Hexamethylene bisacetamide leads to reduced helper virus-free HSV-1 amplicon expression titers via suppression of ICP0.
The herpes simplex virus (HSV)-derived amplicon vector has evolved into a promising gene transfer platform for widespread DNA delivery in gene replacement strategies and vaccine development given its ease of molecular manipulation, large transgene capacity, and transduction efficiencies of numerous cell types in vivo. The recent development of helper virus-free packaging methodologies bodes well for this vector system in its eventual implementation as a clinically viable therapeutic modality. For realization of clinical application, efforts have been made to enhance yields and quality of helper-free amplicon stocks. Hexamethylene bisacetamide (HMBA), a hybrid polar compound that exhibits stimulatory activity of HSV-1 immediate-early gene expression, has been employed as a standard reagent in helper virus-free packaging given its purported mode of action on virus gene expression kinetics. Unexpectedly, we have found that HMBA exhibits no titer-enhancing activity; in contrast, the compound enhances the proportion of amplicon virions that are non-expressive. Omission of HMBA during vector packaging led to a marked reduction in the ratios of vector genome-transducing to transgene-expressing virions. This effect was neither packaging-cell-specific nor amplicon-promoter-dependent. Analysis of resultant vector stocks indicated amplicon genome replication/concatenation was unaffected, but the level of particle-associated ICP0 was reduced in stocks packaged in the presence of HMBA. Inclusion of a co-transfected, ICP0-expressing plasmid into the packaging process led to significant rescue of amplicon expression titers, indicating that regulation of ICP0 concentrations is critical for maintenance of the amplicon genome expressive state.
Department of Neurology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA.
Clark A
CA
Burris
Suresh
S
de Silva
Wade C
WC
Narrow
Ann E
AE
Casey
Louis T
LT
Lotta
Howard J
HJ
Federoff
William J
WJ
Bowers
D000081:Acetamides / Q000494:pharmacology*; D000818:Animals; D022003:Cell Nucleus Structures / Q000187:drug effects / Q000378:metabolism; D002522:Chlorocebus aethiops; D015967:Gene Expression Regulation, Viral / Q000187:drug effects; D006378:Helper Viruses / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D018259:Herpesvirus 1, Human / Q000187:drug effects* / Q000235:genetics*; D017874:Immediate-Early Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D011401:Promoter Regions, Genetic / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D044767:Ubiquitin-Protein Ligases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D014709:Vero Cells; D014771:Virion / Q000187:drug effects; D019065:Virus Assembly / Q000187:drug effects
D000081:Acetamides; D017874:Immediate-Early Proteins; D044767:Ubiquitin-Protein Ligases; C051804:Vmw110 protein, Human herpesvirus 1; C014026:hexamethylene bisacetamide