Targeted delivery of HMGB1 siRNA to macrophages and dendritic cells for sepsis treatment in humanized mouse model (P6223)

Abstract

Abstract Over expression cytokine by innate immune cells is thought to initiate multiple organ failure in murine models of sepsis. Whether human cytokine storm also plays a similar role is not clear. Here we show that human hematopoietic cells are required to induce sepsis-induced mortality following cecal ligation and puncture (CLP) in the severely immunodeficient NOD/SCID/IL2Rγ-/- mice and siRNA treatment to inhibit HMGB1 release by human macrophages and dendritic cells dramatically reduces sepsis-induced mortality. Following CLP, as compared to immunocompetent WT mice, NOD/SCID/IL2Rγ-/- mice did not show high levels of serum HMGB1 or murine proinflammatory cytokines and were relatively resistant to sepsis-induced mortality. In contrast, NOD/SCID/IL2Rγ-/- mice transplanted with human hematopoietic stem cells (humanized BLT mice) showed high serum levels of HMGB1 as well as multiple human, but not murine proinflammatory cytokines and uniformly succumbed, suggesting human cytokines are sufficient to induce organ failure in this model. Moreover, targeted delivery of HMGB1 siRNA to human macrophages and dendritic cells using a short AchR binding peptide (RVG-9R) effectively suppressed secretion of HMGB1, reduced the human cytokine storm, human lymphocyte apoptosis and rescued humanized mice from CLP-induced mortality. SiRNA treatment was also effective when started after the appearance of sepsis symptoms. These results show that: CLP in humanized mice provides a model to study human sepsis; HMGB1 siRNA might provide a treatment strategy for human sepsis; and RVG-9R provides a tool to deliver siRNA to human macrophages and dendritic cells that could potentially be used suppress a variety of human inflammatory diseases.