Immunometabolite L-2-Hydroxyglutarate in Natural Killer Cell Antiviral Immunity

Natural Killer (NK) cells are a major component of host immunity against viral infections rapidly responding toinfected cells by secreting cytokines and lytic granules. NK cells are particularly important for controllinginfections by herpesviruses such as cytomegalovirus which can cause significant clinical consequences inimmunocompromised patients and neonates. Using a well-established mouse cytomegalovirus (MCMV)infection model our lab and others have demonstrated that NK cells undergo dynamic metabolic and epigeneticshifts during antiviral responses to fuel their activation and effector functions. However the mechanisms by whichNK cells coordinate these metabolic and epigenetic changes are not well understood.Growing evidence indicates that central metabolites play important roles in immune cell activation by acting notonly as energy sources but also as substrates for growth signaling pathways epigenetic regulation and effectordifferentiation. L-2-hydroxyglutarate (L-2HG) is an immunometabolite that has been shown to play a role incoordinating metabolic and epigenetic shifts in activated CD8+ T cells dendritic cells and macrophages. Duringactivation L-2HG accumulates and acts as a potent competitive inhibitor of KG-dependent enzymes includinghistone lysine demethylases and hypoxia inducible factor prolyl hydroxylases altering the epigenetic andmetabolic state of these cells. While L-2HG is clearly important for immune cell function the role of L-2HG in NKcells is unknown. My preliminary data indicates that NK cells limit levels of L-2HG during infection by increasingthe expression of L-2HG dehydrogenase. Excess accumulation of L-2HG resulted in impaired NK cell antiviralfunctions. Given the impact of L-2HG on epigenetics and metabolism I hypothesize that L-2HG accumulationis detrimental to the NK cell antiviral response by disrupting highly coordinated changes in histone methylationand by skewing the balance between glycolytic and oxidative metabolism. Using the novel mouse models of NK-specific L-2HG accumulation and depletion that I generated in collaboration with the lab of Dr. Andrew IntlekoferI will pursue the following aims. In Aim 1 I will use in vivo and in vitro epigenetic assays to assess the impact ofL-2HG accumulation on activating H3K4me3 and repressive H3K27me3 levels during NK cell responses toMCMV. In Aim 2 I will use metabolic assays to elucidate the HIF-1-dependent and -independent metabolicperturbations by L-2HG in NK cells during MCMV infection. This study will define a novel metabolic-epigeneticaxis in NK cells that will inform the development of improved NK cell-based antiviral therapies.