Transduction efficacy and retrograde movement of a lentiviral vector pseudotyped by modified rabies glycoprotein throughout the trisynaptic circuit of the rat hippocampus

BACKGROUND: The trisynaptic circuit (entorhinal cortex-dentate gyrus-CA3-CA1) is a key unidirectional network in the hippocampus. Damage to the hippocampus interrupts this circuit and causes neurological disorders. Efficient delivery of therapeutic genes into this network is of great interest with respect to treating trisynaptic circuit pathologies. METHODS: We generated a lentivector system pseudotyped by a variant of rabies glycoprotein, FUG-B2. The efficiency of the vector in the retrograde transduction of the rat hippocampal neurons (i.e. the entorhinal cortex from the dentate gyrus, the dentate gyrus from CA3, and CA3 from CA1) was examined by direct injection of the vector into the dentate gyrus, CA3 and CA1. To distinguish transduction of the neuronal and glial cells, as well as selective retrograde gene transfer, double-staining of the green fluorescent protein (GFP) expressing cells with the specific neuron biomarker NeuN (neuronal nuclear protein) and the specific glia biomarker GFAP (glial fibrillary acidic protein) was performed across the network. RESULTS: The transgene was successfully introduced into the circuit. More than 80% of the neuronal and glial cells at the injection sites preserved GFP expression during the 2-month period after vector injection. Importantly, GFP was expressed selectively in almost 80.0% of the presynaptic neuronal cells by retrograde axonal transport of the vector. CONCLUSIONS: The FUG-B2-based vector system can efficiently introduce the transgene into the rat hippocampal neurons both directly and indirectly through retrograde monosynaptic movement. This efficient and long-lasting gene delivery might provide a tool for treating neurological disorders originating in hippocampal circuits.