Submitted March 8, 2007
Accepted July 25, 2007
A microRNA-regulated lentiviral vector mediates stable correction of hemophilia B mice
Brian D Brown, Alessio Cantore, Andrea Annoni, Lucia Sergi Sergi, Angelo Lombardo, Patrizia Della Valle, Armando D'Angelo, and Luigi Naldini*
San Raffaele Telethon Institute for Gene Therapy, San Raffaele Scientific Institute, Milan, Italy
Coagulation Service and Thrombosis Research Unit, IRCCS San Raffaele Hospital, Milan, Italy
Vita Salute San Raffaele University, Milano, Italy
* Corresponding author; email: naldini.luigi{at}hsr.it.
A long-standing goal for the treatment of hemophilia B is the development of a gene transfer strategy that can maintain sustained production of clotting factor IX (F.IX) in the absence of an immune response. To this end, we have sought to use lentiviral vectors (LV) as a means for systemic gene transfer. Unfortunately, initial evaluation of LVs expressing F.IX from hepatocyte-specific promoters failed to achieve sustained F.IX expression in hemophilia B mice due to the induction of an anti-F.IX cellular immune response. Further analysis suggested that this may be a result of off-target transgene expression in hematopoietic-lineage cells of the spleen. In order to overcome this problem, we modified our vector to contain a target sequence for the hematopoietic-specific microRNA, mir-142-3p. This eliminated off-target expression in hematopoietic cells, and enabled sustained gene transfer in hemophilia B mice for >280 days post-injection. Treated mice had >10% normal F.IX activity, no detectable anti-F.IX antibodies and were unresponsive to F.IX immunization. Importantly, the mice survived tail-clip challenge, thus demonstrating phenotypic correction of their bleeding diathesis. This work, which is amongst the first applications to exploit the microRNA regulatory pathway, provides the basis for a promising new therapy for the treatment of hemophilia B.
