Replication of the herpes simplex virus type 1 RL1 mutant 1716 in primary neuronal cell cultures - possible relevance to use as a viral vector

The herpes simplex virus type 1 (HSV-1) RL1 deletion mutant 1716 has proper ties that make it a promising candidate as a viral vector for gene therapy in the human nervous system. These properties include its ability to spread along neural pathways and establish a latent infection in post-mitotic neu rons, while retaining a non-virulent phenotype in vivo and an inability to cause a lytic infection in stationary or fully differentiated cells. In thi s study we used viral replication assays and indirect immunofluorescence to investigate the ability of 1716 to bind to, enter, express genes and produ ce progeny virus in dissociated neuronal cell cultures prepared from rat hi ppocampal, medial septal and dorsal root ganglion (DRG) tissues and in prim ary rat astrocyte cultures. Both heterogeneous cultures and those that had been enriched for neurons were employed. Following both low and high multip licities of virus infection, the behaviour of 1716 was compared with its wi ld-type parent HSV-1 strain 17 in these cultures. It was found that the gro wth of 1716 was significantly impaired compared to wild type HSV-I, with th ese differences being magnified at lower multiplicities of viral infection as well as in neuron-enriched cultures: this impairment is likely to be due to decreased replication, as immunofluorescence assays showed that 1716 bo und to, entered and expressed genes in all neuronal cell types and astrocyt es with similar efficiency to the wild type virus. This ability of 1716 to enter and express genes in different neuronal populations demonstrates its potential suitability as a viral vector. (C) 2000 Elsevier Science B.V. All rights reserved.