RESUMO
BACKGROUND: Erythropoietin (EPO) is a 30.4kDa glycoprotein that serves as the primary regulator of red cell production in mammals. Recombinant erythropoietin has been used in the treatment of anemia associated with numerous chronic diseases. Ex vivo therapy of recombinant EPO, however, requires large dose and frequent administration, which gives financial impact to the patients. In vivo delivery of EPO using gene therapy method can solve this problem. METHODS: Recombinant lentiviral vectors containing the rat EPO gene were made by co-transfection of 293T cell with pRRL-cPPT-CMV-EPO-PRE-SIN, pMDL, pVSVG, and pREV plasmids. These viruses were concentrated and intramusculary injected into the groin muscles of Fisher 344 rats. Sequential complete blood counts were measured periodically thereafter. RESULTS: Virus doses of 6x107 infectious units and 6x106 infectious units produced significantly increased hemoglobin and hematocrit values, being 24.9+/-0.19g/dL, 66.9+/-0.62% (P < 0.01, N=5) and 18.4+/-0.55g/dL, 54.6+/-1.71%(P < 0.01, N=5), respectively at 40 weeks after injection, over values of control animals receiving normal saline (15.2+/-0.42g/dL, 44.6+/-0.49%, N=5). CONCLUSION: Lentiviral vectors are able to transduce skeletal muscle and are capable of achieving sustained expression and systemic delivery of EPO following intramuscular administration. Gene therapy using lentiviral vectors may provide a practical strategy for in vivo delivery of therapeutic proteins.