Retrograde Transgene Expression via Neuron-Specific Lentiviral Vector Depends on Both Species and Input Projections.

For achieving retrograde gene transfer, we have so far developed two types of lentiviral vectors pseudotyped with fusion envelope glycoprotein, termed HiRet vector and NeuRet vector, consisting of distinct combinations of rabies virus and vesicular stomatitis virus glycoproteins. In the present study, we compared the patterns of retrograde transgene expression for the HiRet vs. NeuRet vectors by testing the cortical input system. These vectors were injected into the motor cortex in rats, marmosets, and macaques, and the distributions of retrograde labels were investigated in the cortex and thalamus. Our histological analysis revealed that the NeuRet vector generally exhibits a higher efficiency of retrograde gene transfer than the HiRet vector, though its capacity of retrograde transgene expression in the macaque brain is unexpectedly low, especially in terms of the intracortical connections, as compared to the rat and marmoset brains. It was also demonstrated that the NeuRet but not the HiRet vector displays sufficiently high neuron specificity and causes no marked inflammatory/immune responses at the vector injection sites in the primate (marmoset and macaque) brains. The present results indicate that the retrograde transgene efficiency of the NeuRet vector varies depending not only on the species but also on the input projections.

A note on retrograde gene transfer efficiency and inflammatory response of lentiviral vectors pseudotyped with FuG-E vs. FuG-B2 glycoproteins.

Pseudotyped lentiviral vectors give access to pathway-selective gene manipulation via retrograde transfer. Two types of such lentiviral vectors have been developed. One is the so-called NeuRet vector pseudotyped with fusion glycoprotein type E, which preferentially transduces neurons. The other is the so-called HiRet vector pseudotyped with fusion glycoprotein type B2, which permits gene transfer into both neurons and glial cells at the injection site. Although these vectors have been applied in many studies investigating neural network functions, it remains unclear which vector is more appropriate for retrograde gene delivery in the brain. To compare the gene transfer efficiency and inflammatory response of the NeuRet vs. HiRet vectors, each vector was injected into the striatum in macaque monkeys, common marmosets, and rats. It was revealed that retrograde gene delivery of the NeuRet vector was equal to or greater than that of the HiRet vector. Furthermore, inflammation characterized by microglial and lymphocytic infiltration occurred when the HiRet vector, but not the NeuRet vector, was injected into the primate brain. The present results indicate that the NeuRet vector is more suitable than the HiRet vector for retrograde gene transfer in the primate and rodent brains.

The use of an optimized chimeric envelope glycoprotein enhances the efficiency of retrograde gene transfer of a pseudotyped lentiviral vector in the primate brain.

Lentiviral vectors have been used not only for various basic research experiments, but also for a wide range of gene therapy trials in animal models. The development of a pseudotyped lentiviral vector with the property of retrograde infection allows us to introduce foreign genes into neurons that are localized in regions innervating the site of vector injection. Here, we report the efficiency of retrograde gene transfer of a recently developed FuG-E pseudotyped lentiviral vector in the primate brain by comparing its transduction pattern with that of the parental FuG-C pseudotyped vector. After injection of the FuG-E vector encoding green fluorescent protein (GFP) into the striatum of macaque monkeys, many GFP-immunoreactive neurons were found in regions projecting to the striatum, such as the cerebral cortex, thalamus, and substantia nigra. Quantitative analysis revealed that in all regions, the number of neurons retrogradely transduced with the FuG-E vector was larger than in the FuG-C vector injection case. It was also confirmed that the FuG-E vector displayed explicit neuronal specificity to the same extent as the FuG-C vector. This vector might promote approaches to pathway-selective gene manipulation and provide a powerful tool for effective gene therapy trials against neurological disorders through enhanced retrograde delivery.