Comparative analysis of the transcripts mapped in the BamHI DNA fragment B of avirulent HSV-1 HFEM, virulent HSV-1 F, and their intratypic recombinant viruses

Inhibitory effect of essential oils against herpes simplex virus type 2

Essential oils from anise, hyssop, thyme, ginger, camomile and sandalwood were screened for their inhibitory effect against herpes simplex virus type 2 (HSV-2) in vitro on RC-37 cells using a plaque reduction assay. Genital herpes is a chronic, persistent infection spreading efficiently and silently as sexually transmitted disease through the population. Antiviral agents currently applied for the treatment of herpesvirus infections include acyclovir and its derivatives. The inhibitory concentrations (IC50) were determined at 0.016%, 0.0075%, 0.007%, 0.004%, 0.003% and 0.0015% for anise oil, hyssop oil, thyme oil, ginger oil, camomile oil and sandalwood oil, respectively. A clearly dose-dependent virucidal activity against HSV-2 could be demonstrated for all essential oils tested. In order to determine the mode of the inhibitory effect, essential oils were added at different stages during the viral infection cycle. At maximum noncytotoxic concentrations of the essential oils, plaque formation was significantly reduced by more than 90% when HSV-2 was preincubated with hyssop oil, thyme oil or ginger oil. However, no inhibitory effect could be observed when the essential oils were added to the cells prior to infection with HSV-2 or after the adsorption period. These results indicate that essential oils affected HSV-2 mainly before adsorption probably by interacting with the viral envelope. Camomile oil exhibited a high selectivity index and seems to be a promising candidate for topical therapeutic application as virucidal agents for treatment of herpes genitalis.

Susceptibility of drug-resistant clinical herpes simplex virus type 1 strains to essential oils of ginger, thyme, hyssop, and sandalwood

Acyclovir-resistant clinical isolates of herpes simplex virus type 1 (HSV-1) were analyzed in vitro for their susceptibilities to essential oils of ginger, thyme, hyssop, and sandalwood. All essential oils exhibited high levels of virucidal activity against acyclovir-sensitive strain KOS and acyclovir-resistant HSV-1 clinical isolates and reduced plaque formation significantly.

Antibacterial, antiviral, antiproliferative and apoptosis-inducing properties of Brackenridgea zanguebarica (Ochnaceae)

Brackenridgea zanguebarica is a small tree that is used in traditional African medicine as a type of cure-all for many diseases, including the treatment of wounds. The yellow bark of B. zanguebarica was used for the preparation of an ethanolic extract, which was tested in various concentrations against eleven bacteria, Herpes simplex virus type 1 (HSV-1) and different human tumour cell lines. The extract that contains different polyphenolic substances like calodenin B. Cell growth inhibition, assessed via MTT-assay, was found in all tested human cell lines with IC50 values (concentration of extract that reduced cell viability by 50%) between 33 microg dry extract/mL for HL-60 human myeloid leukaemia cells and 93 microg dry extract/mL for HaCaT human keratinocytes. Staining with Annexin-V-FLUOS and JC-1 followed by subsequent analysis via flow cytometry revealed significant apoptosis-inducing properties. Analysis of caspase activity using a fluorogenic caspase-3 substrate showed a significant caspase activity in Jurkat T-cells after incubation with the extract. The bark extract had a pronounced activity against free HSV-1 and a strong antibacterial activity against Gram-positive strains (MICs: 6-24 microg dry extract/mL), which are often involved in skin infections. Additionally, no irritating properties of the extract could be observed in hen-egg test chorioallantoic membrane (HET-CAM) assay. These findings give a rationale for the traditional use of B. zanguebarica and are a basis for further analysis of the plant's components, their biological activity, and its use in modern phytotherapy.

Virucidal effect of peppermint oil on the enveloped viruses herpes simplex virus type 1 and type 2 in vitro

The virucidal effect of peppermint oil, the essential oil of Mentha piperita, against herpes simplex virus was examined. The inhibitory activity against herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2) was tested in vitro on RC-37 cells using a plaque reduction assay. The 50% inhibitory concentration (IC50) of peppermint oil for herpes simplex virus plaque formation was determined at 0.002% and 0.0008% for HSV-1 and HSV-2, respectively. Peppermint oil exhibited high levels of virucidal activity against HSV-1 and HSV-2 in viral suspension tests. At noncytotoxic concentrations of the oil, plaque formation was significantly reduced by 82% and 92% for HSV-1 and HSV-2, respectively. Higher concentrations of peppermint oil reduced viral titers of both herpesviruses by more than 90%. A clearly time-dependent activity could be demonstrated, after 3 h of incubation of herpes simplex virus with peppermint oil an antiviral activity of about 99% could be demonstrated. In order to determine the mode of antiviral action of the essential oil, peppermint oil was added at different times to the cells or viruses during infection. Both herpesviruses were significantly inhibited when herpes simplex virus was pretreated with the essential oil prior to adsorption. These results indicate that peppermint oil affected the virus before adsorption, but not after penetration into the host cell. Thus this essential oil is capable to exert a direct virucidal effect on HSV. Peppermint oil is also active against an acyclovir resistant strain of HSV-1 (HSV-1-ACV(res)), plaque formation was significantly reduced by 99%. Considering the lipophilic nature of the oil which enables it to penetrate the skin, peppermint oil might be suitable for topical therapeutic use as virucidal agent in recurrent herpes infection.

Analysis and characterization of the complete genome of tupaia (tree shrew) herpesvirus

The tupaia herpesvirus (THV) was isolated from spontaneously degenerating tissue cultures of malignant lymphoma, lung, and spleen cell cultures of tree shrews (Tupaia spp.). The determination of the complete nucleotide sequence of the THV strain 2 genome resulted in a 195,857-bp-long, linear DNA molecule with a G+C content of 66.5%. The terminal regions of the THV genome and the loci of conserved viral genes were found to be G+C richer. Furthermore, no large repetitive DNA sequences could be identified. This is in agreement with the previous classification of THV as the prototype species of herpesvirus genome group F. The search for potential coding regions resulted in the identification of 158 open reading frames (ORFs) regularly distributed on both DNA strands. Seventy-six out of the 158 ORFs code for proteins that are significantly homologous to known herpesvirus proteins. The highest homologies found were to primate and rodent cytomegaloviruses. Biological properties, protein homologies, the arrangement of conserved viral genes, and phylogenetic analysis revealed that THV is a member of the subfamily Betaherpesvirinae. The evolutionary lineages of THV and the cytomegaloviruses seem to have branched off from a common ancestor. In addition, it was found that the arrangements of conserved genes of THV and murine cytomegalovirus strain Smith, both of which are not able to form genomic isomers, are colinear with two different human cytomegalovirus (HCMV) strain AD169 genomic isomers that differ from each other in the orientation of the long unique region. The biological properties and the high degree of relatedness of THV to the mammalian cytomegaloviruses allow the consideration of THV as a model system for investigation of HCMV pathogenicity.

Structural organization and analysis of the viral terminase gene locus of Tupaia herpesvirus

Tupaia herpesvirus (THV) was isolated from spontaneously degenerating tissue cultures of malignant lymphoma, lung, and spleen cell cultures of tree shrews (Tupaia spp.). In order to determine the phylogenetic relatedness of THV the complete nucleotide sequence of the viral terminase (VTER) gene locus (6223 bp) of Tupaia herpesvirus strain 2 (THV-2) was elucidated and analysed. The VTER gene locus, encoding one of the most highly conserved herpes viral proteins is composed of two exons. The intron contains five potential open reading frames (ORFs). The arrangement of these ORFs is colinear with the corresponding regions in the genomes of the mammalian cytomegaloviruses. The precise primary structure of the THV-2 VTER splice junction was determined using RT-PCR and was found to be in agreement with the corresponding splice donor and acceptor sites of the mammalian cytomegaloviruses. The comparison of all six putative THV-2 proteins with the corresponding counterparts in other herpesviruses revealed that THV resides between the Human and the Murine cytomegalovirus (HCMV, MCMV). These results are in agreement with our previous statement, that THV and the known cytomegaloviruses are closely related to each other and should be classified into one taxonomic group. The genetic data presented here and in previous studies are based on the detailed comparison of highly conserved viral genes. Consequently, the classification of the Human and the cytomegaloviruses into the two genera Cyto- and Muromegalovirus, that is mainly based on overall genome structure, should be reconsidered.

Large envelope glycoprotein and nucleocapsid protein of equine arteritis virus (EAV) induce an immune response in Balb/c mice by DNA vaccination; strategy for developing a DNA-vaccine against EAV-infection

Equine arteritis virus (EAV) is a member of the Arteriviridae family, that includes lactate dehydrogenase-elevating virus (LDV), porcine reproductive and respiratory syndrome virus (PRRSV), and simian haemorrhagic fever virus (SHFV). Equine arteritis is a contagious disease of horses and is spread via respiratory or reproductive tract. The objective of the present study is to evaluate the possibility for developing a model system for prevention horses against an EAV infection by DNAvaccination. A cDNA bank from the RNA of EAV was established. This gene library contains the translation unit of the EAV open reading frames (ORF) 1 to 7. The identity of the cDNA was confirmed by nucleotide sequence analysis. Using this defined EAV cDNA gene library the cDNA sequence of the viral ORFs were molecularly cloned into the corresponding sites of well characterized and powerful expression vectors (pCR3.1, pDisplay, and/or pcDNA3.1/HisC). The capability of these recombinant plasmids expressing the gene products of the individual viral ORFs 3 to 5, and 7 in induction of an immune response in mouse system was investigated. The Balb/c mice (ten mice per assay) were inoculated with the DNA of the constructed expression vectors harboring and expressing the EAV cDNA of the viral ORFs. The Balb/c mice were injected with about 100 microg DNA diluted in 100 microl PBS. The DNA was injected subcutaneously and into the tibialis cranialis muscle (Musculus gastrocnemius). The mice were boosted 3 to 5 times with the same quantities of DNA and under the same conditions at about two week intervals. Control mice received the same amount of parental expression vectors via an identical route and frequency. The pre- and post-vaccinated sera of the individual animals were screened by neutralization tests (NT). Neutralizing antibodies against EAV were detected when the animals were inoculated with the DNA of the expression vectors harboring cDNA of the EAV ORFs 5 and 7. Highest NT-titers were observed when the animals were administered with the cDNA of ORF 5 and/or with the cDNA of the neutralization determinants of EAV that is located on the N-terminal ectodomain of the gene product of ORF 5 between the amino acid positions 1-121. These results obtained from these studies justified proofing the capability of the EAV cDNA sequences of the viral genes including ORFs 5 and 7 in the autologous animal system horse.

Structural organization of a conserved gene cluster of Tupaia herpesvirus encoding the DNA polymerase, glycoprotein B, a probable processing and transport protein, and the major DNA binding protein

The Tupaia herpesviruses (THVs) have been isolated from malignant lymphoma tissue cultures and from degenerating lung and spleen cell cultures of tree shrews (Tupaia spp.). Recently we succeeded in the localization of the gene locus of the THV DNA polymerase (DPOL) gene within the viral genome. Based on these results the highly conserved gene cluster of herpesviruses encoding the DPOL, the glycoprotein B (gB), a probable processing and transport protein (PRTP), and the major DNA binding protein (DNBI) was characterized in the genome of THV strain 2 (THV-2) in its entirety. The complete nucleotide sequence of the gene cluster was determined and it was discovered that the THV-2 gene products are most closely related to the corresponding proteins of mammalian cytomegaloviruses. The transcriptional activity of the four genes was confirmed by amplification of a part of the corresponding mRNAs obtained from infected cell RNA by RT-PCR. The homology values and the overall structure of the gene cluster, that shows specific colinearity with the corresponding clusters of the mammalian cytomegaloviruses, is further evidence that THV-2 is a member of the subfamily Betaherpesvirinae.

The syn3 strain HSZP of herpes simplex virus type 1 (HSV-1) is not pathogenic for mice and shows limited neural spread

Strain HSZP of the herpes simplex virus type 1 (HSV-1) forms large giant cells in vitro. This property was found associated with a mutation that alters the codon CGC (in the strain KOS or 17 sequence) to CAC (in the HSZP sequence), changing the amino acid 857 from arginine to histidine in the cytoplasmic domain of the glycoprotein B (gB) polypeptide chain. Giant cell formation by ANGpath was attributed to a mutation that alters the codon GCC (in KOS and strain 17 sequences) to GTC (in ANGpath sequence) changing the amino acid 854 in the same (syn3) region of the gB molecule. In contrast to the ANGpath virus, which is pathogenic (1 LD50 < 1 x 10(4) PFU) for adult DBA/2 mice after peripheral inoculation, strain HSZP was never found to be lethal for adult mice. Whereas ANGpath-infected mice which survived acute infection frequently (79%) developed latency in the regional sensory ganglion (as proved by virus reactivation during explantation), latent HSZP reactivated in ganglion culture at a considerably reduced rate (21%). Only 10-day-old DBA/2 mice were sensitive to HSZP infection. In these, HSZP spread from the site of peripheral administration mainly by hematogenous route. The neural spread of HSZP in suckling DBA/2 mice was manifested by the involvement of vegetative neurons in the wall of the small intestine and in the retroperitoneal vegetative ganglia. We conclude that HSZP, a polykaryocyte-forming strain with a mutation in the syn3 region II, shows limited neuroinvasity for mice after peripheral administration.

Restitution of the UL56 gene expression of HSV-1 HFEM led to restoration of virulent phenotype; deletion of the amino acids 217 to 234 of the UL56 protein abrogates the virulent phenotype

Recently it was shown that the avirulent phenotype of HSV-1 strain HFEM is correlated to the lack of DNA sequences of the promoter region of the UL56 gene. In order to investigate the role of the UL56 gene of HSV-1 in the process of viral pathogenicity in more detail, a complete copy of the UL56 gene of the virulent HSV-1 strain 17 was inserted within the DNA sequences of the incomplete UL56 gene of the genome of HSV-1 strain HFEM. The UL56 gene of HSV-1 strain 17 comprises 1428 bp corresponding to the nucleotide positions (NP) 11,5967-117,395 of the genome of HSV-1 strain 17 (SacII-DNA fragment) containing the promoter region and the entire UL56 gene with identical transcription termination signals. This particular DNA fragment was inserted into the corresponding region of the genome of HSV-1 strain HFEM by co-transfection experiments in which the beta-galactosidase gene served as reporter gene. Those recombinant viruses with the ability to express the UL56 gene were tested for their pathogenicity in vivo. The results of these experiments indicate that the restoration of the viral UL56 gene expression led to the restitution of the virulent phenotype of HSV-1 strain HFEM. The UL56 protein which has been shown to be a component of the virion possesses several characteristic signatures e.g. a hydrophobic domain at the carboxy-terminus between amino acid residues 217 and 234 (VFGVVAIVVVIILVFLWR). In order to investigate the role of this particular signature of the UL56 protein in the process of viral pathogenicity, site-specific mutagenesis was performed for removing the carboxy-terminus of the UL56 protein. The deleted region of the DNA sequences of the UL56 gene between NP 1122-1175 corresponds to NP 116 220-116 373 of the viral genome. The DNA sequences of the UL56 gene of virulent HSV-1 strain 17 and F were replaced by DNA sequences of the truncated UL56 gene by co-transfection experiments in which the beta-galactosidase gene served as a reporter gene. Those recombinant viruses with the ability to express the truncated UL56 gene were examined for their pathogenicity in vivo. The analysis revealed that the expression of the truncated UL56 protein (without hydrophobic domain 217-234 aa) was not sufficient for the maintenance of the virulent phenotype of HSV-1 strains.

In vitro expression of UL56 gene of herpes simplex virus type 1; detection of UL56 gene product in infected cells and in virions

In order to investigate the functional properties of the UL56 gene of herpes simplex virus type 1 (HSV-1), it was necessary to express the UL56 protein in vitro. The DNA sequences corresponding to the open reading frame of the UL56 gene of HSV-1 strain F were amplified from genomic viral DNA by PCR using primers corresponding to the translational start and termination regions of the UL56 ORF. The PCR product (705 bp) was inserted into the EcoRI/XbaI recognition sites of the bacterial expression vector pMal-c2. This procedure allowed the expression of the viral UL56 gene fused to the maltose-binding protein (MBP) of Escherichia coli, and subsequent cleavage of the fusion protein with the specific protease factor Xa. The induced fusion protein was purified by affinity chromatography using amylose columns. The apparent molecular weight of the fusion protein was about 70 kDa. Factor Xa cleaves the fusion protein into two subfragments of 42 kDa (MBP) and 30 kDa (UL56). Rabbit antisera induced against recombinant UL56 protein were used for detection of the UL56 gene product during the infection cycles of HSV-1. The presence of the UL56 protein was detected in infected cells and in HSV-1 virions by Western blot experiments and by immunofluorescence assays. A strong and increasing cytoplasmic fluorescence was observed in RC-37 cells infected with HSV-1 strain F between 6 and 16 h post-infection. In addition it was found that human HSV-1 IgM/IgG positive convalescent sera recognized the recombinant UL56 protein.

Herpes simplex virus type 1 (HSV-1) UL56 gene is involved in viral intraperitoneal pathogenicity to immunocompetent mice

A comparison of the pathogenicity in mice of the recombinant herpes simplex virus type 1 (HSV-1) strain HSV-1-M-LacZ, in which the UL56 gene has been deleted, was made with its parental strain F, following infection in different mouse strains. The polymerase chain reaction (PCR) technique was used to study the migration of virus DNA in the mouse model. Tissues from adult mice infected intraperitoneally (IP) with one of three HSV-1 strains (F, HFEM or HSV-1-LacZ) were examined for the presence of viral DNA. DNA of the pathogenic strain F was detected in the adrenal glands, spinal cord, brain, liver and pancreas. DNA of HSV-1-M-LacZ was detected in the same tissues. However, DNA of the apathogenic strain HFEM was detected transiently (on days 2 and 3 p.i., but not days 1, 5 or 7), only in the adrenal glands and no viral DNA was detected in any of the other tissues. HSV-1 pathogenic strains injected intraperitoneally into newborn mice (7 days old) killed most of the mice. In the surviving mice viral DNA of the three virus strains was found in peritoneal exudate cells (PEC), adrenal glands, spinal cord, liver and spleen. It was found that HSV-1-M-LacZ, which lacks the UL56 gene, resembled in pathogenicity to the newborn mice the pathogenic HSV-1 strains F and KOS. The PCR technique was used to trace viral DNA in tissues of the mice which survived HSV-1 infection at 7 weeks of age. Only HSV-1 (KOS) DNA was detected in the pancreas. The brains of these mice did not contain viral DNA. It is suggested that HSV-1 DNA may reside in surviving HSV-1- infected newborn mice in a "latent" state in nonneural tissues.

Determination of the coding capacity of the BamHI DNA fragment B of apathogenic Herpes simplex virus type 1 strain HFEM by DNA nucleotide sequence analysis

Herpes simplex virus type 1 (HSV-1) strain HFEM acquired an apathogenic phenotype due to a deletion within the DNA sequences of the BamHI DNA fragment B of the viral genome. In order to investigate the coding strategy of this particular region of the genome of HSV-1 strain HFEM the DNA nucleotide sequence of the BamHI DNA fragment B was determined. This analysis revealed that the BamHI DNA fragment B of HSV-1 strain HFEM comprises 6593 bp, corresponding to the nucleotide positions (np) 113322 to 117088 and np 120643 to 123465 of the genome of HSV-1 strain 17. According to these data the deletion of the genome of HSV-1 strain HFEM occurred between the np 117089 and 120642. The promoter region of the UL56 gene of HSV-1 strain HFEM is a part of the deleted DNA sequences. Therefore, this gene of HSV-1 strain HFEM is affected and cannot be expressed. The first 35 amino acid (AA) residues of the deduced amino acid sequence of the UL56 open reading frame (ORF) were found to be identical to the amino acid sequence of the UL56 genes of HSV-1 strains 17 and F. However, due to a deletion at np 3494 of the BamHI DNA fragment B of HSV-1 strain HFEM the amino acid composition of the predicted UL56 gene of HSV-1 strain HFEM is different from HSV-1 strain 17 between amino acid positions 36 and 233. In addition the deduced amino acid sequence of the IRL (inverted repeat of the long segment) copy of the IE110 gene of HSV-1 strain HFEM was found to be about 342 amino acids shorter than the amino acid sequence of IE110 gene of HSV-1 strain 17 (775 AA). This was based on a point mutation which was detected within the DNA sequences of Exon 3 of this copy of IE110 gene of HSV-1 strain HFEM.

Elimination of UL56 gene by insertion of LacZ cassette between nucleotide position 116030 to 121753 of the herpes simplex virus type 1 genome abrogates intraperitoneal pathogenicity in tree shrews and mice

In order to investigate whether or not the UL56 gene is involved in those processes determining the viral pathogenicity and latency, a recombinant virus HSV-1-M-LacZ was constructed in which the DNA sequences between nucleotide position (np) 116030 and 121753 were replaced by the E. coli beta-galactosidase (LacZ) gene. This deletion spans from the carboxyterminus of UL55 (np 116030) to the second exon of IE110 (np 121753) eliminating UL56 and the variable region of the BamHI DNA fragment B which were implicated in intraperitoneal pathogenicity and latency. The host range and growth kinetics of the recombinant virus HSV-1 M-LacZ were comparable to the parental strain HSV-1 F. As expected it was found that HSV-1-M-LacZ lost its virulent phenotype and was not able to develop acute infection in animals. The state of the UL56 gene was investigated by determining the cDNA sequence of the UL56 gene transcript of HSV-1 F using PCR products obtained after amplification of the cDNA with oligonucleotide primers corresponding to the translational start and stop codons of this gene. This analysis revealed that the DNA sequence of the UL56 gene of HSV-1 F differed from those DNA sequences determined for the genomic DNA of HSV-1 strain 17. Between nucleotide position 116343 and 116344 two nucleotides -AG- are inserted which prolong the ORF of the UL56 gene to 233 amino acids with a predicted molecular weight of 30 kDa.

In vitro transcription and translation of proteins encoded by the BamHI-B genomic fragment of herpes simplex virus-1

The BamHI-B DNA fragment of herpes simplex virus type-1 (HSV-1) is associated with intraperitoneal pathogenicity. Among the recently mapped RNA transcripts from this fragment (15), one was reported to be associated with latency. To relate the RNA transcripts to virus pathogenicity, the in vitro-transcribed RNAs from BamHI-B fragments of three HSV-1 strains--F (pathogenic), R19, and HFEM (apathogenic), were studied by in vitro translation. When the BamHI-HpaI (0.738-0.755 map units) DNA fragment from HSV-1 strain F was transcribed rightward and translated, three proteins of 70, 63, and 51 kD were detected. The 63 kD protein resembles in size and orientation the protein encoded by the ICP-27 (IE-2) gene (0.740-0.749 mu). The 51 kD polypeptide is assumed to be a prematurely terminated form of this protein. No proteins were obtained from RNA transcribed in the opposite direction. The SalI-NcoI (0.746-0.761 mu) fragment of the three HSV-1 strains yielded two proteins of 25 and approximately 15 kD when transcribed rightward and a 35 kD polypeptide from RNA transcribed in the opposite direction. As a result of the genomic deletion in HFEM, it was possible to obtain the 35 kD protein from the SalI-SalI DNA fragment (0.746-0.761 mu) as well. In vitro transcription and translation of the PstI-SalI (0.778-0.790 mu) DNA fragment (the right-hand side of HpaI-P) did not result in protein synthesis. The possibility that the UL56 gene is connected with the intraperitoneal pathogenicity of HSV-1 is discussed.

Identification and mapping of the UL56 gene transcript of herpes simplex virus type 1

The herpes simplex virus type 1 (HSV-1) strain HFEM is apathogenic for tree shrews and mice by the intraperitoneal application route. This is due to a 4.1 kbp deletion [0.762 to 0.789 map units (mu)] within the BamHI DNA fragment B of the viral genome. With exception of 71 bp the DNA sequences of the deleted region are located within the repetitive DNA sequences of the inverted repeat of the L segment of the HSV-1 genome (IRL). A 1.5 kb RNA hybridizing to the DNA sequences of the HSV-1 genome at map position 0.760-0.762 (BssHII DNA fragment F, part of the BamHI DNA fragment B) was found to be missing in cells infected with HSV-1 HFEM and other apathogenic HSV-1 strains. A detailed analysis of the transcriptional profile of this region of the pathogenic prototype strain HSV-1 F and strand-specific hybridizations revealed that this 1.5 kb RNA species is transcribed at 2 to 4 h p.i. in leftward orientation. The corresponding open reading frame in the HSV-1 genome had been predicted as the UL56 gene. The absence of this 1.5 kb RNA in HSV-1 HFEM-infected cells is due to the fact that the promoter region of the UL56 gene is located within those DNA sequences which are deleted in the HSV-1 HFEM genome. A specific DNA fragment (650 bp) was amplified by reverse polymerase chain reaction using oligonucleotide primers corresponding to the predicted translational start and termination region of the UL56 gene. The corresponding cDNA had been derived from cellular RNA from HSV-1 F-infected cells using oligo(dT) priming. This indicates that the 1.5 kb RNA is the real transcript of the UL56 gene of HSV-1.

Expression of human immunodeficiency virus type 1 gag gene using genetically engineered herpes simplex virus type 1 recombinants

Infectious herpes simplex virus type 1 (HSV-1) recombinants were constructed by inserting the cDNA sequence of the human immunodeficiency virus type 1 (HIV-1) gag gene (from nucleotide position 675 [SacI] to 3859 [Asp718] of the cDNA sequences of HIV-1 strain BH-10) within the DNA sequences of the BamHI DNA fragment B of the genome of an apathogenic HSV-1 strain HFEM. This HSV-1 strain possesses a 4.1-kbp deletion within the BamHI DNA fragment B between 0.762 and 0.789 map units of the viral genome, which allows the insertion of at least 4 kbp of foreign genetic material into this particular region. The DNA sequences of the immediate early promoter (IE4) of HSV-1 that were inserted upstream from the gag gene were used as a promoter. The screening of 205 virus stocks derived from individual plaques revealed that 46 recombinant viruses harbor HIV-1 gag-specific DNA sequences. However, it was found that only six of the recombinant viruses are able to express the gag gene product of HIV-1. This indicates that the ratio of the positive recombination events is about 2.9%.

Characterization of RNA transcripts from herpes simplex virus-1 DNA fragment BamHI-B

Herpes simplex virus type 1 (HSV-1) DNA fragment BamHI-B (0.738-0.809 map units) was recently reported to be associated with the phenotype of intraperitoneal pathogenicity and to encode a latency-associated RNA transcript. Part of this fragment resides within the internal repeat sequence of the long (L) region of the viral genome. In this study, RNA transcripts from BamHI-B were characterized. In addition to immediate-early mRNAs IE-1 and IE-2, eight novel RNA species were found. Three transcripts were mapped in the repeat regions of this fragment and five transcripts in the unique L region of BamHI-B. In addition, transcription activity from these regions was compared in several HSV-1 strains. These included the intraperitoneal virulent F and KOS strains, the avirulent strain HFEM, as well as the HFEM/F intratypic virulent recombinant R-MIC1. Several differences were noted and their possible relevance to virulence is discussed.

Organotropism of latent herpes simplex virus type 1 is correlated to the presence of a 1.5 kb RNA transcript mapped within the BamHI DNA fragment B (0.738 to 0.809 map units)

The transcriptional activity of the DNA sequences within the genome of herpes simplex virus type 1 (HSV-1) at the coordinates 0.760 to 0.762 and their influence in the process of viral latency were investigated. Seven avirulent HSV-1 strains (HFEM, 1752/2, 1752/3, 1752/11, 1469, 1475, 1618), two virulent wild-type HSV-1 strains (F and 17) and three virulent intratypic HSV-1 recombinant viruses (R19, R26, RM1C1) were screened. The virulent HSV-1 strains colonize the ganglia but the avirulent virus strains are only able to persist in the spleen of infected animals (tree shrews). A 1.5 kb RNA transcript was detectable in all virus strains recovered from the ganglia. This RNA transcript hybridised to the HSV-1 DNA sequences at the genome coordinates 0.760 to 0.762 (BssHII DNA fragment F, part of the BamHI DNA fragment B of HSV-1, 0.738 to 0.809 map units (m.u.]. In contrast it was found that the 1.5 kb RNA transcript was missing or its size was changed in cells infected with those HSV-1 strains which were recovered from the spleens of latently infected animals. The state of viral latency of three defined deletion variants of HSV-1 strain 17 (1704, 1705, and 1706) whose genome harbors deletions (2.2 to 5.3 kb) comprising the DNA sequences of the particular region (0.760 to 0.762 m.u.) was investigated. These studies revealed that all three deletion variants could only be recovered from the spleens of latently infected tree shrews.