Characterisation of a South African human astrovirus as type 8 by antigenic and genetic analyses

Human astroviruses (HAstV) can, on the basis of immunoassays using type-specific rabbit antisera, be classified into eight serotypes that correlate with genotypes. Very few isolates of HAstV type 8 have been described and there is a paucity of data available with regard to the antigenic and genetic relationships between HAstV type 8 (HAstV-8) and HAstV types 1 (HAstV-1) to 7 (HAstV-7). A wild-type HAstV from a South African paediatric patient with diarrhoea was analysed antigenically, by immune electron microscopy and enzyme immunoassay, and genetically in selected regions of the ORF1a, ORF1b and ORF2 and characterised as a HAstV-8. This HAstV-8 strain exhibited greatest homology with HAstV-4 in the 5' end of the capsid gene and ORF1a and 1b, and greatest homology with HAstV-5 in the 3' end of the capsid region. This study confirms, by both antigenic and genetic analyses, that HAstV-8 represents a distinct antigenic and genotype and is the first report of a HAstV-8 from a hospitalised paediatric patient with diarrhoea in southern Africa.