Preparation of herpes simplex virus of high titer

Opportunities, Technology, and the Joy of Discovery

My grandparents were immigrants. My paternal grandfather was illiterate. Yet my parents were able to complete college and to become teachers. I had a conventional upbringing in a small town in Florida, graduating from high school in 1960. I was fortunate enough to graduate cum laude from Florida State University and to earn other credentials leading to faculty positions at outstanding institutions of higher education: the University of Chicago and Northwestern University. At a time when women were rarely the leaders of research groups, I was able to establish a well-funded research program and to make contributions to our understanding of viral entry into cells. My best research was done after I became confident enough to seek productive interactions with collaborators. I am grateful for the collaborators and collaborations that moved our field forward and for my trainees who have gone on to successes in many different careers. Expected final online publication date for the Annual Review of Virology, Volume 9 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

miRNAs Targeting ICP4 and Delivered to Susceptible Cells in Exosomes Block HSV-1 Replication in a Dose-Dependent Manner

miRNAs are potent tools that in principle can be used to control the replication of infectious agents. The objectives of the studies reported here were to design miRNAs that can block the replication of herpes simplex virus 1 and which could be delivered to infected cells via exosomes. We report the following: (1) We designed three miRNAs targeting the mRNA encoding ICP4, an essential viral regulatory protein. Of the three miRNAs, one miRNA401 effectively blocked ICP4 accumulation and viral replication on transfection into susceptible cells. (2) To facilitate packaging of the miRNA into exosomes, we incorporated into the sequence of miRNA401 an exosome-packaging motif. miRNA401 was shown to be packaged into exosomes and successfully delivered by exosomes to susceptible cells, where it remained stable for at least 72 hr. Finally, the results show that miRNA401 delivered to cells via exosomes effectively reduced virus yields in a miRNA401 dose-dependent fashion. The protocol described in this report can be applied to study viral gene functions without actually deleting or mutagenizing the gene.

Cells infected with herpes simplex virus 1 export to uninfected cells exosomes containing STING, viral mRNAs, and microRNAs

STING (stimulator of IFN genes) activates the IFN-dependent innate immune response to infection on sensing the presence of DNA in cytosol. The quantity of STING accumulating in cultured cells varies; it is relatively high in some cell lines [e.g., HEp-2, human embryonic lung fibroblasts (HEL), and HeLa] and low in others (e.g., Vero cells). In a preceding publication we reported that STING was stable in four cell lines infected with herpes simplex virus 1 and that it was actively stabilized in at least two cell lines derived from human cancers. In this report we show that STING is exported from HEp-2 cells to Vero cells along with virions, viral mRNAs, microRNAs, and the exosome marker protein CD9. The virions and exosomes copurified. The quantity of STING and CD9 exported from one cell line to another was inoculum-size-dependent and reflected the levels of STING and CD9 accumulating in the cells in which the virus inoculum was made. The export of STING, an innate immune sensor, and of viral mRNAs whose major role may be in silencing viral genes in latently infected neurons, suggests that the virus has evolved mechanisms that curtail rather than foster the spread of infection under certain conditions.

Similarities and Differences in the Development of Laboratory Strains and Freshly Isolated Strains of Herpes Simplex Virus in HEp-2 Cells: Electron Microscopy

HEp-2 cells infected with two laboratory strains (mP and MP) and two freshly isolated strains (F and G) of herpes simplex virus were fixed at intervals between 4 and 50 hr postinfection and sectioned, and were then examined with the electron microscope. These studies revealed the following. (i) All four strains caused identical segregation of nucleoli and aggregation of host chromosomes at the nuclear membrane. (ii) The development of MP virus could not be differentiated from that of its parent mP strain. (iii) There were quantitative differences between laboratory (mP) and freshly isolated (F) type 1 strains. Thus, cells infected with F contained numerous nuclear crystals of nucleocapsids and relatively few cytoplasmic structures containing enveloped nucleocapsids. Conversely, cells infected with mP or with MP virus contained numerous cytoplasmic structures with enveloped nucleocapsids and relatively few nuclear crystals of nucleocapsids. (iv) There were qualitative differences between type 2 strain (G) isolated from genital lesions and type 1 strains. Thus, cells infected with the G strain contain numerous filaments in nuclei and unenveloped and partially enveloped nucleocapsids in the cytoplasm. Of particular interest is the finding that cytoplasmic membranes in apposition to nucleocapsids were thickened and bent as if they were enveloping the particle. The significance of the qualitative differences in the development of the four strains is discussed.

Quantitation of HSV mass distribution in a rodent brain tumor model

A number of different viral vectors have been used for gene therapy of tumors, with many more under construction, ultimately designed to improve tumor targeting and transduction efficiency. It has become apparent that insufficient viral delivery can be a key limitation to treatment efficacy. We have studied the in vivo mass distribution of a herpes simplex virus type 1 (HSV) vector, hrR3, by radiolabeling it with 111In-oxine. The virus was administered to intracerebral 9L glioma bearing Fisher (F-344) rats by intracarotid and intratumoral injection. The blood half-life of the virus was 1 min (fast component, 10% contribution) and 180 min (slow component, 90% contribution). Approximately 20% of activity had been excreted by 24 h. With intracarotid injection, the total amount of virus that accumulated in tumor was 0.10+/-0.07% of the injected dose (ID)/g at 1 h and 0.19+/-0.01% ID/g at 24 h. By comparison, co-injection of RMP-7, a synthetic bradykinin analog, with the virus, resulted in slightly increased tumor delivery of 0.17+/-0.10% ID/g (P 0.05) at 1 h. The 1 h organ distribution after intra-arterial injection (%ID/organ) was as follows: liver 273+/-2.86%, lung 2.10+/-0.68% and kidney 1.78+/-1.60% with lesser amounts in other organs. When virus was injected directly into the tumor, 71% of virus remained in tumor at 24 h (590+/-212 %ID/g, consistent with the small tumor mass containing most of the virus) with the following distribution regions: tumor > border zone > normal brain (99:40: 1). These studies are the first quantitative mass distribution studies of HSV vectors in an experimental brain tumor model. Localization and quantitation of viral accumulation in vivo will enable detailed analysis of viral and organ interactions critical for advancing the therapeutic use of vectors.

Neural precursor cells for delivery of replication-conditional HSV-1 vectors to intracerebral gliomas

Cellular delivery of a replication-conditional herpes simplex virus type 1 (HSV-1) vector provides a means for gene therapy of invasive tumor cells. LacZ-bearing neural precursor cells, which can migrate and differentiate in the brain, were infected with a ribonucleotide reductase-deficient HSV-1 mutant virus (rRp450) that replicates only in dividing cells. Replication of rRp450 in neural precursor cells was blocked prior to implantation into the tumor by growth arrest in late G1 phase through treatment with mimosine. Viral titers in the medium of mimosine-treated, rRp450-infected neural precursor cells were below detection levels 3 days after infection. In culture, after removal of mimosine and passaging, cells resumed growth and replication of rRp450 so that, 7 days later, virus was present in the medium and cell death was evident. Mimosine-treated neural precursor cells injected into established intracerebral CNS-1 gliomas in nude mice migrated extensively throughout the tumor and into the surrounding parenchyma beyond the tumor over 3 days. Mimosine-treated neural precursor cells, infected with rRp450 and injected into intracerebral CNS-1 tumors, also migrated within the tumor with the appearance of foci of HSV-thymidine kinase-positive (TK+) cells, presumably including tumor cells, distributed throughout the tumor and in the surrounding parenchyma over a similar period. This migratory cell delivery method has the potential to expand the range of delivery of HSV-1 vectors to tumor cells in the brain.

Oncolytic virus therapy of multiple tumors in the brain requires suppression of innate and elicited antiviral responses

The occurrence of multiple tumors in an organ heralds a rapidly fatal course. Although intravascular administration may deliver oncolytic viruses/vectors to each of these tumors, its efficiency is impeded by an antiviral activity present in complement-depleted plasma of rodents and humans. Here, this activity was shown to interact with complement in a calcium-dependent fashion, and antibody neutralization studies indicated preimmune IgM has a contributing role. Short-term exposure to cyclophosphamide (CPA) partially suppressed this activity in rodents and humans. At longer time points, cyclophosphamide also abrogated neutralizing antibody responses. Cyclophosphamide treatment of rats with large single or multiple intracerebral tumors substantially increased viral survival and propagation, leading to neoplastic regression.

Mapping the in vivo distribution of herpes simplex virions

We describe a method for labeling enveloped viral particles with a radiotracer, indium-111, allowing labeled viruses to be traced in vivo by nuclear imaging. After initial optimization experiments, a labeling efficiency of 83% (incorporation yield) was achieved for herpes simplex virus (HSV), resulting in a specific activity of 30 microCi/10(9) PFU. The labeling procedure did not significantly reduce the infectivity of the labeled virus and the virus did not release any significant amounts of the radionuclide within 12 hr after labeling. Sequential imaging of animals after intravenous administration of the labeled virus showed fast accumulation in the liver and redistribution from the blood pool (immediately after injection) to liver and spleen (12-24 hr after injection). At 12 hr after injection 7% of the virus-associated (111)In had been eliminated from the body and the remaining organ distribution of the virus was as follows: spleen 2.87 +/- 0.54% ID/g; liver, 2.60 +/- 0.51% ID/g; kidney, 0.98 +/- 0.31% ID/g; lung, 0.57 +/- 0.10% ID/g; [corrected] and lower amounts in other organs. Our results indicate that the described method allows qualitative and quantitative assessment of viral biodistribution in vivo by nuclear imaging.

Therapeutic efficiency and safety of a second-generation replication-conditional HSV1 vector for brain tumor gene therapy

A second-generation replication-conditional herpes simplex virus type 1 (HSV) vector defective for both ribonucleotide reductase (RR) and the neurovirulence factor gamma34.5 was generated and tested for therapeutic safety and efficiency in two different experimental brain tumor models. In culture, cytotoxic activity of this double mutant HSV vector, MGH-1, for 9L gliosarcoma cells was similar to that of the HSV mutant, R3616, which is defective only for gamma34.5, but was significantly weaker than that of the HSV mutant hrR3, which is defective only for RR. The diminished tumoricidal effect of the gamma34.5 mutants could be accounted for by their reduced ability to replicate in 9L cells. The MGH-1 vector did not achieve significant prolongation of survival in vivo in the syngeneic 9L rat gliosarcoma model for either single brain tumor focus or multiple intracerebral and leptomeningeal tumors, when the vector was applied intratumorally or intrathecally, respectively, and with or without subsequent ganciclovir (GCV) treatment. In identical 9L brain tumor models with single and multiple foci, application of hrR3 with or without GCV was previously shown to result in marked long-term survival. Contrary to the findings with intrathecal injection of hrR3, no vector-related mortality was observed in any animals treated with MGH-1. Thus, in these rat brain tumor models, the double mutant, replication-conditional HSV vector MGH-1 showed a higher therapeutic safety than the RR-minus vector, hrR3, but had clearly decreased therapeutic efficiency compared to hrR3. The development of new HSV vectors for brain tumor gene therapy will require a balance between maximizing therapeutic efficacy and minimizing toxicity to the brain. Standardized application in brain tumor models as presented here will help to screen new HSV vectors for these requirements.

Structure and function in the herpes simplex virus 1 RNA-binding protein U(s)11: mapping of the domain required for ribosomal and nucleolar association and RNA binding in vitro

The herpes simplex virus 1 US11 protein is an RNA-binding regulatory protein that specifically and stably associates with 60S ribosomal subunits and nucleoli and is incorporated into virions. We report that US11/ beta-galactosidase fusion protein expressed in bacteria bound to rRNA from the 60S subunit and not the 40S subunit. This binding reflects the specificity of ribosomal subunit association. Analyses of deletion mutants of the US11 gene showed that specific RNA binding activity, nucleolar localization, and association with 60S ribosomal subunits were found to map to the amino acid sequences of the carboxyl terminus of US11 protein, suggesting that these activities all reflect specific binding of US11 to large subunit rRNA. The carboxyl-terminal half of the protein consists of a regular tripeptide repeat of the sequence RXP and constitutes a completely novel RNA-binding domain. All of the mutant US11 proteins could be incorporated into virus particles, suggesting that the signal for virion incorporation either is at the amino-terminal four amino acids or is redundant in the protein.

Selective uptake of viral and monocrystalline particles delivered intra-arterially to experimental brain neoplasms

In this study we investigated the intra-arterial delivery of viral and nonviral particles to experimental brain tumors. A herpes simplex virus (HSV) vector and monocrystalline iron oxide nanoparticles (MION) were injected into the internal carotid artery of Fisher 344 rats harboring intracerebral 9L gliosarcomas, using bradykinin to disrupt the blood-tumor barrier. Brain and internal organs were stained both for virus-mediated gene expression and for iron. Quantitative comparisons of gene expression and MION uptake with and without blood-tumor barrier disruption were performed in the center and at the periphery of the tumor mass, as well as in normal brain. In addition, MION distribution was traced in vivo by MR imaging. Delivery of HSV into 9L gliosarcoma cells was greatly enhanced by intra-carotid bradykinin infusion. Virus-mediated expression of the HSV-thymidine kinase (TK) and beta-galactosidase gene products was highest at the tumor periphery as compared to the tumor center. Selective HSV infection of multiple tumor foci was achieved in both hemispheres without affecting normal brain. MION uptake was high at the tumor periphery even without blood-tumor barrier disruption. Bradykinin increased MION uptake predominantly in the center of the tumor with virtually no effect at the periphery. These findings show that selective blood-tumor barrier disruption by bradykinin can be used to enhance HSV-mediated gene delivery to tumor cells in the periphery of brain tumors. A crucial aspect in the treatment of malignant brain tumors is the eradication of tumor cells infiltrating the brain; bradykinin may facilitate access of vectors to these areas by selective disruption of their neovasculature.

A herpes simplex virus 1 US11-expressing cell line is resistant to herpes simplex virus infection at a step in viral entry mediated by glycoprotein D

A baby hamster kidney [BHK(tk-)] cell line (US11cl19) which stably expresses the US11 and alpha 4 genes of herpes simplex virus 1 strain F [HSV-1(F)] was found to be resistant to infection with HSV-1. Although wild-type HSV-1(F) attached with normal kinetics to the surface of US11cl19 cells, most cells showed no evidence of infection and failed to accumulate detectable amounts of alpha mRNAs. The relationship between the expression of UL11 and resistance to HSV infection in US11cl19 cells has not been defined, but the block to infection with wild-type HSV-1 was overcome by exposing cells with attached virus on their surface to the fusogen polyethylene glycol, suggesting that the block to infection preceded the fusion of viral and cellular membranes. An escape mutant of HSV-1(F), designated R5000, that forms plaques on US11cl19 cells was selected. This mutant was found to contain a mutation in the glycoprotein D (gD) coding sequence that results in the substitution of the serine at position 140 in the mature protein to asparagine. A recombinant virus, designated R5001, was constructed in which the wild-type gD gene was replaced with the R5000 gD gene. The recombinant formed plaques on US11cl19 cells with an efficiency comparable to that of the escape mutant R5000, suggesting that the mutation in gD determines the ability of the mutant R5000 to grow on US11cl19 cells. The observation that the US11cl19 cells were slightly more resistant to fusion by polyethylene glycol than parental BHK(tk-) cells led to the selection and testing of clonal lines from unselected and polyethylene glycol-selected BHK(tk-) cells. The results were that 16% of unselected to as much as 36% of the clones selected for relative resistance to polyethylene glycol fusion exhibited various degrees of resistance to infection. The exact step at which the infection was blocked is not known, but the results illustrate the ease of selection of cell clones with one or more sites at which infection could be blocked.

The herpes simplex virus 1 RNA binding protein US11 is a virion component and associates with ribosomal 60S subunits

The herpes simplex virus 1 US11 gene encodes a site- and conformation-specific RNA binding regulatory protein. We fused the coding sequence of this protein with that of beta-galactosidase, expressed the chimeric gene in Escherichia coli, and purified a fusion protein which binds RNA in the same way as the infected cell protein. The fusion protein was used to generate anti-US11 monoclonal antibody. Studies with this antibody showed that US11 protein is a viral structural protein estimated to be present in 600 to 1,000 copies per virion. The great majority of cytoplasmic US11 protein was found in association with the 60S subunit of infected cell ribosomes. US11 protein associates with ribosomes both late in infection at the time of its synthesis and at the time of infection after its introduction into the cytoplasm by the virion. US11 protein expressed in an uninfected cell line stably transfected with the US11 gene associates with ribosomal 60S subunits and localizes to nucleoli, suggesting that US11 protein requires no other viral functions for these associations.

Herpes simplex virus 1 RNA-binding protein US11 negatively regulates the accumulation of a truncated viral mRNA

The US11 gene of herpes simplex virus 1 (HSV-1) encodes a site-specific, basic, RNA-binding protein. The viral RNA sequences bound by US11 protein precipitated by a monoclonal antibody hybridized to a 1.3-kb BamHI C' fragment of the HSV-1 genome. This fragment encodes a US11-regulated transcript which accumulates to high level in the cells infected with US11- virus but not in cells infected with wild-type virus. This transcript, designated delta 34, is a truncated form of the mRNA encoding an essential protein encoded by the UL34 open reading frame. The US11 protein was shown to bind delta 34 RNA at or near its 3' terminus. The nucleotide sequence of the region surrounding the termination of transcription of delta 34 RNA transcription suggests that the latter may be the product of transcriptional attenuation. US11 protein resembles the tat protein of human immunodeficiency virus with respect to size, charge, nucleolar accumulation, and possibly effect on accumulation of its target RNA but does not share with it discernible sequence homology.

The herpes simplex virus 1 gene encoding a protease also contains within its coding domain the gene encoding the more abundant substrate

The herpes simplex virus 1 open reading frames UL26 and UL26.5 are 3' coterminal. The larger, UL26 open reading frame encodes a protein approximately 80,000 in apparent molecular weight and contains the promoter and coding sequence of the UL26.5 gene, which specifies a capsid protein designated infected cell protein 35. The larger product contains in its entirety the amino acid sequence of the smaller protein. We report that the UL26 gene encodes a protease which catalyzes its own cleavage and that of the more abundant product of UL26.5. By inserting the coding sequence of an epitope to a cytomegalovirus monoclonal antibody and homologs of the immunoglobulin G binding domain of staphylococcal protein A into the 3' termini of the coding domains of the two open reading frames, we identified both products of the cleavage and determined that the cleavage site is approximately 20 amino acids from the carboxyl termini of both proteins.

Role of herpes simplex virus type 1 UL46 and UL47 in alpha TIF-mediated transcriptional induction: characterization of three viral deletion mutants

The transcriptional induction of the alpha or immediate-early gene class of herpes simplex virus type 1 effected by the alpha trans-induction factor (alpha TIF, ICP25, VP16, Vmw65) requires an alpha-specific cis-acting site. Increased transcription does not result from the direct, independent binding of alpha TIF, but rather from an alpha TIF-dependent formation of a protein-DNA complex containing, in addition to alpha TIF, at least one host cell factor. One of the host factors is a POU domain protein which recognizes an octamer element in the alpha-specific consensus. There is evidence that alpha TIF may drive the formation of multiple protein-DNA complexes containing a POU protein and additional host factors. Previously, the gene products of UL46 and UL47 have been implicated in modulating the alpha TIF-dependent transcriptional induction of alpha genes. Our current studies have extended these analyses from a transient-expression system to a series of viral deletion mutants. In these studies we demonstrate that neither UL46- nor UL47-encoded gene product, either separately or in combination, is required for viral growth in cell culture. The absence of UL47 reduces by up to 80% the ability of the virus to induce an alpha-regulated thymidine kinase reporter gene resident in 143TK- cells. Autoradiograms of [35S]methionine pulse-labeled infected cell proteins, separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, show that deleting UL46 and/or UL47 has no discernable effect on the synthesis of alpha TIF or alpha TIF-containing proteins. Subsequent Western immunoblot analysis, with rabbit anti-alpha TIF antibodies made to an alpha TIF-Staphylococcus aureus protein A fusion, demonstrated that the accumulation and steady-state levels of alpha TIF or alpha TIF-containing proteins was indistinguishable from that of the thymidine kinase-negative isogenic parental virus, R delta 305.

The promoter, transcriptional unit, and coding sequence of herpes simplex virus 1 family 35 proteins are contained within and in frame with the UL26 open reading frame

The herpes simplex virus 1 (HSV-1) genome specifies an abundant capsid protein which in denaturing gels forms multiple bands designated family 35 proteins (D.K. Braun, B. Roizman, and L. Pereira, J. Virol. 49:142-153, 1984). Nucleotide-sequencing studies have assigned the coding sequences of these proteins to the open reading frame UL26 (D.J. McGeoch, M.A. Dalrymple, A.J. Davidson, A. Dolan, M.C. Frame, D. McNab, L.J. Perry, J.E. Scott, and P. Taylor, J. Gen. Virol. 69:1531-1574, 1988). IN studies reported here, a series of plasmid constructs containing deletions or insertions of an alpha 4 promoter or of a sequence encoding a cytomegalovirus epitope reacting with a mouse monoclonal antibody revealed the following: the open reading frame previously designated UL26 encodes two proteins which share amino acid sequences, and each coding domain is contained in its own transcriptional unit that terminates at a common, unique poly(A) site. On the basis of the transcription initiation site (+1), it was predicted that the UL26 open reading frame encodes a protein of 635 amino acids, and a protein with an apparent molecular weight of approximately 75,000 has been identified. The second transcriptional unit, designated UL26.5, predicted to specify a protein of 329 amino acids, encodes the family 35 proteins; it is transcribed by an mRNA which initiates at approximately nucleotide +1000 of the UL26 transcription initiation site and is translated from the methionine initiation codon located at position +1099 of the UL26 transcriptional unit. The DNA fragment comprising the sequences downstream of the HpaI cleavage site (+832 of UL26) contains both the promoter and the coding sequence of family 35 proteins and is both competent and efficient in expressing the proteins in transfected cells superinfected with HSV-1 or HSV-2.

The herpes simplex virus Us11 open reading frame encodes a sequence-specific RNA-binding protein

Herpes simplex virus 1- and 2 (HSV-1 and HSV-2)-infected cell extracts but not uninfected cell extracts contain an RNA-binding activity for an in vitro-transcribed sequence from the domains of the HSV-1 US11 and alpha 47 genes. The transcript of this sequence has not been detected in infected cells. The binding is sequence and secondary structure specific and protects approximately 95 nucleotides from RNase digestion. Analyses of HSV-1 x HSV-2 recombinants and HSV-1 deletion mutants mapped the function necessary for activity to the US11 or alpha 47 open reading frame. The alpha 47 gene was excluded, since the RNA-binding activity is a late (gamma 2) function dependent on viral DNA synthesis for its expression. The US11 function is the only viral function required, since translation in rabbit reticulocyte lysate of an in vitro-synthesized US11 mRNA resulted in the appearance of the RNA-binding activity. The product of the US11 open reading frame is associated with the RNA probe-protein complex inasmuch as insertion of a sequence encoding in frame 15 additional amino acids at the C terminus of the US11 protein caused a corresponding decrease in the electrophoretic mobility of the binding complex.

Identification and characterization of the herpes simplex virus type 2 gene encoding the essential capsid protein ICP32/VP19c

We describe the characterization of the herpes simplex virus type 2 (HSV-2) gene encoding infected cell protein 32 (ICP32) and virion protein 19c (VP19c). We also demonstrate that the HSV-1 UL38/ORF.553 open reading frame (ORF), which has been shown to specify a viral protein essential for capsid formation (B. Pertuiset, M. Boccara, J. Cebrian, N. Berthelot, S. Chousterman, F. Puvian-Dutilleul, J. Sisman, and P. Sheldrick, J. Virol. 63: 2169-2179, 1989), must encode the cognate HSV type 1 (HSV-1) ICP32/VP19c protein. The region of the HSV-2 genome deduced to contain the gene specifying ICP32/VP19c was isolated and subcloned, and the nucleotide sequence of 2,158 base pairs of HSV-2 DNA mapping immediately upstream of the gene encoding the large subunit of the viral ribonucleotide reductase was determined. This region of the HSV-2 genome contains a large ORF capable of encoding two related 50,538- and 49,472-molecular-weight polypeptides. Direct evidence that this ORF encodes HSV-2 ICP32/VP19c was provided by immunoblotting experiments that utilized antisera directed against synthetic oligopeptides corresponding to internal portions of the predicted polypeptides encoded by the HSV-2 ORF or antisera directed against a TrpE/HSV-2 ORF fusion protein. The type-common immunoreactivity of the two antisera and comparison of the primary amino acid sequences of the predicted products of the HSV-2 ORF and the equivalent genomic region of HSV-1 provided evidence that the HSV-1 UL38 ORF encodes the HSV-1 ICP32/VP19c. Analysis of the expression of the HSV-1 and HSV-2 ICP32/VP19c cognate proteins indicated that there may be differences in their modes of synthesis. Comparison of the predicted structure of the HSV-2 ICP32/VP19c protein with the structures of related proteins encoded by other herpes viruses suggested that the internal capsid architecture of the herpes family of viruses varies substantially.

Cellular proteins specifically bind single- and double-stranded DNA and RNA from the initiation site of a transcript that crosses the origin of DNA replication of herpes simplex virus 1

The small-component origins of herpes simplex virus 1 DNA synthesis are transcribed late in infection by an RNA with heterogeneous initiation sites approximately 290-360 base pairs from the origins. We report that cellular proteins react with a labeled RNA probe representing the 5' terminus of a subset of this RNA but not with the complementary strand of this RNA. The proteins form two complexes. Complex 2 was formed by all nuclear extracts tested, whereas complex 1 was invariably formed by proteins present only in nuclear extracts of mock-infected cells. Complex 1 protects a contiguous stretch of 40 nucleotides of the labeled RNA probe from nuclease degradation. Formation of complex 1 was competitively inhibited in a sequence-specific fashion by single-stranded RNA and DNA and by double-stranded RNA and DNA. The protein(s) forming complex 1 is, thus, quite distinct from known nucleic acid-binding proteins in that they recognize a specific nucleotide sequence, irrespective of the nature (single- and double-stranded RNA and DNA) of the nucleic acid. We conclude the following: (i) the proteins forming complex 1 and 2 are probably different, (ii) complex 1 is neither required throughout infection for viral replication nor able to hinder viral replication in cells in culture, and (iii) cells susceptible to infection encode one or more proteins that recognize specific sequences in single-stranded nucleic acids; either these proteins impart a compatible conformation on single-stranded nucleic acids with the conformation of the same strand in the double-stranded nucleic acid, or these proteins confer a specific, distinct conformation to both single-stranded and double-stranded nucleic acids.

Delineation of regulatory domains of early (beta) and late (gamma 2) genes by construction of chimeric genes expressed in herpes simplex virus 1 genomes

The expression of the gamma 2 class of viral genes in cells infected with herpes simplex virus 1 requires viral DNA synthesis and functional viral products made earlier in infection. To identify the sequences required for gamma 2 gene expression, we constructed recombinant viruses in which regions of the thymidine kinase gene (tk), a beta gene normally expressed early in infection, were replaced by specific domains of a gamma 2 gene. The phenotypic attributes examined were (i) sensitivity or resistance of expression in cells exposed to sufficient phosphonoacetate to block viral DNA synthesis, properties of gamma 2 and beta genes, respectively; (ii) expression early in infection, a property of beta genes; and (iii) expression late in infection, a property of gamma 2 genes. We report that replacement of nucleotides -200 to +51 of tk with nucleotides -77 to +104 of the gamma 2 gene conferred upon tk all of the tested attributes of gamma 2 genes. The tk sequence in the 5' transcribed noncoding domain downstream of nucleotide +51 played no apparent role in the expression of the chimeric genes. Similarly, tk sequence downstream of -16 and gamma 2 sequence upstream of -12, when juxtaposed in correct orientations, yielded a chimeric gene that was poorly expressed. In contrast, the chimeric gene consisting of tk sequence upstream of -16 fused to gamma 2 sequence downstream of -12 had the attributes of both beta and gamma 2 genes in that it was expressed both early and late in infection and was partially resistant to phosphonoacetate. The capacity for expression late in infection encoded in the gamma 2 5' transcribed noncoding domain was observed in cells infected with a recombinant virus in which gamma 2 nucleotides +17 to +104 were inserted into the 5' transcribed noncoding domain of the tk gene. We conclude that whereas in the beta genes exemplified by the tk gene the regulatory domains are mainly upstream from nucleotide +51, the sequence(s) that confers gamma 2 regulation is downstream from the TATAA box.

Characterization of major recognition sequences for a herpes simplex virus type 1 origin-binding protein

To investigate early initiation events in the replication of herpes simplex virus type 1, we analyzed interactions of proteins from infected cell extracts with the small origin of herpes simplex virus type 1 (oris1). Using the mobility shift assay, we detected two origin-specific binding interactions. We characterized the more prominent interaction on both strands of the DNA duplex with DNase I protection and methylation interference assays. Protein binding protects 17 bases of DNA on each strand from DNase I. These sequences are located at the left end of the central palindrome and are shifted four bases relative to one another. On the basis of the DNase protection pattern, we believe this protein to be related to the origin-binding protein defined by Elias et al. (P. Elias, M.E. O'Donnell, E.S. Mocarski, and I.R. Lehman, Proc. Natl. Acad. Sci. 83:6322-6326, 1986). Our DNase I footprint shows both strong and weak areas of protection. The regions strongly protected from DNase I align with the essential contact residues identified by interference footprinting. Methylation interference defines a small binding domain of 8 base pairs: 5'-GTTCGCAC-3'/3'-CAAGCGTG-5'. This recognition sequence contains two inverted 5'-GT(T/G)CG-3' repeats which share a 2-base overlap; thus, the origin-binding protein probably binds to the inverted repeats as a dimer.

Activation of herpes simplex virus 1 gamma 2 genes by viral DNA replication

The expression of gamma 2 or true gamma genes resident in the herpes simplex virus 1 genome requires functional products of genes expressed earlier in infection and viral DNA synthesis. To determine whether the requirement for viral DNA synthesis for the expression of gamma 2 genes reflects a trans-acting function of a product of one or a few genes made or activated during viral DNA synthesis or whether it reflects a cis effect of DNA synthesis at specific sites, 143 thymidine kinase (TK) minus cells were sequentially infected with a virus carrying a 700-bp deletion of the TK gene and 6 hr later with wild-type or recombinant viruses carrying an alpha-TK or a gamma 2-TK gene in either the presence or absence of viral DNA synthesis. These experiments indicated that the gamma 2-TK gene contained in an unreplicated viral genome was not expressed by trans-acting factors specified before and during DNA synthesis by the first infecting virus, and, therefore, the induction of gamma 2 genes appears to be mediated by a cis-acting function associated with viral DNA synthesis.

The herpes simplex virus origins of DNA synthesis in the S component are each contained in a transcribed open reading frame

In the herpes simplex virus 1 genome, the origins of viral DNA synthesis are located in the unique sequences of the L component (Oril) and in the reiterated sequences of the S component (OriS) located between the 5' terminus of the alpha 4 gene and the 5' terminus of either the alpha 22 (left terminus of the S component) or the alpha 47 (right terminus of the S component) gene. Studies prompted by the finding that only one, but not both, OriS sequence is dispensable for growth in cell culture indicate that each OriS sequence is contained in an open reading frame designated as OriSORF. The transcription of OriSORF is initiated approximately 860 nucleotides upstream from that of the alpha 4 gene and 162 nucleotides downstream, but on the opposite strand from the transcription initiation site of the alpha 22 or alpha 47 genes within the inverted repeat c sequence. The OriSORF transcript is 3' coterminal with the mRNA of the alpha 4 gene, polyadenylated but not spliced, transported into the cytoplasm, and capable of directing the synthesis of a 330-amino-acid protein with a translated molecular weight of approximately 34,000. Transcription is cycloheximide but not phosphonoacetate sensitive and is therefore regulated as either a beta or a gamma 1 gene. The implications of the transcription of OriS and of possible functions of the product of OriSORF are discussed.

Effects of herpes simplex virus on mRNA stability

Herpes simplex virus virions contain one or more functions which mediate shutoff of host protein synthesis, disaggregation of host polyribosomes, and degradation of host mRNA. We studied aspects of the host shutoff mechanism by using herpes simplex virus type 1 mutants deficient in virion-induced shutoff of host protein synthesis (G. S. Read and N. Frenkel, J. Virol. 46:498-512, 1983). Shutoff of host protein synthesis by the wild-type virus was associated with degradation of host mRNAs, including beta-actin, alpha-tubulin, and heat shock protein 70. In contrast, the virion host shutoff (vhs) mutants were deficient to various degrees in their ability to induce host mRNA degradation; the extent of mRNA degradation correlated well with the extent of inhibition of host protein synthesis. This finding suggests that inhibition of host protein synthesis and degradation of host mRNA were mediated by the same virion-associated function. Virion-induced degradation of host mRNA was not prevented by inhibitors of ribosome translocation, nor could it be augmented, for mutant vhs-1, by drugs which disaggregate polyribosomes. This suggests that mRNA in polyribosomes, as well as nonpolyribosomal mRNA, is susceptible to virion-induced degradation. Finally, the half-life of viral transcripts was also prolonged in cells infected with the vhs-1 mutant virus, suggesting that the vhs function indiscriminately decreased the half-lives of both host and viral mRNAs. The vhs function may thus play a dual role in virus infection. (i) It inhibits host gene expression, and (ii) it enables rapid transitions in the expression of viral genes which are sequentially transcribed as infection progresses.

Herpes simplex virus-infected cells contain a function(s) that destabilizes both host and viral mRNAs

The herpes simplex virus virion contains a function that mediates the shutoff of host-protein synthesis and the degradation of host mRNA. Viral mutants affected in this function (vhs mutants) have previously been derived. Cells infected with these mutants exhibit a more stable synthesis of host as well as the immediate early (alpha)-viral proteins. We now show that a function associated with purified virions of the wild-type virus reduces the half-life of host and alpha mRNAs, whereas purified vhs-1 mutant virions lack this activity. The functional half-life of many early (beta)- and late (gamma)-viral mRNAs is also prolonged in mutant virus infections. These studies suggest that the wild-type virion brings into cells a function that indiscriminately reduces the half-life of both host and viral transcripts and that the early translational shutoff of the host is a consequence of this function. This function may facilitate rapid transitions in the expression of groups of genes that are transcriptionally turned on at different times after infection.

Construction and properties of a viable herpes simplex virus 1 recombinant lacking coding sequences of the alpha 47 gene

The five alpha genes, alpha 0, alpha 4, alpha 22, alpha 27, and alpha 47, are the first set of herpes simplex virus 1 genes to be transcribed and expressed in productively infected cells. We report here the construction of a viral recombinant from which all of the coding sequences of the alpha 47 gene were deleted. In addition to the alpha 47 protein, infected cell lysates did not contain detectable amounts of two polypeptide bands with apparent molecular weights of 18,000 and 21,000 which could be specified by a gene whose regulatory domain and 5' transcribed noncoding sequences overlap with the coding sequences of the alpha 47 gene. The alpha 47- virus grew as well as the wild-type parent virus in Vero, baby hamster kidney, and Rat-1 cell lines.

gamma 2-Thymidine kinase chimeras are identically transcribed but regulated a gamma 2 genes in herpes simplex virus genomes and as beta genes in cell genomes

True gamma or gamma 2 genes, unlike alpha, beta, and gamma 1 (beta gamma) genes of herpes simplex virus 1 (HSV-1), stringently require viral DNA synthesis for their expression. We report that gamma 2 genes resident in cells were induced in trans by infection with HSV-1 but that the induction did not require amplification of either the resident gene or the infecting viral genome. Specifically, to test the hypothesis that expression of these genes is amplification dependent, we constructed two sets of gamma 2-thymidine kinase (TK) chimeric genes. The first (pRB3038) consisted of the promoter-regulatory region and a portion of 5'-transcribed noncoding region of the domain of a gamma 2 gene identified by Hall et al. (J. Virol. 43:594-607) in the HSV-1(F) BamHI fragment D' to the 5'-transcribed noncoding and coding regions of the TK gene. The second (pRB3048) contained, in addition, an origin of HSV-1 DNA replication. Cells transfected with either the first or second construct and selected for the TK+ phenotype were then tested for TK induction after superinfection with HSV-1(F) delta 305, containing a deletion in the coding sequences of the TK gene, and viruses containing, in addition, a ts lesion in the alpha 4 regulatory protein (ts502 delta 305) or in the beta 8 major DNA-binding protein (tsHA1 delta 305). The results were as follows: induction by infection with TK- virus of chimeric TK genes with or without an origin of DNA replication was dependent on functional alpha 4 protein but not on viral DNA synthesis; the resident chimeric gene in cells selected for G418 (neomycin) resistance was regulated in the same fashion; the chimeric gene recombined into the viral DNA was regulated as a gamma 2 gene in that its expression in infected cells was dependent on viral DNA synthesis; the gamma 2-chimeric genes resident in the host and in viral genomes were transcribed from the donor BamHI fragment D' containing the promoter-regulatory domain of the gamma 2 gene. The significance of the differential regulation of gamma 2 genes in the environments of host and viral genomes by viral trans-acting factors is discussed.

Analysis of HSV isolated from patients with unilateral and bilateral herpetic keratitis

Restriction enzyme analysis was utilized to investigate 11 HSV isolates from patients with herpetic keratitis. The electrophoretic profiles of the DNAs indicate that the isolates belong to HSV-1 and are epidemiologically unrelated. Two of the isolates, derived from a patient with simultaneous bilateral herpetic keratitis were further characterized by genetic and phenotypic analyses. These studies showed the following: (i) the two recrudescent lesions were caused by the same HSV-1 isolate; (ii) the isolate yielded two different plaque phenotypes; (iii) these plaques showed different sensitivity to I.D.U.

gamma 2-Thymidine kinase chimeras are identically transcribed but regulated a gamma 2 genes in herpes simplex virus genomes and as beta genes in cell genomes

True gamma or gamma 2 genes, unlike alpha, beta, and gamma 1 (beta gamma) genes of herpes simplex virus 1 (HSV-1), stringently require viral DNA synthesis for their expression. We report that gamma 2 genes resident in cells were induced in trans by infection with HSV-1 but that the induction did not require amplification of either the resident gene or the infecting viral genome. Specifically, to test the hypothesis that expression of these genes is amplification dependent, we constructed two sets of gamma 2-thymidine kinase (TK) chimeric genes. The first (pRB3038) consisted of the promoter-regulatory region and a portion of 5'-transcribed noncoding region of the domain of a gamma 2 gene identified by Hall et al. (J. Virol. 43:594-607) in the HSV-1(F) BamHI fragment D' to the 5'-transcribed noncoding and coding regions of the TK gene. The second (pRB3048) contained, in addition, an origin of HSV-1 DNA replication. Cells transfected with either the first or second construct and selected for the TK+ phenotype were then tested for TK induction after superinfection with HSV-1(F) delta 305, containing a deletion in the coding sequences of the TK gene, and viruses containing, in addition, a ts lesion in the alpha 4 regulatory protein (ts502 delta 305) or in the beta 8 major DNA-binding protein (tsHA1 delta 305). The results were as follows: induction by infection with TK- virus of chimeric TK genes with or without an origin of DNA replication was dependent on functional alpha 4 protein but not on viral DNA synthesis; the resident chimeric gene in cells selected for G418 (neomycin) resistance was regulated in the same fashion; the chimeric gene recombined into the viral DNA was regulated as a gamma 2 gene in that its expression in infected cells was dependent on viral DNA synthesis; the gamma 2-chimeric genes resident in the host and in viral genomes were transcribed from the donor BamHI fragment D' containing the promoter-regulatory domain of the gamma 2 gene. The significance of the differential regulation of gamma 2 genes in the environments of host and viral genomes by viral trans-acting factors is discussed.

A noninverting genome of a viable herpes simplex virus 1: presence of head-to-tail linkages in packaged genomes and requirements for circularization after infection

The wild-type herpes simplex virus 1 genome consists of two components, L and S, which invert relative to each other, giving rise to four isomers. Previously we reported the construction of a herpes simplex virus 1 genome, HSV-1(F)I358, from which 15 kilobase pairs of DNA spanning the junction between L and S components were deleted and which no longer inverted (Poffenberger et al., Proc. Natl. Acad. Sci. U.S.A. 80:2690-2694, 1983). Further studies on the structure of HSV-1(F)I358 revealed the presence of two submolar populations among packaged DNA. The first, comprising no more than 10% of total packaged DNA, consisted of defective genomes with a subunit size of 36 kilobase pairs. The results suggest that this population arose by recombination through a directly repeated sequence inserted in place of the deleted L-S junction. The second minor population consisted of HSV-1(F)I358 DNA linked head-to-tail. Analyses of the structure of HSV-1(F)I358 DNA after infection indicated that the fraction of total DNA linked head-to-tail increased to approximately 40 to 50% within 30 min after exposure of cells to virus. The formation of head-to-tail linkages did not require de novo protein synthesis. Our interpretation of the results is that the termini of full-length DNA molecules are held together during packaging, that a small fraction of the termini is covalently linked during or after packaging, and that the remainder is covalently joined after the release of viral DNA from the infecting virus by either host or viral factors introduced into the cell during infection.

A post-alpha gene function turns off the capacity of a host protein to bind DNA in cells infected with herpes simplex virus 1

HEp-2 cell proteins electrophoretically separated in denaturing polyacrylamide gels and electrically transferred to nitrocellulose sheets contain a polypeptide which efficiently binds linear native DNA end labeled with 32P but not denatured DNA. The polypeptide has an apparent molecular weight of ca. 130,000. The activity of the protein was stable, and no appreciable turnover was observed after exposure of uninfected cells to inhibitory concentrations of cycloheximide for intervals of up to 24 h. However, the activity was absent from lysates of cells harvested 6 h or later postinfection with wild-type viruses. To identify the viral function involved in the loss of DNA-binding activity, we tested the lysates of cells infected with several mutants. Thus, the DNA-binding activity was unaffected in cells infected with a temperature-sensitive mutant (herpes simplex virus 1 tsLB2) in the alpha 4 gene and was maintained at a nonpermissive temperature (39 degrees C). Experiments involving (i) temperature shift-down of cells infected with tsLB2 in the presence of cycloheximide, (ii) withdrawal of cycloheximide in the presence and absence of actinomycin D from cells infected with wild-type virus, (iii) infection of cells at 33 and 39 degrees C with herpes simplex virus 1 tsHA1 carrying a temperature-sensitive lesion in the beta 8 gene, and (iv) infection of cells in the presence of inhibitory concentrations of phosphonoacetate led to the conclusion that the viral functions responsible for the loss of DNA-binding capacity were specified by either beta or gamma genes not dependent on viral DNA synthesis for their expression.

Neurotransmitter synthesizing enzymes in experimental viral encephalitis

Stereotactic intracerebral inoculation of a non-neuroadapted strain of herpes simplex virus type 1 into the left neostriatum of Sprague-Dawley rats induced clinical acute encephalitis within 3 to 5 days postinoculation, with microscopic evidence of inflammation in brain parenchyma, but with no gross areas of tissue destruction. Viral presence in brain was unequivocally confirmed by tissue culture, immunofluorescence and electron microscopy. Levels of activity of neurotransmitter synthesizing enzymes tyrosine hydroxylase (TH), glutamate decarboxylase (GAD), and choline acetyltransferase (ChAT) in the substantia nigra, caudate-putamen and frontal cortex of acutely encephalitic animals were not significantly different from those of PBS-inoculated controls; neither were there significant differences between the inoculated and non-inoculated sides of the individual animals. Our results show that locally injected herpes simplex virus may spread in brain causing neurological symptoms and death without major local structural changes or loss of neurotransmitter synthesizing enzymes. The degree and distribution of cell dysfunction and cell loss in viral encephalitis basically determine any alterations of enzyme activities specific to the involved cell population. The literature on neurotransmitter enzymes and experimental viral encephalitis is reviewed.

Characterization of the herpes simplex virion-associated factor responsible for the induction of alpha genes

Herpes simplex virus (HSV) genes form three groups, alpha, beta, and gamma, whose synthesis is coordinately regulated and sequentially ordered in a cascade fashion. Earlier studies by Post et al. (Cell 24:555-565, 1981) have shown that chimeric genes constructed by fusion of 5' noncoding leader and upstream sequences of alpha genes to the 5' noncoding leader and structural sequences of the viral thymidine kinase (TK), a beta gene, are regulated as alpha genes upon recombination into the viral genome. In cells converted from TK- to TK+ phenotype, these chimeric genes are induced by infection with homologous TK- virus. The induction of the resident chimeric gene does not require viral protein synthesis and is independent of the presence of functional alpha gene 4 product required for the expression of beta genes. In this paper, we report on the properties of the alpha-TK gene chimera resident in converted TK+ murine (L316) and human (I316) cells. Our results were as follows. (i) The pattern of induction of L316 cells exposed to 0.1, 1.0, and 10 PFU per cell suggested that exposure to competent virus is required for induction and that in untreated preparations this virus corresponds to infectious virus. (ii) UV light-irradiated virus was just as effective as untreated virus in inducing alpha-TK chimeras. (iii) HSV-1(HFEM)tsB7 induced the alpha-TK gene chimeras at the nonpermissive (39 degrees C) temperature; at 39 degrees C the parental HSV-1(HFEM)tsB7 capsids accumulate at nuclear pores and do not release viral DNA. (iv) The alpha-TK gene chimeras were not induced by infection with spontaneous TK- mutants of pseudorabies virus and bovine mammillitis virus or with human cytomegalovirus or adenovirus type 2 or by exposure to lysates of HSV-1-infected cells from which the virus was removed by centrifugation. These results indicate that the alpha gene inducer is a virion component located outside the capsid and that its function might be to stimulate the transcription of alpha genes by recognizing regulatory sites on viral DNAs or host cell products or both.

Inhibition of herpes simplex virus DNA synthesis by pokeweed antiviral protein

Pokeweed antiviral protein at a concentration of 3 microM inhibited both the synthesis and release of infectious herpes simplex virus type 1 in cell culture by 90 and 99%, respectively. Addition of pokeweed antiviral protein to Vero cell monolayers before virus infection was 10 to 15% more effective in reducing virus yields than was the simultaneous addition of the antiviral protein with virus inoculum. Viral DNA synthesis was inhibited by 90% in cells which had been exposed to the antiviral protein, whereas cellular DNA synthesis was unaffected. No significant inhibition in the synthesis of the majority of viral infected-cell polypeptides was observed early postinfection (7 h), with the exception of infected cell polypeptides 4 and 41, whose syntheses were reduced by 38 and 25%, respectively. At 9 to 21 h postinfection, however, the synthesis of individual infected cell polypeptides was reduced by 48 to greater than 99%.

Simplified method for typing herpes simplex virus by restriction endonuclease analysis

We have developed a simplified method for unambiguously typing herpes simplex virus. The method depends on the production of cell-associated virus at 34 degrees C and subsequently, on the separation of cellular DNA and viral DNA by Dounce homogenization and the removal of nuclei by centrifugation. Viral nucleic acid was prepared from the cytoplasmic fraction and analyzed after restriction endonuclease cleavage. The method obviates the use of radioactive isotopes, and the viral DNA is effectively free of interfering cellular DNA.

Molecular genetics of herpes simplex virus. VIII. further characterization of a temperature-sensitive mutant defective in release of viral DNA and in other stages of the viral reproductive cycle

Previous studies have shown that cells infected with the herpes simplex virus 1(HFEM) mutant tsB7 and maintained at the nonpermissive temperature fail to accumulate viral polypeptides. Analyses of intertypic recombinants generated by marker rescue of tsB7 with herpes simplex virus 2 DNA fragments localized the mutation between 0.46 and 0.52 map units on the viral genome (Knipe et al., J. Virol. 38:539-547, 1981). In this paper we report that the mutation in tsB7 affects several aspects of the reproductive cycle of the virus at the nonpermissive temperature. Thus, (i) viral capsids accumulate at the nuclear pores and do not release viral DNA for at least 6 h postinfection at 39 degrees C. The DNA was released within 30 min after a shift to the permissive temperature. (ii) Experiments involving shifts from the permissive to the nonpermissive temperature indicated that viral protein synthesis was not sustained in cells maintained at the permissive temperature for less than 4 h. (iii) Viral DNA synthesis was delayed at the permissive temperature for as long as 8 h. Once initiated, it continued at 39 degrees C. (iv) Marker rescue of tsB7 by transfection with herpes simplex virus 1(F) DNA fragments localized the mutation to between 0.501 and 0.503 map units on the viral genome. These results are consistent with the tsB7 lesion being in a gene coding for a virion component which affects release of viral DNA from capsids and onset of viral DNA synthesis.

Structural features of the herpes simplex virus alpha gene 4, 0, and 27 promoter-regulatory sequences which confer alpha regulation on chimeric thymidine kinase genes

Previous studies have shown that herpes simplex virus genes form three groups, alpha, beta, and gamma, whose expression is coordinately regulated and sequentially ordered in a cascade fashion. Chimeric genes constructed by fusion of the coding and 5' nontranslated leader sequences of the thymidine kinase (TK) gene to the sequences upstream from the site of initiation of transcription of alpha genes 4 and 27 are regulated as alpha genes and are induced in cells converted to TK+ phenotype by infection with TK- virus. In alpha gene 4 (S. Mackem and B. Roizman, Proc. Natl. Acad. Sci. U.S.A. 79:4917-4921, 1982), both the promoter and the regulatory region are separable and movable. The promoter permits expression but not induction when fused to TK in the noncoding leader region of the gene. The regulator, when fused to the promoter of an expressible but noninducible portion of the natural beta TK, renders the gene inducible as an alpha gene; it consists of multiple regulatory units acting cumulatively. In this paper, we report on the precise site of initiation of transcription of alpha gene 0 within the inverted b sequences of the L component of viral DNA. We also report the following. (i) The chimeric gene consisting of the coding and 5' nontranslated leader regions of the TK gene fused to portions of the domain of alpha gene 0 extending largely upstream from the site of initiation of transcription of alpha gene 0 was regulated in the same fashion as the alpha 4- and alpha 27-TK chimeras. The regulatory region in the alpha gene 0 is largely upstream from nucleotide - 140. (ii) The promoter-regulatory regions of alpha genes 0, 4, and 27 share TATA sequences, A + T-rich (consensus) sequences occurring in regulating regions of alpha genes 0 and 4 in more than one copy, and multiple G + C-rich inverted repeats. The relation of these sequences to the function of the promoter-regulatory regions of the alpha genes is discussed.

Regulation of alpha genes of herpes simplex virus: the alpha 27 gene promoter-thymidine kinase chimera is positively regulated in converted L cells

In cells infected with herpes simplex virus 1, the expression of viral genes is coordinately regulated and sequentially ordered; the alpha genes are expressed first and are followed by beta and gamma genes in a cascade fashion. Earlier, this laboratory reported (Post et al., Cell 24:555-565, 1981) that a chimeric gene, constructed by the replacement of 50 base pairs of DNA coding for 5' nontranslated leader and sequences upstream of the site of transcription initiation of thymidine kinase (a beta gene) by corresponding sequences of alpha gene no. 4, was regulated as an alpha gene. Of particular interest was the observation that in cells converted to TK(+) phenotype, the chimeric gene was positively regulated by superinfecting virus. In this paper, we report two series of experiments. First, we determined that transcription of alpha gene no. 27 is initiated at or near a five-nucleotide sequence flanked by an eight-nucleotide perfect inverted repeat situated from 256 to 277 bases to the right of the left terminus of the BamHI B fragment. In the second series of experiments, we constructed a chimeric gene which consisted of the thymidine kinase sequences described above but was fused to a DNA fragment expected to contain the promoter-regulatory region of alpha gene 27 and stretching from approximately -270 to the +55 nucleotide. The chimeric gene in converted cells was amplified upon superinfection with TK(-) virus only when the promoter-regulatory region was in the correct transcriptional orientation relative to the leader and structural sequences of the thymidine kinase gene. The requirements for amplification of the expression of this chimeric thymidine kinase gene were exactly the same as those previously reported for the alpha gene no. 4-thymidine kinase chimera and different from those of the standard (beta) thymidine kinase. We conclude that the positive regulation of expression of alpha gene no. 4 deduced in previous studies may be a general property of alpha genes and that the promoter-regulatory region of alpha gene no. 27 is within a sequence contained between -270 and +55 nucleotides relative to the transcription initiation site.

Differential immunologic reactivity and processing of glycoproteins gA and gB of herpes simplex virus types 1 and 2 made in Vero and HEp-2 cells

Herpes simplex virus types 1 and 2 (HSV-1 and HSV-2, respectively) specify five major glycoproteins designated as gA, gB, gC, gD, and gE. Previous studies have shown that gA and gB differ in electrophoretic mobility but not in reactivity with antisera prepared to each of these glycoproteins. Moreover, gA and gB of HSV-1 crossreact in serologic tests with the corresponding glycoproteins of HSV-2. In this paper, we report on the reactivities of gA and gB of HSV-1 and HSV-2 with 24 independently derived monoclonal antibodies reactive with these antigens. Our results show the following: (i) Electrophoretic mobilities of HSV-1 and HSV-2 glycoproteins gA and gB made in HEp-2 cells are significantly less than those made in Vero cells. (ii) All monoclonal antibodies precipitated both gA and gB made in infected HEp-2 cells. These include 12 monoclonal antibodies that neutralized virus and 12 that did not. (iii) HSV-2 glycoproteins gA and gB made in HEp-2 cells contain type-specific domains. However, monoclonal antibodies produced by one clone directed to these domains did not react with glycoproteins made in Vero cells. (iv) Lysates of infected Vero cells contain three lower molecular weight polypeptides that also reacted with monoclonal antibodies directed to glycoproteins gA and gB. These polypeptides are virus specific inasmuch as those specified by HSV-1 differ in electrophoretic mobilities from those specified by HSV-2. these polypeptides are absent in lysates of HEp-2 cells.

Molecular genetics of herpes simplex virus. VII. Characterization of a temperature-sensitive mutant produced by in vitro mutagenesis and defective in DNA synthesis and accumulation of gamma polypeptides

We report on the properties of a temperature-sensitive mutant produced by transfection of cells with intact DNA and a specific DNA fragment mutagenized with low levels of hydroxylamine. The plating efficiency of the mutant at 39 degrees C relative to that at 33.5 degrees C was 5 X 10(-6). The pattern of polypeptides produced at the nonpermissive temperature was similar to that seen with wild-type virus in infected cells treated with inhibitory concentrations of phosphonoacetic acid in that alpha and beta polypeptides were produced, whereas most gamma polypeptides were either reduced or absent. Consistently, the mutant did not make viral DNA, although temperature sensitivity of the viral DNA polymerase could not be demonstrated. Marker rescue studies with herpes simplex virus type 2 (HSV-2) DNA mapped the mutant in the L component within map positions 0.385 and 0.402 in the prototype (P) arrangement of the HSV-1 genome. Analysis of the recombinants permitted the mapping of the genes specifying infected cell polypeptides 36, 35, 37, 19.5, 11, 8, 2, 43, and 44, but only the infected cell polypeptide 8 of HSV-2 was consistently made by all recombinants containing demonstrable HSV-2 sequences. Marker rescue studies with cloned HSV-1 DNA fragments mapped the temperature-sensitive lesion within less than 10(3) base pairs between 0.383 and 0.388 map units. Translation of the RNA hybridizing to cloned HSV-1 DNA, encompassing the smallest region containing the mutation, revealed polypeptide 8 (128,000 molecular weight), which was previously identified as a beta polypeptide with high affinity for viral DNA, and a polypeptide (25,000 molecular weight) not previously identified in lysates of labeled cells.

Factors governing expression of the herpes simplex virus gene for thymidine kinase in clonal derivatives of transformed mouse L cells

The cells used in this study are sublines of a transformed mouse L cell line (designated H2) that carries the herpes simplex virus (HSV) gene for thymidine kinase (tk) as well as other viral genetic information acquired after exposure of the parental Ltk(-) cells to UV-irradiated HSV type 1. These sublines of the H2 cell line were isolated by cloning under nonselective conditions and were shown to express widely different levels of viral tk. Selective media were used to isolate phenotypically tk(-) and tk(+) variants in sequence from one of the clonal derivatives. As previously reported, superinfection of the tk(+) cell lines with tk(-) HSV type 1 resulted in enhancement of tk activity. A new finding was that viral tk activity could be induced by superinfection in at least 30% of cells from the phenotypically tk(-) sublines, indicating that a functional viral tk gene was retained in a significant proportion of the cells. Experiments were designed to test for the presence of regulatory factors that could influence tk expression in the nonsuperinfected sublines of H2. Absence of freely diffusible regulatory factors was indicated by the finding that the fusion of phenotypically tk(-) and tk(+) cells and untransformed cells in appropriate combinations did not affect the levels of tk detected. Moreover, there was no evidence for the presence in phenotypically tk(+) transformed cells of HSV-specific regulatory factors that could influence expression of tk from a superinfecting viral genome. Phenotypically tk(+) sublines of H2 were found to differ from the phenotypically tk(-) sublines and from untransformed cells in that the tk(+) cells synthesized viral proteins earlier and produced greater yields of infectious HSV progeny after superinfection with wild-type tk(+) virus. We can conclude that the absence of tk expression in the tk(-) H2 sublines cannot be accounted for by rearrangements or loss of DNA sequences encoding the enzyme itself or of sequences necessary for induction of the gene by superinfecting HSV. Moreover, it appears that the expression of tk in the tk(+) H2 sublines correlates with the presence of some factor that can enhance (or the absence of some factor that can depress) HSV replication and gene expression.

Molecular engineering of the herpes simplex virus genome: insertion of a second L-S junction into the genome causes additional genome inversions

We have developed a technique for the insertion of any DNA fragment into the herpes simplex virus (HSV) genome at specific sites. This technique was used to resolve a specific problem concerning the isomerization of the HSV genome. Briefly, HSV DNA consists of four isomers differing in the orientation of two covalently linked components, L and S, relative to each other. Each component consists of unique sequences flanked by inverted repeats. To determine whether the isomerization of HSV DNA is the result of generalized recombinatin between homologous reiterated sequences in the inverted repeats or the result of site-specific recombination, we constructed plasmids in which DNA fragments derived from various regions of the viral genome were inserted in both orientations into the thymidine kinase gene, rendering it nonfunctional. The HSV DNA sequences in the plasmids were then recombined into the viral genome, and viral recombinants were selected for their thymidine kinase-deficient phenotype. The insertion of these fragments by homologous recombination was highly efficient in that all the viral clones isolated contained the inserted fragment at the expected location. The only fragments that promoted additional inversions of the viral genome were those spanning the junction between the L and S components. Furthermore, analysis of isomers formed by these recombinants indicates that the inversions occur only when sequences in the inserted fragment are in inverted orientation in relation to homologous sequences at the termini or at the authentic junction.

Cloning of reiterated and nonreiterated herpes simplex virus 1 sequences as BamHI fragments

Over 95% of the herpes simplex virus type 1 (strain F) DNA sequences have been cloned as BamHI fragments in the pBR322 plasmid. With one exception, all of the cloned fragments have the same electrophoretic mobilities and restriction enzyme cleavage sites as do the authentic fragments derived from the BamHI digests of the viral genome. The exception is the BamHI B fragment mapping at the right end of L component in the prototype arrangement of the DNA. Thus, a small deletion mapping near the left end of the fragment was present in two independently derived plasmids. Included in the collection of plasmids are several clones containing DNA sequences that span the junction between the L and S components of the virus DNA. Several plasmids containing the junction fragment were found to be sufficiently stable to permit the preparation of large amounts of the DNA fragment for fine-structure mapping of the restriction enzyme cleavage sites. Preliminary studies on one cloned fragment (BamHI G) have shown that it is biologically active in marker rescue of a temperature-sensitive mutation and in transfer of a plaque morphology marker.

Comparative analysis of the virion polypeptides specified by herpes simplex virus type 2 strains

This paper reports on the variability of structural polypeptides of 32 strains of Herpes simplex virus 2 (HSV-2) isolated from various locations in the United States and Italy. Most strains were passaged a limited number of times at low multiplicity outside the human host; a few strains were characterized by numerous passages at variable multiplicities in cell culture. The acrylamide gel electrophoresis of polypeptides from purified virions revealed very few differences. Considering these differences the HSV-2 strains analysed can be classified into 3 groups according to the variability of three polypeptides. The study of polypeptides in HSV-2 infected cells revealed more differences than those seen in the structural proteins. Comparisons of the structural proteins specified by HSV-2 and HSV-1 virions, revealed clear variant features of the electrophoretic profiles, especially when pH of main gel was 8.9.

Regulation of herpesvirus macromolecular synthesis. VIII. The transcription program consists of three phases during which both extent of transcription and accumulation of RNA in the cytoplasm are regulated

This report concerns the stable viral RNA sequences that accumulate in HEp-2 cells infected with herpes simplex virus type 1. By hybridizing labeled total DNA and restriction endonuclease DNA fragments with excess unlabeled total nuclear and cytoplasmic RNA, we determined the genetic complexity of the RNA and we mapped the regions on the physical map of herpes simplex virus type 1 DNA that are homologous to the RNA. Our results show the following. (i) The viral RNAs accumulating in the nucleus and cytoplasm of cells infected and maintained in the presence of inhibitory concentrations of either cycloheximide or emetine were homologous to 33 and 12% of viral DNA, respectively. All of the fragments tested contained sequences homologous to nuclear RNA. However, only the fragments mapping between 0.00 and 0.18, and 0.53 and 1.00 map units contained sequences homologous to cytoplasmic RNA. (ii) The viral RNAs that accumulate in the nucleus and cytoplasm of cells infected and maintained in the presence of inhibitory concentrations of phoaphonoacetic acid were homologous to 39 and 26% of viral DNA, respectively. In this instance all of the fragments except those mapping between 0.42 and 0.53 map units contained sequences homologous to cytoplasmic RNA. (iii) The viral RNAs that accumulate in the nucleus and cytoplasm 8 h after infection were homologous to greater than 50 and 41%, respectively. All of the fragments tested contained sequences homologous to cytoplasmic RNA. (iv) The viral RNAs that accumulate in the nucleus and cytoplasm of cells infected and maintained in the presence of canavanine are homologous to 33 and 19% of viral DNA, respectively. All of the fragments tested contained sequences homologous to both nuclear and cytoplasmic RNAs. Our results indicate the following. First, there are at least three phases of transcription of viral DNA. Phase 1 does not require the synthesis of host cell or viral proteins. Phase 2 requires the synthesis of viral proteins made before the initiation of viral DNA synthesis. Phase 3 appears to be related to the initiation of viral DNA synthesis. Second, both the extent of transcription and the accumulation of viral RNA in the cytoplasm are tightly regulated. The genetic complexity of total RNA accumulating in infected cells increased in each successive phase. Moreover, the genetic complexity of nuclear RNA was invariably higher than that of cytoplasmic RNA in each phase. Lastly, the results of the studies on viral RNA accumulating in canavanine-treated cells reinforce the hypothesis made previously that more than one polypeptide in each of the alpha and beta polypeptide groups is involved in the transcription preceding the transitions from alpha to beta and beta to gamma polypeptide synthesis, respectively, and that canavanine selectively inactivated subsets of these polypeptides permitting only partial transitions from alpha to beta and beta to gamma to occur.

Influence of genetic and physiological properties of the host cell on the cytopathic expression of herpes simplex virus

Two plaque morphology variants, a cell aggregating variant and a syncytial variant, were isolated from MDBK cells infected with the MP mutant of herpes simplex virus, type 1. The variants differed in the polypeptides produced in infected MDBK cells. The properties of the variants were stable on passage in cells and both variants produced only syncytia in KB and Hep-2 cells. The physiological state of MDBK cells influenced the cytopathological expression of the infecting virus, so that, under certain conditions, each variant could shift from one type of plaque morphology to the other. However, attempts to correlate this plaque morphology shift with a difference in the glycopolypeptides synthesized in the infected cells were unsuccessful.

Membrane proteins specified by herpes simplex viruses. III. Role of glycoprotein VP7(B2) in virion infectivity

Experiments done with a temperature"sensitive mutant of herpes simplex virus type 1 (HSV-1) have revealed that one of the virisn glycoproteins, designated VP7(B2), is apparently not required for the production of enveloped virus particles, whereas it does play a critical role in virion infectivity. The mutant, designated HSV-1[HFEM]tsB5, fails to accumulate VP7(B2) at nonpermissive temperature and produces virions that lack detectable quantities of this glycoprotein and that have very low specific infectivity. The poor infectivity of the virions is most readily explained by failure of penetration into the host cell rather than by failure of adsorption to cells because it was shown that the VP7(B2)-deficient virions can bind to cells and that polyethylene glycol, an agent known to promote membrane fusion, can significantly enhance infectivity of the adsorbed virions.

Anatomy of herpes simplex virus DNA. XII. Accumulation of head-to-tail concatemers in nuclei of infected cells and their role in the generation of the four isomeric arrangements of viral DNA

Previous reports (H. Delius and J. B. Clements, J. Gen. Virol. 33:125-134, 1976; G. S. Hayward, R. J. Jacob, S. C. Wadsworth, and B. Roizman, Proc. Natl. Acad. Sci. U.S.A. 72:4243-4247, 1975; B. Roizman, G. S. Hayward, R. Jacob, S. W. Wadsworth, and R. W. Honess, Excerpta Med. Int. Congr. Ser. 2:188-198, 1974) have shown that herpes simplex virus DNA extracted from virions accumulating in the cytoplasm of infected cells consists of four populations of linear molecules differing in the orientation of the covalently linked large (L) and small (S) components relative to each other. Together, these four isomeric arrangements of viral DNA display four different termini and four different L-S component junctions. In the studies reported in this paper, we analyzed with restriction endonucleases the newly replicated viral DNA shortly after the onset of viral DNA synthesis, the progeny DNA accumulating in the nuclei late in infection, and rapidly sedimenting DNA present in nuclei of infected cells at 8 h after infection. In each instance the nuclear viral DNA contained a decreased concentration of all four terminal fragments and an increase in the concentration of fragments spanning the junction of L and S components relative to the concentration of other DNA fragments. The results are consistent with the hypothesis that the viral DNA accumulating in the nuclei consists of head-to-tail concatemers arising from the replication of DNA by a rolling-circle mechanism. A model is presented for generation of all four isomeric arrangements of herpes simplex virus DNA from one arrangement based on excision and repair of unit length DNA from head-to-tail concatemers and known features of the sequence arrangement of viral DNA.