Isolation in Europe of 69 M-like (serotype 8) human rotavirus strains with either subgroup I or II specificity and a long RNA electropherotype.

During an epidemiological study on the prevalence of human rotavirus (HRV) serotypes 1-4 in Europe, we found that some strains could not be typed. However, when a monoclonal antibody directed to serotype 8 HRV was included in the typing assay, we detected seven 69 M-like (serotype 8) strains, six from Finland and one from Italy. The previously reported serotype 8 HRV strains, 69 M, B 37, and B 38 isolated in Indonesia, were of subgroup I specificity and presented a peculiar "super short" RNA electropherotype. In contrast, all the seven European strains possessed a long RNA pattern, and one of them had subgroup II specificity. Three of these strains were adapted to growth in cell cultures and were further characterized by neutralization and by Northern blot hybridization. They appeared to be closely related to serotype 8 HRV strain 69 M by neutralization, but showed partial homology with several human and animal strains by hybridization. The epidemiological importance of these serotype 8 strains circulating in Europe should be investigated, in view of their possible inclusion in a rotavirus vaccine.