title: Inducible gene expression of the human immunodeficiency virus LTR in a replication-incompetent herpes simplex virus vector.
abstract: Although replication-incompetent herpes simplex virus (HSV) vectors have the capability to express foreign genes, successful development of these vectors for gene delivery would require that expression of the foreign gene be regulated. To investigate the feasibility of obtaining inducible expression of a foreign gene in such a vector, a replication-incompetent HSV vector, vd120/LTR beta, was developed that used the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) to express the Escherichia coli lacZ gene. Examination of lacZ expression from the HIV-1 LTR in vd120/LTR beta-infected cells indicated that the LTR was active as a promoter under both replicating and nonreplicating conditions, although expression of lacZ under nonreplicating conditions was approximately 4-fold lower. In addition, the LTR expressed lacZ in a manner distinct from that of well-characterized HSV-1 promoters of each temporal class. The effect of the HIV-1 regulatory protein Tat on expression from the LTR in vd120/LTR beta was examined by infection of two different HeLa-derived cell lines that constitutively expressed Tat, HL2/3, and HLtat. Compared to infection of HeLa cells, lacZ expression from vd120/LTR beta-infected HL2/3 and HLtat cells increased from 4- to 24-fold, depending on the multiplicity of vector infection. Sustained expression of lacZ from the LTR in vd120/LTR beta-infected cells was not observed even in the continuous presence of Tat, although vector could be recovered for up to 5 days after infection. However, the amount of recoverable vector decreased during this time, suggesting that cellular cytotoxicity may account for some of the decrease in Tat-mediated expression from the LTR.
authors.affiliation: Laboratory of DNA Viruses, Food and Drug Administration, Bethesda, Maryland 20892, USA.
authors.forename: M P
authors.initials: MP
authors.lastname: Warden
authors.forename: J P
authors.initials: JP
authors.lastname: Weir
mesh_terms: D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D003673:Defective Viruses / Q000235:genetics* / Q000502:physiology; D017353:Gene Deletion; D015967:Gene Expression Regulation, Viral; D015696:Gene Products, tat / Q000235:genetics / Q000378:metabolism; D017930:Genes, Reporter; D005822:Genetic Vectors; D016325:HIV Long Terminal Repeat; D006367:HeLa Cells; D018259:Herpesvirus 1, Human / Q000235:genetics* / Q000502:physiology; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics; D007763:Lac Operon; D014709:Vero Cells; D014779:Virus Replication; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D015696:Gene Products, tat; D017874:Immediate-Early Proteins; C048925:herpes simplex virus, type 1 protein ICP4; D001616:beta-Galactosidase