Vitamin D receptor (VDR), influenced by gene polymorphisms like FokI, may affect susceptibility to infections, including coronavirus disease 2019 (COVID-19). Since studies in children are limited, we aimed to analyze the correlation between the VDR FokI variant and both the incidence and severity of COVID-19 in Egyptian children.

Seventy-seven COVID-19-positive and 107 COVID-19-negative pediatric patients were included. Participants' serum 25(OH)D levels, inflammatory biomarkers, and demographics were evaluated. Real-time polymerase chain reaction (PCR) was used for genotyping the VDR FokI (rs2228570) polymorphism.

Absolute lymphocyte count (ALC) was significantly lower in COVID-19 patients than in controls, while interleukin-6 (IL-6), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), procalcitonin, and D-dimer were significantly higher (all p < 0.001). Vitamin D insufficiency was significantly more common in COVID-19 cases (18.2 % versus 3.7 %, p = 0.002). Male sex, increased tumor necrosis factor-alpha (TNF-α), and CRP were significantly associated with severe COVID-19 (p = 0.032, 0.029, < 0.001, respectively). The FokI TT genotype in codominant and recessive models and the T allele in the multiplicative model were significantly correlated with 2.4, 3.0, and 1.8 folds increased COVID-19 risk (p = 0.043, < 0.001, and 0.004, respectively). However, VDR FokI variants did not significantly associate with severe COVID-19.

The T allele and TT genotype of the FokI variant in the VDR gene increase susceptibility to COVID-19 but not its severity in Egyptian children. Additional research is required to validate the potential role of vitamin D and its receptor polymorphism in COVID-19.

COVID-19 is a disease caused by SARS-CoV-2. It became a health problem affecting the lives of millions of people. Toll-like receptors are responsible for recognizing viral particles and activating the innate immune system. The genetic factors associated with COVID-19 remain unclear. Thus, this study aims to assess the association between the polymorphism in Toll-like receptors and susceptibility to COVID-19. We searched the electronic databases (Science Direct, PUBMED, Web of Science, and Scopus) for studies assessing the association between Toll-like receptor polymorphisms and susceptibility to COVID-19. The quality of the studies was assessed using the Q-Genie tool. Thirteen studies were included in this systematic review. The studies analyzed polymorphisms in TLR2, TLR3, TLR4, TLR7, TLR8 and TLR9. We used SNP2TFBS bioinformatic analysis to identify the variants influencing transcription factor binding sites. The Ensembl Genome Browser was used to assess the allele and genotype frequencies in different populations. The bioinformatic analysis revealed that the variant rs5743836 of TLR9 affects the transcription factor binding sites NFKB1 and RELA. The genotype frequency of the variants rs3775291, rs3853839, rs3764880 were higher in East Asian population compared to the other populations. The frequency of the rs3775290 variant was higher in East and South Asian populations. The rs179008 variant was higher in the European population, and the rs5743836 was higher in the African population. Toll-like receptors play an important role in COVID-19 susceptibility. Further studies in different populations are necessary to elucidate the role of Toll-like receptors polymorphisms in SARS-CoV-2 infection.

COVID-19 patients face an increased risk of thromboembolic complications, yet the exact pathophysiological role of platelets in the disease remains unclear. Considering the multifaceted nature of COVID-19 symptoms, including platelet hyperactivation and inflammation, the development of compounds that simultaneously target both represents a promising therapeutic strategy. The monoterpene 1.8-cineole (CNL-1976) is known for its anti-inflammatory and anti-aggregatory effects. Thus, understanding the mechanism behind platelet hyperactivation and the effect of 1.8-cineole during COVID-19 is crucial when aiming for a reduction of disease severity. In this study, we investigated the mechanism of platelet activation triggered by the SARS-CoV-2 S1 spike protein (S1). Utilizing S1-coupled beads, we discovered that platelet activation and aggregation were dependent on plasma components, particularly S1-specific IgG antibodies. The formation of immune complexes through IgG binding to S1 facilitated the crosslinking of the platelet expressed FcγRIIa receptor, initiating platelet activation and aggregation, as well as formation of platelet-leukocyte aggregates (PLAs). Importantly, treatment with 1.8-cineole significantly inhibited S1-bead-induced platelet activity and PLA formation. These findings strongly suggest that antibody-mediated platelet activation via FcγRIIa directly contributes to the well-recognized prothrombotic environment during COVID-19. Moreover, our data indicate that 1.8-cineole can serve as a potential therapeutic compound, alleviating platelet-driven thromboinflammatory complications associated with COVID-19 and post-acute sequelae of SARS-CoV-2 (PASC).

Enterotoxigenic Escherichia coli (ETEC) is one of the primary pathogens causing diarrhea in piglets, causing significant economic losses in the swine farming industry. Due to the numerous serotypes of ETEC, traditional vaccines fail to provide sufficient cross-protection, and subunit vaccines based on epitope design have emerged as a safer and more effective approach for prevention and control. Unlike vaccine development strategies that involve the tandem arrangement of multiple antigenic epitopes, this study used the K88-FaeG protein as a backbone and incorporated the antigenic epitopes of K99-FanC to achieve a better immunogenicity. By using bioinformatics software to predict B-cell linear epitopes (score of over 0.6), B-cell epitopes from three-dimensional structures (50% amino acid score of ≥0.2), and B-cell epitope IgG antibody subtypes, as well as docking analysis with Sus scrofa aminopeptidase N (APN) receptors, six antigenic epitopes of K99-FanC were selected. Through Western blotting and competitive ELISA, we confirmed that all six recombinant proteins exhibited binding capabilities to K88- and K99-positive serum. The ELISA results showed that the serum levels of specific IgG and IgA antibodies increased after immunization, with FaeG-Ep3 and FaeG-Ep5 inducing the highest antibody titers against FanC-IgG (Log2 = 14.96) and FaeG-IgG (Log2 = 17.96), respectively. Bacterial adhesion assays revealed that only FaeG-Ep3 effectively blocked the adhesion of both K99 and K88 to IPEC-J2 cells. Immunization challenge experiments showed that, in the unimmunized group, mice infected with K88 and K99 experienced weight loss (p < 0.05) with intestinal villus shedding and intestinal wall structural damage. However, in the FaeG-Ep3-immunized group, no significant weight loss occurred after infection, and the villus protection rate (83%) was the same as that in the FaeG and FanC immunized groups. Overall, the FaeG-Ep3 recombinant protein identified in this study shows potential vaccine application value and provides new insights for developing multivalent vaccines against ETEC.

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.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can lead to severe coronavirus disease 2019 (COVID-19), which is characterized by cytokine storm and organ dysfunction. The spike S1 subunit induces inflammatory cytokine production, but the immune cell subsets that respond to S1 stimulation and contribute to disease severity remain unclear.

We analyzed serum samples and peripheral blood mononuclear cells (PBMCs) from patients with COVID-19 (moderate: n = 7; severe: n = 25) and healthy controls (n = 38). Using mass cytometry (cytometry by time-of-flight; CyTOF), we analyzed immune cell responses to S1 subunit stimulation in PBMCs from healthy donors and patients with COVID-19. We examined correlations among identified cell populations, serum cytokine levels, and clinical parameters.

Serum S1 subunit levels correlated with disease severity and inflammatory cytokine concentrations. S1 subunit stimulation induced dose-dependent cytokine production from PBMCs, predominantly from myeloid cells. CyTOF analysis identified classical monocytes with high CD147 expression (CD147hi cMono) as the primary source of S1-induced cytokines. The proportion of CD147hi cMono increased significantly in severe COVID-19 and decreased with clinical improvement. The frequency of CD147hi cMono showed a stronger positive correlation with clinical severity markers in younger patients compared to older patients.

CD147hi cMono are the primary cellular source of S1-induced inflammatory cytokines and may serve as potential biomarkers for monitoring COVID-19 severity and treatment response.

The coronavirus disease-19 (COVID-19) pandemic has been a very significant health issue in the period between 2020 and 2023, forcing research to characterize severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequences and to develop novel therapeutic approaches. Interleukin-6 (IL-6) and IL-8 are considered significant therapeutic targets for COVID-19 and emerging evidence has suggested that microRNAs (miRNAs/miRs) serve a key role in regulating these genes. MiRNAs are short, 19-25 nucleotides in length, non-coding RNAs that regulate gene expression at the post-transcriptional level through the sequence-selective recognition of the 3'-untranslated region (3'-UTR) of the regulated mRNAs, eventually repressing translation, commonly, via mRNA degradation. For example, among several miRNAs involved in the regulation of the COVID-19 'cytokine storm', miR-93-5p can inhibit IL-8 gene expression by directly targeting the 3'-UTR of IL-8 mRNA. In addition, miR-93-5p can regulate Toll-like receptor-4 (TLR4) and interleukin-1 receptor-associated kinase 4 (IRAK4) expression, thus affecting the nuclear factor-κB (NF-κB) pathway and the expression of NF-κB-regulated genes, such as IL-6, IL-1β and other hyper-expressed genes during the COVID-19 'cytokine storm'. In the present study, the results provided preliminary evidence suggesting that the miR-93-5p-based miRNA therapeutics could be combined with the anti-inflammatory aged garlic extract (AGE) to more effectively inhibit IL-8 gene expression. The human bronchial epithelial IB3-1 cell line was employed as experimental model system. IB3-1 cells were stimulated with the BNT162b2 COVID-19 vaccine and transfected with pre-miR-93-5p in the absence or in the presence of AGE, to verify the inhibitory effects on the BNT162b2-induced expression of the IL-8 gene. The accumulation of IL-8 mRNA was assessed by RT-qPCR; the release of IL-8 protein was determined by Bio-Plex assay. In addition, the possible applications of TLR4/NF-κB inhibitory agents (such as miR-93-5p and AGE) for treating human pathologies at a hyperinflammatory state, such as COVID-19, cystic fibrosis and other respiratory diseases, were summarized.

Various pattern recognition receptors (PRRs), including toll-like receptors (TLRs), play a crucial role in recognizing invading pathogens as well as damage-associated molecular patterns (DAMPs) released in response to infection. The resulting signaling cascades initiate appropriate immune responses to eliminate these pathogens. Current evidence suggests that SARS-CoV-2-driven activation of TLR4, whether through direct recognition of the spike glycoprotein (alone or in combination with endotoxin) or by sensing various TLR4-activating DAMPs or alarmins released during viral infection, acts as a critical mediator of antiviral immunity. However, TLR4 exerts a dual role in COVID-19, demonstrating both beneficial and deleterious effects. Dysregulated TLR4 signaling is implicated in the proinflammatory consequences linked to the immunopathogenesis of COVID-19. Additionally, TLR4 polymorphisms contribute to severity of the disease. Given its significant immunoregulatory impact on COVID-19 immunopathology and host immunity, TLR4 has emerged as a key target for developing inhibitors and immunotherapeutic strategies to mitigate the adverse effects associated with SARS-CoV-2 and related infections. Furthermore, TLR4 agonists are also being explored as adjuvants to enhance immune responses to SARS-CoV-2 vaccines.

The objective of this study was to better understand immune failure mechanisms during severe acute respiratory syndrome coronavirus 2, SARS-CoV-2 infection, which are critical for developing targeted vaccines and effective treatments. We collected 34 cases representing different disease severities and performed high-quality single-cell TCR/BCR sequencing to analyze the peripheral immune cell profiles. Additionally, we assessed antibody-neutralizing activity through in vitro experiments. Our integrated multiomics analysis uncovers a profound immune paradox in severe COVID-19: hyperinflammation coexists with immunosuppression, driven by distinct yet interconnected dysregulatory mechanisms. Severe patients develop robust humoral immunity, evidenced by clonally expanded plasma cells producing neutralizing antibodies (e.g., IGHG1-dominated responses) and antigen-specific T cell activation. However, these protective responses are counteracted by myeloid-driven immunosuppression, particularly CD14+ HMGB2+ monocytes exhibiting metabolic reprogramming and HLA-DR downregulation, coupled with progressive T cell exhaustion characterized by IFN-γ/TNF-α hyperactivation and impaired antigen presentation. Importantly, prolonged viral persistence in severe cases arises from a failure to coordinate humoral and cellular immunity-antibody-mediated neutralization cannot compensate for defective cytotoxic T cell function and monocyte-mediated immune suppression. These findings highlight the necessity for therapeutic strategies that simultaneously enhance antibody effector functions (e.g., Fc optimization), restore exhausted T cells, and reverse myeloid suppression. They also highlight the importance of vaccines designed to elicit balanced B cell memory and durable T cell responses, which are critical to preventing severe disease progression. By addressing the dual challenges of hyperinflammation and immunosuppression, such approaches could restore immune coordination and improve outcomes in severe COVID-19.

A cytokine storm is marked by excessive pro-inflammatory cytokine release, and has emerged as a key factor in severe COVID-19 cases - making it a critical therapeutic target. However, its pathophysiology was poorly understood, which hindered effective treatment. SARS-CoV-2 initially disrupts angiotensin signalling, promoting inflammation through ACE-2 downregulation. Some patients' immune systems then fail to shift from innate to adaptive immunity, suppressing interferon responses and leading to excessive pyroptosis and neutrophil activation. This amplifies tissue damage and inflammation, creating a pro-inflammatory loop. The result is the disruption of Th1/Th2 and Th17/Treg balances, lymphocyte exhaustion, and extensive blood clotting. Cytokine storm treatments include glucocorticoids to suppress the immune system, monoclonal antibodies to neutralize specific cytokines, and JAK inhibitors to block cytokine receptor signalling. However, the most effective treatment options for mitigating SARS-CoV-2 infection remain vaccines as a preventive measure and antiviral drugs for the early stages of infection. This article synthesizes insights into immune dysregulation in COVID-19, offering a framework to better understand cytokine storms and to improve monitoring, biomarker discovery, and treatment strategies for COVID-19 and other conditions involving cytokine storms.

SARS-CoV-2, first identified in late 2019, has given rise to numerous variants of concern (VOCs), posing a significant threat to human health. The emergence of Omicron BA.1.1 towards the end of 2021 led to a pandemic in early 2022. At present, the lethal mouse model for the study of SARS-CoV-2 needs supplementation, and the alterations in neutrophils and monocytes caused by different strains remain to be elucidated.

Human ACE2 transgenic mice were inoculated with the SARS-CoV-2 prototype and Omicron BA.1, respectively. The pathogenicity of the two strains was evaluated by observing clinical symptoms, viral load and pathology. Complete blood count, immunohistochemistry and flow cytometry were performed to detect the alterations of neutrophils and monocytes caused by the two strains.

Our findings revealed that Omicron BA.1 exhibited significantly lower virulence compared to the SARS-CoV-2 prototype in the mouse model. Additionally, we observed a significant increase in the proportion of neutrophils late in infection with the SARS-CoV-2 prototype and Omicron BA.1. We found that the proportion of monocytes increased at first and then decreased. The trends in the changes in the proportions of neutrophils and monocytes induced by the two strains were similar.

Our study provides valuable insights into the utility of mouse models for simulating the severe disease of SARS-CoV-2 prototype infection and the milder manifestation associated with Omicron BA.1. SARS-CoV-2 prototype and Omicron BA.1 resulted in similar trends in the changes in neutrophils and monocytes.

Our research is driven by the need to design an advanced multi-epitope vaccine construct (MEVC) using the S-protein of SARS-CoV-2 to combat the emergence of new variants. Through rigorous computational screening, we have identified linear and discontinuous B-cell epitopes, CD8 + and CD4 + T-cell epitopes, ensuring extensive MEVC coverage across 90.03% of the global population. The MEVC, featuring four CD4 + and four CD8 + T-cell epitopes connected linearly with two adjuvant proteins on both ends, has been carefully designed to elicit robust immune response. Our in-silico analysis has confirmed the construct's antigenicity, non-allergenicity, and non-toxicity with optimized codon sequences for enhanced expression in E. coli K12. Furthermore, molecular docking and dynamics analyses have demonstrated its strong binding affinity with TLR-3 and TLR 4, and in-silico immune simulation yielded promising results on heightened B-cell and T-cell-mediated immunity. However, wet lab experiments are essential to validate computational findings to revolutionize the development of vaccines against SARS-CoV-2.

Kingella kingae is a Gram-negative bacterium that causes invasive infections in children and older or immunocompromised individuals, making it a significant public health concern. In this study, a pan-proteomic mediated vaccine target mining was attempted to identify potential vaccine targets in K. kingae. Currently, there is no vaccine available against this pathobiont. Therefore, we designed and validated an in silico vaccine construct by targeting the lactoferrin/transferrin-binding TonB-dependent receptor. Antigenic regions of the TonB receptor were mapped, and the predicted epitopes were anticipated to be effective in a broad range of the world population. Using their combinations with linkers and various adjuvants, 12 vaccine constructs were prepared. The best construct (C7) with no allergenicity and high antigenicity was subjected to molecular modeling, docking with important immune receptors of humans, and then molecular dynamics (MD) simulation. After binding validation and stability assessment, it was cloned into a pet-28a + plasmid vector. Immune response was also simulated, and the vaccine was observed to invoke B- and T-cell induction. These findings can help accelerate the development of a new vaccine against K. kingae or other pathogens targeting the homolog of TonB. Nevertheless, we propose additional testing of C7 construct for efficacy and safety in vitro and in vivo.

Recent emergence of zoonotic monkeypox virus (Mpox) in human has triggered the virologists to develop plausible preventive measures. Hitherto, our understanding on the mechanism of immunopathogenesis of Mpox infection is elusive. However, available experimental evidences suggest induction of inflammation as the main cause of pathogenesis. Toll-like receptors (TLRs) are critical in initiating and modulating the host immune response to pathogens. Inflammatory responses observed in various poxvirus infections have, in fact, been shown to be mediated through TLR activation. Therefore, by in silico approaches, this study seeks to identify the Mpox antigen(s) (MAg) that are most likely to interact with human cell-surface TLRs. The Mpox proteomics data available in UniProt database contain 174 protein sequences, among which 105 immunoreactive proteins were modeled for 3D structure and examined for comparative protein-protein interactions with the TLRs through molecular docking and molecular dynamics simulation. F14, an 8.28 kDa infective protein of Mpox, was found to exhibit strong binding affinity (ΔG=-12.5 Kcal mol-1) to TLR1/2 dimer to form a compact thermodynamically stable protein complex. Interestingly, a significant level of conformational change was also observed in both F14 and TLR6 while forming F14-TLR1/2 complex. Based on these data we propose F14 as a putative ligand of human TLR1/2 to initiate proinflammatory signaling in the Mpox-infected host.

Severe acute respiratory syndrome coronavirus (SARS-CoV), the virus responsible for COVID-19, interacts with the host immune system through complex mechanisms that significantly influence disease outcomes, affecting both innate and adaptive immunity. These interactions are crucial in determining the disease's severity and the host's ability to clear the virus. Given the virus's substantial socioeconomic impact, high morbidity and mortality rates, and public health importance, understanding these mechanisms is essential. This article examines the diverse innate immune responses triggered by SARS-CoV-2's structural proteins, including the spike (S), membrane (M), envelope (E), and nucleocapsid (N) proteins, along with nonstructural proteins (NSPs) and open reading frames. These proteins play pivotal roles in immune modulation, facilitating viral replication, evading immune detection, and contributing to severe inflammatory responses such as cytokine storms and acute respiratory distress syndrome (ARDS). The virus employs strategies like suppressing type I interferon production and disrupting key antiviral pathways, including MAVS, OAS-RNase-L, and PKR. This study also explores the immune pathways that govern the activation and suppression of immune responses throughout COVID-19. By analyzing immune sensing receptors and the responses initiated upon recognizing SARS-CoV-2 structural proteins, this review elucidates the complex pathways associated with the innate immune response in COVID-19. Understanding these mechanisms offers valuable insights for therapeutic interventions and informs public health strategies, contributing to a deeper understanding of COVID-19 immunopathogenesis.

In public health emergencies, viral diseases like influenza and COVID-19 have become a major concern. One of the proposed responses to this concern is the use of probiotics. Probiotics have a potent role in arming our bodies to combat viral infections. They affect the innate and adaptive immune systems in various ways. Accumulating studies has shown that probiotics can reduce the possibility of infection or the duration of respiratory symptoms by modulating the functions of the immune system. This review aims to summarize the impacts of probiotics on respiratory viral infections and their potential antiviral mechanisms. Therefore, we herein discussed probiotics in relation to lung immunity, distinct types of respiratory viral infections (VRIs), including influenza, rhinoviruses, respiratory syncytial virus, and upper respiratory viral infections, and lastly, probiotics and their effects on COVID-19. However, more studies are needed to explore the antiviral mechanisms of probiotics.

The initial interaction between COVID-19 and the human body involves the receptor-binding domain (RBD) of the viral spike protein with the angiotensin-converting enzyme 2 (ACE2) receptor. Likewise, the spike protein can engage with immune-related proteins, such as toll-like receptors (TLRs) and pulmonary surfactant proteins A (SP-A) and D (SP-D), thereby triggering immune responses. In this study, we utilize computational methods to investigate the interactions between the spike protein and TLRs (specifically TLR2 and TLR4), as well as (SP-A) and (SP-D). The study is conducted on four variants of concern (VOC) to differentiate and identify common virus behaviours. An assessment of the structural stability of various variants indicates slight changes attributed to mutations, yet overall structural integrity remains preserved. Our findings reveal the spike protein's ability to bind with TLR4 and TLR2, prompting immune activation. In addition, our in-silico results reveal almost similar docking scores and therefore affinity for both ACE2-spike and TLR4-spike complexes. We demonstrate that even minor changes due to mutations in all variants, surfactant A and D proteins can function as inhibitors against the spike in all variants, hindering the ACE2-RBD interaction.Communicated by Ramaswamy H. Sarma.

The interactions between viruses and the host immune response are nuanced and intricate. The cytokine response arguably plays a central role in dictating the outcome of virus infection, balancing inflammation, and healing, which is crucial to resolving infection without destructive immunopathologies.

Early innate immune responses are key to the generation of a beneficial or detrimental immune response. These initial responses are regulated by a plethora of surface bound, endosomal, and cytoplasmic innate immune receptors known as pattern recognition receptors. Of these, the Toll-like receptors (TLRs) play an important role in the induction of cytokines during virus infection. Recognizing pathogen-associated molecular patterns (PAMPs) such as viral proteins and/or nucleotide sequences, the TLRs act as sentinels for the initiation and propagation of immune responses.

TLRs are important receptors for initiating the innate response to single-stranded RNA (ssRNA) viruses like influenza A virus (IAV), severe acute respiratory syndrome coronavirus-1 (SARS-CoV-1), SARS-CoV-2, Middle East respiratory syndrome coronavirus, dengue virus, and Ebola virus. Infection with these viruses is also associated with aberrant expression of proinflammatory cytokines that contribute to a harmful cytokine storm response. Herein we discuss the connections between these ssRNA viruses, cytokine storm, and the roles of TLRs.

The interactions between viruses and the host immune response are nuanced and intricate. The cytokine response arguably plays a central role in dictating the outcome of virus infection, balancing inflammation, and healing, which is crucial to resolving infection without destructive immunopathologies.

Early innate immune responses are key to the generation of a beneficial or detrimental immune response. These initial responses are regulated by a plethora of surface bound, endosomal, and cytoplasmic innate immune receptors known as pattern recognition receptors. Of these, the Toll-like receptors (TLRs) play an important role in the induction of cytokines during virus infection. Recognizing pathogen-associated molecular patterns (PAMPs) such as viral proteins and/or nucleotide sequences, the TLRs act as sentinels for the initiation and propagation of immune responses.

TLRs are important receptors for initiating the innate response to single-stranded RNA (ssRNA) viruses like influenza A virus (IAV), severe acute respiratory syndrome coronavirus-1 (SARS-CoV-1), SARS-CoV-2, Middle East respiratory syndrome coronavirus, dengue virus, and Ebola virus. Infection with these viruses is also associated with aberrant expression of proinflammatory cytokines that contribute to a harmful cytokine storm response. Herein we discuss the connections between these ssRNA viruses, cytokine storm, and the roles of TLRs.

Since the initial description of Toll receptors in Drosophila and their mammalian counterparts Toll-like receptors (TLRs), numerous fundamental and applied studies have explored their crucial role as sensors of pathogen-associated molecular patterns (PAMPs). Among the ten human TLRs, TLR4 is particularly well known for its ability to detect lipopolysaccharides (LPS), a component of the Gram-negative bacterial cell wall. In addition to its archetypal functions, TLR4 is also a versatile virus sensor. This review provides a background on the discovery of TLR4 and how this knowledge laid a foundation for characterization of its diverse roles in antiviral responses, examined through genetic, biochemical, structural, and immunological approaches. These advances have led to a deeper understanding of the molecular functions that enable TLR4 to orchestrate multi-nodal control by professional antigen-presenting cells (APCs) to initiate appropriate and regulated antiviral immune responses.

Toll-like receptors (TLRs) of human are considered as the most critical immunological mediators of inflammatory pathogenesis of COVID-19. These immunoregulatory glycoproteins are located on the surface and/or intracellular compartment act as innate immune sensors. Upon binding with distinct SARS-CoV-2 ligand(s), TLRs signal activation of different transcription factors that induce expression of the proinflammatory mediators that collectively induce 'cytokine storm'. Similarly, TLR activation is also pivotal in conferring protection to infection and invasion as well as upregulating the tissue repair pathways. This dual role of the human TLRs in deciding the fate of SARS-CoV-2 has made these receptor proteins as the critical mediators of immunoprotective and immunopathogenic consequences associated with COVID-19. Herein, pathbreaking discoveries exploring the immunobiological importance of the TLRs in COVID-19 and developing TLR-directed therapeutic intervention have been reviewed by accessing the up-to-date literatures available in the public domain/databases. In accordance with our knowledge in association with the importance of TLRs' role against viruses and identification of viral particles, they have been recognized as suitable candidates with high potential as vaccine adjuvants. In this regard, the agonists of TLR4 and TLR9 have effective potential in vaccine technology while the others need further investigations. This comprehensive review suggests that basal level expression of TLRs can act as friends to keep our body safe from strangers but act as a foe via overexpression. Therefore, selective inhibition of the overexpressed TLRs appears to be a solution to counteract the cytokine storm while TLR-agonists as vaccine adjuvants could lessen the risk of infection in the naïve population.

Andrographolide is a medicinal compound which possesses anti-SARS-CoV-2 activity. A number of cellular targets of andrographolide have been identified by target predictions and computational studies.

However, a potential cellular target of andrographolide has never been explored in SARS-CoV-2 infected lung epithelial cells. We aimed to identify cellular pathways involved in andrographolide-mediated anti-SARS-CoV-2 activity.

The viral infection was determined by immunofluorescence staining, enzyme-linked immunosorbent assay and focus-forming assay. Proteomic analysis was employed to identify cellular pathways and key proteins controlled by andrographolide in the human lung epithelial cells Calu-3 infected by SARS-CoV-2. Immunofluorescence staining was used to test protein expression and localization. Western blot and realtime PCR were utilized to elucidate gene expression. Cellular glutathione level was examined by a reduced/oxidized glutathione assay. An ectopic gene expression was delivered by plasmid transfection.

Gene ontology analysis indicates that proteins involved in nuclear factor erythroid 2-related factor 2 (NRF2)-regulated pathways were differentially expressed by andrographolide. Notably, andrographolide increased expression and nuclear localization of the transcription factor NRF2. In addition, transcriptional expression of GCLC and glutamate-cysteine ligase modifier subunit (GCLM), which are NRF2 target genes, were induced by andrographolide. We further find that infection of SARS-CoV-2 resulted in a reduction of glutathione level in Calu-3; the effect that was rescued by andrographolide. Moreover, andrographolide also induced expression of the glutathione producing enzyme GCLC in SARS-CoV-2 infected lung epithelial cells. Importantly, an ectopic over-expression of GCLC or treatment of N-acetyl-L-cysteine in Calu-3 cells led to a decrease in SARS-CoV-2 infection.

Collectively, our findings suggest the interplay between GCLC-mediated glutathione biogenesis induced by andrographolide and the anti-SARS-CoV-2 activity. The glutathione biogenesis and recycling pathways should be further exploited as a targeted therapy against SARS-CoV-2 infection.

Discovered in late 2019, the SARS-CoV-2 coronavirus has caused the largest pandemic of the 21st century, claiming more than seven million lives. In most cases, the COVID-19 disease caused by the SARS-CoV-2 virus is relatively mild and affects only the upper respiratory tract; it most often manifests itself with fever, chills, cough, and sore throat, but also has less-common mild symptoms. In most cases, patients do not require hospitalization, and fully recover. However, in some cases, infection with the SARS-CoV-2 virus leads to the development of a severe form of COVID-19, which is characterized by the development of life-threatening complications affecting not only the lungs, but also other organs and systems. In particular, various forms of thrombotic complications are common among patients with a severe form of COVID-19. The mechanisms for the development of thrombotic complications in COVID-19 remain unclear. Accumulated data indicate that the pathogenesis of severe COVID-19 is based on disruptions in the functioning of various innate immune systems. The key role in the primary response to a viral infection is assigned to two systems. These are the pattern recognition receptors, primarily members of the toll-like receptor (TLR) family, and the complement system. Both systems are the first to engage in the fight against the virus and launch a whole range of mechanisms aimed at its rapid elimination. Normally, their joint activity leads to the destruction of the pathogen and recovery. However, disruptions in the functioning of these innate immune systems in COVID-19 can cause the development of an excessive inflammatory response that is dangerous for the body. In turn, excessive inflammation entails activation of and damage to the vascular endothelium, as well as the development of the hypercoagulable state observed in patients seriously ill with COVID-19. Activation of the endothelium and hypercoagulation lead to the development of thrombosis and, as a result, damage to organs and tissues. Immune-mediated thrombotic complications are termed "immunothrombosis". In this review, we discuss in detail the features of immunothrombosis associated with SARS-CoV-2 infection and its potential underlying mechanisms.

Cognitive impairment is often found at the acute stages and sequelae of coronavirus disease 2019 (COVID-19), and the underlying mechanisms remain unclear. The S1 protein from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) might be a cause of cognitive impairment associated with COVID-19. The nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome and neuroinflammation play important roles in Alzheimer's disease (AD) with cognitive impairment. However, their roles remain unknown in COVID-19 with cognitive impairment. We stimulated BV2 cells with S1 protein in vitro and injected the hippocampi of wild-type (WT) mice, NLRP3 knockout (KO), and microglia NLRP3 KO mice in vivo with S1 protein to induce cognitive impairment. We assessed exploratory behavior as associative memory using novel object recognition and Morris water maze tests. Neuroinflammation was analyzed using immunofluorescence and western blotting to detect inflammatory markers. Co-localized NLRP3 and S1 proteins were investigated using confocal microscopy. We found that S1 protein injection led to cognitive impairment, neuronal loss, and neuroinflammation by activating NLRP3 inflammation, and this was reduced by global NLRP3 KO and microglia NLRP3 KO. Furthermore, TAK 242, a specific inhibitor of Toll-like receptor-4, resulted in a significant reduction in NLRP3 and pro-IL-1β in BV2 cells with S1 protein stimulation. These results reveal a distinct mechanism through which the SARS-CoV-2 spike S1 protein promotes NLRP3 inflammasome activation and induces excessive inflammatory responses.

Even though the use of SARS-CoV-2 vaccines during the COVID-19 pandemic showed unprecedented success in a short time, it also exposed a flaw in the current vaccine design strategy to offer broad protection against emerging variants of concern. However, developing broad-spectrum vaccines is still a challenge for immunologists. The development of universal vaccines against emerging pathogens and their variants appears to be a practical solution to mitigate the economic and physical effects of the pandemic on society. Very few reports are available to explain the basic concept of universal vaccine design and development. This review provides an overview of the innate and adaptive immune responses generated against vaccination and essential insight into immune mechanisms helpful in designing universal vaccines targeting influenza viruses and coronaviruses. In addition, the characteristics, safety, and factors affecting the efficacy of universal vaccines have been discussed. Furthermore, several advancements in methods worthy of designing universal vaccines are described, including chimeric immunogens, heterologous prime-boost vaccines, reverse vaccinology, structure-based antigen design, pan-reactive antibody vaccines, conserved neutralizing epitope-based vaccines, mosaic nanoparticle-based vaccines, etc. In addition to the several advantages, significant potential constraints, such as defocusing the immune response and subdominance, are also discussed.

Effective treatment to prevent hospitalization and death in people with COVID-19 exists, but people still need interventions that alleviate symptoms without drug interactions. Oral serum-derived bovine immunoglobulins (SBI) may reduce symptoms and time-to-improvement in people with mild-to-moderate COVID-19. In this randomized, open-label, single-site study, participants with mild-to-moderate COVID-19 received SBI 5.0 g bis in die (BID) + Standard of Care (SOC) or SOC alone (2:1) for 2 weeks. After 2 weeks, 78.8% of hospitalized participants on SBI + SOC improved by World Health Organization (WHO) scale of ≥3 compared to 61.1% on SOC alone (odds ratio: OR = 2.4; p = 0.0663), with older participants (>57 years) showing more significant differences between the arms (OR = 6.1; p = 0.0109). Further, more participants on SBI + SOC reported absence of COVID-19 symptoms at Week 2 (74.2%) compared to SOC alone (43.6%; OR = 3.7; p = 0.0031), most notably the absence of dyspnea on exertion (OR = 4.4; p = 0.0047), with women exhibiting the most significant eradication of all symptoms (OR = 5.8; p = 0.0080). No difference in change of IL-6 between arms was observed. Overall, participants with mild-to-moderate COVID-19 on SBI + SOC had a shorter time-to-recovery than on SOC alone, with a significantly higher rate of complete resolution of symptoms. Dyspnea on exertion was the symptom most significantly impacted. For people with mild-to-moderate COVID-19, oral SBI could be a safe and effective intervention, devoid of drug interactions.

Dipeptidyl peptidase-4 (DPP-4) is a multifunctional serine ectopeptidase that cleaves and modifies a plethora of substrates, including regulatory peptides, cytokines and chemokines. DPP-4 is implicated in the regulation of immune response, viral entry, cellular adhesion, metastasis and chemotaxis. Regarding its numerous substrates and extensive expression inside the body, multitasking DPP-4 has been assumed to participate in different pathophysiological mechanisms. DPP-4 inhibitors or gliptins are increasingly used for the treatment of type 2 diabetes mellitus. Several reports from experimental and clinical studies have clarified that DPP-4 inhibitors exert many beneficial pleiotropic effects beyond glycaemic control, which are mediated by anti-inflammatory, anti-oxidant, anti-fibrotic and anti-apoptotic actions. The present review will highlight the most recent findings in the literature about these pleiotropic effects and the potential mechanisms underlying these benefits, with a specific focus on the potential effectiveness of DPP-4 inhibitors in coronavirus disease-19 and diabetic kidney disease.

Every cell in the human body is vital because it maintains equilibrium and carries out a variety of tasks, including growth and development. These activities are carried out by a set of instructions carried by many different genes and organized into DNA. It is well recognized that some lifestyle decisions, like using tobacco, alcohol, UV, or multiple sexual partners, might increase one's risk of developing cancer. The advantages of natural products for any health issue are well known, and researchers are making attempts to separate flavonoid-containing substances from plants. Various parts of plants contain a phenolic compound called flavonoid. Quercetin, which belongs to the class of compounds known as flavones with chromone skeletal structure, has anti-cancer activity.

The study was aimed at investigating the therapeutic action of the flavonoid quercetin on various cancer cells.

The phrases quercetin, anti-cancer, nanoparticles, and cell line were used to search the data using online resources such as PubMed, and Google Scholar. Several critical previous studies have been included.

Quercetin inhibits various dysregulated signaling pathways that cause cancer cells to undergo apoptosis to exercise its anticancer effects. Numerous signaling pathways are impacted by quercetin, such as the Hedgehog system, Akt, NF-κB pathway, downregulated mutant p53, JAK/STAT, G1 phase arrest, Wnt/β-Catenin, and MAPK. There are downsides to quercetin, like hydrophobicity, first-pass effect, instability in the gastrointestinal tract, etc., because of which it is not well-established in the pharmaceutical industry. The solution to these drawbacks in the future is using bio-nanomaterials like chitosan, PLGA, liposomes, and silk fibroin as carriers, which can enhance the target specificity of quercetin. The first section of this review covers the specifics of flavonoids and quercetin; the second section covers the anti-cancer activity of quercetin; and the third section explains the drawbacks and conjugation of quercetin with nanoparticles for drug delivery by overcoming quercetin's drawback.

Overall, this review presented details about quercetin, which is a plant derivative with a promising molecular mechanism of action. They inhibit cancer by various mechanisms with little or no side effects. It is anticipated that plant-based materials will become increasingly relevant in the treatment of cancer.

Nucleic acid-based vaccines allow scalable, rapid, and cell-free vaccine production in response to an emerging disease such as the current COVID-19 pandemic. Here, we objected to the design of a multiepitope mRNA vaccine against the structural proteins of SARS-CoV-2. Through an immunoinformatic approach, promising epitopes were predicted for the spike (S), envelope (E), membrane (M), and nucleocapsid (N) proteins. Fragments rich in overlapping epitopes were selected based on binding affinities with HLA classes I and II for the specific presentation to B and T lymphocytes. Two constructs were designed by fusing the fragments in different arrangements via GG linkers. Construct 1 showed better structural properties and interactions with toll-like receptor 2 (TLR-2), TLR-3, and TLR-4 during molecular docking and dynamic simulation. A 50S ribosomal L7/L12 adjuvant was added to its N-terminus to improve stability and immunogenicity. The final RNA sequence was used to design a trans-amplifying RNA (taRNA) vaccine in a split-vector system. It consists of two molecules: a nonreplicating RNA encoding a trans-acting replicase to amplify the second one, a trans-replicon (TR) RNA encoding the vaccine protein. Overall, the immune response simulation detected that activated B and T lymphocytes and increased memory cell formation. Macrophages and dendritic cells proliferated continuously, and IFN-γ and cytokines like IL-2 were released highly.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) induces immune-mediated diseases. The pathophysiology of COVID-19 uses the following three mechanisms: (1) inflammasome activation mechanism; (2) cGAS-STING signaling mechanism; and (3) SAMHD1 tetramerization mechanism, which leads to IFN-I production. Interactions between the host and virus govern induction, resulting in multiorgan impacts. The NLRP3 with cGAS-STING constitutes the primary immune response. The expression of SARS-CoV-2 ORF3a, NSP6, NSP7, and NSP8 blocks innate immune activation and facilitates virus replication by targeting the RIG-I/MDA5, TRIF, and cGAS-STING signaling. SAMHD1 has a target motif for CDK1 to protect virion assembly, threonine 592 to modulate a catalytically active tetramer, and antiviral IFN responses to block retroviral infection. Plastic and allosteric nucleic acid binding of SAMHD1 modulates the antiretroviral activity of SAMHD1. Therefore, inflammasome activation, cGAS-STING signaling, and SAMHD1 tetramerization explain acute kidney injury, hepatic, cardiac, neurological, and gastrointestinal injury of COVID-19. It might be necessary to effectively block the pathological courses of diverse diseases.

Viruses are obligate intracellular parasites, and they exploit the cellular pathways and resources of their respective host cells to survive and successfully multiply. The strategies of viruses concerning how to take advantage of the metabolic capabilities of host cells for their own replication can vary considerably. The most common metabolic alterations triggered by viruses affect the central carbon metabolism of infected host cells, in particular glycolysis, the pentose phosphate pathway, and the tricarboxylic acid cycle. The upregulation of these processes is aimed to increase the supply of nucleotides, amino acids, and lipids since these metabolic products are crucial for efficient viral proliferation. In detail, however, this manipulation may affect multiple sites and regulatory mechanisms of host-cell metabolism, depending not only on the specific viruses but also on the type of infected host cells. In this review, we report metabolic situations and reprogramming in different human host cells, tissues, and organs that are favorable for acute and persistent SARS-CoV-2 infection. This knowledge may be fundamental for the development of host-directed therapies.

Despite the potential of neutralizing antibodies in the management of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), clinical research on its efficacy in Chinese patients remains limited. This study is aimed at investigating the therapeutic effect of combination of antiviral therapy with neutralizing monoclonal antibodies for recurrent persistent SARS-CoV-2 pneumonia in patients with lymphoma complicated by B cell depletion. A prospective study was conducted on Chinese patients who were treated with antiviral nirmatrelvir/ritonavir therapy and the neutralizing antibody tixagevimab-cilgavimab (tix-cil). The primary outcome was the rate of recurrent SARS-CoV-2 infection. Five patients with lymphoma experienced recurrent SARS-CoV-2 pneumonia and received tix-cil treatment. All patients had a history of CD20 monoclonal antibody use within the year preceding SARS-CoV-2 infection, and two patients also had a history of Bruton's tyrosine kinase (BTK) inhibitor use. These patients had notably low lymphocyte counts and exhibited near depletion of B cells. All five patients tested negative for serum SARS-CoV-2 IgG and IgM antibodies. None of the patients developed reinfection with SARS-CoV-2 pneumonia after antiviral and tix-cil treatment during the 6-month follow-up period. In conclusion, the administration of antiviral and SARS-CoV-2-neutralizing antibodies showed encouraging therapeutic efficacy against SARS-CoV-2 pneumonia in patients with lymphoma complicated by B cell depletion, along with the potential preventive effect of neutralizing antibodies for up to 6 months.

The incidence of atherosclerotic cardiovascular disease is increasing globally, especially in low- and middle-income countries, despite significant efforts to reduce traditional risk factors. Premature subclinical atherosclerosis has been documented in association with several viral infections. The magnitude of the recent COVID-19 pandemic has highlighted the need to understand the association between SARS-CoV-2 and atherosclerosis. This review examines various pathophysiological mechanisms, including endothelial dysfunction, platelet activation, and inflammatory and immune hyperactivation triggered by SARS-CoV-2 infection, with specific attention on their roles in initiating and promoting the progression of atherosclerotic lesions. Additionally, it addresses the various pathogenic mechanisms by which COVID-19 in the post-acute phase may contribute to the development of vascular disease. Understanding the overlap of these syndromes may enable novel therapeutic strategies. We further explore the need for guidelines for closer follow-up for the often-overlooked evidence of atherosclerotic cardiovascular disease among patients with recent COVID-19, particularly those with cardiometabolic risk factors.

The late 2019 emergence of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19, caused profound and unprecedented disruption to the global socio-economic structure, negatively affecting millions of lives worldwide. A typical hallmark of severe COVID-19 is hyper inflammation due to aberrant cytokine release (cytokine storm) by innate immune cells. Recent studies have revealed that SARS-CoV-2, through its spike (S) protein, can activate the body's innate immune cells via Toll-Like Receptors (TLRs), particularly TLR4. In silico studies have demonstrated that the S protein binds with high affinity to TLR4, triggering downstream signaling processes that result in pro-inflammatory cytokine release. Compared to other TLRs, such as TLR2, TLR4 plays a more significant role in initiating and sustaining the inflammatory response associated with severe COVID-19. Furthermore, interactions between the virus and target cells can enhance the cellular expression of TLR4, making cells more susceptible to viral interactions and subsequent inflammation. This increased expression of TLR4 upon viral entry creates a feedback loop, where heightened TLR4 levels lead to amplified inflammatory responses, contributing to the severity of the disease. Additionally, TLR4's potent activation of inflammatory pathways sets it apart from other TLRs, underscoring its pivotal role in the pathogenesis of COVID-19. In this review, we thoroughly explore the multitude of regulatory signaling pathways that SARS-CoV-2 employs to incite inflammation. We specifically focus on the critical impact of TLR4 activation compared to other TLRs, highlighting how TLR4's interactions with the viral S protein can exacerbate the severity of COVID-19. By delving into the mechanisms of TLR4-mediated inflammation, we aim to shed light on potential therapeutic targets that could mitigate the inflammatory damage caused by severe COVID-19. Understanding the unique role of TLR4 in the context of SARS-CoV-2 infection could pave the way for novel treatment strategies that specifically inhibit this receptor's activity, thereby reducing the overall disease burden and improving patient outcomes.

Advancements in nanotechnology were vastly applied in medicine and pharmacy, especially in the field of nano-delivery systems. It took a long time for these systems to ensure precise delivery of very delicate molecules, such as RNA, to cells at concentrations that yield remarkable efficiency, with success rates reaching 95.0% and 94.5%. These days, there are several advantages of using nanotechnological solutions in the prevention and treatment of cancer and viral infections. Its interventions improve treatment outcomes both due to increased effectiveness of the drug at target location and by reducing adverse reactions, thereby increasing patient adherence to the therapy. Based on the current knowledge an updated review was made, and perspective, opportunities and challenges in nanomedicine were discussed. The methods employed include comprehensive examination of existing literature and studies on nanoparticles and nano-delivery systems including both in vitro tests performed on cell cultures and in vivo assessments carried out on appropriate animal models, with a specific emphasis on their applications in oncology and virology. This brings together various aspects including both structure and formation as well as its association with characteristic behaviour in organisms, providing a novel perspective. Furthermore, the practical application of these systems in medicine and pharmacy with a focus on viral diseases and malignancies was explored. This review can serve as a valuable guide for fellow researchers, helping them navigate the abundance of findings in this field. The results indicate that applications of nanotechnological solutions for the delivery of medicinal products improving therapeutic outcomes will continue to expand.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) interacts between the host and virus and govern induction, resulting in multiorgan impacts. Its pathophysiology involves the followings: 1) the angiotensin-converting enzyme (ACE2) and Toll-like receptor (TLR) pathways: 2) the neuropilin (NRP) pathway: 3) the spike protein pathway. Therefore, it is necessary to block the pathological course with modulating innate lymphoid cells against diverse corona variants in the future.

T lymphocytes play a primary role in the adaptive antiviral immunity. Both lymphocytosis and lymphopenia were found to be associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While lymphocytosis indicates an active anti-viral response, lymphopenia is a sign of poor prognosis. T-cells, in essence, rarely express ACE2 receptors, making the cause of cell depletion enigmatic. Moreover, emerging strains posed an immunological challenge, potentially alarming for the next pandemic. Herein, we review how possible indirect and direct key mechanisms could contribute to SARS-CoV-2-associated-lymphopenia. The fundamental mechanism is the inflammatory cytokine storm elicited by viral infection, which alters the host cell metabolism into a more acidic state. This "hyperlactic acidemia" together with the cytokine storm suppresses T-cell proliferation and triggers intrinsic/extrinsic apoptosis. SARS-CoV-2 infection also results in a shift from steady-state hematopoiesis to stress hematopoiesis. Even with low ACE2 expression, the presence of cholesterol-rich lipid rafts on activated T-cells may enhance viral entry and syncytia formation. Finally, direct viral infection of lymphocytes may indicate the participation of other receptors or auxiliary proteins on T-cells, that can work alone or in concert with other mechanisms. Therefore, we address the role of CD147-a novel route-for SARS-CoV-2 and its new variants. CD147 is not only expressed on T-cells, but it also interacts with other co-partners to orchestrate various biological processes. Given these features, CD147 is an appealing candidate for viral pathogenicity. Understanding the molecular and cellular mechanisms behind SARS-CoV-2-associated-lymphopenia will aid in the discovery of potential therapeutic targets to improve the resilience of our immune system against this rapidly evolving virus.

OM-85 is a bacterial lysate used in clinical practice to reduce duration and frequency of recurrent respiratory tract infections. Whereas knowledge of its regulatory effects in vivo has substantially advanced, the mechanisms of OM-85 sensing remain inadequately addressed. Here, we show that the immune response to OM-85 in the mouse is largely mediated by myeloid immune cells through Toll-like receptor (TLR) 4 in vitro and in vivo. Instead, in human immune cells, TLR2 and TLR4 orchestrate the response to OM-85, which binds to both receptors as shown by surface plasmon resonance assay. Ribonucleic acid-sequencing analyses of human monocyte-derived dendritic cells reveal that OM-85 triggers a pro-inflammatory signature and a unique gene set, which is not induced by canonical agonists of TLR2 or TLR4 and comprises tolerogenic genes. A largely overlapping TLR2/4-dependent gene signature was observed in individual subsets of primary human airway myeloid cells, highlighting the robust effects of OM-85. Collectively, our results suggest caution should be taken when relating murine studies on bacterial lysates to humans. Furthermore, our data shed light on how a standardized bacterial lysate shapes the response through TLR2 and TLR4, which are crucial for immune response, trained immunity, and tolerance.

The aim of this study was to elucidate the factors associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that may initiate cytokine cascades and correlate the clinical characteristics of patients with coronavirus disease 2019 (COVID-19) with their serum cytokine profiles.

Recombinant baculoviruses displaying SARS-CoV-2 spike or nucleocapsid protein were constructed and transfected into A549 cells and THP-1-derived macrophages, to determine which protein initiate cytokine release. SARS-CoV-2-specific antibody titers and cytokine profiles of patients with COVID-19 were determined, and the results were associated with their clinical characteristics, such as development of pneumonia or length of hospital stay.

The SARS-CoV-2 nucleocapsid protein, rather than the spike protein, triggers lung epithelial A549 cells to express IP-10, RANTES, IL-16, MIP-1α, basic FGF, eotaxin, IL-15, PDGF-BB, TRAIL, VEGF-A, and IL-5. Additionally, serum CTACK, basic FGF, GRO-α, IL-1α, IL-1RA, IL-2Rα, IL-9, IL-15, IL-16, IL-18, IP-10, M-CSF, MIF, MIG, RANTES, SCGF-β, SDF-1α, TNF-α, TNF-β, VEGF, PDGF-BB, TRAIL, β-NGF, eotaxin, GM-CSF, IFN-α2, INF-γ, and MCP-1 levels were considerably increased in patients with COVID-19. Among them, patients with pneumonia had higher serum IP-10 and M-CSF levels than patients without. Patients requiring less than 3 weeks to show negative COVID-19 tests after contracting COVID-19 had higher serum IP-10 levels than the remaining patients.

Our study revealed that nucleocapsid protein, lung epithelial cells, and IP-10 may be potential targets for the development of new strategies to prevent, or control, severe COVID-19.