Antiviral therapy is crucial for the circumvention of
viral epidemics. The
unavailability of a specific antiviral drug against the chikungunya
virus (CHIKV) disease has created an alarming situation to identify
or develop potent chemical molecules for remedial management of CHIKV.
In the present investigation, in silico
studies of dihydrorugosaflavonoid derivatives (5a–f) with non-structural protein-3 (nsP3) were carried out.
nsP3 replication protein has recently been considered as a possible
antiviral target in which crucial inhibitors fit into the adenosine-binding
pocket of the macrodomain. The 4′-halogenated dihydrorugosaflavonoids
displayed intrinsic binding with the nsp3 macrodomain (PDB ID: 3GPO)
of CHIKV. Compounds 5c and 5d showed docking
scores of −7.54 and −6.86 kcal mol–1, respectively. Various in vitro assays were performed to confirm
their (5a–f) antiviral potential
against CHIKV. The non-cytotoxic dose was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium
bromide assay and was found to be <100 μM. The compounds 5c and 5d showed their inhibitory potential for
CHIKV, which was determined
through cytopathic effect assay and plaque reduction assay, which
show inhibition up to 95 and 92% for 70 μM concentration of
the compounds, respectively. The quantitative real-time polymerase
chain reaction assay result confirmed the ability of 5c and 5d to reduce the viral RNA level at 70 μM
concentration
of compounds to nearly 95 and 93% concentration, respectively, in
cells with CHIKV infection. Further, the CHIKV-inhibitory capacity
of these compounds was corroborated by execution of immunofluorescence
assay. The executed work will be meaningful for the future research
of studied dihydrorugosaflavonoids against prime antiviral entrants,
leading to remedial management
to preclude CHIKV infection.
<p>The reemergence of SARS-CoV
named, as SARS-CoV-2 has been highly infectious and able to infect a large
population around the globe. The World Health Organization (WHO) has declared
this SARS-CoV-2 associated Coronavirus Disease 2019 (COVID-19) as pandemic.
SARS-CoV-2 genome is translated into polyproteins and has been processed by its
protease enzymes. 3CLprotease is named as main protease (M<sup>pro</sup>)
enzyme which cleaves nsp4-nsp16. This crucial role of M<sup>pro</sup> makes
this enzyme a prime and promising antiviral target. The drug repurposing is a
fast alternative method than the discovery of novel antiviral molecules. We
have used high-throughput virtual screening approach to examine FDA approved LOPAC1280
library against M<sup>pro</sup>. Primary screening have identified few
potential drug molecule for the target among which 10 molecules were studied
further. Molecular docking of selected molecules was done to detailed study
about their binding energy and binding modes. Positively, Etoposide, BMS_195614,
KT185, Idarubicin and WIN_62577 were found interacting with substrate binding
pocket of M<sup>pro</sup> with higher binding energy. These molecules are being
advanced by our group for <i>in vitro </i>and
<i>in vivo</i> testing to study the efficacy
of identified drugs. As per our understanding, these molecules have the
potential to efficiently interrupt the viral life cycle and may reduce or
eliminate the expeditious outspreading of SARS-CoV-2.</p>
Arthropod-borne viruses of the alphavirus and flavivirus genera are human pathogens of significant concern, and currently, no specific antiviral treatment is available for these viruses. In this study, the antiviral mechanisms of natural small molecules against Dengue virus (DENV) and Chikungunya virus (CHIKV) have been investigated. Herbacetin (HC) and Caffeic acid phenethyl ester (CAPE) showed depletion of polyamine levels in Vero cells as demonstrated by thin-layer chromatography (TLC). As polyamines are known to play a role in viral replication and transcription, HC and CAPE were expected to inhibit virus replication by reducing polyamine levels. To test this hypothesis, HC and CAPE were evaluated for antiviral activities using a cell-based virus yield assay by quantitative reverse transcription-polymerase chain reaction (qRT-PCR), plaque reduction assay, and immunofluorescence assay (IFA). HC and CAPE displayed potent inhibition with EC50 of 463 nM and 0.417 nM for CHIKV and 8.5 uM and 1.15 uM for DENV, respectively. Interestingly, however, the addition of exogenous polyamines did not completely rescue the virus titer in both CHIKV and DENV infected cells and this indicated additional antiviral mechanisms for HC and CAPE. Further, in silico analysis indicated that HC and CAPE directly target the viral methyltransferases (MTase) of CHIKV and DENV. A high throughput ELISA-based assay that quantifies m7GMP-nsP1 adduct was employed to validate inhibition of CHIKV nsP1 MTase and IC50 was calculated to be 0.009 uM and 0.08 uM for CAPE and HC respectively. Altogether, the identification of natural small molecules as antivirals opens the door for the development of antiviral therapies for the treatment of CHIKV and DENV infections.
BACKGROUND: Emergence of new pathogenic viruses along with adaptive potential of RNA viruses has become a major public health concern. Hence it becomes even more important to explore and evaluate the antiviral properties of nanocomposites which is an ever-evolving field of medical biology. METHODS: In this study, series of metal/metal oxide (Ag/NiO : NiO, AN-5%, AN-10% and AN-15%) and ternary metal oxide nanocomposites (Ag2O/NiO/ZnO : N/Z, A/N/Z-1, A/N/Z-2 and A/N/Z-3) have been synthesized and characterized. Cellular uptake of nanocomposites was confirmed by ICP-MS. RESULTS: Intriguingly, molecular docking of metal oxides in the active site of nsP3 validated the binding of nanocomposites to chikungunya virus replication protein nsP3. In-vitro antiviral potential of nanocomposites were tested by performing plaque reduction assay, cytopathic effect (CPE) analysis and qRT-PCR. The nanocomposites showed significant reduction in virus titre. Half-maximal inhibitory concentration (IC50) for A/N/Z-3 and AN-5% were determined to be 2.828 and 3.277 g/mL, respectively. CPE observation and qRT-PCR results were consistent with the data obtained from plaque reduction assay for A/N/Z-3 and AN-5%. CONCLUSION: These results, have opened new avenues for development of nanocomposites based antiviral therapies.
Emerging variants of SARS-CoV-2 still threaten the effectiveness of currently deployed vaccines, and antivirals can prove to be an effective therapeutic option for attenuating it. The papain-like protease (PLpro) is an attractive target due to its sequence conservation and critical role in the replication and pathogenesis of SARS-CoV-2. PLpro also plays very important role in modulation of host immune responses by deubiquitinating (DUBs) or deISGylating host proteins. Thus, targeting PLpro serves as a two-pronged approach to abate SARS-CoV-2. Due to its structural and functional similarities with the host DUB enzymes, an in-house library of DUB inhibitors was constituted in this study. Five promising compounds exhibiting high binding affinities with the substrate binding site of PLpro were identified from a library of 81 compounds with in silico screening, docking, and simulation studies. Interestingly, lithocholic acid, linagliptin, teneligliptin, and flupenthixol significantly inhibited the proteolytic activity of PLpro. Each of these compounds abrogated in vitro replication of SARS-CoV-2 with EC50 values in the range of 5-21 micro M. In addition, crystal structure of SARS-CoV-2 PLpro and its complex with inhibitors have been determined that revealed their inhibitory mechanism. The findings of this study provide the proof-of-principle that the DUB inhibitors hold high potential as a new class of therapeutics against SARS-CoV-2. Additionally, this is the first study that has opened a new avenue towards not only targeting PLpro active site but also simultaneously directing towards restoration of antiviral immune response of the host for deterring SARS-CoV-2.
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