Discovery of berberine, abamectin and ivermectin as antivirals against chikungunya and other alphaviruses

Unlocking the potential of Berberine: Advancing cancer therapy through chemosensitization and combination treatments

Despite considerable progress in cancer treatment options, resistance to chemotherapeutic drugs remains a significant challenge. This review focuses on Berberine (BBR), an isoquinoline alkaloid found in various medicinal plants, which has garnered attention in the field of oncology for its anticancer potential either alone or in combination with other compounds and its ability to modulate chemoresistance, acting as a natural chemosensitizer. BBR's ability to modulate chemoresistance is attributed to its diverse mechanisms of action, including inducing DNA breaks, inhibition of drug efflux pumps, modulation of apoptosis and necroptosis, downregulating multidrug resistance genes, enhancing immune response, suppressing angiogenesis and targeting multiple pathways within cancer cells, including protein kinase B/mammalian target of rapamycin (Akt/mTOR), epidermal growth factor receptor (EGFR), mitogen-activated protein kinase (MAPK), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), poly(ADP-ribose) polymerase (PARP1), janus kinase/signal transducers and activators of transcription (JAK-STAT), Wnt/β-catenin etc. Moreover, BBR, in combination with other compounds, also offers a promising approach to cancer therapy, enforcing its broad-spectrum anticancer effects. Therefore, this review aims to elucidate the intricate mechanism of action of BBR in combinatorial therapy as a potential chemosensitizer to increase the efficiency of several drugs, including cisplatin, doxorubicin, lapatinib, tamoxifen, irinotecan, niraparib, etc. in various cancers. Additionally, this review briefly covers the origin and biological activities of BBR, exploring the specific actions underlying its anticancer effects. Further, pharmacokinetic properties of BBR are also discussed, providing insight into its therapeutic potential and optimization of its use in cancer treatment.

Recent Applications of Protoberberines as Privileged Starting Materials for the Development of Novel Broad-Spectrum Antiviral Agents: A Concise Review (2017-2023)

Berberine is a well-known phytochemical with significant antiviral activity against a wide range of viruses. Due to having a unique backbone consisting of four interconnected rings, it can be used as a platform for the design and development of novel semisynthetic antiviral agents. The question here is whether novel broad-spectrum antiviral drugs with enhanced activity and toxicity potential can be obtained by attempting to modify the structure of this privileged lead compound. The present study aims to review the results of recent studies in which berberine and its close analogues (protoberberine alkaloids) have been used as starting materials for the production of new semisynthetic antiviral structures. For this purpose, relevant studies published in high-quality journals indexed in databases such as Scopus, Web of Science, PubMed, etc. in the time frame of 2017 to 2023 were collected. Our selection criterion in the current review focuses on the studies in which protoberberines were used as starting materials for the production of semisynthetic agents with antiviral activity during the indicated time period. Correspondingly, studies were identified in which semisynthetic derivatives with significant inhibitory activity against a wide range of viruses including human immunodeficiency virus (HIV), enterovirus 71 (EV71), zika virus (ZIKV), influenza A/B, cytomegalovirus (CMV), respiratory syncytial virus (RSV), and coxsackieviruses were designed and synthesized. Our conclusion is that, despite the introduction of diverse semisynthetic derivatives of berberine with improved activity profiles compared to the parent natural leads, sufficient derivatization has not been done yet and more studies are needed.

Recent advances towards natural plants as potential inhibitors of SARS-Cov-2 targets

CONTEXT

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is still ongoing and currently the most striking epidemic disease. With the rapid global spread of SARS-CoV-2 variants, new antivirals are urgently needed to avert a more serious crisis. Inhibitors from traditional medicines or natural plants have shown promising results to fight COVID-19 with different mechanisms of action.

OBJECTIVES

To provide comprehensive and promising approaches to the medical community in the fight against this epidemic by reviewing potential plant-derived anti-SARS-CoV-2 inhibitors.

METHODS

Structural databases such as TCMSP (http://lsp.nwu.edu.cn/tcmsp.php), TCM Database @ Taiwan (http://tcm.cmu.edu.tw/), BATMAN-TCM (http://bionet.ncpsb.org/batman-tcm/) and TCMID (http://www.megabionet.org/tcmid/), as well as PubMed, Sci Finder, Research Gate, Science Direct, CNKI, Web of Science and Google Scholar were searched for relevant articles on TCMs and natural products against SARS-CoV-2.

RESULTS

Seven traditional Chinese medicines formulas have unique advantages in regulating the immune system for treating COVID-19. The plant-derived natural compounds as anti-SARS-CoV-2 inhibitors were identified based on 5 SARS-CoV-2 key proteins, namely, angiotensin-converting enzyme 2 (ACE2), 3 C-like protease (3CLpro), papain-like protease (PLpro), spike (S) protein, and nucleocapsid (N) protein.

CONCLUSIONS

A variety of natural products, such as flavonoids, terpenoids, phenols, and alkaloids, were identified, which could be used as potential SASR-Cov-2 inhibitors. These shed new light on the efficient discovery of SASR-Cov-2 inhibitors from natural products.

Synergistic In Vitro Antiviral Effect of Combinations of Ivermectin, Essential Oils, and 18-(Phthalimid-2-yl)ferruginol against Arboviruses and Herpesvirus

Combining antiviral drugs with different mechanisms of action can help prevent the development of resistance by attacking the infectious agent through multiple pathways. Additionally, by using faster and more economical screening methods, effective synergistic drug candidates can be rapidly identified, facilitating faster paths to clinical testing. In this work, a rapid method was standardized to identify possible synergisms from drug combinations. We analyzed the possible reduction in the antiviral effective concentration of drugs already approved by the FDA, such as ivermectin (IVM), ribavirin (RIBA), and acyclovir (ACV) against Zika virus (ZIKV), Chikungunya virus (CHIKV), and herpes virus type 2 (HHV-2). Essential oils (EOs) were also included in the study since they have been reported for more than a couple of decades to have broad-spectrum antiviral activity. We also continued studying the antiviral properties of one of our patented molecules with broad-spectrum antiviral activity, the ferruginol analog 18-(phthalimid-2-yl)ferruginol (phthFGL), which presented an IC99 of 25.6 μM for the three types of virus. In general, the combination of IVM, phthFGL, and oregano EO showed the greatest synergism potential against CHIKV, ZIKV, and HHV-2. For instance, this combination achieved reductions in the IC99 value of each component up to ~8-, ~27-, and ~12-fold for CHIKV, respectively. The ternary combination of RIBA, phthFGL, and oregano EO was slightly more efficient than the binary combination RIBA/phthFGL but much less efficient than IVM, phthFGL, and oregano EO, which indicates that IVM could contribute more to the differentiation of cell targets (for example via the inhibition of the host heterodimeric importin IMP α/β1 complex) than ribavirin. Statistical analysis showed significant differences among the combination groups tested, especially in the HHV-2 and CHIKV models, with p = 0.0098. Additionally, phthFGL showed a good pharmacokinetic profile that should encourage future optimization studies.

In Vitro Analyses of the Multifocal Effects of Natural Alkaloids Berberine, Matrine, and Tabersonine against the O'nyong-nyong Arthritogenic Alphavirus Infection and Inflammation

O'nyong-nyong virus (ONNV) is a member of the reemerging arthritogenic alphaviruses that cause chronic debilitating polyarthralgia and/or polyarthritis via their tropism for the musculoskeletal system. Thus, the discovery of dual antiviral and anti-inflammatory drugs is a great challenge in this field. We investigated the effects of the common plant-derived alkaloids berberine (isoquinoline), matrine (quinolizidine), and tabersonine (indole) at a non-toxic concentration (10 μM) on a human fibroblast cell line (HS633T) infected by ONNV (MOI 1). Using qRT-PCR analyses, we measured the RNA levels of the gene coding for the viral proteins and for the host cell immune factors. These alkaloids demonstrated multifocal effects by the inhibition of viral replication, as well as the regulation of the type-I interferon antiviral signaling pathway and the inflammatory mediators and pathways. Berberine and tabersonine proved to be the more valuable compounds. The results supported the proposal that these common alkaloids may be useful scaffolds for drug discovery against arthritogenic alphavirus infection.

Increased In Vivo Exposure of N-(4-Hydroxyphenyl) Retinamide (4-HPR) to Achieve Plasma Concentrations Effective against Dengue Virus

N-(4-hydroxyphenyl) retinamide (4-HPR, or fenretinide) has promising in vitro and in vivo antiviral activity against a range of flaviviruses and an established safety record, but there are challenges to its clinical use. This study evaluated the in vivo exposure profile of a 4-HPR dosage regime previously shown to be effective in a mouse model of severe dengue virus (DENV) infection, comparing it to an existing formulation for human clinical use for other indications and developed/characterised self-emulsifying lipid-based formulations of 4-HPR to enhance 4-HPR in vivo exposure. Pharmacokinetic (PK) analysis comprising single-dose oral and IV plasma concentration-time profiles was performed in mice; equilibrium solubility testing of 4-HPR in a range of lipids, surfactants and cosolvents was used to inform formulation approaches, with lead formulation candidates digested in vitro to analyse solubilisation/precipitation prior to in vivo testing. PK analysis suggested that effective plasma concentrations could be achieved with the clinical formulation, while novel lipid-based formulations achieved > 3-fold improvement. Additionally, 4-HPR exposure was found to be limited by both solubility and first-pass intestinal elimination but could be improved through inhibition of cytochrome P450 (CYP) metabolism. Simulated exposure profiles suggest that a b.i.d dosage regime is likely to maintain 4-HPR above the minimum effective plasma concentration for anti-DENV activity using the clinical formulation, with new formulations/CYP inhibition viable options to increase exposure in the future.

Ethyl palmitate, an anti-chikungunya virus principle from Sauropus androgynus, a medicinal plant used to alleviate fever in ethnomedicine

ETHNOPHARMACOLOGICAL RELEVANCE

Sauropus androgynus is a medicinal shrub used for the treatment of fever in ethnomedical traditions in various Southeast Asian countries.

AIM OF THE STUDY

This study was aimed to identify antiviral principles from S. androgynus against Chikungunya virus (CHIKV), a major mosquito-borne pathogen that re-emerged in the last decade, and to unravel their mechanism of action.

MATERIALS AND METHODS

Hydroalcoholic extract of S. androgynus leaves was screened for anti-CHIKV activity using cytopathic effect (CPE) reduction assay. The extract was subjected to activity guided isolation and the resultant pure molecule was characterized by GC-MS, Co-GC and Co-HPTLC. The isolated molecule was further evaluated for its effect by plaque reduction assay, Western blot and immunofluorescence assays. In silico docking with CHIKV envelope proteins and molecular dynamics simulation (MD) analyses were used to elucidate its possible mechanism of action.

RESULTS

S. androgynus hydroalcoholic extract showed promising anti-CHIKV activity and its active component, obtained by activity guided isolation, was identified as ethyl palmitate (EP), a fatty acid ester. At 1 μg/mL, EP led to 100% inhibition of CPE and a significant 3 log₁₀ reduction in CHIKV replication in Vero cells at 48 h post-infection. EP was highly potent with an EC₅₀ of 0.0019 μg/mL (0.0068 μM) and a very high selectivity index. EP treatment significantly reduced viral protein expression, and time of addition studies revealed that it acts at the stage of viral entry. A strong binding to the viral envelope protein E1 homotrimer during entry, thus preventing viral fusion, was identified as a possible mechanism by which EP imparts its antiviral effect.

CONCLUSIONS

S. androgynus contains EP as a potent antiviral principle against CHIKV. This justifies the use of the plant against febrile infections, possibly caused by viruses, in various ethnomedical systems. Our results also prompt more studies on fatty acids and their derivatives against viral diseases.

Ameliorating the antiparasitic activity of the multifaceted drug ivermectin through a polymer nanocapsule formulation

Ivermectin (IVM) is a potent antiparasitic widely used in human and veterinary medicine. However, the low oral bioavailability of IVM restricts its therapeutic potential in many parasitic infections, highlighting the need for novel formulation approaches. In this study, poly(ε-caprolactone) (PCL) nanocapsules containing IVM were successfully developed using the nanoprecipitation method. Pumpkin seed oil (PSO) was used as an oily core in the developed nanocapsules. Previously, PSO was chemically analyzed by headspace solid-phase microextraction coupled to gas chromatography/mass spectrometry (HS-SPME/GC-MS). The solubility of IVM in PSO was found to be 4,266.5 ± 38.6 μg/mL. In addition, the partition coefficient of IVM in PSO/water presented a logP of 2.44. A number of nanocapsule batches were produced by factorial design resulting in an optimized formulation. Negatively charged nanocapsules measuring around 400 nm demonstrated unimodal size distribution, and presented regular spherical morphology under transmission electron microscopy. High encapsulation efficiency (98-100%) was determined by HPLC. IVM-loaded capsules were found to be stable in nanosuspensions at 4°C and 25°C, with no significant variations in particle size observed over a period of 150 days. Nanoencapsulated IVM (0.3 mM) presented reduced toxicity to J774 macrophages and L929 fibroblasts compared to free IVM. Moreover, IVM-loaded nanocapsules also demonstrated enhanced in vitro anthelmintic activity against Strongyloides venezuelensis in comparison to free IVM. Collectively, the present findings demonstrate the promising potential of PCL-PSO nanocapsules to improve the antiparasitic effects exerted by IVM.

The protein disulfide isomerase inhibitor 3-methyltoxoflavin inhibits Chikungunya virus

Chikungunya virus (CHIKV) is the etiological agent of chikungunya fever, a (re)emerging arbovirus infection, that causes severe and often persistent arthritis, as well as representing a serious health concern worldwide for which no antivirals are currently available. Despite efforts over the last decade to identify and optimize new inhibitors or to reposition existing drugs, no compound has progressed to clinical trials for CHIKV and current prophylaxis is based on vector control, which has shown limited success in containing the virus. Our efforts to rectify this situation were initiated by screening 36 compounds using a replicon system and ultimately identified the natural product derivative 3-methyltoxoflavin with activity against CHIKV using a cell-based assay (EC50 200 nM, SI = 17 in Huh-7 cells). We have additionally screened 3-methyltoxoflavin against a panel of 17 viruses and showed that it only additionally demonstrated inhibition of the yellow fever virus (EC50 370 nM, SI = 3.2 in Huh-7 cells). We have also showed that 3-methyltoxoflavin has excellent in vitro human and mouse microsomal metabolic stability, good solubility and high Caco-2 permeability and it is not likely to be a P-glycoprotein substrate. In summary, we demonstrate that 3-methyltoxoflavin has activity against CHIKV, good in vitro absorption, distribution, metabolism and excretion (ADME) properties as well as good calculated physicochemical properties and may represent a valuable starting point for future optimization to develop inhibitors for this and other related viruses.

Cheminformatics-Based Study Identifies Potential Ebola VP40 Inhibitors

The Ebola virus (EBOV) is still highly infectious and causes severe hemorrhagic fevers in primates. However, there are no regulatorily approved drugs against the Ebola virus disease (EVD). The highly virulent and lethal nature of EVD highlights the need to develop therapeutic agents. Viral protein 40 kDa (VP40), the most abundantly expressed protein during infection, coordinates the assembly, budding, and release of viral particles into the host cell. It also regulates viral transcription and RNA replication. This study sought to identify small molecules that could potentially inhibit the VP40 protein by targeting the N-terminal domain using an in silico approach. The statistical quality of AutoDock Vina’s capacity to discriminate between inhibitors and decoys was determined, and an area under the curve of the receiver operating characteristic (AUC-ROC) curve of 0.791 was obtained. A total of 29,519 natural-product-derived compounds from Chinese and African sources as well as 2738 approved drugs were successfully screened against VP40. Using a threshold of −8 kcal/mol, a total of 7, 11, 163, and 30 compounds from the AfroDb, Northern African Natural Products Database (NANPDB), traditional Chinese medicine (TCM), and approved drugs libraries, respectively, were obtained after molecular docking. A biological activity prediction of the lead compounds suggested their potential antiviral properties. In addition, random-forest- and support-vector-machine-based algorithms predicted the compounds to be anti-Ebola with IC50 values in the micromolar range (less than 25 μM). A total of 42 natural-product-derived compounds were identified as potential EBOV inhibitors with desirable ADMET profiles, comprising 1, 2, and 39 compounds from NANPDB (2-hydroxyseneganolide), AfroDb (ZINC000034518176 and ZINC000095485942), and TCM, respectively. A total of 23 approved drugs, including doramectin, glecaprevir, velpatasvir, ledipasvir, avermectin B1, nafarelin acetate, danoprevir, eltrombopag, lanatoside C, and glycyrrhizin, among others, were also predicted to have potential anti-EBOV activity and can be further explored so that they may be repurposed for EVD treatment. Molecular dynamics simulations coupled with molecular mechanics Poisson–Boltzmann surface area calculations corroborated the stability and good binding affinities of the complexes (−46.97 to −118.9 kJ/mol). The potential lead compounds may have the potential to be developed as anti-EBOV drugs after experimental testing.

Novel Tetrahydroisoquinoline-Based Heterocyclic Compounds Efficiently Inhibit SARS-CoV-2 Infection In Vitro

The ongoing COVID-19 pandemic has caused over six million deaths and huge economic burdens worldwide. Antivirals against its causative agent, SARS-CoV-2, are in urgent demand. Previously, we reported that heterocylic compounds, i.e., chloroquine (CQ) and hydroxychloroquine (HCQ), are potent in inhibiting SARS-CoV-2 replication in vitro. In this study, we discussed the syntheses of two novel heterocylic compounds: tert-butyl rel-4-(((3R,4S)-3-(1H-indol-3-yl)-1-oxo-2-propyl-1,2,3,4-tetrahydroisoquinolin-4-yl)methyl)piperazine-1-carboxylate (trans-1) and rel-(3R,4S)-3-(1H-indol-3-yl)-4-(piperazin-1-ylmethyl)-2-propyl-3,4-dihydroisoquinolin-1(2H)-one (trans-2), which effectively suppressed authentic SARS-CoV-2 replication in Vero E6 cells. Compound trans-1 showed higher anti-SARS-CoV-2 activity than trans-2, with a half maximal effective concentration (EC₅₀) of 3.15 μM and a selective index (SI) exceeding 63.49, which demonstrated comparable potency to CQ or HCQ. Additional anti-SARS-CoV-2 tests on Calu-3 human lung cells showed that trans-1 efficiently inhibited viral replication (EC₅₀ = 2.78 μM; SI: > 71.94) and performed better than CQ (EC₅₀ = 44.90 μM; SI = 2.94). The time of an addition assay showed that the action mechanism of trans-1 differed from that of CQ, as it mainly inhibited the post-entry viral replication in both Vero E6 and Calu-3 cells. In addition, the differences between the antiviral mechanisms of these novel compounds and CQ were discussed.

Identification of Potential Antiviral Hops Compounds against Chikungunya Virus

Chikungunya virus (CHIKV) is an arthropod-borne virus that belongs to the genus Alphavirus (family Togaviridae). CHIKV causes chikungunya fever, which is mostly characterized by fever, arthralgia and, sometimes, a maculopapular rash. The bioactive constituents of hops (Humulus lupulus, Cannabaceae), mainly acylphloroglucinols, known as well as α- and β-acids, exerted distinct activity against CHIKV, without showing cytotoxicity. For fast and efficient isolation and identification of such bioactive constituents, a silica-free countercurrent separation method was applied. The antiviral activity was determined by plaque reduction test and was visually confirmed by a cell-based immunofluorescence assay. All hops compounds demonstrated a promising post-treatment viral inhibition, except the fraction of acylphloroglucinols, in mixture. β-acids fraction of 125 µg/mL expressed the strongest virucidal activity (EC50 = 15.21 µg/mL), in a drug-addition experiment on Vero cells. Hypothesis for mechanism of action were proposed for acylphloroglucinols based on their lipophilicity and chemical structure. Therefore, inhibition of some steps of the protein kinase C (PKC) transduction cascades was also discussed.

Growth in chikungunya virus-related research in ASEAN and South Asian countries from 1967 to 2022 following disease emergence: a bibliometric and graphical analysis

BACKGROUND

ASEAN (Association of Southeast Asian Nations) is composed of ten Southeast Asian countries bound by socio-cultural ties that promote regional peace and stability. South Asia, located in the southern subregion of Asia, includes nine countries sharing similarities in geographical and ethno-cultural factors. Chikungunya is one of the most significant problems in Southeast and South Asian countries. Much of the current chikungunya epidemic in Southeast Asia is caused by the emergence of a virus strain that originated in Africa and spread to Southeast Asia. Meanwhile, in South Asia, three confirmed lineages are in circulation. Given the positive correlation between research activity and the improvement of the clinical framework of biomedical research, this article aimed to examine the growth of chikungunya virus-related research in ASEAN and South Asian countries.

METHODS

The Scopus database was used for this bibliometric analysis. The retrieved publications were subjected to a number of analyses, including those for the most prolific countries, journals, authors, institutions, and articles. Co-occurrence mapping of terms and keywords was used to determine the current state, emerging topics, and future prospects of chikungunya virus-related research. Bibliometrix and VOSviewer were used to analyze the data and visualize the collaboration network mapping.

RESULTS

The Scopus search engine identified 1280 chikungunya-related documents published by ASEAN and South Asian countries between 1967 and 2022. According to our findings, India was the most productive country in South Asia, and Thailand was the most productive country in Southeast Asia. In the early stages of the study, researchers investigated the vectors and outbreaks of the chikungunya virus. In recent years, the development of antivirus agents has emerged as a prominent topic.

CONCLUSIONS

Our study is the first to present the growth of chikungunya virus-related research in ASEAN and South Asian countries from 1967 to 2022. In this study, the evaluation of the comprehensive profile of research on chikungunya can serve as a guide for future studies. In addition, a bibliometric analysis may serve as a resource for healthcare policymakers.

Alkaloids as potential antivirals. A comprehensive review

Alkaloids are a diverse group of natural phytochemicals. These phytochemicals in plants provide them protection against pests, and herbivorous organisms and also control their development. Numerous of these alkaloids have a variety of biological effects, and some have even been developed into medications with different medicinal properties. This review aims to provide a broad overview of the numerous naturally occurring alkaloids (isolated from both terrestrial and aquatic species) along with synthetically produced alkaloid compounds having prominent antiviral properties. Previous reviews on this subject have focused on the biological actions of both natural and synthetic alkaloids, but they have not gone into comprehensive detail about their antiviral properties. We reviewed here several antiviral alkaloids that have been described in the literature in different investigational environments i.e. (in-vivo, in-ovo, in-vitro, and in-silico), and found that these alkaloid compounds have significant antiviral properties against several infectious viruses. These alkaloids repressed and targeted various important stages of viral infection at non-toxic doses while some of the alkaloids reported here also exhibited comparable inhibitory activities to commercially used drugs. Overall, these anti-viral effects of alkaloids point to a high degree of specificity, implying that they could serve as effective and safe antiviral medicines if further pursued in medicinal and pharmacological investigations.

Chikungunya: An Emerging Public Health Concern

Purpose of Review

The worldwide spread of chikungunya over the past two decades calls for greater knowledge and awareness of the virus, its route of transmission, methods of diagnosis, and the use of available treatment and prevention measures.

Recent Findings

Chikungunya virus infection, an Aedes mosquito-borne febrile disease, has spread from Africa and Asia to Europe and the Americas and from the tropics and subtropics to temperate regions. International travel is a pivotal influence in the emergence of chikungunya as a global public health threat, as evidenced by a growing number of published reports on travel-related chikungunya infections. The striking features of chikungunya are arthralgia and arthritis, and the disease is often mistaken for dengue. Although mortality is low, morbidity can be profound and persistent. Current treatment for chikungunya is supportive; chikungunya vaccines and therapeutics are in development. Travelers planning to visit areas where the mosquito vectors are present should be advised on preventive measures.

Summary

Chikungunya is an emerging disease in the Americas. Frequent travel, the presence of at least two competent mosquito species, and a largely naïve human population in the Western Hemisphere create a setting conducive to future outbreaks. Awareness of the disease and its manifestations is critical to effectively and safely manage and limit its impact. Vaccines in late-stage clinical trials offer a new pathway to prevention.

Contemporary exploitation of natural products for arthropod-borne pathogen transmission-blocking interventions

An integrated approach to innovatively counter the transmission of various arthropod-borne diseases to humans would benefit from strategies that sustainably limit onward passage of infective life cycle stages of pathogens and parasites to the insect vectors and vice versa. Aiming to accelerate the impetus towards a disease-free world amid the challenges posed by climate change, discovery, mindful exploitation and integration of active natural products in design of pathogen transmission-blocking interventions is of high priority. Herein, we provide a review of natural compounds endowed with blockade potential against transmissible forms of human pathogens reported in the last 2 decades from 2000 to 2021. Finally, we propose various translational strategies that can exploit these pathogen transmission-blocking natural products into design of novel and sustainable disease control interventions. In summary, tapping these compounds will potentially aid in integrated combat mission to reduce disease transmission trends.

Anti-Alphaviral Alkaloids: Focus on Some Isoquinolines, Indoles and Quinolizidines

The discovery and the development of safe and efficient therapeutics against arthritogenic alphaviruses (e.g., chikungunya virus) remain a continuous challenge. Alkaloids are structurally diverse and naturally occurring compounds in plants, with a wide range of biological activities including beneficial effects against prominent pathogenic viruses and inflammation. In this short review, we discuss the effects of some alkaloids of three biologically relevant structural classes (isoquinolines, indoles and quinolizidines). Based on various experimental models (viral infections and chronic diseases), we highlight the immunomodulatory effects of these alkaloids. The data established the capacity of these alkaloids to interfere in host antiviral and inflammatory responses through key components (antiviral interferon response, ROS production, inflammatory signaling pathways and pro- and anti-inflammatory cytokines production) also involved in alphavirus infection and resulting inflammation. Thus, these data may provide a convincing perspective of research for the use of alkaloids as immunomodulators against arthritogenic alphavirus infection and induced inflammation.

The use of Ivermectin for the treatment of COVID-19: Panacea or enigma?

The outbreak of SARS-CoV-2 pandemic has triggered unprecedented social, economic and health challenges. To control and reduce the infection rate, countries employed non-pharmaceutical measures such as social distancing, isolation, quarantine, and the use of masks, hand and surface sanitisation. Since 2021 a global race for COVID-19 vaccination ensued, mainly due to a lack of equitable vaccine production and distribution. To date, no treatments have been demonstrated to cure COVID-19. The scientific World is now considering the potential use of Ivermectin as a prophylactic and treatment for COVID-19. Against this background, the objective of this study is to review the literature to demystify the enigma or panacea in the use of Ivermectin. This paper intends to investigate literature which supports the existence or shows the nonexistence of a causal link between Ivermectin, COVID-19 mortality and recovery. There are inconsistent results on the effectiveness of Ivermectin in the treatment of COVID-19 patients. Some studies have asserted that in a bid to slow down the transmission of COVID-19, ivermectin can be used to inhibit the in vitro replication of SARS-CoV-2. The pre-existing health system burdens can be alleviated as patients treated prophylactically would reduce hospital admissions and stem the spread of COVID-19. On a global scale, Ivermectin is currently used by about 28% of the world's population, and its adoption is presently about 44% of countries. However, the full administration of this drug would require further tests to establish its clinical effectiveness and efficacy.

High-Throughput Screening of FDA-Approved Drug Library Reveals Ixazomib Is a Broad-Spectrum Antiviral Agent against Arboviruses

The emergence of significant arboviruses and their spillover transmission to humans represent a major threat to global public health. No approved drugs are available for the treatment of significant arboviruses in circulation today. The repurposing of clinically approved drugs is one of the most rapid and promising strategies in the identification of effective treatments for diseases caused by arboviruses. Here, we screened small-molecule compounds with anti-tick-borne encephalitis virus, West Nile virus, yellow fever virus and chikungunya virus activity from 2580 FDA-approved drugs. In total, 60 compounds showed antiviral efficacy against all four of the arboviruses in Huh7 cells. Among these compounds, ixazomib and ixazomib citrate (inhibitors of 20S proteasome β5) exerted antiviral effects at a low-micromolar concentration. The time-of-drug-addition assay suggested that ixazomib and ixazomib citrate disturbed multiple processes in viruses’ life cycles. Furthermore, ixazomib and ixazomib citrate potently inhibited chikungunya virus replication and relieved virus-induced footpad swelling in a mouse model. These results offer critical information which supports the role of ixazomib as a broad-spectrum agent against arboviruses.

Characterization of the RNA-dependent RNA polymerase from Chikungunya virus and discovery of a novel ligand as a potential drug candidate

Chikungunya virus (CHIKV) is the causative agent of Chikungunya fever, an acute febrile and arthritogenic illness with no effective treatments available. The development of effective therapeutic strategies could be significantly accelerated with detailed knowledge of the molecular components behind CHIKV replication. However, drug discovery is hindered by our incomplete understanding of their main components. The RNA-dependent RNA-polymerase (nsP4-CHIKV) is considered the key enzyme of the CHIKV replication complex and a suitable target for antiviral therapy. Herein, the nsP4-CHIKV was extensively characterized through experimental and computational biophysical methods. In the search for new molecules against CHIKV, a compound designated LabMol-309 was identified as a strong ligand of the nsp4-CHIKV and mapped to bind to its active site. The antiviral activity of LabMol-309 was evaluated in cellular-based assays using a CHIKV replicon system and a reporter virus. In conclusion, this study highlights the biophysical features of nsP4-CHIKV and identifies a new compound as a promising antiviral agent against CHIKV infection.

The Antifungal Itraconazole Is a Potent Inhibitor of Chikungunya Virus Replication

Chikungunya virus (CHIKV) is the causative agent of chikungunya fever, a disabling disease that can cause long-term severe arthritis. Since the last large CHIKV outbreak in 2015, the reemergence of the virus represents a serious public health concern. The morbidity associated with viral infection emphasizes the need for the development of specific anti-CHIKV drugs. Herein, we describe the development and characterization of a CHIKV reporter replicon cell line and its use in replicon-based screenings. We tested 960 compounds from MMV/DNDi Open Box libraries and identified four candidates with interesting antiviral activities, which were confirmed in viral infection assays employing CHIKV-nanoluc and BHK-21 cells. The most noteworthy compound identified was itraconazole (ITZ), an orally available, safe, and cheap antifungal, that showed high selectivity indexes of >312 and >294 in both replicon-based and viral infection assays, respectively. The antiviral activity of this molecule has been described against positive-sense single stranded RNA viruses (+ssRNA) and was related to cholesterol metabolism that could affect the formation of the replication organelles. Although its precise mechanism of action against CHIKV still needs to be elucidated, our results demonstrate that ITZ is a potent inhibitor of the viral replication that could be repurposed as a broad-spectrum antiviral.

COVID-19 and The Promise of Small Molecule Therapeutics: Are There Lessons to be Learnt?

The coronavirus disease 2019 (COVID-19) pandemic had grounded the world to a standstill. As the disease continues to rage two years on, it is apparent that effective therapeutics are critical for a successful endemic living with COVID-19. A dearth in suitable antivirals has prompted researchers and healthcare professionals to investigate existing and developmental drugs against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although some of these drugs initially appeared to be promising for the treatment of COVID-19, they were ultimately found to be ineffective. In this review, we provide a retrospective analysis on the merits and limitations of some of these drugs that were tested against SARS-CoV-2 as well as those used for adjuvant therapy. While many of these drugs are no longer part of our arsenal for the treatment of COVID-19, important lessons can be learnt. The recent inclusion of molnupiravir and Paxlovid™ as treatment options for COVID-19 represent our best hope to date for endemic living with COVID-19. Our viewpoints on these two drugs and their prospects as current and future antiviral agents will also be provided.

Prospective mode of action of Ivermectin: SARS-CoV-2

The well-known anti-helminthic drug ivermectin (IVM) has been established as an example of drug repurposing for the management of SARS-CoV-2 infection. Various study has been done to understand the inhibitory mechanism of IVM against SARS-CoV-2 targets. Broadly, IVM has been categorized as a host-directed agent and the proposed mechanism involves inhibition of the IMPα/ß1-mediated nuclear import of viral proteins. In addition, in vitro/in vivo and molecular docking/dynamic simulation studies suggested multitargets mechanism of IVM against SARS-CoV-2. Present manuscript attempts to provide an overview of the detailed mechanism of action based on experimental and computational studies. The knowledge of binding interaction of IVM and SARS-CoV-2 targets will give the direction to developed new and potential anti-COVID agents.

Moxidectin and Ivermectin Inhibit SARS-CoV-2 Replication in Vero E6 Cells but Not in Human Primary Bronchial Epithelial Cells

Antiviral therapies are urgently needed to treat and limit the development of severe COVID-19 disease. Ivermectin, a broad-spectrum anti-parasitic agent, has been shown to have anti-SARS-CoV-2 activity in Vero cells at a concentration of 5 μM. These limited in vitro results triggered the investigation of ivermectin as a treatment option to alleviate COVID-19 disease. However, in April 2021, the World Health Organization stated the following: "The current evidence on the use of ivermectin to treat COVID-19 patients is inconclusive." It is speculated that the in vivo concentration of ivermectin is too low to exert a strong antiviral effect. Here, we performed a head-to-head comparison of the antiviral activity of ivermectin and the structurally related, but metabolically more stable moxidectin in multiple in vitro models of SARS-CoV-2 infection, including physiologically relevant human respiratory epithelial cells. Both moxidectin and ivermectin exhibited antiviral activity in Vero E6 cells. Subsequent experiments revealed that these compounds predominantly act on the steps following virus cell entry. Surprisingly, however, in human-airway-derived cell models, both moxidectin and ivermectin failed to inhibit SARS-CoV-2 infection, even at concentrations of 10 μM. These disappointing results call for a word of caution in the interpretation of anti-SARS-CoV-2 activity of drugs solely based on their activity in Vero cells. Altogether, these findings suggest that even using a high-dose regimen of ivermectin, or switching to another drug in the same class, is unlikely to be useful for treatment of SARS-CoV-2 in humans.

Inhibition of bovine and ovine capripoxviruses (Lumpy skin disease virus and Sheeppox virus) by ivermectin occurs at different stages of propagation in vitro

Capripoxvirus diseases are listed as reportable diseases by World Organization for Animal Health (OIE). Lumpy skin disease virus (LSDV) and sheeppox virus (SPPV), which can only be distinguished by molecular analysis, cause moderately, severe, or sometimes fatal infections in cattle and sheep. Even though vaccines are the most effective way to control the infection, their effectiveness may decrease in some cases. Therefore, it is significant to explore antiviral drugs against these diseases along with the vaccine. This study aimed to investigate the antiviral efficiency of ivermectin (IVM) at different stages of in vitro replication of LSDV and SPPV. For this purpose, viral titers (TCID₅₀/mL) of the viruses not treated with IVM (0.0 μM) and treated with non-cytotoxic concentrations of IVM (1.0 and 2.5 μM) were compared during a nine-day (216 h) post-infection period by viral titration assay. At 2.5 μM concentrations of IVM, the mean viral titer was significantly (P<0.05) reduced by approximately three logs for the replication stage of LSDV and SPPV. To evaluate the antiviral activity of IVM against LSDV and SPPV by treatment at the virus attachment and penetration stages, the titers of the virus either untreated or treated with 2,5 μM IVM were compared by virus titration assay. The number of infectious virions for LSDV and SPPV were decreased by 99.82% and 99.87% at the viral replication stage, 68.38% and 25.01% at the attachment stage, and 57.83% and 0.0% at the penetration stage, respectively. It was determined that ivermectin is statistically more effective on LSDV than SPPV at the virus attachment and penetration stages (P<0.05). This study found that the drug IVM can inhibit capripoxviruses, including LSDV and SPPV at various stages of the propagation. Moreover, this research predicted the in vitro antiviral ability of IVM against capripoxvirus infections for the first time.

Drug-based therapeutic strategies for COVID-19-infected patients and their challenges

Emerging epidemic-prone diseases have introduced numerous health and economic challenges in recent years. Given current knowledge of COVID-19, herd immunity through vaccines alone is unlikely. In addition, vaccination of the global population is an ongoing challenge. Besides, the questions regarding the prevalence and the timing of immunization are still under investigation. Therefore, medical treatment remains essential in the management of COVID-19. Herein, recent advances from beginning observations of COVID-19 outbreak to an understanding of the essential factors contributing to the spread and transmission of COVID-19 and its treatment are reviewed. Furthermore, an in-depth discussion on the epidemiological aspects, clinical symptoms and most efficient medical treatment strategies to mitigate the mortality and spread rates of COVID-19 is presented.

Treatment of SARS-CoV-2 (COVID-19): A safety perspective

The goal of this review is to report a balanced perspective of current evidence for efficacy of treatments for coronavirus disease 2019 (COVID-19) against the historical safety of these treatments as of May 2021. We preselected therapies of interest for COVID-19 based on national guidelines and modified over time. We searched PubMed and Medline for these specific COVID-19 treatments and data related to their efficacy. We also searched for prior randomized controlled trials of each therapy to assess adverse effects, and we obtained the Food and Drug Administration Approval label for this information. Several drugs have been approved for the treatment of COVID-19, and many more are under study. This includes dexamethasone, remdesivir, hydroxychloroquine/chloroquine, lopinvir/ritonavir, interferon or interleukin inhibitors, convalescent plasma and several vitamins and minerals. The strongest evidence for benefit is mortality benefit with dexamethasone in patients with COVID-19 and hypoxemia, although there is a signal of harm if this is started too early. There are several other promising therapies, like interleukin inhibitors and ivermectin. Hydroxychloroquine/chloroquine, lopinvir/ritonavir, and convalescent plasma do not have enough evidence of benefit to outweigh the known risks of these drugs.

Macrodomain Binding Compound MRS 2578 Inhibits Alphavirus Replication

Alphaviruses are positive-strand RNA viruses causing febrile disease. Macrodomain-containing proteins, involved in ADP-ribose-mediated signaling, are encoded by both host cells and several virus groups, including alphaviruses. In this study, compound MRS 2578 that targets the human ADP-ribose glycohydrolase MacroD1 inhibited Semliki Forest virus production as well as viral RNA replication and replicase protein expression. The inhibitor was similarly active in alphavirus trans-replication systems, indicating that it targets the viral RNA replication stage.

Tomatidine reduces Chikungunya virus progeny release by controlling viral protein expression

Tomatidine, a natural steroidal alkaloid from unripe green tomatoes has been shown to exhibit many health benefits. We recently provided in vitro evidence that tomatidine reduces the infectivity of Dengue virus (DENV) and Chikungunya virus (CHIKV), two medically important arthropod-borne human infections for which no treatment options are available. We observed a potent antiviral effect with EC50 values of 0.82 μM for DENV-2 and 1.3 μM for CHIKV-LR. In this study, we investigated how tomatidine controls CHIKV infectivity. Using mass spectrometry, we identified that tomatidine induces the expression of p62, CD98, metallothionein and thioredoxin-related transmembrane protein 2 in Huh7 cells. The hits p62 and CD98 were validated, yet subsequent analysis revealed that they are not responsible for the observed antiviral effect. In parallel, we sought to identify at which step of the virus replication cycle tomatidine controls virus infectivity. A strong antiviral effect was seen when in vitro transcribed CHIKV RNA was transfected into Huh7 cells treated with tomatidine, thereby excluding a role for tomatidine during CHIKV cell entry. Subsequent determination of the number of intracellular viral RNA copies and viral protein expression levels during natural infection revealed that tomatidine reduces the RNA copy number and viral protein expression levels in infected cells. Once cells are infected, tomatidine is not able to interfere with active RNA replication yet it can reduce viral protein expression. Collectively, the results delineate that tomatidine controls viral protein expression to exert its antiviral activity. Lastly, sequential passaging of CHIKV in presence of tomatidine did not lead to viral resistance. Collectively, these results further emphasize the potential of tomatidine as an antiviral treatment towards CHIKV infection.

Chikungunya fever is a debilitating disease caused by the mosquito-borne Chikungunya virus. Over the past two decades the geographical spread of the virus and its mosquito vector has drastically increased thereby causing millions of infections. To date there is no antiviral drug and no vaccine available to treat/prevent Chikungunya virus infection. We recently showed that the natural steroidal alkaloid tomatidine has potent antiviral activity towards Chikungunya virus at submicromolar concentrations. In this study we dissected how tomatidine reduces the production of Chikungunya virus particles. We show that tomatidine lowers viral protein expression and we hypothesize that the effect of tomatidine on viral protein translation hampers the production of progeny viral RNA copies / number of infected cells thereby leading to a reduced production of secreted virus particles. Also, we show that Chikungunya virus does not readily become resistant to tomatidine. Collectively, we deciphered the mechanism by which tomatidine exerts antiviral activity to Chikungunya virus and our results strengthen the potential of tomatidine as an antiviral treatment strategy towards Chikungunya virus.

Agent Clustering Strategy Based on Metabolic Flux Distribution and Transcriptome Expression for Novel Drug Development

The network module-based method has been used for drug repositioning. The traditional drug repositioning method only uses the gene characteristics of the drug but ignores the drug-triggered metabolic changes. The metabolic network systematically characterizes the connection between genes, proteins, and metabolic reactions. The differential metabolic flux distribution, as drug metabolism characteristics, was employed to cluster the agents with similar MoAs (mechanism of action). In this study, agents with the same pharmacology were clustered into one group, and a total of 1309 agents from the CMap database were clustered into 98 groups based on differential metabolic flux distribution. Transcription factor (TF) enrichment analysis revealed the agents in the same group (such as group 7 and group 26) were confirmed to have similar MoAs. Through this agent clustering strategy, the candidate drugs which can inhibit (Japanese encephalitis virus) JEV infection were identified. This study provides new insights into drug repositioning and their MoAs.

Plant Alkaloids Inhibit Membrane Fusion Mediated by Calcium and Fragments of MERS-CoV and SARS-CoV/SARS-CoV-2 Fusion Peptides

To rationalize the antiviral actions of plant alkaloids, the ability of 20 compounds to inhibit calcium-mediated fusion of lipid vesicles composed of phosphatidylglycerol and cholesterol was investigated using the calcein release assay and dynamic light scattering. Piperine, tabersonine, hordenine, lupinine, quinine, and 3-isobutyl-1-methylxanthine demonstrated the most potent effects (inhibition index greater than 50%). The introduction of phosphatidylcholine into the phosphatidylglycerol/cholesterol mixture led to significant changes in quinine, hordenine, and 3-isobutyl-1-methylxanthine efficiency. Comparison of the fusion inhibitory ability of the tested alkaloids, and the results of the measurements of alkaloid-induced alterations in the physical properties of model membranes indicated a potent relationship between a decrease in the cooperativity of the phase transition of lipids and the ability of alkaloids to prevent calcium-mediated vesicle fusion. In order to use this knowledge to combat the novel coronavirus pandemic, the ability of the most effective compounds to suppress membrane fusion induced by fragments of MERS-CoV and SARS-CoV/SARS-CoV-2 fusion peptides was studied using the calcein release assay and confocal fluorescence microscopy. Piperine was shown to inhibit vesicle fusion mediated by both coronavirus peptides. Moreover, piperine was shown to significantly reduce the titer of SARS-CoV2 progeny in vitro in Vero cells when used in non-toxic concentrations.

Effectiveness and safety of ivermectin in the treatment of COVID-19: protocol for a systematic review and meta-analysis

INTRODUCTION

Ivermectin is a drug with antiviral properties and has been proposed as an alternative treatment for patients with COVID-19, in some countries; however, there is limited evidence to support its clinical use. Accordingly, the aim of this review and meta-analysis is to obtain superior evidence on the effectiveness and safety of ivermectin in treatment of COVID-19.

METHODS AND ANALYSIS

We will search in the medical databases and International Clinical Trials Registry Platform databases for randomised clinical trials and quasi-randomised trials published from December 2019. The criteria for inclusion are that infection needs to be confirmed by a real-time PCR or serology test, and the effect of ivermectin has been compared with placebo, symptomatic treatment or no treatment. We will exclude observational studies and clinical trials that involved patients with symptoms suggestive of COVID-19, but without a laboratorial diagnosis. Outcomes of interest include mortality, time to symptom resolution, time of hospitalisation, frequency of invasive mechanical ventilation and extracorporeal membrane oxygenation, incidence of severe acute respiratory syndrome, admission to intensive care unit, viral load, PCR-negative status, percentage of infection after prophylactic use, and total incidence of adverse and side effects. Study selection will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Two reviewers will independently select the studies and assess their eligibility. Two other reviewers will independently extract data from each study. Meta-analysis will then be carried out using fixed-effects or random-effects model, using the mean difference for continuous outcomes and the relative risk for dichotomous outcomes. Bias risk will be assessed using the Cochrane risk-of-bias tool. The quality of evidence for each outcome will be assessed using GRADE (Grading of Recommendations Assessment, Development and Evaluation) methodology. Review Manager V.5.3.5 will be used for synthesis and subgroup analysis.

ETHICS AND DISSEMINATION

Owing to the nature of the review, ethical approval is not required. The results will be disseminated through peer-reviewed publications.

PROSPERO REGISTRATION NUMBER

CRD42020197395.

Berberine Inhibits Dengue Virus through Dual Mechanisms

Mosquito transmitted viruses, particularly those of the genus Flavivirus, are a significant healthcare burden worldwide, especially in tropical and sub-tropical areas. However, effective medicines for these viral infections remains lacking. Berberine (BBR) is an alkaloid found in some plants used in traditional medicines in Southeast Asia and elsewhere, and BBR has been shown to possess anti-viral activities. During a screen for potential application to mosquito transmitted viruses, BBR was shown to have virucidal activity against dengue virus (DENV; IC₅₀ 42.87 µM) as well as against Zika virus (IC₅₀ 11.42 µM) and chikungunya virus (IC₅₀ 14.21 µM). BBR was shown to have cellular effects that lead to an increase in cellular DENV E protein without a concomitant effect on DENV nonstructural proteins, suggesting an effect on viral particle formation or egress. While BBR was shown to have an effect of ERK1/2 activation this did not result in defects in viral egress mechanisms. The primary effect of BBR on viral production was likely to be through BBR acting through AMPK activation and disruption of lipid metabolism. Combined these results suggest that BBR has a dual effect on DENV infection, and BBR may have the potential for development as an anti-DENV antiviral.

Natural-Product-Based Solutions for Tropical Infectious Diseases

About half of the world's population and 80% of the world's biodiversity can be found in the tropics. Many diseases are specific to the tropics, with at least 41 diseases caused by endemic bacteria, viruses, parasites, and fungi. Such diseases are of increasing concern, as the geographic range of tropical diseases is expanding due to climate change, urbanization, change in agricultural practices, deforestation, and loss of biodiversity. While traditional medicines have been used for centuries in the treatment of tropical diseases, the active natural compounds within these medicines remain largely unknown. In this review, we describe infectious diseases specific to the tropics, including their causative pathogens, modes of transmission, recent major outbreaks, and geographic locations. We further review current treatments for these tropical diseases, carefully consider the biodiscovery potential of the tropical biome, and discuss a range of technologies being used for drug development from natural resources. We provide a list of natural products with antimicrobial activity, detailing the source organisms and their effectiveness as treatment. We discuss how technological advancements, such as next-generation sequencing, are driving high-throughput natural product screening pipelines to identify compounds with therapeutic properties. This review demonstrates the impact natural products from the vast tropical biome have in the treatment of tropical infectious diseases and how high-throughput technical capacity will accelerate this discovery process.

A Water-Soluble Antibiotic in Rhubarb Stalk Shows an Unusual Pattern of Multiple Zones of Inhibition and Preferentially Kills Slow-Growing Bacteria

Organic extract of Rhubarb (Rheum officinale) roots is known to have several medicinal uses. However, not much research has been done with the rhubarb stalk. The aim of this research is to evaluate the anti-bacterial and anti-proliferative effects of the aqueous extract from rhubarb stalks. The crude aqueous extract was further purified using anion exchange and gel filtration. The purified compound demonstrated broad spectrum antibacterial activity against the Gram-negative bacteria, E. coli and Aggregatibacter actinomycetemcomitans, and Gram-positive bacteria, S. aureus. A time-kill assay demonstrated that the antibiotic has strong bactericidal activity. It also has anti-proliferative action against the breast cancer cell line MCF-7 with no cytotoxicity, although the crude extract had a significant cytotoxic effect. The antibiotic activity, as measured by the diameter of the zone of inhibition, increased by several fold in low nutrient and/or low salt agar, suggesting that the antibiotic preferentially kills slow-growing bacteria. The antibiotic also gives an unusual pattern of multiple zones of inhibition in which several zones of cell growth are seen within the zone of inhibition. In conclusion, the active component in the aqueous extract of rhubarb stalk has great potential as a strong bactericidal antibiotic and as an anti-proliferative drug.

A secondary approach with conventional medicines and supplements to recuperate current COVID-19 status

Novel coronavirus 2019 (COVID-19) is a zoonosis that revised the global economic and societal progress since early 2020. The SARS-CoV-2 has been recognized as the responsible pathogen for COVID-19 with high infection and mortality rate potential. It has spread in 192 countries and infected about 1.5% of the world population, and still, a proper therapeutic approach is not unveiled. COVID-19 indication starts with fever to shortness of breathing, leading to ICU admission with the ventilation support in severe conditions. Besides the symptomatic mainstay clinical therapeutic approach, only Remdesivir has been approved by the FDA. Several pharmaceutical companies claimed different vaccines with exceptionally high efficacy (90–95%) against COVID-19; how long these vaccines can protect and long-term safety with the new variants are unpredictable. After the worldwide spread of the COVID-19 pandemic, numerous clinical trials with different phases are being performed to find the most appropriate solution to this condition. Some of these trials with old FDA-approved drugs showed promising results. In this review, we have precisely compiled the efforts to curb the disease and discussed the clinical findings of Ivermectin, Doxycycline, Vitamin-D, Vitamin-C, Zinc, and cannabidiol and their combinations. Additionally, the correlation of these molecules on the prophylactic and diseased ministration against COVID-19 has been explored.

Antivirals against the Chikungunya Virus

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that has re-emerged in recent decades, causing large-scale epidemics in many parts of the world. CHIKV infection leads to a febrile disease known as chikungunya fever (CHIKF), which is characterised by severe joint pain and myalgia. As many patients develop a painful chronic stage and neither antiviral drugs nor vaccines are available, the development of a potent CHIKV inhibiting drug is crucial for CHIKF treatment. A comprehensive summary of current antiviral research and development of small-molecule inhibitor against CHIKV is presented in this review. We highlight different approaches used for the identification of such compounds and further discuss the identification and application of promising viral and host targets.

Potential Prophylactic Treatments for COVID-19

The World Health Organization declared the SARS-CoV-2 outbreak a Public Health Emergency of International Concern at the end of January 2020 and a pandemic two months later. The virus primarily spreads between humans via respiratory droplets, and is the causative agent of Coronavirus Disease 2019 (COVID-19), which can vary in severity, from asymptomatic or mild disease (the vast majority of the cases) to respiratory failure, multi-organ failure, and death. Recently, several vaccines were approved for emergency use against SARS-CoV-2. However, their worldwide availability is acutely limited, and therefore, SARS-CoV-2 is still expected to cause significant morbidity and mortality in the upcoming year. Hence, additional countermeasures are needed, particularly pharmaceutical drugs that are widely accessible, safe, scalable, and affordable. In this comprehensive review, we target the prophylactic arena, focusing on small-molecule candidates. In order to consolidate a potential list of such medications, which were categorized as either antivirals, repurposed drugs, or miscellaneous, a thorough screening for relevant clinical trials was conducted. A brief molecular and/or clinical background is provided for each potential drug, rationalizing its prophylactic use as an antiviral or inflammatory modulator. Drug safety profiles are discussed, and current medical indications and research status regarding their relevance to COVID-19 are shortly reviewed. In the near future, a significant body of information regarding the effectiveness of drugs being clinically studied for COVID-19 is expected to accumulate, in addition to information regarding the efficacy of prophylactic treatments.

Crosstalk between nucleocytoplasmic trafficking and the innate immune response to viral infection

The nuclear pore complex is the sole gateway connecting the nucleoplasm and cytoplasm. In humans, the nuclear pore complex is one of the largest multiprotein assemblies in the cell, with a molecular mass of ∼110 MDa and consisting of 8 to 64 copies of about 34 different nuclear pore proteins, termed nucleoporins, for a total of 1000 subunits per pore. Trafficking events across the nuclear pore are mediated by nuclear transport receptors and are highly regulated. The nuclear pore complex is also used by several RNA viruses and almost all DNA viruses to access the host cell nucleoplasm for replication. Viruses hijack the nuclear pore complex, and nuclear transport receptors, to access the nucleoplasm where they replicate. In addition, the nuclear pore complex is used by the cell innate immune system, a network of signal transduction pathways that coordinates the first response to foreign invaders, including viruses and other pathogens. Several branches of this response depend on dynamic signaling events that involve the nuclear translocation of downstream signal transducers. Mounting evidence has shown that these signaling cascades, especially those steps that involve nucleocytoplasmic trafficking events, are targeted by viruses so that they can evade the innate immune system. This review summarizes how nuclear pore proteins and nuclear transport receptors contribute to the innate immune response and highlights how viruses manipulate this cellular machinery to favor infection. A comprehensive understanding of nuclear pore proteins in antiviral innate immunity will likely contribute to the development of new antiviral therapeutic strategies.

Berberine: A Promising Natural Isoquinoline Alkaloid for the Development of Hypolipidemic Drugs

Berberine, as a representative isoquinoline alkaloid, exhibits significant hypolipidemic activity in both animal models and clinical trials. Recently, a large number of studies on the lipid-lowering mechanism of berberine and studies for improving its hypolipidemic activity have been reported, but for the most part, they have been either incomplete or not comprehensive. In addition, there have been a few specific reviews on the lipid-reducing effect of berberine. In this paper, the physicochemical properties, the lipid-lowering mechanism, and studies of the modification of berberine all are discussed to promote the development of berberine as a lipid-lowering agent. Subsequently, this paper provides some insights into the deficiencies of berberine in the study of lipid-lowering drug, and based on the situation, some proposals are put forward.

Drug Repurposing: A Strategy for Discovering Inhibitors against Emerging Viral Infections

BACKGROUND

Viral diseases are responsible for several deaths around the world. Over the past few years, the world has seen several outbreaks caused by viral diseases that, for a long time, seemed to possess no risk. These are diseases that have been forgotten for a long time and, until nowadays, there are no approved drugs or vaccines, leading the pharmaceutical industry and several research groups to run out of time in the search for new pharmacological treatments or prevention methods. In this context, drug repurposing proves to be a fast and economically viable technique, considering the fact that it uses drugs that have a well-established safety profile. Thus, in this review, we present the main advances in drug repurposing and their benefit for searching new treatments against emerging viral diseases.

METHODS

We conducted a search in the bibliographic databases (Science Direct, Bentham Science, PubMed, Springer, ACS Publisher, Wiley, and NIH's COVID-19 Portfolio) using the keywords "drug repurposing", "emerging viral infections" and each of the diseases reported here (CoV; ZIKV; DENV; CHIKV; EBOV and MARV) as an inclusion/exclusion criterion. A subjective analysis was performed regarding the quality of the works for inclusion in this manuscript. Thus, the selected works were those that presented drugs repositioned against the emerging viral diseases presented here by means of computational, high-throughput screening or phenotype-based strategies, with no time limit and of relevant scientific value.

RESULTS

291 papers were selected, 24 of which were CHIKV; 52 for ZIKV; 43 for DENV; 35 for EBOV; 10 for MARV; and 56 for CoV and the rest (72 papers) related to the drugs repurposing and emerging viral diseases. Among CoV-related articles, most were published in 2020 (31 papers), updating the current topic. Besides, between the years 2003 - 2005, 10 articles were created, and from 2011 - 2015, there were 7 articles, portraying the outbreaks that occurred at that time. For ZIKV, similar to CoV, most publications were during the period of outbreaks between the years 2016 - 2017 (23 articles). Similarly, most CHIKV (13 papers) and DENV (14 papers) publications occur at the same time interval. For EBOV (13 papers) and MARV (4 papers), they were between the years 2015 - 2016. Through this review, several drugs were highlighted that can be evolved in vivo and clinical trials as possible used against these pathogens showed that remdesivir represent potential treatments against CoV. Furthermore, ribavirin may also be a potential treatment against CHIKV; sofosbuvir against ZIKV; celgosivir against DENV, and favipiravir against EBOV and MARV, representing new hopes against these pathogens.

CONCLUSION

The conclusions of this review manuscript show the potential of the drug repurposing strategy in the discovery of new pharmaceutical products, as from this approach, drugs could be used against emerging viral diseases. Thus, this strategy deserves more attention among research groups and is a promising approach to the discovery of new drugs against emerging viral diseases and also other diseases.

Potential Drugs for the Treatment of COVID-19: Synthesis, Brief History and Application

Coronaviruses (CoVs) belonging to the Betacoronavirus group, an unusually large RNA genome, are characterized by club-like spikes that project from their surface. An outbreak of a novel coronavirus 2019 (nCOVID-19) showing a unique replication strategy and infection has posed a significant threat to international health and the economy around the globe. Scientists around the world are investigating few previously used clinical drugs for the treatment of COVID-19. This review provides synthesis and mode of action of recently investigated drugs like Chloroquine, Hydroxychloroquine, Ivermectin, Selamectin, Remdesivir, Baricitinib, Darunavir, Favipiravir, Lopinavir/ritonavir and Mefloquine hydrochloride that constitute an option for COVID-19 treatment.

How SARS-CoV-2 and Other Viruses Build an Invasion Route to Hijack the Host Nucleocytoplasmic Trafficking System

The host nucleocytoplasmic trafficking system is often hijacked by viruses to accomplish their replication and to suppress the host immune response. Viruses encode many factors that interact with the host nuclear transport receptors (NTRs) and the nucleoporins of the nuclear pore complex (NPC) to access the host nucleus. In this review, we discuss the viral factors and the host factors involved in the nuclear import and export of viral components. As nucleocytoplasmic shuttling is vital for the replication of many viruses, we also review several drugs that target the host nuclear transport machinery and discuss their feasibility for use in antiviral treatment.

Drug repurposing approach to combating coronavirus: Potential drugs and drug targets

In the past two decades, three highly pathogenic human coronaviruses severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus, and, recently, SARS-CoV-2, have caused pandemics of severe acute respiratory diseases with alarming morbidity and mortality. Due to the lack of specific anti-CoV therapies, the ongoing pandemic of coronavirus disease 2019 (COVID-19) poses a great challenge to clinical management and highlights an urgent need for effective interventions. Drug repurposing is a rapid and feasible strategy to identify effective drugs for combating this deadly infection. In this review, we summarize the therapeutic CoV targets, focus on the existing small molecule drugs that have the potential to be repurposed for existing and emerging CoV infections of the future, and discuss the clinical progress of developing small molecule drugs for COVID-19.

Review of the Emerging Evidence Demonstrating the Efficacy of Ivermectin in the Prophylaxis and Treatment of COVID-19

BACKGROUND

After COVID-19 emerged on U.S shores, providers began reviewing the emerging basic science, translational, and clinical data to identify potentially effective treatment options. In addition, a multitude of both novel and repurposed therapeutic agents were used empirically and studied within clinical trials.

AREAS OF UNCERTAINTY

The majority of trialed agents have failed to provide reproducible, definitive proof of efficacy in reducing the mortality of COVID-19 with the exception of corticosteroids in moderate to severe disease. Recently, evidence has emerged that the oral antiparasitic agent ivermectin exhibits numerous antiviral and anti-inflammatory mechanisms with trial results reporting significant outcome benefits. Given some have not passed peer review, several expert groups including Unitaid/World Health Organization have undertaken a systematic global effort to contact all active trial investigators to rapidly gather the data needed to grade and perform meta-analyses.

DATA SOURCES

Data were sourced from published peer-reviewed studies, manuscripts posted to preprint servers, expert meta-analyses, and numerous epidemiological analyses of regions with ivermectin distribution campaigns.

THERAPEUTIC ADVANCES

A large majority of randomized and observational controlled trials of ivermectin are reporting repeated, large magnitude improvements in clinical outcomes. Numerous prophylaxis trials demonstrate that regular ivermectin use leads to large reductions in transmission. Multiple, large "natural experiments" occurred in regions that initiated "ivermectin distribution" campaigns followed by tight, reproducible, temporally associated decreases in case counts and case fatality rates compared with nearby regions without such campaigns.

CONCLUSIONS

Meta-analyses based on 18 randomized controlled treatment trials of ivermectin in COVID-19 have found large, statistically significant reductions in mortality, time to clinical recovery, and time to viral clearance. Furthermore, results from numerous controlled prophylaxis trials report significantly reduced risks of contracting COVID-19 with the regular use of ivermectin. Finally, the many examples of ivermectin distribution campaigns leading to rapid population-wide decreases in morbidity and mortality indicate that an oral agent effective in all phases of COVID-19 has been identified.

Phytochemicals from Plant Foods as Potential Source of Antiviral Agents: An Overview

To date, the leading causes of mortality and morbidity worldwide include viral infections, such as Ebola, influenza virus, acquired immunodeficiency syndrome (AIDS), severe acute respiratory syndrome (SARS) and recently COVID-19 disease, caused by the SARS-CoV-2 virus. Currently, we can count on a narrow range of antiviral drugs, especially older generation ones like ribavirin and interferon which are effective against viruses in vitro but can often be ineffective in patients. In addition to these, we have antiviral agents for the treatment of herpes virus, influenza virus, HIV and hepatitis virus. Recently, drugs used in the past especially against ebolavirus, such as remdesivir and favipiravir, have been considered for the treatment of COVID-19 disease. However, even if these drugs represent important tools against viral diseases, they are certainly not sufficient to defend us from the multitude of viruses present in the environment. This represents a huge problem, especially considering the unprecedented global threat due to the advancement of COVID-19, which represents a potential risk to the health and life of millions of people. The demand, therefore, for new and effective antiviral drugs is very high. This review focuses on three fundamental points: (1) presents the main threats to human health, reviewing the most widespread viral diseases in the world, thus describing the scenario caused by the disease in question each time and evaluating the specific therapeutic remedies currently available. (2) It comprehensively describes main phytochemical classes, in particular from plant foods, with proven antiviral activities, the viruses potentially treated with the described phytochemicals. (3) Consideration of the various applications of drug delivery systems in order to improve the bioavailability of these compounds or extracts. A PRISMA flow diagram was used for the inclusion of the works. Taking into consideration the recent dramatic events caused by COVID-19 pandemic, the cry of alarm that denounces critical need for new antiviral drugs is extremely strong. For these reasons, a continuous systematic exploration of plant foods and their phytochemicals is necessary for the development of new antiviral agents capable of saving lives and improving their well-being.

Progress of Plant Medicine Derived Extracts and Alkaloids on Modulating Viral Infections and Inflammation

Viral infectious diseases are serious threats to human health in both developing and developed countries. Although there is the continued development of new drugs from synthetic sources as antiviral agents, medicinal plants continue to provide the basic raw materials for some of the most important antiviral drugs. Alkaloids are a class of pharmacologically active plant compounds that are usually alkaline in nature. In this review, we tried to summarize recent progress in herb-based antiviral research, the advantages of using active plant compounds as antiviral agents, and the inflammatory responses initiated by alkaloids, based on the literature from 2009 to 2019, for the treatment of conditions, including influenza, human immunodeficiency virus, herpes simplex virus, hepatitis, and coxsackievirus infections. Articles are retrieved from PubMed, Google Scholar, and Web of Science using relevant keywords. In particular, the alkaloids from medicinal plants responsible for the molecular mechanisms of anti-inflammatory actions are identified and discussed. This review can provide a theoretical basis and approaches for using various alkaloids as antiviral treatments. More research is needed to develop alkaloidal compounds as antiviral therapeutic agents and potential regulators of the anti-inflammatory response.

Bacterial natural products in the fight against mosquito-transmitted tropical diseases

Covering: up to 2019 Secondary metabolites of microbial origin have long been acknowledged as medically relevant, but their full potential remains largely unexploited. Of the countless natural compounds discovered thus far, only 5-10% have been isolated from microorganisms. At the same time, while whole-genome sequencing has demonstrated that bacteria and fungi often encode natural products, only a few genera have yet been mined for new compounds. This review explores the contributions of bacterial natural products to combatting infection by malaria parasites, filarial worms, and arboviruses such as dengue, Zika, Chikungunya, and West Nile. It highlights how molecules isolated from microorganisms ranging from marine cyanobacteria to mosquito endosymbionts can be exploited as antimicrobials and antivirals. Pursuit of this mostly untapped source of chemical entities will potentially result in new interventions against these tropical diseases, which are urgently needed to combat the increase in the incidence of resistance.