Type I interferon subtypes differentially activate the anti-leukaemic function of natural killer cells

Mechanism of interferon alpha therapy for chronic hepatitis B and potential approaches to improve its therapeutic efficacy

Hepatitis B virus (HBV) chronically infects 296 million people worldwide and causes more than 820,000 deaths annually due to cirrhosis and hepatocellular carcinoma. Current standard-of-care medications for chronic hepatitis B (CHB) include nucleos(t)ide analogue (NA) viral DNA polymerase inhibitors and pegylated interferon alpha (PEG-IFN-α). NAs can efficiently suppress viral replication and improve liver pathology, but not eliminate or inactivate HBV covalently closed circular DNA (cccDNA). CCC DNA is the most stable HBV replication intermediate that exists as a minichromosome in the nucleus of infected hepatocyte to transcribe viral RNA and support viral protein translation and genome replication. Consequentially, a finite duration of NA therapy rarely achieves a sustained off-treatment suppression of viral replication and life-long NA treatment is most likely required. On the contrary, PEG-IFN-α has the benefit of finite treatment duration and achieves HBsAg seroclearance, the indication of durable immune control of HBV replication and functional cure of CHB, in approximately 5% of treated patients. However, the low antiviral efficacy and poor tolerability limit its use. Understanding how IFN-α suppresses HBV replication and regulates antiviral immune responses will help rational optimization of IFN therapy and development of novel immune modulators to improve the rate of functional cure. This review article highlights mechanistic insight on IFN control of HBV infection and recent progress in development of novel IFN regimens, small molecule IFN mimetics and combination therapy of PEG-IFN-α with new direct-acting antivirals and therapeutic vaccines to facilitate the functional cure of CHB.

Sex-dependent differences in type I IFN-induced natural killer cell activation

Natural killer (NK) cells are important antiviral effector cells and also involved in tumor clearance. NK cells express IFNAR, rendering them responsive to Type I IFNs. To evaluate Type I IFN-mediated modulation of NK cell functions, individual Type I IFNs subtypes were assessed for their ability to activate NK cells. Different Type I IFN subtypes displayed a broad range in the capacity to induce and modulate NK cell activation and degranulation, measured by CD69 and CD107a expression in response to leukemia cell line K562. When including biological sex as a variable in the analysis, transwell co-cultures of NK cells with either male- or female-derived PBMCs or pDCs stimulated with the TLR7/8 agonist CL097 showed that NK cells were more activated by CL097-stimulated cells derived from females. These sex-specific differences were linked to higher CL097-induced IFNα production by pDCs derived from females, indicating an extrinsic sex-specific effect of Type I IFNs on NK cell function. Interestingly, in addition to the extrinsic effect, we also observed NK cell-intrinsic sex differences, as female NK cells displayed higher activation levels after IFNα-stimulation and after co-culture with CL097-stimulated pDCs, suggesting higher activation of IFNα-signaling transduction in female NK cells. Taken together, the results from these studies identify both extrinsic and intrinsic sex-specific differences in Type I IFN-dependent NK cell functions, contributing to a better understanding of sex-specific differences in innate immunity.

Targeting cGAS/STING signaling-mediated myeloid immune cell dysfunction in TIME

Myeloid immune cells (MICs) are potent innate immune cells serving as first responders to invading pathogens and internal changes to cellular homeostasis. Cancer is a stage of altered cellular homeostasis that can originate in response to different pathogens, chemical carcinogens, and internal genetic/epigenetic changes. MICs express several pattern recognition receptors (PRRs) on their membranes, cytosol, and organelles, recognizing systemic, tissue, and organ-specific altered homeostasis. cGAS/STING signaling is a cytosolic PRR system for identifying cytosolic double-stranded DNA (dsDNA) in a sequence-independent but size-dependent manner. The longer the cytosolic dsDNA size, the stronger the cGAS/STING signaling activation with increased type 1 interferon (IFN) and NF-κB-dependent cytokines and chemokines' generation. The present article discusses tumor-supportive changes occurring in the tumor microenvironment (TME) or tumor immune microenvironment (TIME) MICs, specifically emphasizing cGAS/STING signaling-dependent alteration. The article further discusses utilizing MIC-specific cGAS/STING signaling modulation as critical tumor immunotherapy to alter TIME.

IFN-β activates cytotoxic function of human natural killer cells toward IL-27 and poly(I:C) stimulated PC3 and DU145 cells

Natural killer (NK) cell phenotype and function are altered in patients with prostate cancer, and increased NK cell activity is associated with a better prognosis in patients with disease. For patients with advanced stage prostate cancer, immunotherapies are a promising approach when standard treatment options have been exhausted. With the rapid emergence of NK cell-based therapies, it is important to understand the mechanisms by which NK cells can be triggered to kill cancer cells that have developed immune-evasive strategies. Altering the cytokine profiles of advanced prostate cancer cells may be an area to explore when considering ways in which NK cell activation can be modulated. We have previously demonstrated that combining the cytokine, IL-27, with TLR3 agonist, poly(I:C), changes cytokine secretion in the advanced prostate cancer models, PC3 and DU145 cells. Herein, we extend our previous work to study the effect of primary human NK cells on prostate cancer cell death in an in vitro co-culture model. Stimulating PC3 and DU145 cells with IL-27 and poly(I:C) induced IFN-β secretion, which was required for activation of primary human NK cells to kill these stimulated prostate cancer cells. PC3 cells were more sensitized to NK cell-mediated killing when compared to DU145 cells, which was attributed to differential levels of IFN-β produced in response to stimulation with IL-27 and poly(I:C). IFN-β increased granzyme B secretion and membrane-bound TRAIL expression by co-cultured NK cells. We further demonstrated that these NK cells killed PC3 cells in a partially TRAIL-dependent manner. This work provides mechanistic insight into how the cytotoxic function of NK cells can be improved to target cancer cells.