LONG-TERM EXPRESSION OF A REPORTER GENE FROM LATENT HERPES-SIMPLEX VIRUS IN THE RAT HIPPOCAMPUS

A problem in utilizing herpes simplex virus (HSV) as a vector for expr ession of foreign genes in CNS neurons has been the inability to facil itate long-term expression of the engineered genes. Previously, we sho wed that the murine moloney leukemia virus LTR would drive beta-galact osidase (beta-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-te rm expression vectors. Following stereotactic injection of 8117/43 (an ICP4 minus, non-replicating virus with the LTR driving the beta-gal g ene, or KD6 (an ICP4 minus non-replicating virus not expressing beta-g al) into the hippocampus of rats, polymerase chain reaction (PCR) anal ysis of viral DNA after 2 months indicated that latent infections were established. Assaying by both x-gal staining and reverse transcriptas e PCR we demonstrate that (1) beta-gal can be detected for at least 6 months in hippocampal neurons, and (2) although the number of beta-gal transcripts in these cells drops considerably by 2 weeks, they can be detected during the period studied. These studies indicate that the L TR promoter is active and affords long-term expression in the CNS, alb eit at comparatively low levels compared to those observed at acute ti mes.