Iremonger, J. | Search bioRxiv

bioRxiv2025

Non-canonical inflammasome drives intrinsic anti-microbial responses in human Natural Killer (NK) cells.

Inflammasome pathways are critical for detecting pathogens and initiating inflammatory responses, yet how individual cell types configure these signalling platforms remains poorly understood. Here, we demonstrate that human Natural Killer cells possess distinct inflammasome machinery, lacking canonical components and innate sensors (NLRP3, NLRC4, TLR4) but harbour a functional non-canonical inflammasome (NCI). Using Salmonella enterica Typhimurium infection of primary human NK cells, we show that cytosolic bacterial access triggers caspase-4-dependent pyroptosis and IL-18 secretion, without canonical inflammasome activation or IL-1{beta} production. Strikingly, murine NK cells express inflammasome transcripts but lack functional caspase-11 protein and do not undergo pyroptosis upon infection, revealing species-specific post-transcriptional regulation. We further identify IL-12, but not IFN{gamma}, as a priming signal for NCI components in human NK cells, a functional distinction from macrophages and epithelial cells. Together, these findings reveal that human NK cells have evolved a specialised inflammasome with unique regulatory inputs, establishing these cells as autonomous sensors of intracellular Gram-negative infection.

immunology↗

bioRxiv2021

Divergent metabolism between Trypanosoma congolense and Trypanosoma brucei results in differential drug sensitivity

Animal African Trypanosomiasis (AAT) is a debilitating livestock disease prevalent across sub-Saharan Africa, a main cause of which is the protozoan parasite Trypanosoma congolense. In comparison to the well-studied T. brucei, there is a major paucity of knowledge regarding the biology of T. congolense. Here, we use a combination of omics technologies and novel genetic tools to characterise core metabolism in T. congolense mammalian-infective bloodstream-form parasites, and test whether metabolic differences compared to T. brucei impact upon drug sensitivity. Like T. brucei, glycolysis plays a major part in T. congolense energy metabolism. However, the rate of glucose uptake is significantly reduced in T. congolense, with cells remaining viable when cultured in concentrations as low as 2 mM. Instead of pyruvate, the primary glycolytic endpoints are succinate, malate and acetate. Comparative transcriptomics analysis showed higher levels of activity associated with the mitochondrial pyruvate dehydrogenase complex, acetate generation and the succinate shunt in T. congolense. However, based on omics analysis and chemical inhibition, there does not appear to be significant levels of oxidative phosphorylation. Stable-isotope labelling of glucose enabled the comparison of carbon usage between T. brucei and T. congolense, highlighting differences in nucleotide and fatty acid metabolism. To validate the metabolic similarities and differences, both species were treated with pharmacological inhibitors, confirming a lack of essential electron transport chain activity in T. congolense, but increased sensitivity to inhibition of mitochondrial pyruvate import. Strikingly, T. congolense exhibited significant resistance to inhibitors of fatty acid synthesis, including a 780-fold greater EC50 against the lipase and fatty acid synthase inhibitor Orlistat, compared to T. brucei. These data highlight that bloodstream form T. congolense diverges from T. brucei in key areas of metabolism, with several features that are intermediate between bloodstream- and insect-stage T. brucei. These results have implications for drug development, mechanisms of drug resistance and host-pathogen interactions.

microbiology↗