Genomic characterization of orthobunyavirus of veterinary importance in America

A Review of Omics Studies on Arboviruses: Alphavirus, Orthobunyavirus and Phlebovirus

Since the intricate and complex steps in pathogenesis and host-viral interactions of arthropod-borne viruses or arboviruses are not completely understood, the multi-omics approaches, which encompass proteomics, transcriptomics, genomics and metabolomics network analysis, are of great importance. We have reviewed the omics studies on mosquito-borne viruses of the Togaviridae, Peribuyaviridae and Phenuiviridae families, specifically for Chikungunya, Mayaro, Oropouche and Rift Valley Fever viruses. Omics studies can potentially provide a new perspective on the pathophysiology of arboviruses, contributing to a better comprehension of these diseases and their effects and, hence, provide novel insights for the development of new antiviral drugs or therapies.

First report of antiviral activity of nordihydroguaiaretic acid against Fort Sherman virus (Orthobunyavirus)

The genus Orthobunyavirus are a group of viruses within arbovirus, with a zoonotic cycle, some of which could lead to human infection. A characteristic of these viruses is their lack of antiviral treatment or vaccine for its prevention. The objective of this work was to study the in vitro antiviral activity of nordihydroguaiaretic acid (NDGA), the most important active compound of Larrea divaricata Cav. (Zigophyllaceae), against Fort Sherman virus (FSV) as a model of Orthobunyavirus genus. At the same time, the effect of NDGA as a lipolytic agent on the cell cycle of this viral model was assessed. The method of reducing plaque forming units on LLC-MK2 cells was used to detect the action of NDGA on CbaAr426 and SFCrEq231 isolates of FSV. NDGA did not show virucidal effect, but it had antiviral activity with a similar inhibition in both isolates, which was dose dependent. It was established that the NDGA has a better inhibition 1-h post-internalization (p.i.), showing a different behavior in each isolate, which was dependent upon the time p.i. Since virus multiplication is dependent on host cell lipid metabolism, the antiviral effect of NDGA has been previously related to its ability to disturb the lipid metabolism, probably by interfering with the 5-lipoxigenase (5-LOX) and the sterol regulatory element-binding proteins (SREBP) pathway. We determined by using caffeic acid, a 5-LOX inhibitor, that the inhibition of this enzyme negatively affected the FSV replication; and by means of resveratrol, a SREBP1 inhibitor, it was showed that the negative regulation of this pathway only had action on the SFCrEq231 reduction. In addition, it was proved that the NDGA acts intracellularly, since it showed the ability to incorporate into LLC-MK2 cells. The information provided in this work converts the NDGA into a compound with antiviral activity in vitro against FSV (Orthobunyavirus), which can be subjected to structural modifications in the future to improve the activity.

Identification of animal hosts of Fort Sherman virus, a New World zoonotic orthobunyavirus

An orthobunyavirus termed Fort Sherman virus (FSV) was isolated in 1985 from a febrile US soldier in Panama, yet potential animal reservoirs remained unknown. We investigated sera from 192 clinically healthy peri-domestic animals sampled in northeastern Brazil during 2014-2018 by broadly reactive RT-PCR for orthobunyavirus RNA, including 50 cattle, 57 sheep, 35 goats and 50 horses. One horse sampled in 2018 was positive (0.5%; 95% CI, 0.01-3.2) at 6.2 × 10³ viral RNA copies/mL. Genomic comparisons following virus isolation in Vero cells and deep sequencing revealed high identity of translated amino acid sequences between the new orthobunyavirus and the Panamanian FSV prototype (genes: L, 98.8%; M, 83.5%; S, 100%), suggesting these viruses are conspecific. Database comparisons revealed even higher genomic identity between the Brazilian FSV and taxonomically unassigned Argentinian mosquito- and horse-derived viruses sampled in 1965, 1982 and 2013 with only 1.1% maximum translated amino acid distances across viral genes, suggesting the Argentinian viruses were also distinct FSV strains. The Panamanian FSV strain was an M gene reassortant relative to all Southern American FSV strains, clustering phylogenetically with Cache Valley virus (CVV). Mean dN/dS ratios among FSV genes ranged from 0.03 to 0.07, compatible with strong purifying selection. FSV-specific neutralizing antibodies occurred at relatively high end-point titres in the range of 1:300 in 22.0% of horses (11 out of 50 animals), 8.0% of cattle (4/50 animals), 7.0% of sheep (4/57 animals) and 2.9% of goats (1/35 animals). High specificity of serologic testing was suggested by significantly higher overall FSV-specific compared to CVV- and Bunyamwera virus-specific end-point titres (p = .009), corroborating a broad vertebrate host range within peri-domestic animals. Growth kinetics using mosquito-, midge- and sandfly-derived cell lines suggested Aedes mosquitos as potential vectors. Our findings highlight the occurrence of FSV across a geographic range exceeding 7,000 km, surprising genomic conservation across a time span exceeding 50 years, M gene-based reassortment events, and the existence of multiple animal hosts of FSV.