rAAV-based gene therapy (Baker IDI Heart & Diabetes Institute/Monash University/University of Melbourne)

Gene therapy of hypertension requires long-term expression of a therapeutic gene to achieve stable reduction of blood pressure. Human tissue kallikrein (HK) cleaves kininogen to produce a potent vasoactive peptide kinin, which plays an important role in the regulation of the cardiovascular and renal functions. In the present study, we have delivered human kallikrein cDNA with an rAAV vector to explore the potential therapeutic effects of kallikrein on hypertension and related secondary complications. A single tail vein injection of the rAAV-HK vector into the adult spontaneously hypertensive rats resulted in a significant reduction (12.0+/-2.55 mmHg, P<0.05, n=6, ANOVA) of the systolic blood pressure from 2 weeks after vector injection, when compared with the control rAAV-lacZ vector-injected rats. Weekly blood pressure monitoring showed stable hypertension-reduction effect throughout the course of the 20-week experiments. In addition, total urine microalbumin contents decreased as a result of rAAV-HK treatment. Histological analysis of various tissues showed remarkable amelioration of cardiovascular hypertrophy, renal injury and collagen depositions in the rAAV-treated group. Finally, persistent expression of the transgene product HK was confirmed by the enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction. We conclude that rAAV-mediated HK delivery rendered a long-term and stable reduction of hypertension and protected against renal injury, cardiac remodeling in the spontaneously hypertensive rat model. Further studies are warranted for the development of a gene therapy strategy for human hypertension.

Recombinant adeno-associated virus vector (rAAV) is a promising vehicle for gene delivery, but few reports have documented its application in solid organ transplantation. In a rat orthotopic liver transplantation model, we investigated the efficacy of rAAV-mediated human cytotoxic T-lymphocyte-associated antigen 4 and immunoglobulin G (hCTLA4Ig) gene transfer to induce long-term allograft survival.

Dark Agouti and Lewis rats were used as donors and recipients, respectively, in six experimental groups: (a) syngeneic control, (b) no treatment, (c) rAAV-green fluorescent protein, (d) rAAV-hCTLA4Ig, (e) low-dose FK506 for 7 days, and (f) rAAV-hCTLA4Ig and low-dose FK506 for 7 days.

The liver allografts were rejected within 10 days when no treatment was given or rAAV-green fluorescent protein was delivered. rAAV-hCTLA4Ig transduction slightly prolonged the survival time to 11 days. Long-term survival was achieved using the combined treatment of rAAV-hCTLA4Ig and low-dose FK506, whereas grafts were rejected on day 33 in the low-dose FK506 group. A sustained hCTLA4 level in plasma was detected in the combined treatment group from day 5 to day 180. On postoperative day 5, combined treatment significantly decreased the interleukin-2 and interferon-gamma protein levels in the grafts and the number of infiltrating B, T, CD25+, CD4+, CD8+, and NK cells.

This study shows that rAAV-hCTLA4Ig gene transfer combined with low-dose FK506 can achieve long-term liver allograft survival.