RT Journal Article SR Electronic(1) A1 Xie, Hong A1 Ryman, Kate D A1 Campbell, Gerald A A1 Barrett, Alan D.TYR 1998 T1 Mutation in NS5 protein attenuates mouse neurovirulence of yellow fever 17D vaccine virus. JF Journal of General Virology, VO 79 IS 8 SP 1895 OP 1899 DO https://doi.org/10.1099/0022-1317-79-8-1895 PB Microbiology Society, SN 1465-2099, AB The 17D-204 vaccine manufactured in South Africa (17D-204-SA) and a large plaque variant (17D-LP) derived from it were highly virulent in adult mice. The LD50 of 17D-LP virus was 0 2 p.f.u. for mice following intracerebral inoculation. In comparison, a medium plaque variant derived from 17D-LP, termed 17D-MP virus, was found to be attenuated in adult mice following the same route of inoculation (> 104 p.f.u./LD50). Replication of 17D-MP virus was decreased in infected mouse brains compared to 17D-LP virus. Also, 17D-MP virus was slightly temperature sensitive at 39·5 °C. Compared to its parent viruses, 17D-204-SAand 17D-LP, 17D-MP virus had one unique mutation at nt 8045 in the genome which resulted in a single amino acid substitution (Pro → Ser) at residue 137 of the NS5 protein and appeared to be the mutation responsible for the attenuation of 17D-MP virus. This is the first time that altered virulence of a flavivirus caused by mutation in a non-structural protein gene, other than NS1, has been reported., UL https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-79-8-1895