SARS-CoV-2 reservoir in post-acute sequelae of COVID-19 (PASC).

Millions of people are suffering from Long COVID or post-acute sequelae of COVID-19 (PASC). Several biological factors have emerged as potential drivers of PASC pathology. Some individuals with PASC may not fully clear the coronavirus SARS-CoV-2 after acute infection. Instead, replicating virus and/or viral RNA-potentially capable of being translated to produce viral proteins-persist in tissue as a 'reservoir'. This reservoir could modulate host immune responses or release viral proteins into the circulation. Here we review studies that have identified SARS-CoV-2 RNA/protein or immune responses indicative of a SARS-CoV-2 reservoir in PASC samples. Mechanisms by which a SARS-CoV-2 reservoir may contribute to PASC pathology, including coagulation, microbiome and neuroimmune abnormalities, are delineated. We identify research priorities to guide the further study of a SARS-CoV-2 reservoir in PASC, with the goal that clinical trials of antivirals or other therapeutics with potential to clear a SARS-CoV-2 reservoir are accelerated.

Transcriptomics of type 2 diabetic and healthy human neutrophils.

OBJECTIVES: Chronic inflammatory diseases, including diabetes and cardiovascular disease, are heterogeneous and often co-morbid, with increasing global prevalence. Uncontrolled type 2 diabetes (T2D) can result in severe inflammatory complications. As neutrophils are essential to normal and aberrant inflammation, we conducted RNA-seq transcriptomic analyses to investigate the association between neutrophil gene expression and T2D phenotype. As specialized pro-resolving lipid mediators (SPM) act to resolve inflammation, we further surveyed the impact of neutrophil receptor binding SPM resolvin E1 (RvE1) on isolated diabetic and healthy neutrophils. METHODS: Cell isolation and RNA-seq analysis of neutrophils from N = 11 T2D and N = 7 healthy individuals with available clinical data was conducted. Additionally, cultured neutrophils (N = 3 T2D, N = 3 healthy) were perturbed with increasing RvE1 doses (0 nM, 1 nM, 10 nM, or 100 nM) prior to RNA-seq. Data was evaluated through a bioinformatics pipeline including pathway analysis and post hoc false discovery rate (FDR)-correction. RESULTS: We observed significant differential expression of 50 genes between T2D and healthy neutrophils (p < 0.05), including decreased T2D gene expression in inflammatory- and lipid-related genes SLC9A4, NECTIN2, and PLPP3 (p < 0.003). RvE1 treatment induced dose-dependent differential gene expression (uncorrected p < 0.05) across groups, including 59 healthy and 216 T2D neutrophil genes. Comparing T2D to healthy neutrophils, 1097 genes were differentially expressed across RvE1 doses, including two significant genes, LILRB5 and AKR1C1, involved in inflammation (p < 0.05). CONCLUSIONS: The neutrophil transcriptomic database revealed novel chronic inflammatory- and lipid-related genes that were differentially expressed between T2D cells when compared to controls, and cells responded to RvE1 dose-dependently by gene expression changes. Unraveling the mechanisms regulating abnormalities in diabetic neutrophil responses could lead to better diagnostics and therapeutics targeting inflammation and inflammation resolution.

Oral Microbial Species and Virulence Factors Associated with Oral Squamous Cell Carcinoma.

The human microbiome has been the focus of numerous research efforts to elucidate the pathogenesis of human diseases including cancer. Oral cancer mortality is high when compared with other cancers, as diagnosis often occurs during late stages. Its prevalence has increased in the USA over the past decade and accounts for over 40,000 new cancer patients each year. Additionally, oral cancer pathogenesis is not fully understood and is likely multifactorial. To unravel the relationships that are associated with the oral microbiome and their virulence factors, we used 16S rDNA and metagenomic sequencing to characterize the microbial composition and functional content in oral squamous cell carcinoma (OSCC) tumor tissue, non-tumor tissue, and saliva from 18 OSCC patients. Results indicate a higher number of bacteria belonging to the Fusobacteria, Bacteroidetes, and Firmicutes phyla associated with tumor tissue when compared with all other sample types. Additionally, saliva metaproteomics revealed a significant increase of Prevotella in five OSCC subjects, while Corynebacterium was mostly associated with ten healthy subjects. Lastly, we determined that there are adhesion and virulence factors associated with Streptococcus gordonii as well as from known oral pathogens belonging to the Fusobacterium genera found mostly in OSCC tissues. From these results, we propose that not only will the methods utilized in this study drastically improve OSCC diagnostics, but the organisms and specific virulence factors from the phyla detected in tumor tissue may be excellent biomarkers for characterizing disease progression.

Self-Assembled STrap for Global Proteomics and Salivary Biomarker Discovery.

Clinical biomarkers identified by shotgun proteomics require proteins in body fluids or tissues to be enzymatically digested before being separated and sequenced by liquid chromatography-tandem mass spectrometry. How well peptide signals can be resolved and detected is largely dependent on the quality of sample preparation. Conventional approaches such as in-gel, in-solution, and filter-based digestion, despite their extensive implementation by the community, become less appealing due to their unsatisfying protein/peptide recovery rate, lengthy sample processing, and/or lowcost-effectiveness. Suspension trapping has recently been demonstrated as an ultrafast approach for proteomic analysis. Here, for the first time, we extend its application to human salivary proteome analyses. In particular, we present a simple self-assembled glass fiber filter device which can be packed with minimal difficulty, is extremely cost-effective, and maintains the same performance as commercial filters. As a proof-of-principle, we analyzed the whole saliva from 8 healthy individuals as well as a cohort of 10 subjects of oral squamous cell carcinoma (OSCC) patients and non-OSCC subjects. Label-free quantification revealed surprisingly low interindividual variability and several known markers. Our study provides the first evidence of an easy-to-use and low-cost device for clinical proteomics as well as for general proteomic sample preparation.

Neutrophil Resolvin E1 Receptor Expression and Function in Type 2 Diabetes.

Unresolved inflammation is key in linking metabolic dysregulation and the immune system in type 2 diabetes. Successful regulation of acute inflammation requires biosynthesis of specialized proresolving lipid mediators, such as E-series resolvin (RvE) 1, and activation of cognate G protein-coupled receptors. RvE1 binds to leukotriene B4 (BLT-1) on neutrophils and to ERV-1/ChemR23 on monocyte/macrophages. We show novel actions of RvE1 and expression patterns of neutrophil receptors in type 2 diabetes. Neutrophils from healthy subjects express functional BLT-1, low levels of minimally functional ERV-1, and inversed coexpression when compared to neutrophils from type 2 diabetes subjects. Stimulation with TNF-α or LPS increased the expression of ERV-1 by healthy and diabetic neutrophils. RvE1 counteracted LPS and TNF-α induction of ERV-1 overexpression and endogenous diabetic overexpression, activating phagocytosis and resolution signals. Functional ERV-1 was determined by phosphorylation of the signaling protein ribosomal S6. Receptor-antagonism experiments revealed that the increase in phosphorylation of ribosomal S6 was mediated by BLT-1 in healthy subject neutrophils and by ERV-1 in diabetes. Metabololipidomics reveal a proinflammatory profile in diabetic serum. Cell phagocytosis is impaired in type 2 diabetes and requires RvE1 for activation. The dose of RvE1 required to activate resolution signals in type 2 diabetic neutrophils was significantly higher than in healthy controls. RvE1 rescues the dysregulation seen on neutrophil receptor profile and, following a therapeutic dosage, activates phagocytosis and resolution signals in type 2 diabetes. These findings reveal the importance of resolution receptors in health, disease, and dysregulation of inflammation in type 2 diabetes.

Potential for Stem Cell-Based Periodontal Therapy.

Periodontal diseases are highly prevalent and are linked to several systemic diseases. The goal of periodontal treatment is to halt the progression of the disease and regenerate the damaged tissue. However, achieving complete and functional periodontal regeneration is challenging because the periodontium is a complex apparatus composed of different tissues, including bone, cementum, and periodontal ligament. Stem cells may represent an effective therapeutic tool for periodontal regeneration due to their plasticity and their ability to regenerate different tissues. This review presents and critically analyzes the available information on stem cell-based therapy for the regeneration of periodontal tissues and suggests new avenues for the development of more effective therapeutic protocols.

Impact of resolvin E1 on murine neutrophil phagocytosis in type 2 diabetes.

Diabetic complications involve inflammation-mediated microvascular and macrovascular damage, disruption of lipid metabolism, glycosylation of proteins, and abnormalities of neutrophil-mediated events. Resolution of inflamed tissues to health and homeostasis is an active process mediated by endogenous lipid agonists, including lipoxins and resolvins. This proresolution system appears to be compromised in type 2 diabetes (T2D). The goal of this study was to investigate unresolved inflammation in T2D. Wild-type (WT) and genetically engineered mice, including T2D mice (db/db), transgenic mice overexpressing the human resolvin E1 (RvE1) receptor (ERV1), and a newly bred strain of db/ERV1 mice, were used to determine the impact of RvE1 on the phagocytosis of Porphyromonas gingivalis in T2D. Neutrophils were isolated and incubated with fluorescein isothiocyanate-labeled P. gingivalis, and phagocytosis was measured in a fluorochrome-based assay by flow cytometry. Mitogen-activated protein kinase (MAPK) (p42 and p44) and Akt (Thr308 and Ser473) phosphorylation was analyzed by Western blotting. The mouse dorsal air pouch model was used to evaluate the in vivo impact of RvE1. Results revealed that RvE1 increased the neutrophil phagocytosis of P. gingivalis in WT animals but had no impact in db/db animals. In ERV1-transgenic and ERV1-transgenic diabetic mice, phagocytosis was significantly increased. RvE1 decreased Akt and MAPK phosphorylation in the transgenic animals. In vivo dorsal air pouch studies revealed that RvE1 decreases neutrophil influx into the pouch and increases neutrophil phagocytosis of P. gingivalis in the transgenic animals; cutaneous fat deposition was reduced, as was macrophage infiltration. The results suggest that RvE1 rescues impaired neutrophil phagocytosis in obese T2D mice overexpressing ERV1.

Sputum production and salivary microbiome in COVID-19 patients reveals oral-lung axis.

SARS-CoV-2, a severe respiratory disease primarily targeting the lungs, was the leading cause of death worldwide during the pandemic. Understanding the interplay between the oral microbiome and inflammatory cytokines during acute infection is crucial for elucidating host immune responses. This study aimed to explore the relationship between the oral microbiome and cytokines in COVID-19 patients, particularly those with and without sputum production. Saliva and blood samples from 50 COVID-19 patients were subjected to 16S ribosomal RNA gene sequencing for oral microbiome analysis, and 65 saliva and serum cytokines were assessed using Luminex multiplex analysis. The Mann-Whitney test was used to compare cytokine levels between individuals with and without sputum production. Logistic regression machine learning models were employed to evaluate the predictive capability of oral microbiome, salivary, and blood biomarkers for sputum production. Significant differences were observed in the membership (Jaccard dissimilarity: p = 0.016) and abundance (PhILR dissimilarity: p = 0.048; metagenomeSeq) of salivary microbial communities between patients with and without sputum production. Seven bacterial genera, including Prevotella, Streptococcus, Actinomyces, Atopobium, Filifactor, Leptotrichia, and Selenomonas, were more prevalent in patients with sputum production (p<0.05, Fisher's exact test). Nine genera, including Prevotella, Megasphaera, Stomatobaculum, Selenomonas, Leptotrichia, Veillonella, Actinomyces, Atopobium, and Corynebacteria, were significantly more abundant in the sputum-producing group, while Lachnoanaerobaculum was more prevalent in the non-sputum-producing group (p<0.05, ANCOM-BC). Positive correlations were found between salivary IFN-gamma and Eotaxin2/CCL24 with sputum production, while negative correlations were noted with serum MCP3/CCL7, MIG/CXCL9, IL1 beta, and SCF (p<0.05, Mann-Whitney test). The machine learning model using only oral bacteria input outperformed the model that included all data: blood and saliva biomarkers, as well as clinical and demographic variables, in predicting sputum production in COVID-19 subjects. The performance metrics were as follows, comparing the model with only bacteria input versus the model with all input variables: precision (95% vs. 75%), recall (100% vs. 50%), F1-score (98% vs. 60%), and accuracy (82% vs. 66%).

Association between risk of obstructive sleep apnea severity and risk of severe COVID-19 symptoms: insights from salivary and serum cytokines.

Objectives: Obstructive sleep apnea (OSA) can adversely affect the immune response through clinical factors such as hypoxia, inflammation, and sleep disturbance. Since SARS-CoV-2 heavily relies on local and systemic host immune responses, this study aims to examine the links between the severity of OSA risk, cytokine levels, and the severity of symptoms associated with SARS-CoV-2 infection. Methods: Saliva and blood samples from 50 COVID-19 patients and 30 non-infected hospital staff members were collected. Using Luminex multiplex analysis, 65 blood and salivary cytokines were examined from the collected samples. Ordinal logistic regression analysis was utilized to examine the association between the self-reported risk of OSA, assessed through the STOP-Bang questionnaire, and the likelihood of experiencing severe symptoms of COVID-19. Mann-Whitney test was then performed to compare the cytokine levels between individuals with moderate to severe risk of OSA to those with a mild risk of OSA. Results: Ordinal logistic regression analysis revealed that individuals with a moderate to severe risk of OSA were 7.60 times more likely to experience more severe symptoms of COVID-19 compared to those with a mild risk of OSA (OR = 7.60, 95%CI: 3.03, 19.06, p < 0.001). Moreover, among COVID-19-positive patients with a moderate to severe risk of OSA, there was a statistically significant negative correlation with serum IL-6 (p < 0.05), Eotaxin (CCL11) (p = 0.04), and salivary MIP-3α/CCL20 (p = 0.04). In contrast, individuals without COVID-19 who had a moderate to severe risk of OSA exhibited a significant positive correlation with serum IL-6 (p = 0.04). Conclusion: Individuals with moderate to severe risk of OSA were more likely to experience severe COVID-19 symptoms than those with mild risk for OSA. Additional analysis from the present studies revealed distinct patterns of oral and systemic immune responses between individuals with mild and moderate to severe risk of OSA. Findings from the present study underscores the importance of early detection and management of OSA to improve clinical outcomes, particularly when faced with the subsequent superimposed infection such as COVID-19.

Minimal Bacterial Cell JCVI-syn3B as a Chassis to Investigate Interactions between Bacteria and Mammalian Cells.

Mycoplasmas are atypical bacteria with small genomes that necessitate colonization of their respective animal or plant hosts as obligate parasites, whether as pathogens, or commensals. Some can grow axenically in specialized complex media yet show only host-cell-dependent growth in cell culture, where they can survive chronically and often through interactions involving surface colonization or internalization. To develop a mycoplasma-based system to identify genes mediating such interactions, we exploited genetically tractable strains of the goat pathogen Mycoplasma mycoides (Mmc) with synthetic designer genomes representing the complete natural organism (minus virulence factors; JCVI-syn1.0) or its reduced counterpart (JCVI-syn3B) containing only those genes supporting axenic growth. By measuring growth of surviving organisms, physical association with cultured human cells (HEK-293T, HeLa), and induction of phagocytosis by human myeloid cells (dHL-60), we determined that JCVI-syn1.0 contained a set of eight genes (MMSYN1-0179 to MMSYN1-0186, dispensable for axenic growth) conferring survival, attachment, and phagocytosis phenotypes. JCVI-syn3B lacked these phenotypes, but insertion of these genes restored cell attachment and phagocytosis, although not survival. These results indicate that JCVI-syn3B may be a powerful living platform to analyze the role of specific gene sets, from any organism, on the interaction with diverse mammalian cells in culture.

Host-microbiome associations in saliva predict COVID-19 severity.

Established evidence indicates that oral microbiota plays a crucial role in modulating host immune responses to viral infection. Following severe acute respiratory syndrome coronavirus 2, there are coordinated microbiome and inflammatory responses within the mucosal and systemic compartments that are unknown. The specific roles the oral microbiota and inflammatory cytokines play in the pathogenesis of coronavirus disease 2019 (COVID-19) are yet to be explored. Here, we evaluated the relationships between the salivary microbiome and host parameters in different groups of COVID-19 severity based on their oxygen requirement. Saliva and blood samples (n = 80) were collected from COVID-19 and from noninfected individuals. We characterized the oral microbiomes using 16S ribosomal RNA gene sequencing and evaluated saliva and serum cytokines and chemokines using multiplex analysis. Alpha diversity of the salivary microbial community was negatively associated with COVID-19 severity, while diversity increased with health. Integrated cytokine evaluations of saliva and serum showed that the oral host response was distinct from the systemic response. The hierarchical classification of COVID-19 status and respiratory severity using multiple modalities separately (i.e. microbiome, salivary cytokines, and systemic cytokines) and simultaneously (i.e. multimodal perturbation analyses) revealed that the microbiome perturbation analysis was the most informative for predicting COVID-19 status and severity, followed by the multimodal. Our findings suggest that oral microbiome and salivary cytokines may be predictive of COVID-19 status and severity, whereas atypical local mucosal immune suppression and systemic hyperinflammation provide new cues to understand the pathogenesis in immunologically compromised populations.

Major alteration of Lung Microbiome and the Host Reaction in critically ill COVID-19 Patients with high viral load.

Background: Patients with COVID-19 under invasive mechanical ventilation are at higher risk of developing ventilator-associated pneumonia (VAP), associated with increased healthcare costs, and unfavorable prognosis. The underlying mechanisms of this phenomenon have not been thoroughly dissected. Therefore, this study attempted to bridge this gap by performing a lung microbiota analysis and evaluating the host immune responses that could drive the development of VAP. Materials and methods: In this prospective cohort study, mechanically ventilated patients with confirmed SARS-CoV-2 infection were enrolled. Nasal swabs (NS), endotracheal aspirates (ETA), and blood samples were collected initially within 12 hours of intubation and again at 72 hours post-intubation. Plasma samples underwent cytokine and metabolomic analyses, while NS and ETA samples were sequenced for lung microbiome examination. The cohort was categorized based on the development of VAP. Data analysis was conducted using RStudio version 4.3.1. Results: In a study of 36 COVID-19 patients on mechanical ventilation, significant differences were found in the nasal and pulmonary microbiome, notably in Staphylococcus and Enterobacteriaceae, linked to VAP. Patients with VAP showed a higher SARS-CoV-2 viral load, elevated neutralizing antibodies, and reduced inflammatory cytokines, including IFN-δ, IL-1ß, IL-12p70, IL-18, IL-6, TNF-α, and CCL4. Metabolomic analysis revealed changes in 22 metabolites in non-VAP patients and 27 in VAP patients, highlighting D-Maltose-Lactose, Histidinyl-Glycine, and various phosphatidylcholines, indicating a metabolic predisposition to VAP. Conclusions: This study reveals a critical link between respiratory microbiome alterations and ventilator-associated pneumonia in COVID-19 patients, with elevated SARS-CoV-2 levels and metabolic changes, providing novel insights into the underlying mechanisms of VAP with potential management and prevention implications.

Determining the optimal treatment target in patients with ulcerative colitis: rationale, design, protocol and interim analysis for the randomised controlled VERDICT trial.

INTRODUCTION: Symptoms, endoscopy and histology have been proposed as therapeutic targets in ulcerative colitis (UC). Observational studies suggest that the achievement of histologic remission may be associated with a lower risk of complications, compared with the achievement of endoscopic remission alone. The actiVE ulcerative colitis, a RanDomIsed Controlled Trial (VERDICT) aims to determine the optimal treatment target in patients with UC. METHODS AND ANALYSIS: In this multicentre, prospective randomised study, 660 patients with moderate to severe UC (Mayo rectal bleeding subscore [RBS] ≥1; Mayo endoscopic score [MES] ≥2) are randomly assigned to three treatment targets: corticosteroid-free symptomatic remission (Mayo RBS=0) (group 1); corticosteroid-free endoscopic remission (MES ≤1) and symptomatic remission (group 2); or corticosteroid-free histologic remission (Geboes score <2B.0), endoscopic remission and symptomatic remission (group 3). Treatment is escalated using vedolizumab according to a treatment algorithm that is dependent on the patient's baseline UC therapy until the target is achieved at weeks 16, 32 or 48. The primary outcome, the time from target achievement to a UC-related complication, will be compared between groups 1 and 3 using a Cox proportional hazards model. ETHICS AND DISSEMINATION: The study was approved by ethics committees at the country level or at individual sites as per individual country requirements. A full list of ethics committees is available on request. Study results will be disseminated in peer-reviewed journals and at scientific meetings. TRIAL REGISTRATION NUMBER: EudraCT: 2019-002485-12; NCT04259138.

Natural resolution of inflammation.

Inflammation is a protective response essential for maintaining human health and for fighting disease. As an active innate immune reaction to challenge, inflammation gives rise to clinical cardinal signs: rubor, calor, dolor, tumor and functio laesa. Termination of acute inflammation was previously recognized as a passive process; a natural decay of pro-inflammatory signals. We now understand that the natural resolution of inflammation involves well-integrated, active, biochemical programs that return tissues to homeostasis. This review focuses on recent advances in the understanding of the role of endogenous lipid mediators that modulate cellular fate and inflammation. Biosynthesis of eicosanoids and other lipids in exudates coincides with changes in the types of inflammatory cells. Resolution of inflammation is initiated by an active class switch in lipid mediators, such as classic prostaglandins and leukotrienes, to the production of proresolution mediators. Endogenous pro-resolving lipid mediators, including arachidonic acid-derived lipoxins, aspirin-triggered lipoxins, ω3-eicosapentaenoic acid-derived resolvins of the E-series, docosahexaenoic acid-derived resolvins of the D-series, protectins and maresins, are biosynthesized during the resolution phase of acute inflammation. Depending on the type of injury and the type of tissue, the initial cells that respond are polymorphonuclear leukocytes, monocytes/macrophages, epithelial cells or endothelial cells. The selective interaction of specific lipid mediators with G protein-coupled receptors expressed on innate immune cells (e.g. G protein-coupled receptor 32, lipoxin A4 receptor/formyl peptide receptor2, chemokine-like receptor 1, leukotriene B4 receptor type 1 and cabannoid receptor 2) induces cessation of leukocyte infiltration; vascular permeability/edema returns to normal with polymorphonuclear neutrophil death (mostly via apoptosis), the nonphlogistic infiltration of monocyte/macrophages and the removal (by macrophages) of apoptotic polymorphonuclear neutrophils, foreign agents (bacteria) and necrotic debris from the site. While an acute inflammatory response that is resolved in a timely manner prevents tissue injury, inadequate resolution and failure to return tissue to homeostasis results in neutrophil-mediated destruction and chronic inflammation. A better understanding of the complex mechanisms of lipid agonist mediators, cell targets and actions allows us to exploit and develop novel therapeutic strategies to treat human inflammatory diseases, including periodontal diseases.

Antimicrobial effect of sophoraflavanone G isolated from Sophora flavescens against mutans streptococci.

In this study, the antibacterial properties of sophoraflavanone G isolated from the methanol extract of Sophora flavescens were tested against 16 strains of mutans streptococci to screen and determine the optimal concentration of anti-caries natural extract. The antimicrobial activity was evaluated by measuring minimum bactericidal concentration (MBC). The cell viability of normal human gingival fibroblast (NHGF) cells was tested using the methyl thiazolyl tetrazolium assay after exposure to sophoraflavanone G. The data showed that sophoraflavanone G had a remarkable antimicrobial effect on the bacteria tested with an MBC ranging from 0.5 µg/ml to 4 µg/ml. Sophoraflavanone G had no cytotoxic effect on NHGF cells at concentrations where it produced an antimicrobial effect. These findings demonstrate that sophoraflavanone G has strong antimicrobial activity against mutans streptococci and could be useful in the development of novel oral hygiene products, such as a gargle solution or dentifrice.

Postoperative maxillary cyst after maxillary sinus augmentation.

The posterior edentulous maxilla is a critical anatomic region for dental implant therapy. Because of severe alveolar bone resorption and maxillary sinus pneumatization, low bone volume is often presented clinically. Although maxillary sinus augmentation has been developed to promote bone reconstruction and oral rehabilitation, complications have been reported. Possible complications include paranasal sinusitis, loss of the graft, and displacement of an implant into the antrum. In this study, we present an observed rare complication of maxillary sinus augmentation, a postoperative maxillary cyst that occurred 10 years after treatment.

Oral mucosa immunity: ultimate strategy to stop spreading of pandemic viruses.

Global pandemics are most likely initiated via zoonotic transmission to humans in which respiratory viruses infect airways with relevance to mucosal systems. Out of the known pandemics, five were initiated by respiratory viruses including current ongoing coronavirus disease 2019 (COVID-19). Striking progress in vaccine development and therapeutics has helped ameliorate the mortality and morbidity by infectious agents. Yet, organism replication and virus spread through mucosal tissues cannot be directly controlled by parenteral vaccines. A novel mitigation strategy is needed to elicit robust mucosal protection and broadly neutralizing activities to hamper virus entry mechanisms and inhibit transmission. This review focuses on the oral mucosa, which is a critical site of viral transmission and promising target to elicit sterile immunity. In addition to reviewing historic pandemics initiated by the zoonotic respiratory RNA viruses and the oral mucosal tissues, we discuss unique features of the oral immune responses. We address barriers and new prospects related to developing novel therapeutics to elicit protective immunity at the mucosal level to ultimately control transmission.

Host-Microbiome Associations in Saliva Predict COVID-19 Severity.

Established evidence indicates that oral microbiota plays a crucial role in modulating host immune responses to viral infection. Following Severe Acute Respiratory Syndrome Coronavirus 2 - SARS-CoV-2 - there are coordinated microbiome and inflammatory responses within the mucosal and systemic compartments that are unknown. The specific roles that the oral microbiota and inflammatory cytokines play in the pathogenesis of COVID-19 are yet to be explored. We evaluated the relationships between the salivary microbiome and host parameters in different groups of COVID-19 severity based on their Oxygen requirement. Saliva and blood samples (n = 80) were collected from COVID-19 and from non-infected individuals. We characterized the oral microbiomes using 16S ribosomal RNA gene sequencing and evaluated saliva and serum cytokines using Luminex multiplex analysis. Alpha diversity of the salivary microbial community was negatively associated with COVID-19 severity. Integrated cytokine evaluations of saliva and serum showed that the oral host response was distinct from the systemic response. The hierarchical classification of COVID-19 status and respiratory severity using multiple modalities separately (i.e., microbiome, salivary cytokines, and systemic cytokines) and simultaneously (i.e., multi-modal perturbation analyses) revealed that the microbiome perturbation analysis was the most informative for predicting COVID-19 status and severity, followed by the multi-modal. Our findings suggest that oral microbiome and salivary cytokines may be predictive of COVID-19 status and severity, whereas atypical local mucosal immune suppression and systemic hyperinflammation provide new cues to understand the pathogenesis in immunologically naïve populations.