Biology subjects

Tavis, J. E.

Publications and source records attributed to Tavis, J. E..

3 recordsLinked to original sources

bioRxiv2022

Metal Coordinating Inhibitors of Rift Valley Fever virus Replication

Rift Valley Fever Virus (RVFV) is a veterinary and human pathogen and is an agent of bioterrorism concern. Currently, RVFV treatment is limited to supportive care, so new drugs to control RVFV infection are urgently needed. RVFV is a member of the Bunyavirales order, and replication of these viruses depends on the viral endonuclease activity of the viral L protein. Screening for RVFV replication inhibitors among compounds with divalent cation-coordinating motifs similar to known viral nuclease inhibitors identified 31 novel RVFV inhibitors with selective indexes from 5 - 402 and 50% effective concentrations of 0.54 - 56 {micro}M in Vero cells, primarily -Hydroxytropolones and N-Hydroxypyridinediones. Inhibitor activity and selective index was validated in the human cell line A549. To evaluate specificity, select compounds were tested against another Bunyavirus, La Crosse Virus (LACV). Conservation of the enzymatic activity such as the cap-snatching mechanism among the Bunyavirales implies that the -Hydroxytropolone and N-Hydroxypyridinedione chemotypes hold potential for development into treatments for related pathogens, including Hantaan Virus, Severe fever with thrombocytopenia syndrome virus, Crimean-Congo Hemorrhagic Fever Virus, and LACV. Keywords: Rift Valley Fever Virus 1, La Crosse virus 2, Cap-snatching endonuclease 3, Replication inhibitors 4, -Hydroxytropolones 5, N-Hydroxypyridinediones 6.

microbiology↗

bioRxiv2022

Predicted structure of the hepatitis B virus polymerase reveals an ancient conserved protein fold

Hepatitis B virus (HBV) replicates by protein-primed reverse transcription. It chronically infects >250 million people, and the dominant anti-HBV drugs are nucleos(t)ide analogs targeting the viral polymerase (P). P has four domains, the terminal protein (TP) that primes DNA synthesis, a spacer, the reverse transcriptase (RT), and the ribonuclease H (RNaseH). Despite being a major drug target and catalyzing a reverse transcription pathway very different from the retroviral pathway, HBV P has resisted structural analysis for decades. Here, we exploited advances in protein structure prediction to model the structure of P. The predicted HBV RT and RNaseH domains aligned to the HIV RT-RNaseH at 3.75 [A] RMSD, had a nucleic acid binding groove spanning the two active sites, had DNA polymerase active site motifs in their expected positions, and accommodated two Mg++ ions in both active sites. Surprisingly, the TP domain wrapped around the RT domain, with the priming tyrosine poised over the RT active site. This model was validated using published mutational analyses, and by docking RT and RNaseH inhibitors, RNA:DNA heteroduplexes, and the HBV {varepsilon} RNA stem-loop that templates DNA priming into the model. The HBV P fold, including the orientation of the TP domain, was conserved among hepadnaviruses from rodents to fish and in P from a fish nackednavirus, but not in other non-retroviral RTs. Therefore, this protein fold has persisted since the hepadnaviruses diverged from nackednaviruses >400 million years ago. This model will guide drug development and mechanistic studies into Ps function. SignificanceThe hepatitis B virus (HBV) polymerase (P) catalyzes an unusual reverse transcription pathway and is a major drug target. However, Ps insolubility and instability have long prevented its structural analyses. This work predicts the structure of P proteins from human to fish viruses, revealing an unanticipated conserved protein fold that is at least 400 million years old. The HBV P model was validated by mechanistically interpreting mutations with strong phenotypes and by computationally docking nucleic acids to P and inhibitors into both of its active sites. The model will advance mechanistic studies into the function of P and enable drug discovery against targets on P other than the reverse transcriptase and ribonuclease H active sites.

microbiology↗

bioRxiv2020

Establishment of a Replicon System for Bourbon Virus and Identification of Small Molecules that Efficiently Inhibit Virus Replication

Bourbon virus (BRBV) was first isolated from a patient hospitalized at the University of Kansas Hospital in 2014. Since then, several deaths have been reported to be caused by BRBV infection in the Midwest and Southern United States. BRBV is a tick-borne virus that is widely carried by lone star ticks. It belongs to genus Thogotovirus of the Orthomyxoviridae family. Currently, there are no treatments or vaccines available for BRBV or thogotovirus infection caused diseases. In this study, we reconstituted a replicon reporter system, composed of plasmids expressing the RNA-dependent RNA polymerase (RdRP) complex (PA, PB1 and PB2), nucleocapsid (NP) protein, and a reporter gene flanked by the 3 and 5 UTR of the envelope glycoprotein (GP) genome segment. By using the luciferase reporter, we screened a few small molecule compounds of anti-endonuclease that inhibited the nicking activity by parvovirus B19 (B19V) NS1, as well as FDA-approved drugs targeting the RdRP of influenza virus. Our results demonstrated that myricetin, and an anti-B19V NS1 nicking inhibitor, efficiently inhibited the RdRP activity of BRBV and virus replication. The IC50 and EC50 of myricetin are 2.22 M and 4.6 M, respectively, in cells. Myricetin had minimal cytotoxicity in cells, and therefore the therapeutic index of the compound is high. In conclusion, the BRBV replicon system is a useful tool to study viral RNA replication and to develop antivirals, and myricetin may hold promise in treatment of BRBV infected patients.

microbiology↗