scFv-EM48 reduces neuropil aggregates in HD mouse brains. (A) Immunostaining of the mouse brain with rabbit anti-HA (red) and mouse anti-NeuN (green) confirms that scFv-EM48-HA is expressed in neurons. Merged image is also shown. (B and C) Immunostaining of the striatum of R6/2 mice (B) and the cortex of N171-82Q HD mice that were injected with adenoviral vector (control virus) or adenoviral scFv-EM48 (C). Rabbit EM48 was used to stain transgenic htt (green). scFv-EM48 staining is not shown separately but can be seen in the merged images in which scFv-EM48-HA (red) is stained by mouse antibody to the HA epitope, and nuclei (blue) were revealed with Hoechst dye. Note that small neuropil aggregates were decreased in the adenoviral scFv-EM48–injected area. Bars, 5 μm. (D) Quantitative assessment of neuropil aggregate density in R6/2 and N171-82Q mice. The values represent the number of neuropil aggregates per image (630×) relative to the noninjected contralateral area. The data are presented as means ± standard error. **, P <0.01.