Effects of structural modification of calcium spirulan, a sulfated polysaccharide from Spirulina platensis, on antiviral activity

Cyanobacterial and microalgae polymers: antiviral activity and applications

At the end of 2019, the world witnessed the beginning of the COVID-19 pandemic. As an aggressive viral infection, the entire world remained attentive to new discoveries about the SARS-CoV-2 virus and its effects in the human body. The search for new antivirals capable of preventing and/or controlling the infection became one of the main goals of research during this time. New biocompounds from marine sources, especially microalgae and cyanobacteria, with pharmacological benefits, such as anticoagulant, anti-inflammatory and antiviral attracted particular interest. Polysaccharides (PS) and extracellular polymeric substances (EPS), especially those containing sulfated groups in their structure, have potential antiviral activity against several types of viruses including HIV-1, herpes simplex virus type 1, and SARS-CoV-2. We review the main characteristics of PS and EPS with antiviral activity, the mechanisms of action, and the different extraction methodologies from microalgae and cyanobacteria biomass.

Characterization of C-phycocyanin antioxidant, anti-inflammatory, anti-tumour, and anti-HCoV-229E activities and encapsulation for implementation in an innovative functional yogurt

Functional bioactive ingredients isolated from microalgae as sustainable sources have become a new subject of pharmacology and functional foods. Thus, the work aims to produce crude phycocyanin (C-PC), define it, and investigate its pharmacological effects before warping it in a nanophytosome. Subsequently, the physicochemical properties of nanoparticles were evaluated. Both free and nanophytosomes of C-PC were incorporated into cow milk fermented with the probiotic Lactobacillus rhamnosus KU985435 to make functional yoghurt and the stability of C-PC of both phytosomes was assessed. The amino acid content of C-PC revealed the presence of eight of nine essential amino acids and eight of eleven non-essential amino acids. C-PC has a medium molecular weight (82.992 kDa). Some pharmacological effects like reducing inflammation (98.76 % ± 0.065), fighting free radicals (99.12 % ± 0.027), and being able to inhibit the human coronavirus 229 E with a selective index of 27.9 were observed. The maximum viral inhibitory activity was detected during the adsorption stage. Anti-human liver and colon carcinomas that exceeded Doxorubicin with very low cytotoxicity against normal cell lines were detected. C-PC is an unstable protein that could be degraded in the yoghurt during storage. Therefore, phytosome encapsulation can effectively stabilize C-PC (particle size 44.50 ± 12 nm and zeta-potential -32.4 ± 5 mV) and protect it from the acidic environment of the yoghurt. The produced yoghurt showed the desired physicochemical and functional properties and overall acceptance. The results prove that C-PC from spirulina algae is a renewable source of dyes. The encapsulation process using phytosomes gave it high stability against environmental influences, and therefore, it can be applied in the food and pharmaceutical industries in the future.

Polysaccharides derived from Spirulina platensis inhibited Singapore grouper iridovirus by impeding the entry of viral particles

Attributable to the rapid dissemination and high lethality of Singapore grouper iridovirus (SGIV), it has caused significant economic losses for marine fish aquaculture in China and Southeast Asian nations. Hence, there is an urgent need to find antiviral drugs that are both safe and effective. In this study, a novel heteropolysaccharide named Spirulina platensis polysaccharides (SPP) was purified and characterized from S. platensis. The molecular weight of SPP is 276 kDa and it mainly consists of Glc and Rha, followed by minor components such as Gal, Xyl, and Fuc. The backbone of SPP was determined to be →2) -β-Rhap-(1 → 4) -α-Fucp-(1 → [2) -α-Rhap-(1] 2[→6)-α-Glcp-(1] 4[→ 4) -α-Glcp-(1] 8[→ 4) -β-Glcp-(1]2→, with branches of β-Galp, α-Xylp and α-Glcp. SPP significantly inhibited SGIV-induced cytopathic effects (CPEs), viral gene replication and viral protein expression. The antiviral mechanism of SPP was associated with the disruption of SGIV entry to host cells. Furthermore, it was not observed that SPP made statistically significant impact on the expression of interferon-related cytokines. Our results offered novel insights into the potential utilization of spirulina polysaccharides for combating aquatic animal viruses.

The potential, challenges, and prospects of the genus Spirulina polysaccharides as future multipurpose biomacromolecules

Spirulina has been widely used worldwide as a food and medicinal ingredient for centuries. Polysaccharides are major bioactive constituents of Spirulina and are of interest because of their functional properties and unlimited application potential. However, the clinical translation and market industrialization of the polysaccharides from genus Spirulina (PGS) are retarded due to the lack of a further understanding of their isolation, bioactivities, structure-activity relationships (SARs), toxicity, and, most importantly, versatile applications. Herein, we provide an overview of the extraction, purification, and structural features of PGS; meanwhile, the advances in bioactivities, SARs, mechanisms of effects, and toxicity are discussed and summarized. Furthermore, the applications, potential developments, and future research directions are scrutinized and highlighted. This review may help fill the knowledge gap between theoretical insights and practical applications and guide future research and industrial application of PGS.

Evaluating the effect of Spirulina platensis on the immune response of broiler chickens to various vaccines and virulent Newcastle disease virus challenge

This study investigated the efficacy of co-administration of Spirulina platensis (SP) with vaccines on the immune response to Avian influenza (AI), Infectious bronchitis (IB), and Newcastle disease (ND), along with I/M challenging by virulent ND virus (vNDV) genotype VII. 126 one-day-old broiler chicks were allocated into six groups (21 birds/group with three replicates): G1: negative control; G2: positive control; G3: vaccinated, non-SP-supplemented; G4: vaccinated, SP-supplemented (0.1%); G5: vaccinated, SP-supplemented (0.3%); and G6: vaccinated, SP-supplemented (0.5%). G2-6 were challenged with a velogenic NDV genotype VII virus. Dietary SP administration prevented the ND-induced mortality compared to G2 (52.4%) and G3 (14.3%), in addition to alleviating the clinical disease. G3-6 showed significant improvement in body weight loss% and FCR during two weeks post vNDV challenge (pc), and the overall FCR (2.64 ± 0.28, 1.56 ± 0.03, 1.60 ± 0.05, 1.53 ± 0.04, and 1.54 ± 0.03 for G2, 3, 4, 5 and 6, respectively) (P<0.05). On the challenging day, the ND-HI titer (log2) of G3 (5.44 ± 0.24) was numerically higher than G6 (4.20 ± 0.55) and lower than G4 (6.10 ± 0.34) and G5 (6.00 ± 0.28). On the 10th day pc, ND-HI titer in G4-6 was numerically lower in a dose-dependent manner than that of G3, suggesting an antiviral efficacy of SP. G4-6 had lower viral shedding titer than G2 and G3 (P<0.05). In G3-6, viral shedding was reduced by 15, 27, 24, and 33.6%, respectively. In addition, the histopathological lesions in the trachea, lung, and spleen were severe in G2, moderately reduced in G3, and more relieved in G4-6. At three weeks after vaccination, the HI antibody titer of AIH5 was significantly higher after SP administration, especially at the 0.3% level, compared to the vaccine alone (P<0.05), demonstrating an immune-stimulating effect. In conclusion, dietary administration of SP, particularly a dose of 0.3%, for vaccinated chickens against NDV exerted an antiinflammatory and antiviral effects by preventing deaths, alleviating clinical disease and weight loss, and decreasing viral shedding post heterologous NDV challenge.

Cyanometabolites: molecules with immense antiviral potential

Cyanometabolites are active compounds derived from cyanobacteria that include small low molecular weight peptides, oligosaccharides, lectins, phenols, fatty acids, and alkaloids. Some of these compounds may pose a threat to human and environment. However, majority of them are known to have various health benefits with antiviral properties against pathogenic viruses including Human immunodeficiency virus (HIV), Ebola virus (EBOV), Herpes simplex virus (HSV), Influenza A virus (IAV) etc. Cyanometabolites classified as lectins include scytovirin (SVN), Oscillatoria agardhii agglutinin (OAAH), cyanovirin-N (CV-N), Microcystis viridis lectin (MVL), and microvirin (MVN) also possess a potent antiviral activity against viral diseases with unique properties to recognize different viral epitopes. Studies showed that a small linear peptide, microginin FR1, isolated from a water bloom of Microcystis species, inhibits angiotensin-converting enzyme (ACE), making it useful for the treatment of coronavirus disease 2019 (COVID-19). Our review provides an overview of the antiviral properties of cyanobacteria from the late 90s till now and emphasizes the significance of their metabolites in combating viral diseases, particularly severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has received limited attention in previous publications. The enormous medicinal potential of cyanobacteria is also emphasized in this review, which justifies their use as a dietary supplement to fend off pandemics in future.

Polysaccharides from Spirulina platensis: Extraction methods, structural features and bioactivities diversity

Spirulina platensis, a well-known blue-green microalga cultivated and consumed in China and United States, is traditionally used as a food supplement and medical ingredient. Increasing evidence has confirmed that the Spirulina platensis polysaccharides (SPPs) are vital and representative pharmacologically active biomacromolecules and exhibit multiple health-promoting activities both in vivo and in vitro, such as those of anti-cancer, anti-oxidant, immunomodulatory, hypolipidemic and hypoglycemic, anti-thrombotic, anti-viral, regulation of the gut microbiota properties and other biological activity. The purpose of this review aims to comprehensively and systematically outline the extraction and purification methods, structural features, biological activities, underlying mechanisms, and toxicities of SPPs to support their potential utilization value in pharmaceuticals fields and functional foods. The structural and activities relationship of SPPs is also discussed. Besides, new valuable insights for future research with SPPs have also been proposed in the important areas of structural characterization and pharmacological activities.

A review of microbial-environmental interactions recorded in Proterozoic carbonate-hosted chert

The record of life during the Proterozoic is preserved by several different lithologies, but two in particular are linked both spatially and temporally: chert and carbonate. These lithologies capture a snapshot of dominantly peritidal environments during the Proterozoic. Early diagenetic chert preserves some of the most exceptional Proterozoic biosignatures in the form of microbial body fossils and mat textures. This fossiliferous and kerogenous chert formed in shallow marine environments, where chert nodules, layers, and lenses are often surrounded by and encased within carbonate deposits that themselves often contain kerogen and evidence of former microbial mats. Here, we review the record of biosignatures preserved in peritidal Proterozoic chert and chert-hosting carbonate and discuss this record in the context of experimental and environmental studies that have begun to shed light on the roles that microbes and organic compounds may have played in the formation of these deposits. Insights gained from these studies suggest temporal trends in microbial-environmental interactions and place new constraints on past environmental conditions, such as the concentration of silica in Proterozoic seawater, interactions among organic compounds and cations in seawater, and the influence of microbial physiology and biochemistry on selective preservation by silicification.

Integration of Arthrospira platensis (spirulina) into the brewing process to develop new beers with unique sensory properties

Microalgae, and particularly the cyanobacterium Arthrospira platensis (spirulina), have attracted much attention due to their wide range of uses. The potential use of spirulina in food is mainly driven by its high content of macro and micronutrients including proteins, γ-linolenic acid, sulfated polysaccharides, minerals, vitamins, and the natural pigment phycocyanin. Despite these potential benefits, spirulina is still not widely used in the food industry due to numerous technological challenges during manufacturing or specific sensory issues in the final product. This research deals with the feasibility of integrating spirulina into the brewing process to create a tasty beer with high consumer acceptance. In the novel recipes, 5% (w/w) of the malt was replaced by spirulina powder. The first part of the study investigated inclusion at different time points throughout manufacturing of a reference beer style (mild pale ale). Compared to the control, alcoholic fermentation was slightly influenced by cyanobacterial biomass but resulted in a beer with a typical beer-like character. Sensory evaluations including a simple descriptive test, a popularity analysis, and Just-About-Right-Questions, indicated a complex alteration in the sensory properties. This includes a dominant algal taste that disturbs the character of the pale ale beers but also a deep blue color of the beer, if spirulina was included during the wort cooling phase. Based on these results, another set of beers with a higher original extract concentration and increased hop dosages was produced. These beers had a high popularity (6.0 original TESTSCORE; 7.12 and 6.64 optimized TESTSCORE), and also exhibited a deep blue color due to the natural pigment phycocyanin from spirulina. Further, bitterness and algal taste was rated by most of the panelists to be “just right” and the simple descriptive test indicated “sweetness” as important attribute which was not expected for this hoppy beer style.

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.

Cyanobacterial metabolites as novel drug candidates in corona viral therapies: A review

Most of the medical and nonmedical research labs, all around the world, are racing against time to produce an effective vaccine or an antiviral medicine for coronavirus disease 2019 (COVID‐19). Conventional medicines and novel nano‐materials including chemical and herbal‐based compounds are all into positive trials toward coronaviruses and other pandemic infections. Among them, natural immune boosters have attracted physicians because of their longevity and reliability for fewer side effects. This is a review article with a detailed picture of an unexplored antiviral source with maximum potency in curing viral infections. Cyanobacteriae have been known for centuries and are rich in secondary metabolites of proteins, biopeptides, and polysaccharides for prominent antiviral action against chest infections. But detailed exploratory research is required to purify, scale‐up, and commercialize the pharmacologically active agents from these drug reserves.

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.

Evaluation of Microalgae Antiviral Activity and Their Bioactive Compounds

During the last year, science has been focusing on the research of antivirally active compounds overall after the SARS-CoV-2 pandemic, which caused a great amount of deaths and the downfall of the economy in 2020. Photosynthetic organisms such as microalgae are known to be a reservoir of bioactive secondary metabolites; this feature, coupled with the possibility of achieving very high biomass levels without excessive energetic expenses, make microalgae worthy of attention in the search for new molecules with antiviral effects. In this work, the antiviral effects of microalgae against some common human or animal viruses were considered, focusing our attention on some possible effects against SARS-CoV-2. We summed up the data from the literature on microalgae antiviral compounds, from the most common ones, such as lectins, polysaccharides and photosynthetic pigments, to the less known ones, such as unidentified proteins. We have discussed the effects of a microalgae-based genetic engineering approach against some viral diseases. We have illustrated the potential antiviral benefits of a diet enriched in microalgae.

Antiviral Cyanometabolites-A Review

Global processes, such as climate change, frequent and distant travelling and population growth, increase the risk of viral infection spread. Unfortunately, the number of effective and accessible medicines for the prevention and treatment of these infections is limited. Therefore, in recent years, efforts have been intensified to develop new antiviral medicines or vaccines. In this review article, the structure and activity of the most promising antiviral cyanobacterial products are presented. The antiviral cyanometabolites are mainly active against the human immunodeficiency virus (HIV) and other enveloped viruses such as herpes simplex virus (HSV), Ebola or the influenza viruses. The majority of the metabolites are classified as lectins, monomeric or dimeric proteins with unique amino acid sequences. They all show activity at the nanomolar range but differ in carbohydrate specificity and recognize a different epitope on high mannose oligosaccharides. The cyanobacterial lectins include cyanovirin-N (CV-N), scytovirin (SVN), microvirin (MVN), Microcystisviridis lectin (MVL), and Oscillatoria agardhii agglutinin (OAA). Cyanobacterial polysaccharides, peptides, and other metabolites also have potential to be used as antiviral drugs. The sulfated polysaccharide, calcium spirulan (CA-SP), inhibited infection by enveloped viruses, stimulated the immune system’s response, and showed antitumor activity. Microginins, the linear peptides, inhibit angiotensin-converting enzyme (ACE), therefore, their use in the treatment of COVID-19 patients with injury of the ACE2 expressing organs is considered. In addition, many cyanobacterial extracts were revealed to have antiviral activities, but the active agents have not been identified. This fact provides a good basis for further studies on the therapeutic potential of these microorganisms.

Oxy+ (arthrospira) and its medicinal importance: an appraisal

Oxy+ is a natural source of arthrospira found in nature, used as a dietary supplement and manufactured in Aruba for lifefactors. Arthrospira contains good quality of proteins, sulfated polysaccharides, γ-linoleic acid, along with an array of carotene and phytopigments, vitamins, and minerals which are reported to be antioxidant, immunomodulator, antihyperglycemic, antidyslipidemic, cardioprotective, hepatoprotective, antiviral, anticancerous, antihypertensive, anti-inflammatory, analgesic, neuroprotective and renoprotective activities. Several studies have shown arthrospira, and active ingredients of it revealed various pharmacological activities. It can be used for the management of various ailments such as diabetes, dyslipidemia, obesity, hypertension, cancer, arthritis, osteoarthritis, autoimmune disorders, etc. This review attempts to explore the hidden benefits of Oxy+ (arthrospira).

Oxy+ (arthrospira) and its medicinal importance: an appraisal

Oxy+ is a natural source of arthrospira found in nature, used as a dietary supplement and manufactured in Aruba for lifefactors. Arthrospira contains good quality of proteins, sulfated polysaccharides, γ-linoleic acid, along with an array of carotene and phytopigments, vitamins, and minerals which are reported to be antioxidant, immunomodulator, antihyperglycemic, antidyslipidemic, cardioprotective, hepatoprotective, antiviral, anticancerous, antihypertensive, anti-inflammatory, analgesic, neuroprotective and renoprotective activities. Several studies have shown arthrospira, and active ingredients of it revealed various pharmacological activities. It can be used for the management of various ailments such as diabetes, dyslipidemia, obesity, hypertension, cancer, arthritis, osteoarthritis, autoimmune disorders, etc. This review attempts to explore the hidden benefits of Oxy+ (arthrospira).

Advances in Antiviral Material Development

The rise in human pandemics demands prudent approaches in antiviral material development for disease prevention and treatment via effective protective equipment and therapeutic strategy. However, the current state of the antiviral materials research is predominantly aligned towards drug development and its related areas, catering to the field of pharmaceutical technology. This review distinguishes the research advances in terms of innovative materials exhibiting antiviral activities that take advantage of fast-developing nanotechnology and biopolymer technology. Essential concepts of antiviral principles and underlying mechanisms are illustrated, followed with detailed descriptions of novel antiviral materials including inorganic nanomaterials, organic nanomaterials and biopolymers. The biomedical applications of the antiviral materials are also elaborated based on the specific categorization. Challenges and future prospects are discussed to facilitate the research and development of protective solutions and curative treatments.

Polymers in the Medical Antiviral Front-Line

Antiviral polymers are part of a major campaign led by the scientific community in recent years. Facing this most demanding of campaigns, two main approaches have been undertaken by scientists. First, the classic approach involves the development of relatively small molecules having antiviral properties to serve as drugs. The other approach involves searching for polymers with antiviral properties to be used as prescription medications or viral spread prevention measures. This second approach took two distinct directions. The first, using polymers as antiviral drug-delivery systems, taking advantage of their biodegradable properties. The second, using polymers with antiviral properties for on-contact virus elimination, which will be the focus of this review. Anti-viral polymers are obtained by either the addition of small antiviral molecules (such as metal ions) to obtain ion-containing polymers with antiviral properties or the use of polymers composed of an organic backbone and electrically charged moieties like polyanions, such as carboxylate containing polymers, or polycations such as quaternary ammonium containing polymers. Other approaches include moieties hybridized by sulphates, carboxylic acids, or amines and/or combining repeating units with a similar chemical structure to common antiviral drugs. Furthermore, elevated temperatures appear to increase the anti-viral effect of ions and other functional moieties.

Biological Activities of Rhamnan Sulfate Extract from the Green Algae Monostroma nitidum (Hitoegusa)

Monostroma nitidum is a green single-cell layered algae that grows on the southwest coast of Japan. It is often used for salad ingredients, boiled tsukudani, soups, etc., due to its health benefits. M. nitidum is composed of many cell aggregates, and the various substances that fill the intercellular space are dietary fibers, vitamins, and minerals. Rhamnan sulfate (RS), a sulfated polysaccharide, is main the component of the fiber extracted from M. nitidum. Recently, some biological properties of RS have been demonstrated by in vitro and in vivo studies that probably protect human subjects from viruses and ameliorate vascular dysfunction caused by metabolic disorders, especially lifestyle-related diseases. In this review, we focus on the antithrombotic effects of RS and introduce its antiviral and other biological activities.

Systematic screening of viral entry inhibitors using surface plasmon resonance

Viral binding and entry into host cells for various viruses have been studied extensively, yielding a detailed understanding of the overall viral entry process. As cell entry is an essential and requisite process by which a virus initiates infection, it is an attractive target for therapeutic intervention. The advantages of targeting viral entry are an extracellular target site, relatively easy access for biological interventions, and lower toxicity. Several cell-based strategies and biophysical techniques have been used to screen compounds that block viral entry. These studies led to the discovery of inhibitors against HIV, HCV, influenza, Ebola, and RSV. In recent years, several compounds screened by fragment-based drug discovery have been approved as drugs or are in the final stages of clinical trials. Among fragment screening technologies, surface plasmon resonance has been widely used because it provides accurate information on binding kinetics, allows real-time monitoring of ligand-drug interactions, requires very small sample amounts to perform analyses, and requires no modifications to or labeling of ligands. This review focuses on surface plasmon resonance-based schemes for screening viral entry inhibitors.

Monocyte chemoattractant protein-1 polymorphism interaction with spirulina immunomodulatory effects in healthy Korean elderly: A 16 week, double-blind randomized clinical trial

BACKGROUND/OBJECTIVES

Spirulina is a known a functional food related to lipid profiles, immune functions, and antioxidant capacity. Circulating monocyte chemoattractant protein-1 (MCP-1) level is associated with inflammation markers. Single nucleotide polymorphism in the MCP-1 promoter region -2518 have been identified and shown to affect gene transcription. Gene variation may also impact functional food supplementary effects. The current study investigated the interaction of MCP-1 -2518 polymorphism with spirulina supplements on anti-inflammatory capacity in Korean elderly.

SUBJECTS/METHODS

After genotyping, healthy elderly subjects (n = 78) were included in a randomized, double blind, and placebo controlled study. Baseline characteristic, body composition, and dietary intake were measured twice (baseline vs. week 16). For 16 weeks, subjects consumed 8 g either spirulina or placebo daily. Plasma MCP-1, interleukin (IL) -2, IL-6, tumor necrosis factor (TNF)-α, complement (C) 3, immunoglobulin (Ig) G, and Ig A concentrations and lymphocyte proliferation rate (LPR) were analyzed as inflammatory markers.

RESULTS

In the placebo group with A/A genotype, MCP-1 level was significantly increased, but the spirulina group with A/A genotype was unchanged. IL-2 was significantly increased only in subjects with spirulina supplementation. TNF-α was significantly reduced in subjects with the G carrier. C3 was significantly increased in the placebo group, particularly when A/A increased more than G, but not when spirulina was ingested. LPR was significantly different only in subjects with A/A genotype; there was a significant increase in phytohemagglutinin and lipopolysaccharide induced LPR in the spirulina group.

CONCLUSION

In healthy Korean elderly, spirulina supplementation may influence different inflammatory markers by the MCP-1 genotype. These results may be useful for customized dietary guidelines to improve immune function in Koreans.

Well-tolerated Spirulina extract inhibits influenza virus replication and reduces virus-induced mortality

Influenza is one of the most common human respiratory diseases, and represents a serious public health concern. However, the high mutability of influenza viruses has hampered vaccine development, and resistant strains to existing anti-viral drugs have also emerged. Novel anti-influenza therapies are urgently needed, and in this study, we describe the anti-viral properties of a Spirulina (Arthrospira platensis) cold water extract. Anti-viral effects have previously been reported for extracts and specific substances derived from Spirulina, and here we show that this Spirulina cold water extract has low cellular toxicity, and is well-tolerated in animal models at one dose as high as 5,000 mg/kg, or 3,000 mg/kg/day for 14 successive days. Anti-flu efficacy studies revealed that the Spirulina extract inhibited viral plaque formation in a broad range of influenza viruses, including oseltamivir-resistant strains. Spirulina extract was found to act at an early stage of infection to reduce virus yields in cells and improve survival in influenza-infected mice, with inhibition of influenza hemagglutination identified as one of the mechanisms involved. Together, these results suggest that the cold water extract of Spirulina might serve as a safe and effective therapeutic agent to manage influenza outbreaks, and further clinical investigation may be warranted.

Impact of daily supplementation of Spirulina platensis on the immune system of naïve HIV-1 patients in Cameroon: a 12-months single blind, randomized, multicenter trial

BACKGROUND

Micronutrient deficiencies occur early in Human Immunodeficiency Virus (HIV) infections they have reverse effects on the nutritional status. The diet supplementation with a natural nutraceutical rich in proteins and micronutrient like Spirulina platensis, may be effective and efficient in delaying HIV disease progression by frequently reported improvement in immune response.

METHODS

A prospective single-blind, randomized, multicenter study conducted on 320 HIV-1 ARV-naïve participants for 12 months. Participants received either S. platensis supplementation and standard care or standard care and local balanced diet without S. platenis. Selected hematological and biochemical as well as CD4 count cells, viral load copies were assessed at three separate times.

RESULTS

Among the 169 ART-naïve participants enrolled in the study, the female was mostly represented (67.1%). The significant increase of CD4 count cells (596.32-614.92 cells count) and significant decrease of viral load levels (74.7 × 10(3)-30.87 × 10(3) copies/mL) of the patients who received a supplementation of S. platensis was found after 6 months of treatment. Haemoglobin level was also significantly higher in the same group while the fasting blood glucose concentration decreased after 12 months compared to control.

CONCLUSION

A daily supplementation with S. platensis to diet combined with a reasonable balanced diet has significantly increased the CD4 cells and reduced the viral load after 6 months. Further studies are recommended among a large specific group of people infected by the HIV in order to investigate the mechanisms involved on the effect of S. platensis on immune system.

Antioxidant Effect of Spirulina (Arthrospira) maxima on Chronic Inflammation Induced by Freund's Complete Adjuvant in Rats

One of the major mechanisms in the pathogenesis of chronic inflammation is the excessive production of reactive oxygen and reactive nitrogen species, and therefore, oxidative stress. Spirulina (Arthrospira) maxima has marked antioxidant activity in vivo and in vitro, as well as anti-inflammatory activity in certain experimental models, the latter activity being mediated probably by the antioxidant activity of this cyanobacterium. In the present study, chronic inflammation was induced through injection of Freund's complete adjuvant (CFA) in rats treated daily with Spirulina (Arthrospira) maxima for 2 weeks beginning on day 14. Joint diameter, body temperature, and motor capacity were assessed each week. On days 0 and 28, total and differential leukocyte counts and serum oxidative damage were determined, the latter by assessing lipid peroxidation and protein carbonyl content. At the end of the study, oxidative damage to joints was likewise evaluated. Results show that S. maxima favors increased mobility, as well as body temperature regulation, and a number of circulating leukocytes, lymphocytes, and monocytes in specimens with CFA-induced chronic inflammation and also protects against oxidative damage in joint tissue as well as serum. In conclusion, the protection afforded by S. maxima against development of chronic inflammation is due to its antioxidant activity.

Effects of Spirulina platensis supplementation on lipid profile in HIV-infected antiretroviral naïve patients in Yaounde-Cameroon: a randomized trial study

Background

Cardiovascular diseases (CVD) and metabolic alterations are among the majors public health concern that have been reported in people living with HIV infections. Factors contributing to cardio metabolic syndrome in HIV include body fat distribution, dyslipidemia, insulin resistance, cardiovascular dysfunction and inflammation. The aim of the study was to determine the effect of Spirulina platensis (Cyanobacteriaceae) supplementation versus local diet on lipid profile in HIV-infected antiretroviral-naive patients.

Methods

A prospective single-blind, randomized, multicentre study was conducted from February 2010 to December 2012. A total of 320 HIV antiretroviral-naïve patients were screened and 169 were recruited in this study. Patients were randomized and received either Spirulina supplementation combined with local diet (n = 82) or local diet only (n = 87). Age, weight, body mass index (BMI), lipid profile, CD4 count, and local food intake variables were assessed on three separate occasions (three, six and twelve months).

Results

An average age of the patients was 35.6 ± 9 years. The majority of participants were female 67.1%. Regarding the lipid profile, there is a significant increase in HDL-cholesterol and a significant decrease in total cholesterol, LDL-cholesterol and triglycerides in the group of patients who consumed Spirulina platensis. A change in the atherogenic index defined by the ratio CT/HDL-C substitutable by LDL-C/HDL-C and the TC/HDL decreased significantly from 10.83 at baseline to 2.22 after 12 months (p = 0.21 and p <0.0001) in the patients taking Spirulina.

Conclusions

Nutritional supplementation with Spirulina combined with a quantitative and qualitative balanced diet for at least six months can retard an exposition to lipid abnormalities in HIV–infected antiretroviral-naive patients. Further studies are recommended on a large group of people not infected with HIV and exposed to cardiovascular risk factors.

Anticoagulant activity of a sulfated polysaccharide from the green alga Arthrospira platensis

BACKGROUND

The polysaccharide of culture medium from Arthrospira platensis was extracted by ultrafiltration, partially characterized and assayed for anticoagulant activity.

METHODS

The crude polysaccharidic fraction was fractionated by anion exchange chromatography on DEAE-cellulose, subjected to acetate cellulose electrophoresis and characterized by physicochemical procedures. The anticoagulant effect of the ultrafiltrated polysaccharide was checked by several coagulation tests.

RESULTS

Anion exchange chromatography revealed in the whole ultrafiltrated polysaccharidic fraction the occurrence of a sulfated spirulan-like component designated PUF2. The average molecular weight of PUF2 was determined by size exclusion chromatography combined with multi-angle light scattering (SEC-MALS) and viscosimetry and was 199 kDa and the sulfate content was 20% weight/dry weight. The physicochemical characterization indicated the occurrence of rhamnose (49.7%), galacturonic and glucuronic acid (32% of total sugar). The anticoagulant effect of this sulfated polysaccharide was mainly due to the potentiation of thrombin inhibition by heparin cofactor II and was 4-times higher than that of the porcine dermatan sulfate whereas it had no effect on anti-Xa activity.

CONCLUSIONS

An ultrafiltrated sulfated polysaccharide, likely a calcium spirulan was obtained from the culture medium of A. platensis and showed an anticoagulant activity mediated by heparin cofactor II.

GENERAL SIGNIFICANCE

Old culture medium of A. platensis may represent an important source for the spirulan-like PUF2 which was endowed with potentially useful anticoagulant properties whereas its obtention by ultrafiltration may represent an extraction procedure of interest.

Focus on antivirally active sulfated polysaccharides: from structure-activity analysis to clinical evaluation

In recent years, many compounds having potent antiviral activity in cell culture have been detected and some of these compounds are currently undergoing either preclinical or clinical evaluation. Among these antiviral substances, naturally occurring sulfated polysaccharides and those from synthetic origin are noteworthy. Recently, several controversies over the molecular structures of sulfated polysaccharides, viral glycoproteins, and cell-surface receptors have been resolved, and many aspects of their antiviral activity have been elucidated. It has become clear that the antiviral properties of sulfated polysaccharides are not only a simple function of their charge density and chain length but also their detailed structural features. The in vivo efficacy of these compounds mostly corresponds to their ability to inhibit the attachment of the virion to the host cell surface although in some cases virucidal activity plays an additional role. This review summarizes experimental evidence indicating that sulfated polysaccharides might become increasingly important in drug development for the prevention of sexually transmitted diseases in the near future.

[Studies on evaluation of natural products for antiviral effects and their applications]

In the search for novel antiviral molecules from natural products, we have discovered various antiviral molecules with characteristic mechanisms of action. Scopadulciol (SDC), isolated from the tropical medicinal plant Scoparia dulcis L., showed stimulatory effects on the antiviral potency of acyclovir (ACV) or ganciclovir (GCV). This effect of SDC was exerted via the activation of viral thymidine kinase (HSV-1 TK) and, as a result, an increase in the cellular concentration of the active form of ACV/GCV, i.e., the triphosphate of ACV or GCV. On the basis of these experimental results, cancer gene therapy using the HSV-1 tk gene and ACV/GCV together with SDC was found to be effective in suppressing the growth of cancer cells in animals. Acidic polysaccharides such as calcium spirulan (Ca-SP) from Spirulina platensis, nostoflan from Nostoc flagelliforme, and a fucoidan from the sporophyll of Undaria pinnatifida (mekabu fucoidan) were also found to be potent inhibitors against several enveloped viruses. Their antiviral potency was dependent on molecular weight and content of the sulfate or carboxyl group as well as counterion species chelating with sulfate groups, indicating the importance of the three-dimensional structure of the molecules. In addition, unlike dextran sulfate, Ca-SP was shown to target not only viral absorption/penetration stages but also some replication stages of progeny viruses after penetration into cells. When mekabu fucoidan or nostoflan was administered with oseltamivir phosphate, their synergistic antiviral effects on influenza A virus were confirmed in vitro as well as in vivo.

Antiviral activity of Arthrospira-derived spirulan-like substances

Natural substances offer interesting pharmacological perspectives for antiviral drug development in regard to broad-spectrum antiviral properties and novel modes of action. In this study we analyzed polysaccharide fractions isolated from Arthrospira platensis. Fractions containing intracellular or extracellular spirulan-like molecules showed a pronounced antiviral activity in the absence of cytotoxic effects. Using specific assays for the quantification of viral replication in vitro, these substances exhibited strong inhibition of human cytomegalovirus, herpes simplex virus type 1, human herpesvirus type 6 and human immunodeficiency virus type 1, while only weak or no inhibition was noted for Epstein-Barr virus and influenza A virus. Considering herpesviruses, antiviral effects were most pronounced when the cells were preincubated with the substances prior to the addition of virus, indicating that antiviral action may be primarily targeted to virus entry. However, an inspection of the inhibition of human cytomegalovirus protein synthesis clearly demonstrated that intracellular steps also contributed to the antiviral effect. In the case of human immunodeficiency virus, inhibition occurred at a stage later than viral entry. Thus, spirulan-like substances possess a marked antiherpesviral and anti-HIVactivity based on different modes of action. Further development of these substances might yield novel candidates of broad-spectrum antiviral drugs.

Antiviral Activities of Polysaccharides from Natural Sources

The ever increasing resistance of human pathogens to current anti-infective agents is a serious medical problem, leading to the need to develop novel antibiotic prototype molecules. In the case of viruses, the search for antiviral agents involves additional difficulties, particularly due to the nature of the infectious viral agents. Thus, many compounds that may cause the death of viruses are also very likely to injure the host cell that harbours them. Natural products are increasingly appreciated as leads for drug discovery and development. Screening studies have been carried out in order to find antiviral agents from natural sources, and the occurrence of antiviral activity in extracts of plants, marine organisms and fungi is frequent. The evidence indicates that there may be numerous potentially useful antiviral phytochemicals in nature, waiting to be evaluated and exploited. In addition, other plants, not previously utilized medicinally, may also reveal antivirals. Among natural antiviral agents, recent investigations have reconsidered the interest of phyto-polysaccharides, which act as potent inhibitors of different viruses. This chapter will illustrate a variety of antiviral polysaccharides from natural sources since 1990, with the aim of making this matter more accessible to drug development

In vitro anti-herpetic activity of sulfated polysaccharide fractions from Caulerpa racemosa

A sulfated polysaccharide fraction was isolated from the hot water extract of the green alga Caulerpa racemosa and designated HWE. This polymer, which contained galactose, glucose, arabinose and xylose as the major component sugars, had [alpha](D)(30) + 46.2 degrees in water and contained 9% sulfate hemiester groups. Sugar linkage analysis indicates that HWE was branched and mainly contained 1,3- and 1,3,6-linked galactose, 1,3,4-linked arabinose, 1,4-linked glucose and terminal- and 1,4-linked xylose residues. Sulfation was deduced from infrared spectroscopy and methylation analysis to occur on O-6 of galactose and O-3 of arabinose. The native polysaccharide could be fractionated by size exclusion chromatography into two overlapping fractions and the major fraction has a hydrodynamic volume similar to that of 70 kDa dextran. HWE was a selective inhibitor of reference strains and TK(-) acyclovir-resistant strains of herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) in Vero cells, with antiviral effective concentration 50% (EC(50)) values in the range of 2.2-4.2 microg/ml and lacking cytotoxic effects. Furthermore, HWE did not exhibit anticoagulant properties at concentrations near the EC(50).

Sodium spirulan as a potent inhibitor of arterial smooth muscle cell proliferation in vitro

Sodium spirulan (Na-SP) is a sulfated polysaccharide with M(r) approximately 220,000 isolated from the blue-green alga Spirulina platensis. The polysaccharide consists of two types of disaccharide repeating units, O-hexuronosyl-rhamnose (aldobiuronic acid) and O-rhamnosyl-3-O-methylrhamnose (acofriose) with sulfate groups, other minor saccharides and sodium ion. Since vascular smooth muscle cell proliferation is a crucial event in the progression of atherosclerosis, we investigated the effect of Na-SP on the proliferation of bovine arterial smooth muscle cells in culture. It was found that Na-SP markedly inhibits the proliferation without nonspecific cell damage. Either replacement of sodium ion with calcium ion or depolymerization of the Na-SP molecule to M(r) approximately 14,700 maintained the inhibitory activity, however, removal of sodium ion or desulfation markedly reduced the activity. Heparin and heparan sulfate also inhibited vascular smooth muscle cell growth but their effect was weaker than that of Na-SP; dextran sulfate, chondroitin sulfate, dermatan sulfate and hyaluronan failed to inhibit the cell growth. The present data suggest that Na-SP is a potent inhibitor of arterial smooth muscle cell proliferation, and the inhibitory effect requires a certain minimum sequence of polysaccharide structure whose molecular conformation is maintained by sodium ion bound to sulfate group.

Mechanism of activation of heparin cofactor II by calcium spirulan

Calcium spirulan (Ca-SP), a novel sulfated polysaccharide, increases the rate of thrombin inhibition by heparin cofactor II (HCII) more than 1000-fold through a mechanism not requiring the amino-terminal acidic domain of HCII. Activation of HCII by Ca-SP was molecular-weight dependent. Furthermore, HD22, an aptamer that binds exosite II of thrombin, produced a concentration-dependent, 15-fold reduction at 5 microM in the rate of thrombin inhibition by HCII with Ca-SP, suggesting that Ca-SP interacts with exosite II of thrombin. Mutations of Lys173 to Leu (K173L) and Arg189 to Leu (R189L) in the HCII molecule resulted in large decreases in the rate of thrombin inhibition mediated by Ca-SP and in the NaCl concentration needed for elution from Ca-SP-Toyopearl. Mutations of Lys173 to Arg (K173R) and Arg189 to Lys (R189K) showed inhibition of thrombin similar to wild-type rHCII (wt-rHCII). These results indicate that Ca-SP binds to the positive charges of Lys173 and Arg189 on the HCII molecule. In the thrombin inhibitory process by HCII, Ca-SP appears to play as a template by binding to both thrombin and HCII.