Long-term expression of a reporter gene from latent herpes simplex virus in the rat hippocampus

• Published in: Brain research. Molecular brain research. 1995-07, Vol.31 (1), p.48-60
• Main Authors: Bloom, David C., Maidment, Nigel T., Tan, Aiko, Dissette, Vivian B., Feldman, Lawrence T., Stevens, Jack G.
• Format: Article
• Language: English
• Subjects: Animals; beta-Galactosidase - analysis; beta-Galactosidase - genetics; Biological and medical sciences; Biotechnology; Central nervous system; Evaluation Studies as Topic; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Enzymologic - physiology; Gene Expression Regulation, Viral - physiology; Gene therapy; Genes, Reporter; Health. Pharmaceutical industry; herpes simplex virus; Herpes virus; Hippocampus; Hippocampus - cytology; Hippocampus - metabolism; Hippocampus - virology; Histocytochemistry; In Situ Hybridization; Industrial applications and implications. Economical aspects; Latent; Male; Neurons - metabolism; Polymerase Chain Reaction; Rats; Rats, Sprague-Dawley; Simplexvirus - genetics; Simplexvirus - physiology; Time Factors; Vector; Virus Latency - genetics; β-Galactosidase
• ISSN: 0169-328X; 1872-6941
• DOI: 10.1016/0169-328X(95)00031-M

A problem in utilizing herpes simplex virus (HSV) as a vector for expression of foreign genes in CNS neurons has been the inability to facilitate long-term expression of the engineered genes. Previously, we showed that the murine moloney leukemia virus LTR would drive β-galactosidase (β-gal) transcription for extended periods from the latent viral genome in sensory, but not motor neurons. In this communication we further evaluate the utility of the LTR promoter for use in long-term expression vectors. Following stereotactic injection of 8117/43 (an ICP4 minus, non-replicating virus with the LTR driving the β-gal gene, or KD6 (an ICP4 minus non-replicating virus not expressing β-gal) into the hippocampus of rats, polymerase chain reaction (PCR) analysis of viral DNA after 2 months indicated that latent infections were established. Assaying by both x-gal staining and reverse transcriptase PCR we demonstrate that (1) β-gal can be detected for at least 6 months in hippocampul neurons, and (2) although the number of β-gal transcripts in these cells drops considerably by 2 weeks, they can be detected during the period studied. These studies indicate that the LTR promoter is active and affords long-term expression in the CNS, albeit at comparatively low levels compared to those observed at acute times.