Potentiation of the antiviral activity of poly r(A-U) by riboflavin, FAD and FMN

Therapeutic Promises of Plant Metabolites against Monkeypox Virus: An In Silico Study

The monkeypox virus was still spreading in May 2022, with the first case identified in a person with travel ties to Nigeria. Using molecular docking-based techniques, we evaluated the efficiency of different bioactive chemicals obtained from plants against the monkeypox virus. A total of 56 plant compounds were evaluated for antimonekypox capabilities, with the top four candidates having a higher binding affinity than the control. We targeted the monkeypox profilin-like protein, which plays a key role in viral replication and assembly. Among the metabolites, curcumin showed the strongest binding affinity with a value of -37.43 kcal/mol, followed by gedunin (-34.89 kcal/mol), piperine (-34.58 kcal/mol), and coumadin (-34.14 kcal/mol). Based on ADME and toxicity assessments, the top four substances had no negative impacts. Furthermore, four compounds demonstrated resistance to deformability, which was corroborated by normal mode analysis. According to the bioactivity prediction study, the top compound target class was an enzyme, membrane receptor, and oxidoreductase. Furthermore, the study discovered that wortmannin, a gedunin analogue, can behave as an orthopoxvirus. The study found that these bioactive natural drug candidates could potentially work as monkeypox virus inhibitors. We recommended further experimental validation to confirm the promising findings of the study.

Modulation of the Antiviral Activity of Poly (A-U) by Ethidium Bromide and Propidium Iodide

The role of ethidium bromide (EB) and propidium iodide (PI) in modulating the antiviral and interferon-inducing activities of poly(adenylate-uridylate) (poly (A-U)) was examined using the human foreskin fibroblast-vesicular stomatitis virus (HSF-VSV) bioassay system in which the concentration of poly (A-U) was fixed at 0.05 mM or 0.2 mM while the EB or PI concentration was varied to produce variable EB (or PI)/ribonucleotide ratios ranging from 1:16 to 2:1. EB, PI and poly (A-U) tested individually were not efficacious antiviral agents. When poly (A-U) was combined with the ethidium bromide or propidium iodide the antiviral activity was potentiated 15- to 22-fold at EB (or PI)/ribonucleotide ratios in the region of 1/4. The interferon-inducing activity of the EB (or PI)/poly (A-U) combinations were equal to the sum of the interferon-inducing activity of the poly (A-U) and the EB or (PI). These results indicate that the EB and PI potentiate the antiviral activity of the poly (A-U) without superinduction of interferon. The direct viral inactivation study demonstrated that EB, PI, poly (A-U) and the EB (or PI)/poly (A-U) combinations did not inactivate the VSV at concentrations near the 50% viral inhibitory dose.

RNA–Intercalating Agent Interactions: in vitro Antiviral Activity Studies

Twenty intercalating agents were tested to examine the effects of intercalating dye-induced perturbations upon the antiviral activity of poly (adenylate–uridylate) [poly (A-U)]. Neither poly (A-U) alone nor each intercalative dye was an efficacious antiviral agent. When poly (A-U) was combined with major groove intercalating dyes (acridine orange or proflavine), no synergism was observed. When poly (A-U) was combined with minor groove intercalating dyes [ethidium (EB), propidium (PI), adriamycin (ADR) or daunomycin (DMN)] or minor/major groove intercalating dyes [9-aminoacridine (9-AA), N2-methyl-9-hydroxy-ellipticine (NMHE) or N2,N6-dimethyl-9-hydroxy-ellipticine (DMHE)] the 50% effective doses (ED50) of the poly (A-U), 9-AA, ADR, DMHE, DMN, EB, NMHE and PI decreased 18-, 22-, 60-, 274-, 61-, 154-, 113- and 299-fold, respectively. When poly (A-U) was combined individually with 11 dyes whose mode of intercalation was not known, the ED50 of ametantrone (HAQ), chloroquine (CHL), mitoxantrone (DHAQ) and quinine (QUI) decreased 125-, 65-, 251- and 32-fold, respectively. These results suggest that the four dyes may intercalate into poly (A-U) from the minor groove. Ten (ADR, CHL, DMN, DHAQ, DMHE, EB, HAQ, NMHE, PI, QUI) of the 20 dyes evaluated exhibited significant synergism with poly (A-U), as quantified by the fractional inhibitory concentration index. Interferon (IFN) neutralization assays demonstrated that the IFN-inducing capability of the dye/poly (A-U) combinations approximated the sum of the capabilities of the poly (A-U) and the dyes employed. These results suggest that the majority of the dyes tested potentiate the antiviral activity of poly (A-U) without affecting the amount of IFN induced.

The antiviral activity of RNA-dye combinations

The results of our previous studies (Jamison et al. 1988, 1989, 1990 a, b, c, d, e) have shown that the ability of intercalative dyes to modulate the antiviral activity of poly r(A-U) is related to the groove through which the dyes intercalate into the poly r(A-U). When poly r(A-U) is combined with the minor groove intercalating dyes or the minor/major groove intercalating dyes, optimum enhancement of antiviral activity is observed at the dye/ribonucleotide ratio predicted by the neighbor exclusion model (usually 1/4 or 1/6). No enhancement is observed when poly r(A-U) is combined with major groove intercalating dyes. When poly r(A-U) is combined with additional intercalative dyes to produce a dye/ribonucleotide ratio of 1/4 and a ribonucleotide concentration of 200 microM, the antiviral activity of poly r(A-U) is enhanced 8- to 20-fold, while 50% effective doses of the poly r(A-U) and the dyes decreases 18- to 347-fold. Interferon neutralization assays demonstrate that the interferon-inducing capability of the dye/poly r(A-U) combinations approximates the sum of the interferon-inducing capabilities of the poly r(A-U) and the dyes employed and suggests that the dyes potentiate the antiviral activity of poly r(A-U) without affecting the amount of interferon induced. Direct viral inactivation studies demonstrate that the dyes, poly r(A-U), and the dye/poly r(A-U) combinations do not inactivate VSV at concentrations near the 50% viral inhibitory dose. Assessment of cytotoxicity by microscope examination of HSF cell morphology and trypan blue exclusion indicates that the dye/poly r(A-U) combinations exhibit antiviral activity at concentrations well below those that induce cyto-toxicity. Several of the dyes and the dye/poly r(A-U) combinations exhibit anti-HIV-1 activity, suggesting that the enhancement phenomenon is not virus-specific nor host cell-specific. The enhancement phenomenon is sensitive to the base sequence of the polynucleotide with dye/poly r(A-U) and dye/poly r(G-C) combinations displaying enhanced antiviral activity, while dye/poly (rI).poly (rC) and dye/poly d(A-T) combinations do not. These results suggest that while intercalation of the dye and interferon induction are necessary for enhanced antiviral activity, neither intercalation nor interferon induction alone is sufficient to potentiate the antiviral activity of polyribonucleotides.

In vitro antiviral activity of poly (A-U) and ellipticines

The role of N2-methyl-9-hydroxy-ellipticine (NMHE) and N2,N6-dimethyl-9-hydroxy-ellipticine (DMHE) in modulating the antiviral activity of poly (A-U) was examined using a human foreskin fibroblast-vesicular stomatitis virus (HSF-VSV) bioassay in which the concentration of poly (A-U) was fixed at 0.05 mM or 0.2 mM while the NMHE or DMHE concentration was varied to produce variable NMHE (or DMHE)/ribonucleotide ratios ranging from 1:16 to 2:1. Poly (A-U), NMHE and DMHE tested individually were not efficacious antiviral agents. When the poly (A-U) was combined with the NMHE or DMHE, the antiviral activity of the poly (A-U) was potentiated 16- to 20-fold a NMHE (or DMHE)/ribonucleotide ratios in the region of 1/4. Poly (A-U), NMHE and DMHE induce beta-IFN. The interferon-inducing activity of the NMHE (or DMHE)/poly (A-U) combination was equal to the sum of the interferon-inducing activity of the poly (A-U) alone and the NMHE (or DMHE) alone. The direct viral inactivation study demonstrated that NMHE, DMHE, poly (A-U) and the NMHE (or DMHE)/poly (A-U) combinations did not inactivate VSV at concentrations near the 50% viral inhibitory dose. Photomicrographs of HSF cells incubated with NMHE alone or with a NMHE/poly (A-U) combination suggest that poly (A-U) affects the subcellular distribution of the NMHE by steering the NMHE to the nucleolus. These observations suggest that modulation of a nuclear process may be responsible for the enhanced antiviral activity.

Enhancement of the antiviral activity of poly r(A-U) by ametantrone and mitoxantrone

The role of ametantrone (HAQ) and mitoxantrone (DHAQ) in modulating the antiviral and interferon-inducing activities of poly r(A-U) was examined using the human foreskin fibroblast-vesicular stomatitis virus (HSF-VSV) bioassay system in which the concentration of poly r(A-U) was fixed at 0.05 mM or 0.2 mM while the HAQ or DHAQ concentration was varied to produce variable HAQ (or DHAQ)/ribonucleotide ratios ranging from 1:16 to 2:1. HAQ, DHAQ and poly r(A-U) tested individually were not efficacious antiviral agents. When poly r(A-U) was combined with the ametantrone or mitoxantrone the antiviral activity was potentiated 10-fold at HAQ (or DHAQ)/ribonucleotide ratios in the region of 1/4 to 1/6. The interferon-inducing activity of the HAQ (or DHAQ)/poly r(A-U) combinations were equal to the sum of the interferon-inducing activity of the poly r(A-U) and the HAQ (or DHAQ). These results indicate that the HAQ and DHAQ potentiate the antiviral activity of the poly r(A-U) without the superinduction of interferon. The direct viral inactivation study demonstrated that HAQ, DHAQ, poly r(A-U) and the HAQ (or DHAQ)/poly r(A-U) combinations did not inactivate the VSV at concentrations near the viral 50% inhibitory dose.