Major mutation events in structural genes of peste des petits ruminants virus through serial passages in vitro.

Peste des petits ruminants (PPR) is an highly contagious disease of small ruminants, and caused by peste des petits ruminants virus (PPRV), a member of the genus Morbillivirus in the family Paramyxoviridae. The first outbreak of PPR in China was officially reported in July 2007, when a PPRV strain was successfully isolated from a sick goat in Tibet, followed by sequencing at a full-genome level (China/Tibet/Geg/07-30, GenBank: FJ905304.1). To date, this isolate has been virulently attenuated by more than 90 serial passages in Vero-Dog-SLAM cells at our laboratory. In this study, a total of nine strains by serial passages (namely the 10th, 20th, 30th, 40th, 50th, 60th, 70th, 80th, and 90th passages) were chosen for sequencing of six structural genes in PPRV. The sequence analysis showed that mutation rates in all viral genes were relatively low, and only a few identical mutations within certain genes were stably maintained after an earlier passage, perhaps indicating a predominance of mutants after such a passage.