Bernd Jahrsdörfer

Introduction: The emergence of SARS-CoV-2 variants of concern (VOCs), particularly Omicron, has challenged the efficacy of initial COVID-19 vaccination strategies. Booster immunizations, especially with mRNA vaccines, were introduced to enhance and prolong immune protection. However, the underlying mechanisms of humoral and cellular immunity induced by homologous versus heterologous vaccination regimens remain incompletely understood. This study aimed to elucidate the immune responses, including B cell, plasmacytoid dendritic cell (pDC), and T cell activation, following mRNA booster vaccination.Methods: In a longitudinal cohort study, 136 individuals received three different vaccination regimens: homologous mRNA, heterologous vector-mRNA-mRNA, or heterologous vector-vector-mRNA vaccinations. Serum and peripheral blood mononuclear cells (PBMCs) were collected at multiple time points up to 64 weeks after initial vaccination. Anti-SARS-CoV-2 IgG titers and neutralization capacity against the wildtype virus and Omicron variant were measured using ELISA and cPass assays. Cellular immunity was assessed by IFN-γ release assays, and flow cytometry was employed to analyze B cell and pDC frequencies, viability, and activation markers. Functional pDC-mediated T cell activation was evaluated in mixed lymphocyte cultures.Results: mRNA booster vaccination stabilized high anti-SARS-CoV-2 IgG titers and neutralizing activity against wildtype virus across all regimens, with the homologous mRNA group showing the highest antibody titers and Omicron neutralization capacity. Peripheral B cell frequencies and activation markers (MHC class I/II, CD86) were significantly upregulated post-booster. pDCs demonstrated enhanced antigen-presenting capacity and significantly promoted SARS-CoV-2-specific T cell IFN-γ responses in vitro. Despite differences in humoral responses between regimens, breakthrough infection rates up to 25 weeks post-booster were comparable across cohorts, suggesting compensatory mechanisms via cellular immunity.Discussion: Our findings highlight the pivotal role of pDCs and T cells in sustaining effective immunity following mRNA booster vaccination. While homologous mRNA regimens induce superior humoral responses, robust cellular immunity in heterologous regimens may balance protection levels against breakthrough infections. The study underscores the importance of integrated humoral and cellular immune responses, suggesting potential for optimized booster strategies and pDC-targeted vaccine designs to enhance long-term protection against SARS-CoV-2 and emerging variants.

The aim of the following review is to shed light on the putative role of regulatory B cells (Bregs) in various human diseases and highlight their potential prognostic and therapeutic relevance in humans. Regulatory B cells are a heterogeneous group of B lymphocytes capable of suppressing inflammatory immune reactions. In this way, Bregs contribute to the maintenance of tolerance and immune homeostasis by limiting ongoing immune reactions temporally and spatially. Bregs play an important role in attenuating pathological inflammatory reactions that can be associated with transplant rejection, graft-versus-host disease, autoimmune diseases and allergies but also with infectious, neoplastic and metabolic diseases. Early studies of Bregs identified IL-10 as an important functional molecule, so the IL-10-secreting murine B10 cell is still considered a prototype Breg, and IL-10 has long been central to the search for human Breg equivalents. However, over the past two decades, other molecules that may contribute to the immunosuppressive function of Bregs have been discovered, some of which are only present in human Bregs. This expanded arsenal includes several anti-inflammatory cytokines, such as IL-35 and TGF-β, but also enzymes such as CD39/CD73, granzyme B and IDO as well as cell surface proteins including PD-L1, CD1d and CD25. In summary, the present review illustrates in a concise and comprehensive manner that although human Bregs share common functional immunosuppressive features leading to a prominent role in various human immunpathologies, they are composed of a pool of different B cell types with rather heterogeneous phenotypic and transcriptional properties.

Introduction: The infusion of ex-vivo-generated regulatory B cells may represent a promising novel therapeutic approach for a variety of autoimmune and hyperinflammatory conditions including graft-versus-host disease.Methods: Previously, we developed a protocol for the generation of a novel population of regulatory B cells, which are characterized by secretion of enzymatically active granzyme B (GraB cells). This protocol uses recombinant interleukin 21 (IL-21) and goat-derived F(ab)’2 fragments against the human B cell receptor (anti-BCR). Generally, the use of xenogeneic material for the manufacturing of advanced therapy medicinal products should be avoided to prevent adverse immune reactions as well as potential transmission of so far unknown diseases.Results: In the present work we demonstrated that phorbol-12-myristate-13-acetate (PMA/TPA), a phorbol ester with a particular analogy to the second messenger diacylglycerol (DAG), is a potent enhancer of IL-21-induced differentiation of pre-activated B cells into GraB cells. The percentage of GraB cells after stimulation of pre-activated B cells with IL-21 and PMA/TPA was not significantly lower compared to stimulation with IL-21 and anti-BCR.Discussion: Given that PMA/TPA has already undergone encouraging clinical testing in patients with certain haematological diseases, our results suggest that PMA/TPA may be a safe and feasible alternative for ex-vivo manufacturing of GraB cells.

BACKGROUND. Results of many randomized trials on COVID-19 convalescent plasma (CCP) have been reported, but information on long-term outcome after CCP treatment is limited. The objectives of this extended observation of the randomized CAPSID trial are to assess long-term outcome and disease burden in patients initially treated with or without CCP. METHODS. Of 105 randomized patients, 50 participated in the extended observation. Quality of life (QoL) was assessed by questionnaires and a structured interview. CCP donors (n = 113) with asymptomatic to moderate COVID-19 were included as a reference group. RESULTS. The median follow-up of patients was 396 days, and the estimated 1-year survival was 78.7% in the CCP group and 60.2% in the control (P = 0.08). The subgroup treated with a higher cumulative amount of neutralizing antibodies showed a better 1-year survival compared with the control group (91.5% versus 60.2%, P = 0.01). Medical events and QoL assessments showed a consistent trend for better results in the CCP group without reaching statistical significance. There was no difference in the increase in neutralizing antibodies after vaccination between the CCP and control groups. CONCLUSION. The trial demonstrated a trend toward better outcome in the CCP group without reaching statistical significance. A predefined subgroup analysis showed a significantly better outcome (long-term survival, time to discharge from ICU, and time to hospital discharge) among those who received a higher amount of neutralizing antibodies compared with the control group. A substantial long-term disease burden remains after severe COVID-19. Trial registration. EudraCT 2020-001310-38 and ClinicalTrials.gov NCT04433910. Funding. Bundesministerium für Gesundheit (German Federal Ministry of Health).

The COVID-19 course and immunity differ in children and adults. We analyzed immune response dynamics in 28 families up to 12 months after mild or asymptomatic infection. Unlike adults, the initial response is plasmablast-driven in children. Four months after infection, children show an enhanced specific antibody response and lower but detectable spike 1 protein (S1)-specific B and T cell responses than their parents. While specific antibodies decline, neutralizing antibody activity and breadth increase in both groups. The frequencies of S1-specific B and T cell responses remain stable. However, in children, one year after infection, an increase in the S1-specific IgA class switch and the expression of CD27 on S1-specific B cells and T cell maturation are observed. These results, together with the enhanced neutralizing potential and breadth of the specific antibodies, suggest a progressive maturation of the S1-specific immune response. Hence, the immune response in children persists over 12 months but dynamically changes in quality, with progressive neutralizing, breadth, and memory maturation. This implies a benefit for booster vaccination in children to consolidate memory formation.

In this prospective observational cohort study we analyzed cellular and serological immune response parameters against SARS-CoV-2 and current variants of concern (VOC) in 147 COVID-19-convalescent and 39 COVID-19-naïve individuals before and after BNT162b2 booster vaccination. No significant differences regarding immunological response parameters were observed between younger and older individuals. Booster vaccination induced full recovery of both cellular and serological response parameters including IFN-γ secretion and anti-spike antibody titers with strong neutralization capacities against wild type SARS-COV-2 and Delta. Surprisingly, even serological neutralization capacity against Omicron was detectable one month after second vaccination and four months before it had been first observed in South Africa. As a result, more than 90% of convalescent individuals exhibited detectable and 75% strong Omicron neutralization capacity after booster vaccination, compared with 72% and 46% of COVID-19-naïve individuals. Our results support the notion that broad and cross-reactive immune memory against SARS-CoV-2 including currently known VOCs can be established by booster vaccination with spike-based mRNA vaccines like BNT162b2, particularly in COVID-19-convalescent individuals of all ages. Nevertheless, especially in COVID-19-naïve individuals future variants escaping the memory immune response may require vaccine approaches such as inactivated whole virus vaccines, which include all antigenic components of the virus.

Transplant recipients exhibit an impaired protective immunity after SARS-CoV-2 vaccination, potentially caused by mycophenolate (MPA) immunosuppression. Recent data from patients with autoimmune disorders suggest that temporary MPA hold might greatly improve booster vaccination outcomes. We applied a fourth dose of SARS-CoV-2 vaccine to 29 kidney transplant recipients during a temporary (5 weeks) MPA/azathioprine hold, who had not mounted a humoral immune response to previous vaccinations. Seroconversion until day 32 after vaccination was observed in 76% of patients, associated with acquisition of virus-neutralizing capacity. Interestingly, 21/25 (84%) calcineurin inhibitor–treated patients responded, but only 1/4 belatacept-treated patients responded. In line with humoral responses, counts and relative frequencies of spike receptor binding domain–specific (RBD-specific) B cells were markedly increased on day 7 after vaccination, with an increase in RBD-specific CD27 ⁺⁺ CD38 ⁺ plasmablasts. Whereas overall proportions of spike-reactive CD4 ⁺ T cells remained unaltered after the fourth dose, frequencies were positively correlated with specific IgG levels. Importantly, antigen-specific proliferating Ki67 ⁺ and in vivo–activated programmed cell death 1–positive T cells significantly increased after revaccination during MPA hold, whereas cytokine production and memory differentiation remained unaffected. In summary, antimetabolite hold augmented all arms of immunity during booster vaccination. These data suggest further studies of antimetabolite hold in kidney transplant recipients.

Elderly residents of long-term care facilities (LTCFs) have long been underrepresented in studies on vaccine efficacy, particularly in light of currently emerging variants of concern (VOCs). In this prospective observational cohort study, we analyzed serological immune responses in 190 individuals before, 3 weeks after 1^st and 3 weeks after 2^nd vaccination with BNT162b2. Unvaccinated COVID-19-convalescent subjects served as reference. End points comprised serum anti-spike IgG and IgA titers as well as neutralization capacities against unmutated and mutated SARS-CoV-2 receptor binding domains including B.1.1.7, B.1.351 and P.1. We found that antibody titers and neutralization capacities up to 3 weeks after 2^nd vaccination with BNT162b2 were significantly higher in COVID-19-convalescent as compared to COVID-19-naive vaccinees. Moreover, pre-vaccination anti-NCP IgG titers, but not age or gender, had a high impact on the strength and kinetics of post-vaccination neutralization capacity development. Most importantly, BNT162b2-induced neutralization capacity was cross-reactive with VOCs. In contrast to unvaccinated convalescents, vaccinated convalescent individuals of all ages acquired strong neutralizing capacities against current VOCs. The present study suggests that COVID-19-convalescent individuals with a broad age range between 18 and 98 years benefit from BNT162b2 vaccination by developing strong and broad neutralizing immune responses against SARS-CoV-2 including current VOCs.

Der folgende Beitrag gibt einen Überblick über kommerziell erhältliche Testsysteme zur Untersuchung von Probenmaterial aus Blut auf verschiedene Antikörper gegen SARS-CoV-2. Dabei wird auch auf mögliche Anwendungen solcher Testungen eingegangen, angefangen von Seroprävalenz- und Longitudinalstudien über das Screening potenzieller Rekonvaleszenzplasmaspender bis hin zum Monitoring der humoralen Immunantwort nach Impfung gegen SARS-CoV-2. The following article provides an overview of commercially available test systems for screening blood samples for various antibodies against SARS-CoV-2. It also discusses possible applications of such testing, ranging from seroprevalence and longitudinal studies to screening of potential convalescent plasma donors and monitoring of the humoral immune response after vaccination against SARS-CoV-2. Publication Date: 27 August 2021 (online) © 2021. Thieme. All rights reserved. Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

To identify the most efficient methods of immunological protection against SARS-CoV-2, including the currently most widespread variants of concern (VOCs)—B.1.1.7, B.1.351 and P.1—a simultaneous side-by-side-comparison of available vaccination regimes is required. In this observational cohort study, we compared immunological responses in 144 individuals vaccinated with the mRNA vaccines BNT162b2 or mRNA-1273 and the vector vaccine ChAdOx1-nCoV-19, either alone, in combination, or in the context of COVID-19-convalescence. Unvaccinated COVID-19-convalescent subjects served as a reference. We found that cellular and serological immune responses, including neutralizing capacity against VOCs, were significantly stronger with mRNA vaccines as compared with COVID-19-convalescent individuals or vaccinated individuals receiving the vector vaccine ChAdOx1-nCoV-19. Booster immunizations with mRNA vaccines triggered strong and broadly neutralizing antibody and IFN-γ responses in 100% of vaccinated individuals investigated. This effect was particularly strong in COVID-19-convalescent and ChAdOx1-nCoV-19-primed individuals, who were characterized by comparably moderate cellular and neutralizing antibody responses before mRNA vaccine booster. Heterologous vaccination regimes and convalescent booster regimes using mRNA vaccines may allow enhanced protection against SARS-CoV-2, including current VOCs. Furthermore, such regimes may facilitate rapid (re-)qualification of convalescent plasma donors with high titers of broadly neutralizing antibodies.