CELL-CULTURE ADAPTATION OF PUUMALA HANTAVIRUS CHANGES THE INFECTIVITYFOR ITS NATURAL RESERVOIR, CLETHRIONOMYS-GLAREOLUS, AND LEADS TO ACCUMULATION OF MUTANTS WITH ALTERED GENOMIC RNA S-SEGMENT

This paper reports the establishment of a model for hantavirus host ad aptation. Wild-type (wt) (bank vole-passaged) and Vero E6 cell-culture d variants of Puumala virus strain Kazan were analyzed for their virol ogic and genetic properties. The wt variant was well adapted for repro duction in bank voles but not in cell culture, while the Vero E6 strai ns replicated to much higher efficiency in cell culture but did not re producibly infect bank voles. Comparison of the consensus sequences of the respective viral genomes revealed no differences in the coding re gion of the S gene. However, the noncoding regions of the S gene were found to be different at positions 26 and 1577. In one additional and independent adaptation experiment, all analyzed cDNA clones from the V ero E6-adapted variant were found to carry substitutions at position 1 580 of the S segment, just 3 nucleotides downstream of the mutation ob served in the first adaptation. No differences were found in the conse nsus sequences of the entire M segments from the wt and the Vero E6-ad apted variants. The results indicated different impacts of the S and t he M genomic segments for the adaptation process and selective advanta ges for the variants that carried altered noncoding sequences of the S segment. We conclude that the isolation in cell culture resulted in a phenotypically and genotypically altered hantavirus.