Recombinant adeno-associated virus serotypes 2- and 5-mediated gene transfer in the mammalian brain: quantitative analysis of heparin co-infusion.

Recombinant adeno-associated viruses (rAAVs) are among the most promising vectors for gene delivery into the CNS. However, a major hurdle for gene transfer to the mammalian brain is to achieve high transduction levels in target cells beyond the immediate injection site. Therefore, building upon the optimization of injection parameters on which we have recently reported, it is important to define additional methods to increase the volume of distribution. Here, we establish an optimal heparin concentration, and show that co-injection of heparin together with rAAV2 leads to a significantly higher and more homogeneous distribution of transduced cells. In contrast, the diffusion pattern of rAAV serotype 5 differs from that of rAAV2, in that its distribution is less homogeneous, more variable, and patchy. Furthermore, this study illustrates the influence of receptor binding on the expression pattern following injection of rAAV in the CNS. In addition to improvements in expression cassettes and viral titers and the use of very slow infusion rates, gene transfer studies in the CNS where the goal is to obtain widespread transduction should consider co-injecting the viral vector rAAV2 with heparin to maximize transduction efficiency and viral spread.