SEQUENCES OF WILD PUUMALA VIRUS GENES SHOW A CORRELATION OF GENETIC-VARIATION WITH GEOGRAPHIC ORIGIN OF THE STRAINS

An experimental scheme was developed for direct sequence analysis of P uumala virus-containing specimens from wild rodents (Clethrionomys gla reolus). Total RNA isolated from rodent lung tissues was reverse-trans cribed in the presence of a universal 11 nucleotide primer complementa ry to all three viral RNA segments followed by amplification in a PCR with gene-specific primers. A full-length PCR product of approximately 1800 bp from the S segment encoding the viral nucleoprotein and a pro duct of approximately 900 bp from the M segment (encoding the C-termin al two-thirds of the G2 protein and including the 3' non-coding region ) of Puumala virus (from C. glareolus trapped in Udmurtia) were prepar ed and sequenced. No pronounced differences to Vero cell-grown viruses were seen. The Udmurtia/894Cg/91 strain was more closely related to t he Bashkiria/CG18-20/84 strain than to the Finnish prototype strain of Puumala virus, Sotkamo/V-2969/81. Thus there is a correlation with th e geographic origin of the three strains. The results indicate the occ urrence of genetic drift and different selection pressures leading to (i) clustering of mutations, (ii) a lower frequency of nucleotide subs titutions in the coding than in the 3' noncoding regions and (iii) a h igher frequency of amino acid substitutions in G2 than in the N protei n.