Ex vivo analysis of cytokine and metabolic profiles in placental malaria reveals compartment-dependent T-cell variations.

γδ T cells play a key role in modulating immune responses to pregnancy-associated malaria and can enhance vaccine efficacy through their activation and cytotoxic functions. However, the mechanisms guiding γδT cell differentiation in placental malaria (PM) remain poorly understood. We examined ex vivo associations between cytokines, metabolic profiles and γδ T-cell differentiation in women with PM. A case-control study including 50 women at delivery (21 PM+, 29 PM-) was carried out. Peripheral, placental intervillous space, and cord blood mononuclear cells were isolated, and multiparametric flow cytometry was performed to characterize γδT-cells and memory phenotypes, its subsets (Vδ1+, Vδ2+, Vδ3+), and the expression of exhaustion (TIM-3, PD1) and activation (HLA-DR) markers. Ex vivo plasma levels of IL-8, IL-33, and IL-35 were quantified by Luminex assay or ELISA. Immunometabolic profiles were assessed in a subset of 15 samples from uninfected women following cell stimulation with phytohemagglutinin (PHA) by SCENITH assay. In general, the frequency of γδ T cells and their subsets varied depending on the different blood compartments, with naïve and central memory (CM) phenotypes observed mainly in CBMC, while effector memory (EM) and terminally differentiated effector memory (TEMRA) phenotypes were found mainly in PBMC and IVBMC. Ex vivo analyses showed that γδ T cell-modulating cytokine IL-8 were associated, in a compartment-dependent manner, with down-regulation of immunoregulatory markers TIM-3 and PD-1. Interestingly, IL-8 and IL-33 were associated with increased frequency of the TEMRA cell phenotype in peripheral blood, consistent with enhanced differentiation of naïve γδT cells during PM. Metabolic profiling of the different cell types further established an enhanced mitochondrial metabolic activity in predominantly terminally differentiated γδ T cells in PBMC, compared to the mainly glycolytic activities of non-terminally differentiated cells in CBMC and IVBMC. Placental malaria is associated with a compartment-specific memory γδ T cell differentiation, with cytokines and metabolic reprogramming regulating exhaustion. These findings reveal key regulatory processes that determine the function of γδ T cells during placental malaria, which constitute potential targets for new therapeutic intervention against PM.