Adenovirus-mediated transgene expression in nonhuman primate brain

Transgene expression in the brain of St. Kitts green monkey, Cercopithecus aethiops sabeus, was studied following injection of a serotype 5 adenoviral vector deleted in E1 and E3, The vector harbored the transgene for Escheri chia coli beta-galactosidase (beta-Gal) with the simian virus 40 (SV40) nuc lear localization signal under control of the Rous sarcoma viral (RSV) long terminal repeat. Several titers ranging from 5 x 10(7) to 2 x 10(9) plaque -forming units (PFU) in volumes ranging from 5 to 250 mu l were injected in to the caudate nuclei of 18 monkeys. Monkeys were treated with dexamethason e for 9 days, beginning the day prior to surgery, and were sacrificed at 1 week or at 1, 2, or 3 months. At 1 week, beta-Gal was expressed in thousand s of cells, including both neurons and astrocytes. In addition, some dopami nergic neurons in the substantia nigra expressed transgene, suggesting retr ograde transport of the vector. At 1 month 162,000 +/- 68,000 (SEM) or 65,0 00 +/- 29,000 beta-Gal-expressing cells persisted in striatum injected with 6 x 10(8) PFU in 30 mu l or 5 x 10(7) PFU in 5 mu l, respectively, Transge ne expression was also observed in one of two monkeys sacrificed at 2 month s and in a single monkey sacrificed at 3 months, No transgene expression wa s observed at 1 month in striatum injected with a higher titer (2 x 10(9) P FU in 100 mu l) or more dilute vector (5 x 10(7) PFU in 30 mu l), Staining for the major histocompatibility complex II (MHC II) subtype DR showed inte nse staining in sites injected with a higher vector titer, in which no tran sgene persisted at 1 month, whereas low to moderate staining was present in sites with high transgene expression. These observations suggest that ther e is an optimal range of vector titers for obtaining persistent transgene e xpression from E1E3-deleted adenovirus in primate brain, above which host r esponses limit transgene stability.