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Viruses assigned to the genus Ledantevirus form a distinct monophyletic group based on well-supported Maximum Likelihood trees inferred from complete L sequences. Many of the viruses in the genus have been isolated from bats and many or all appear to be transmitted by arthropods. There are three distinct phylogroups comprising: A) Fukuoka virus (FUKV), Barur virus (BARV), Nishimuro virus (NISV), Nkolbisson virus (NKOV) and Yongjia tick virus 2 (YjTV-2); B) Le Dantec virus (LDV), Keuraliba virus (KEUV) and Kern Canyon virus (KCV); and C) Mount Elgon bat virus (MEBV), Kumasi rhabdovirus (KRV), Oita virus (OITAV), Fikirini rhabdovirus (FKRV), Kolente virus (KOLEV), Wuhan louse fly virus 5 (WhLFV-5) and Kanyawara virus (KYAV). The genus is linked phylogenetically to viruses assigned to the genera Perhavirus and Sprivivirus (infecting fish), and more distantly to the genus Vesiculovirus (infecting mammals).
For all members of the genus that have been characterised morphologically, virions are bullet-shaped. A detailed electron microscopic study of KCV revealed enveloped virions (mean dimensions 132 x 73 nm) in negative-stained preparations with prominent cross-striations, axial channels, and 8 nm surface projections evenly distributed at 7 nm intervals (Murphy and Fields 1967). MEBV displayed similar morphology under negative-stain but virions were longer (mean 230 nm x 70 nm) (Murphy et al., 1970). In ultrathin sections of mouse brain tissue, enveloped bullet-shaped OITAV virions (160–300 nm x 100 nm) have been reported (Iwasaki et al., 2004); enveloped bullet-shaped virions have also been reported from cell supernates or in ultrathin sections of infected tissue for NKOV (130–150 nm x 66 nm), LEDV (163 nm x 78 nm), FUKV, NISV and KRV (Ndiaye et al., 1987, Cropp et al., 1985, Sakai et al., 2015, Binger et al., 2015, Kaneko et al., 1986). Differences in reported particle dimensions are likely to result from factors such as variations in conditions for fixation and staining for electron microscopy, the presence of defective-interfering particles and end-to-end-fusion of virions.
Ledantevirus genomes consist of a single molecule of negative-sense, single-stranded RNA and range from approximately 10.8–11.5 kb.
The N, P, M, G and L share sequence homology and/or structural characteristics with the cognate proteins of other rhabdoviruses. Other proteins are encoded in the genome but have not yet been identified in infected cells. The U1 ORFs present in LDV, KEUV and KCV encode small basic proteins of 64 to 77 amino acids (7.3–8.8 kDa). The FUKV Mx ORF encodes a predicted double-membrane-spanning protein of 86 amino acids (10.4 kDa) (Walker et al., 2015, Blasdell et al., 2015).
Ledantevirus genome organisations include five genes (N, P, M, G and L) encoding the structural proteins and concise intergenic regions. (Walker et al., 2015, Sakai et al., 2015, Blasdell et al., 2015, Kading et al., 2013, Li et al., 2015). In LDV, KEUV and KCV genomes, a small additional ORF (U1) between the G and L genes occurs as an independent transcriptional unit including consensus transcription initiation and transcription termination/polyadenylation sequences; in the FUKV genome, an alternative ORF (Mx) encoding a putative double-membrane-spanning protein occurs within the M gene (Figure 1.Ledantevirus).
Figure 1.Ledantevirus. Schematic representation of ledantevirus genome organisations. N, P, M, G and L represent ORFs encoding the structural proteins. The U1 ORFs of Kern Canyon virus, Keuraliba virus and Le Dantec virus (red) and the Fukuoka virus Mx ORF (blue) are highlighted.
Serological cross-reactions (complement-fixation, indirect fluorescence antibody or ELISA) have been reported between various members of the genus. These include between: LDV and KEUV; KCV, BARV, FUKV, NKOV and KEUV; KOLEV, BARV and FUKV; and FUKV, BARV and MEBV (Calisher et al., 1989, Tesh et al., 1983, Cropp et al., 1985, Ghedin et al., 2013).
Viruses assigned to the genus infect mammals in Africa, Asia or North America. Many have been isolated from bats or arthropods feeding on bats (KCV, KOLEV, FKRV, MEBV, KRV, OITAV, WhLFV-5, KYAV) (Wiley et al., 2017, Johnson 1965, Murphy and Fields 1967, Ghedin et al., 2013, Kading et al., 2013, Metselaar et al., 1969, Binger et al., 2015, Iwasaki et al., 2004, Li et al., 2015, Goldberg et al., 2017). Others have been isolated from rodents (BARV, KEUV) or ungulates (FUKV, NISV) (Sakai et al., 2015, Kaneko et al., 1986, Karabatsos 1985). LDV was isolated from humans, initially from a young female with fever and hepatosplenomegaly and subsequently from an adult male with neurological signs; however, a causal relationship has not been established and its natural reservoir(s) and mode(s) of transmission are unknown (Cropp et al., 1985, Woodruff et al., 1977). NKOV has also been isolated from human serum (Ndiaye et al., 1987). Some of the viruses have been isolated from or detected in mosquitoes, midges, fleas, ticks or other arthropods (NKOV, KOLEV, FUKV, BARV, WhLFV-5, YjTV-2) and may be assumed to be arboviruses (Ndiaye et al., 1987, Li et al., 2015, Ghedin et al., 2013, Johnson et al., 1977, Salaun et al., 1969).
Viruses assigned to different species within the genus Ledantevirus have several of the following characteristics: A) minimum amino acid sequence divergence of 7% in L; B) minimum amino acid sequence divergence of 15% in G; C) significant differences in genome organisation as evidenced by numbers and locations of ORFs; D) can be distinguished in serological tests; and E) occupy different ecological niches as evidenced by differences in hosts and/or arthropod vectors. All members clearly meet criteria A and B. The viruses each meet the other criteria to varying extents based on available data.
Ledantevirus: from the name of the medical centre (Hôpital Aristide Le Dantec) in Dakar, Senegal, where the patient from which Le Dantec virus, a member of the type species Le Dantec ledantevirus, was first isolated. The medical centre derives its name from the French military doctor, Aristide Auguste Le Dantec, who established the first medical school in Senegal.
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