Prophylactic antibodies inhibit spike-specific T and B cell responses after COVID-19 vaccination.

Active and passive immunization is used in high-risk patients to prevent severe courses of COVID-19, but the impact of prophylactic neutralizing antibodies on the immune reaction to the mRNA vaccines has remained enigmatic. Here we show that CD4 T and B cell responses to Spikevax booster immunization are suppressed by the therapeutic antibodies Casirivimab and Imdevimab. B cell and T cell responses were significantly induced in controls but not in antibody-treated patients. The data indicates that humoral immunity, i. e. high levels of antibodies, negatively impacts reactive immunity, resulting in blunted cellular responses upon boosting. This argues for temporal separation of vaccination efforts; with active vaccination preferably applied before prophylactic therapeutic antibody treatment.

Induction of robust cellular and humoral immunity against SARS-CoV-2 after a third dose of BNT162b2 vaccine in previously unresponsive older adults.

Here we compared SARS-CoV-2-specific antibody and T-cell responses between older adults (>80 years old, n = 51) and a younger control group (20-53 years old, n = 46) after receiving two doses of BNT162b2. We found that responses in older adults were generally lower, and we identified 10% low-/non-responders. After receiving a third vaccination with BNT162b2, 4 out of 5 low-/non-responders showed antibody and T-cell responses similar to those of responders after two vaccinations.

The Worm-Specific Immune Response in Multiple Sclerosis Patients Receiving Controlled Trichuris suis Ova Immunotherapy.

Considering their potent immunomodulatory properties, therapeutic applications of Trichuris suis ova (TSO) are studied as potential alternative treatment of autoimmune disorders like multiple sclerosis (MS), rheumatoid arthritis (RA), or inflammatory bowel disease (IBD). Clinical phase 1 and 2 studies have demonstrated TSO treatment to be safe and well tolerated in MS patients, however, they reported only modest clinical efficacy. We therefore addressed the cellular and humoral immune responses directed against parasite antigens in individual MS patients receiving controlled TSO treatment (2500 TSO p.o. every 2 weeks for 12 month). Peripheral blood mononuclear cells (PBMC) of MS patients treated with TSO (n = 5) or placebo (n = 6) were analyzed. A continuous increase of serum IgG and IgE antibodies specific for T. suis excretory/secretory antigens was observed up to 12 months post-treatment. This was consistent with mass cytometry analysis identifying an increase of activated HLA-DRhigh plasmablast frequencies in TSO-treated patients. While stable and comparable frequencies of total CD4+ and CD8+ T cells were detected in placebo and TSO-treated patients over time, we observed an increase of activated HLA-DR+CD4+ T cells in TSO-treated patients only. Frequencies of Gata3+ Th2 cells and Th1/Th2 ratios remained stable during TSO treatment, while Foxp3+ Treg frequencies varied greatly between individuals. Using a T. suis antigen-specific T cell expansion assay, we also detected patient-to-patient variation of antigen-specific T cell recall responses and cytokine production. In summary, MS patients receiving TSO treatment established a T. suis-specific T- and B-cell response, however, with varying degrees of T cell responses and cellular functionality across individuals, which might account for the overall miscellaneous clinical efficacy in the studied patients.

Characterization of pre-existing and induced SARS-CoV-2-specific CD8+ T cells.

Emerging data indicate that SARS-CoV-2-specific CD8+ T cells targeting different viral proteins are detectable in up to 70% of convalescent individuals1-5. However, very little information is currently available about the abundance, phenotype, functional capacity and fate of pre-existing and induced SARS-CoV-2-specific CD8+ T cell responses during the natural course of SARS-CoV-2 infection. Here, we define a set of optimal and dominant SARS-CoV-2-specific CD8+ T cell epitopes. We also perform a high-resolution ex vivo analysis of pre-existing and induced SARS-CoV-2-specific CD8+ T cells, applying peptide-loaded major histocompatibility complex class I (pMHCI) tetramer technology. We observe rapid induction, prolonged contraction and emergence of heterogeneous and functionally competent cross-reactive and induced memory CD8+ T cell responses in cross-sectionally analyzed individuals with mild disease following SARS-CoV-2 infection and three individuals longitudinally assessed for their T cells pre- and post-SARS-CoV-2 infection. SARS-CoV-2-specific memory CD8+ T cells exhibited functional characteristics comparable to influenza-specific CD8+ T cells and were detectable in SARS-CoV-2 convalescent individuals who were seronegative for anti-SARS-CoV-2 antibodies targeting spike (S) and nucleoprotein (N). These results define cross-reactive and induced SARS-CoV-2-specific CD8+ T cell responses as potentially important determinants of immune protection in mild SARS-CoV-2 infection.

IGLV3-21*01 is an inherited risk factor for CLL through the acquisition of a single-point mutation enabling autonomous BCR signaling.

The prognosis of chronic lymphocytic leukemia (CLL) depends on different markers, including cytogenetic aberrations, oncogenic mutations, and mutational status of the immunoglobulin (Ig) heavy-chain variable (IGHV) gene. The number of IGHV mutations distinguishes mutated (M) CLL with a markedly superior prognosis from unmutated (UM) CLL cases. In addition, B cell antigen receptor (BCR) stereotypes as defined by IGHV usage and complementarity-determining regions (CDRs) classify ∼30% of CLL cases into prognostically important subsets. Subset 2 expresses a BCR with the combination of IGHV3-21-derived heavy chains (HCs) with IGLV3-21-derived light chains (LCs), and is associated with an unfavorable prognosis. Importantly, the subset 2 LC carries a single-point mutation, termed R110, at the junction between the variable and constant LC regions. By analyzing 4 independent clinical cohorts through BCR sequencing and by immunophenotyping with antibodies specifically recognizing wild-type IGLV3-21 and R110-mutated IGLV3-21 (IGLV3-21R110), we show that IGLV3-21R110-expressing CLL represents a distinct subset with poor prognosis independent of IGHV mutations. Compared with other alleles, only IGLV3-21*01 facilitates effective homotypic BCR-BCR interaction that results in autonomous, oncogenic BCR signaling after acquiring R110 as a single-point mutation. Presumably, this mutation acts as a standalone driver that transforms IGLV3-21*01-expressing B cells to develop CLL. Thus, we propose to expand the conventional definition of CLL subset 2 to subset 2L by including all IGLV3-21R110-expressing CLL cases regardless of IGHV mutational status. Moreover, the generation of monoclonal antibodies recognizing IGLV3-21 or mutated IGLV3-21R110 facilitates the recognition of B cells carrying this mutation in CLL patients or healthy donors.

Surface Barcoding of Live PBMC for Multiplexed Mass Cytometry.

Sample barcoding is a powerful method for harmonizing mass cytometry data. By assigning a unique combination of barcode labels to each cell sample, a set of individual samples can be pooled and further processed and acquired as a large, single sample. For assays that require uncompromised profiling of cell-surface markers on live cells, barcoding by metal-labeled antibodies targeting cell-surface epitopes is the barcoding approach of choice. Here we provide an optimized and validated protocol for cell-surface barcoding of ten PBMC samples with palladium-labeled ß2-microglobulin (B2M) antibodies used in a 5-choose-2 barcoding scheme, for subsequent immune phenotyping by mass cytometry. We further provide details on the generation of palladium-labeled antibodies utilizing amine-reactive isothiocyanobenzyl-EDTA (ITCB-EDTA) that permits the implementation of antibody-based barcoding not interfering with lanthanide channels typically used for analyte detection in mass cytometry assays.

Age dependent differences in the kinetics of γδ T cells after influenza vaccination.

Immunosenescence is a hallmark of the aging immune system and is considered the main cause of a reduced vaccine efficacy in the elderly. Although γδ T cells can become activated by recombinant influenza hemagglutinin, their age-related immunocompetence during a virus-induced immune response has so far not been investigated. In this study we evaluate the kinetics of γδ T cells after vaccination with the trivalent 2011/2012 northern hemisphere seasonal influenza vaccine. We applied multi-parametric flow cytometry to a cohort of 21 young (19-30 years) and 23 elderly (53-67 years) healthy individuals. Activated and proliferating γδ T cells, as identified by CD38 and Ki67 expression, were quantified on the days 0, 3, 7, 10, 14, 17, and 21. We observed a significantly lower number of activated and proliferating γδ T cells at baseline and following vaccination in elderly as compared to young individuals. The kinetics changes of activated γδ T cells were much stronger in the young, while corresponding changes in the elderly occurred slower. In addition, we observed an association between day 21 HAI titers of influenza A and the frequencies of Ki67+ γδ T cells at day 7 in the young. In conclusion, aging induces alterations of the γδ T cell response that might have negative implications for vaccination efficacy.

Silver nanoparticles for the detection of cell surface antigens in mass cytometry.

Mass cytometry has pioneered >40-parameter single-cell analyses that allow for the characterization of complex cellular networks at unprecedented depth. Up to 135 parameters can be simultaneously detected, but limited availability of metal tags suitable for labeling of specific probes prevents optimal exploitation of the analytical capacity of mass cytometers. To this end, we here establish the application of elemental silver nanoparticles (AgNP) of different size for reporting cell surface antigens on human leukocytes in mass cytometry assays. The mass channels at 107 Da and 109 Da are uniquely occupied by silver isotopes and do not interfere with other mass cytometry reagents. Streptavidin-coated AgNP (SA-AgNP) facilitated distinct and specific detection of various antigens, such as CD8, CD244 and CD294 on peripheral blood leukocytes pre-incubated with respective biotinylated primary antibodies. Signal intensities elicited by 40 nm-sized AgNP allowed specific detection of the low abundance antigen CD25 on both, peripheral blood regulatory T cells and CD25lo CD127+ CD4+ T cells, enabling their distinct clustering in viSNE plots. SA-AgNP were of high elemental purity, showed minor background binding to cells in immunoassays, and were compatible with previously established staining protocols for PBMC and leukocytes, facilitating their use in complex mass cytometry panels. Considering the synthesis of AgNP from isotopically purified silver, the usage of AgNP extends the analytical capacity of mass cytometry panels by one, prospectively two, additional parameters, suitable for the detection of cellular targets of low abundance. © 2016 International Society for Advancement of Cytometry.

Highly Predictive Model for a Protective Immune Response to the A(H1N1)pdm2009 Influenza Strain after Seasonal Vaccination.

Understanding the immune response after vaccination against new influenza strains is highly important in case of an imminent influenza pandemic and for optimization of seasonal vaccination strategies in high risk population groups, especially the elderly. Models predicting the best sero-conversion response among the three strains in the seasonal vaccine were recently suggested. However, these models use a large number of variables and/or information post- vaccination. Here in an exploratory pilot study, we analyzed the baseline immune status in young (<31 years, N = 17) versus elderly (≥50 years, N = 20) donors sero-negative to the newly emerged A(H1N1)pdm09 influenza virus strain and correlated it with the serological response to that specific strain after seasonal influenza vaccination. Extensive multi-chromatic FACS analysis (36 lymphocyte sub-populations measured) was used to quantitatively assess the cellular immune status before vaccination. We identified CD4+ T cells, and amongst them particularly naive CD4+ T cells, as the best correlates for a successful A(H1N1)pdm09 immune response. Moreover, the number of influenza strains a donor was sero-negative to at baseline (NSSN) in addition to age, as expected, were important predictive factors. Age, NSSN and CD4+ T cell count at baseline together predicted sero-protection (HAI≥40) to A(H1N1)pdm09 with a high accuracy of 89% (p-value = 0.00002). An additional validation study (N = 43 vaccinees sero-negative to A(H1N1)pdm09) has confirmed the predictive value of age, NSSN and baseline CD4+ counts (accuracy = 85%, p-value = 0.0000004). Furthermore, the inclusion of donors at ages 31-50 had shown that the age predictive function is not linear with age but rather a sigmoid with a midpoint at about 50 years. Using these results we suggest a clinically relevant prediction model that gives the probability for non-protection to A(H1N1)pdm09 influenza strain after seasonal multi-valent vaccination as a continuous function of age, NSSN and baseline CD4 count.

Siglec-1-positive plasmacytoid dendritic cells (pDCs) in human peripheral blood: A semi-mature and myeloid-like subset imbalanced during protective and autoimmune responses.

Plasmacytoid dendritic cells (pDCs) play a central role in the pathogenesis of systemic lupus erythematosus (SLE) as IFN-α producers and promoters of T-cell activation or tolerance. Here, we demonstrated by flow-cytometry and confocal microscopy that Siglec-1, a molecule involved in the regulation of adaptive immunoresponses, is expressed in a subset of semi-mature, myeloid-like pDCs in human blood. These pDCs express lower BDCA-2 and CD123 and higher HLA-DR and CD11c than Siglec-1-negative pDCs and do not produce IFN-α via TLR7/TLR9 engagement. In vitro, Siglec-1 expression was induced in Siglec-1-negative pDCs by influenza virus. Proportions of Siglec-1-positive/Siglec-1-negative pDCs were higher in SLE than in healthy controls and correlated with disease activity. Healthy donors immunized with yellow fever vaccine YFV-17D displayed different kinetics of the two pDC subsets during protective immune response. PDCs can be subdivided into two subsets according to Siglec-1 expression. These subsets may play specific roles in (auto)immune responses.

Low Thymic Activity and Dendritic Cell Numbers Are Associated with the Immune Response to Primary Viral Infection in Elderly Humans.

Immunological competence declines progressively with age, resulting in increased susceptibility of the elderly to infection and impaired responses to vaccines. Underlying mechanisms remain largely obscure as they have been related to complex, individual systemic immune properties that are challenging to investigate. In this study, we explored age-related changes in human immunity during a primary virus infection experimentally induced by immunization with live-attenuated yellow fever (YF) vaccine. Applying detailed serology, advanced FACS analysis, and systems biology, we discovered that aged subjects developed fewer neutralizing Abs, mounted diminished YF-specific CD8(+) T cell responses, and showed quantitatively and qualitatively altered YF-specific CD4(+) T cell immunity. Among numerous immune signatures, low in vivo numbers of naive CD4(+) recent thymic emigrants and peripheral dendritic cells correlated well with reduced acute responsiveness and altered long-term persistence of human cellular immunity to YF vaccination. Hence, we reveal in this article that essential elements of immune responses such as recent thymic emigrants and dendritic cells strongly relate to productive immunity in the elderly, providing a conceivable explanation for diminished responsiveness to vaccination with neoantigens and infection with de novo pathogens in the aged population.

Effects of aging on human leukocytes (part I): immunophenotyping of innate immune cells.

Immunosenescence is a hallmark of the aging immune system, leading to increased susceptibility to infections in the aged population and decreased ability to eradicate infectious pathogens. These effects, in turn, result in an increased burden on the healthcare system due to elevated frequency and duration of hospital visits. Growing evidence suggests that cells of the innate immune system are central modulators for the initiation and maintenance of an adequate pathogen-specific response through the adaptive immune system. While there are many reports on age-dependent alterations and dysfunctions of the adaptive immune system, the underlying mechanisms and effects of natural aging on the composition of the innate immune system remain unknown. Here, we present the results obtained from the comprehensive immunophenotyping of innate leukocyte populations, examined for age-related alterations within different sub-populations assessed using multi-parametric flow cytometry. We compared peripheral blood mononuclear cells from 24 young (aged 19-30 years) and 26 elderly (aged 53-67 years) donors. For classical CD16(+)CD56(dim) NK cells, the fraction of CD62L(+)CD57(+) was diminished in the elderly donors compared with young individuals, while the other investigated NK subsets remained unaffected by age. Both transitional monocytes and non-classical CD14(+-)CD16(++) monocytes were increased in the elderly compared with the young. The populations of pDCs and mDC2 were decreased among the elderly. These data demonstrate that the dynamics of the mDC subsets might counteract decreased virus surveillance. Furthermore, these data show that the maturation of NK cells might gradually slow down.

Effects of aging on human leukocytes (part II): immunophenotyping of adaptive immune B and T cell subsets.

Immunosenescence results from a continuous deterioration of immune responses resulting in a decreased response to vaccines. A well-described age-related alteration of the immune system is the decrease of de novo generation of T and B cells. In addition, the accumulation of memory cells and loss of diversity in antigen specificities resulting from a lifetime of exposure to pathogens has also been described. However, the effect of aging on subsets of γδTCR(+) T cells and Tregs has been poorly described, and the efficacy of the recall response to common persistent infections in the elderly remains obscure. Here, we investigated alterations in the subpopulations of the B and T cells among 24 healthy young (aged 19-30) and 26 healthy elderly (aged 53-67) individuals. The analysis was performed by flow cytometry using freshly collected peripheral blood. γδTCR(+) T cells were overall decreased, while CD4(+)CD8(-) cells among γδTCR(+) T cells were increased in the elderly. Helios(+)Foxp3(+) and Helios(-)Foxp3(+) Treg cells were unaffected with age. Recent thymic emigrants, based on CD31 expression, were decreased among the Helios(+)Foxp3(+), but not the Helios(-)Foxp3(+) cell populations. We observed a decrease in Adenovirus-specific CD4(+) and CD8(+) T cells and an increase in CMV-specific CD4(+) T cells in the elderly. Similarly, INFγ(+)TNFα(+) double-positive cells were decreased among activated T cells after Adenovirus stimulation but increased after CMV stimulation. The data presented here indicate that γδTCR(+) T cells might stabilize B cells, and functional senescence might dominate at higher ages than those studied here.

Barcoding of live human peripheral blood mononuclear cells for multiplexed mass cytometry.

Mass cytometry is developing as a means of multiparametric single-cell analysis. In this study, we present an approach to barcoding separate live human PBMC samples for combined preparation and acquisition on a cytometry by time of flight instrument. Using six different anti-CD45 Ab conjugates labeled with Pd104, Pd106, Pd108, Pd110, In113, and In115, respectively, we barcoded up to 20 samples with unique combinations of exactly three different CD45 Ab tags. Cell events carrying more than or less than three different tags were excluded from analyses during Boolean data deconvolution, allowing for precise sample assignment and the electronic removal of cell aggregates. Data from barcoded samples matched data from corresponding individually stained and acquired samples, at cell event recoveries similar to individual sample analyses. The approach greatly reduced technical noise and minimizes unwanted cell doublet events in mass cytometry data, and it reduces wet work and Ab consumption. It also eliminates sample-to-sample carryover and the requirement of instrument cleaning between samples, thereby effectively reducing overall instrument runtime. Hence, CD45 barcoding facilitates accuracy of mass cytometric immunophenotyping studies, thus supporting biomarker discovery efforts, and it should be applicable to fluorescence flow cytometry as well.