Emerging concepts about the evolutionary history of hantaviruses
Abstract number: O83
Kang H.J., Bennett S.N., Sumibcay L., Arai S., Hope A.G., Cook J.A., Song J.W., Yanagihara R.
Objective: Recent discovery of genetically distinct hantaviruses in shrews (family Soricidae), captured in widely separated geographic regions, challenges the conventional view that rodents are the principal and progenitor reservoir hosts of hantaviruses, and raises the possibility that other soricomorphs, notably moles (family Talpidae), harbour hantaviruses.
Methods: Using oligonucleotide primers based on conserved genomic regions of rodent- and soricid-borne hantaviruses, RNA extracts from tissues of the Japanese shrew mole (Urotrichus talpoides), American shrew mole (Neurotrichus gibbsii) and European common mole (Talpa europaea) were analyzed for hantavirus sequences by RT-PCR. Newfound S-, M- and L-segment sequences were aligned using Clustal W and were analyzed phylogenetically by the maximum-likelihood and Markov Chain Monte Carlo tree-sampling methods, with the GTR+I+G model of evolution.
Results: Novel hantavirus genomes, designated Asama virus (ASAV), Oxbow virus (OXBV) and Nova virus (NVAV), were detected in tissues of Urotrichus talpoides, Neurotrichus gibbsii and Talpa europaea, respectively. Sequence and phylogenetic analyses indicated that ASAV and OXBV were related to hantaviruses harboured by soricine shrews in Eurasia and North America, respectively. By contrast, phylogenetic analyses of full-length S- and L-segment sequences showed that NVAV formed a unique clade, clearly distinct and evolutionarily distant from all other hantaviruses. Despite the high degree of sequence divergence at the nucleotide and amino acid levels, the secondary structures of the nucleocapsid proteins, as well as the L-segment motifs, of the mole-associated hantaviruses were well conserved.
Conclusions: While cross-species transmission has influenced the course of hantavirus evolution, such host-switching events alone do not satisfactorily explain the co-existence and distribution of genetically distinct hantaviruses among species in two taxonomic orders of small mammals spanning four continents. When viewed within the context of molecular phylogeny and zoogeography, the close association between distinct hantavirus clades and specific subfamilies of rodents, shrews and moles is likely the result of alternating and variable periodic co-divergence at certain taxonomic levels through evolutionary time. Thus, the primeval hantavirus might have arisen from an insect-borne virus, with ancestral soricomorphs, rather than rodents, serving as the original mammalian hosts.
|Session name:||19th European Congress of Clinical Microbiology and Infectious Diseases|
|Location:||Helsinki, Finland, 16 - 19 May 2009|
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