Interference in dengue virus adsorption and uncoating by carrageenans

C1q modulation of antibody-dependent enhancement of dengue virus infection in human myeloid cell lines is dependent on cell type and antibody specificity

Antibody-dependent enhancement (ADE) of dengue virus (DENV) infection is one of the mechanisms contributing to increased severity during heterotypic, secondary infection. The complement protein C1q has been shown to reduce the magnitude of ADE in vitro. Therefore, we investigated the mechanisms of C1q modulation of ADE, focusing on processes of viral entry. Using a model of ADE of DENV-1 infection in human myeloid cell lines in the presence of monoclonal antibodies, 4G2 and 2H2, we found that C1q produced nearly a 40-fold reduction of ADE of DENV-1 in K562 cells, but had no effect in U937 cells. In K562 cells, C1q reduced adsorption of DENV-1/4G2 and exerted a dual inhibitory effect on adsorption and internalization of DENV-1/2H2. Distinct endocytic pathways in the presence of antibody corresponded to conditions where C1q produced a differential action. Also, C1q did not affect the intrinsic cell response mediated by FcγR in human myeloid cells. The modulation of ADE of DENV-1 by C1q is dependent on the FcγR expressed on immune cells and the specificity of the antibody comprising the immune complex. Understanding protective and pathogenic mechanisms in the humoral response to DENV infections is crucial for the successful design of antivirals and vaccines.

Natural Product-Derived Phytochemicals for Influenza A Virus (H1N1) Prevention and Treatment

Influenza A (H1N1) viruses are prone to antigenic mutations and are more variable than other influenza viruses. Therefore, they have caused continuous harm to human public health since the pandemic in 2009 and in recent times. Influenza A (H1N1) can be prevented and treated in various ways, such as direct inhibition of the virus and regulation of human immunity. Among antiviral drugs, the use of natural products in treating influenza has a long history, and natural medicine has been widely considered the focus of development programs for new, safe anti-influenza drugs. In this paper, we focus on influenza A (H1N1) and summarize the natural product-derived phytochemicals for influenza A virus (H1N1) prevention and treatment, including marine natural products, flavonoids, alkaloids, terpenoids and their derivatives, phenols and their derivatives, polysaccharides, and derivatives of natural products for prevention and treatment of influenza A (H1N1) virus. We further discuss the toxicity and antiviral mechanism against influenza A (H1N1) as well as the druggability of natural products. We hope that this review will facilitate the study of the role of natural products against influenza A (H1N1) activity and provide a promising alternative for further anti-influenza A drug development.

Exploring carrageenan: From seaweed to biomedicine-A comprehensive review

Biomaterials are pivotal in the realms of tissue engineering, regenerative medicine, and drug delivery and serve as fundamental building blocks. Within this dynamic landscape, polymeric biomaterials emerge as the frontrunners, offering unparalleled versatility across physical, chemical, and biological domains. Natural polymers, in particular, captivate attention for their inherent bioactivity. Among these, carrageenan (CRG), extracted from red seaweeds, stands out as a naturally occurring polysaccharide with immense potential in various biomedical applications. CRG boasts a unique array of properties, encompassing antiviral, antibacterial, immunomodulatory, antihyperlipidemic, antioxidant, and antitumor attributes, positioning it as an attractive choice for cutting-edge research in drug delivery, wound healing, and tissue regeneration. This comprehensive review encapsulates the multifaceted properties of CRG, shedding light on the chemical modifications that it undergoes. Additionally, it spotlights pioneering research that harnesses the potential of CRG to craft scaffolds and drug delivery systems, offering high efficacy in the realms of tissue repair and disease intervention. In essence, this review celebrates the remarkable versatility of CRG and its transformative role in advancing biomedical solutions.

Anti-herpes simplex virus activities and mechanisms of marine derived compounds

Herpes simplex virus (HSV) is the most widely prevalent herpes virus worldwide, and the herpetic encephalitis and genital herpes caused by HSV infection have caused serious harm to human health all over the world. Although many anti-HSV drugs such as nucleoside analogues have been ap-proved for clinical use during the past few decades, important issues, such as drug resistance, toxicity, and high cost of drugs, remain unresolved. Recently, the studies on the anti-HSV activities of marine natural products, such as marine polysaccharides, marine peptides and microbial secondary metabolites are attracting more and more attention all over the world. This review discusses the recent progress in research on the anti-HSV activities of these natural compounds obtained from marine organisms, relating to their structural features and the structure-activity relationships. In addition, the recent findings on the different anti-HSV mechanisms and molecular targets of marine compounds and their potential for therapeutic application will also be summarized in detail.

Expanding the synthesis of a library of potent glucuronic acid glycodendrons for Dengue virus inhibition

Multivalent glycodendrons are valuable tools to mimic many structural and functional features of cell-surface glycoconjugates and its focal position scaffolds represent important components to increase specificity and affinity. Previous work in our group described the preparation of a tetravalent glucuronic acid dendron that binds with good affinity to Dengue virus envelope protein (KD = 22 μM). Herein, the chemical synthesis and binding analysis of a new library of potent glucuronic acid dendrons bearing different functional group at the focal position and different level of multivalency are described. Their chemical synthesis was performed sequentially in three stages and with good yields. Namely a) the chemical synthesis of the oligo and polyalkynyl scaffolds, b) assembling with fully protected glucuronic acid-based azide units by using a microwave assisted copper-catalysed azide-alkyne cycloaddition reaction and c) sequential deprotection of hydroxyl and carboxylic acid groups. Surface Plasmon Resonance studies have demonstrated that the valency and the focal position functional group exert influence on the interaction with Dengue virus envelope protein. Molecular modelling studies were carried out in order to understand the binding observed. This work reports an efficient glycodendrons chemical synthesis that provides appropriate focal position functional group and multivalence, that offer an easy and versatile strategy to find new active compounds against Dengue virus.

Nanotechnology-driven improvisation of red algae-derived carrageenan for industrial and bio-medical applications

Algae biomass has been recognized as feedstock with diverse application including production of biofuel, biofertilizer, animal feed, wastewater treatment and bioremediation. In addition, algae species are a potential reservoir of metabolites and polymers with potential to be utilized for biomedicine, healthcare and industrial purposes. Carrageenan is one such medicinally and industrially significant polysaccharide which is extracted from red algae species (Kappaphycus alvarezii and Eucheuma denticulatum, among the common species). The extraction process of carrageenan is affected by different environmental factors and the source of biomass, which can vary and significantly impact the yield. Diverse applications of carrageenan include hydrogel beads, bio-composites, pharmacological properties, application in cosmetics, food and related industries. Carrageenan biological activities including antioxidant, anti-inflammatory, antimicrobial, and antitumor activities are significantly influenced by sulfation pattern, yield percentage and molecular weight. In addition to natural biomedical potential of carrageenan, synergetic effect of carrageenan- nanocomposites exhibit potential for further improvisation of biomedical applications. Nanotechnology driven bio-composites of carrageenan remarkably improve the quality of films, food packaging, and drug delivery systems. Such nano bio-composites exhibit enhanced stability, biodegradability, and biocompatibility, making them suitable alternatives for drug delivery, wound-healing, and tissue engineering applications. The present work is a comprehensive study to analyze biomedical and other applications of Carrageenan along with underlying mechanism or mode of action along with synergetic application of nanotechnology.

Metabolic Profiling, Antiviral Activity and the Microbiome of Some Mauritian Soft Corals

Soft corals, recognized as sessile marine invertebrates, rely mainly on chemical, rather than physical defense, by secreting intricate secondary metabolites with plausible pharmaceutical implication. Their ecological niche encompasses a diverse community of symbiotic microorganisms which potentially contribute to the biosynthesis of these bioactive metabolites. The emergence of new viruses and heightened viral resistance underscores the urgency to explore novel pharmacological reservoirs. Thus, marine organisms, notably soft corals and their symbionts, have drawn substantial attention. In this study, the chemical composition of four Mauritian soft corals: Sinularia polydactya, Cespitularia simplex, Lobophytum patulum, and Lobophytum crassum was investigated using LC-MS techniques. Concurrently, Illumina 16S metagenomic sequencing was used to identify the associated bacterial communities in the named soft corals. The presence of unique biologically important compounds and vast microbial communities found therein was further followed up to assess their antiviral effects against SARS-CoV-2 and HPV pseudovirus infection. Strikingly, among the studied soft corals, L. patulum displayed an expansive repertoire of unique metabolites alongside a heightened bacterial consort. Moreover, L. patulum extracts exerted some promising antiviral activity against SARS-CoV-2 and HPV pseudovirus infection, and our findings suggest that L. patulum may have the potential to serve as a therapeutic agent in the prevention of infectious diseases, thereby warranting further investigation.

Biological activity of algal derived carrageenan: A comprehensive review in light of human health and disease

Carrageenans are a family of natural linear sulfated polysaccharides derived from red seaweeds and used as a common food additive. Carrageenan's properties, impact on health, and aesthetic benefits have all been studied for a long time; however, the mechanisms are still unclear. In pharmaceutical aspects, carrageenan displayed potential antioxidant and immunomodulatory properties in both in vivo and in vitro action. It also contributes to potential disease-preventive activities through dynamic modulation of important intracellular signaling pathways, regulation of ROS buildup, and preservation of major cell survival and death processes which leads to potential drug development. Furthermore, the chemical synthesis of the current bioactive medicine with confirmational rearrangement may increase availability and bioactivity needs diligent examination. In this review, we give an up-to-date overview of recent research on Carrageenan with reference to health and therapeutic advantages. In addition, we have focused on structural conformation and its primary strategic deployment in disease prevention, as well as the mechanistic investigation of how it functions to combat various disease-preventive employed for future therapeutic interventions. This review may get new insights into the possible novel role of carrageenan and open up a novel disease-preventive mechanism and enhance human health.

Host Cell Targets for Unconventional Antivirals against RNA Viruses

The recent COVID-19 crisis has highlighted the importance of RNA-based viruses. The most prominent members of this group are SARS-CoV-2 (coronavirus), HIV (human immunodeficiency virus), EBOV (Ebola virus), DENV (dengue virus), HCV (hepatitis C virus), ZIKV (Zika virus), CHIKV (chikungunya virus), and influenza A virus. With the exception of retroviruses which produce reverse transcriptase, the majority of RNA viruses encode RNA-dependent RNA polymerases which do not include molecular proofreading tools, underlying the high mutation capacity of these viruses as they multiply in the host cells. Together with their ability to manipulate the immune system of the host in different ways, their high mutation frequency poses a challenge to develop effective and durable vaccination and/or treatments. Consequently, the use of antiviral targeting agents, while an important part of the therapeutic strategy against infection, may lead to the selection of drug-resistant variants. The crucial role of the host cell replicative and processing machinery is essential for the replicative cycle of the viruses and has driven attention to the potential use of drugs directed to the host machinery as therapeutic alternatives to treat viral infections. In this review, we discuss small molecules with antiviral effects that target cellular factors in different steps of the infectious cycle of many RNA viruses. We emphasize the repurposing of FDA-approved drugs with broad-spectrum antiviral activity. Finally, we postulate that the ferruginol analog (18-(phthalimide-2-yl) ferruginol) is a potential host-targeted antiviral.

Inhibition of dengue virus infection by trifluoperazine

Dengue virus (DENV), a member of the genus Flavivirus, family Flaviviridae, is the most widespread viral pathogen transmitted to humans by mosquitoes. Despite the increased incidence of DENV infection, there are no antiviral drugs available for treatment or prevention. Phenothiazines are heterocyclic compounds with various pharmacological properties that are very adaptable for drug repurposing. In the present report, we analyzed the antiviral activity against DENV and the related Zika virus (ZIKV) of trifluoperazine (TFP), a phenothiazine derivative in clinical use as an antipsychotic and antiemetic agent. TFP exhibited dose-dependent inhibitory activity against the four DENV serotypes and ZIKV in monkey Vero cells at non-cytotoxic concentrations with 50% effective concentration values in the range 1.6-6.4 µM. A similar level of antiviral efficacy was exhibited by TFP against flavivirus infection in the human cell lines A549 and HepG2. Mechanistic studies, performed using time-dependent infectivity assays, real-time RT-PCR, Western blot, and immunofluorescence techniques, indicated that uncoating of the virus during penetration into the cell was the main target for TFP in infected cells, but the compound also exerted a minor effect on a late stage of the virus multiplication cycle. This study demonstrates that TFP, a pharmacologically active phenothiazine, is a selective inhibitor of DENV multiplication in cell culture. Our findings open perspectives for the repositioning of phenothiazines like TFP with a wide spectrum of antiviral efficacy as potential agents for the control of pathogenic flaviviruses.

Novel Exopolysaccharide from Marine Bacillus subtilis with Broad Potential Biological Activities: Insights into Antioxidant, Anti-Inflammatory, Cytotoxicity, and Anti-Alzheimer Activity

In the presented study, Bacillus subtilis strain AG4 isolated from marine was identified based on morphological, physiological, phylogenetic characteristics and an examination of 16S rRNA sequences. Novel exopolysaccharide (EPSR4) was extracted and isolated from the Bacillus subtilis strain as a major fraction of exopolysaccharide (EPS). The analysis of structural characterization indicated that EPSR4 is a β-glycosidic sulphated heteropolysaccharide (48.2%) with a molecular weight (Mw) of 1.48 × 104 g/mole and has no uronic acid. Analysis of monosaccharide content revealed that EPSR4 consists of glucose, rhamnose and arabinose monosaccharide in a molar ratio of 5:1:3, respectively. Morphological analysis revealed that EPSR4 possess a high crystallinity degree with a significant degree of porosity, and its aggregation and conformation in the lipid phase might have a significant impact on the bioactivity of EPSR4. The biological activity of EPSR4 was screened and evaluated by investigating its antioxidant, cytotoxicity, anti-inflammatory, and anti-Alzheimer activities. The antioxidant activity results showed that EPSR4 has 97.6% scavenging activity toward DPPH free radicals at 1500 µg/mL, with an IC50 value of 300 µg/mL, and 64.8% at 1500 µg/mL toward hydrogen peroxide free radicals (IC50 = 1500 µg/mL, 30 min). Furthermore, EPSR4 exhibited considerable inhibitory activity towards the proliferation of T-24 (bladder carcinoma), A-549 (lung cancer) and HepG-2 (hepatocellular carcinoma) cancer cell lines with IC50 of 244 µg/mL, 148 µg/mL and 123 µg/mL, respectively. An evaluation of anti-inflammatory activity revealed that EPSR4 has potent lipoxygenase (LOX) inhibitory activity (IC50 of 54.3 µg/mL) and a considerable effect on membrane stabilization (IC50 = 112.2 ± 1.2 µg/mL), while it showed cyclooxygenase (COX2) inhibitory activity up to 125 µg/mL. Finally, EPSR4 showed considerable inhibitory activity towards acetylcholine esterase activity. Taken together, this study reveals that Bacillus subtilis strain AG4 could be considered as a potential natural source of novel EPS with potent biological activities that would be useful for the healthcare system.

Advances in Research on Antiviral Activities of Sulfated Polysaccharides from Seaweeds

In recent years, various viral diseases have suddenly erupted, resulting in widespread infection and death. A variety of biological activities from marine natural products have gradually attracted the attention of people. Seaweeds have a wide range of sources, huge output, and high economic benefits. This is very promising in the pharmaceutical industry. In particular, sulfated polysaccharides derived from seaweeds, considered a potential source of bioactive compounds for drug development, have shown antiviral activity against a broad spectrum of viruses, mainly including common DNA viruses and RNA viruses. In addition, sulfated polysaccharides can also improve the body’s immunity. This review focuses on recent advances in antiviral research on the sulfated polysaccharides from seaweeds, including carrageenan, galactan, fucoidan, alginate, ulvan, p-KG03, naviculan, and calcium spirulan. We hope that this review will provide new ideas for the development of COVID-19 therapeutics and vaccines.

Antiviral Polymers: A Review

Polymers, due to their high molecular weight, tunable architecture, functionality, and buffering effect for endosomal escape, possess unique properties as a carrier or prophylactic agent in preventing pandemic outbreak of new viruses. Polymers are used as a carrier to reduce the minimum required dose, bioavailability, and therapeutic effectiveness of antiviral agents. Polymers are also used as multifunctional nanomaterials to, directly or indirectly, inhibit viral infections. Multifunctional polymers can interact directly with envelope glycoproteins on the viral surface to block fusion and entry of the virus in the host cell. Polymers can indirectly mobilize the immune system by activating macrophages and natural killer cells against the invading virus. This review covers natural and synthetic polymers that possess antiviral activity, their mechanism of action, and the effect of material properties like chemical composition, molecular weight, functional groups, and charge density on antiviral activity. Natural polymers like carrageenan, chitosan, fucoidan, and phosphorothioate oligonucleotides, and synthetic polymers like dendrimers and sialylated polymers are reviewed. This review discusses the steps in the viral replication cycle from binding to cell surface receptors to viral-cell fusion, replication, assembly, and release of the virus from the host cell that antiviral polymers interfere with to block viral infections.

A review on structural genomics approach applied for drug discovery against three vector-borne viral diseases: Dengue, Chikungunya and Zika

Structural genomics involves the advent of three-dimensional structures of the genome encoded proteins through various techniques available. Numerous structural genomics research groups have been developed across the globe and they contribute enormously to the identification of three-dimensional structures of various proteins. In this review, we have discussed the applications of the structural genomics approach towards the discovery of potential lead-like molecules against the genomic drug targets of three vector-borne diseases, namely, Dengue, Chikungunya and Zika. Currently, all these three diseases are associated with the most important global public health problems and significant economic burden in tropical countries. Structural genomics has accelerated the identification of novel drug targets and inhibitors for the treatment of these diseases. We start with the current development status of the drug targets and antiviral drugs against these three diseases and conclude by describing challenges that need to be addressed to overcome the shortcomings in the process of drug discovery.

Polysaccharides and Тheir Derivatives as Potential Antiviral Molecules

In the current context of the COVID-19 pandemic, it appears that our scientific resources and the medical community are not sufficiently developed to combat rapid viral spread all over the world. A number of viruses causing epidemics have already disseminated across the world in the last few years, such as the dengue or chinkungunya virus, the Ebola virus, and other coronavirus families such as Middle East respiratory syndrome (MERS-CoV) and severe acute respiratory syndrome (SARS-CoV). The outbreaks of these infectious diseases have demonstrated the difficulty of treating an epidemic before the creation of vaccine. Different antiviral drugs already exist. However, several of them cause side effects or have lost their efficiency because of virus mutations. It is essential to develop new antiviral strategies, but ones that rely on more natural compounds to decrease the secondary effects. Polysaccharides, which have come to be known in recent years for their medicinal properties, including antiviral activities, are an excellent alternative. They are essential for the metabolism of plants, microorganisms, and animals, and are directly extractible. Polysaccharides have attracted more and more attention due to their therapeutic properties, low toxicity, and availability, and seem to be attractive candidates as antiviral drugs of tomorrow.

An Overview of Potential Seaweed-Derived Bioactive Compounds for Pharmaceutical Applications

Nowadays, seaweeds are widely involved in biotechnological applications. Due to the variety of bioactive compounds in their composition, species of phylum Ochrophyta, class Phaeophyceae, phylum Rhodophyta and Chlorophyta are valuable for the food, cosmetic, pharmaceutical and nutraceutical industries. Seaweeds have been consumed as whole food since ancient times and used to treat several diseases, even though the mechanisms of action were unknown. During the last decades, research has demonstrated that those unique compounds express beneficial properties for human health. Each compound has peculiar properties (e.g., antioxidant, antimicrobial, antiviral activities, etc.) that can be exploited to enhance human health. Seaweed’s extracted polysaccharides are already involved in the pharmaceutical industry, with the aim of replacing synthetic compounds with components of natural origin. This review aims at a better understanding of the recent uses of algae in drug development, with the scope of replacing synthetic compounds and the multiple biotechnological applications that make up seaweed’s potential in industrial companies. Further research is needed to better understand the mechanisms of action of seaweed’s compounds and to embrace the use of seaweeds in pharmaceutical companies and other applications, with the final scope being to produce sustainable and healthier products.

Broad Spectrum Algae Compounds Against Viruses

The pharmaceutical industry is currently trying to develop new bioactive compounds to inactivate both enveloped and non-enveloped viruses for therapeutic purposes. Consequently, microalgal and macroalgal bioactive compounds are being explored by pharmaceutical, as well as biotechnology and food industries. In this review, we show how compounds produced by algae include important candidates for viral control applications. We discuss their mechanisms of action and activity against enveloped and non-enveloped viruses, including those causing infections by enteric, parenteral, and respiratory routes. Indeed, algal products have potential in human and animal medicine.

Antimicrobial Mechanisms of Biomaterials: From Macro to Nano

Overcoming the global concern of antibiotic resistance is one of the biggest challenge faced by scientists today and the key to tackle this issue of emerging infectious diseases is the...

Antiviral Strategies Using Natural Source-Derived Sulfated Polysaccharides in the Light of the COVID-19 Pandemic and Major Human Pathogenic Viruses

Only a mere fraction of the huge variety of human pathogenic viruses can be targeted by the currently available spectrum of antiviral drugs. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak has highlighted the urgent need for molecules that can be deployed quickly to treat novel, developing or re-emerging viral infections. Sulfated polysaccharides are found on the surfaces of both the susceptible host cells and the majority of human viruses, and thus can play an important role during viral infection. Such polysaccharides widely occurring in natural sources, specifically those converted into sulfated varieties, have already proved to possess a high level and sometimes also broad-spectrum antiviral activity. This antiviral potency can be determined through multifold molecular pathways, which in many cases have low profiles of cytotoxicity. Consequently, several new polysaccharide-derived drugs are currently being investigated in clinical settings. We reviewed the present status of research on sulfated polysaccharide-based antiviral agents, their structural characteristics, structure-activity relationships, and the potential of clinical application. Furthermore, the molecular mechanisms of sulfated polysaccharides involved in viral infection or in antiviral activity, respectively, are discussed, together with a focus on the emerging methodology contributing to polysaccharide-based drug development.

Iota-Carrageenan Inhibits Replication of SARS-CoV-2 and the Respective Variants of Concern Alpha, Beta, Gamma and Delta

The COVID-19 pandemic continues to spread around the world and remains a major public health threat. Vaccine inefficiency, vaccination breakthroughs and lack of supply, especially in developing countries, as well as the fact that a non-negligible part of the population either refuse vaccination or cannot be vaccinated due to age, pre-existing illness or non-response to existing vaccines intensify this issue. This might also contribute to the emergence of new variants, being more efficiently transmitted, more virulent and more capable of escaping naturally acquired and vaccine-induced immunity. Hence, the need of effective and viable prevention options to reduce viral transmission is of outmost importance. In this study, we investigated the antiviral effect of iota-, lambda- and kappa-carrageenan, sulfated polysaccharides extracted from red seaweed, on SARS-CoV-2 Wuhan type and the spreading variants of concern (VOCs) Alpha, Beta, Gamma and Delta. Carrageenans as part of broadly used nasal and mouth sprays as well as lozenges have the potential of first line defense to inhibit the infection and transmission of SARS-CoV-2. Here, we demonstrate by using a SARS-CoV-2 spike pseudotyped lentivirus particles (SSPL) system and patient-isolated SARS-CoV-2 VOCs to infect transgenic A549ACE2/TMPRSS2 and Calu-3 human lung cells that all three carrageenan types exert antiviral activity. Iota-carrageenan exhibits antiviral activity with comparable IC₅₀ values against the SARS-CoV-2 Wuhan type and the VOCs. Altogether, these results indicate that iota-carrageenan might be effective for prophylaxis and treatment of SARS-CoV-2 infections independent of the present and potentially future variants.

Iota-carrageenan and xylitol inhibit SARS-CoV-2 in Vero cell culture

Last year observed a global pandemic caused by SARS-CoV-2 (severe acute respiratory syndrome-coronavirus 2) infection affecting millions of individuals worldwide. There is an urgent unmet need to provide an easily producible and affordable medicine to prevent transmission and provide early treatment for this disease. Since the nasal cavity and the rhinopharynx are the sites of initial replication of SARS-CoV-2, a nasal spray may be an effective option to target SARS-CoV-2 infection. In this study, we tested the antiviral action of three candidate nasal spray formulations against SARS-CoV-2 in vitro. We determined that iota-carrageenan in concentrations as low as 6 μg/mL inhibits SARS-CoV-2 in vitro. The concentrations of iota-carrageenan with activity against SARS-CoV-2 in vitro may be easily achieved through the application of nasal sprays as commonly used in several countries. Recently a double-blind, placebo-controlled study showed that iota-carrageenan in isotonic sodium chloride reduces ca. five times the risk of infection by SARS-CoV-2 in health care personnel. Further, xylitol at a concentration of 50 mg/mL (ca. 329 mM) was found to exert some antiviral action, though this preliminary finding needs further confirmation.

Can the Nasal Cavity Help Tackle COVID-19?

Despite the progress made in the fight against the COVID-19 pandemic, it still poses dramatic challenges for scientists around the world. Various approaches are applied, including repurposed medications and alternative routes for administration. Several vaccines have been approved, and many more are under clinical and preclinical investigation. This review aims to systemize the available information and to outline the key therapeutic strategies for COVID-19, based on the nasal route of administration.

Efficacy of a Nasal Spray Containing Iota-Carrageenan in the Postexposure Prophylaxis of COVID-19 in Hospital Personnel Dedicated to Patients Care with COVID-19 Disease

BACKGROUND

Iota-Carrageenan (I-C) is a sulfate polysaccharide synthesized by red algae, with demonstrated antiviral activity and clinical efficacy as nasal spray in the treatment of common cold. In vitro, I-C inhibits SARS-CoV-2 infection in cell culture.

RESEARCH QUESTION

Can a nasal spray with Iota-Carrageenan be useful in the prophylaxis of COVID-19 in health care workers managing patients with COVID-19 disease?

STUDY DESIGN AND METHODS

This is a pilot pragmatic multicenter, randomized, double-blind, placebo-controlled study assessing the use of a nasal spray containing I-C in the prophylaxis of COVID-19 in hospital personnel dedicated to care of COVID-19 patients. Clinically healthy physicians, nurses, kinesiologists and other health care providers managing patients hospitalized for COVID-19 were assigned in a 1:1 ratio to receive four daily doses of I-C spray or placebo for 21 days. The primary end point was clinical COVID-19, as confirmed by reverse transcriptase polymerase chain reaction testing, over a period of 21 days. The trial is registered at ClinicalTrials.gov (NCT04521322).

RESULTS

A total of 394 individuals were randomly assigned to receive I-C or placebo. Both treatment groups had similar baseline characteristics. The incidence of COVID-19 differs significantly between subjects receiving the nasal spray with I-C (2 of 196 [1.0%]) and those receiving placebo (10 of 198 [5.0%]). Relative risk reduction: 79.8% (95% CI 5.3 to 95.4; p=0.03). Absolute risk reduction: 4% (95% CI 0.6 to 7.4).

INTERPRETATION

In this pilot study a nasal spray with I-C showed significant efficacy in preventing COVID-19 in health care workers managing patients with COVID-19 disease.

CLINICAL TRIALS REGISTRATION

NCT04521322.

Potential Antiviral Properties of Industrially Important Marine Algal Polysaccharides and Their Significance in Fighting a Future Viral Pandemic

Over the decades, the world has witnessed diverse virus associated pandemics. The significant inhibitory effects of marine sulfated polysaccharides against SARS-CoV-2 shows its therapeutic potential in future biomedical applications and drug development. Algal polysaccharides exhibited significant role in antimicrobial, antitumor, antioxidative, antiviral, anticoagulant, antihepatotoxic and immunomodulating activities. Owing to their health benefits, the sulfated polysaccharides from marine algae are a great deal of interest globally. Algal polysaccharides such as agar, alginate, carrageenans, porphyran, fucoidan, laminaran and ulvans are investigated for their nutraceutical potential at different stages of infection processes, structural diversity, complexity and mechanism of action. In this review, we focus on the recent antiviral studies of the marine algae-based polysaccharides and their potential towards antiviral medicines.

Marine bacterial exopolysaccharide EPS11 inhibits migration and invasion of liver cancer cells by directly targeting collagen I

Many natural polysaccharides have significant anticancer activity with low toxicity, but the complex chemical structures make in-depth studies of the involved mechanisms extremely difficult. The purpose of this study was to investigate the effect of the marine bacterial exopolysaccharide (exopolysaccharide 11 [EPS11]) on liver cancer metastasis to explore the underlying target protein and molecular mechanism. We found that EPS11 significantly suppressed cell adhesion, migration, and invasion in liver cancer cells. Proteomic analysis showed that EPS11 induced downregulation of proteins related to the extracellular matrix–receptor interaction signaling pathway. In addition, the direct pharmacological target of EPS11 was identified as collagen I using cellular thermal shift assays. Surface plasmon resonance and pull-down assays further confirmed the specific binding of EPS11 to collagen I. Moreover, EPS11 was shown to inhibit tumor metastasis by directly modulating collagen I activity via the β1-integrin–mediated signaling pathway. Collectively, our study demonstrated for the first time that collagen I could be a direct pharmacological target of polysaccharide drugs. Moreover, directly targeting collagen I may be a promising strategy for finding novel carbohydrate-based drugs.

Andrographolide as a potent and promising antiviral agent

Andrographolide is a labdane diterpenoid extracted and purified from the aerial parts of plants belonging to genus Andrographis (Acanthaceae). The research has shown the plant based compound is low cytotoxic, having antimicrobial, anti-cancer, antiviral and anti-parasitic effects. Andrographolide both prevent spread as well as transmission of virus to neighboring cells by interfering with different cell signaling pathways. In addition to its medicinal value, plant has been found having nutritional value. Therefore being cost effective, easy availability and having nutritional value as a natural supplement, can be used to improve the quality of life in countries having low standard of living. Due to the limited number of effective vaccines, the plant-based antiviral drugs have provided considerable hope for fighting against the viral infections. The plant-derived compound when produced in large quantities is cost effective with low cytotoxic effects. However, much deep insight research at the molecular level is needed to develop the molecules against the viral infection. This paper aims to highlight the antiviral role of Andrographolide that can made significant contributions toward the improvement of human health and will also summarize the current status and future strategies concerning the therapeutic applications of Andrographolide to combat different viral disease in humans.

Antiviral Activity of Carrageenans and Processing Implications

Carrageenan and carrageenan oligosaccharides are red seaweed sulfated carbohydrates with well-known antiviral properties, mainly through the blocking of the viral attachment stage. They also exhibit other interesting biological properties and can be used to prepare different drug delivery systems for controlled administration. The most active forms are λ-, ι-, and κ-carrageenans, the degree and sulfation position being determined in their properties. They can be obtained from sustainable worldwide available resources and the influence of manufacturing on composition, structure, and antiviral properties should be considered. This review presents a survey of the antiviral properties of carrageenan in relation to the processing conditions, particularly those assisted by intensification technologies during the extraction stage, and discusses the possibility of further chemical modifications.

Marine Sulfated Polysaccharides as Promising Antiviral Agents: A Comprehensive Report and Modeling Study Focusing on SARS CoV-2

SARS-CoV-2 (severe acute respiratory syndrome coronavirus-2) is a novel coronavirus strain that emerged at the end of 2019, causing millions of deaths so far. Despite enormous efforts being made through various drug discovery campaigns, there is still a desperate need for treatments with high efficacy and selectivity. Recently, marine sulfated polysaccharides (MSPs) have earned significant attention and are widely examined against many viral infections. This article attempted to produce a comprehensive report about MSPs from different marine sources alongside their antiviral effects against various viral species covering the last 25 years of research articles. Additionally, these reported MSPs were subjected to molecular docking and dynamic simulation experiments to ascertain potential interactions with both the receptor-binding domain (RBD) of SARS CoV-2's spike protein (S-protein) and human angiotensin-converting enzyme-2 (ACE2). The possible binding sites on both S-protein's RBD and ACE2 were determined based on how they bind to heparin, which has been reported to exhibit significant antiviral activity against SARS CoV-2 through binding to RBD, preventing the virus from affecting ACE2. Moreover, our modeling results illustrate that heparin can also bind to and block ACE2, acting as a competitor and protective agent against SARS CoV-2 infection. Nine of the investigated MSPs candidates exhibited promising results, taking into consideration the newly emerged SARS CoV-2 variants, of which five were not previously reported to exert antiviral activity against SARS CoV-2, including sulfated galactofucan (1), sulfated polymannuroguluronate (SPMG) (2), sulfated mannan (3), sulfated heterorhamnan (8), and chondroitin sulfate E (CS-E) (9). These results shed light on the importance of sulfated polysaccharides as potential SARS-CoV-2 inhibitors.

Viral inhibitors derived from macroalgae, microalgae, and cyanobacteria: A review of antiviral potential throughout pathogenesis

Viruses are abiotic obligate parasites utilizing complex mechanisms to hijack cellular machinery and reproduce, causing multiple harmful effects in the process. Viruses represent a growing global health concern; at the time of writing, COVID-19 has killed at least two million people around the world and devastated global economies. Lingering concern regarding the virus' prevalence yet hampers return to normalcy. While catastrophic in and of itself, COVID-19 further heralds in a new era of human-disease interaction characterized by the emergence of novel viruses from natural sources with heretofore unseen frequency. Due to deforestation, population growth, and climate change, we are encountering more viruses that can infect larger groups of people with greater ease and increasingly severe outcomes. The devastation of COVID-19 and forecasts of future human/disease interactions call for a creative reconsideration of global response to infectious disease. There is an urgent need for accessible, cost-effective antiviral (AV) drugs that can be mass-produced and widely distributed to large populations. Development of AV drugs should be informed by a thorough understanding of viral structure and function as well as human biology. To maximize efficacy, minimize cost, and reduce development of drug-resistance, these drugs would ideally operate through a varied set of mechanisms at multiple stages throughout the course of infection. Due to their abundance and diversity, natural compounds are ideal for such comprehensive therapeutic interventions. Promising sources of such drugs are found throughout nature; especially remarkable are the algae, a polyphyletic grouping of phototrophs that produce diverse bioactive compounds. While not much literature has been published on the subject, studies have shown that these compounds exert antiviral effects at different stages of viral pathogenesis. In this review, we follow the course of viral infection in the human body and evaluate the AV effects of algae-derived compounds at each stage. Specifically, we examine the AV activities of algae-derived compounds at the entry of viruses into the body, transport through the body via the lymph and blood, infection of target cells, and immune response. We discuss what is known about algae-derived compounds that may interfere with the infection pathways of SARS-CoV-2; and review which algae are promising sources for AV agents or AV precursors that, with further investigation, may yield life-saving drugs due to their diversity of mechanisms and exceptional pharmaceutical potential.

Formulation of a Composite Nasal Spray Enabling Enhanced Surface Coverage and Prophylaxis of SARS-COV-2

Airborne pathogens pose high risks in terms of both contraction and transmission within the respiratory pathways, particularly the nasal region. However, there is little in the way of adequate intervention that can protect an individual or prevent further spread. This study reports on a nasal formulation with the capacity to combat such challenges, focusing on severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Formulation of a polysaccharide-based spray, known for its mucoadhesive properties, is undertaken and it is characterized for its mechanical, spray distribution, and antiviral properties. The ability to engineer key mechanical characteristics such as dynamic yield stresses and high coverage is shown, through systematic understanding of the composite mixture containing both gellan and λ-carrageenan. Furthermore, the spray systems demonstrate highly potent capacities to prevent SARS-CoV-2 infection in Vero cells, resulting in complete inhibition when either treating, the cells, or the virus, prior to challenging for infection. From this data, a mechanism for both prophylaxis and prevention is proposed; where entrapment within a polymeric coating sterically blocks virus uptake into the cells, inactivating the virus, and allowing clearance within the viscous medium. As such, a fully preventative spray is formulated, targeted at protecting the lining of the upper respiratory pathways against SARS-CoV-2.

The antiviral activity of iota-, kappa-, and lambda-carrageenan against COVID-19: A critical review

Objective

There is no specific antiviral treatment available for coronavirus disease 2019 (COVID-19). Among the possible natural constituents is carrageenan, a polymer derived from marine algae that possesses a variety of antiviral properties. The purpose of this review was to summarize the evidence supporting carrageenan subtypes' antiviral activity against the emerging severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causative agent of COVID-19.

Methods

PubMed/MEDLINE and Google Scholar searches were conducted for publications using the terms 'carrageenan', 'iota carrageenan', 'kappa carrageenan', lambda-carrageenan', 'coronavirus', 'common cold', 'rhinovirus', and 'SARS-CoV-2' search was also done in grey literature to increase our understanding. A search for the word "carrageenan" was also carried out. Most of the publications were discussed in narrative.

Results

Carrageenan has been shown to have potent antiviral activity against both coronaviruses (coronavirus NL63, SARS-CoV-2) and non-coronaviruses such as dengue virus, herpes simplex virus, cytomegalovirus, vaccinia virus, vesicular stomatitis virus, sindbis virus, human immunodeficiency virus, influenza virus, human papillomavirus, rabies virus, junin virus, tacaribe virus, African swine fever, bovine herpes virus, suid herpes virus, and rhinovirus. No in vivo study has been conducted using carrageenan as an anti-SARS-CoV-2 agent. The majority of the in vivo research was done on influenza, a respiratory virus that causes common cold together with coronavirus. Thus, various clinical trials were conducted to determine the transferability of these in vitro data to clinical effectiveness against SARS-CoV-2. When combined with oral ivermectin, nasally administered iota-carrageenan improved outcome in COVID-19 patients. It is still being tested in clinics for single-dose administration.

Conclusion

Though the carrageenan exhibited potent antiviral activity against SARS-CoV-2 and was used to treat COVID-19 under emergency protocol in conjunction with oral medications such as ivermectin, there is no solid evidence from clinical trials to support its efficacy. Thus, clinical trials are required to assess its efficacy for COVID-19 treatment prior to broad application.

Ultra-high-performance liquid chromatography charge transfer dissociation mass spectrometry (UHPLC-CTD-MS) as a tool for analyzing the structural heterogeneity in carrageenan oligosaccharides

Ultra-high-performance liquid chromatography (UHPLC) with charge transfer dissociation mass spectrometry (CTD-MS) is presented for the analysis of a mixture of complex sulfated oligosaccharides. The mixture contained kappa (κ), iota (ι), and lambda (λ) carrageenans that contain anhydro bridges, different degrees of sulfation ranging from one to three per dimer, different positioning of the sulfate groups along the backbone, and varying degrees of polymerization (DP) between 4 and 12. Optimization studies using standard mixtures of carrageenans helped establish the optimal conditions for online UHPLC-CTD-MS/MS analysis. Optimization included (1) UHPLC conditions; (2) ion source conditions, such as the capillary voltage, drying gas and nebulizing gas temperature, and flow rate; and (3) CTD-MS conditions, including data-dependent CTD-MS. The UHPLC-CTD results were contrasted with UHPLC-CID results of the same mixture on the same instrument. Whereas CID tends to produce B/Y and C/Z ions with many neutral losses, CTD produced more abundant A/X ions and less abundant neutral losses, which enabled more confident structural detail. The results demonstrate that He-CTD is compatible with the timescale of UHPLC and provides more structural information about carrageenans compared to state-of-the-art methods like UHPLC-CID analysis.

Dengue structural proteins as antiviral drug targets: Current status in the drug discovery & development

Dengue virus belongs to the class of RNA viruses and subclass of enveloped single-stranded positive-sense RNA virus. It causes dengue fever (DF), dengue hemorrhagic fever (DHF), or dengue shock syndrome (DSS), where DHF and DSS are life-threatening. Even though dengue is an age-old disease, it is still a mystery and continues to be a global threat. Numerous attempts have been carried out in the past few decades to eradicate the virus through vaccine and antiviral drugs, but still battle continues. In this review, the possible drug targets for discovery and development of potential antiviral drugs against structural proteins of dengue virus, the current development status of the antiviral drugs against dengue around the world, and challenges that need to be addressed to overcome the shortcomings in the process of drug discovery have been discussed.

Potential of algal metabolites for the development of broad-spectrum antiviral therapeutics: Possible implications in COVID-19 therapy

Covid-19 pandemic severely affected human health worldwide. Till October 19, 2020, total confirmed patients of COVID-19 are 39,944,882, whereas 1,111,998 people died across the globe. Till to date, we do not have any specific medicine and/or vaccine to treat COVID-19; however, research is still going on at war footing. So far vaccine development is concerned, here it is noteworthy that till now three major variants (named A, B, and C) of severe acute respiratory syndrome-coronavirus2 (SARS-CoV-2) have been recognized. Increased mutational rate and formation of new viral variants may increase the attrition rate of vaccines and/or candidate chemotherapies. Herbal remedies are chemical cocktails, thus open another avenue for effective antiviral therapeutics development. In fact, India is a large country, which is densely populated, but the overall severity of COVID-19 per million populations is lesser than any other country of the world. One of the major reasons for the aforesaid difference is the use of herbal remedies by the Government of India as a preventive measure for COVID-19. Therefore, the present review focuses on the epidemiology and molecular pathogenesis of COVID-19 and explores algal metabolites for their antiviral properties.

Antiviral Potential of Algal Metabolites-A Comprehensive Review

Historically, algae have stimulated significant economic interest particularly as a source of fertilizers, feeds, foods and pharmaceutical precursors. However, there is increasing interest in exploiting algal diversity for their antiviral potential. Here, we present an overview of 50-years of scientific and technological developments in the field of algae antivirals. After bibliometric analysis of 999 scientific references, a survey of 16 clinical trials and analysis of 84 patents, it was possible to identify the dominant algae, molecules and viruses that have been shaping and driving this promising field of research. A description of the most promising discoveries is presented according to molecule class. We observed a diverse range of algae and respective molecules displaying significant antiviral effects against an equally diverse range of viruses. Some natural algae molecules, like carrageenan, cyanovirin or griffithsin, are now considered prime reference molecules for their outstanding antiviral capacity. Crucially, while many algae antiviral applications have already reached successful commercialization, the large spectrum of algae antiviral capacities already identified suggests a strong potential for future expansion of this field.

Antiviral Compounds for Blocking Arboviral Transmission in Mosquitoes

Mosquito-borne arthropod-borne viruses (arboviruses) such as the dengue virus (DENV), Zika virus (ZIKV), and chikungunya virus (CHIKV) are important human pathogens that are responsible for significant global morbidity and mortality. The recent emergence and re-emergence of mosquito-borne viral diseases (MBVDs) highlight the urgent need for safe and effective vaccines, therapeutics, and vector-control approaches to prevent MBVD outbreaks. In nature, arboviruses circulate between vertebrate hosts and arthropod vectors; therefore, disrupting the virus lifecycle in mosquitoes is a major approach for combating MBVDs. Several strategies were proposed to render mosquitoes that are refractory to arboviral infection, for example, those involving the generation of genetically modified mosquitoes or infection with the symbiotic bacterium Wolbachia. Due to the recent development of high-throughput screening methods, an increasing number of drugs with inhibitory effects on mosquito-borne arboviruses in mammalian cells were identified. These antivirals are useful resources that can impede the circulation of arboviruses between arthropods and humans by either rendering viruses more vulnerable in humans or suppressing viral infection by reducing the expression of host factors in mosquitoes. In this review, we summarize recent advances in small-molecule antiarboviral drugs in mammalian and mosquito cells, and discuss how to use these antivirals to block the transmission of MBVDs.

Antiviral activity of lambda-carrageenan against influenza viruses and severe acute respiratory syndrome coronavirus 2

Influenza virus and coronavirus, belonging to enveloped RNA viruses, are major causes of human respiratory diseases. The aim of this study was to investigate the broad spectrum antiviral activity of a naturally existing sulfated polysaccharide, lambda-carrageenan (λ-CGN), purified from marine red algae. Cell culture-based assays revealed that the macromolecule efficiently inhibited both influenza A and B viruses with EC₅₀ values ranging from 0.3 to 1.4 μg/ml, as well as currently circulating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with an EC₅₀ value of 0.9 ± 1.1 μg/ml. No toxicity to the host cells was observed at concentrations up to 300 μg/ml. Plaque titration and western blot analysis verified that λ-CGN reduced expression of viral proteins in cell lysates and suppressed progeny virus production in culture supernatants in a dose-dependent manner. This polyanionic compound exerts antiviral activity by targeting viral attachment to cell surface receptors and preventing virus entry. Moreover, its intranasal administration to mice during influenza A viral challenge not only alleviated infection-mediated reductions in body weight but also protected 60% of mice from virus-induced mortality. Thus, λ-CGN could be a promising antiviral agent for preventing infection with several respiratory viruses.

Are Bioactive Molecules from Seaweeds a Novel and Challenging Option for the Prevention of HPV Infection and Cervical Cancer Therapy?-A Review

Cervical cancer represents one of the leading causes of cancer-related death in women all over the world. The infection with human papilloma virus (HPV) is one of the major risk factors for the development of premalignant lesions, which will progress to cervical cancer. Seaweeds are marine organisms with increased contents of bioactive compounds, which are described as potential anti-HPV and anti-cervical cancer agents. Our study aims to bring together all the results of the previous studies, conducted in order to highlight the potency of bioactive molecules from seaweeds, as anti-HPV and anti-cervical agents. This paper is a review of the English literature published between January 2010 and August 2020. We performed a systematic study in the Google Academic and PubMed databases using the key words "HPV infection", "anticancer", "seaweeds", "cervical cancer" and "carcinogenesis process", aiming to evaluate the effects of different bioactive molecules from marine algae on cervical cancer cell lines and on HPV-infected cells. Only original studies were considered for our research. None of the papers was excluded due to language usage or affiliation. Recent discoveries pointed out that sulfated polysaccharides, such as dextran sulfate heparan or cellulose sulfate, blocked the ability of HPV to infect cells, and inhibited the carcinogenesis process. Carrageenans inhibited the virions of HPV from binding the cellular wall. Fucoidan induced the growth inhibition of HeLa cervical cells in vitro. Heterofucans exhibited antiproliferative effects on cancer cell lines. Terpenoids from brown algae are also promising agents with anti-cervical cancer activity. Considering all the results of the previous studies, we observed that great amounts of bioactive molecules from seaweeds could treat both unapparent HPV infection and clinical visible disease. Furthermore, these molecules were very efficient in the treatment of invasive cervical carcinomas. In these conditions, we consider seaweeds extracts as a novel and challenging therapeutic strategy, and we hope that our study paves the way for further clinical trials in the field.

Antiviral activity of sulfated polysaccharides from marine algae and its application in combating COVID-19: Mini review

Marine-derived sulfated polysaccharides possess various antiviral activities against a broad range of enveloped and non-enveloped viruses. It has become the potential source of antiviral drugs for pharmaceutical development. In this review, we will discuss the different types of sulfated polysaccharides and their structural classification. Some of the major sulfated polysaccharides with potent antiviral activity, including carrageenan, agar, ulvan, fucoidan, and alginates, are considered in this review. The mechanism of these sulfated polysaccharides in inhibiting the different stages of the viral infection process inside the host cell is also demonstrated. It involves blocking the initial entry of the virus or inhibiting its transcription and translation by modulating the immune response of the host cell. In addition, we explore the potential of sulfated polysaccharides as antiviral agents in preventing recent Corona Virus Disease-2019 (COVID-19).

Antioxidant and cytotoxic activities of sulfated polysaccharides from five different edible seaweeds

In recent times, there has been a growing interest in the exploration of antioxidants and global trend toward the usage of seaweeds in the food industries. The low molecular weight up to 14 kDa sulfated polysaccharides of seaweeds (Portieria hornemannii, Spyridia hypnoides, Asparagopsis taxiformis, Centroceras clavulatum and Padina pavonica) were evaluated for in vitro antioxidant activities and cytotoxic assay using HeLa cell line and also characterized by FTIR. The high yield (7.74% alga dry wt.) of sulfated polysaccharide was observed in P. hornemannii followed by S. hypnoides (0.69%), C. clavulaum (0.55%) and A. taxiformis (0.17%). In the brown seaweed P. pavonica, the sulfated polysaccharide yield was 2.07%. High amount of sulfate was recorded in the polysaccharide of A. taxiformis followed by C. clavulaum, P. pavonica, S. hypnoides and P. hornemannii as indicative for bioactivity. The FTIR spectroscopic analysis supports the sulfated polysaccharides of S. hypnoides, C. clavulatum and A. taxiformis are similar to agar polymer whereas the spectral characteristics of P. hornemannii have similarities to carrageenan. The higher DPPH activity and reducing power were recorded in the polysaccharide of brown seaweed P. pavonica than the red seaweeds as follows: DPPH activities: S. hypnoides > A. taxiformis > C. clavulatum > P. hornimanii; Reducing power: A. taxiformis > P. hornimanii > S. hypnoides > C. clavulatum. The polysaccharide fractions contain up to 14 kDa from red seaweeds P. hornemannii and S. hypnoides followed by brown seaweed P. pavonica exhibit cytotoxic activity in HeLa cancer cell line (and are similar to structural properties of carrageenan extracted from P. hornemannii). The low molecular weight agar like polymer of S. hypnoides and alginate like brown seaweed P. pavonica showing better in vitro antioxidant activities that are capable of exhibiting cytotoxicity against HeLa cell line can be taken up further in-depth investigation for nutraceutical study.

Carrageenans as Broad-Spectrum Microbicides: Current Status and Challenges

Different kinds of red algae are enriched with chemically diverse carbohydrates. In particular, a group of sulfated polysaccharides, which were isolated from the cell walls of red algae, gained a large amount of attention due to their broad-spectrum antimicrobial activities. Within that group, carrageenans (CGs) were expected to be the first clinically applicable microbicides that could prevent various viral infections due to their superior antiviral potency and desirable safety profiles in subclinical studies. However, their anticipated beneficial effects could not be validated in human studies. To assess the value of a second attempt at pharmacologically developing CGs as a new class of preventive microbicides, all preclinical and clinical development processes of CG-based microbicides need to be thoroughly re-evaluated. In this review, the in vitro toxicities; in vivo safety profiles; and in vitro, ex vivo, and in vivo antiviral activities of CGs are summarized according to the study volume of their target viruses, which include human immunodeficiency virus, herpesviruses, respiratory viruses, human papillomavirus, dengue virus, and other viruses along with a description of their antiviral modes of action and development of antiviral resistance. This evaluation of the strengths and weaknesses of CGs will help provide future research directions that may lead to the successful development of CG-based antimicrobial prophylactics.

A Review of the Varied Uses of Macroalgae as Dietary Supplements in Selected Poultry with Special Reference to Laying Hen and Broiler Chickens

Seaweeds comprise ca. 12,000 species. Global annual harvest is ca. 30.13 million metric tonnes, (valued ca. $11.7 billion USD in 2016) for various commercial applications. The growing scope of seaweed-based applications in food, agricultural fertilizers, animal feed additives, pharmaceuticals, cosmetics and personal care is expected to boost market demand. Agriculture and animal feed applications held the second largest seaweed market share in 2017, and the combined market is anticipated to reach much higher values by 2024 due to the impacts of current research and development targeting enhanced animal health and productivity. In general, seaweeds have been utilized in animal feed as a rich source of carbohydrates, protein, minerals, vitamins and dietary fibers with relatively well-balanced amino acid profiles and a unique blend of bioactive compounds. Worldwide, the animal nutrition market is largely driven by rising demand for poultry feeds, which represents ca. 47% of the total consumption for all animal nutrition. This review provides an overview of the utilization of specific seaweeds as sustainable feed sources for poultry production, including a detailed survey of seaweed-supplemented diets on growth, performance, gastrointestinal flora, disease, immunity and overall health of laying/broiler hens. Anti-microbial effects of seaweeds are also discussed.

Antiviral activity of the natural alkaloid anisomycin against dengue and Zika viruses

Flaviviruses constitute a public health concern because of their global burden and the lack of specific antiviral treatment. Here we investigated the antiviral activity of the alkaloid anisomycin against dengue (DENV) and Zika (ZIKV) viruses. At non-cytotoxic concentrations, anisomycin strongly inhibited the replication of reference strains and clinical isolates of all DENV serotypes and Asian and African strains of ZIKV in Vero cells. Anisomycin also prevented DENV and ZIKV multiplication in human cell lines. While initial steps of DENV and ZIKV replicative cycle were unaffected, a high inhibition of viral protein expression was demonstrated after treatment with anisomycin. DENV RNA synthesis was strongly reduced in anisomycin treated cultures, but the compound did not exert a direct inhibitory effect on 2' O-methyltransferase or RNA polymerase activities of DENV NS5 protein. Furthermore, anisomycin-mediated activation of p38 signaling was not related to the antiviral action of the compound. The evaluation of anisomycin efficacy in a mouse model of ZIKV morbidity and mortality revealed that animals treated with a low dose of anisomycin exhibited a significant reduction in viremia levels and died significantly later than the control group. This protective effect was lost at higher doses, though. In conclusion, anisomycin is a potent and selective in vitro inhibitor of DENV and ZIKV that impairs a post-entry step of viral replication; and a low-dose anisomycin treatment may provide some minimal benefit in a mouse model.

Montelukast, an Anti-asthmatic Drug, Inhibits Zika Virus Infection by Disrupting Viral Integrity

The association of Zika virus (ZIKV) infection and severe complications including neurological sequelae especially fetal microcephaly has aroused global attentions since its outbreak in 2015. Currently, there are no vaccines or therapeutic drugs clinically approved for treatments of ZIKV infection, however. And the drugs used for treating ZIKV in pregnant women require a higher safety profile. Here, we identified an anti-asthmatic drug, montelukast, which is of safety profile for pregnant women and exhibited antiviral efficacy against ZIKV infection in vitro and in vivo. And we showed that montelukast could disrupt the integrity of the virions to release the viral genomic RNA, hence irreversibly inhibiting viral infectivity. In consideration of the neuro-protective activity that montelukast possessed, which was previously reported, it is promising that montelukast could be used for patients with ZIKV infection, particularly for pregnant women.

Antimicrobial lead compounds from marine plants

Marine environment is a home to a very wide diversity of flora and fauna, which includes an array of genetically diverse coastline and under seawater plant species, animal species, microbial species, their habitats, ecosystems, and supporting ecological processes. The Earth is home to an estimated 10 million species, of which a large chunk belongs to marine environment. Marine plants are a store house of a variety of antimicrobial compounds like classes of marine flavonoids—flavones and flavonols, terpenoids, alkaloids, peptides, carbohydrates, fatty acids, polyketides, polysaccharides, phenolic compounds, and steroids. Lot of research today is directed toward marine species, which have proved to be a potent source of structurally widely diverse and yet highly bioactive secondary metabolites. Varied species of phylum Porifera, algae including diatoms, Chlorophyta, Euglenophyta, Dinoflagellata, Chrysophyta, cyanobacteria, Rhodophyta, and Phaeophyta, bacteria, fungi, and weeds have been exploited by mankind for their inherent indigenous biological antimicrobial compounds, produced under the extreme stressful underwater conditions of temperature, atmospheric pressure, light, and nutrition. The present study aims at presenting a brief review of bioactive marine compounds possessing antimicrobial potency.

Antiviral bioactivity of renewable polysaccharides against Varicella Zoster

Although several effective treatments exist against Varicella zoster virus (VZV), resistant strains have emerged and the treatment is usually not definite and may have various undesired side effects. Thus, alternative treatment options are necessary. Here we studied the inhibitory effects of natural polysaccharides (PSs) obtained from renewable sources, varied by their structure and charge, on VZV infection in vitro, using a plaque assay. In terms of selectivity indices, almost all the tested PSs were very active; in the order of λ > ἰ > G > κ > P against VZV compared to Acyclovir as a reference drug and exhibited dose-dependent behavior. Our results, which showed a strong inhibition of VZV infection when the cells were treated with ἰ only at the time of infection or only post infection may indicate a multistep inhibitory effect. It seems that ἰ may block different stages of the virus replication cycle including early steps such as absorption and penetration to the host cells and also late steps after the penetration into the host cells. These results are part of an on-going research that highlights the PSs as potential novel nontoxic candidates that can be used against VZV, and contributes to the elucidation of their mode of action.