Background: COVID-19 vaccines are safe and effective at preventing severe disease. Among the rare complications that may compromise vaccine acceptance are allergic reactions. This study aimed at comparing the incidence and potential triggers of the most commonly reported allergic reactions related to licensed COVID-19 vaccines in Europe and the United States (US) based on data of the two of the world’s largest vaccine adverse event reporting systems, EudraVigilance and VAERS. Methods: Data pertaining to allergic reactions post COVID-19 vaccination reported from week 52/2020 to week 39/2021 were collected from EudraVigilance and VAERS databases and analyzed. Incidence rates were calculated using the corresponding administered vaccine doses as denominators for all licensed vaccines and both platform types (mRNA or vectored). The composition of the novel mRNA and vectored vaccines was examined to identify potential allergic triggers. Results: Anaphylactic reactions and anaphylactic shock were the most common allergic reactions, predominantly reported by females, at estimated incidence rates of 9.91/million and 1.36/million vaccine doses, respectively. A 2- to 5-fold higher incidence of both allergic reactions was found in Europe compared to the US for both vaccine platforms. Most cases were benign. Fatalities were extremely rare and associated with vectored rather than mRNA vaccines. Conclusions: The precise mechanism(s) for allergic reactions after vaccination with COVID-19 vaccines are not fully known. Plausible explanations include exposure to components of the final pharmaceutical product and cross-reactivity to ingredients or unintentional impurities in the final formula. Additional research is warranted to further improve vaccine safety.

Judit Rovira Rubió

and 13 more

Background: From early life, respiratory viruses are implicated in the development, exacerbation and persistence of respiratory conditions such as asthma. Complex dynamics between microbial communities and host immune responses, shape immune maturation and homeostasis, influencing health outcomes. We evaluated the hypothesis that the respiratory virome is linked to systemic immune responses, using peripheral blood and nasopharyngeal swab samples from preschool-age children in the PreDicta cohort. Methods: Peripheral blood mononuclear cells from 51 children (32 asthmatics, 19 healthy controls), participating in the 2-year multinational PreDicta cohort were cultured with bacterial (Bacterial-DNA, LPS) or viral (R848, Poly:IC, RV) stimuli. Supernatants were analyzed by Luminex for the presence of 22 relevant cytokines. Virome composition was obtained using untargeted high troughput sequencing of nasopharyngeal samples. The metagenomic data were used for the characterization of virome profiles and the presence of key viral families (Picornaviridae, Anelloviridae, Siphoviridae). These were correlated to cytokine secretion patterns, identified through hierarchical clustering and principal component analysis. Results: High spontaneous cytokine release was associated with increased presence of Prokaryotic virome profiles and reduced presence of Eukaryotic and Anellovirus profiles. Antibacterial responses did not correlate with specific viral families or virome profile, however, low antiviral responders had more Prokaryotic and less Eukaryotic virome profiles. Anelloviruses and Anellovirus-dominated profiles were equally distributed amongst immune response clusters. The presence of Picornaviridae and Siphoviridae was associated with low interferon-λ responses. Asthma or allergy did not modify these correlations. Conclusions: Antiviral cytokines responses at a systemic level reflect the upper airway virome composition. Individuals with low innate interferon responses have higher abundance of Picornaviruses (mostly Rhinoviruses) and bacteriophages. Bacteriophages, particularly Siphoviridae appear to be sensitive sensors of host antimicrobial capacity, while Anelloviruses are not affected by TLR-induced immune responses.

Sofia Tagkareli

and 6 more

Background: Although FoxP3 + regulatory T (Treg) cells constitute a highly heterogeneous population, with different regulatory potential depending on the disease context, distinct subsets or phenotypes remain poorly defined. This hampers the development of immunotherapy for allergic and autoimmune disorders. Objective: This study aimed at characterizing distinct FoxP3 + Treg subpopulations involved in the suppression of Th2-mediated allergic inflammation in the lung. Methods: We used an established mouse model of allergic airway disease based on ovalbumin sensitization and challenge to analyze FoxP3 + Tregs during the induction and resolution of inflammation, and identify markers that distinguish their most suppressive phenotypes. We also developed a new knock-in mouse model ( Foxp3creCd103dtr) enabling the specific ablation of CD103 +FoxP3 + Tregs for functional studies. Results: We found that during resolution of allergic airway inflammation in mice >50% of FoxP3 + Treg cells expressed the integrin CD103 which marks FoxP3 + Treg cells of high IL-10 production, increased expression of immunoregulatory molecules such as KLRG1, ICOS and CD127, and enhanced suppressive capacity for Th2-mediated inflammatory responses. CD103 +FoxP3 + Tregs were essential for keeping allergic inflammation under control as their specific depletion in Foxp3creCd103dtr mice lead to severe alveocapillary damage, eosinophilic pneumonia, and markedly reduced lifespan of the animals. Conversely, adoptive transfer of CD103 +FoxP3 + Tregs effectively treated disease, attenuating Th2 responses and allergic inflammation in an IL-10-dependent manner. Conclusion: Our study identifies a novel regulatory T cell population, defined by CD103 expression, programmed to prevent exuberant type 2 inflammation and keep homeostasis in the respiratory tract under control. This has important therapeutic implications.
Background The maturation of innate immune responses in health and atopy is still incompletely understood. Methods We aimed to evaluate age-related trajectories of the TLR3 and TLR7/8 pathways across the lifespan and whether these differ between healthy and atopic individuals. Peripheral blood mononuclear cells (PBMCs) were isolated from 39 otherwise healthy atopic and 39 non-atopic subjects, aged 0-45 years. Selected cytokines involved in antiviral responses were measured by Luminex in culture supernatants of poly(I:C)- and R848-stimulated PBMCs. The non-parametric correlation between age and cytokine expression and differences in developmental trajectories between healthy and atopic were estimated. Patterns of cytokine development were identified with principal component analysis. Results Normal innate immune maturation entails significant and progressive age-related changes in the production of IL-1β, TNF-α, MIP-1β, MCP-3, IP-10, IL-10, IL-12p70 and IFN-γ upon TLR3 and/or TLR7/8 stimulation. Individual cytokines made small contributions to the observed variability; chemokines MCP-3 and IP-10 were key contributors. The development of these pathways deviated in atopic subjects with significant differences observed in the trajectories of IL-1β, MIP-1β and IL-10 synthesis. Conclusion TLR3 and TLR7/8 pathways mature during childhood, while atopy is associated with an abnormal maturation pattern. Suboptimal responses in Th1, inflammatory cytokine and chemokine production may be implicated in poor antiviral immunity in atopics, while deficient maturation of IL-10 producing capacity in the breaking of tolerance.

Sofia Tagkareli

and 6 more

Background: Although FoxP3+ regulatory T (Treg) cells constitute a highly heterogeneous population, with different regulatory potential depending on the context, distinct subsets or phenotypes remain poorly defined. This hampers the development of immunotherapy for allergic and autoimmune disorders. This study aimed at characterizing distinct FoxP3+ Treg subpopulations involved in the suppression of Th2-mediated allergic inflammation in the lung. Methods: We used an established mouse model of allergic airway disease based on ovalbumin sensitization and challenge to analyze FoxP3+ Tregs during the induction and resolution of inflammation, and identify markers that distinguish their most suppressive phenotypes. We also developed a new knock-in mouse model (Foxp3creCd103dtr) enabling the specific ablation of CD103+FoxP3+ Tregs for functional studies. Results: We found that during resolution of allergic airway inflammation in mice >50% of FoxP3+ Treg cells expressed the integrin CD103 which marks FoxP3+ Treg cells of high IL-10 production, increased expression of immunoregulatory molecules such as KLRG1, ICOS and CD127, and enhanced suppressive capacity for Th2-mediated inflammatory responses. CD103+FoxP3+ Tregs were essential for keeping allergic inflammation under control as their specific depletion in Foxp3creCd103dtr mice lead to severe alveocapillary damage and eosinophilic pneumonia, markedly reducing the lifespan of the experimental animals. Conversely, adoptive transfer of CD103+FoxP3+ Tregs effectively treated disease, attenuating Th2 responses and allergic inflammation in an IL-10-dependent manner. Conclusion: Our study identifies a novel regulatory T cell population, defined by CD103 expression, programmed to prevent exuberant type 2 inflammation and keep homeostasis in the respiratory tract under control. This has important therapeutic implications.

Evangelos Andreakos

and 2 more

EDITORIAL Coronavirus disease‐19 (COVID‐19) is a new disease caused by SARS‐CoV2. Since the beginning of 2020, it has become one of the main challenges of our times, causing a high incidence of severe pneumonia, acute respiratory distress syndrome (ARDS), multiorgan failure and death1. At the root of COVID-19 lies the sudden development of ‘cytokine storms’, hyper-inflammatory responses involving the release of pro-inflammatory cytokines (e.g., TNF-α, IL-6, IL-1, IL-8, and MCP-1) that impair the gas exchange function of the lung and lead in select patients, mostly with underlying comorbidities, to multiorgan failure and death1,2. Additional complications triggered by ‘cytokine storms’ include endothelial dysfunction and hypercoagulation, increasing the risk of thromboembolytic events, and life-threatening cardiovascular complications. Anti-inflammatory therapies are thus being considered for alleviating the damaging side effects of hyper-inflammation with many trials including anti-cytokine biologicals, disease-modifying antirheumatic drugs (DMARDs) and corticosteroids being ongoing3. Surprisingly, among them dexamethasone has taken center stage as initial results from the RECOVERY trial, a large multicenter randomized open-label trial for hospitalized patients run in the United Kingdom, revealed notable efficacy in the treatment of critically ill COVID-19 patients4.Dexamethasone is one of the oldest synthetic glucocorticoid agonists synthesized in 1957 and introduced into the clinic in 1961. When administered at 6 mg daily, either orally or intravenously for 10 days, dexamethasone was shown in the RECOVERY trial to improve survival rates of hospitalized patients with severe COVID-19 receiving oxygen or being on mechanical ventilation by a remarkable 30%4. Benefit was restricted to patients requiring respiratory support whereas in milder cases this was not clear. This notable efficacy of dexamethasone treatment goes against the current view of corticosteroid use in respiratory viral infections which remains contradictory. Although corticosteroids improve ventilator weaning and can lower the intensity of the host response to the virus, tempering the ‘cytokine storm’ and limiting immunopathology, they can also reduce viral clearance and lead to more severe disease. Understanding therefore how dexamethasome mediates its effects is of paramount importance.Dexamethasone, as other corticosteroids, is held to mediate its anti-inflammatory and immunosuppressive effects via the glucocorticoid receptor. Upon ligand binding, the receptor-corticosteroid molecule complex moves into the cell nucleus, where it dimerizes and binds to glucocorticoid response elements (GRE), acting as transcriptional repressor or transactivator of diverse sets of genes. This results in the inhibition of inflammatory cell activity, including neutrophils, macrophages and lymphocytes, and the suppression of pro-inflammatory cytokines such as TNF and interleukins and other genes such as cyclooxygenase-2 and inducible nitric oxide synthase5. However, we have recently uncovered that dexamethasone can also induce the D-series proresolving lipid mediator pathway leading to the production of 17-HDHA and the protectins D1 and DX6. These are potent major players of the molecular machinery driving the resolution of inflammation, i.e. the proper regulated termination of pro-inflammatory responses involving the catabolism of pro-inflammatory mediators, the removal of inflammatory cells and the restoration of the tissue in a timely and highly coordinated manner7. Although resolution of inflammation has long been considered to occur spontaneously as a result of the waning of pro-inflammatory responses, this is now known to be an ordered and highly regulated process involving the timely production of enzymatically oxygenated lipid-derived mediators such as protectins, D-series resolvins and maresins derived from the omega-3 fatty acid docosahexaenoic acid (DHA), E-series resolvins derived from eicosapentaenoic acid (EPA), and lipoxins biosynthesized from omega-6 fatty acids following eicosanoid class switching7. Interestingly, certain lipid mediators have been shown to exert additional non-conventional functions; resolvin D4 can attenuate pathologic thrombosis, reduce NETosis and promote clot removal8 which is now recognized as a key pathology of COVID-19 infection, while resolvin E4 (RvE4) stimulates efferocytosis of senescent erythrocytes in hemorrhagic exudates especially under hypoxic conditions that characterize COVID-199. Moreover, corticosteroids have been reported to reduce fibrinogen and procoagulant factors under pro-inflammatory conditions and increase anticoagulant factors10.The ability of viral infections to induce proresolving lipids has been reported earlier. Toll-like receptor 7 (TLR7), a major pattern recognition receptor of viral RNA, activates PD1 and PDX production11. Moreover, influenza virus infection has been demonstrated to drive proresolving lipid mediator networks including the production of PD1 which limits influenza pathogenicity by directly interacting with the RNA replication machinery to inhibit viral RNA nuclear export12,13. Notably, in particularly virulent strains of influenza virus such as the H5N1 avian strain, PD1 formation is not sufficiently upregulated, leading to more efficient viral replication and host demise12. It is therefore plausible that the efficacy of dexamethasone in COVID-19 is due at least in part to its ability to induce proresolving lipid mediators that possess multiple anti-inflammatory and proresolving actions tempering down inflammation and promoting its resolution, preventing coagulation and enhancing viral and bacterial clearance (Figure 1) yet are not immunosuppressive . Whether other corticosteroids beyond dexamethasone can also mediate such effects, and to what extent, is not known. Whether inhalable corticosteroids, such as those given to asthmatic patients, can also induce proresolving lipid mediator networks locally and thus prevent the development of severe SARS‐CoV‐2 infection remains to be determined. There is evidence that asthmatic patients exhibit reduced incidence of severe and/or critical COVID-1914.Recently, COVID-19 patients showed increased association of serum arachidonate-derived proinflammatory lipid mediators, e.g. prostaglandins, in severe COVID -19 infections while some pro-resolving mediators such as resolvin E3 were up-regulated in the moderate COVID-19 group suggesting that an imbalance in lipid mediators with a swift toward pro-inflammatory mediators in severe disease may contribute to COVID-19 disease severity15. Although the involvement of proresolving lipid mediator pathways in COVID-19 is an attractive hypothesis, further evidence from human trials is needed as there are no studies at present reporting the induction or modulation of such networks in the context of the various disease stages and treatments. It is thus of uttermost priority to investigate proresolving lipid mediators in COVID-19, in a temporal and longitudinal manner, as modulating these networks either through drug treatment or direct administration of resolvin and protectins agonists has the potential to affect this highly lethal and devastating disease in a way other approaches cannot. Such studies are therefore eagerly awaited.