Efficient delivery of small interfering RNA for inhibition of IL-12p40 expressionin vivo.
BACKGROUND
RNA interference is an evolutionary conserved immune response mechanism that can be used as a tool to provide novel insights into gene function and structure. The ability to efficiently deliver small interfering RNA to modulate gene expressionin vivomay provide new therapeutic approaches to currently intractable diseases.


METHODS
In vitro, siRNA targeting IL-12p40 was delivered to the murine macrophage cell line (J774A.1) encapsulated in a liposome with an IL-12 inducing agent (LPS/IFN-γ) over a number of time points. Controls included a variety of non-target specific siRNA reagents. Supernatants were analyzed for cytokine production while the cells were removed for mRNA profiling.In vivo, siRNA-targeting IL-12p40 was delivered to the murine peritoneal cavity in a therapeutic fashion, after endotoxin (LPS) challenge. Cells from the peritoneal cavity were removed by lavage and analyzed by flow cytometry. Levels of IL-12 present in lavage and in serum were also examined by ELISA.


RESULTS
In this report, we show that IL-12p40 siRNA can specifically silence macrophage expression of IL-12p40 mRNA and IL-12p70 proteinin vitro. We extend this finding to demonstrate that delivery of liposome encapsulated siRNA targeting IL-12p40 to the murine peritoneal cavity can modulate an inflammatory stimulusin vivo. Furthermore, specific siRNA can be used therapeutically after endotoxin challenge to reduce both the local and systemic inflammatory response. Thus, the delivery of siRNA can be used to elicit specific non-permanent inhibition of endogenous protein expression.


CONCLUSIONS
In vitrosilencing of IL-12p40 using siRNA at selected doses leads to specific knockdown of IL-12p70 protein production without inducing type I interferons. Furthermore, siRNA targeting murine IL-12p40 can be used therapeutically to counter an inflammatory responsein vivo.
Flynn
Marion A
MA
Institute of Immunology, National University of Ireland, Maynooth, Co. Kildare, Ireland.
Casey
David G
DG
Institute of Immunology, National University of Ireland, Maynooth, Co. Kildare, Ireland.
Todryk
Stephen M
SM
Institute of Immunology, National University of Ireland, Maynooth, Co. Kildare, Ireland.
Mahon
Bernard P
BP
Institute of Immunology, National University of Ireland, Maynooth, Co. Kildare, Ireland.