GENETIC-VARIATION OF WILD PUUMALA VIRUSES WITHIN THE SEROTYPE, LOCAL RODENT POPULATIONS AND INDIVIDUAL ANIMAL

Reverse transcriptase polymerase chain reaction cloning and sequencing were used to determine the range of S gene/N protein variability in w ild Puumala virus (PUU) strains and to study phylogenetic relationship s between two groups of strains which originated from Finland and from European Russia. Analyses of the nucleotide and predicted amino acid sequences showed: (1) all PUU strains shared a common ancient ancestor ; and (2) the more recent ancestors were different for the Finnish bra nch and the Russian branch of PUU strains. A cluster of amino acid sub stitutions in the N protein of Finnish strains was found; this cluster was located within a highly variable region of the molecule carrying B-cell epitopes (Vapalahti et al., J. Med. Virol., 1995, in press). Di fferent levels of S gene/N protein diversity of PUU were revealed supp orting the view of geographical clustering of genetic variants. Puumal a virus from individual voles was found to be a complex mixture of clo sely related variants-quasispecies. The ratio of non-silent to silent nucleotide mutations registered in the S genes/N proteins of PUU quasi species was 4- to 16-fold higher than that in Puumala virus strains, r esulting in a more wide range of quasispecies N protein sequence diver sity.