Thromboinflammatory pathways triggered by gut dysbiosis in patients with Lupus

Imbalances in the gut microbiome have been documented in patients with Systemic Lupus erythematosus (SLE), an archetypic systemic autoimmune disease that is associated with great morbidity and premature death, especially in the ~40% with Lupus Nephritis (LN). While studies of lupus-prone mice have suggested potential microbiome-related pathogenic pathways, little is known about the mechanisms by which gut community alterations affect lupus pathogenesis. Our recent longitudinal studies identified patients with flares of LN, concurrent with great intestinal expansions (or blooms) of a candidate gut pathobiont species. In murine systems, pathobiont blooms induced high-level gut permeability, microbial translocation and inflammatory responses. To perform unbiased surveys of possible effects on immune activation, we generated blood bulk RNA-seq libraries from groups of patients at time of high disease activity, and compared to matched controls. We have assembled a multi-disciplinary team to now test a novel data-driven mechanistic hypothesis: that intestinal blooms of this pathobiont contribute to lupus flares through systemic release of microbial factors causing platelet activation and thromboinflammation, pathways first documented in patients with sepsis. In Aim 1, we will focus on human systems, and in feasibility studies we will analyze RNA-seq libraries from individual patients over time, to determine whether this platelet activation profile fluctuates with disease activity, or if it represents a persistent state. We will also interrogate public data sets to investigate whether these pathways are common in other SLE cohorts. Established in vitro assay systems will characterize phenotypic and functional changes in platelets isolated from patients representative of bloom and non bloom active LN groups, non-renal SLE patients and healthy controls. Using naïve human cells, and stimulation with killed candidate pathobiont, co-cultured with strains isolated from SLE patients or healthy individuals, or pathobiont- derived immune active components, we will directly test for in vitro capacity to directly activate human platelets, implicated in the pathogenesis of LN. In Aim 2, we will assess the feasibility of using murine models, by in vitro and in vivo testing, to assess whether components of the gut microbiome trigger these postulated immune pathways implicated in Lupus pathogenesis. Our mechanistic studies will utilize the same set of stimulants and microbiome factors used in Aim 1 in established murine models emulating the human system.