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    Poster Networking

    Immunothrombosis

    Poster Networking Session

    PB0772 - Platelet-B cell interactions modulate the antibody response to adenoviral and mRNA vaccines against SARS-CoV-2

    Monday, June 26, 2023
    18:30 – 19:30 ET
    Room: Exhibition
    Background: Genetic-based COVID-19 vaccines have proved highly effective in reducing the risk of hospitalization and death. As they were first distributed on a large-scale population, adenoviral-based vaccines were linked to a very rare thrombosis with thrombocytopenia syndrome and the interplay between platelets and vaccinations increasingly gained attention.

    Aims: To study the crosstalk between platelets and the vaccine-induced immune response.

    Methods: We prospectively enrolled young healthy volunteers who received the mRNA-based vaccine, BNT162b2 (n=15; mean age  standard deviation (SD): 28.71.5 years) or the adenovirus-based vaccine, AZD1222 (n=25; 28.65.7 years) and studied their short-term platelet and immune response before and after vaccine injections, by multiparametric flow cytometry. In a separate cohort of 2065 healthcare workers (45.9±13.3 years), we retrospectively analysed the effect of aspirin (n=56) on the antibody response 1 and 5 months after a two-dose regimen of the BNT162b2 vaccination.

    Results: Here we show that a faster antibody response to either vaccine is associated to the formation of platelet aggregates with marginal zone-like B-cells, a subtype geared to respond rapidly to blood-borne pathogens and to bridge the temporal gap between innate and adaptive immunity. However, while the mRNA-based vaccine is associated with a more gradual and tolerogenic response that fosters the crosstalk between platelets and adaptive immunity, the adenovirus-based vaccine, the less immunogenic of the two, evokes an antiviral-like response during which platelets are cleared and less likely to cooperate with B-cells. In support of a role of platelets in supporting adaptive immunity, we also present preliminary evidence that subjects taking aspirin (n=56) display lower antibody levels after BNT162b2 vaccination compared to matched individuals.

    Conclusion(s): Platelets are an integral component of the innate signalling pathways that promote the B-cell response after immunization. Future studies on the platelet-immune crosstalk post-immunization will improve safety, efficacy, and strategic administration of next-generation vaccines.