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Adeno-associated virus (AAV)-based vectors are promising vehicles for therapeutic gene delivery, including for the treatment for heart failure. It has been demonstrated for each of the AAV serotypes 1 through 8 that inhibition of the proteasome results in increased transduction efficiencies. For AAV9, however, the effect of proteasome inhibitors on in vivo transduction has until now not been evaluated. Here we demonstrate, in a well-established rodent heart failure model, that concurrent treatment with the proteasome inhibitor bortezomib does not enhance the efficacy of AAV9.SERCA2a to improve cardiac function as examined by echocardiography and pressure volume analysis. Western blot analysis of SERCA2a protein and reverse transcription-PCR of SERCA2a mRNA demonstrated that bortezomib had no effect on either endogenous rat SERCA2a levels nor on expression levels of human SERCA2a delivered by AAV9.SERCA2a. Similarly, the number of AAV9 genomes in heart samples was unaffected by bortezomib treatment. Interestingly, whereas transduction of HeLa cells and neonatal rat cardiomyocytes by AAV9 was stimulated by bortezomib, transduction of adult rat cardiomyocytes was inhibited. These results indicate an organ/cell-type-specific effect of proteasome inhibition on AAV9 transduction. A future detailed analysis of the underlying molecular mechanisms promises to facilitate the development of improved AAV vectors. [ABSTRACT FROM AUTHOR]

Recombinant adeno-associated (AAV) viruses have unique properties, which make them ideal vectors for gene transfer targeting the myocardium. Numerous serotypes of AAV have been identified with variable tropisms towards cardiac tissue. In the present study, we investigated the time course of expression of eight different AAV serotypes in rat myocardium and the nature of the immunity against these serotypes. We first assessed whether neutralizing antibodies (NAb) were present for any of the serotype in the rats. We injected 100 μl of each AAV 1–8 serotype (1012 DNAse resistant particles/ml), encoding LacZ gene, into the apical wall of rat myocardium. At 1, 4, 12 and 24 weeks after gene delivery, the animals were killed and β-galactosidase (β-gal) activity was assessed by luminometry. Additionally, LacZ genomic copies and AAV capsids copies were measured through standard polymerase chain reaction analysis and cryo-sections from the area of viral injection were stained for X-gal detection at the same time points. No NAbs were detected against any of AAV serotypes. At all the time points studied, AAV1, 6 and 8 demonstrated the highest efficiency in transducing rat hearts in vivo. Parallel to the results with β-gal activity, the highest levels LacZ and AAV DNA genomic copies were with AAV1, 6 and 8. The positive X-gal staining depicted by these serotypes confirmed these results. These results indicate that among the various AAV serotypes, AAV1, 6 and 8 have differential tropism for the heart unaffected by pre-existing NAb in the rat. Although AAV 1 and 6 vectors induced rapid and robust expression and reach a plateau at 4 weeks, AAV 8 continued increasing until the end of the study. AAV 2, 5 and 7 vectors were slower to induce expression of the reporter gene, but did reach levels of expression comparable to AAV1 and AAV6 vectors after 3 months.Gene Therapy (2007) 14, 989–997. doi:10.1038/sj.gt.3302895; published online 25 January 2007 [ABSTRACT FROM AUTHOR]

Presents a study on kick-starting calcium cycling in rats. Presentation of a novel approach to gene therapy for heart failure; Importance of calcium movement to the process of excitation–contraction coupling in cardiac myocytes; Use of molecular targeting to enhance calcium cycling and increase contractility in the failing heart.