Acetyl-CoA generation by Acly distinctly regulates CD4 T cell programming during Plasmodium infection

Introduction/Rationale: Malaria is a disease triggered by Plasmodium parasite infection, causing over 200 million cases and ~600,000 deaths each year. CD4 T cells, specifically Th1 and Tfh, are critical for parasite control and clearance. We found that CD4 T cell subsets responding to malaria exhibit distinct energetic demands. These energetic dependencies are supported by metabolic pathways that may differentially represent available metabolites, including Acetyl-CoA (Ac-CoA) that sits at a central node between cytosolic and mitochondrial metabolism. Based on the distinct energetic demands of CD4 T cell subsets, different levels of Ac-CoA may be present in the cytosol regulating acetylation and differentiation. Our scRNA-seq data shows Acly, which converts cytosolic citrate into Ac-CoA, is expressed in malaria-specific CD4 T cells. While the contribution of Acly in CD4 T cells is not well defined, published data suggests a role in Th1 cells in vitro. Therefore, we hypothesize that Acly is required for optimal Th1 cell programming during infection.

Methods: To address the role of Acly in vivo, we engineered a conditional genetic system to excise Acly from mature, peripheral Plasmodium-specific CD4 T cells. We employed systems of co-adoptive transfer and flow cytometry to assess the phenotype of the transferred cells. We used SCENITH to measure energy profiles and Mitotracker for changes in mitochondrial activity and mass.

Results: Loss of Acly negatively impacts the Th1 population but sustains the Tfh population. Acly-KO Th1 cells show changes in mitochondrial function and energetic profiles, with no observed changes in Tfh cells. Functionally, Acly-KO T cells produce less IFN-gamma.

Conclusion: These data establish a role of Acly in CD4 T cell programming during malaria, potentially supporting the Th1 program. Our data provide an opportunity to unravel metabolic programs and regulatory nodes that are critical for Th1 development but dispensable for Tfh differentiation.