Targeting mitochondrial dysfunction can restore antiviral activity of NK cells in HIV/HCV coinfection

Introduction:

Hepatitis C virus (HCV) co-infection in HIV(+) persons remains a relevant health problem. Not only is it less likely that acute hepatitis C will heal spontaneously than in HIV(-) patients, but there is also a significantly faster progression of liver disease with faster development of liver fibrosis than in HCV monoinfected patients. Recently, we showed that ineffective IFN-g production of IL-2 stimulated HIV(+) NK cells may contribute to low spontaneous clearance rate and accelerated progression of HCV-associated liver disease in HIV(+) patients. However, the mechanisms underlying impaired IL-2 sensitivity of HIV(+) NK cells remained unclear.

Patients and Methods:

NK cell IFN-g production and NK cell-mediated inhibition of HCV replication were studied in HIV patients (n = 10) and compared to healthy controls (n = 10).

NK cell-mediated inhibition of HCV replication was analyzed using the HuH7A2HCVreplicon model. IFN-g production of NK cells was analysed by flow cytometry. Metabolic NK cell activity was studied using a Seahorse XF Analyzer. Gene expression was analysed by rt-PCR.

Results:

First, we investigated whether HIV(+) NK cells had a disorder in the IL-2 signalling pathway. However, neither the expression of the IL-2 receptors CD122 and CD25 nor the expression of central molecules in the signalling pathway itself showed a significant difference between HIV patients and healthy controls. An alternative plausible explanation would be a dysregulation of intracellular metabolic processes, since metabolic processes are essential for the development and function of NK cells. Indeed, we found HIV(+) NK cells to display an impaired reserve respiratory capacity suggesting metabolic/mitochondrial dysfunction. Accordingly, we found HIV infection to be associated with an altered expression of genes involved in regulating metabolic/mitochondrialy activity, including the genes encoding for phosphofructokinase-1 (PFK-1), AMP-activated protein kinase (AMPK) and pyruvat dehydrogenase (PDH). These alterations were found especially in HIV patients with a low CD4+ T cell count (< 400/µl). Moreover, we could show that the disturbed IFN-g production of NK cells in HIV patients with low CD4 count can be restored by stimulation with a mitochondrion-targeted antioxidant (MitoTEMPO). Accordingly, we found MitoTEMPO significantly increase anti-HCV activity of HIV(+) NK cells.

Conclusions:

Taken together, our data suggest that mitochondria may represent promising targets for novel therapeutic approaches to reconstitute NK cell functions in HIV/HCV coinfected patients.