Targeted delivery of siRNA to cell death proteins in sepsis.

Immune suppression is a major cause of morbidity and mortality in the patients with sepsis. Apoptotic loss of immune effector cells such as CD4 T and B cells is a key component in the loss of immune competence in sepsis. Inhibition of lymphocyte apoptosis has led to improved survival in animal models of sepsis. Using quantitative real-time polymerase chain reaction of isolated splenic CD4 T and B cells, we determined that Bim and PUMA, two key cell death proteins, are markedly upregulated during sepsis. Lymphocytes have been notoriously difficult to transfect with small interfering RNA (siRNA). Consequently a novel, cyclodextrin polymer-based, transferrin receptor-targeted, delivery vehicle was used to coadminister siRNA to Bim and PUMA to mice immediately after cecal ligation and puncture. Antiapoptotic siRNA-based therapy markedly decreased lymphocyte apoptosis and prevented the loss of splenic CD4 T and B cells. Flow cytometry confirmed in vivo delivery of siRNA to CD4 T and B cells and also demonstrated decreases in intracellular Bim and PUMA protein. In conclusion, Bim and PUMA are two critical mediators of immune cell death in sepsis. Use of a novel cyclodextrin polymer-based, transferrin receptor-targeted siRNA delivery vehicle enables effective administration of antiapoptotic siRNAs to lymphocytes and reverses the immune cell depletion that is a hallmark of this highly lethal disorder.