Exploring bioflavonoids as novel antivirals against Chikungunya virus / Rafidah Lani

Chikungunya virus (CHIKV) is a mosquito-borne virus that recently has been classified as a Category C pathogen by National Institute of Allergy and Infectious Diseases (NIAID). This alphavirus causes several clinical features similar to dengue virus infection, except polyarthritis and tenosynovitis, where the similarities would usually cause misdiagnosis. CHIKV has caused many large outbreaks all over sub-Sahara Africa and tropical Asia including India and the Western Pacific. This could possibly turn into an emerging global pandemic if no effective preventive measures are taken. Since CHIKV spreads by increased global travels, immunologically naive populations such as in the United States (US) is at risk, since it is one of the non-endemic regions. Besides the US recently, there have been travel-associated CHIKV cases in Australia, Asia and European countries as well. The challenge posed by CHIKV is there is no vaccine and antiviral treatment currently available for CHIKV infection. CHIKV infection is treated symptomatically by the administration of non-steroidal anti-inflammatory drugs or steroids, bed rest and fluids. In worst case scenarios, such as debilitating chronic CHIKV infection, corticosteroids is the only option. Available treatments such as chloroquine can only inhibit CHIKV cell-to-cell spread but not the replication of the infected cells. Research on vaccines and antivirals are still actively pursued to produce safer vaccines with longer protective effects and persistent antibodies. Live vaccines were produced, but with side effects including risks of producing chronic rheumatism. Most antiviral drugs that have been suggested are nucleoside analogues where they are potentially teratogenic, embryotoxic, carcinogenic and possess anti-proliferative activities. iv Turning to organic sources may prove to be more beneficial in the search for anti-CHIKV compounds, such as natural bioflavonoids which can be derived from most herbal medicines and ordinary fruits. Bioflavonoids are phenolic compounds that possess anti-oxidant, anti-tumor, anti-proliferative, anti-inflammatory, antibacterial and antiviral activities. Thus, in this study, the main objective is to find non-toxic bioflavonoid compounds that could inhibit the CHIKV infection or at least reduce the CHIKV replication at in vitro level. In order to meet the objectives of this study, various antiviral assays were performed including the CHIKV replicon cell line-based assay, immunofluorescence assay and western blotting analyses. The replication efficiency of CHIKV at each antiviral assay was determined by using the qRT-PCR assay with RNA copy number as the parameter. Statistical analysis was performed by using the Graph Pad Prism 5 software with suitable statistical analysis for each assay. Through this study, 4 out of 14 bioflavonoid compounds were identified to exhibit intracellular antiviral activity against CHIKV at different stages of CHIKV life cycle. These compounds are baicalein, fisetin, quercetagetin and silymarin. These compounds were also able to suppress the accumulation of important CHIKV proteins such as pE2, E2, nsP1 and nsP3 proteins in addition to the ability to interfere with CHIKV replication cycle. This study is the first step towards finding a potent anti-CHIKV compound

Knowledge of SARS-CoV-2 Epitopes and Population HLA Types Is Important in the Design of COVID-19 Vaccines

The COVID-19 pandemic has caused extensive loss of lives and economic hardship. In response, infectious disease experts and vaccine developers promptly responded by bringing forth candidate vaccines, some of which have been listed in the World Health Organization’s Emergency Use Listing. Notwithstanding the diverse worldwide population genetics, the vaccines thus far developed are generic in nature for use worldwide. Differences in the human leukocyte antigen (HLA) in different populations, variation of the T cell epitopes, and the propensity of SARS-CoV-2 genetic mutations left room for improvement of the vaccines. Here, we discussed the implications of COVID-19 vaccination and SARS-CoV-2 infection by taking into consideration SARS-CoV-2 mutations, T cell epitopes, risk factors, and current platforms of candidate vaccines based on the HLA types that are commonly present in Peninsular Malaysia Chinese, Indian, and Malay populations. The HLA types associated with protection against and susceptibility to severe SARS-CoV-2 infection were identified based on reported case-control and cohort studies. The relevance of including the non-spike SARS-CoV-2 proteins in the future COVID-19 vaccines is also highlighted. This review is meant to trigger researchers to acknowledge the importance of investigating the possible relationships between the HLA haplotype and the SARS-CoV-2 strains circulating in different populations

Fisetin Modulates Toll-like Receptor-Mediated Innate Antiviral Response in Chikungunya Virus-Infected Hepatocellular Carcinoma Huh7 Cells

In the chronic phase of chikungunya virus (CHIKV) infection, excessive inflammation manifests as incapacitating joint pain and prolonged arthritis. Arthritis resulted from a large influx of infiltrating immune cells driven by pro-inflammatory cytokines and chemokines originating from the toll-like receptor (TLR)-mediated innate antiviral response. This study investigated fisetin’s ability to modulate TLR-mediated antiviral responses against CHIKV in Huh7 cells. The CHIKV inhibitory potential of fisetin was assessed by plaque-forming unit assay, virus yield reduction assay, and bright-field microscopy (cytopathic effect, immunofluorescence). Fisetin’s modulatory potential on TLR-mediated antiviral response was evaluated by immunofluorescence assay (expression of TLR proteins), qRT-PCR (mRNA level of antiviral genes), human cytokine array, and the immunoblotting of key transcription factors. The present study showed fisetin induced the expression of the antiviral genes at an early time-point by promoting the phosphorylation of IRF3 and IRF7. Fisetin reduced excessive inflammatory cytokine responses in CHIKV-infected Huh7 cells by impeding the over-phosphorylation of NF-κB. Fisetin also reduced CHIKV-induced cytopathic effects in CHIKV-infected Huh7 cells. Altogether, our study suggests that fisetin modulates TLR-mediated antiviral responses by affecting the CHIKV-induced inflammatory responses

Fisetin Modulates Toll-like Receptor-Mediated Innate Antiviral Response in Chikungunya Virus-Infected Hepatocellular Carcinoma Huh7 Cells

In the chronic phase of chikungunya virus (CHIKV) infection, excessive inflammation manifests as incapacitating joint pain and prolonged arthritis. Arthritis resulted from a large influx of infiltrating immune cells driven by pro-inflammatory cytokines and chemokines originating from the toll-like receptor (TLR)-mediated innate antiviral response. This study investigated fisetin’s ability to modulate TLR-mediated antiviral responses against CHIKV in Huh7 cells. The CHIKV inhibitory potential of fisetin was assessed by plaque-forming unit assay, virus yield reduction assay, and bright-field microscopy (cytopathic effect, immunofluorescence). Fisetin’s modulatory potential on TLR-mediated antiviral response was evaluated by immunofluorescence assay (expression of TLR proteins), qRT-PCR (mRNA level of antiviral genes), human cytokine array, and the immunoblotting of key transcription factors. The present study showed fisetin induced the expression of the antiviral genes at an early time-point by promoting the phosphorylation of IRF3 and IRF7. Fisetin reduced excessive inflammatory cytokine responses in CHIKV-infected Huh7 cells by impeding the over-phosphorylation of NF-κB. Fisetin also reduced CHIKV-induced cytopathic effects in CHIKV-infected Huh7 cells. Altogether, our study suggests that fisetin modulates TLR-mediated antiviral responses by affecting the CHIKV-induced inflammatory responses

From defense to offense: Modulating toll-like receptors to combat arbovirus infections

ABSTRACTArboviruses are a significant threat to global public health, with outbreaks occurring worldwide. Toll-like receptors (TLRs) play a crucial role in the innate immune response against these viruses by recognizing pathogen-associated molecular patterns and initiating an inflammatory response. Significantly, TLRs commonly implicated in the immune response against viral infections include TLR2, TLR4, TLR6, TLR3, TLR7, and TLR8; limiting or allowing them to replicate and spread within the host. Modulating TLRs has emerged as a promising approach to combat arbovirus infections. This review summarizes recent advances in TLR modulation as a therapeutic target in arbovirus infections. Studies have shown that the activation of TLRs can enhance the immune response against arbovirus infections, leading to increased viral clearance and protection against disease. Conversely, inhibition of TLRs can reduce the excessive inflammation and tissue damage associated with arbovirus infection. Modulating TLRs represents a potential therapeutic strategy to combat arbovirus infections

COVID-19 therapeutic potential of natural products

Despite the fact that coronavirus disease 2019 (COVID-19) treatment and management are now considerably regulated, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is still one of the leading causes of death in 2022. The availability of COVID-19 vaccines, FDA-approved antivirals, and monoclonal antibodies in low-income countries still poses an issue to be addressed. Natural products, particularly traditional Chinese medicines (TCMs) and medicinal plant extracts (or their active component), have challenged the dominance of drug repurposing and synthetic compound libraries in COVID-19 therapeutics. Their abundant resources and excellent antiviral performance make natural products a relatively cheap and readily available alternative for COVID-19 therapeutics. Here, we deliberately review the anti-SARS-CoV-2 mechanisms of the natural products, their potency (pharmacological profiles), and application strategies for COVID-19 intervention. In light of their advantages, this review is intended to acknowledge the potential of natural products as COVID-19 therapeutic candidates

Flavone Enhances Dengue Virus Type-2 (NGC Strain) Infectivity and Replication in Vero Cells

This study investigates the effects of 2-phenyl-1-benzopyran-4-one (flavone) on DENV-2 infectivity in Vero cells. Virus adsorption and attachment and intracellular virus replication were investigated using a foci forming unit assay (FFUA) and quantitative RT-PCR, respectively. Addition of flavone (100 μg/mL) significantly increased the number of DENV-2 foci by 35.66% ± 1.52 and 49.66% ± 2.51 when added during and after virus adsorption to the Vero cells, respectively. The average foci size after 4 days of infection increased by 33% ± 2.11 and 89% ± 2.13. The DENV-2 specific RNA copy number in the flavone-treated infected cells increased by 6.41- and 23.1-fold when compared to the mock-treated infected cells. Flavone (100 μg/mL) did not promote or inhibit Vero cell proliferation. The CC50 value of flavone against Vero cells was 446 µg/mL. These results suggest that flavone might enhance dengue virus replication by acting antagonistically towards flavonoids known to inhibit dengue virus replication