Resequencing of the Puumala virus strain Sotkamo from the WHO Arbovirus collection.

RNA viruses exhibit a high mutation rate as the RNA-dependent RNA polymerase lacks proofreading and repair capabilities. It is known that serial passaging on cell culture leads to virus adaptation. Puumala virus (PUUV) strain Sotkamo is the prototype virus for the low-pathogenic hantavirus Puumala, family Bunyaviridae. A full-length sequence of the strain Sotkamos tripartite genome was made available more than 15 years ago, after at least 15 passages on Vero E6 cells. A distinct sample from the sequenced strain, with unknown passage history, was then included in the WHO Arbovirus collection. The genome sequence of this included sample was determined in this study and exhibited over 99 % identity in comparison to the previously published sequence. A total of 23 nucleotide changes across all genome segments were found. The small segment had the highest nucleotide variance without changes on the protein level. Within the extraviral domain of the glycoproteins, the majority of non-synonymous mutations were detected, whereas the large segment is most conserved on the nucleotide level. It seems possible that the PUUV strain Sotkamo adapted differently to serial passaging on cell culture in two different laboratories. In addition, a distinct passage number could exhibit itself within the nucleotide differences.