Cohort design.
The study was approved by the Luxembourg National Research Ethics Committee (CNER) (SYS-T-Act: No. 201509/11) and registered at ClinicalTrials.gov (NCT02931955). Informed consent was obtained from each participant prior to sampling and personal data collecting, which were in full compliance with the Luxembourg National Commission for Data Protection (CNPD, before the implementation of GDPR in Europe). We obtained notification on 11th Sep, 2015 and modification approval on 17th Jul, 2017 from CNPD.
The study participants with moderate-to-severe allergic rhinitis (pollen allergy patients, PAP, n = 16) and insect sting reactions (venom allergy patients, VAP, n = 18) eligible for AIT in accordance with the current international guidelines were recruited at a tertiary center (Service National d’Immuno-Allergology of Centre Hospitalier de Luxembourg) between August 2016 and February 2018. The healthy controls (HC, n = 10) were recruited at the Clinical and Epidemiological Investigation Center of the Luxembourg Institute of Health (CIEC-LIH) between Jan and Apr 2018. The study was designed as a real-world, prospective, exploratory, data-driven trial for identification of novel potential biomarkers and molecular switches in the early time window of AIT in the outpatient clinical setting. The inclusion criteria were the confirmed clinical diagnosis of allergy (skin prick test positivity and elevated sIgE titers to plant pollen or insect venom allergens, respectively), clinical indication for launch of AIT for the patients and absence of known allergies for healthy volunteers. The exclusion criteria were age less than 18 years, pregnancy and lactation; overt asthma or chronic obstructive pulmonary disease, concomitant autoimmune disorders, chronic diseases in exacerbation or not adequately controlled, history of hematological malignancies or solid tumors, treatment with systemic steroids, immunomodulatory agents or biologics, acute and exacerbation of chronic infections, traumas and surgeries in six months prior to the study enrollment. No restrictions were introduced regarding the number of sensitizing allergens, duration of the allergic disease, the time elapsed since the last field sting and treatment with mono- versus polyvalent allergen immunotherapy products. In VAP, an ultra-rush AIT protocol was administered to reach the maintenance dose within 8 hours with 14 injections (Fig. 1A). For PAP, a conventional up-dosing AIT was applied to reach the maintenance dose within 6 weeks with a weekly injection scheme. Therefore, although the exact sampling periods are different between the two groups of patients, our sampling schemes allowed us to cover comparable periods (essentially build-up phase) until the beginning of the maintenance stage for both types of AIT.
While the age of the PAP was comparable to that of HC (median, ∼37 and ∼35 years, respectively, Table S1), VAP were older (median, ∼49 years). While both patient groups included male and female participants at almost 1:1 ratio, the HC group was predominantly female (9 of 10). Five of 16 PAP were sensitized to major birch pollen allergen (Bet v1), two of 16 exhibited elevated sIgE and clinical reactivity to timothy grass pollen allergens (Phl p1 & Phl p5) and eight were allergic to the pollen of both species. One PAP was timothy grass pollen-allergic, but the sIgE results were not available. Most VAP (14 of 18) presented with a history of systemic reactions to wasp (yellow jacket; Vespula spp.) stings, being sensitized to Ves v1 (one of 18), Ves v5 (eight of 18) or both allergens (five of 18). Three of four bee VAP showed elevated sIgE levels to both Api m1 and Api m5, another VAP being mono-sensitized to Api m1. Two VAP are hobby beekeepers.
On the first day of the ultra-rush protocol, most of the VAP received their first injection at 8:00 AM with a gradually increasing dose in µg (i.e., starting from 0.003 to 0.006, 0.015, 0.030, 0.060, 0.150, 0.30, 0.60, 1.50, 3.00, 6.00, 15.00, 30.00, ending with 55.00) at 15-min intervals. While the baseline (0h) blood sample was drawn at 8:00 AM, the second blood sample (8h) was taken at 16:00. There were a few cases, where the first injection was given at 8:15 AM and then the afternoon sampling was delayed to 16:15. Biological samples were collected by trained study nurses, transported at room temperature (RT) within maximum two hours to the bio-specimen laboratory of the Integrated Biobank of Luxembourg (IBBL), where they were either used freshly in the experiments on the same day, or cryopreserved in the IBBL biorepository for further analysis later on.
Isolation and cryopreservation of PBMCs.
PBMCs (peripheral blood mononuclear cells) were obtained from fresh whole blood by density gradient immediately followed by CD4 T-cell isolation and Th2 sorting or cryopreservation. For PBMC isolation and deep immunophenotyping analysis, we followed a similar procedure as we described in another clinical study (Capelle et al. 2022). Briefly, we collected up to 50 ml of blood per patient at each time point. 40ml were collected in BD ACD tubes for PBMC analyses and 10ml in BD EDTA tubes for whole-blood-count and cytokine measurements. We first added 13 ml of Ficoll Paque Plus (GE17-1440-02, Merck) at the bottom of the Falcon tubes. Blood from ACD tubes was mixed and split into two 50-ml Falcon tubes that were diluted with up to a total volume of 35ml with DPBS (14190144, Thermo Fisher Scientific). Diluted blood was added carefully on the top of Ficoll-containing Falcon tubes. The Falcon tubes were then centrifuged at 400g at room temperature (RT) for 30 min. The PBMC layer was collected, diluted with DPBS plus 2% heat-inactivated FBS (fetal bovine serum, 10500-064, Thermo Fisher Scientific) and centrifuged twice at 300g for 10 min at RT. Purified PBMCs were either cryopreserved using 90% heat-inactivated FBS plus 10%DMSO (D2650, Sigma Aldrich) freezing medium and stored in liquid nitrogen or used freshly to isolate CD4 + T cells as described below. The plasma layer was also collected during the PBMC isolation process. Whole-blood-count data were measured by ABX Micros CRP 200 (Horiba, Axonlab) and plasma were isolated from fresh blood collected in 10 ml BD EDTA tubes.
Single-cell mass cytometry (CyTOF) measurement, analysis and visualization.
Peripheral blood mononuclear cells (PBMCs) were isolated and stored in liquid nitrogen until the day of the staining when the cryovials were thawed using warm DMEM 4.5 g/L Glucose with L-Glutamine (BE12-604F, Lonza) containing 5% of FBS (10500-064, Thermo Fischer Scientific) and 2 mM EDTA (15575-038, Invitrogen). Cells were then washed with PBS (17-516F, Lonza). Prior to the metal-conjugated antibody staining and for assessing their viability, cells were re-suspended at a concentration of 1 x 107 /1 mL and were incubated for 5 min at RT with Cell-ID Cisplatin (201064, Fluidigm) at a final concentration of 1 µM. The incubation was stopped by adding the staining buffer (PBS, 5%FBS, 2 mM EDTA; of note, EDTA was not used in other scenarios unless specified). Surface staining was performed by adding a cocktail of pre- or in-house-conjugated antibodies (Table S2) for 30 min at RT; excess antibodies were removed by washing (400g, RT, 10 min). It is important to mention that each tube was then split into half for introducing intense washing steps since the samples had initially shown strong signals of iodine (most probably coming from the Ficoll). As a last step, samples were incubated with Ir-Intercalator (201192B, Fluidigm), diluted in MaxPar Fix&Perm (201067, Fluidigm) at a final concentration of 50 nM, and rested at 4oC until the day of the acquisition. Prior to the acquisition, cells were washed twice with PBS and with de-ionized water two times. Centrifugation conditions after fixation, on the acquisition day, were 800g, for 10 min at 4oC. Cells were re-suspended at 5 x 105 per ml in 1:10 calibration beads (EQ Four Element Calibration Beads, 201078, Fluidigm), diluted with de-ionized water and the samples were analyzed with the Helios™ mass cytometer (Fluidigm) at a flow rate of 0.030 mL per min. Generated .fcs files were normalized with the HELIOS acquisition software (v 7.0.5189) by using EQ beads as a standard. Unless otherwise specified, the indicated frequency of the given subset was always relative to the total living singlets (for the full gating strategy, please refer to Figure S1). Statistical analysis of supervised CyTOF analysis was done in Qluocore Omics Explore v 3.8 (1). The non-paired two-tailed Mann-Whitney test was applied to compare the immune subsets between different groups at the given matched time point while paired two-tailed Mann-Whitney test was used to compare the AIT response or natural immune fluctuations between a later time point and baseline from the same patients or controls. The volcano plot was visualized in Graphpad Prism v9.0. Of note, due to technical staining issues, the number of samples used for TCRγδ analysis (n = 149) was lower than that for the other immune subsets (n = 199) (for details regarding TCRγδ staining on which sample, participant and time point, please refer to our i3Dare website).
Although our CyTOF data was essentially analyzed by the supervised manual gating as described above, we also independently validated our discoveries of several selected subsets of interest (only Fig. 3C, 3H) by our unsupervised clustering and visualization methods. The unsupervised clustering analysis was performed using the pre-gated living singlets. Pre-gating of identifying live singlets was done in FlowJo v10. Lineage markers used for clustering have been arcsin transformed using a co-factor of 5. Unsupervised clustering has been performed using GigaSOM (https://github.com/LCSB-BioCore/GigaSOM.jl). GigaSOM is a FlowSOM-style clustering and dimension reduction method, but adapted for our huge-scale data sets with ~ 200 million of cells using the high performance computing system in the Julia programming language (v 1.4). Of note, the analysis and visualization was performed without down-sampling. High resolution clustering settings were 32x32 SOM-grid, 40 rounds (epochs) and exponential radius decay. The 1024 clusters were annotated to different immune cell subsets according to the marker combinations similar to that established in the manual gating strategy (Figure S1). The plot (Fig. 2A, 3C, 3H) was visualized using EmbedSOM v2 (https://github.com/exaexa/EmbedSOM). The representation of a two-dimensional embedding of each single cell has been performed using the default settings of EmbedSOM.
Measurement of circulating cytokine levels by the MSD assay.
Ten analysts were either cytokines or chemokines (IFN-γ, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12p70, IL-13 and TNF-α) measured in plasma samples (isolated from EDTA tubes) from patients and healthy controls at all time points using a multiplexing assay [The V-Plex Proinflammatory Panel 1 (hu) assay from MSD, kit catalog K15049D-1]. The samples were undiluted and measured in duplicates. The assay was performed according to the manufacturer’s instructions. Data were recorded and analyzed on a MESO QuickPlex SQ 120 instrument (software version LSR_4_0_12).
Analysis of intracellular cytokines in B cells following CpG stimulation.
Detection of IL-10 production in human B cells followed the procedures described elsewhere (Menon et al. 2021). Nine samples were selected from those collected at baseline and 8h per participant group (either VAP or HC). The reason why only nine samples per group were selected was that we had to analyze both Bregs and kinome simultaneously to save precious clinical samples, where the number of sample spots was a limiting factor in the available chips for the kinome analysis. We selected VAP samples based on the top ranking of the plasma IL-6 level fold-changes between 8h vs baseline while randomly selecting nine out of ten HC samples per time point. Following the thawing of bio-banked cryopreserved PBMC depleted of CD4 T cells [refer to the section ‘Isolation and cryopreservation of PBMCs’], we re-suspended those cells in RPMI complete media (RPMI-1640 supplemented with 100 U/ml Penicillin, 100 µg/ml Streptomycin, 2 mM L-Glutamine and 10% heat-inactivated FBS). 8.5 x 105 cells were stimulated by 1 µM of CpG (ODN2395, Invivogen) for 72h in 200 µl of RPMI complete media with a U-bottom 96-well plate. In the last 4.5h before staining, 50 ng/ml PMA, 250 ng/ml Ionomycin plus 1 µl of BD Golgiplug were added together. The cells were then washed (200g, 10 min, 4oC) and blocked with Fc blocker (BD) for 5 min at 4oC. The cells were again washed and stained with the surface marker antibody mastermix (CD3 BUV737, 741822, BD; CD19 PercP-Cy5.5, 45-0199-42, Invitrogen; LIVE/DEAD Fixable Near-IR Dead Cell Stain, L10119, Thermo Fisher Scientific) in BD Brilliant stain buffer at 4oC for 30 min. The cells were subsequently stained with selected cytokine antibodies (IL-10-APC, 506807, Biolegend; TNF-a-BV650, 502938, Biolegend) using the Fixation/Permeablization kit (554714, BD) following the manufacture’s recommendations. The cells were finally re-suspended in the staining buffer (2% FBS in Ca2+/Mg2+ free PBS) and acquired in a BD LSRFortessa™ (v8.0.1). The Breg stimulation results were analyzed in Kaluza software (v2.1, Beckman).
Ex-vivo human kinome analysis using the PamGene array.
The same nine samples of the patient groups (refer to the rationale of selecting these nine samples above) processed for Breg analysis were also utilized to asses kinase activity using PamGene’s (PamGene International B.V., HH's-Hertogenbosch, the Netherlands) phosphotyrosine kinase (PTK) and serine-threonine kinase (STK) assay. Following the thawing of bio-banked PBMCs depleted of CD4 T cells [refer to the section ‘Isolation and cryopreservation of PBMCs’], cells were directly (without any in-vitro treatment) pelleted (800g, 5 min, 4oC) before resuspension in 1ml ice-cold PBS and pelleted (1000g, 10 min, 4oC). Pellets were lysed with 45 µl of M-PER (78501, Thermo Fisher Scientific) supplemented with Halt Phosphatase Inhibitor Cocktail (78428, Thermo Fisher Scientific) and Halt Protease Inhibitor Cocktail, EDTA free (78437, Thermo Fisher Scientific) for 15 min on ice. The lysate was clarified (10,000g, 15 min, 4oC) before preparing 10 µl aliquots, each snap frozen in liquid nitrogen before storage at -80oC. One aliquot was used for protein quantification by Bradford.
Adopting a balanced design, a separate aliquot of cell lysate was assessed on the PTK chip (86402, PamGene) and the STK chip (87102, PamGene) using the manufacturer's protocol. From each chip, a series of images describing the phosphorylation of peptides (196 for PTK and 144 for STK) corresponding to ~ 350 native kinases in the applied lysate was obtained. Using the instrument manufacturer’s BioNavigator software (v6.3.67.0), data was curated and normalized by chip using COMBAT. Upstream kinase analysis, a multiple hypothesis testing approach, identifies responsible kinases for the changes in peptide phosphorylation observed. R v4.1.1 was used to compile the results and to display them using an adaptation of the CORAL tool (https://github.com/dphansti/CORAL).
Principal component analysis (PCA) and integrative analysis.
Based on the ‘corr’ function in MATLAB 2020a, the correlation coefficient matrixes within or between different datasets were calculated (e.g., within different immune subsets, between immune subsets and cytokines). Since the datasets often do not follow a normal distribution, the ‘Spearman’ correlation coefficient was employed for the correlation analysis described in this section. The continuous range of correlation coefficients is (-1, + 1). The P-values following the two-tailed test were also directly generated by the 'corr' function. When the P-value is less than 0.05, we considered that the corresponding correlation coefficient was significantly different from zero.
The principal component analysis (PCA) was performed on the default setting of the ‘pca’ function in MATLAB 2020a. Considering different types of datasets, different groups of participants and different sampling time points, we divided the analysis into two categories. One type was to analyze the sample distribution between different participant groups using different combinations of datasets at a fixed sampling time point; the second type was to analyze time evolution responses within a fixed participant group. Before the PCA analysis, all the data were centered by ‘zscore’ function so that each variable had a mean value of 0 and a standard deviation of 1. In order to compare the changes of the overall immune features of each patient following immunotherapy (or each healthy control following the sampling period), we calculated the average distance among pairs of the adjacent two time points of each participant in the two-dimensional PCA plots. The larger the distance is, the more the overall peripheral immune system of the given subject has changed over the sampling period either caused by immunotherapy and/or natural fluctuation. Of note, each plot in the time-slice PCA figure (Fig. 2B and Figure S2D) is independent and different PCA plots were draw together only for better visualization.
Th2-cell-type-specific RNA-seq analysis.
Sorting Th2 cells and cell-type-specific mRNA sequencing
Following the PBMC isolation from fresh blood, CD4 + T cells were first enriched with human CD4 microbeads (130-045-101, Miltenyl Biotec) following the manufacture’s recommendations while the remaining fractions of PBMC were immediately cryopreserved as described above. The CD4 + T cells were then immediately shipped at 4°C to our sorting flow-cytometry facility. The CD4 + T cells were first stained in Brilliant Stain Buffer (563794, BD) using all the Abs with specified dilution factors and configuration settings as defined in Table S4. Samples were incubated for 30 min at 4°C in the dark (and briefly vortexed once after 15 min). After two washes at 350g, 10 min, 4°C, the cells were re-suspended at a concentration of 10 million per ml and aseptically sorted (20 PSI, 100 µm nozzle, purity mode) in a BD Aria III sorter (for the FACS gating strategy, please refer to Figure S6A). After sorting, cells were centrifuged at 350g, 10 min, 4°C, pelleted and lysed in 700 µl of the Qiazol buffer (Qiagen). The samples were transferred into 1.5 ml Eppendorf tubes and immediately frozen at -80°C until RNA extraction. RNA was extracted using RNeasy Micro kit (Qiagen) following the manufacture’s recommendations. RNA-seq was performed at the EMBL Genomics Core Facility (Heidelberg, Germany) using single-read 75bp high output by NextSeq 500 with ~ 50 Million reads/sample. The NEBNext Ultra II RNA Library Prep Kit was used and the rRNA deletion step was included.
Th2-cell-specific RNA-seq pre-processing and quality control
Quality control of the raw sequencing data was conducted using the FastQC software (v0.11.7-Java-1.8.0_162) (https://www.bioinformatics.babraham.ac.uk/projects/fastqc/). Reads were mapped to the reference human genome 38 (http://hgdownload.soe.ucsc.edu/goldenPath/hg38/bigZips/) and summarized to genes using the R Bioconductor Rsubread package (v1.32.4). One sample was excluded for further analysis because CD127 Ab was forgotten to add before sorting.
Analysis of potential confounding factors
Clinical and demographic factors that are significantly different between groups can have a confounding effect on subsequent analyses if no correction for these factors is applied. The following statistical tests were conducted to identify potential confounding factors. For categorical variables, a Fisher’s exact test was performed, whereas for normally distributed numerical variables having equal variances, one-way ANOVA was applied. In case of a normally distributed variable with unequal variances between the groups, Welch one-way test was used. For non-normally distributed values, the Kruskal-Walls rank sum test was employed. Homogeneity of variances was determined using Levene’s test, while normality was tested using quantile-quantile (Q-Q) plots.
Filtering, normalization, voom transformation and quality control
Genes that consistently had zero or very low counts were first removed using the Bioconductor edgeR package (v3.24.3). Trimmed Mean of M-values (TMM) normalization was performed on the filtered data with the edgeR package. The normalized data were voom-transformed to enable differential expression analysis with the Bioconductor limma package (v3.38.3). Principal component analysis (PCA) was performed on the voom-transformed data, and a score plot was presented where each batch was represented by a different colored symbol. In case of no batch effect, the batches do not cluster in the PCA plot. Furthermore, a principal coordinate analysis (PCoA) was conducted with the R Stats package and the score plot was inspected to check for potential outliers.
Differential expression and enrichment analysis
Differentially-expressed genes (DEGs) between allergic patients and controls, and between AIT-treated samples and baseline were determined by applying an empirical Bayes moderated t-test on the voom-transformed data, implemented in the R Bioconductor limma package (v3.38.3). Nominal p-values were corrected for multiple hypothesis testing by computing false discovery rates (FDR) according to the Benjamini-Hochberg procedure and using an FDR significance threshold of 0.05. Entrez gene IDs were converted to gene symbols with the R Bioconductor org.Hs.eg.db package (v3.7.0). DEGs were visualized in heatmaps and volcano plots using the R Bioconductor ComplexHeatmap (v1.20.0) and R ggplot2 (v3.2.0) packages, respectively.
Enriched differentially-regulated pathways and GO (Gene Ontology) biological processes were determined by over-representation analysis in ConsensusPathDB (release 34, http://cpdb.molgen.mpg.de/ ) using all measured genes as background list. Pathways were selected from Reactome, KEGG, Wikipathways, Biocarta and PID. Pathways and GO biological processes with Benjamini-Hochberg corrected FDR ≤ 0.05 were considered significant.
Interactive and interlinked resource (‘i3Dare’) sharing
To enhance the re-usability of our valuable clinical immunology resource, we employed the business intelligence tool Tableau to integrate and share various datasets in a website (Hedin et al. 2021), allowing investigators to scrutinize all our results in an user-friendly, interactive and interlinked manner. In the manuscript, we could not show the dynamic response patterns of each measured immune subset following AIT. However, in our resource website, for each measured immune subset, independent of significance levels and change folds, following the click, one can visualize and explore its dynamic response pattern following the launch of AIT in different patient groups. Importantly, through our interactive website, each subset in each volcano plot can be related to its dynamic response pattern over time. It is also possible to compare the dynamic responses between different immune subsets, which is not realizable for any static figures. Moreover, one can also explore immune responses of each individual patient at different time points following the launch of AIT, or benchmark the measurements of clinical samples with our reference datasets generated from HC or VAP or PAP.