide seque nces of PCR products from the reference strains and several wild isola tes indicated two distinct genogroups of sequences in open reading fra me la (ORF la). These genogroups correlated with serotype: genogroup A included strains of types 1 to 5, while genogroup B included strains of types 6 and 7. This phylogenetic arrangement differs from the nearl y equidistant clustering of serotypes seen when comparing nucleotide s equences from either ORF Ib or ORF 2. It is possible that recombinatio n was responsible for the observed difference in genetic relationships .