A new Tanay virus isolated from mosquitoes in Guangxi, China

Discovery of Two Novel Negeviruses in a Dungfly Collected from the Arctic

Negeviruses are a proposed group of insect-specific viruses that can be separated into two distinct phylogenetic clades, Nelorpivirus and Sandewavirus. Negeviruses are well-known for their wide geographic distribution and broad host range among hematophagous insects. In this study, the full genomes of two novel negeviruses from each of these clades were identified by RNA extraction and sequencing from a single dungfly (Scathophaga furcata) collected from the Arctic Yellow River Station, where these genomes are the first negeviruses from cold zone regions to be discovered. Nelorpivirus dungfly1 (NVD1) and Sandewavirus dungfly1 (SVD1) have the typical negevirus genome organization and there was a very high coverage of viral transcripts. Small interfering RNAs derived from both viruses were readily detected in S. furcata, clearly showing that negeviruses are targeted by the host antiviral RNA interference (RNAi) pathway. These results and subsequent in silico analysis (studies) of public database and published virome data showed that the hosts of nege-like viruses include insects belonging to many orders as well as various non-insects in addition to the hematophagous insects previously reported. Phylogenetic analysis reveals at least three further groups of negeviruses, as well as several poorly resolved solitary branches, filling in the gaps within the two sub-groups of negeviruses and plant-associated viruses in the Kitaviridae. The results of this study will contribute to a better understanding of the geographic distribution, host range, evolution and host antiviral immune responses of negeviruses.

A New Fort Crockett Virus Strain Isolated from Culicoides in Yunnan Province, China, near the China-Laos-Vietnam Border

In July 2016, a virus strain (JCC12-12) was isolated from Culicoides collected in Jiangcheng County, Yunnan Province, China. The JCC12-12 virus was sequenced using next-generation sequencing; a 9294-nt-long sequence with a G + C content of 35.63% was obtained by assembly and splicing. Phylogenetic analysis of the RNA-dependent RNA polymerase domain (RdRP) amino acid sequence showed that JCC12-12 virus shared the evolutionary branch of the Fort Crockett virus strain 22503a, isolated from Paracoccus marginatus in the United States; these viruses shared 87.5% homology, while the nucleotide homology of the JCC12-12 virus with other negeviruses was <50.8%, suggesting that JCC12-12 virus isolated from Culicoides was Fort Crockett virus. This is the first report of the Fort Crockett virus isolated from Culicoides.

Novel monoclonal antibodies against Australian strains of negeviruses and insights into virus structure, replication and host -restriction

We report the isolation of Australian strains of Bustos virus and Ngewotan virus, two insect-specific viruses in the newly identified taxon Negevirus, originally isolated from Southeast Asian mosquitoes. Consistent with the expected insect-specific tropism of negeviruses, these isolates of Ngewotan and Bustos viruses, alongside the Australian negevirus Castlerea virus, replicated exclusively in mosquito cells but not in vertebrate cells, even when their temperature was reduced to 34 °C. Our data confirmed the existence of two structural proteins, putatively one membrane protein forming the majority of the virus particle, and one glycoprotein forming a projection on the apex of the virions. We generated and characterized 71 monoclonal antibodies to both structural proteins of the two viruses, most of which were neutralizing. Overall, these data increase our knowledge of negevirus mechanisms of infection and replication in vitro.

Characterization of a Novel Tanay Virus Isolated From Anopheles sinensis Mosquitoes in Yunnan, China

Globally, mosquitoes are known to be competent vectors to various arboviruses that cause serious and debilitating diseases to humans and animals. Conversely, mosquitoes harbor a wide array of insect specific viruses (ISVs) that are generally neglected. Extensive characterization of these ISVs is important in understanding their persistence infection effect on host behavior and arbovirus transmission. Herein, we report first time isolation of Tanay virus (TANAV) isolate YN15_103_01 in Anopheles sinensis mosquitoes from Yunnan Province, China. Phylogenetically, the isolate’s nucleotide identity had more than 14.47% variance compared to previous TANAV isolates, and it clustered into an independent branch within the genus Sandewavirus in the newly proposed taxon Negevirus. TANAV growth and high titers was attained in Aag2 cells (10⁷ PFU/mL) but with no CPE observed up to 7 days.p.i. compared to C6/36 cells that exhibited extensive CPE at 48 h.p.i. with titers of 10⁷ PFU/mL. Contrarywise, the viral isolate did not replicate in vertebrate cell lines. Electron microscopy analyses showed that its final maturation process takes place in the cell cytoplasm. Notably, the predicted viral proteins were verified to be corresponding to the obtained SDS-PAGE protein bands. Our findings advance forth new and vital knowledge important in understanding insect specific viruses, especially TANAV.