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Contains fulltext : 291524.pdf (Publisher’s version ) (Open Access) For intradermal (ID) immunisation, novel needle-based delivery systems have been proposed as a better alternative to the Mantoux method. However, the penetration depth of needles in the human skin and its effect on immune cells residing in the different layers of the skin has not been analyzed. A novel and user-friendly silicon microinjection needle (Bella-mu(TM)) has been developed, which allows for a perpendicular injection due to its short needle length (1.4-1.8 mm) and ultrashort bevel. We aimed to characterize the performance of this microinjection needle in the context of the delivery of a particle-based outer membrane vesicle (OMV) vaccine using an ex vivo human skin explant model. We compared the needles of 1.4 and 1.8 mm with the conventional Mantoux method to investigate the depth of vaccine injection and the capacity of the skin antigen-presenting cell (APC) to phagocytose the OMVs. The 1.4 mm needle deposited the antigen closer to the epidermis than the 1.8 mm needle or the Mantoux method. Consequently, activation of epidermal Langerhans cells was significantly higher as determined by dendrite shortening. We found that five different subsets of dermal APCs are able to phagocytose the OMV vaccine, irrespective of the device or injection method. ID delivery using the 1.4 mm needle of a OMV-based vaccine allowed epidermal and dermal APC targeting, with superior activation of Langerhans cells. This study indicates that the use of a microinjection needle improves the delivery of vaccines in the human skin.

International audience; Background: Lymphopenia and the neutrophil/lymphocyte ratio may have prognostic value in COVID-19 severity.Objective: We investigated neutrophil subsets and functions in blood and bronchoalveolar lavage (BAL) of COVID-19 patients on the basis of patients’ clinical characteristics.Methods: We used a multiparametric cytometry profiling based to mature and immature neutrophil markers in 146 critical or severe COVID-19 patients.Results: The Discovery study (38 patients, first pandemic wave) showed that 80% of Intensive Care Unit (ICU) patients develop strong myelemia with CD10−CD64+ immature neutrophils (ImNs). Cellular profiling revealed three distinct neutrophil subsets expressing either the lectin‐like oxidized low‐density lipoprotein receptor‐1 (LOX‐1), the interleukin-3 receptor alpha (CD123), or programmed death-ligand 1 (PD-L1) overrepresented in ICU patients compared to non-ICU patients. The proportion of LOX-1- or CD123-expressing ImNs is positively correlated with clinical severity, cytokine storm (IL-1β, IL-6, IL-8, TNFα), acute respiratory distress syndrome (ARDS), and thrombosis. BALs of patients with ARDS were highly enriched in LOX-1-expressing ImN subsets and in antimicrobial neutrophil factors. A validation study (118 patients, second pandemic wave) confirmed and strengthened the association of the proportion of ImN subsets with disease severity, invasive ventilation, and death. Only high proportions of LOX-1-expressing ImNs remained strongly associated with a high risk of severe thrombosis independently of the plasma antimicrobial neutrophil factors, suggesting an independent association of ImN markers with their functions.Conclusion: LOX-1-expressing ImNs may help identifying COVID-19 patients at high risk of severity and thrombosis complications.

International audience; Rationale. The importance of the adaptative T cell response in the control and resolution of viral infection has been well-established. However, the nature of T cell-mediated viral control mechanisms in life-threatening stages of COVID-19 has yet to be determined.Objective. The aim of the present study was to determine the function and phenotype of T cell populations associated with survival or death of COVID-19 patients under intensive care as a result of phenotypic and functional profiling by mass cytometry.Findings. Increased frequencies of circulating, polyfunctional, CD4+CXCR5+HLA-DR+ stem cell memory T cells (TSCM) and decreased proportions of Granzyme-B and Perforin-expressing effector memory T cells (TEM) were detected in recovered and deceased patients, respectively. The higher abundance of polyfunctional CD8+PD-L1+CXCR3+ T effector cells, CXCR5+HLA-DR+ TSCM, as well as anti-nucleocapsid (NC) cytokine-producing T cells permitted to differentiate between recovered and deceased patients. The results from a principal component analysis showed an imbalance in the T cell compartment allowed for the separation of recovered and deceased patients. The paucity of circulating CD8+PD-L1+CXCR3+ Teff-cells and NC-specific CD8+ T-cells accurately forecasts fatal disease outcome.Conclusion. This study provides insight into the nature of the T cell populations involved in the control of COVID-19 and therefor might impact T cell-based vaccine designs for this infectious disease.

International audience; Vaccination is one of the major public health advances in modern medicine. But in order to improve the effectiveness of existing vaccines and develop new ones, we need to know more about the mechanisms of action that lead to protective immunity and the strategies that lead to sustainable defence. Cutaneous vaccination is a promising procedure because of the richness of innate cells in the skin and their role in the quality, intensity and persistence of adaptive responses. A Systems Biology approach is used to probe immunological dynamic post-vaccination and to simultaneously analyse a large number of variables: antibody and cytokines levels, gene expression or even cellular outcomes. Immunological data have been collected from an influenza vaccination clinical trial and, thanks to this approach, provided insight into the impact of the immunization route on the quality of immune responses. An innate gene signature is also identified in order to predict the intensity of immune responses.; Vaccination is one of the major public health advances in modern medicine. But in order to improve the effectiveness of existing vaccines and develop new ones, we need to know more about the mechanisms of action that lead to protective immunity and the strategies that lead to sustainable defence. Cutaneous vaccination is a promising procedure because of the richness of innate cells in the skin and their role in the quality, intensity and persistence of adaptive responses. A Systems Biology approach is used to probe immunological dynamic post-vaccination and to simultaneously analyse a large number of variables: antibody and cytokines levels, gene expression or even cellular outcomes. Immunological data have been collected from an influenza vaccination clinical trial and, thanks to this approach, provided insight into the impact of the immunization route on the quality of immune responses. An innate gene signature is also identified in order to predict the intensity of immune responses.