Genetic variation in the capsid region of human astrovirus serotype 4 isolated in Japan

The entire capsid regions of 12 serotype-4 astroviruses from Japan were sequenced and compared with those of other serotypes. Serotype-4 isolates were divided into two new subgroups. The intrasubgroup nucleic acid and deduced amino acid sequences were quite homologous (more than 93%), but slightly less so between subgroups (almost 85%). However, the serotype-4 sequences differed from those of serotypes 1, 2, 3, 5, 6, 7 and 8 (less than 50%). Determining whether these differences significantly alter the epidemiology and antigenicity will require further investigation.