Human Cathelicidin Inhibits SARS-CoV-2 Infection: Killing Two Birds with One Stone

LL-37 Inhibits TMPRSS2-Mediated S2' Site Cleavage and SARS-CoV-2 Infection but Not Omicron Variants

Continual evolution of SARS-CoV-2 spike drives the emergence of Omicron variants that show increased spreading and immune evasion. Understanding how the variants orientate themselves towards host immune defence is crucial for controlling future pandemics. Herein, we demonstrate that human cathelicidin LL-37, a crucial component of innate immunity, predominantly binds to the S2 subunit of SARS-CoV-2 spike protein, occupying sites where TMPRSS2 typically binds. This binding impedes TMPRSS2-mediated priming at site S2' and subsequent membrane fusion processes. The mutation N764K within S2 subunit of Omicron variants reduces affinity for LL-37 significantly, thereby diminishing binding capacity and inhibitory effects on membrane fusion. Moreover, the early humoral immune response enhanced by LL-37 is observed in mice against SARS-CoV-2 spike but not Omicron BA.4/5 spike. These findings reveal the mechanism underlying interactions amongst LL-37, TMPRSS2 and SARS-CoV-2 and VOCs, and highlight the distinct mutation for Omicron variants to evade the fusion activity inhibition by host innate immunity.

Dodecapeptides derived from human cathelicidin with potent activity against carbapenem-resistant Acinetobacter baumannii

The increasing infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB) poses a serious threat to global public health. Antimicrobial peptides (AMPs) are alternatives to conventional antibiotics in combating superbugs. However, discovering AMPs with low synthesis costs and strong antibacterial effects against CRAB is challenging. In this study, we synthesized 28 dodecapeptides for bactericidal assessment by site mutation and all-hydrocarbon stapling on the basis of the antibacterial core of human cathelicidin. The linear derivative d12 (Q5RD9I-KR12) and the i, i + 4 stapled peptide d24, which was generated by substituting Val4 and Lys8 of d12 to staples, stood out among the candidates. These short AMPs efficiently bound to bacterial membrane and penetrated it in a lipid A-dependent manner, resulting in low minimal inhibitory concentrations to inactivate CRAB clinical isolates (2.5-20 μg/mL). The CRAB infection mouse models of irradiation-assisted local pulmonary infection and intra-abdominal sepsis revealed that treatment with d12 and d24 significantly eliminated CRAB in vivo and thereby increased mouse survival. Owing to its improved proteolytic resistance, d24 outperformed d12 in suppressing intra-abdominal CRAB infection. The excellent antibacterial effects, good biocompatibility, and facile synthesis make d12 and d24 promising candidates to curb CRAB infections in different application scenarios.

COVID-19 and our understanding of vitamin D and immune function

The interaction between vitamin D and the immune system is perhaps the most well recognised extraskeletal facet of vitamin D, encompassing early studies of therapy for TB and leprosy through to more recent links with autoimmune disease. However, the spotlight on vitamin D and immune function has been particularly intense in the last five years following the COVID-19 pandemic. This was due, in part, to the many association studies of vitamin D status and COVID-19 infection and disease prognosis, as well as the smaller number of clinical trials of vitamin D supplementation. However, a potential role for vitamin D in COVID-19 also stemmed from the basic biology of vitamin D that provides a plausible mechanistic rationale for beneficial effects of vitamin D for improved immune health in the setting of respiratory infection. The aim of this review is to summarise the different strands of mechanistic evidence supporting a beneficial effect of vitamin D in COVID-19, how this was modified during the pandemic itself, and the potential new aspects of vitamin D and immune function that are likely to arise in the near future. Key topics that feature in this review are: antibacterial versus antiviral innate immune responses to 1,25-dihydroxyvitamin D (1,25(OH)2D); the function of immune 1α-hydroxylase (CYP27B1) activity and metabolism of 25-hydroxyvitamin D (25(OH)D) beyond antigen-presenting cells; advances in immune cell target gene responses to 1,25-dihydroxyvitamin D (notably changes in metabolic profile). Whilst much of the interest during the COVID-19 era has focused on vitamin D and public health, the continued evolution of our understanding of how vitamin D interacts with different components of the immune system continues to support a beneficial role for vitamin D in immune health.

Antimicrobial peptides: from discovery to developmental applications

Antimicrobial resistance (AMR) has emerged as a significant crisis in global health. Due to their advantageous properties, antimicrobial peptides (AMPs) have garnered considerable attention as a potential alternative therapy to address the AMR crisis. These peptides might disrupt cell membranes or cell walls to exhibit antimicrobial activity, or modulate the immune response to promote recovery from diseases. In recent years, significant progress has been made in the research of AMPs, alongside the emergence of new challenges. This review first systematically summarizes and critically discusses recent advancements in understanding the characteristics and current landscapes of AMPs, as well as their regulatory mechanisms of action and practical applications, particularly those reported or approved within the last 5 years. Additionally, the principles, paths for their identification, and future research trends in AMPs are also analyzed following a discussion of the advantages and disadvantages of AMPs in comparison to conventional antibiotics. Unlike significant prior literature in this field, this report has summarized the latest major discovery methods for AMPs and, more importantly, emphasized their practical applications by supporting various viewpoints using selected examples of AMPs' applications in real-life scenarios. Besides, some emerging hot topics of AMPs, including those derived from gut microbiota and their potential synergistic effects in combating AMR, were profiled. All of these indicate the originality of the report and provide valuable references for future AMP discoveries and applications.

The Impact of Vitamin D in the Prevention of Influenza, COVID-19, and Dengue: A Review

Since its discovery, vitamin D (VD) has been known for its implications in maintaining bone homeostasis. However, in recent years it has been discovered that the vitamin D receptor is expressed on different cells of the immune system and that these cells can locally produce the active form of this molecule, calcitriol, strongly suggesting that this vitamin might play a key role in both branches of the immune system, innate and adaptive. Recent evidence has demonstrated that VD participates in the different protective phases of the immune system against invading microorganisms, including in the activation and production of antimicrobial peptides, in the inactivation of replication of infectious agents, in the prevention of the exposure of cellular receptors to microbial adhesion, and, more importantly, in the modulation of the inflammatory response. In recent years, the world has witnessed major outbreaks of an ancient infectious disease, dengue fever; the emergence of a pandemic caused by an unknown virus, SARS-CoV-2; and the resurgence of a common respiratory infection, influenza. Despite belonging to different viral families, the etiological agents of these infections present a common trait: their capacity to cause complications not only through their cytopathic effect on target tissues but also through the excessive inflammatory response produced by the human host against an infection. This review outlines the current understanding of the role that vitamin D plays in the prevention of the aforementioned diseases and in the development of their complications through its active participation as a major modulator of the immune response.

Marsupial cathelicidins: characterization, antimicrobial activity and evolution in this unique mammalian lineage

Introduction

Cathelicidins are a family of antimicrobial peptides well-known for their antimicrobial and immunomodulatory functions in eutherian mammals such as humans. However, cathelicidins in marsupials, the other major lineage of mammals, have received little attention despite lineage-specific gene expansions resulting in a large and diverse peptide repertoire.

Methods

We characterized cathelicidins across the marsupial family tree and investigated genomic organisation and evolutionary relationships amongst mammals. Ancestral sequence reconstruction was used to predict ancestral marsupial cathelicidins, which, alongside extant peptides, were synthesized and screened for antimicrobial activity.

Results

We identified 130 cathelicidin genes amongst 14 marsupial species representing 10 families, with gene expansions identified in all species. Cathelicidin genes were encoded in a highly syntenic region of the genome amongst all mammals, although the number of gene clusters differed amongst lineages (eutherians one, marsupials two, and monotremes three). 32 extant and ancestral marsupial cathelicidins displayed rapid, potent, and/or broad-spectrum antibacterial and antifungal activity. Phylogenetic analysis revealed that marsupial and monotreme cathelicidin repertoires may reflect both mammals and birds, as they encode non-classical cathelicidins found only in birds, as well as multiple copies of neutrophil granule protein and classic cathelicidins found only in eutherian mammals.

Conclusion

This study sheds light on the evolutionary history of mammalian cathelicidins and highlights the potential of wildlife for novel bioactive peptide discovery.

Peptides Corresponding to the Receptor-Binding Domain (RBD) of Several SARS-CoV-2 Variants Of Concern Prevent Recognition of the Human ACE2 Receptor and Consecutive Cell Infections

New strategies are needed to prevent and control upcoming outbreaks of SARS-CoV-2 infections, independent of vaccination. SARS-CoV-2 binds to the human ACE-2 receptor through the receptor binding domain (RBD) of the spike (S) protein, allowing the virus to enter human cells and begin replication. When peptides corresponding to four regions of RBD containing previously reported ACE-2 interaction sites were explored, the sequence 392 to 421, peptide p392wt, bound strongly to ACE-2 and inhibited wild-type RBD binding to ACE-2. Interestingly, p392 peptides corresponding to mutated sequences from different SARS-CoV-2 VOCs, including the current VOC BA.5 and KP.3, bound less strongly to ACE-2, but showed partially better inhibition of the ACE-2 interaction of all tested RBDs. When studied in a SARS-CoV-2 pseudovirus assay, the p392 peptides showed a good inhibition rate of 98.8±8.1 % at a peptide concentration of ~244 μmol/L, while none of the p392 peptides inhibited antibody binding to the RBD, suggesting that peptide treatment is sufficient in the presence of anti-RBD antibodies. Interestingly these peptides were active in the presence of diluted human serum and non-toxic to human cell lines.

Advances in Antimicrobial Peptides: Mechanisms, Design Innovations, and Biomedical Potential

This comprehensive review explores the advancements in the study of antimicrobial peptides (AMPs), highlighting their potential as promising alternatives to conventional antibiotics in the context of growing antibiotic resistance. AMPs are small molecular proteins found ubiquitously in nature, exhibiting broad-spectrum antimicrobial activity, including antibacterial, antiviral, and antifungal effects, and are vital components of the innate immune system. Due to their non-specific membrane-disrupting mechanism, AMPs are emerging as effective candidates for novel anti-infective agents. The integration of AMPs with biomaterials, such as nanoparticles, liposomes, polymers, and hydrogels, enhances their stability and efficacy while offering multifunctional therapeutic benefits. These combinations promote diverse antibacterial mechanisms, including membrane disruption, intracellular metabolic interference, cell wall modulation, and immune system activation. Despite challenges, such as toxicity, stability, and resistance, innovative strategies including computer-aided design and structural modification show promise in optimizing AMPs' activity, targeting precision, and biocompatibility. The potential for AMPs in clinical applications remains highly promising, with significant opportunities for overcoming antimicrobial resistance through novel AMP-based therapeutic strategies.

In silico antiviral effect assessment of some venom gland peptides from Odontobuthus doriae scorpion against SARS-CoV-2

SARS-CoV-2 is from the enveloped virus family responsible for the COVID-19 pandemic. No efficient drugs are currently available to treat infection explicitly caused by this virus. Therefore, searching for effective treatments for severe illness caused by SARS-CoV-2 is crucial. Scorpion venoms are significant sources of peptides with pharmaceutical potential, including antivirals. Although some studies have determined the antiviral effects of some scorpion peptides on other members of the Coronaviridae family, a few anti-SARS-CoV-2 effects of these peptides have been reported until now. This study assessed the antiviral effects of five predicted antimicrobial peptides with potential for antiviral activities from the Iranian yellow scorpion "Odontobuthus doriae" by computational methods. These peptides were selected from the cDNA library that our research team constructed. A 3D model of peptides was designed with I-TASSER. The models were refined using a 200 ns Molecular Dynamics (MD) simulation using Gromacs 2021.2 software. Refined models were Docked with the RBD domain of SARS-CoV-2 spike protein using HADDOCK software. The docking of human ACE2 peptide with the RBD domain was also assessed. The docked complexes (RBD-peptide and RBD-ACE2) were refined again by a 100 ns MD simulation and then analyzed. The results from molecular docking after molecular dynamics simulation showed that ODAMP2 and ODAMP5 after stabilizing analysis and according to MMPBSA results (with -59.24 kcal/mol and -51.82 kcal/mol, respectively) have a strong binding affinity to the RBD domain of COVID-19 spike protein compared to human ACE2 and some other studied components. Therefore, this peptide can be an excellent candidate for use as an agent to inhibit the RBD domain of SARS-COV2 virus in clinical studies for medicinal purposes after in vitro and in vivo laboratory evaluations.

Segment-Based Peptide Design Reveals the Importance of N-Terminal High Cationicity for Antimicrobial Activity Against Gram-Negative Pathogens

Host defense antimicrobial peptides (AMPs) are recognized candidates to develop a new generation of peptide antibiotics. While high hydrophobicity can be deployed in peptides for eliminating Gram-positive bacteria, high cationicity is usually observed in AMPs against Gram-negative pathogen. This study investigates how the sequence distribution of basic amino acids affects peptide activity. For this purpose, we utilized human cathelicidin LL-37 as a template and designed four highly selective ultrashort peptides with similar length, net charge, and hydrophobic content. LL-10 + , RK-9 + , KR-8 + , and RIK-10 + showed similar activity against methicillin-resistant Staphylococcus aureus in vitro and comparable antibiofilm efficacy in a murine wound model. However, these peptides showed clear activity differences against Gram-negative pathogens with RIK-10 + (i.e., LL-37mini2) being the strongest and LL-10 + the weakest. To understand this activity difference, we characterized peptide toxicity; the effects of salts, pH, and serum on peptide activity; and the mechanism of action and determined the membrane-bound helical structure for RIK-10 + by two-dimensional NMR spectroscopy. By writing an R program, we generated charge density plots for these peptides and uncovered the importance of the N-terminal high-density basic charges for antimicrobial potency. To validate this finding, we reversed the sequences of two peptides. Interestingly, sequence reversal weakened the activity of RIK-10 + but increased the activity of LL-10 + especially against Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii. Those more active peptides with high cationicity at the N-terminus are also more hydrophobic based on HPLC retention times. A database search found numerous natural sequences that arrange basic amino acids primarily at the N-terminus. Combined, this study not only obtained novel peptide leads but also discovered one useful strategy for designing novel antimicrobials to control drug-resistant Gram-negative pathogens.

Antiviral activity of cathelicidins against porcine epidemic diarrhea virus (PEDV): Mechanisms, and efficacy

Porcine epidemic diarrhea virus (PEDV) is a harmful coronavirus infecting pigs, which is resulting in substantial financial losses in the global pig industry. The lack of effective vaccines or treatments underscores the pressing need for new antiviral strategies. Antimicrobial peptides (AMPs), specifically cathelicidins such as LL-37, have demonstrated promising activity against a range of viruses. This study aims to elucidate the antiviral mechanisms of cathelicidins by examining their inhibitory capabilities against PEDV in vitro. Four pig-derived antimicrobial peptides (PMAP-36, PMAP-23, PR-39, and PG-1), together with chicken-derived CATH-B1 and human-derived LL-37 were analyzed for their anti-PEDV activity. Flow cytometry and fluorescent microscopy confirmed that LL-37 and CATH-B1 had strong inhibitory effects at non-toxic concentrations of 5 and 10 µM, significantly reducing GFP-PEDV infection of Vero cells both in co- and pre-incubation setups. In contrast, none of the porcine peptides exhibited any inhibitory effects, even at higher doses. Fluorogenic LL-37 was shown to enter VERO cells, indicative of a possible immunomodulatory antiviral mode of action. However, transmission electron microscopy clearly indicated that both LL-37 and CATH-B1 affected virus morphology and caused aggregation of viral particles, showing that peptide-virus interaction caused reduced virus infectivity. In conclusion, this analysis highlights the potential of LL-37 and CATH-B1 as inhibitors against PEDV, suggesting promising directions for innovative therapeutic antiviral strategies.

P-selectin Facilitates SARS-CoV-2 Spike 1 Subunit Attachment to Vesicular Endothelium and Platelets

SARS-CoV-2 infection starts from the association of its spike 1 (S1) subunit with sensitive cells. Vesicular endothelial cells and platelets are among the cell types that bind SARS-CoV-2, but the effectors that mediate viral attachment on the cell membrane have not been fully elucidated. Herein, we show that P-selectin (SELP), a biomarker for endothelial dysfunction and platelet activation, can facilitate the attachment of SARS-CoV-2 S1. Since we observe colocalization of SELP with S1 in the lung tissues of COVID-19 patients, we perform molecular biology experiments on human umbilical vein endothelial cells (HUVECs) to confirm the intermolecular interaction between SELP and S1. SELP overexpression increases S1 recruitment to HUVECs and enhances SARS-CoV-2 spike pseudovirion infection. The opposite results are determined after SELP downregulation. As S1 causes endothelial inflammatory responses in a dose-dependent manner, by activating the interleukin (IL)-17 signaling pathway, SELP-induced S1 recruitment may contribute to the development of a "cytokine storm" after viral infection. Furthermore, SELP also promotes the attachment of S1 to the platelet membrane. Employment of PSI-697, a small inhibitor of SELP, markedly decreases S1 adhesion to both HUVECs and platelets. In addition to the role of membrane SELP in facilitating S1 attachment, we also discover that soluble SELP is a prognostic factor for severe COVID-19 through a meta-analysis. In this study, we identify SELP as an adhesive site for the SARS-CoV-2 S1, thus providing a potential drug target for COVID-19 treatment.

Recent advances in the therapeutic potential of cathelicidins

The alarming increase in antimicrobial resistance in the last decades has prompted the search for alternatives to control infectious diseases. Antimicrobial peptides (AMPs) represent a heterogeneous class of molecules with ample antibacterial, antiviral, and antifungal effects. They can be found in many organisms, including all classes of vertebrates, providing a valuable source of new antimicrobial agents. The unique properties of AMPs make it harder for microbes develop resistance, while their immunomodulatory properties and target diversity reinforce their translational use in multiple diseases, from autoimmune disorders to different types of cancer. The latest years have witnessed a vast number of studies evaluating the use of AMPs in therapy, with many progressing to clinical trials. The present review explores the recent developments in the medicinal properties of cathelicidins, a vast family of AMPs with potent antimicrobial and immunomodulatory effects. Cathelicidins from several organisms have been tested in disease models of viral and bacterial infections, inflammatory diseases, and tumors, with encouraging results. Combining nanomaterials with active, natural antimicrobial peptides, including LL-37 and synthetic analogs like ceragenins, leads to the creation of innovative nanoagents with significant clinical promise. However, there are still important limitations, such as the toxicity of many cathelicidins to healthy host cells and low stability in vivo. The recent advances in nanomaterials and synthetic biology may help overcome the current limitations, enabling the use of cathelicidins in future therapeutics. Furthermore, a better understanding of the mechanisms of cathelicidin action in vivo and their synergy with other host molecules will contribute to the development of safer, highly effective therapies.

Enhancing RNA Payload and Temperature Stability and Activity with Cationic Peptide-Coated Zinc Oxide Nanoparticles

The lipid nanoparticle (LNP) mRNA vaccine was first tested through clinic but suffered from relatively low RNA payloads and poor temperature stability. Our lab patented a protamine-coated particle approach for temperature-stabilizing DNA vaccines, translating this successfully to the clinic. In subsequent work, we have characterized RNA interaction and delivery by zinc oxide nanoparticles, filing a patent most recently entitled RNA-stabilizing nanoparticles, similarly utilizing protamine-coated zinc oxide nanoparticles for RNA. Here, we present this data for the first time. Briefly, ZnO, ZnO-protamine, and ZnO-protamine-RNA were characterized by size and zeta potential analyses and the RNA-loaded nanoparticles were visualized by transmission electron microscopy. UV spectroscopic analysis demonstrated up to 95-98% loading efficiency with protamine and approximately 75% loading efficiency with LL37, another cationic antiviral peptide. Elution of the RNA isolated from the particles afforded a calculation in three independent trials where RNA payloads ranged from 18 to 45 μg of RNA per 0.5 mg of coated particles. Circular dichroism (CD) analysis indicated that binding of RNA to ZnO NPs stabilized, enhancing the pattern with a clear dependence on the RNA:ZnO stoichiometry. Enhanced temperature stability was shown by differential scanning calorimetry (DSC), gel electrophoresis, and in vitro mRNA expression analysis. Using poly I:C RNA with a well-defined melting point (64.3 ± 0.32 °C), formation of the ZnO:RNA complex increased the RNA melting point (70.9 ± 0.62 °C). After refrigerated or room-temperature storage or incubation at 30, 40, or 50 °C, RNA comigration with the control RNA was recovered from all samples, exposed to either 14 or 100 nm ZnO, and coated with protamine. Furthermore, the ZnO-protamine-mRNA samples retained significantly higher expression activity when incubated at these elevated temperatures. Finally, the ZnO-protamine-mRNA was functionally active for in vitro translation, in cell extracts, and in cells for expression of GFP, luciferase, and COVID spike protein. These data support further preclinical development of ZnO-protamine-mRNA.

Antimicrobial peptides and other potential biomarkers of critical illness in SARS-CoV-2 patients with acute kidney injury. AMPAKI-CoV study

Antimicrobial peptides (AMPs) constitute a complex network of 10-100 amino acid sequence molecules widely distributed in nature. While over 300 AMPs have been described in mammals, cathelicidins and defensins remain the most extensively studied. Some publications have explored the role of AMPs in COVID-19, but these findings are preliminary, and in vivo studies are still lacking. In this study, we report the plasma levels of five AMPs (LL-37, α-defensin 1, α-defensin 3, β-defensin 1, and β-defensin 3), using the ELISA technique (MyBioSource, San Diego, CA, United States, kits MBS2601339 (beta-defensin 1), MBS2602513 (beta-defensin 3), MBS703879 (alpha-defensin 1), MBS706289 (alpha-defensin 3), MBS7234921 (LL37)), and the measurement of six cytokines (tumor necrosis factor-α, interleukin-1β, interleukin-6, interleukin-10, interferon-γ, and monocyte chemoattractant protein-1), through the magnetic bead immunoassay Milliplex® and the MAGPIX® System (MilliporeSigma, Darmstadt, Germany, kit HCYTOMAG-60 K (cytokines)), in 15 healthy volunteers, 36 COVID-19 patients without Acute Kidney Injury (AKI) and 17 COVID-19 patients with AKI. We found increased levels of α-defensin 1, α-defensin 3 and β-defensin 3, in our COVID-19 population, when compared to healthy controls, along with higher levels of interleukin-6, interleukin-10, interferon-γ, and monocyte chemoattractant protein-1. These findings suggest that these AMPs and cytokines may play a crucial role in the systemic inflammatory response and tissue damage characterizing severe COVID-19. The levels of α-defensin 1 and α-defensin 3 were significantly higher in COVID-19 AKI group in comparison to the non-AKI group. Furthermore, IL-10 and the product IL-10 × IL-1B showed excellent performance in discriminating AKI, with AUCs of 0.86 and 0.88, respectively. Among patients with COVID-19, AMPs may play a key role in the inflammation process and disease progression. Additionally, α-defensin 1 and α-defensin 3 may mediate the AKI process in these patients, representing an opportunity for further research and potential therapeutic alternatives in the future.

A novel film spray containing curcumin inhibits SARS-CoV-2 and influenza virus infection and enhances mucosal immunity

BACKGROUND

Infection by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and influenza virus is still a major worldwide health concern. Plants are a good source of bioactive compounds to be used as preventive measures for both inhibiting the virus binding and enhancing mucosal innate immunity. Curcumin has been shown to possess antiviral activity and modulate innate immunity. Therefore, the purpose of this study was to develop an oro-nasal film spray containing curcumin and determine its antiviral activity against SARS-CoV-2 and influenza virus infection, as well as its effects on mucosal innate immunity and inflammatory cytokines in vitro.

METHODS

The antiviral activity of the film spray against SARS-CoV-2, influenza A/H1N1, A/H3N2, and influenza B was assessed in vitro by plaque reduction assay. Cytotoxicity of the film spray to oral keratinocytes and nasal epithelial cells was assessed by MTT assay, and cytotoxicity to Vero and MDCK cells was assessed by an MTS-based cytotoxicity assay. Oral and nasal innate immune markers in response to the film spray were determined by ELISA and by a commercial Milliplex Map Kit, respectively.

RESULTS

Our data show that the film spray containing curcumin can inhibit both SARS-CoV-2 and influenza virus infections while maintaining cell viability. Results obtained among 4 viruses revealed that curcumin film spray demonstrated the highest inhibitory activity against SARS-CoV-2 with the lowest EC50 of 3.15 µg/ml and the highest SI value of 4.62, followed by influenza B (EC50 = 6.32 µg/ml, SI = 2.04), influenza A/H1N1 (EC50 = 7.24 µg/ml, SI = 1.78), and influenza A/H3N2 (EC50 > 12.5 µg/ml, SI < 1.03), respectively. Antimicrobial peptides LL-37 and HD-5, IL-6 and TNF-α produced by oral keratinocytes were significantly induced by the film spray, while hBD2 was significantly reduced.

CONCLUSION

Film spray containing curcumin possesses multiple actions against SARS-CoV-2 infection by inhibiting ACE-2 binding in target cells and enhancing mucosal innate immunity. The film spray can also inhibit influenza virus infection. Therefore, the curcumin film spray may be effective in preventing the viral infection of both SARS-CoV-2 and influenza.

Antimicrobial peptides for novel antiviral strategies in the current post-COVID-19 pandemic

The recent pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has highlighted how urgent and necessary the discovery of new antiviral compounds is for novel therapeutic approaches. Among the various classes of molecules with antiviral activity, antimicrobial peptides (AMPs) of innate immunity are among the most promising ones, mainly due to their different mechanisms of action against viruses and additional biological properties. In this review, the main physicochemical characteristics of AMPs are described, with particular interest toward peptides derived from amphibian skin. Living in aquatic and terrestrial environments, amphibians are one of the richest sources of AMPs with different primary and secondary structures. Besides describing the various antiviral activities of these peptides and the underlying mechanism, this review aims at emphasizing the high potential of these small molecules for the development of new antiviral agents that likely reduce the selection of resistant strains.

Dietary Vitamin D Mitigates Coronavirus-Induced Lung Inflammation and Damage in Mice

The COVID-19 pandemic caused by the SARS-CoV-2 (β-CoV) betacoronavirus has posed a significant threat to global health. Despite the availability of vaccines, the virus continues to spread, and there is a need for alternative strategies to alleviate its impact. Vitamin D, a secosteroid hormone best known for its role in bone health, exhibits immunomodulatory effects in certain viral infections. Here, we have shown that bioactive vitamin D (calcitriol) limits in vitro replication of SARS-CoV-2 and murine coronaviruses MHV-3 and MHV-A59. Comparative studies involving wild-type mice intranasally infected with MHV-3, a model for studying β-CoV respiratory infections, confirmed the protective effect of vitamin D in vivo. Accordingly, mice fed a standard diet rapidly succumbed to MHV-3 infection, whereas those on a vitamin D-rich diet (10,000 IU of Vitamin D3/kg) displayed increased resistance to acute respiratory damage and systemic complications. Consistent with these findings, the vitamin D-supplemented group exhibited lower viral titers in their lungs and reduced levels of TNF, IL-6, IL-1β, and IFN-γ, alongside an enhanced type I interferon response. Altogether, our findings suggest vitamin D supplementation ameliorates β-CoV-triggered respiratory illness and systemic complications in mice, likely via modulation of the host's immune response to the virus.

Niacinamide enhances cathelicidin mediated SARS-CoV-2 membrane disruption

The continual emergence of SARS-CoV-2 variants threatens to compromise the effectiveness of worldwide vaccination programs, and highlights the need for complementary strategies for a sustainable containment plan. An effective approach is to mobilize the body's own antimicrobial peptides (AMPs), to combat SARS-CoV-2 infection and propagation. We have found that human cathelicidin (LL37), an AMP found at epithelial barriers as well as in various bodily fluids, has the capacity to neutralise multiple strains of SARS-CoV-2. Biophysical and computational studies indicate that LL37's mechanism of action is through the disruption of the viral membrane. This antiviral activity of LL37 is enhanced by the hydrotropic action of niacinamide, which may increase the bioavailability of the AMP. Interestingly, we observed an inverse correlation between LL37 levels and disease severity of COVID-19 positive patients, suggesting enhancement of AMP response as a potential therapeutic avenue to mitigate disease severity. The combination of niacinamide and LL37 is a potent antiviral formulation that targets viral membranes of various variants and can be an effective strategy to overcome vaccine escape.

A Bioresponsive Genetically Encoded Antimicrobial Crystal for the Oral Treatment of Helicobacter Pylori Infection

Helicobacter pylori (H. pylori) causes infection in the stomach and is a major factor for gastric carcinogenesis. The application of antimicrobial peptides (AMPs) as an alternative treatment to traditional antibiotics is limited by their facile degradation in the stomach, their poor penetration of the gastric mucosa, and the cost of peptide production. Here, the design and characterization of a genetically encoded H. pylori-responsive microbicidal protein crystal Cry3Aa-MIIA-AMP-P17 is described. This designed crystal exhibits preferential binding to H. pylori, and when activated, promotes the targeted release of the AMP at the H. pylori infection site. Significantly, when the activated Cry3Aa-MIIA-AMP-P17 crystals are orally delivered to infected mice, the Cry3Aa crystal framework protects its cargo AMP against degradation, resulting in enhanced in vivo efficacy against H. pylori infection. Notably, in contrast to antibiotics, treatment with the activated crystals results in minimal perturbation of the mouse gut microbiota. These results demonstrate that engineered Cry3Aa crystals can serve as an effective platform for the oral delivery of therapeutic peptides to treat gastrointestinal diseases.

A review of the antiviral activity of cationic antimicrobial peptides

Viral epidemics are occurring frequently, and the COVID-19 viral pandemic has resulted in at least 6.5 million deaths worldwide. Although antiviral therapeutics are available, these may not have sufficient effect. The emergence of resistant or novel viruses requires new therapies. Cationic antimicrobial peptides are agents of the innate immune system that may offer a promising solution to viral infections. These peptides are gaining attention as possible therapies for viral infections or for use as prophylactic agents to prevent viral spread. This narrative review examines antiviral peptides, their structural features, and mechanism of activity. A total of 156 cationic antiviral peptides were examined for information of their mechanism of action against both enveloped and non-enveloped viruses. Antiviral peptides can be isolated from various natural sources or can be generated synthetically. The latter tend to be more specific and effective and can be made to have a broad spectrum of activity with minimal side effects. Their unique properties of being positively charged and amphipathic enable their main mode of action which is to target and disrupt viral lipid envelopes, thereby inhibiting viral entry and replication. This review offers a comprehensive summary of the current understanding of antiviral peptides, which could potentially aid in the design and creation of novel antiviral medications.

Efficacy and safety of Oral LL-37 against the Omicron BA.5.1.3 variant of SARS-COV-2: A randomized trial

Recombinant LL-37 Lactococcus lactis (Oral LL-37) was designed to prevent progression of COVID-19 by targeting virus envelope, however, effectiveness and safety of Oral LL-37 in clinical application was unclear. A total of 238 adult inpatients, open-labelled, randomized, placebo-controlled, single-center study was conducted to investigate the primary end points, including negative conversion time (NCT) of SARS-CoV-2 RNA and adverse events (AEs). As early as intervened on 6th day of case confirmed, Oral LL-37 could significantly shorten NCT (LL-37 9.80 ± 2.67 vs. placebo 14.04 ± 5.89, p < 0.01). For Oral LL-37, as early as treated in 6 days, the adjusted hazard ratio (HR) for a primary event of nucleic acid negative outcome was 6.27-fold higher than 7-day-later (HR: 6.276, 95% confidence interval [CI]: 3.631-10.848, p < 0.0001), and the adjusted HR of Oral LL-37 within 6 days is higher than placebo (HR: 2.427 95% CI: 1.239-4.751, p = 0.0097). No severe AEs were observed during hospitalization and follow-up investigation. This study shows that early intervention of Oral LL-37 incredibly reduces NCT implying a potential for clearance of Omicron BA.5.1.3 without evident safety concerns.

Vitamin D Deficiency in COVID-19 Patients and Role of Calcifediol Supplementation

Hypovitaminosis D has been associated with worse outcome in respiratory tract infections, with conflicting opinions regarding its role in Coronavirus-19 disease (COVID-19). Our study aimed to evaluate the possible relationship between 25-OH vitamin D (25OHD) values and the following conditions in patients hospitalized for COVID-19: prognosis, mortality, invasive (IV) and non-invasive (NIV) mechanical ventilation, and orotracheal intubation (OTI). A further objective was the analysis of a possible positive effect of supplementation with calcifediol on COVID-19 severity and prognosis. We analyzed 288 patients hospitalized at the San Giovanni di Dio Hospital in Florence and the Santa Maria alle Scotte Hospital in Siena, from November 2020 to February 2021. The 25OHD levels correlated positively with the partial pressure of oxygen and FiO2 (PaO2/FiO2) ratio (r = 0.17; p < 0.05). Furthermore, when we analyzed the patients according to the type of respiratory support, we found that 25OHD levels were markedly reduced in patients who underwent non-invasive ventilation and orotracheal intubation (OTI). The evaluation of the length of hospitalization in our population evidenced a longer duration of hospitalization in patients with severe 25OHD deficiency (<10 ng/mL). Moreover, we found a statistically significant difference in the mortality rate between patients who had 25OHD levels below 10 ng/mL and those with levels above this threshold in the total population (50.8% vs. 25.5%, p = 0.005), as well as between patients with 25OHD levels below 20 ng/mL and those with levels above that threshold (38.4% vs. 24.6%, p = 0.04). Moreover, COVID-19 patients supplemented with calcifediol presented a significantly reduced length of hospitalization (p < 0.05). Interestingly, when we analyzed the possible effects of calcifediol on mortality rate in patients with COVID-19, we found that the percentage of deaths was significantly higher in patients who did not receive any supplementation than in those who were treated with calcifediol (p < 0.05) In conclusion, we have demonstrated with our study the best prognosis of COVID-19 patients with adequate vitamin D levels and patients treated with calcifediol supplementation.

Preparing for the next viral threat with broad-spectrum antivirals

There is a large global unmet need for the development of countermeasures to combat hundreds of viruses known to cause human disease and for the establishment of a therapeutic portfolio for future pandemic preparedness. Most approved antiviral therapeutics target proteins encoded by a single virus, providing a narrow spectrum of coverage. This, combined with the slow pace and high cost of drug development, limits the scalability of this direct-acting antiviral (DAA) approach. Here, we summarize progress and challenges in the development of broad-spectrum antivirals that target either viral elements (proteins, genome structures, and lipid envelopes) or cellular proviral factors co-opted by multiple viruses via newly discovered compounds or repurposing of approved drugs. These strategies offer new means for developing therapeutics against both existing and emerging viral threats that complement DAAs.

Positive correlational shift between crevicular antimicrobial peptide LL-37, pain and periodontal status following non-surgical periodontal therapy. A pilot study

BACKGROUND

Periodontitis has a high prevalence and uncertain recurrence. Unlike the pro-inflammatory cytokine profile, little is known about the anti-inflammatory cytokine and antimicrobial peptide overview following treatment. The present study aimed to evaluate if any of the antimicrobial peptide LL-37, interleukin (IL) 4, 10 and 6 together with the volume of gingival crevicular fluid (GCF) and total protein concentration in GCF could be used as correlative biomarkers for the severity in periodontitis as well as prognostic factors in the management of the disease.

METHODS

Forty-five participants were recruited and allocated to the healthy (15), Stage I-II (15) or Stage III-IV periodontitis (15) group. Along with periodontal examination, GCF samples were obtained at baseline and 4-6 weeks following scaling and root planing (SRP) for the periodontitis groups. GCF samples were analyzed by ELISA kits to quantify LL-37 and IL-4, -6 and - 10. One-way ANOVA followed by Dunnett's test was used to determine differences among the three groups at baseline. Two-way ANOVA followed by Sidak's post-hoc test was used to compare between pre- and post-SRP in the two periodontitis groups.

RESULTS

The amount of GCF volume was significantly correlated to the severity of periodontitis and decreased following SRP, particularly in the Stage III-IV group (p < 0.01). The levels of LL-37, IL-6, and pain and periodontal clinical parameters were significantly correlated to the severity of periodontitis. IL-4 and IL-10 in the periodontitis groups were significantly lower than the healthy group (p < 0.0001) and barely improved following SRP up to the level of the healthy group.

CONCLUSIONS

With the limitations of this study, crevicular LL-37 may be a candidate for a biomarker of periodontitis and the associated pain upon probing.

TRIAL REGISTRATION

The study was registered in clinical trials.gov, with number NCT04404335, dated 27/05/2020.

Role of antimicrobial peptide cathelicidin in thrombosis and thromboinflammation

Thrombosis is a frequent cause of cardiovascular mortality and hospitalization. Current antithrombotic strategies, however, target both thrombosis and physiological hemostasis and thereby increase bleeding risk. In recent years the pathophysiological understanding of thrombus formation has significantly advanced and inflammation has become a crucial element. Neutrophils as most frequent immune cells in the blood and their released mediators play a key role herein. Neutrophil-derived cathelicidin next to its strong antimicrobial properties has also shown to modulates thrombosis and thus presents a potential therapeutic target. In this article we review direct and indirect (immune- and endothelial cell-mediated) effects of cathelicidin on platelets and the coagulation system. Further we discuss its implications for large vessel thrombosis and consecutive thromboinflammation as well as immunothrombosis in sepsis and COVID-19 and give an outlook for potential therapeutic prospects.

Immunomodulatory Properties of Vitamin D in the Intestinal and Respiratory Systems

Vitamin D plays a crucial role in modulating the innate immune response by interacting with its intracellular receptor, VDR. In this review, we address vitamin D/VDR signaling and how it contributes to the regulation of intestinal and respiratory microbiota. We additionally review some components of the innate immune system, such as the barrier function of the pulmonary and intestinal epithelial membranes and secretion of mucus, with their respective modulation by vitamin D. We also explore the mechanisms by which this vitamin D/VDR signaling mounts an antimicrobial response through the transduction of microbial signals and the production of antimicrobial peptides that constitute one of the body’s first lines of defense against pathogens. Additionally, we highlight the role of vitamin D in clinical diseases, namely inflammatory bowel disease and acute respiratory distress syndrome, where excessive inflammatory responses and dysbiosis are hallmarks. Increasing evidence suggests that vitamin D supplementation may have potentially beneficial effects on those diseases.

High-Throughput CAMP Assay (HiTCA): A Novel Tool for Evaluating the Vitamin D-Dependent Antimicrobial Response

Vitamin D is known to modulate human immune responses, and vitamin D deficiency is associated with increased susceptibility to infection. However, what constitutes sufficient levels or whether vitamin D is useful as an adjuvant therapeutic is debated, much in part because of inadequate elucidation of mechanisms underlying vitamin D's immune modulatory function. Cathelicidin antimicrobial peptide (CAMP) has potent broad-spectrum activity, and the CAMP gene is regulated in human innate immune cells by active 1,25(OH)2D3, a product of hydroxylation of inactive 25(OH)D3 by CYP27B1-hydroxylase. We developed a CRISPR/Cas9-edited human monocyte-macrophage cell line containing the mCherry fluorescent reporter gene at the 3' end of the endogenous CAMP gene. The High Throughput CAMP Assay (HiTCA) developed here is a novel tool for evaluating CAMP expression in a stable cell line that is scalable for a high-throughput workflow. Application of HiTCA to serum samples from a small number of human donors (n = 10) showed individual differences in CAMP induction that were not fully accounted for by the serum vitamin D metabolite status of the host. As such, HiTCA may be a useful tool that can advance our understanding of the human vitamin D-dependent antimicrobial response, which is being increasingly appreciated for its complexity.

Evaluation of In Vitro and In Vivo Antiviral Activities of Vitamin D for SARS-CoV-2 and Variants

The COVID-19 pandemic has brought about unprecedented medical and healthcare challenges worldwide. With the continual emergence and spread of new COVID-19 variants, four drug compound libraries were interrogated for their antiviral activities against SARS-CoV-2. Here, we show that the drug screen has resulted in 121 promising anti-SARS-CoV-2 compounds, of which seven were further shortlisted for hit validation: citicoline, pravastatin sodium, tenofovir alafenamide, imatinib mesylate, calcitriol, dexlansoprazole, and prochlorperazine dimaleate. In particular, the active form of vitamin D, calcitriol, exhibits strong potency against SARS-CoV-2 on cell-based assays and is shown to work by modulating the vitamin D receptor pathway to increase antimicrobial peptide cathelicidin expression. However, the weight, survival rate, physiological conditions, histological scoring, and virus titre between SARS-CoV-2 infected K18-hACE2 mice pre-treated or post-treated with calcitriol were negligible, indicating that the differential effects of calcitriol may be due to differences in vitamin D metabolism in mice and warrants future investigation using other animal models.

COVID-19 and Multiple Sclerosis: A Complex Relationship Possibly Aggravated by Low Vitamin D Levels

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an exceptionally transmissible and pathogenic coronavirus that appeared at the end of 2019 and triggered a pandemic of acute respiratory disease, known as coronavirus disease 2019 (COVID-19). COVID-19 can evolve into a severe disease associated with immediate and delayed sequelae in different organs, including the central nervous system (CNS). A topic that deserves attention in this context is the complex relationship between SARS-CoV-2 infection and multiple sclerosis (MS). Here, we initially described the clinical and immunopathogenic characteristics of these two illnesses, accentuating the fact that COVID-19 can, in defined patients, reach the CNS, the target tissue of the MS autoimmune process. The well-known contribution of viral agents such as the Epstein-Barr virus and the postulated participation of SARS-CoV-2 as a risk factor for the triggering or worsening of MS are then described. We emphasize the contribution of vitamin D in this scenario, considering its relevance in the susceptibility, severity and control of both pathologies. Finally, we discuss the experimental animal models that could be explored to better understand the complex interplay of these two diseases, including the possible use of vitamin D as an adjunct immunomodulator to treat them.

Peptide-based inhibitors hold great promise as the broad-spectrum agents against coronavirus

Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV), Middle East Respiratory Syndrome (MERS), and the recent SARS-CoV-2 are lethal coronaviruses (CoVs) that have caused dreadful epidemic or pandemic in a large region or globally. Infections of human respiratory systems and other important organs by these pathogenic viruses often results in high rates of morbidity and mortality. Efficient anti-viral drugs are needed. Herein, we firstly take SARS-CoV-2 as an example to present the molecular mechanism of CoV infection cycle, including the receptor binding, viral entry, intracellular replication, virion assembly, and release. Then according to their mode of action, we provide a summary of anti-viral peptides that have been reported in peer-reviewed publications. Even though CoVs can rapidly evolve to gain resistance to the conventional small molecule drugs, peptide-based inhibitors targeting various steps of CoV lifecycle remain a promising approach. Peptides can be continuously modified to improve their antiviral efficacy and spectrum along with the emergence of new viral variants.

Blood leukocyte transcriptional modules and differentially expressed genes associated with disease severity and age in COVID-19 patients

Since the molecular mechanisms determining COVID-19 severity are not yet well understood, there is a demand for biomarkers derived from comparative transcriptome analyses of mild and severe cases, combined with patients' clinico-demographic and laboratory data. Here the transcriptomic response of human leukocytes to SARS-CoV-2 infection was investigated by focusing on the differences between mild and severe cases and between age subgroups (younger and older adults). Three transcriptional modules correlated with these traits were functionally characterized, as well as 23 differentially expressed genes (DEGs) associated to disease severity. One module, correlated with severe cases and older patients, had an overrepresentation of genes involved in innate immune response and in neutrophil activation, whereas two other modules, correlated with disease severity and younger patients, harbored genes involved in the innate immune response to viral infections, and in the regulation of this response. This transcriptomic mechanism could be related to the better outcome observed in younger COVID-19 patients. The DEGs, all hyper-expressed in the group of severe cases, were mostly involved in neutrophil activation and in the p53 pathway, therefore related to inflammation and lymphopenia. These biomarkers may be useful for getting a better stratification of risk factors in COVID-19.

Irradiation accelerates SARS-CoV-2 infection by enhancing sphingolipid metabolism

Cancer patients who receive radiotherapy have a high risk of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection, but the concrete reason remains unclear. Herein, we investigated the influence of irradiation on the vulnerability of cancer cells to SARS-CoV-2 using S pseudovirions and probed the underlying mechanism via RNA-seq and other molecular biology techniques. Owing to the enhancement of sphingolipid metabolism, irradiation accelerated pseudovirion infection. Mechanistically, irradiation induced the expression of acid sphingomyelinase (ASM), which catalyses the hydrolysis of sphingomyelin to ceramide, contributing to lipid raft formation and promoting SARS-CoV-2 invasion. Inhibition of lipid raft formation with methyl-β-cyclodextrin (MβCD) or the tyrosine kinase inhibitor genistein and ASM suppression through small interfering RNA or amitriptyline (AMT) treatment abolished the enhancing effect of irradiation on viral infection. Animal experiments supported the finding that irradiation promoted SARS-CoV-2 S pseudovirion infection in A549 cell tumour-bearing BALB/c nude mice, whereas AMT treatment dramatically decreased viral infection. This study discloses the role of sphingolipid metabolism in irradiation-induced SARS-CoV-2 infection, thus providing a potential target for clinical intervention to protect patients receiving radiotherapy from COVID-19.

Possible Impact of Vitamin D Status and Supplementation on SARS-CoV-2 Infection Risk and COVID-19 Symptoms in a Cohort of Patients with Inflammatory Bowel Disease

The coronavirus disease (COVID-19) pandemic represents a global health challenge, particularly considering concomitant diseases. Patients with inflammatory bowel diseases (IBD) can be considered a population at risk. On the other hand, the risk of developing IBD and COVID-19 have both been described as modulated by vitamin D (VD) levels. In this work, a cohort of 106 adult patients affected by IBD was prospectively enrolled, during the second wave of the pandemic in Italy. In these patients, VD plasma levels, demographic, and clinical characteristics were tested for a correlation/an association with the risk of infection with SARS-CoV-2 in the study period (anti-spike IgG positivity) and the severity of COVID-19 symptoms. By multivariate logistic regression analysis, VD supplementation (Odds Ratio; OR 0.116, p = 0.002), therapy with monoclonal antibodies (OR 0.227, p = 0.007), and the use of mesalazine (OR 2.968, p = 0.046) were found to be independent predictors of SARS-CoV-2 positivity. Moreover, hypertension was associated with severe disease (p = 0.019), while a VD level higher than 30 ng/mL (p = 0.031, OR 0.078) was associated with asymptomatic infection. No interplay between IBD activity and COVID-19 risk of infection or symptoms was observed. These results confirm the importance of VD levels in defining the risk of COVID-19 and give encouraging data about the safety of maintaining immunomodulatory treatments for IBD during the COVID-19 pandemic.

HBD-2 variants and SARS-CoV-2: New insights into inter-individual susceptibility

Background

A deep understanding of the causes of liability to SARS-CoV-2 is essential to develop new diagnostic tests and therapeutics against this serious virus in order to overcome this pandemic completely. In the light of the discovered role of antimicrobial peptides [such as human b-defensin-2 (hBD-2) and cathelicidin LL-37] in the defense against SARS-CoV-2, it became important to identify the damaging missense mutations in the genes of these molecules and study their role in the pathogenesis of COVID-19.

Methods

We conducted a comprehensive analysis with multiple in silico approaches to identify the damaging missense SNPs for hBD-2 and LL-37; moreover, we applied docking methods and molecular dynamics analysis to study the impact of the filtered mutations.

Results

The comprehensive analysis reveals the presence of three damaging SNPs in hBD-2; these SNPs were predicted to decrease the stability of hBD-2 with a damaging impact on hBD-2 structure as well. G51D and C53G mutations were located in highly conserved positions and were associated with differences in the secondary structures of hBD-2. Docking-coupled molecular dynamics simulation analysis revealed compromised binding affinity for hBD-2 SNPs towards the SARS-CoV-2 spike domain. Different protein-protein binding profiles for hBD-2 SNPs, in relation to their native form, were guided through residue-wise levels and differential adopted conformation/orientation.

Conclusions

The presented model paves the way for identifying patients prone to COVID-19 in a way that would guide the personalization of both the diagnostic and management protocols for this serious disease.

Hydrophobic diversification is the key to simultaneously increased antifungal activity and decreased cytotoxicity of two ab initio designed peptides

The fact that some antimicrobial peptides have been utilized clinically and as food preservatives stimulated the efforts in search of new candidates. In our previous studies, we succeeded in designing potent peptides against methicillin-resistant Staphylococcus aureus (MRSA), severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2), and Ebola viruses based on the database filtering technology. The designed peptides were proved highly potent. However, this ab initio method has not been utilized to design antifungal peptides. This study report two novel antifungal peptides with 21 and 15 amino acids designed by more effectively extracting the most probable parameters from ∼1200 antifungal peptides in the antimicrobial peptide database (APD). Subsequent hydrophobic diversification led to two peptide variants with enhanced activity against four fungal strains but reduced cytotoxicity to four mammalian cell lines. DFTAFP-1A (KWSGAAAKKLKSLLSGLGKLL) and DFTAFP-2A (KWSGLLLKLGAASKL) retained activity against Zygosaccharomyces bailii at pH 5.6 and 6.3 or after autoclave. The peptides could permeabilize fungal membranes and adopted helical conformations in membrane mimetic micelles. Collectively, this study demonstrated not only the successful design of two novel antifungal peptides based on the APD database but also optimization of desired peptide properties. This improved database approach may be utilized to design useful peptides to combat other drug-resistant pathogens as well.

Vitamin D and COVID-19: Narrative Review after 3 Years of Pandemic

Active vitamin D [1,25(OH)₂D₃-calcitriol] is a secosteroid hormone whose receptor is expressed on all cells of the immune system. Vitamin D has a global anti-inflammatory effect and its role in the management of a SARS-CoV-2 infection has been investigated since the beginning of the COVID-19 pandemic. In this narrative review, the laboratory and clinical results of a vitamin D supplementation have been collected from both open-label and blinded randomized clinical trials. The results are generally in favor of the utility of maintaining the serum concentrations of calcifediol [25(OH)D₃] at around 40 ng/mL and of the absolute usefulness of its supplementation in subjects with deficient serum levels. However, two very recent large-scale studies (one open-label, one placebo-controlled) have called into question the contribution of vitamin D to clinical practice in the era of COVID-19 vaccinations. The precise role of a vitamin D supplementation in the anti-COVID-19 armamentarium requires further investigations in light of the breakthrough which has been achieved with mass vaccinations.

Does vitamin D supplementation reduce COVID-19 severity?: a systematic review

BACKGROUND

The evidence regarding the efficacy of vitamin D supplementation in reducing severity of COVID-19 is still insufficient. This is partially due to the lack of primary robust trial-based data and heterogeneous study designs.

AIM

This evidence summary, aims to study the effect of vitamin D supplementation on morbidity and mortality in hospitalized COVID-19 patients.Design: Evidence summary of systematic reviews.

METHODS

For this study, systematic reviews and meta-analysis published from December 2019 to January 2022 presenting the impact of vitamin D supplementation on COVID-19 severity were screened and selected from PubMed and Google scholar. After initial screening, 10 eligible reviews were identified and quality of included reviews were assessed using AMSTAR and GRADE tools and overlapping among the primary studies used were also assessed.

RESULTS

The number of primary studies included in the systematic reviews ranged from 3 to 13. Meta-analysis of seven systematic reviews showed strong evidence that vitamin D supplementation reduces the risk of mortality (Odds ratio: 0.48, 95% CI: 0.346-0.664; P < 0.001) in COVID patients. It was also observed that supplementation reduces the need for intensive care (Odds ratio: 0.35; 95%CI: 0.28-0.44; P < 0.001) and mechanical ventilation (Odds ratio: 0.54; 95% CI: 0.411-0.708; P < 0.001) requirement. The findings were robust and reliable as level of heterogeneity was considerably low. However the included studies were of varied quality. Qualitative analysis showed that supplements (oral and IV) are well tolerated, safe and effective in COVID patients.

CONCLUSION

The findings of this study show that vitamin D supplementation is effective in reducing the COVID-19 severity. Hence, vitamin D should be recommended as an adjuvant therapy for COVID-19.However, more robust and larger trials are required to substantiate it further.

Early Prediction of COVID-19 Patient Survival by Targeted Plasma Multi-Omics and Machine Learning

The recent surge of coronavirus disease 2019 (COVID-19) hospitalizations severely challenges healthcare systems around the globe and has increased the demand for reliable tests predictive of disease severity and mortality. Using multiplexed targeted mass spectrometry assays on a robust triple quadrupole MS setup which is available in many clinical laboratories, we determined the precise concentrations of hundreds of proteins and metabolites in plasma from hospitalized COVID-19 patients. We observed a clear distinction between COVID-19 patients and controls and, strikingly, a significant difference between survivors and nonsurvivors. With increasing length of hospitalization, the survivors' samples showed a trend toward normal concentrations, indicating a potential sensitive readout of treatment success. Building a machine learning multi-omic model that considers the concentrations of 10 proteins and five metabolites, we could predict patient survival with 92% accuracy (area under the receiver operating characteristic curve: 0.97) on the day of hospitalization. Hence, our standardized assays represent a unique opportunity for the early stratification of hospitalized COVID-19 patients.

Antimicrobial peptides: A promising tool to combat multidrug resistance in SARS CoV2 era

COVID-19 (Coronavirus Disease 2019), a life-threatening viral infection, is caused by a highly pathogenic virus named SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2). Currently, no treatment is available for COVID-19; hence there is an urgent need to find effective therapeutic drugs to combat COVID-19 pandemic. Considering the fact that the world is facing a major issue of antimicrobial drug resistance, naturally occurring compounds have the potential to achieve this goal. Antimicrobial peptides (AMPs) are naturally occurring antimicrobial agents which are effective against a wide variety of microbial infections. Therefore, the use of AMPs is an attractive therapeutic strategy for the treatment of SARS-CoV-2 infection. This review sheds light on the potential of antimicrobial peptides as antiviral agents followed by a comprehensive description of effective antiviral peptides derived from various natural sources found to be effective against SARS-CoV and other respiratory viruses. It also highlights the mechanisms of action of antiviral peptides with special emphasis on their effectiveness against SARS-CoV-2 infection.

In vitro Screening of Herbal Medicinal Products for Their Supportive Curing Potential in the Context of SARS-CoV-2

COVID-19 herbal medicinal products may have the potential for symptom relief in nonsevere or moderate disease cases. In this in vitro study we screened the five herbal medicinal products Sinupret extract (SINx), Bronchipret thyme-ivy (BRO-TE), Bronchipret thyme-primula (BRO TP), Imupret (IMU), and Tonsipret (TOP) with regard to their potential to (i) interfere with the binding of the human angiotensin-converting enzyme 2 (ACE2) receptor with the SARS-CoV-2 spike S1 protein, (ii) modulate the release of the human defensin HBD1 and cathelicidin LL-37 from human A549 lung cells upon spike S1 protein stimulation, and (iii) modulate the release of IFN-γ from activated human peripheral blood mononuclear cells (PBMC). The effect of the extracts on the interaction of spike S1 protein and the human ACE2 receptor was measured by ELISA. The effects on the intracellular IFN-γ expression in stimulated human PBMC were measured by flow cytometry. Regulation of HBD1 and LL-37 expression and secretion was assessed in 25 d long-term cultured human lung A549 epithelial cells by RT-PCR and ELISA. IMU and BRO-TE concentration-dependently inhibited the interaction between spike S1 protein and the ACE2 receptor. SINx, TOP, and BRO-TE significantly upregulated the intracellular expression of anti-viral IFN-γ from stimulated PBMC. Cotreatment of A549 cells with IMU or BRO TP together with SARS-CoV-2 spike protein significantly upregulated mRNA expression (IMU) and release of HBD1 (IMU and BRO TP) and LL-37 (BRO TP). The in vitro screening results provide first evidence for an immune-activating potential of some of the tested herbal medicinal extracts in the context of SARS-CoV-2. Whether these could be supportive in symptom relief or curing from SARS-CoV-2 infection needs deeper understanding of the observations.

Human ACE2 Peptide-Attached Plasmonic-Magnetic Heterostructure for Magnetic Separation, Surface Enhanced Raman Spectroscopy Identification, and Inhibition of Different Variants of SARS-CoV-2 Infections

The emergence of Alpha, Beta, Gamma, Delta, and Omicron variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for several million deaths up to now. Because of the huge amount of vaccine escape mutations in the spike (S) protein for different variants, the design of material for combating SARS-CoV-2 is very important for our society. Herein, we report on the design of a human angiotensin converting enzyme 2 (ACE2) peptide-conjugated plasmonic-magnetic heterostructure, which has the capability for magnetic separation, identification via surface enhanced Raman spectroscopy (SERS), and inhibition of different variant SARS-CoV-2 infections. In this work, plasmonic-magnetic heterostructures were developed using the initial synthesis of polyethylenimine (PEI)-coated Fe3O4-based magnetic nanoparticles, and then gold nanoparticles (GNPs) were grown onto the surface of the magnetic nanoparticles. Experimental binding data between ACE2-conjugated plasmonic-magnetic heterostructures and spike-receptor-binding domain (RBD) show that the Omicron variant has maximum binding ability, and it follows Alpha < Beta < Gamma < Delta < Omicron. Our finding shows that, due to the high magnetic moment (specific magnetization 40 emu/g), bioconjugated heterostructures are capable of effective magnetic separation of pseudotyped SARS-CoV-2 bearing the Delta variant spike from an infected artificial nasal mucus fluid sample using a simple bar magnet. Experimental data show that due to the formation of huge "hot spots" in the presence of SARS-CoV-2, Raman intensity for the 4-aminothiolphenol (4-ATP) Raman reporter was enhanced sharply, which has been used for the identification of separated virus. Theoretical calculations using finite-difference time-domain (FDTD) simulation indicate that, due to the "hot spots" formation, a six orders of magnitude Raman enhancement can be observed. A concentration-dependent inhibition efficiency investigation using a HEK293T-human cell line indicates that ACE2 peptide-conjugated plasmonic-magnetic heterostructures have the capability of complete inhibition of entry of different variants and original SARS-CoV-2 pseudovirions into host cells.

LL-37, a Multi-Faceted Amphipathic Peptide Involved in NETosis

Innate immunity responds to infections and inflammatory stimuli through a carefully choreographed set of interactions between cells, stimuli and their specific receptors. Of particular importance are endogenous peptides, which assume roles as defensins or alarmins, growth factors or wound repair inducers. LL-37, a proteolytic fragment of cathelicidin, fulfills the roles of a defensin by inserting into the membranes of bacterial pathogens, functions as alarmin in stimulating chemotaxis of innate immune cells, and alters the structure and efficacy of various cytokines. Here, we draw attention to the direct effect of LL-37 on neutrophils and the release of extracellular traps (NETs), as NETs have been established as mediators of immune defense against pathogens but also as important contributors to chronic disease and tissue pathogenesis. We propose a specific structural basis for LL-37 function, in part by highlighting the structural flexibility of LL-37 and its ability to adapt to distinct microenvironments and interacting counterparts.

Vitamin D and the Ability to Produce 1,25(OH)2D Are Critical for Protection from Viral Infection of the Lungs

Vitamin D supplementation is linked to improved outcomes from respiratory virus infection, and the COVID-19 pandemic renewed interest in understanding the potential role of vitamin D in protecting the lung from viral infections. Therefore, we evaluated the role of vitamin D using animal models of pandemic H1N1 influenza and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. In mice, dietary-induced vitamin D deficiency resulted in lung inflammation that was present prior to infection. Vitamin D sufficient (D+) and deficient (D-) wildtype (WT) and D+ and D- Cyp27B1 (Cyp) knockout (KO, cannot produce 1,25(OH)2D) mice were infected with pandemic H1N1. D- WT, D+ Cyp KO, and D- Cyp KO mice all exhibited significantly reduced survival compared to D+ WT mice. Importantly, survival was not the result of reduced viral replication, as influenza M gene expression in the lungs was similar for all animals. Based on these findings, additional experiments were performed using the mouse and hamster models of SARS-CoV-2 infection. In these studies, high dose vitamin D supplementation reduced lung inflammation in mice but not hamsters. A trend to faster weight recovery was observed in 1,25(OH)2D treated mice that survived SARS-CoV-2 infection. There was no effect of vitamin D on SARS-CoV-2 N gene expression in the lung of either mice or hamsters. Therefore, vitamin D deficiency enhanced disease severity, while vitamin D sufficiency/supplementation reduced inflammation following infections with H1N1 influenza and SARS-CoV-2.

Vitamin D boosts immune response of macrophages through a regulatory network of microRNAs and mRNAs

Vitamin D is associated with the stimulation of innate immunity, inflammation, and host defense against pathogens. Macrophages express receptors of Vitamin D, regulating transcription of genes related to immune processes. However, the transcriptional and post-transcriptional strategies controlling gene expression in differentiated macrophages, and how they are influenced by Vitamin D are not well understood. We studied whether Vitamin D enhances immune response by regulating the expression of microRNAs and mRNAs. Analysis of the transcriptome showed differences in expression of 199 genes, of which 68% were up-regulated, revealing the cell state of monocyte-derived macrophages differentiated with Vitamin D (D3-MDMs) as compared to monocyte-derived macrophages (MDMs). The differentially expressed genes appear to be associated with pathophysiological processes, including inflammatory responses, and cellular stress. Transcriptional motifs in promoter regions of up- or down-regulated genes showed enrichment of VDR motifs, suggesting possible roles of transcriptional activator or repressor in gene expression. Further, microRNA-Seq analysis indicated that there were 17 differentially expressed miRNAs, of which, 7 were up-regulated and 10 down-regulated, suggesting that Vitamin D plays a critical role in the regulation of miRNA expression during macrophages differentiation. The miR-6501-3p, miR-1273h-5p, miR-665, miR-1972, miR-1183, miR-619-5p were down-regulated in D3-MDMs compared to MDMs. The integrative analysis of miRNA and mRNA expression profiles predict that miR-1972, miR-1273h-5p, and miR-665 regulate genes PDCD1LG2, IL-1B, and CD274, which are related to the inflammatory response. Results suggest an essential role of Vitamin D in macrophage differentiation that modulates host response against pathogens, inflammation, and cellular stress.

The ratio of serum LL-37 levels to blood leucocyte count correlates with COVID-19 severity

Beneficial effects of vitamin D on COVID-19 progression have been discussed in several studies. Vitamin D stimulates the expression of the antimicrobial peptide LL-37, and evidence shows that LL-37 can antagonize SARS-CoV-2. Therefore, we investigated the association between LL-37 and vitamin D serum levels and the severity of COVID-19. To this end, 78 COVID-19 patients were divided into 5 groups according to disease severity. We determined serum levels of LL-37, vitamin D, and routine laboratory parameters. We demonstrated a correlation of CRP, IL-6, PCT, leukocyte count, and LDH with the severity of COVID-19. Our study did not demonstrate a direct relationship between serum levels of LL-37 and vitamin D and the severity of COVID-19. LL-37 is produced by granulocytes and released at the site of inflammation. Therefore, the analysis of LL-37 in broncho-alvelolar lavage rather than in patient serum seems critical. However, since LL-37 is produced by granulocytes, we determined serum LL-37 levels as a function of leukocyte count. The LL-37/leukocyte count ratio correlates highly significantly inversely proportional with COVID-19 severity. Our results indicate that the LL-37/leukocyte count ratio could be used to assess the risk of COVID-19 progression as early as hospital admission.

Circulating biomarkers of inflammaging as potential predictors of COVID-19 severe outcomes

The COVID-19 pandemic caused by SARS-CoV-2 infection has been of unprecedented clinical and socio-economic worldwide relevance. The case fatality rate for COVID-19 grows exponentially with age and the presence of comorbidities. In the older patients, COVID-19 manifests predominantly as a systemic disease associated with immunological, inflammatory, and procoagulant responses. Timely diagnosis and risk stratification are crucial steps to define appropriate therapies and reduce mortality, especially in the older patients. Chronically and systemically activated innate immune responses and impaired antiviral responses have been recognized as the results of a progressive remodeling of the immune system during aging, which can be described by the words 'immunosenescence' and 'inflammaging'. These age-related features of the immune system were highlighted in patients affected by COVID-19 with the poorest clinical outcomes, suggesting that the mechanisms underpinning immunosenescence and inflammaging could be relevant for COVID-19 pathogenesis and progression. Increasing evidence suggests that senescent myeloid and endothelial cells are characterized by the acquisition of a senescence-associated pro-inflammatory phenotype (SASP), which is considered as the main culprit of both immunosenescence and inflammaging. Here, we reviewed this evidence and highlighted several circulating biomarkers of inflammaging that could provide additional prognostic information to stratify COVID-19 patients based on the risk of severe outcomes.

Role of LL-37 in thrombotic complications in patients with COVID-19

Blood clot formation induced by dysfunctional coagulation is a frequent complication of coronavirus disease 2019 (COVID-19) and a high-risk factor for severe illness and death. Neutrophil extracellular traps (NETs) are implicated in COVID-19-induced immunothrombosis. Furthermore, human cathelicidin, a NET component, can perturb the interaction between the SARS-CoV-2 spike protein and its ACE2 receptor, which mediates viral entry into cells. At present, however, the levels of cathelicidin antimicrobial peptides after SARS-CoV-2 infection and their role in COVID-19 thrombosis formation remain unclear. In the current study, we analyzed coagulation function and found a decrease in thrombin time but an increase in fibrinogen level, prothrombin time, and activated partial thromboplastin time in COVID-19 patients. In addition, the cathelicidin antimicrobial peptide LL-37 was upregulated by the spike protein and significantly elevated in the plasma of patients. Furthermore, LL-37 levels were negatively correlated with thrombin time but positively correlated with fibrinogen level. In addition to platelet activation, cathelicidin peptides enhanced the activity of coagulation factors, such as factor Xa (FXa) and thrombin, which may induce hypercoagulation in diseases with high cathelicidin peptide levels. Injection of cathelicidin peptides promoted the formation of thrombosis, whereas deletion of cathelicidin inhibited thrombosis in vivo. These results suggest that cathelicidin antimicrobial peptide LL-37 is elevated during SARS-CoV-2 infection, which may induce hypercoagulation in COVID-19 patients by activating coagulation factors.

Upregulating Human Cathelicidin Antimicrobial Peptide LL-37 Expression May Prevent Severe COVID-19 Inflammatory Responses and Reduce Microthrombosis

COVID-19 is characterized by hyperactivation by inflammatory cytokines and recruitment of macrophages, neutrophils, and other immune cells, all hallmarks of a strong inflammatory response that can lead to severe complications and multi-organ damage. Mortality in COVID-19 patients is associated with a high prevalence of neutrophil extracellular trap (NET) formation and microthrombosis that are exacerbated by hyperglycemia, diabetes, and old age. SARS-CoV-2 infection in humans and non-human primates have revealed long-term neurological consequences of COVID-19, possibly concomitant with the formation of Lewy bodies in the brain and invasion of the nervous system via the olfactory bulb. In this paper, we review the relevance of the human cathelicidin LL-37 in SARS-CoV-2 infections. LL-37 is an immunomodulatory, host defense peptide with direct anti-SARS-CoV-2 activity, and pleiotropic effects on the inflammatory response, neovascularization, Lewy body formation, and pancreatic islet cell function. The bioactive form of vitamin D and a number of other compounds induce LL-37 expression and one might predict its upregulation, could reduce the prevalence of severe COVID-19. We hypothesize upregulation of LL-37 will act therapeutically, facilitating efficient NET clearance by macrophages, speeding endothelial repair after inflammatory tissue damage, preventing α-synuclein aggregation, and supporting blood-glucose level stabilization by facilitating insulin release and islet β-cell neogenesis. In addition, it has been postulated that LL-37 can directly bind the S1 domain of SARS-CoV-2, mask angiotensin converting enzyme 2 (ACE2) receptors, and limit SARS-CoV-2 infection. Purposeful upregulation of LL-37 could also serve as a preventative and therapeutic strategy for SARS-CoV-2 infections.

Allosteric control of ACE2 peptidase domain dynamics

The Angiotensin Converting Enzyme 2 (ACE2) assists the regulation of blood pressure and is the main target of the coronaviruses responsible for SARS and COVID19. The catalytic function of ACE2 relies on the opening and closing motion of its peptidase domain (PD). In this study, we investigated the possibility of allosterically controlling the ACE2 PD functional dynamics. After confirming that ACE2 PD binding site opening-closing motion is dominant in characterizing its conformational landscape, we observed that few mutations in the viral receptor binding domain fragments were able to impart different effects on the binding site opening of ACE2 PD. This showed that binding to the solvent exposed area of ACE2 PD can effectively alter the conformational profile of the protein, and thus likely its catalytic function. Using a targeted machine learning model and relative entropy-based statistical analysis, we proposed the mechanism for the allosteric perturbation that regulates the ACE2 PD binding site dynamics at atomistic level. The key residues and the source of the allosteric regulation of ACE PD dynamics are also presented.