Recombinant Semliki Forest virus and Sindbis virus efficiently infect neurons in hippocampal slice cultures

Gene transfer into nervous tissue is a powerful tool for the analysis of ge ne function. By using a rat hippocampal slice culture preparation, we show here that Semliki Forest virus (SFV) and Sindbis virus (SIN) vectors are us eful for the effective infection of neurons. The stratum pyramidale and/or the granular cell layer were injected with recombinant virus encoding beta- galactosidase (LacZ) or green fluorescent protein (GFP), By using low conce ntrations of injected SFV-LacZ or SIN-LacZ, we detected LacZ staining of py ramidal cells, interneurons, and granule cells. About 60% of the infected c ells showed clear neuronal morphology; thus, relatively few glial cells exp ressed the transgene. Expression of GFP from SFV and SIN vectors gave simil ar results, with an even higher percentage (>90%) of the GFP-positive cells identified as neurons. Infected pyramidal cells were readily recognized in living slices, displaying GFP fluorescence in dendrites of up to fourth or der and in dendritic spines. They appeared morphologically normal and viabl e at 1-5 days postinfection. We conclude that both SFV and SIN vectors effi ciently transfer genes into neurons in hippocampal slice cultures, In combi nation with the GFP reporter, SFV and SIN vectors will allow the physiologi cal examination of identified neurons that have been modified by overexpres sion or suppression of a specific gene product.