HIV/HBV co-infection remodels the immune landscape and Natural Killer cell functional responses
Background: Hepatitis B (HBV) and human immunodeficiency virus (HIV) co-infection is a common occurrence globally, with significant morbidity and mortality. Both viruses lead to dysregulated immune responses including changes in natural killer (NK) cells, a key component of antiviral defense and a promising target for HBV cure strategies. In this study we used high-throughput single cell analysis to explore the immune cell landscape in people with HBV mono-infection and HIV/HBV co-infection, on antiviral therapy, with emphasis on identifying the distinctive characteristics of NK cell subsets. Results:  Our data show striking differences in the transcriptional programs of NK cells.  HIV/HBV co-infection was characterized by an overrepresentation of adaptive, KLRC2 expressing NK cells, including a higher abundance of a chemokine enriched (CCL3/CCL4) adaptive cluster. The NK cell remodeling in HIV/HBV co-infection was reflected in enriched activation pathways shared with T cells, including CD3? phosphorylation and ZAP-70 translocation that can mediate stronger ADCC responses and a bias towards chemokine/cytokine signaling. By contrast HBV mono-infection imposed a stronger cytotoxic profile on NK cells and a more prominent signature of exhaustion with higher circulating levels of HBsAg. Mirroring the transcriptomic analysis, phenotypic alterations in the NK cell pool in co-infection were consistent with increased 'adaptiveness' and better capacity for ADCC compared to HBV mono-infection.  Overall an adaptive NK cell signature correlated inversely with circulating levels of HBsAg and HBV-RNA in our cohort. Conlcusions: This study provides new insights into the differential transcriptional signature and functional profile of NK cells in HBV and HIV/HBV co-infection, highlighting new pathways that can be manipulated to tailor NK cell-focused approaches to advance cure strategies in the different population groups. Overall design: Peripheral blood mononuclear cells were harvested from 3 control subjects along with 5 HIV-HBV co-onfected and 5 HBV monoinfected subjects. Those with >95% viability were used for this study. Library construction was performed using the 10x next GEM Chips Chromium single cell library 5' construction kit. cDNA libraries were prepared as per 10x Genomics Single Cell 5' reagent kit user guide with calculations based on the amount of input cDNA. Purified libraries were analysed by Novogene.