Advanced In vitro Human Immune Profiling of GMMA-based vaccines

Generalized Modules for Membrane Antigens (GMMA) are outer membrane vesicles derived from engineered Gram-negative bacteria. GMMA, resembling bacteria outer membrane surface, provide a flexible platform for the vaccine development and GMMA-based vaccines have been demonstrated to induce a functional antibody response with a low reactogenicity profile. Recently we published data showing that GMMA vaccine candidates activate Antigen Presenting Cells by exhibiting a self-adjuvanticity potential. However, we still have a lack of information about how GMMA affect the various immune cell subsets in terms of functionality /differentiation and/or maturation. Furthermore, remain unclear whether additional cell subsets present at the injection site could also be activated by GMMA. To deeply characterize the GMMA Mode of Action (MoA) on different cell populations we use GMMA- based vaccine candidates Shigella to stimulate blood, isolated monocytes, in vitro differentiated Monocyte- derived Dendritic Cell (MoDC) and human Skeletal Muscle Cell (hSkMC). Thanks to a multicolor flow cytometry-based analysis combined to cytokine detection assay, we demonstrated that monocytes are activated upon stimulation with GMMA Shigella, producing pro-inflammatory cytokines and chemokines such as IL-6, IL-8, MIP-1α, IP-10. Moreover, MoDC in vitro model allowed us to show that GMMA induce activation and maturation of Dendritic Cells by inducing cytokines production and upregulation of markers such as CD40, CD83, CD86. Finally, we showed that GMMA induced the production of myokines on hSkMC (IL-6, IL-8, IP-10) after in vitro stimulation demonstrating that GMMA also influence the activation of muscle cells at the injection site. Further investigation will be done with the aim to dissect the GMMA MoA on key immune cells and to understand the impact of GMMA-mediated APC activation on adaptive immune response developing an in vitro model of T cell polarization.