Replication-Competent Controlled Herpes Simplex Virus.
We present the development and characterization of a replication-competent controlled herpes simplex virus 1 (HSV-1). Replication-essential ICP4 and ICP8 genes of HSV-1 wild-type strain 17syn+ were brought under the control of a dually responsive gene switch. The gene switch comprises (i) a transactivator that is activated by a narrow class of antiprogestins, including mifepristone and ulipristal, and whose expression is mediated by a promoter cassette that comprises an HSP70B promoter and a transactivator-responsive promoter and (ii) transactivator-responsive promoters that drive the ICP4 and ICP8 genes. Single-step growth experiments in different cell lines demonstrated that replication of the recombinant virus, HSV-GS3, is strictly dependent on an activating treatment consisting of administration of a supraphysiological heat dose in the presence of an antiprogestin. The replication-competent controlled virus replicates with an efficiency approaching that of the wild-type virus from which it was derived. Essentially no replication occurs in the absence of activating treatment or if HSV-GS3-infected cells are exposed only to heat or antiprogestin. These findings were corroborated by measurements of amounts of viral DNA and transcripts of the regulated ICP4 gene and the glycoprotein C (gC) late gene, which was not regulated. Similar findings were made in experiments with a mouse footpad infection model.


OBJECTIVE
The alphaherpesviruses have long been considered vectors for recombinant vaccines and oncolytic therapies. The traditional approach uses vector backbones containing attenuating mutations that restrict replication to ensure safety. The shortcoming of this approach is that the attenuating mutations tend to limit both the immune presentation and oncolytic properties of these vectors. HSV-GS3 represents a novel type of vector that, when activated, replicates with the efficiency of a nonattenuated virus and whose safety is derived from deliberate, stringent regulation of multiple replication-essential genes. By directing activating heat to the region of virus administration, replication is strictly confined to infected cells within this region. The requirement for antiprogestin provides an additional level of safety, ensuring that virus replication cannot be triggered inadvertently. Replication-competent controlled vectors such as HSV-GS3 may have the potential to be superior to conventional attenuated HSV vaccine and oncolytic vectors without sacrificing safety.
Department of Molecular Genetics and Microbiology, University of Florida College of Medicine, Gainesville, Florida, USA.
David C
DC
Bloom
Department of Molecular Genetics and Microbiology, University of Florida College of Medicine, Gainesville, Florida, USA.
Joyce
J
Feller
Department of Molecular Genetics and Microbiology, University of Florida College of Medicine, Gainesville, Florida, USA.
Peterjon
P
McAnany
Hospital Universitario La Paz, IdiPAZ, Madrid, Spain CIBER de Bioingenieria, Biomateriales y Nanomedicina, Barcelona, Spain.
Nuria
N
Vilaboa
HSF Pharmaceuticals SA, La Tour-de-Peilz, Switzerland Department of Physiological Sciences, University of Florida College of Veterinary Sciences, Gainesville, Florida, USA rvoellmy@hsfpharma.com.
Richard
R
Voellmy
D000818:Animals; D002522:Chlorocebus aethiops; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D005812:Genes, Switch; D005818:Genetic Engineering; D005822:Genetic Vectors / Q000737:chemistry* / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006561:Herpes Simplex / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D018259:Herpesvirus 1, Human / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D006614:Hindlimb; D006358:Hot Temperature; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D015735:Mifepristone / Q000494:pharmacology; D009649:Norpregnadienes / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D014709:Vero Cells; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism; D014779:Virus Replication / Q000187:drug effects*
D004279:DNA, Viral; D004268:DNA-Binding Proteins; D018840:HSP70 Heat-Shock Proteins; C491129:HSPA7 protein, human; C045462:ICP8 protein, Simplexvirus; D017874:Immediate-Early Proteins; D009649:Norpregnadienes; D012333:RNA, Messenger; D014759:Viral Envelope Proteins; D014764:Viral Proteins; C038535:glycoprotein gC, herpes simplex virus type 1; C048925:herpes simplex virus, type 1 protein ICP4; D015735:Mifepristone; C094854:ulipristal