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Travis S. Tierney and Andres M. Lozano

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Richard E. Clatterbuck, Philippe Gailloud, Travis Tierney, Victoria M. Clatterbuck, Kieran J. Murphy and Rafael J. Tamargo

Object. Results of prior studies in rats and rabbits show that the alteration of vasomotor tone in vasospasm following periadventitial blood exposure may be reversed, at least in part, by the administration of compounds releasing nitric oxide (NO). The authors have now generalized this finding to nonhuman primates.

Methods. Ten cynomolgus monkeys underwent cerebral angiography before and 7 days following the induction of subarachnoid hemorrhage (SAH) by the placement of 2 to 3 ml clotted autologous blood around the supraclinoid carotid, proximal anterior cerebral, and proximal middle cerebral arteries. An ethylene vinyl acetate copolymer, either blank (five animals) or containing 20% w/w (Z)-1-[2-(2-aminoethyl)-N-(2-aminoethyl)amino]diazen-1-ium-1,2-diolate (DETA/NO, 4.3 mg/kg; five animals) was placed adjacent to the vessels at the time of surgery. Animals were killed on Day 7 post-SAH following repeated cerebral angiography. The mean percentage of control vascular areal fraction was calculated from angiograms. Cerebral vessels were sectioned and the mean percentage of lumen patency was calculated.

One animal that had received the DETA/NO polymer died prior to repeated angiography. In the remaining animals, DETA/NO caused a significant decrease in vasospasm compared with controls, according to both angiographic (84.8 ± 8.6 compared with 56.6 ± 5.2%, respectively, p < 0.05) and histological studies (internal carotid artery 99.3 ± 1.8 compared with 60.1 ± 4.4%, respectively, p < 0.001; middle cerebral artery 98.4 ± 3 compared with 56.1 ± 3.7%, respectively, p < 0.001; and anterior cerebral artery 89.2 ± 8.5 compared with 55.8 ± 6.3%, respectively, p < 0.05).

Conclusions. The controlled release of DETA/NO is effective in preventing delayed cerebral vasospasm in an SAH model in nonhuman primates. The death of one animal in the treatment group indicates that the present dosage is at the threshold between therapeutic efficacy and toxicity.

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Carlos E. Sanchez, Travis S. Tierney, John T. Gale, Kambiz N. Alavian, Ayguen Sahin, Jeng-Shin Lee, Richard C. Mulligan and Bob S. Carter

Object

Although several clinical trials utilizing the adeno-associated virus (AAV) type 2 serotype 2 (2/2) are now underway, it is unclear whether this particular serotype offers any advantage over others in terms of safety or efficiency when delivered directly to the CNS.

Methods

Recombinant AAV2–green fluorescent protein (GFP) serotypes 2/1, 2/2, 2/5, and 2/8 were generated following standard triple transfection protocols (final yield 5.4 × 1012 particles/ml). A total of 180 μl of each solution was stereotactically infused, covering the entire rostrocaudal extent of the caudoputamen in 4 rhesus monkeys (Macaca mulatta) (3.0 ± 0.5 kg). After 6 weeks' survival, the brain was formalin fixed, cut at 40 μm, and stained with standard immunohistochemistry for anti-GFP, anticaspase-2, and cell-specific markers (anti–microtubule-associated protein-2 for neurons and anti–glial fibrillary acidic protein for glia). Unbiased stereological counting methods were used to determine cell number and striatal volume.

Results

The entire striatum of each animal contained GFP-positive cells with significant labeling extending beyond the borders of the basal ganglia. No ischemic/necrotic, hemorrhagic, or neoplastic change was observed in any brain. Total infusate volumes were similar across the 4 serotypes. However, GFP-labeled cell density was markedly different. Adeno-associated virus 2/1, 2/2, and 2/5 each labeled < 8000 cells/mm3, whereas serotype 8 labeled > 21,000 cells, a 3- to 4-fold higher transduction efficiency. On the other hand, serotype 8 also labeled neurons and glia with equal affinity compared with neuronal specificities > 89% for the other serotypes. Moderate caspase-2 colabeling was noted in neurons immediately around the AAV2/1 injection tracts, but was not seen above the background anywhere in the brain following injections with serotypes 2, 5, or 8.

Conclusions

Intrastriatal delivery of AAV2 yields the highest cell transduction efficiencies but lowest neuronal specificity for serotype 8 when compared with serotypes 1, 2, and 5. Only AAV2/1 revealed significant caspase-2 activation. Careful consideration of serotype-specific differences in AAV2 neurotropism, transduction efficiency, and potential toxicity may affect future human trials.