Biology subjects

O'Hehir, R. E.

Publications and source records attributed to O'Hehir, R. E..

4 recordsLinked to original sources

bioRxiv2023

Third dose COVID-19 mRNA vaccine enhances IgG4 isotype switching and recognition of Omicron subvariants by memory B cells after with mRNA but not adenovirus priming

BackgroundBooster vaccinations are recommended to improve protection against severe disease from SARS-CoV-2 infection. With primary vaccinations involving various adenoviral vector and mRNA-based formulations, it remains unclear if these differentially affect the immune response to booster doses. We here examined the effects of homologous (mRNA/mRNA) and heterologous (adenoviral vector/mRNA) vaccination on antibody and memory B cell (Bmem) responses against ancestral and Omicron subvariants. MethodsHealthy adults who received primary BNT162b2 (mRNA) (n=18) or ChAdOx1 (vector) (n=25) vaccination were sampled 1-month and 6-months after their 2nd and 3rd dose (homologous or heterologous) vaccination. Recombinant spike receptor-binding domain (RBD) proteins from ancestral, Omicron BA.2 and BA.5 variants were produced for ELISA-based serology, and tetramerized for immunophenotyping of RBD-specific Bmem. ResultsDose 3 boosters significantly increased ancestral RBD-specific plasma IgG and Bmem in both cohorts. Up to 80% of ancestral RBD-specific Bmem expressed IgG1+. IgG4+ Bmem were detectable after primary mRNA vaccination, and expanded significantly to 5-20% after dose 3, whereas heterologous boosting did not elicit IgG4+ Bmem. Recognition of Omicron BA.2 and BA.5 by ancestral RBD-specific plasma IgG increased from 20% to 60% after the 3rd dose in both cohorts. Reactivity of ancestral RBD-specific Bmem to Omicron BA.2 and BA.5 increased following a homologous booster from 40% to 60%, but not after a heterologous booster. ConclusionA 3rd mRNA dose generates similarly robust serological and Bmem responses in homologous and heterologous vaccination groups. The expansion of IgG4+ Bmem after mRNA priming might result from the unique vaccine formulation or dosing schedule affecting the Bmem response duration and antibody maturation.

immunology↗

bioRxiv2023

Accurate determination of house dust mite sensitization in asthma and allergic rhinitis through cytometric detection of Der p 1 and Der p 2 binding on Basophils (CytoBas)

BackgroundHouse dust mite (HDM) is the commonest allergen trigger globally for allergic rhinitis and atopic asthma. To expedite accurate confirmation of allergen sensitization, we designed fluorescent allergen tetramers to directly stain specific IgE on basophils to detect allergen sensitization using the flow cytometric CytoBas assay. MethodsRecombinant proteins of major HDM allergens (component), Der f 1, Der p 1 and Der p 2 were biotinylated and conjugated with fluorochrome streptavidins as tetramers. Blood samples from 64 HDM-allergic patients and 26 non-HDM-sensitized controls were incubated with allergen tetramers for evaluation of basophil binding (CytoBas) and activation (BAT) with flow cytometry. ResultsThe tetramers effectively bound and activated basophils from allergic patients but not non-sensitized controls. CytoBas with Der p 1 as a single allergen had comparable sensitivity and specificity (92% and 100%) to BAT (91% and 100%), similarly for CytoBas with a single Der p 2 (95% and 96%) to BAT (95% and 87%) in detecting allergen sensitization. A positive staining for Der p 1 and/or Der p 2 was 100% sensitive and 96% specific for HDM allergy. ConclusionsCytoBas has diagnostic accuracy for group 1 and group 2 HDM allergens that is comparable to a BAT assay, but with additional advantages of multiple allergen components in a single tube and no requirement for in vitro basophil activation. These findings endorse a single, multiplex CytoBas assay for accurate and component-resolved diagnosis of aeroallergen sensitization in patients with allergic asthma and/or rhinitis. CAPSULE SUMMARYA single flow cytometry stain of basophils (CytoBas) with both Der p 1 and Der p 2 provides >95% specificity and sensitivity for detection of functional HDM allergen sensitization. HighlightsO_LIFluorescent tetramers of recombinant Der f 1, Der p 1 and Der p 2 can be used to detect functional IgE sensitization to house dust mite (HDM) by flowcytometric detection on basophils (CytoBas). C_LIO_LIA single CytoBas assay with inclusion of both Der p 1 and Der p 2 can detect HDM sensitization with >95% sensitivity and specificity. C_LI

immunology↗

bioRxiv2023

COVID-19 adenoviral vector vaccination elicits a robust memory B cell response with the capacity to recognize Omicron BA.2 and BA.5 variants

Following the COVID-19 pandemic caused by SARS-CoV-2, novel vaccines have successfully reduced severe disease and death. Despite eliciting lower antibody responses, adenoviral vector vaccines are nearly as effective as mRNA vaccines. Therefore, protection against severe disease may be mediated by immune memory cells. We here evaluated plasma antibody and memory B cells (Bmem) targeting the Spike receptor binding domain (RBD) elicited by the adenoviral vector vaccine ChAdOx1 (AstraZeneca), their capacity to bind Omicron subvariants, and compared this to the response elicited by the mRNA vaccine BNT162b2 (Pfizer-BioNTech). Whole blood was sampled from 31 healthy adults pre-vaccination, and four weeks after dose one and dose two of ChAdOx1. Neutralizing antibodies (NAb) against SARS-CoV-2 were quantified at each timepoint. Recombinant RBDs of the Wuhan-Hu-1 (WH1), Delta, BA.2, and BA.5 variants were produced for ELISA-based quantification of plasma IgG and incorporated separately into fluorescent tetramers for flow cytometric identification of RBD-specific Bmem. NAb and RBD-specific IgG levels were over eight times lower following ChAdOx1 vaccination than BNT162b2. In ChAdOx1-vaccinated individuals, median plasma IgG recognition of BA.2 and BA.5 as a proportion of WH1-specific IgG was 26% and 17%, respectively. All donors generated resting RBD-specific Bmem, which were boosted after the second dose of ChAdOx1, and were similar in number to those produced by BNT162b2. The second dose of ChAdOx1 boosted Bmem that recognized VoC, and 37% and 39% of WH1-specific Bmem recognized BA.2 and BA.5, respectively. These data uncover mechanisms by which ChAdOx1 elicits immune memory to confer effective protection against severe COVID-19.

immunology↗

bioRxiv2022

Double-dose mRNA vaccination to SARS-CoV-2 progressively increases recognition of variants-of-concern by Spike RBD-specific memory B cells

BackgroundSARS-CoV-2 vaccination with BNT162b2 (Pfizer BioNTech) has been shown to be 95% effective.1 Double-dose vaccination generates high levels of spike-specific antibodies, memory B cells (Bmem) and T cells. However, variants of concern (VoC) with mutations in the spike Receptor Binding Domain (RBD) can evade antibody responses. Booster vaccinations improve antibody recognition of VoC, but it is unclear if this is due to higher total antibodies or their capacity to bind VoC. We here addressed the capacity of surface Ig on single Wuhan-specific Bmem after first and second dose BNT162b2 vaccination to recognize variant RBD. MethodsSamples were collected from 30 healthy COVID-19 naive individuals pre-BNT162b2 vaccination, 3 weeks post-dose 1 and 4-weeks post-dose 2. Plasma antibodies and Bmem were evaluated using recombinant RBD proteins of the Wuhan, Gamma and Delta strains. ResultsAll individuals generated a robust antibody response to BNT162b2 vaccination with all participants producing neutralizing antibodies following dose 2. IgM+ and IgG+ RBD-specific Bmem were generated after one vaccine dose, and those expressing IgG1 increased in absolute number after dose 2. The majority of RBD-specific Bmem bound the Gamma and/or Delta variants, and this proportion significantly increased after the second dose. ConclusionThe second dose of BNT162b2 increases the number of circulating Ig-class switched RBD-specific Bmem. Importantly, the second dose of vaccination is required for a high frequency of RBD-specific Bmem to recognize Gamma and Delta variants. This suggests that dose 2 not only increases the number of RBD-specific Bmem but also the affinity of the Bmem to overcome the point mutations in VoC.

immunology↗