Figure 2.

Viral recombinants used to obtain long-term transgene expression in the central nervous system. A schematic of the herpes simplex virus (HSV) genome is shown with its long and short unique regions (U_L and U_S) each flanked by terminal inverted repeats (TR_L and IR_L, TR_S and IR_S). The region of the internal repeats has been expanded to show where transcription of the primary latency-associated transcript (LAT) starts. The position of the major LAT intron is indicated. Scarpini et al. have reported the use of a recombinant virus in which an internal ribosomal entry site (IRES)-linked reporter gene is inserted into a 168-bp deletion within the major LAT-coding region. Lilley et al. have reported the use of a recombinant virus in which a reporter gene under transcriptional control of the HCMV IE promoter has been inserted into an 188-bp deletion which starts 82 bp upstream of the locus used by Scarpini et al.