IL-15 re-programming compensates for NK cell mitochondrial dysfunction in HIV-1 infection

Dynamic regulation of cellular metabolism is important for maintaining homeostasis and can directly influence immune cell function and differentiation including Natural Killer (NK) cell responses. Persistent HIV-1 infection leads to a state of chronic activation, subset redistribution and progressive NK cell dysregulation. In this study we examined the metabolic processes that characterise NK cell subsets in HIV-1 infection, including adaptive NK cell subpopulations expressing the activating receptor NKG2C, which expand during chronic infection. These adaptive NK cells exhibit an enhanced metabolic profile in human cytomegalovirus (HCMV) infected HIV-1 seronegative individuals. However, the bioenergetic advantage of adaptive CD57+NKG2C+ NK cells is diminished during chronic HIV-1 infection, where NK cells uniformly display reduced oxidative phosphorylation (OXPHOS) and limited fuel flexibility upon CD16 stimulation. Defective OXPHOS was accompanied by increased mitochondrial depolarisation and structural alterations indicative of mitochondrial dysfunction, suggesting that mitochondrial defects are restricting the metabolic plasticity of NK cell subsets in HIV-1 infection. The metabolic requirement for receptor stimulation was alleviated upon IL-15 pre-treatment enhancing mammalian target of rapamycin complex1 (mTORC1) activity and NK cell functionality in HIV-1 infection, representing an effective strategy for pharmacologically boosting NK cell responses.