Germline rare variants of lectin pathway genes predispose to asymptomatic SARS-CoV-2 infection in elderly individuals

Background/Objectives: Emerging evidence suggests that complement system infection-dependent hyperactivation may worsen COVID-19 outcome. We investigated the role of predicted high impact variants -referred as Qualifying Variants (QVs) -of complement system genes in predisposing asymptomatic COVID-19 in elderly individuals, known to be more susceptible to severe disease. Method(s): Exploiting Whole-Exome Sequencing (WES) data and 56 complement system genes, we performed a gene-based collapsing test between 164 asymptomatic subjects (age >= 60 y.o.) and 56,885 European individuals from the gnomAD database. We replicated this test comparing the same asymptomatic individuals with 147 hospitalized COVID-19 patients. Result(s): We found an enrichment of QVs in three genes (MASP1, COLEC10 and COLEC11), which belong to the lectin pathway, in the asymptomatic cohort. Moreover, individuals with QVs showed lower serum levels of Masp1 and of prothrombin activity compared to controls while no differences were observed for CH50 and AH50 levels that measure the activity of classical and alternative complement pathways, respectively. Finally, integrative analyses of genome-wide association study and expression quantitative loci traits data showed a correlation between polymorphisms associated with asymptomatic COVID-19 and decreased expression of MASP1, COLEC11 and COLEC10 genes in lung tissue. Conclusion(s): This study suggests that rare genetic variants can protect from severe COVID-19 by mitigating the activation of lectin pathway and prothrombin activity.

Association between mannose binding lectin gene polymorphisms and clinical severity of COVID-19 in children.

BACKGROUND: Mannose-binding lectin (MBL) is a member of innate immunity and acts with MASP (MBL-associated serine protease) to activate the lectin pathway of the complement system. MBL gene polymorphisms are associated with susceptibility to infectious diseases. This study investigated whether MBL2 genotype, serum MBL levels, and serum MASP-2 levels affect the course of SARS-CoV-2 infection. METHODS AND RESULTS: Pediatric patients diagnosed with COVID-19 by positive real-time polymerase chain reaction (PCR) were included in the study. Single nucleotide polymorphisms in the promoter and exon 1 in the MBL2 gene (rs11003125, rs7096206, rs1800450, rs1800451, rs5030737) were identified by a PCR and restriction fragment length polymorphisms analysis. Serum MBL and MASP-2 levels were measured by ELISA. COVID-19 patients were divided into asymptomatic and symptomatic. Variables were compared between these two groups. A total of 100 children were included in the study. The mean age of the patients was 130 ± 67.2 months. Of the patients, 68 (68%) were symptomatic, and 32 (32%) were asymptomatic. The polymorphisms in the - 221nt and - 550nt promoter regions did not differ between groups (p > 0.05). All codon 52 and codon 57 genotypes were determined as wild-type AA. AB genotypes were found 45.6% in symptomatic patients while 23.5% in asymptomatics. Moreover, BB genotype was detected 9.4% in symptomatic and 6.3% in asymptomatic patients (p < 0.001). B allele was more frequent in symptomatic patients (46.3%) compared to asymptomatic patients (10.9%). (p < 0.001). Serum MBL and MASP-2 levels did not differ statistically between the groups (p = 0.295, p = 0.073). CONCLUSION: These findings suggest that codon 54 polymorphism in the MBL2 gene exon-1 region can be associated with the symptomatic course of COVID-19.

Capture and neutralization of SARS-CoV-2 and influenza virus by algae-derived lectins with high-mannose and core fucose specificities.

We first investigated the interactions between several algae-derived lectins and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). We created lectin columns using high-mannose (HM)-type glycan-specific lectins OAA and KAA-1 or core fucose-specific lectin hypninA-2 and conducted binding experiments with SARS-CoV-2. The results showed that these lectins were capable of binding to the virus. Furthermore, when examining the neutralization ability of nine different lectins, it was found that KAA-1, ESA-2, and hypninA-2 were effective in neutralizing SARS-CoV-2. In competitive inhibition experiments with glycoproteins, neutralization was confirmed to occur through HM-type or core fucose-type glycans. However, neutralization was not observed with other lectins, such as OAA. This trend of KAA-1 and ESA-2 having the neutralizing ability and OAA not having it was also similar to influenza viruses. Electron microscopy observations revealed that KAA-1 and hypninA-2 strongly aggregated SARS-CoV-2 particles, while OAA showed a low degree of aggregation. It is believed that the neutralization of SARS-CoV-2 involves multiple factors, such as glycan attachment sites on the S protein, the size of lectins, and their propensity to aggregate, which cause inhibition of receptor binding or aggregation of virus particles. This study demonstrated that several algae-derived lectins could neutralize SARS-CoV-2 and that lectin columns can effectively recover and concentrate the virus.

SIGLEC-9 RESTRAINS ANTIBODY-DEPENDENT NK CELL CYTOTOXICITY AGAINST SARS-CoV-2

Background: SARS CoV 2 infection alters the immunological profiles of natural killer (NK) cells. However, whether NK anti-viral functions (direct cytotoxicity and/or antibody-dependent cell cytotoxicity (ADCC)) are impaired during severe COVID-19 and what host factors modulate these functions remain unclear. Method(s): Using functional assays, we examined the ability of NK cells from SARS-CoV-2 negative controls (n=12), mild COVID-19 patients (n=26), and hospitalized COVID-19 patients (n=41) to elicit direct cytotoxicity and ADCC [NK degranulation by flow] against cells expressing SARS-CoV-2 antigens. SARS-CoV- 2 N antigen plasma load was measured using an ultra-sensitive Simoa assay. We also phenotypically characterized the baseline expression of NK activating (CD16 and NKG2C), maturation (CD57), and inhibitory (NKG2A and the glyco-immune negative checkpoint Siglec-9) by flow cytometry. Finally, an anti-Siglec-9 blocking antibody was used to examine the impact of Siglec-9 expression on anti-SARS-CoV-2-specific ADCC [degranulation and target cell lysis]. Result(s): NK cells from hospitalized COVID-19 patients degranulate less against SARS-CoV-2-antigen-expressing cells (in direct cytolytic and ADCC assays) than did cells from mild COVID-19 patients or negative controls (Fig. 1A). The lower NK degranulation was associated with higher plasma levels of SARS-CoV-2 N-antigen (P<=0.02). Phenotypic and functional analyses showed that NK cells expressing Siglec-9 elicited higher ADCC than Siglec-9- NK cells (P<0.05;Fig. 1B). Consistently, Siglec-9+ NK cells expressed an activated and mature phenotype with higher expression of CD16, CD57, and NKG2C, and lower expression of NKG2A, than Siglec-9- NK cells (P<=0.03). These data are consistent with the concept that the NK cell subpopulation expressing Siglec-9 is highly activated and cytotoxic. However, the Siglec-9 molecule itself is an inhibitory receptor that restrains NK cytotoxicity during cancer and other infections. Indeed, blocking Siglec-9 significantly enhanced the ADCC-mediated NK degranulation and lysis of SARS-CoV-2-antigen-positive target cells (P<=0.05;Fig. 1C). Conclusion(s): These data support a model (Fig. 1D) in which the Siglec-9+ CD56dim NK subpopulation is cytotoxic even while being restrained by the inhibitory effects of Siglec-9. However, alleviating the Siglec-9-mediated restriction on NK cytotoxicity can further improve NK immune surveillance and presents an opportunity to develop novel immunotherapeutic tools against SARS-CoV-2 infected cells. (Figure Presented).

Sars-Cov-2 Vaccine from Infected Plant Attenuated Virus Using Acer Cincinatum (Vine Maple)

Purpose of study Proposal for an oral (or if required, parenteral) COVID-19 vaccination based upon this described technology. Investigational theory under study for the past 9 months of COVID-19 growing season. Coronavirus can attack and infect plant species. It was found that SARS-CoV-2 can infect various plant species. Others have found plants, for example tobacco as a good growth medium for Coronavirus and SARS-CoV-2. This current study has found various plants species infected with SARS-CoV-2 by rPCR. As the plants were located beside a well used hiking trail for humans, and were infected along the trail including various species with SARS-CoV-2, hypothesized that human airborne contact had caused infection in the bordering plants. Humans were observed to be coughing while walking on the trail, and were not wearing masks. The plant leaves developed small circular colonies of the virus, which became self-limited at several millimeters in diameter. All of the plants were clear of these lesions before the COVID-19 Pandemic. The plants 'immune' system produced antiviral agents, including lectins which limited the growth of the colonies and prevent death of the leaf and whole plant. The fungal cultures of the 'spots' were negative. The rPCR of all spots tested in the present series was positive for SARS-CoV-2. Hypothesis, that self-augmentation of the virus occurred by the natural culturing in plant leaves that produce antiviral agents as part of their 'immune system.' Hypothesis, a symbiotic type relationship developed between the plant using its chemical immune system, and the virus allowed to replicate in an augmented fashion to allow both the virus and the host to survive and grow. As the top candidates for the oral vaccine are nontoxic, hypothesis involves the maceration of the infected leaves, mixing with a nontoxic adjuvant and flavoring to promote assimilation and palatability, with the proposed route of entry being mastication, thus exposing the oral-nasal mucosa to the vaccine, with the probable best of immunity to usual exposure to the SARS-CoV-2 virus, that is the oral-nasal mucosal and upper airway route. As many types of animals are now infected with SARS-CoV-2, it is further hypothesized that this oral vaccine could also be mass produced to add to various animals by feedstock and oral route. Methods used Hypotheses formed through observations. Testing of observations by pPCR, viral cell culture, fungal culture, light and electron microscopy. Summary of results pPCR SARS-CoV-2 positive, cell culture 'lysis experiment' positive, EM and light microscopy positive, fungal culture negative. Conclusions TABLE OF HYPOTHESES AND STUDY RESULTS (HYPOTHETICAL, OBSERVED, PROVEN) 1. The first hypothesis that the virus is attenuated by the plant, using its innate chemical immune system. Similarly, Pasteur used chemical such as phenol to attenuate viruses for wome of the first successful vaccines. Observed. 2. Hypothesis, the plants 'immune' system produced antiviral agents, including lectins, flavonoids, and others, which limited the growth of the colonies and prevent death of the leaf and whole plant. Proven. 3. Hypothesis is that the nontoxic plants, such as Vine Maple sp.(Acer cincinatum), could be used to produce and oral plant attenuated vaccine. Hypothesis. 4. Hypothesis involves the maceration of the infected leaves, mixing with a nontoxic adjuvant and flavoring to promote assimilation and palatability, with the proposed route of entry being mastication, thus exposing the oral-nasal mucosa to the vaccine, with the probable best of immunity to usual exposure to the SARS-CoV-2 virus, that is the oral-nasal mucosa, upper airway. (Figure Presented).

SARS-CoV-2 infection alters the breast milk glycomic profile

Breast milk is generally accepted as the perfect source of nutrition for the health and development of infants. It also assists in infant innate and adaptive immunity through many proteins that are decorated with glycans. Examples of these glycoproteins include IgA, IgG, and innate immune lectins. Maternal diet and environmental exposure such as pathogens and pollutants affect human milk composition including its glycoprofile. Despite altered glycosylation can have a consequence on the nursing infant's health and immunity, the current knowledge is still emerging in this area of study. COVID-19 has gained attention in recent years by causing severe morbidity and mortality. Similar to other infectious diseases such as influenza, our lab recently revealed alterations in glycome of plasma and different tissue samples of COVID-19 infected patients. Inspired by these findings, we are interested in disclosing the effect of SARS-CoV-2 on glycosylation of breast milk proteins. Toward this, we performed a large-scale systematic study using our high-throughput lectin microarray analysis technology. We analyzed 132 control samples (breast milk collected pre- COVID) and breast milk from 78 COVID-19 infected mothers. Our data showed there is a 4-fold increase in -2,3 sialic acid on glycoproteins that is associated with SARS-CoV-2 infection in lactating mothers. Lectin pulldown experiments further testified to these findings. Given the significance of -2,3 sialic acid glycan signature in infectious diseases, our finding could provide valuable insight into therapeutic development.Copyright © 2023 The American Society for Biochemistry and Molecular Biology, Inc.

Acute angioedena attacks after COVID-19 disease or COVID-19 vaccination in a population afflicted with hereditary angioedema

Background: Few studies demonstrating the involvement of the complement system in COVID-19 pathogenesis have been published, suggesting its role in pulmonary symptoms and endothelial permeability, which is known to be crucial in the origin of Hereditary Angioedema (HAE).1 Post-morten tissue of COVID-19 patients reported depots of complement, activated by the lectin pathway, in type I and II alveolar epithelial cells.2 After this evidence and the link that infectious processes have as triggers of angioedema episodes, in patients with HAE, we propose to study the implication of both the infection and de doses of the COVID vaccine, in the appearance of episodes of angioedema in our population with a diagnos is of HAE. Method(s): Telemedicine interventions (telephone consultations) were carried out by trained Allergists from Hospital Universitario de Canarias, reaching out patients with a confirmed diagnosis of HEA by Skin Allergy Unit (SAU) within the local health district. Result(s): A total of 17 (11 females) were finally screened, and 2 (11.76%) passed a confirmed COVID-19 disease in January 2022 associating no acute attacks or need for rescue medication. Both subjects were fully vaccinated (3 doses-schedule) prior to the infection and suffered from a COVID-19 mild disease only. Only an individual dose of COVID-19 vaccination (Vaxzevria, Astra-Zeneca) -out of 40 overall given doses in 15 subjects and 3 different brands-was associated to an acute episode of abdominal swelling demanding immediate self-administered rescue therapy (icatibant) thus, preventing the patient from rushing to the Emergency Department. The subsequent 2 doses of the COVID-19 vaccination were safely scheduled in the same patient. Conclusion(s): In accordance with former reports4, only mild COVID-19 symptoms were associated in subjects with a confirmed diagnosis of HAE.

Transcriptome in Human Mycoses

Mycoses are infectious diseases caused by fungi, which incidence has increased in recent decades due to the increasing number of immunocompromised patients and improved diagnostic tests. As eukaryotes, fungi share many similarities with human cells, making it difficult to design drugs without side effects. Commercially available drugs act on a limited number of targets and have been reported fungal resistance to commonly used antifungal drugs. Therefore, elucidating the pathogenesis of fungal infections, the fungal strategies to overcome the hostile environment of the host, and the action of antifungal drugs is essential for developing new therapeutic approaches and diagnostic tests. Large-scale transcriptional analyses using microarrays and RNA sequencing (RNA-seq), combined with improvements in molecular biology techniques, have improved the study of fungal pathogenicity. Such techniques have provided insights into the infective process by identifying molecular strategies used by the host and pathogen during the course of human mycoses. This chapter will explore the latest discoveries regarding the transcriptome of major human fungal pathogens. Further we will highlight genes essential for host–pathogen interactions, immune response, invasion, infection, antifungal drug response, and resistance. Finally, we will discuss their importance to the discovery of new molecular targets for antifungal drugs. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2014, 2022.

Complement lectin pathway activation is associated with COVID-19 disease severity, independent of MBL2 genotype subgroups.

Introduction: While complement is a contributor to disease severity in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections, all three complement pathways might be activated by the virus. Lectin pathway activation occurs through different pattern recognition molecules, including mannan binding lectin (MBL), a protein shown to interact with SARS-CoV-2 proteins. However, the exact role of lectin pathway activation and its key pattern recognition molecule MBL in COVID-19 is still not fully understood. Methods: We therefore investigated activation of the lectin pathway in two independent cohorts of SARS-CoV-2 infected patients, while also analysing MBL protein levels and potential effects of the six major single nucleotide polymorphisms (SNPs) found in the MBL2 gene on COVID-19 severity and outcome. Results: We show that the lectin pathway is activated in acute COVID-19, indicated by the correlation between complement activation product levels of the MASP-1/C1-INH complex (p=0.0011) and C4d (p<0.0001) and COVID-19 severity. Despite this, genetic variations in MBL2 are not associated with susceptibility to SARS-CoV-2 infection or disease outcomes such as mortality and the development of Long COVID. Conclusion: In conclusion, activation of the MBL-LP only plays a minor role in COVID-19 pathogenesis, since no clinically meaningful, consistent associations with disease outcomes were noted.

Application of urinary proteomics for biomarker discovery in respiratory diseases

Background: To search for molecular biomarkers of pulmonary pathologies using non-invasive samples, such as urine, is of high clinical relevance. However, there are almost no proteomic studies using urine applied to respiratory diseases. Aim(s): To develop a biomarker discovery strategy using non-targeted proteomics in urine with applicability to different pulmonary diseases. Method(s): Urine samples were centrifuged and DTT treated to decrease uromodulin (THP). Low-THP samples were concentrated (ultrafiltration), ultracentrifugated, and exosome free urine was analysed using LC-MS/MS. GO terms/Pathway analyses were performed using STRING database. Result(s): Urine proteome (765 proteins) was enriched (FDR < 0.05) in proteins from different tissues, including respiratory system (N = 124), lung (N = 107), and immune system (N = 88). We detected an enrichment of relevant pathways for respiratory diseases, including several innate (e.g., TLR and NFkB pathways, complement system), and adaptive (e.g., interleukin signalling) immune system pathways. Some of these proteins have been previously studied in respiratory system disease (e.g., MPO, NAPSA, CHL1, FREM2, PLG), lower respiratory tract disease (e.g., NCAM1, MTOR, SERPINA1), viral infectious disease (e.g., ITIH4, CD209, CLEC4M, CD55), or specific pathologies such as coronavirus infection (e.g., ACE2, TMPRSS2), bronchiectasis (e.g., SAA1, SAA2, ELANE) or asthma (e.g., IGFALS, IGFBP7, HSPG2, DPP4, CD44, IL6R, MASP1). Conclusion(s): We have developed a protocol for the detection of proteomic biomarkers in urine. This proteome is enriched in proteins from the immune and respiratory systems, with a potential clinical and translational relevance.

Screening of Natural Antivirals Against the COVID-19 Pandemic-A Compilation of Updates

Coronavirus disease 2019 (COVID-19), named by WHO, is a real public health disaster of the third millennium. This highly contagious viral disease has infected the world population and is now a global pandemic. This acute respiratory distress syndrome (ARDS) has severe complica-tions like pneumonitis, respiratory failure, shock, multiorgan failure, and death. Well-defined FDA-approved synthetic is not yet available. Case management strategies like lockdown, use of masks and sanitizers, social distancing, and repurposing of antiviral drugs were initially undertaken to cope with this pandemic. Different broad-spectrum antiviral drugs are being repurposed as one of the treatment modalities. The global vaccination programme with the newly launched COVID-19 vac-cines, Covishield, covaxin, sputnik V, etc., is an ongoing process. Simultaneously, significant research is being carried out in search of natural antivirals and evaluating the potency of food bioac-tives to aid naturistic protection against the coronavirus. This mini-review has compiled the latest updates on the screening and evidence-based mechanistic evaluation of phytochemicals and food bioactives as non-pharmacological adjuvant aid in COVID pandemics.Copyright © 2023 Bentham Science Publishers.

Enveloped Viruses: Pathogenetic Targets for Cyanobacterial Lectins.

Lectins are a group of highly specific carbohydrate-binding proteins with a wide spectrum of action, involved in the so-called <<first line>> of body defense. These unique biomolecules show high specificity for various mono- and oligosaccharides, primarily for viral and bacterial glycoconjugates. Cyanobacteria lectins are effective against enveloped viruses and are an appealing alternative to existing synthetic drugs. Virtually complete absence of resistance formation in viruses to these compounds is known. The purpose of this review is to analyze, summarize, and discuss the results of experimental studies in vivo and in vitro, illustrating the mechanisms of action and antiviral effects of lectins obtained from cyanobacteria in relation to the most dangerous and socially significant viruses: SARS-Cov-2, HIV, Ebola viruses, influenza, and hepatitis C. In addition, the article outlines some of the challenges that must be overcome in order to obtain effective antiviral drugs in the future.Copyright © Team of Authors, 2022.

Enveloped Viruses: Pathogenetic Targets for Cyanobacterial Lectins.

Lectins are a group of highly specific carbohydrate-binding proteins with a wide spectrum of action, involved in the so-called <<first line>> of body defense. These unique biomolecules show high specificity for various mono- and oligosaccharides, primarily for viral and bacterial glycoconjugates. Cyanobacteria lectins are effective against enveloped viruses and are an appealing alternative to existing synthetic drugs. Virtually complete absence of resistance formation in viruses to these compounds is known. The purpose of this review is to analyze, summarize, and discuss the results of experimental studies in vivo and in vitro, illustrating the mechanisms of action and antiviral effects of lectins obtained from cyanobacteria in relation to the most dangerous and socially significant viruses: SARS-Cov-2, HIV, Ebola viruses, influenza, and hepatitis C. In addition, the article outlines some of the challenges that must be overcome in order to obtain effective antiviral drugs in the future.Copyright © Team of Authors, 2022.

Narsoplimab for severe transplant-associated thrombotic microangiopathy.

BACKGROUND: Transplantation-associated thrombotic microangiopathy (TA-TMA) is an endothelial injury syndrome linked to the overactivation of complement pathways. It manifests with microangiopathic hemolytic anemia, consumptive thrombocytopenia, and microvascular thrombosis leading to ischemic tissue injury. Mannose residues on fungi and viruses activate the mannose-binding lectin complement pathway, and hence activation of the lectin pathway could be one of the reasons for triggering TA-TMA. Narsoplimab, a human monoclonal antibody targeting MASP-2 is a potent inhibitor of the lectin pathway. We describe the transplant course of a pediatric patient who developed TA-TMA following Candida-triggered macrophage activation syndrome and was treated with Narsoplimab. The data collection was performed prospectively. CASE PRESENTATION: The six-year-old girl underwent a human leucocyte antigen (HLA) haploidentical hematopoietic stem cell transplant using post-transplant Cyclophosphamide for severe aplastic anemia. In the second week of the transplant, the patient developed macrophage activation syndrome necessitating treatment with steroids and intravenous immunoglobulin. Subsequently, USG abdomen and blood fungal PCR revealed the diagnosis of hepatosplenic candidiasis. Candida-triggered macrophage activation syndrome responded to antifungals, steroids, intravenous immunoglobulin, and alemtuzumab. However, the subsequent clinical course was complicated by thrombotic microangiopathy. The patient developed hypertension in the 2nd week, followed by high lactate dehydrogenase (1010 U/L), schistocytes (5 per hpf), low haptoglobin (< 5 mg/dl), thrombocytopenia, and anemia in the 3rd week. Ciclosporin was stopped, and the patient was treated with 10 days of defibrotide without response. The course was further complicated by the involvement of the gastrointestinal tract and kidneys. She had per rectal bleeding with frequent but low-volume stools, severe abdominal pain, and hypoalbuminemia with a rising urine protein:creatinine ratio. Narsoplimab was started in the 5th week of the transplant. A fall in lactate dehydrogenase was observed after starting Narsoplimab. This was followed by the resolution of gastrointestinal symptoms, proteinuria, and recovery of cytopenia. The second episode of TA-TMA occurred with parvoviraemia and was also successfully treated with Narsoplimab. CONCLUSION: Lectin pathway inhibition could be useful in treating the fatal complication of transplant-associated thrombotic microangiopathy.

Can circulating oxidative stress-related biomarkers be used as an early prognostic marker for COVID-19?

Background: Oxidative stress plays an important role in the pathogenesis of many diseases. This study aimed to investigate the relationship between nuclear factor kappa B (NF-κB) and oxidative stress and the severity of the disease in new COVID-19 patients, and, to compare the levels of NF-κB, oxidized LDL (oxLDL), and lectin-like oxidized-LDL receptor-1 (LOX-1) with oxygen saturation, which is an indicator of the severity parameters of the disease in COVID-19 patients. Methods: In this prospective study, 100 COVID-19 patients and 100 healthy subjects were selected. Results: LOX-1, NF-κB, and oxLDL were found to be higher in COVID-19 patients compared to the healthy subjects (p < 0.001 for all). According to the results of correlation analysis, it was found that there was no significant relationship between oxygen saturation and LOX-1, NF-κB and oxLDL parameters. There was significant relationship between oxLDL with LOX-1 and NF-κB in patients with COVID-19 disease. ROC analysis results of the highest discrimination power were oxLDL (AUC: 0.955, CI: 0.904-1.000; sensitivity: 77%, and specificity: 100%, for cutoff: 127.944 ng/l) indicating COVID-19. Conclusion: Oxidative stress plays an essential role in COVID-19. NF-κB, oxLDL, and LOX-1 seem to represent good markers in COVID-19. Our study also showed that oxLDL has the highest power in distinguishing patients with COVID-19 from the healthy subjects.

Cyanovirin-N binds to select SARS-CoV-2 spike oligosaccharides outside of the receptor binding domain and blocks infection by SARS-CoV-2.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an enveloped positive stranded RNA virus which has caused the recent deadly pandemic called COVID-19. The SARS-CoV-2 virion is coated with a heavily glycosylated Spike glycoprotein which is responsible for attachment and entry into target cells. One, as yet unexploited strategy for preventing SARS-CoV-2 infections, is the targeting of the glycans on Spike. Lectins are carbohydrate-binding proteins produced by plants, algae, and cyanobacteria. Some lectins can neutralize enveloped viruses displaying external glycoproteins, offering an alternative therapeutic approach for the prevention of infection with virulent ß-coronaviruses, such as SARS-CoV-2. Here we show that the cyanobacterial lectin cyanovirin-N (CV-N) can selectively target SARS-CoV-2 Spike oligosaccharides and inhibit SARS-CoV-2 infection in vitro and in vivo. CV-N neutralizes Delta and Omicron variants in vitro better than earlier circulating viral variants. CV-N binds selectively to Spike with a Kd as low as 15 nM and a stoichiometry of 2 CV-N: 1 Spike but does not bind to the receptor binding domain (RBD). Further mapping of CV-N binding sites on Spike shows that select high-mannose oligosaccharides in the S1 domain of Spike are targeted by CV-N. CV-N also reduced viral loads in the nares and lungs in vivo to protect hamsters against a lethal viral challenge. In summary, we present an anti-coronavirus agent that works by an unexploited mechanism and prevents infection by a broad range of SARS-CoV-2 strains.

Plant lectins as versatile tools to fight coronavirus outbreaks.

The S protein forming the homotrimeric spikes of pathogenic beta-coronaviruses, such as MERS-CoV, SARS-CoV and SARS-CoV-2, is a highly glycosylated protein containing mainly N-glycans of the complex and high-mannose type, as well as O-glycans. Similarly, the host cell receptors DPP4 for MERS-CoV and ACE2 for SARS-CoV and SARS-CoV-2, also represent N- and O-glycosylated proteins. All these glycoproteins share common glycosylation patterns, suggesting that plant lectins with different carbohydrate-binding specificities could be used as carbohydrate-binding agents for the spikes and their receptors, to combat COVID19 pandemics. The binding of plant lectins to the spikes and their receptors could mask the non-glycosylated receptor binding domain of the virus and the corresponding region of the receptor, thus preventing a proper interaction of the spike proteins with their receptors. In this review, we analyze (1) the ability of plant lectins to interact with the N- and O-glycans present on the spike proteins and their receptors, (2) the in vitro and in vivo anti-COVID19 activity already reported for plant lectins and, (3) the possible ways for delivery of lectins to block the spikes and/or their receptors.

Enveloped Viruses: Pathogenetic Targets for Cyanobacterial Lectins

Lectins are a group of highly specific carbohydrate-binding proteins with a wide spectrum of action, involved in the so-called «first line» of body defense. These unique biomolecules show high specificity for various mono- and oligosaccharides, primarily for viral and bacterial glycoconjugates. Cyanobacteria lectins are effective against enveloped viruses and are an appealing alternative to existing synthetic drugs. Virtually complete absence of resistance formation in viruses to these compounds is known. The purpose of this review is to analyze, summarize, and discuss the results of experimental studies in vivo and in vitro, illustrating the mechanisms of action and antiviral effects of lectins obtained from cyanobacteria in relation to the most dangerous and socially significant viruses: SARS-Cov-2, HIV, Ebola viruses, influenza, and hepatitis C. In addition, the article outlines some of the challenges that must be overcome in order to obtain effective antiviral drugs in the future.