Characterization of the Uukuniemi virus group (Phlebovirus: Bunyaviridae): evidence for seven distinct species

Abstract

Evolutionary insights into the phleboviruses are limited because of an imprecise classification scheme based on partial nucleotide sequences and scattered antigenic relationships. In this report, the serologic and phylogenetic relationships of the Uukuniemi group viruses and their relationships with other recently characterized tick-borne phleboviruses are described using full-length genome sequences. We propose that the viruses currently included in the Uukuniemi virus group be assigned to five different species as follows: Uukuniemi virus, EgAn 1825-61 virus, Fin V707 virus, Chizé virus, and Zaliv Terpenia virus would be classified into the Uukuniemi species; Murre virus, RML-105-105355 virus, and Sunday Canyon virus would be classified into a Murre virus species; and Grand Arbaud virus, Precarious Point virus, and Manawa virus would each be given individual species status. Although limited sequence similarity was detected between current members of the Uukuniemi group and Severe fever with thrombocytopenia syndrome virus (SFTSV) and Heartland virus, a clear serological reaction was observed between some of them, indicating that SFTSV and Heartland virus should be considered part of the Uukuniemi virus group. Moreover, based on the genomic diversity of the phleboviruses and given the low correlation observed between complement fixation titers and genetic distance, we propose a system for classification of the Bunyaviridae based on genetic as well as serological data. Finally, the recent descriptions of SFTSV and Heartland virus also indicate that the public health importance of the Uukuniemi group viruses must be reevaluated.

Fig 1

Phylogenetic analysis of the available sequences of phlebovirus L ORF. Neighbor-joining (NJ) analysis at the amino acid level was performed due to the observed high variability of the underlying nucleotide sequences. The statistical significance of the tree topology was evaluated by bootstrap resampling of the sequences 1,000 times. Phylogenetic analyses were performed using MEGA software (29). *, Gouleako virus was isolated from mosquitoes (69).

Fig 2

Phylogenetic analysis of the available sequences of phlebovirus M ORF. A set of 133 M phlebovirus sequences comprising all partial or complete sequences from GenBank were analyzed under conditions identical to those of Fig. 1. *, Gouleako virus was isolated from mosquitoes (69).

Fig 3

Phylogenetic analysis of the available sequences of phlebovirus S ORF. (A) N ORF. A set of 154 N phlebovirus sequences comprising all partial or complete sequences from GenBank were analyzed under conditions identical to those of Fig. 1. (B) NS ORF. A set of 115 NS phlebovirus sequences comprising all partial or complete sequences from GenBank were analyzed under conditions identical to those of Fig. 1. *, Gouleako was isolated from mosquitoes.