Tahyna virus (TAHV) is a member of the California serogroup of the family Bunyaviridae and the genus Orthobunyavirus . Viruses of the genus Orthobunyavirus are arthropod-borne and possess a single-stranded, negative-sense

Tahyna virus (TAHV) is widely distributed in Europe and Asia. A previous study reported a high level of conservation of the TAHV genome in isolates from Europe. During 2006 and 2007, three Tahyna virus isolates from mosquitoes were obtained from various locations in Xinjiang, People’s Republic of China. We analyzed the complete coding sequence of full-length small, medium, and large segments of these isolates. Molecular and phylogenetic analyses of the three complete TAHV genomes showed that sequence identity between isolates from China and Europe was more divergent, and an unexpected level of medium segment diversity was found among isolates from China compared with high levels of sequence conservation for the small and large segments. This study indicated that effects of genotypic diversity on the ecology, transmission, and pathogenicity of TAHV in China should be studied. * Address correspondence to Guo-Dong Liang, State Key Laboratory for Infectious Disease Prevention and Control, Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, 155 Chang Bai Road, Chang Ping District, Beijing 102206, People’s Republic of China. E-mail: [email protected] 443 TAHYNA VIRUS IN CHINA and L segment ORFs of selected TAHV isolates by using a CLUSTAL W alignment of sequences and MEGA version 4 software ( Table 1 ). These analyses showed that the S segment nucleocapsid ORFs of TAHVs from China (XJ0625, XJ0708, and XJ0710) have greater than 99% nucleotide and amino acid sequence identities ( Table 1 ). Similarly, the TAHV L segment polymerase ORFs had ≥ 96.7% nucleotide and amino acid sequence identities ( Table 1 ). The S segment contains the N gene and the L segment contains the RNA-dependent RNA polymerase gene; both of these genes were relatively conserved within genus Orthobunyavirus . Although all virus isolates from Xinjiang or Europe were conserved within each group, the divergence between the two groups were still significant; isolates from Xinjiang showed no more than 92.5% or 83.1% nucleotide identities with Bardos 92 in S or L segments, respectively ( Table 1 ). In contrast to highly conservation of S and L segments in virus isolates from Xinjiang, analyses of glycoprotein ORFs of these viruses indicate a striking diversity of M segment genotypes within the Xinjiang group. Nucleotide identities of G N, NSm, and G C protein sequences in isolates from Xinjiang were 82.5–97% (G N ), 82.4–96.2% (NSm), and 80.1–96.1% (G C ). Identities for virus isolates from Xinjiang were much lower than those for virus isolates from Europe. 6, 7 Also, identities between virus isolates from Xinjiang and Europe were much lower than those within each group ( Supplementary Table 1 ). On the basis of host cell entry functions of envelope glycoproteins and diversity of hosts encountered in the arthropodborne virus transmission cycle, relative diversity of TAHV M segment genotypes when compared with S and L segment genotypes is not unexpected. However, the degree of M segment diversity (< 20% nucleotide sequence diversity) among viruses isolated from the same geographic location of Xinjiang is surprising. The striking pattern of dissimilarity of M segment sequences in contrast to a relatively high degree of similarity in S and L segment sequences provides evidence of possible reassortment of genomic segments between variant strains of TAHV in China. Although significant divergence was observed in the M segment, no amino acid changes were observed for CT and TMD motifs in virus isolates from Xinjiang. These two domains were highly conserved. The CT domain plays an important role in targeting heterodimerized G N and G C proteins to the Golgi apparatus, and the TMD domain is important for virus assembly and morphogenesis. 11, 12 A previous study indicated that high degree of identity in the 5¢ and 3¢ regions of the M segment, although deletions may have occurred within 3¢ non-coding region. 6 Nucleotide identities within virus isolates from Xinjiang were 95.1–100% in the 5¢ untranslated region (UTR) and 93.7–97.2% in the 3¢UTR. In addition, XJ0625 has two nucleotides deleted at positions 43 and 87 in the 3¢-non-coding region in the 3¢UTR (positions 4427 and 4471 for the whole M segment sequence). All virus isolates used in this study were passaged no more than three times after isolation from field mosquitoes. Therefore, it is likely that deletions to the genome did not occur during laboratory passage and that sequences reflect properties of viruses in nature. In addition, the variable region is not likely necessary for functions relevant to virus growth in such cell lines. Phylogenetic analyses of the newly isolated TAHVs from China indicated that neighbor-joining and maximum-parsimony trees shared highly similar topologies and bootstrap values for major groupings ( Figure 1 ). Phylogenies generated from TAHV N gene and polymerase gene ORFs infer that TAHV isolates from China are more closely related to one another than to the isolates from Europe, as indicated by the strong bootstrap support of these groupings ( Figure 1 ). In contrast with geographically consistent groupings generated for S and L segments, although the M segment sequences of XJ0625 and XJ0710 group together with extreme support, the M segment ORF of isolate XJ0708 from China aligns independently within the context of a relatively large diversity of isolates from Europe, including