Carla Johnson

Cerebral malaria (CM) is a potentially lethal complication of Plasmodium falciparum infection characterized by blood-brain barrier disruption and brain hemorrhage. Although immune-mediated endothelial damage is central to CM pathology, the mechanisms linking cytotoxic immune responses to endothelial injury remain unclear. Here, we show that CD8 ⁺ T cells induce receptor-interacting serine/threonine-protein kinase 1 (RIPK1)–regulated cell death of brain endothelial cells in mouse CM, while RIPK1 phosphorylation is increased in brain endothelial cells in human CM. Using magnetic resonance imaging, three-dimensional tissue-cleared brain imaging, cross-species pathology, endothelial translatomics, immunocerebrovascular interactomics, and genetic association testing, we identify a CD8 ⁺ T cell–dependent, RIPK1-centered mouse endothelial cell death program. Combined RIPK1 and caspase inhibition protected cross-presenting endothelial cells from CD8 ⁺ T cell–mediated death in vitro. In vivo, brain endothelial-specific genetic inactivation or systemic pharmacological inhibition of RIPK1 kinase activity prolonged survival in mouse CM without altering parasitemia. These findings support RIPK1 inhibition as a promising therapeutic strategy to counter CD8 ⁺ T cell–induced endothelial death in CM.

Vascular injury and coagulopathy are key drivers of mortality in bacterial sepsis. In Neisseria meningitidis infection, endothelial adhesion and thrombosis cause the characteristic petechial rash and, in the most severe cases, purpura fulminans. Although antibiotics rapidly kill bacteria, inflammation and vascular injury often persist or worsen after bacterial clearance, suggesting ongoing toxicity from released bacterial components. Here we identify bacterial histone-like proteins (HLPs), small positively charged DNA-binding proteins conserved across bacterial species, as previously unrecognized mediators of vascular damage. In vitro HLPs are released following antibiotic exposure, disrupting endothelial integrity. In patients with severe sepsis, they are detectable in plasma and tissue, colocalising with areas of vascular leak and coagulopathy. Non-anticoagulant heparins and anti-HLP antibodies neutralize HLP-induced endothelial disruption and toxicity in vitro and in vivo . These findings reveal HLPs as antibiotic-released bacterial toxins and suggest new therapeutic strategies to prevent vascular injury in sepsis. One sentence summary: Antibiotic treatment of meningococcal and other sepsis causative bacteria triggers the release of histone-like proteins (HLPs) that damage the endothelium and drive coagulopathy, but these effects can be neutralized by non-anticoagulant heparins or anti-HLP antibodies.

Postmortem single-cell studies have transformed understanding of lower respiratory tract diseases (LRTDs), including coronavirus disease 2019 (COVID-19), but there are minimal data from African settings where HIV, malaria and other environmental exposures may affect disease pathobiology and treatment targets. In this study, we used histology and high-dimensional imaging to characterize fatal lung disease in Malawian adults with (n = 9) and without (n = 7) COVID-19, and we generated single-cell transcriptomics data from lung, blood and nasal cells. Data integration with other cohorts showed a conserved COVID-19 histopathological signature, driven by contrasting immune and inflammatory mechanisms: in US, European and Asian cohorts, by type I/III interferon (IFN) responses, particularly in blood-derived monocytes, and in the Malawian cohort, by response to IFN-γ in lung-resident macrophages. HIV status had minimal impact on histology or immunopathology. Our study provides a data resource and highlights the importance of studying the cellular mechanisms of disease in underrepresented populations, indicating shared and distinct targets for treatment.