New genotypes of Liao ning virus (LNV) in Australia exhibit an insect-specific phenotype

Abstract

Liao ning virus (LNV) was first isolated in 1996 from mosquitoes in China, and has been shown to replicate in selected mammalian cell lines and to cause lethal haemorrhagic disease in experimentally infected mice. The first detection of LNV in Australia was by deep sequencing of mosquito homogenates. We subsequently isolated LNV from mosquitoes of four genera (Culex, Anopheles, Mansonia and Aedes) in New South Wales, Northern Territory, Queensland and Western Australia; the earliest of these Australian isolates were obtained from mosquitoes collected in 1988, predating the first Chinese isolates. Genetic analysis revealed that the Australian LNV isolates formed two new genotypes: one including isolates from eastern and northern Australia, and the second comprising isolates from the south-western corner of the continent. In contrast to findings reported for the Chinese LNV isolates, the Australian LNV isolates did not replicate in vertebrate cells in vitro or in vivo, or produce signs of disease in wild-type or immunodeficient mice. A panel of human and animal sera collected from regions where the virus was found in high prevalence also showed no evidence of LNV-specific antibodies. Furthermore, high rates of virus detection in progeny reared from infected adult female mosquitoes, coupled with visualization of the virus within the ovarian follicles by immunohistochemistry, suggest that LNV is transmitted transovarially. Thus, despite relatively minor genomic differences between Chinese and Australian LNV strains, the latter display a characteristic insect-specific phenotype.

Genetic, Morphological and Antigenic Relationships between Mesonivirus Isolates from Australian Mosquitoes and Evidence for Their Horizontal Transmission

“…After a final wash, the membrane was imaged with the Odyssey imaging system (LI-COR). Immunoprecipitation pulldowns were used to test antibodies that did not bind in Western blot as described previously [ 14 ]. Briefly, 60 μL of Protein G beads (Dynabeads; Thermo Fisher Scientific, Scoresby, Vic, Australia) were washed 1× with PBST before incubating with hybridoma culture supernatant on a rotary shaker for 1 h at room temperature.…”

“…A microneutralisation assay was performed as per previously described methods with modifications [ 14 , 23 , 26 ]. Briefly, serial tenfold dilutions were performed on mAb or polyclonal sera (starting undiluted or at 1/10) in RPMI media before adding 100 TCID 50 units per well of virus and incubating for 1 h at 28 °C.…”

“…There is growing evidence that the maintenance of insect-specific viruses within mosquito populations is via vertical transmission [ 12 , 13 , 14 , 15 ]. Indeed, the detection of mesoniviruses in adult male and female mosquitoes supports the hypothesis that mesoniviruses are transmitted from the female mosquito to her progeny [ 16 , 17 ], or via sexual transmission.…”

Origin and evolution of emerging Liao ning Virus (genus Seadornavirus, family Reoviridae)

“…All of the Xinjiang isolates grouped together formed the largest evolutionary branch [5,33]. All of the Australian LNV isolates were divided into two disparate lineage, one composed the isolates from eastern and northern Australia and the other included the isolates from western and southern Australia [11,12]. In this study, a comprehensive molecular phylogenetic analysis of all the LNVs isolated from China and Austrila demonstrated that the LNVs could be divide into three genotypes (Fig.…”

“…Previous researches have reported on the molecular genetic evolution of LNV isolated in China and Australia [5,7,11]. However, the data used for analysis were only limited to the local LNV isolates [5,7,11]. China in Asia and Australia in the South Pacific are located in the northern and southern hemispheres, respectively.…”