Riteau, N. | bioRxiv Science

bioRxiv2026

Hijacking of inflammasome responses by the complement system during Pseudomonas aeruginosa-Aspergillus fumigatus sur-infection

Patients with cystic fibrosis (pwCF) are highly susceptible to chronic pulmonary infections due to mutations in the CFTR gene. From early childhood, pwCF experience repeated lung infections and often develop chronic bacterial and/or fungal colonization. Among the most clinically relevant pathogens, Pseudomonas aeruginosa and Aspergillus fumigatus frequently co-infect and are associated with worse outcomes, including excessive IL-1{beta}-driven inflammation and accelerated lung function decline. Here we investigated the mechanisms underlying inflammasome overactivation during super-infection. We found that inflammasome hyperactivation occurred across macrophage populations, was independent of exogenous priming, and required live co-infection with both pathogens. P. aeruginosa and A. fumigatus cooperatively activated the NLRP3 inflammasome, and this response required both caspase-1 and caspase-8. Unexpectedly, gasdermin D was dispensable for IL-1{beta} release. Bacterial flagellin, type IV pili and the type III secretion system, as well as the fungal polysaccharide galactosaminogalactan (GAG), were each required for overactivation. Mechanistically, P. aeruginosa activated the MyD88-TLR pathway, enhancing macrophage responses and promoting ITGAM (CD11b) expression. Under fungal super-infection, macrophages secreted complement component C3, which may bound fungal surface and engaged the complement receptor C3R (CD11b/CD18). Downstream SYK and ERK signaling amplified inflammasome activation and IL-1{beta} release. Single-cell transcriptomic analysis of pwCF broncho-alveolar lavage and lung samples supported coordinated upregulation of complement and inflammasome pathways during bacterial-fungal infection. Together, these findings identify a complement-inflammasome signaling axis that drives pathological inflammation during bacterial-fungal co-infection in airways of pwCF and may represent a therapeutic target.

immunology↗

bioRxiv2024

Lymphopenia drives T cell exhaustion in immunodeficient STING gain-of-function mice

STING gain-of-function (GOF) mutations are associated with the severe autoinflammatory disease designated STING Associated Vasculopathy with onset in Infancy (SAVI). Mice with the STING GOF V154M mutation develop profound T cell lymphopenia, partly due to a blockage of T cell development in the thymus. To better characterize the mechanisms of peripheral T cell dysfunctions, we conducted a transcriptomic and phenotypic analysis on sorted splenic CD4+ and CD8+ mature T cells from STING GOF V154M mice. We identify a T cell exhaustion phenotype that manifests at a terminal stage, acquired early in life but only after reaching the peripheral environment. This phenotype is independent of type I interferons and does not rely on intrinsic STING activation in either T cells or stromal cells. Mechanistically, the limited number of mature T cells that reach the periphery appear to be quickly impacted by the lymphopenic environment, experiencing heightened stimulation of the IL-7 receptor and TCR pathways, including the NFAT pathway, a key factor in T cell exhaustion. By performing transplantation experiments with STING GOF long term-hematopoietic stem cells (LT-HSCs) along with supportive wild-type bone marrow (BM) cells, we were able to prevent the T cell exhaustion of STING GOF T cells in the resulting non-lymphopenic context, demonstrating that lymphopenia is a major driver of T cell exhaustion in STING GOF mice. T cell exhaustion, although less severe, was also observed in lymphopenic mice carrying Rag1 hypomorphic mutations. In conclusion, our results, which highlight T cell exhaustion induced by lymphopenia, could have important implications for the management of patients with severe immune deficiencies. HighlightsO_LIWe describe a phenotype of T cell exhaustion in STING GOF V154M mice, which is acquired early in life and in the periphery. C_LIO_LISTING GOF-associated T cell exhaustion is independent of type I IFNs, and STING GOF/activation in T cells or in stromal cells is not sufficient for T cell exhaustion. C_LIO_LILymphopenia is a major driver of T cell exhaustion in STING GOF mice, and increased antigenic/IL-7 stimulation of T cells in the lymphopenic context of STING GOF mice could be implicated in the induction of T cell exhaustion. C_LI

immunology↗