Transduction characteristics of adeno-associated virus vectors expressing cap serotypes 7, 8, 9, and Rh10 in the mouse brain.

Recombinant adeno-associated viral (AAV) vectors can transduce cells of the CNS, resulting in long-term expression. AAV vector transduction varies depending on the serotype used and the region of the brain injected. AAV serotypes 7, 8, 9, and Rh10 have recently become available, but the transduction capabilities of these serotypes within the CNS have not been determined. We show that AAV 7, 8, 9, and Rh10 vectors expressing cDNA for a lysosomal enzyme transduce neurons, but not astrocytes or oligodendrocytes, in the cortex, striatum, hippocampus, and thalamus. Although all of the vectors contained the same genome, there were markedly different transduction patterns that could be due only to the differences in capsid proteins. The AAV 9 vector was found to undergo vector genome transport to distal neuronal cell bodies via known axonal pathways. This facilitated the distribution of enzyme, resulting in correction of lysosomal storage lesions in regions of a diseased brain that would not be corrected if the genome were not transported.

Increased susceptibility to the pathogenic effects of wild-type and recombinant herpesviruses in MPS VII mice compared to normal siblings.

In previous studies, we have shown that a herpesvirus vector can transfer a therapeutic cellular gene (beta-glucuronidase) from peripheral sites of inoculation into the central nervous system in mice with a model neurodegenerative disease caused by a deficiency of this enzyme (mucopolysaccharidosis type VII, Sly disease). The vector corrects the enzymatic deficiency in transduced cells but the number of cells corrected is too low to alter the pathology of the disease. The recombinant vector virus, which has the foreign gene substituted into the viral LAT locus, had reduced pathogenicity after corneal inoculation compared to the wild-type virus from which it was derived (HSV-1 strain 17+). We therefore attempted to increase the number of corrected cells in the MPS VII brain by increasing the inoculating dose of the vector. However, the vector was acutely pathogenic in the diseased mice at doses that were non-pathogenic in normal littermates. The pathogenic effect of the vector virus in the mutants could be blocked by passive immunization with human gamma-globulin containing anti-HSV-1 antibodies on the day of infection but not when given at the peak of viral replication (day 4). However, effective protection also blocked transduction by the vector, thereby abrogating the effects of increased vector dosage. The effect was virus specific because inoculation of a high dose of a non-pathogenic variant of strain 17+ virus (1716) directly into the brains of MPS VII mice was not lethal. We found no apparent differences in the acute inflammatory response in mutant versus normal animals. These data suggest that the increased susceptibility to vector virulence was related to the overall compromised state of health of the diseased animals, which is further supported by the observations that the mutant mice are more sensitive to stress and to anesthetics than normal littermates. These findings indicate that adverse effects of gene transfer vectors for genetic diseases may not be fully apparent when tested in normal animals.