Genomic profiling of three progenies isolated from a swarm of eGFP-tagged canine distemper viruses undergoing 40 serial passages.

Canine distemper virus (CDV) is classified into the genus Morbillivirus in the family Paramyxoviridae. This virus has a single-stranded genomic RNA with negative polarity. The L protein is the viral RNA-dependent RNA polymerase (RdRp), closely associated with the fidelity of genome replication. We previously constructed an enhanced green fluorescence protein (eGFP)-tagged recombinant CDV (rCDV-eGFP). This recombinant underwent a total of 47 passages in vitro including 7 blind and 40 ribavirin-treated passages, consequently showing a rich diversity of viral quasispecies by the analysis of next-generation sequencing (NGS). In the present study, through one round of plaque purification, three single-plaque-derived variants (SPDVs) with the brightest fluorescence were independently isolated from a swarm of rCDV-eGFP progenies at passage-47, and then subjected to NGS analysis. The NGS results comprehensively uncovered mutation profiles of these three SPDVs. More importantly, this study aimed to unravel the potential relation between viral replication fidelity and L protein sequence. However, two SPDVs showed no single-amino acid mutation in their own L proteins, implying the rCDV-eGFP progenitor that might be a high-fidelity strain. [ABSTRACT FROM AUTHOR]