Institut für Immunologie
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Monitoring the seroprevalence of SARS-CoV-2 in children and adolescents can provide valuable information for effective SARS-CoV-2 surveillance, and thus guide vaccination strategies. In this study, we quantified antibodies against the spike S1 domains of several SARS-CoV-2 variants (wild-type, Alpha, Delta, and Omicron variants) as well as endemic human coronaviruses (HCoVs) in 1,309 children and adolescents screened between December 2020 and March 2023. Their antibody binding profiles were compared with those of 22 pre-pandemic samples from children and adolescents using an in-house Luminex ® -based Corona Array (CA). The primary objectives of this study were to (i) monitor SARS-CoV-2-specific antibodies in children and adolescents, (ii) evaluate whether the S1-specific antibody response can identify the infecting variant of concern (VoC), (iii) estimate the prevalence of silent infections, and (iv) test whether vaccination or infection with SARS-CoV-2 induce HCoV cross-reactive antibodies. Both SARS-CoV-2 infection and vaccination induced a robust antibody response against the S1 domain of WT and VoCs in children and adolescents. Antibodies specific for the S1 domain were able to distinguish between SARS-CoV-2 VoCs in infected children. The serologically identified VoC was typically the predominant VoC at the time of infection. Furthermore, our highly sensitive CA identified more silent SARS-CoV-2 infections than a commercial ELISA (12.1% vs. 6.3%, respectively), and provided insights into the infecting VoC. Seroconversion to endemic HCoVs occurred in early childhood, and vaccination or infection with SARS-CoV-2 did not induce HCoV S1 cross-reactive antibodies. In conclusion, the antibody response to the S1 domain of the spike protein of SARS-CoV-2 is highly specific, providing information about the infecting VoC and revealing clinically silent infections.
Background
Atopic dermatitis (AD) is a chronic, relapsing inflammatory skin disease with skin barrier defects and a misdirected type 2 immune response against harmless antigens. The skin microbiome in AD is characterized by a reduction in microbial diversity with a dominance of staphylococci, including Staphylococcus epidermidis ( S. epidermidis ).
Objective
To assess whether S. epidermidis antigens play a role in AD, we screened for candidate allergens and studied the T cell and humoral immune response against the extracellular serine protease (Esp).
Methods
To identify candidate allergens, we analyzed the binding of human serum IgG4, as a surrogate of IgE, to S. epidermidis extracellular proteins using 2-dimensional immunoblotting and mass spectrometry. We then measured serum IgE and IgG1 binding to recombinant Esp by ELISA in healthy and AD individuals. We also stimulated T cells from AD patients and control subjects with Esp and measured the secreted cytokines. Finally, we analyzed the proteolytic activity of Esp against IL-33 and determined the cleavage sites by mass spectrometry.
Results
We identified Esp as the dominant candidate allergen of S. epidermidis . Esp-specific IgE was present in human serum; AD patients had higher concentrations than controls. T cells reacting to Esp were detectable in both AD patients and healthy controls. The T cell response in healthy adults was characterized by IL-17, IL-22, IFN-γ, and IL-10, whereas the AD patients’ T cells lacked IL-17 production and released only low amounts of IL-22, IFN-γ, and IL-10. In contrast, Th2 cytokine release was higher in T cells from AD patients than from healthy controls. Mature Esp cleaved and activated the alarmin IL-33.
Conclusion
The extracellular serine protease Esp of S. epidermidis can activate IL-33. As an antigen, Esp elicits a type 2-biased antibody and T cell response in AD patients. This suggests that S. epidermidis can aggravate AD through the allergenic properties of Esp.
Staphylococcus (S.) aureus is a pathobiont, colonizing 20% of healthy adults persistently, while the remainder is colonized transiently, resulting in a general colonization rate of approximately 37%. Beside symptom-free colonization, S. aureus is the cause of different diseases, including self-limiting food poisoning, skin and soft tissue infections, but also life-threatening pneumonia, endocarditis and sepsis. Additionally, numerous studies suggest an involvement of S. aureus in allergic diseases, in which S. aureus colonizes up to 90% of patients. The high abundance of S. aureus in healthy individuals and patients with allergic diseases is enabled by the broad spectrum of its virulence factors. Among them are the T cell superantigens (SAgs).
SAgs act on the immune system in multiple ways. On the one hand, they are superantigenic, i.e. they directly crosslink receptors on antigen-presenting cells (APCs) and T cells. This causes their toxicity, which is due to excessive proliferation of immune cells and cytokine release that can culminate in toxic shock syndrome and death. On the other hand, there are indications, that SAgs are recognized by the adaptive immune system in a conventional way. Most adults have high affinity SAg-specific antibodies that can neutralize the toxins. These antibodies are produced by B cells, which need SAg-specific T cell help for differentiation, presumably provided in a conventional cognate interaction. High levels of SAg-specific IgE were detected in various allergic diseases and linked to the pathology, strongly suggesting an allergenic role of SAgs. However, specific T cells that recognize SAgs as conventional antigens have never been demonstrated and characterized.
In this study, we investigated the recognition of SAgs as conventional antigens by human T cells. This was made possible through the generation of SAg toxoids, which lack superantigenicity but retain the ability to be taken up by APCs, processed and presented to specific T cells in a conventional manner. The lack of residual superantigenicity was validated by analyzing the potential of the toxoids to oligoclonally expand T cells of specific TCR Vβ families and by comparing the immune cell transcriptome after stimulation with wild-type (WT) SAgs, toxoids and conventional S. aureus antigens. We demonstrated, that of the four tested toxoids (inactivated (i) SEA, iSEB, iTSST and iTSSTw) two lack superantigenicity (iSEA and iSEB).
Using iSEA and iSEB as recall antigens for the restimulation of human T cells ex vivo, we discovered a robust SAg-specific T cell memory response. In particular, we found that T cells from healthy, non-symptomatic individuals exhibited a Type 2-polarized cytokine profile when stimulated with iSEA or iSEB. In contrast, patients with chronic rhinosinusitis with nasal polyps (CRSwNP) did not exhibit SEA- or SEB-specific Th2 cells. Additionally, we studied the humoral response and observed increased anti-SAg-IgE levels in the healthy individuals, but not in CRSwNP patients.
While Type 1 and Type 3 immune responses are associated with a protection against S. aureus, the polarization towards Type 2 responses have been discussed to be non-protective and an immune evasion mechanism, which facilitates colonization.
Insights into the involvement of SAgs in the polarization of a specific immune memory and in allergic diseases should be taken into consideration when designing vaccines against S. aureus for individuals with or without allergic diseases. This is important, because the pre-existing immune response to S. aureus antigens might be boosted by vaccination, which would be unwanted in case of a non-protective response profile.
Introduction
COVID-19 vaccines are highly effective in inducing protective immunity. While the serum antibody response to COVID-19 vaccination has been studied in depth, our knowledge of the underlying plasmablast and memory B cell (Bmem) responses is still incomplete. Here, we determined the antibody and B cell response to COVID-19 vaccination in a naïve population and contrasted it with the response to a single influenza vaccination in a primed cohort. In addition, we analyzed the antibody and B cell responses against the four endemic human coronaviruses (HCoVs).
Methods
Measurement of specific plasma IgG antibodies was combined with functional analyses of antibody-secreting plasmablasts and Bmems. SARS-CoV-2- and HCoV-specific IgG antibodies were quantified with an in-house bead-based multiplexed immunoassay.
Results
The antibody and B cell responses to COVID-19 vaccination reflected the kinetics of a prime-boost immunization, characterized by a slow and moderate primary response and a faster and stronger secondary response. In contrast, the influenza vaccinees possessed robust immune memory for the vaccine antigens prior to vaccination, and the recall vaccination moderately boosted antibody production and Bmem responses. Antibody levels and Bmem responses waned several months after the 2 nd COVID-19 vaccination, but were restored upon the 3 rd vaccination. The COVID-19 vaccine-induced antibodies mainly targeted novel, non-cross-reactive S1 epitopes of the viral spike protein, while cross-reactive S2 epitopes were less immunogenic. Booster vaccination not only strongly enhanced neutralizing antibodies against an original SARS-CoV-2 strain, but also induced neutralizing antibodies against the Omicron BA.2 variant. We observed a 100% plasma antibody prevalence against the S1 subunits of HCoVs, which was not affected by vaccination.
Discussion
Overall, by complementing classical serology with a functional evaluation of plasmablasts and memory B cells we provide new insights into the specificity of COVID-19 vaccine-induced antibody and B cell responses.
The iron-regulated surface determinant protein B (IsdB) of Staphylococcus aureus is involved in the acquisition of iron from hemoglobin. Moreover, IsdB elicits an adaptive immune response in mice and humans. Here, we show that IsdB also has impact on innate immunity. IsdB induces the release of proinflammatory cytokines, including IL-6 and IL-1β, in innate immune cells of humans and mice. In silico analysis and thermophoresis show that IsdB directly binds to TLR4 with high affinity. TLR4 sensing was essential for the IsdB-mediated production of IL-6, IL-1β, and other cytokines as it was abolished by blocking of TLR4-MyD88-IRAK1/4-NF-κB signaling. The release of IL-1β additionally required activation of the NLRP3 inflammasome. In human monocytes infected with live S. aureus, IsdB was necessary for maximal IL-1β release. Our studies identify S. aureus IsdB as a novel pathogen-associated molecular pattern that triggers innate immune defense mechanisms.
Life-threatening toxic shock syndrome is often caused by the superantigen toxic shock syndrome toxin-1 (TSST-1) produced by Staphylococcus aureus. A well-known risk factor is the lack of neutralizing antibodies. To identify determinants of the anti-TSST-1 antibody response, we examined 976 participants of the German population-based epidemiological Study of Health in Pomerania (SHIP-TREND-0). We measured anti-TSST-1 antibody levels, analyzed the colonization with TSST-1-encoding S. aureus strains, and performed a genome-wide association analysis of genetic risk factors. TSST-1-specific serum IgG levels varied over a range of 4.2 logs and were elevated by a factor of 12.3 upon nasal colonization with TSST-1-encoding S. aureus. Moreover, the anti-TSST-1 antibody levels were strongly associated with HLA class II gene loci. HLA-DRB1*03:01 and HLA-DQB1*02:01 were positively, and HLA-DRB1*01:01 as well as HLA-DQB1*05:01 negatively associated with the anti-TSST-1 antibody levels. Thus, both toxin exposure and HLA alleles affect the human antibody response to TSST-1.
Introduction: In the light of the ongoing SARS-CoV-2 pandemic, convalescent plasma is a treatment option for COVID-19. In contrast to usual therapeutic plasma, the therapeutic agents of convalescent plasma do not represent clotting factor activities, but immunoglobulins. Quarantine storage of convalescent plasma as a measure to reduce the risk of pathogen transmission is not feasible. Therefore, pathogen inactivation (e.g., Theraflex®-MB, Macopharma, Mouvaux, France) is an attractive option. Data on the impact of pathogen inactivation by methylene blue (MB) treatment on antibody integrity are sparse. Methods: Antigen-specific binding capacity was tested before and after MB treatment of plasma (n = 10). IgG and IgM isoagglutinin titers were tested by agglutination in increasing dilutions. Furthermore, the binding of anti-EBV and anti-tetanus toxin IgG to their specific antigens was assessed by ELISA, and IgG binding to Fc receptors was assessed by flow cytometry using THP-1 cells expressing FcRI and FcRII. Results: There was no significant difference in the isoagglutinin titers, the antigen binding capacity of anti-EBV and anti-tetanus toxin IgG, as well as the Fc receptor binding capacity before and after MB treatment of plasma. Conclusion: MB treatment of plasma does not inhibit the binding capacity of IgM and IgG to their epitopes, or the Fc receptor interaction of IgG. Based on these results, MB treatment of convalescent plasma is appropriate to reduce the risk of pathogen transmission if quarantine storage is omitted.
: An enhanced indoleamine 2,3-dioxygenase 1 (IDO1) activity is associated with an increased
mortality risk in sepsis patients. Thus, the preventive inhibition of IDO1 activity may be
a promising strategy to attenuate the severity of septic shock. 1-methyltryptophan (1-MT)
is currently in the interest of research due to its potential inhibitory effects on IDO1 and
immunomodulatory properties. The present study aims to investigate the protective and
immunomodulatory effects of 1-methyltryptophan against endotoxin-induced shock in a porcine
in vivo model. Effects of 1-MT were determined on lipopolysaccharide (LPS)-induced tryptophan
(TRP) degradation, immune response and sickness behaviour. 1-MT increased TRP and its metabolite
kynurenic acid (KYNA) in plasma and tissues, suppressed the LPS-induced maturation of neutrophils
and increased inactivity of the animals. 1-MT did not inhibit the LPS-induced degradation of TRP
to kynurenine (KYN)—a marker for IDO1 activity—although the increase in KYNA indicates that
degradation to one branch of the KYN pathway is facilitated. In conclusion, our findings provide
no evidence for IDO1 inhibition but reveal the side effects of 1-MT that may result from the proven
interference of KYNA and 1-MT with aryl hydrocarbon receptor signalling. These effects should be
considered for therapeutic applications of 1-MT.
: Platelets are components of the blood that are highly reactive, and they quickly respond
to multiple physiological and pathophysiological processes. In the last decade, it became clear that
platelets are the key components of circulation, linking hemostasis, innate, and acquired immunity.
Protein composition, localization, and activity are crucial for platelet function and regulation. The
current state of mass spectrometry-based proteomics has tremendous potential to identify and quantify thousands of proteins from a minimal amount of material, unravel multiple post-translational
modifications, and monitor platelet activity during drug treatments. This review focuses on the role
of proteomics in understanding the molecular basics of the classical and newly emerging functions
of platelets. including the recently described role of platelets in immunology and the development
of COVID-19.The state-of-the-art proteomic technologies and their application in studying platelet
biogenesis, signaling, and storage are described, and the potential of newly appeared trapped ion
mobility spectrometry (TIMS) is highlighted. Additionally, implementing proteomic methods in
platelet transfusion medicine, and as a diagnostic and prognostic tool, is discussed.
The GATA1 transcription factor is essential for normal erythropoiesis and megakaryocytic differentiation. Germline GATA1 pathogenic variants in the N-terminal zinc finger (N-ZF) are typically associated with X-linked thrombocytopenia, platelet dysfunction, and dyserythropoietic anemia. A few variants in the C-terminal ZF (C-ZF) domain are described with normal platelet count but altered platelet function as the main characteristic. Independently performed molecular genetic analysis identified a novel hemizygous variant (c.865C>T, p.H289Y) in the C-ZF region of GATA1 in a German patient and in a Spanish patient. We characterized the bleeding and platelet phenotype of these patients and compared these findings with the parameters of two German siblings carrying the likely pathogenic variant p.D218N in the GATA1 N-ZF domain. The main difference was profound thrombocytopenia in the brothers carrying the p.D218N variant compared to a normal platelet count in patients carrying the p.H289Y variant; only the Spanish patient occasionally developed mild thrombocytopenia. A functional platelet defect affecting αIIbβ3 integrin activation and α-granule secretion was present in all patients. Additionally, mild anemia, anisocytosis, and poikilocytosis were observed in the patients with the C-ZF variant. Our data support the concept that GATA1 variants located in the different ZF regions can lead to clinically diverse manifestations.