Abstract
Liao ning virus (LNV) is related to Banna virus, a known human-pathogen present in south-east Asia. Both viruses belong to the genus Seadornavirus, family Reoviridae. LNV causes lethal haemorrhage in experimentally infected mice. Twenty seven isolates of LNV were made from mosquitoes collected in different locations within the Xinjiang province of north-western China during 2005. These mosquitoes were caught in the accommodation of human patients with febrile manifestations, or in animal barns where sheep represent the main livestock species. The regions where LNV was isolated are affected by seasonal encephalitis, but are free of Japanese encephalitis (JE). Genome segment 10 (Seg-10) (encoding cell-attachment and serotype-determining protein VP10) and Seg-12 (encoding non-structural protein VP12) were sequenced for multiple LNV isolates. Phylogenetic analyses showed a less homogenous Seg-10 gene pool, as compared to segment 12. However, all of these isolates appear to belong to LNV type-1. These data suggest a relatively recent introduction of LNV into Xinjiang province, with substitution rates for LNV Seg-10 and Seg-12, respectively, of 2.29×10−4 and 1.57×10−4 substitutions/nt/year. These substitution rates are similar to those estimated for other dsRNA viruses. Our data indicate that the history of LNV is characterized by a lack of demographic fluctuations. However, a decline in the LNV population in the late 1980s - early 1990s, was indicated by data for both Seg-10 and Seg-12. Data also suggest a beginning of an expansion in the late 1990s as inferred from Seg-12 skyline plot.
Highlights
The genus Seadornavirus encompasses mosquito-borne 12 segmented dsRNA viruses that have been isolated in South-east Asia
This paper describes a survey of arboviruses in North-east China, which was intended to identify emerging or re-merging viruses circulating in the region, including flaviviruses (such as Japanese encephalitis virus (JEV)), alphaviruses and Banna virus
Sequence analyses Sequence analyses of segment 10 (Seg-10) and segment 12 (Seg-12) and comparisons to published data, showed that all 27 isolates belong to Liao ning virus (LNV)-1 [14,15]
Summary
The genus Seadornavirus encompasses mosquito-borne 12 segmented dsRNA viruses that have been isolated in South-east Asia. The genus is classified within family Reoviridae, subfamily Sedoreovirinae [1], and contains 3 recognised species, Banna virus (BAV), Kadipiro virus (KDV) and Liao ning virus (LNV) [2]. Structural analysis of outer-capsid proteins of BAV showed an ancestral relationship to the rotaviruses, which are non-vectored enteric dsRNA viruses belonging to the family Reoviridae [6]. Banna virus was first isolated from cerebrospinal fluids (CSF) (2 isolates) and sera (25 isolates) of patients with encephalitis in the Yunnan province (Xishuang Banna prefecture) of southern China in 1987. It was isolated in 1992 from patients with fever and flu-like manifestation [7] in the Xinjiang province. In contrast Kadipiro virus has only been isolated from mosquitoes [3]
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