Galectin-9 and Interferon-Gamma Are Released by Natural Killer Cells upon Activation with Interferon-Alpha and Orchestrate the Suppression of Hepatitis C Virus Infection

Abstract

Natural killer (NK) cells mount an immune response against hepatitis C virus (HCV) infection and can be activated by several cytokines, including interleukin-2 (IL-2), IL-15, and interferon-alpha (IFN-α). By exploiting the Huh7.5 hepatoma cell line infected with the HCV JFH1 genome, we provide novel insights into the antiviral effector functions of human primary NK cells after cytokine stimulation. NK cells activated with IFN-α (IFNα-NKs) had enhanced contact-dependent and -independent responses as compared with NK cells activated with IL-2/IL-15 (IL2/IL15-NKs) and could inhibit HCV replication both in vitro and in vivo. Importantly, IFN-α, but not IL-2/IL-15, protected NK cells from the functional inhibition exerted by HCV. By performing flow cytometry, multiplex cytokine profiling, and mass-spectrometry-based proteomics, we discovered that IFNα-NKs secreted high levels of galectin-9 and interferon-gamma (IFN-γ), and by conducting neutralization assays, we confirmed the major role of these molecules in HCV suppression. We speculated that galectin-9 might act extracellularly to inhibit HCV binding to host cells and downstream infection. In silico approaches predicted the binding of HCV envelope protein E2 to galectin-9 carbohydrate-recognition domains, and co-immunoprecipitation assays confirmed physical interaction. IFN-γ, on the other hand, triggered the intracellular expressions of two antiviral gate-keepers in target cells, namely, myxovirus-1 (MX1) and interferon-induced protein with tetratricopeptide repeats 1 (IFIT1). Collectively, our data add more complexity to the antiviral innate response mediated by NK cells and highlight galectin-9 as a key molecule that might be exploited to neutralize productive viral infection.

Galectokines: The Promiscuous Relationship between Galectins and Cytokines

“…However, since IFN-α also induced IFN-γ, the observation could be partly secondary to IFN-γ. In line with this, IL-2/IL-15 treatment of NK cells did not induce the secretion of IFN-γ and galectin-9 [ 118 ].…”

“…In our study, the anti-inflammatory IL-10 also induced galectin-9 expression, albeit to a lesser extent than IFN-γ, while other cytokines (IL-1, TNF-α, VEGF) had no or a slightly inhibitory effect [ 13 ]. Recently, Carreca and coworkers reported that secretion of galectin-9 by NK cells was increased upon treatment with IFN-α [ 118 ]. However, since IFN-α also induced IFN-γ, the observation could be partly secondary to IFN-γ.…”

Unveiling the potential pleiotropic effects of metformin in treating COVID-19: a comprehensive review

“…The gut microbiota can influence the host’s immune response to viral infections by regulating the production of antiviral cytokines and modulating the activity of immune cells. For example, gut bacteria can produce SCFAs, which have been shown to enhance the antiviral immune response by increasing the production of IFN-γ and natural killer (NK) cells ( Carreca et al, 2022 ; Govers et al, 2022 ). Moreover, the gut microbiota can influence the development and function of Tregs, which play a crucial role in maintaining immune homeostasis and preventing excessive inflammation ( Smigiel et al, 2014 ).…”

Impact of T Lymphocytes Isolated from Liver Perfusate of Deceased Brain Donors on Kidney Transplantation: Preliminary Evidence and Future Directions

“…T-Li, natural killer (NK), and NK-T cellular concentrations and phenotypes were retrospectively analyzed in a consecutive series of liver perfusates (LPs) after hepatectomy of whole livers on the bench recovered from deceased brain donors (DBDs). Leucocytes were isolated from the perfusion fluid of liver explants, as previously described [13][14][15]. Briefly, during the organ procurement, the aorta was clamped, and the abdominal cavity was flushed with up to 5 L of preservation solution to exsanguinate the deceased donor.…”