Isolation of a Temperature-sensitive Strain of Enterovirus 71 with Reduced Neurovirulence for Monkeys

Small- and large-plaque-producing viruses were selected from the enterovirus 71 (E71) prototype, BrCr. The small-plaque virus was a temperature-resistant (tr) strain which could multiply at 39.5 degrees C as well as 35 degrees C. The large-plaque virus was temperature-sensitive (ts) and could not grow at 39.5 degrees C. It was shown that the ts strain was much less neurovirulent for monkeys than the tr strain. Both tr and ts strains reacted with homologous and heterologous antibodies in cross-neutralization tests. While no difference was found between tr and ts strains in the size of virion polypeptides, the VP1 polypeptide could be differentiated by isoelectric focusing. Genomic differences between the two strains were found by oligonucleotide mapping.