ghout the brain, its long-term expression of transgenes, and its safety. We successfully demonstrate the therapeutic effects of AAV5-QBP1 and AAV5Hsp40 injections on a mouse model of HD. Most interestingly, we found that AAV5-Hsp40 exerts a non-cell autonomous therapeutic effect, possibly via inhibition of the recently-suggested cell-cell transmission of the polyQ protein, indicating a novel therapeutic mode of action of Hsp40. Results AAV5-QBP1 and AAV5-Hsp40 Inhibit Inclusion Body Formation in polyQ Disease Mouse Neurons We employed the R6/2 HD mouse model to investigate the therapeutic effect of AAV-mediated expression of QBP1 and molecular chaperones. We first tested the effect on accumulation of the pathogenic polyQ protein into inclusion bodies in the neurons of R6/2 mice by AAV5 injections. Injections were performed on mice at postnatal day 7 using an infusion pump, which has been shown to lead to widespread delivery of the injected molecules in the brain, and indeed resulted in widespread expression of the transgene throughout the injected brain hemisphere with,30% infection efficiencies. R6/2 mice were injected with AAV5-GFP on one side of the TL32711 chemical information striatum 
and AAV5-QBP1 on the other side, and htt inclusion body formation was compared between the two sides of both the striatum and the cortex. Inclusion bodies were already formed in 36.0% of AAV5-GFP infected neurons in the striatum at 4 weeks of age, which increased to 68.5% at 8 weeks and 73.8% at 14 weeks, and an age dependent increase in inclusion bodies was also observed in the cortex. In contrast, AAV5-QBP1 infected neurons had significantly less inclusion bodies at most time points, and the rates of neurons with inclusion bodies at 8 weeks, for example, were 68.5% for GFP vs 33.7% for QBP1 in the striatum, and 49.3% for GFP vs 27.4% for QBP1 in the cortex. These results demonstrate a significant inhibitory effect of AAV5-QBP1 on inclusion body formation. We also tested the effect of AAV5-mediated expression of a molecular chaperone on inclusion body formation. Among the various molecular chaperones, we chose to use a member of the Hsp40 family, namely DNAJB1, since members of the DNAJB subfamily have been Non-Cell Autonomous Effect of Hsp40 on polyQ arrowheads. Inclusion body formation in AAV5-QBP1 infected neurons in the striatum and cortex. Inclusion body formation in AAV5-Hsp40 infected neurons in the striatum and cortex. In and, data are shown as means 6 SEM of $6 fields of view, in which over 180 cells were counted. Representative results of two mice analyzed are shown. doi:10.1371/journal.pone.0051069.g001 reported to be the most potent suppressors of expanded polyQ protein aggregation and toxicity. The effect of AAV5-Hsp40 on polyQ inclusion body formation in R6/2 mice was investigated at 8 weeks, an age at which AAV5-QBP1 showed a clear inhibitory effect. AAV5-Hsp40 also exerted a robust effect on inclusion body formation, and the rates of virus infected neurons with inclusion bodies were 68.6% for GFP vs 41.7% for Hsp40 in the striatum, and 47.5% for GFP vs 9.2% for Hsp40 in the cortex. This difference in the effectiveness of Hsp40 between the two brain areas may be due to differences in the expression levels of its partner Hsp70. Although whether polyQ inclusion bodies themselves are cytotoxic or cytoprotective has been controversial, we assume that suppression of inclusion body formation by QBP1 and Hsp40 can be regarded as a therapeutic effect, since they act by pr
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