The doses of DNA encapsulated in THLs and administered IV was 5 or 70μg per rat or primate, respectively, which are equivalent 20 and 12μg/kg body weight, respectively. When the transgene is driven by the widely read SV40 promoter, the levels of luciferase were ~10pg luciferase/mg protein in the monkey brain. High levels of expression were also seen in peripheral tissues that are rich in the target receptor, including liver, spleen, and lung [27, 34]. A 50-fold increase in the tissue levels of luciferase was reported in primates, as compared to Inhibitors,research,lifescience,medical rat and mouse tissues.

The high levels of expression in monkey tissues were associated with intrinsic properties of the HIRMAb that targets the nuclear compartment of the cell [4]. Time course studies in both rodents Inhibitors,research,lifescience,medical and primates demonstrated that the peak of luciferase expression

occurs 48hs following injection of a single IV dose of THLs. The levels of luciferase activity decline thereafter and as a function of time. There are 2 learn more potential mechanisms for the decline in the expression of the transgene, that is, promoter inactivation and plasmid degradation. The levels of both luciferase enzyme activity and plasmid DNA decay in the primate brain and liver were measured, and both processes decayed with a t1/2 of approximately 2 days, which indicates that the transient Inhibitors,research,lifescience,medical duration of the luciferase gene expression is mainly due to plasmid degradation [33]. The organ distribution of the lacZ transgene was also investigated at the cellular level with Inhibitors,research,lifescience,medical histochemistry following THL delivery of a reporter gene driven by the SV40 promoter and designated SV40-lacZ [4, 20, 34]. The latter was used to engineer THLs with either the TfRMAb or the HIRMAb (Table 1). The histochemical detection of the β-galactosidase is shown in Figure 2 for the mouse and the Rhesus monkey. The expression of the transgene

was widely detected through the cortical and subcortical structures of mouse and monkey brain, with a greater gene expression in gray matter relative to white matter in both cerebrum and cerebellum (Figure 2). On the contrary, the β-galactosidase Inhibitors,research,lifescience,medical histochemistry of control uninjected primate brain shows no β-galactosidase activity (Figure 2(b)). Light micrographs of the primate brain shows gene expression out within the choroid plexus epithelium (Figure 2(d)) and the capillary endothelium within white matter (Figure 2(f)). The gene expression was also confirmed within the neurons of the occipital cortex showing the columnar organization of this region in primate brain (Figure 2(e)). The molecular and granular layers of the cerebellum and the Purkinje cells were also positive for the transgene (Figure 2(f)). Confocal microscopy studies with antibodies against either bacterial β-galactoside or the neuronal neuN marker colocalized transgene expression in the neuronal compartment of brain [27, 34].