Inhibitory effect of iota-carrageenan on porcine reproductive and respiratory syndrome virus in vitro

Global seaweed farming and processing in the past 20 years

Seaweed has emerged as one of the most promising resources due to its remarkable adaptability, short development period, and resource sustainability. It is an effective breakthrough to alleviate future resource crises. Algal resources have reached a high stage of growth in the past years due to the increased output and demand for seaweed worldwide. Several aspects global seaweed farming production and processing over the last 20 years are reviewed, such as the latest situation and approaches of seaweed farming. Research progress and production trend of various seaweed application are discussed. Besides, the challenges faced by seaweed farming and processing are also analyzed, and the related countermeasures are proposed, which can provide advice for seaweed farming and processing. The primary products, extraction and application, or waste utilization of seaweed would bring greater benefits with the continuous development and improvement of applications in various fields.

Graphical Abstract

A study protocol for a double-blind randomised placebo-controlled trial evaluating the efficacy of carrageenan nasal and throat spray for COVID-19 prophylaxis—ICE-COVID

Introduction

At present, vaccines form the only mode of prophylaxis against COVID-19. The time needed to achieve mass global vaccination and the emergence of new variants warrants continued research into other COVID-19 prevention strategies. The severity of COVID-19 infection is thought to be associated with the initial viral load, and for infection to occur, viruses including SARS-CoV-2 must first penetrate the respiratory mucus and attach to the host cell surface receptors. Carrageenan, a sulphated polysaccharide extracted from red edible seaweed, has shown efficacy against a wide range of viruses in clinical trials through the prevention of viral entry into respiratory host cells. Carrageenan has also demonstrated in vitro activity against SARS-CoV-2.

Methods and analysis

A single-centre, randomised, double-blinded, placebo-controlled phase III trial was designed. Participants randomised in a 1:1 allocation to either the treatment arm, verum Coldamaris plus (1.2 mg iota-carrageenan (Carragelose®), 0.4 mg kappa-carrageenan, 0.5% sodium chloride and purified water), or placebo arm, Coldamaris sine (0.5% sodium chloride) spray applied daily to their nose and throat for 8 weeks, while completing a daily symptom tracker questionnaire for a total of 10 weeks.

Primary outcome

Acquisition of COVID-19 infection as confirmed by a positive PCR swab taken at symptom onset or seroconversion during the study. Secondary outcomes include symptom type, severity and duration, subsequent familial/household COVID-19 infection and infection with non-COVID-19 upper respiratory tract infections. A within-trial economic evaluation will be undertaken, with effects expressed as quality-adjusted life years.

Discussion

This is a single-centre, phase III, double-blind, randomised placebo-controlled clinical trial to assess whether carrageenan nasal and throat spray reduces the risk of development and severity of COVID-19. If proven effective, the self-administered prophylactic spray would have wider utility for key workers and the general population.

Trial registration

NCT04590365; ClinicalTrials.gov NCT04590365. Registered on 19 October 2020.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06685-z.

Reappraising host cellular factors involved in attachment and entry to develop antiviral strategies against porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome (PRRS), caused by PRRS virus (PRRSV), is a highly contagious disease that brings tremendous economic losses to the global swine industry. As an intracellular obligate pathogen, PRRSV infects specific host cells to complete its replication cycle. PRRSV attachment to and entry into host cells are the first steps to initiate the replication cycle and involve multiple host cellular factors. In this review, we recapitulated recent advances on host cellular factors involved in PRRSV attachment and entry, and reappraised their functions in these two stages, which will deepen the understanding of PRRSV infection and provide insights to develop promising antiviral strategies against the virus.

Advances in the Prophylaxis of Respiratory Infections by the Nasal and the Oromucosal Route: Relevance to the Fight with the SARS-CoV-2 Pandemic

In this time of COVID-19 pandemic, the strategies for prevention of the infection are a primary concern. Looking more globally on the subject and acknowledging the high degree of misuse of protective face masks from the population, we focused this review on alternative pharmaceutical developments eligible for self-defense against respiratory infections. In particular, the attention herein is directed to the nasal and oromucosal formulations intended to boost the local immunity, neutralize or mechanically “trap” the pathogens at the site of entry (nose or mouth). The current work presents a critical review of the contemporary methods of immune- and chemoprophylaxis and their suitability and applicability in topical mucosal dosage forms for SARS-CoV-2 prophylaxis.

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.

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.

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.

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.

Application prospect of polysaccharides in the development of anti-novel coronavirus drugs and vaccines

Since the outbreak of the novel coronavirus disease COVID-19, caused by the SARS-CoV-2 virus, it has spread rapidly worldwide and poses a great threat to public health. This is the third serious coronavirus outbreak in <20 years, following SARS in 2002-2003 and MERS in 2012. So far, there are almost no specific clinically effective drugs and vaccines available for COVID-19. Polysaccharides with good safety, immune regulation and antiviral activity have broad application prospects in anti-virus, especially in anti-coronavirus applications. Here, we reviewed the antiviral mechanisms of some polysaccharides, such as glycosaminoglycans, marine polysaccharides, traditional Chinese medicine polysaccharides, and their application progress in anti-coronavirus. In particular, the application prospects of polysaccharide-based vaccine adjuvants, nanomaterials and drug delivery systems in the fight against novel coronavirus were also analyzed and summarized. Additionally, we speculate the possible mechanisms of polysaccharides anti-SARS-CoV-2, and propose the strategy of loading S or N protein from coronavirus onto polysaccharide capped gold nanoparticles vaccine for COVID-19 treatment. This review may provide a new approach for the development of COVID-19 therapeutic agents and vaccines.

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.

Iota-Carrageenan as an Antiviral Treatment for the Common Cold

Introduction:

The common cold syndrome of acute upper respiratory tract viral infection is the most common disease among mankind and is an extremely common illness in children. There is a great need for a safe and effective antiviral treatment with minimal side effects. The challenge in developing a treatment is the numerous and varied respiratory viruses that cause this common illness and the need for a treatment with good tolerability and safety.

Explanation:

All respiratory viruses must reach the cell surface by passing through respiratory fluid and mucus, and this common feature may allow for the development of antivirals that capture viruses during this transit.

This article discusses how large polyanionic molecules such as iota-carrageenan may trap positively charged respiratory viruses. Iota-carrageenan is a large polysaccharide molecule which is neither absorbed from the respiratory tract nor metabolised. It, therefore, does not have any pharmacological properties. Iota-carrageenan nasal spray has been shown to reduce the titres of respiratory viruses and to reduce the severity of symptoms in placebo-controlled clinical trials, including children and adults. The results of four clinical trials are presented.

Conclusion:

Iota-carrageenan is a good candidate as a safe and effective non-specific antiviral treatment for common cold, and more research is justified on polyanionic molecules like carrageenans as antivirals.