Selective gene silencing in activated leukocytes by targeting siRNAs to the integrin lymphocyte function-associated antigen-1

doi:10.1073/pnas.0608491104

Selective gene silencing in activated leukocytes by targeting siRNAs to the integrin lymphocyte function-associated antigen-1

*CBR Institute for Biomedical Research, and
Departments of ^†Anesthesia and
^‡Pediatrics, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115; and
^§Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215

Edited by Owen N. Witte, University of California, Los Angeles, CA, and approved January 5, 2007 (received for review September 26, 2006)

Abstract

Silencing gene expression by RNAi is a powerful method for exploring gene function and validating drug targets and potentially for therapy. Lymphocytes and other primary blood cells are resistant to lipid-based transfection in vitro and are difficult to target in vivo. We show here that antibody-protamine fusion proteins targeting the human integrin lymphocyte function-associated antigen-1 (LFA-1) efficiently deliver siRNAs and specifically induce silencing in primary lymphocytes, monocytes, and dendritic cells. Moreover, a fusion protein constructed from an antibody that preferentially recognizes activation-dependent conformational changes in LFA-1 selectively targets activated leukocytes and can be used to suppress gene expression and cell proliferation only in activated lymphocytes. The siRNA-fusion protein complexes do not cause lymphocyte activation or induce IFN responses. K562 cells expressing latent WT or constitutively activated LFA-1 engrafted in the lungs of SCID mice are selectively targeted by intravenously injected fusion protein–siRNA complexes, demonstrating the potential in vivo applicability of LFA-1-directed siRNA delivery.

Footnotes

^¶To whom correspondence may be addressed. E-mail: shimaoka{at}cbrinstitute.org and lieberman{at}cbr.med.harvard.edu
Author contributions: D.P. and P.Z. contributed equally to this work; D.P., P.Z., C.V.C., J.L., and M.S. designed research; D.P., P.Z., and C.V.C. performed research; C.V.C., J.L., and M.S. contributed new reagents/analytic tools; D.P., P.Z., C.V.C., J.L., and M.S. analyzed data; and D.P., J.L., and M.S. wrote the paper. D.P., P.Z., C.V.C., and M.S. declare no conflict of interest. J.L. declares a financial interest. A prorizional patent on the antibody fusion protein method for siRNA delivery has been licensed.
This article is a PNAS direct submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0608491104/DC1.
Abbreviations:

LFA-1,

lymphocyte function-associated antigen-1;

scFv,

single-chain variable region fragment;

PBMC,

peripheral blood mononuclear cell;

HA,

high-affinity;

TCR,

T cell receptor.