Single-cell RNA sequencing identifies precise tolerogenic cellular and molecular pathways induced by depigmented-polymerized grass pollen allergen extract.

BACKGROUND: Immunologic mechanism of action of allergoids remains poorly understood. Previous models of allergenicity and immunogenicity have yielded suboptimal knowledge of these immunotherapeutic vaccine products. Novel single-cell RNA sequencing technology offers a bridge to this gap in knowledge. OBJECTIVE: We sought to identify the underpinning tolerogenic molecular and cellular mechanisms of depigmented-polymerized Phleum pratense (Phl p) extract. METHODS: The molecular mechanisms underlying native Phl p, depigmented Phl p (DPG-Phl p), and depigmented-polymerized (DPG-POL-Phl p) allergoid were investigated by single-cell RNA sequencing. Allergen-specific TH2A, T follicular helper (Tfh), and IL-10+ regulatory B cells were quantified by flow cytometry in peripheral blood mononuclear cells from 16 grass pollen-allergic and 8 nonatopic control subjects. The ability of Phl p, DPG-Phl p, and DPG-POL-Phl p to elicit FcεRI- and FcεRII-mediated IgE responses was measured by basophil activation test and IgE-facilitated allergen binding assay. RESULTS: Analysis revealed that DPG-POL-Phl p downregulated genes associated with TH2 signaling, induced functional regulatory T cells exhibiting immunosuppressive roles through CD52 and Siglec-10, modulated genes encoding immunoproteasome that dysregulate the processing and presentation of antigens to T cells and promoted a shift from IgE toward an IgA1 and IgG responses. In grass pollen-allergic subjects, DPG-POL-Phl p exhibited reduced capacity to elicit proliferation of TH2A, IL-4+ Tfh and IL-21+ Tfh cells while being the most prominent at inducing IL-10+CD19+CD5hi and IL-10+CD19+CD5hiCD38intCD24int regulatory B-cell subsets compared to Phl p (all P < .05). Furthermore, DPG-POL-Phl p demonstrated a hypoallergenic profile through basophil activation and histamine release compared to Phl p (31.54-fold, P < .001). CONCLUSIONS: Single-cell RNA sequencing provides an in-depth resolution of the mechanisms underlying the tolerogenic profile of DPG-POL-Phl p.

Diverse immune mechanisms of allergen immunotherapy for allergic rhinitis with and without asthma.

Allergen immunotherapy (AIT) is an effective treatment for allergic rhinitis, inducing long-term clinical tolerance to the sensitizing allergen. Clinical tolerance induction can be achieved when AIT is administered for at least 3 years. AIT is associated with the modulation of innate and adaptive immune systems. This comprises inhibition of IgE-dependent activation of mast cells and basophils in the local target organ, suppression of TH2 cells, immune deviation toward TH1 cells, induction of T and B regulatory cells, and production of allergen-neutralizing antibodies. However, recent developments in their underpinning mechanisms have revealed that AIT, administered subcutaneously or sublingually, induces immune regulation through novel cell targets and molecular mechanisms. This comprehensive review discusses how immune tolerance driven by subcutaneous immunotherapy and sublingual immunotherapy is associated with the induction of a novel regulatory subset of innate lymphoid cells and suppression of proinflammatory TH2, allergen-specific TH2 (TH2A), and T follicular helper cells. Moreover, they are associated with exhaustion of TH2A cells and differential expression of nasal and systemic IgA antibodies. Uncovering the underpinning mechanisms of a successful AIT and immune tolerance induction will allow the development of targeted therapeutics for allergic rhinitis with and without asthma.

Passive Prophylactic Administration with a Single Dose of Anti-Fel d 1 Monoclonal Antibodies REGN1908-1909 in Cat Allergen-induced Allergic Rhinitis: A Randomized, Double-Blind, Placebo-controlled Clinical Trial.

Rationale: Sensitization to Fel d 1 (Felis domesticus allergen 1) contributes to persistent allergic rhinitis and asthma. Existing treatment options for cat allergy, including allergen immunotherapy, are only moderately effective, and allergen immunotherapy has limited use because of safety concerns. Objectives: To explore the relationship among the pharmacokinetic, clinical, and immunological effects of anti-Fel d 1 monoclonal antibodies (REGN1908-1909) in patients after treatment. Methods: Patients received REGN1908-1909 (n = 36) or a placebo (n = 37) in a phase 1b study. Fel d 1-induced basophil and IgE-facilitated allergen binding responses were evaluated at baseline and Days 8, 29, and 85. Cytokine and chemokine concentrations in nasal fluids were measured, and REGN1908-1909 inhibition of allergen-IgE binding in patient serum was evaluated. Measurements and Main Results: Peak serum drug concentrations were concordant with maximal observed clinical response. The anti-Fel d 1 IgE/cat dander IgE ratio in pretreatment serum correlated with Total Nasal Symptom Score improvement. The allergen-neutralizing capacity of REGN1908-1909 was observed in serum and nasal fluid and was detected in an inhibition assay. Type 2 cytokines (IL-4, IL-5, and IL-13) and chemokines (CCL17/TARC, CCL5/RANTES [regulated upon activation, normal T-cell expressed and secreted]) in nasal fluid were inhibited in REGN1908-1909-treated patients compared with placebo (P < 0.05 for all); IL-13 and IL-5 concentrations correlated with Total Nasal Symptom Score improvement. Ex vivo assays demonstrated that REGN1908 and REGN1909 combined were more potent than each alone for inhibiting FcεRI- and FcεRII (CD23)-mediated allergic responses and subsequent T-cell activation. Conclusions: A single, passive-dose administration of Fel d 1-neutralizing IgG antibodies improved nasal symptoms in cat-allergic patients and was underscored by suppression of FcεRI-, FcεRII-, and T-helper cell type 2-mediated allergic responses. Clinical trial registered with www.clinicaltrials.gov (NCT02127801).

Altered chromatin landscape in circulating T follicular helper and regulatory cells following grass pollen subcutaneous and sublingual immunotherapy.

BACKGROUND: Allergen-specific immunotherapy is a disease-modifying treatment that induces long-term T-cell tolerance. OBJECTIVE: We sought to evaluate the role of circulating CXCR5+PD-1+ T follicular helper (cTFH) and T follicular regulatory (TFR) cells following grass pollen subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT) and the accompanying changes in their chromatin landscape. METHODS: Phenotype and function of cTFH cells were initially evaluated in the grass pollen-allergic (GPA) group (n = 28) and nonatopic healthy controls (NAC, n = 13) by mathematical algorithms developed to manage high-dimensional data and cell culture, respectively. cTFH and TFR cells were further enumerated in NAC (n = 12), GPA (n = 14), SCIT- (n = 10), and SLIT- (n = 8) treated groups. Chromatin accessibility in cTFH and TFR cells was assessed by assay for transposase-accessible chromatin sequencing (ATAC-seq) to investigate epigenetic mechanisms underlying the differences between NAC, GPA, SCIT, and SLIT groups. RESULTS: cTFH cells were shown to be distinct from TH2- and TH2A-cell subsets, capable of secreting IL-4 and IL-21. Both cytokines synergistically promoted B-cell class switching to IgE and plasma cell differentiation. Grass pollen allergen induced cTFH-cell proliferation in the GPA group but not in the NAC group (P < .05). cTFH cells were higher in the GPA group compared with the NAC group and were lower in the SCIT and SLIT groups (P < .01). Time-dependent induction of IL-4, IL-21, and IL-6 was observed in nasal mucosa following intranasal allergen challenge in the GPA group but not in SCIT and SLIT groups. TFR and IL-10+ cTFH cells were induced in SCIT and SLIT groups (all, P < .01). ATAC-seq analyses revealed differentially accessible chromatin regions in all groups. CONCLUSIONS: For the first time, we showed dysregulation of cTFH cells in the GPA group compared to NAC, SCIT, and SLIT groups and induction of TFR and IL-10+ cTFH cells following SCIT and SLIT. Changes in the chromatin landscape were observed following allergen-specific immunotherapy in cTFH and TFR cells.

Allergen-specific IgG+ memory B cells are temporally linked to IgE memory responses.

BACKGROUND: IgE is the least abundant immunoglobulin and tightly regulated, and IgE-producing B cells are rare. The cellular origin and evolution of IgE responses are poorly understood. OBJECTIVE: The cellular and clonal origin of IgE memory responses following mucosal allergen exposure by sublingual immunotherapy (SLIT) were investigated. METHODS: In a randomized double-blind, placebo-controlled, time course SLIT study, PBMCs and nasal biopsy samples were collected from 40 adults with seasonal allergic rhinitis at baseline and at 4, 8, 16, 28, and 52 weeks. RNA was extracted from PBMCs, sorted B cells, and nasal biopsy samples for heavy chain variable gene repertoire sequencing. Moreover, mAbs were derived from single B-cell transcriptomes. RESULTS: Combining heavy chain variable gene repertoire sequencing and single-cell transcriptomics yielded direct evidence of a parallel boost of 2 clonally and functionally related B-cell subsets of short-lived IgE+ plasmablasts and IgG+ memory B cells. Mucosal grass pollen allergen exposure by SLIT resulted in highly diverse IgE and IgGE repertoires. These were extensively mutated and appeared relatively stable as per heavy chain isotype, somatic hypermutations, and clonal composition. Single IgGE+ memory B-cell and IgE+ preplasmablast transcriptomes encoded antibodies that were specific for major grass pollen allergens and able to elicit basophil activation at very low allergen concentrations. CONCLUSION: For the first time, we have shown that on mucosal allergen exposure, human IgE memory resides in allergen-specific IgG+ memory B cells. These cells rapidly switch isotype, expand into short-lived IgE+ plasmablasts, and serve as a potential target for therapeutic intervention.

Immunologic mechanisms of a short-course of Lolium perenne peptide immunotherapy: A randomized, double-blind, placebo-controlled trial.

BACKGROUND: A 3-week short-course of adjuvant-free hydrolysates of Lolium perenne peptide (LPP) immunotherapy for rhinoconjunctivitis with or without asthma over 4 physician visits is safe, well tolerated, and effective. OBJECTIVE: We sought to investigate immunologic mechanisms of LPP immunotherapy in a subset of patients who participated in a phase III, multicenter, randomized, double-blind, placebo-controlled trial (clinical.govNCT02560948). METHODS: Participants were randomized to receive LPP (n = 21) or placebo (n = 11) for 3 weeks over 4 visits. Grass pollen-induced basophil, T-cell, and B-cell responses were evaluated before treatment (visit [V] 2), at the end of treatment (V6), and after the pollen season (V8). RESULTS: Combined symptom and rescue medication scores (CSMS) were lower during the peak pollen season (-35.1%, P = .03) and throughout the pollen season (-53.7%, P = .03) in the LPP-treated group compared with those in the placebo-treated group. Proportions of CD63+ and CD203cbrightCRTH2+ basophils were decreased following LPP treatment at V6 (10 ng/mL, P < .0001) and V8 (10 ng/mL, P < .001) compared to V2. No change in the placebo-treated group was observed. Blunting of seasonal increases in levels of grass pollen-specific IgE was observed in LPP-treated but not placebo-treated group. LPP immunotherapy, but not placebo, was associated with a reduction in proportions of IL-4+ TH2 (V6, P = .02), IL-4+ (V6, P = .003; V8, P = .004), and IL-21+ (V6, P = .003; V8, P = .002) follicular helper T cells. Induction of FoxP3+, follicular regulatory T, and IL-10+ regulatory B cells were observed at V6 (all P < .05) and V8 (all P < .05) in LPP-treated group. Induction of regulatory B cells was associated with allergen-neutralizing IgG4-blocking antibodies. CONCLUSION: For the first time, we demonstrate that the immunologic mechanisms of LPP immunotherapy are underscored by immune modulation in the T- and B-cell compartments, which is necessary for its effect.

Heterologous prime-boost with mRNA-1273 stimulates persistent neutralising antibodies in BBIBP-CorV-vaccinated individuals.

BBIBP-CorV inactivated vaccine is one of the most prevalent vaccines globally, but immune responses are far less studied than novel COVID-19 vaccine platforms. Longitudinal studies on BBIBP-CorV with homologous and heterologous booster doses are limited. This study follows a subset of participants from a national study comparing the immunogenicity of COVID-19 vaccines and levels of SARS-CoV-2 neutralising antibody (NAb). Homologous and heterologous booster dose significantly increased NAb levels in BBIBP-CorV-vaccinated individuals. Similar NAb levels were observed 1 month following BNT162b2 or mRNA-1273 booster. Interestingly, NAb persisted following mRNA-1273 booster (n = 95), but waned significantly at 6 and 9 months following BNT162b2 booster (n = 50; P > 0.001). The persistence of NAb was also observed following breakthrough infection. This study provides evidence that not all mRNA vaccines are equal in the longer term and should provide valuable information for policy makers planning booster programmes for BBIBP-CorV vaccinated populations.

Technology-assisted adaptive recruitment strategy for a large nation-wide COVID-19 vaccine immunogenicity study in Brunei.

A national study was conducted in Brunei to assess and compare the immunogenicity of the various brands of COVID-19 vaccines administered to the population as part of the National COVID-19 Vaccination Programme. Most of the population have had received at least 2 doses of BBIBP-CorV, AZD1222 or MRNA-1273 vaccines. Neutralising antibodies against SARS-CoV-2 induced by these vaccines will be analysed to infer population-level immune protection against COVID-19. During the 5-week recruitment period, 24,260 eligible individuals were invited to the study via SMS, out of which 2,712 participants were enrolled into the study. This paper describes the novel adaptive strategy used to recruit the study participants. Digital technology was leveraged to perform targeted online recruitment to circumvent the limitations of traditional recruitment methods. Technology also enabled stratified random selection of these eligible individuals who were stratified based on age, gender and vaccine brand. Data was extracted from the electronic health records, the national mobile health application and a third-party survey platform and integrated into a dedicated research platform called EVYDResearch. The instant availability and access to up-to-date data on EVYDResearch enabled the study team to meet weekly and adopt an adaptive recruitment strategy informed by behavioural science, where interventions could be quickly implemented to improve response rates. Some examples of these include incorporating nudge messaging into SMS invitations, involving the Minister of Health to make press announcements on this study, media coverage, setting up an enquiries hotline and reaching out to foreign language speaking expatriates of a local multinational company to participate in this study. Data integration from various data sources, real time information sharing and a strong teamwork led to good outcomes adaptable to the progress of recruitment, compared to the more time-consuming and static traditional recruitment methods.

Immunogenicity of COVID-19 vaccines and levels of SARS-CoV-2 neutralising antibody in the Bruneian population: Protocol for a national longitudinal study.

INTRODUCTION: Neutralising antibodies (NAbs) have been shown to be correlative of immune protection against SARS-CoV-2. We report the protocol for a national longitudinal study to assess and compare the level of NAbs generated in response to COVID-19 vaccines in Brunei Darussalam in adults 2-6 weeks post primary series (BBIBP-CorV, AZD1222, or mRNA-1273 vaccines) and their subsequent follow-up after administration of a third (booster-1) dose (BBIBP-CorV, mRNA-1273, or BNT162b2). METHODS AND ANALYSIS: Participant data will be extracted and processed from the national electronic health record system (Bru-HIMS) and the national mobile health application (BruHealth) into a research data platform. Eligible adults who have received their primary or booster vaccine will be invited using a stratified random sampling strategy based on age, gender and vaccine type (baseline target population, n=3000; 2-6 weeks post last dose). Blood serum will be isolated, and NAb levels assessed using the cPass surrogate virus neutralisation test. Baseline participants will then be screened for eligibility for subsequent longitudinal analysis. Those who have received a third dose will be followed up at 1, 3, 6, 9 and up to 12 months. NAb levels will be evaluated across the participant population according to vaccine platform/booster type, time since the last dose and correlated with demographic data. The study period is from December 2021 to January 2023 and aims to evaluate how NAb levels wane following a third vaccine dose across different vaccine platforms and determine the impact and rate of breakthrough infections. ETHICS AND DISSEMINATION: This study has been approved by the Medical and Ethical Research Committee of Ministry of Health, Brunei Darussalam. Individual NAb test results will be shared with each participant by text message. The findings from this study will help policy-makers in Brunei develop future vaccination strategies and establish regulations across multiple agencies.

Immunological Responses and Biomarkers for Allergen-Specific Immunotherapy Against Inhaled Allergens.

Long-term efficacy that occurs with allergen immunotherapy of proven value is associated with decreases in IgE-dependent activation of mast cells and tissue eosinophilia. This suppression of type 2 immunity is accompanied by early induction of regulatory T cells, immune deviation in favor of TH1 responses, and induction of local and systemic IgG, IgG4, and IgA antibodies. These "protective" antibodies can inhibit allergen-IgE complex formation and consequent mast cell triggering and IgE-facilitated TH2-cell activation. Recent studies have highlighted the importance of innate responses mediated by type 2 dendritic cells and innate lymphoid cells in allergic inflammation. These cell types are under the regulation of cytokines such as thymic stromal lymphopoietin and IL-33 derived from the respiratory epithelium. Novel subsets of regulatory cells induced by immunotherapy include IL-35-producing regulatory T cells, regulatory B cells, a subset of T follicular regulatory cells, and IL-10-producing group 2 innate lymphoid cells. These mechanisms point to biomarkers that require testing for their ability to predict clinical response to immunotherapy and to inform novel approaches for better efficacy, safety, and long-term tolerance.