Transduction of virulence in herpes simplex virus type 1 from a pathogenic to an apathogenic strain by a cloned viral DNA fragment

Identification and characterization of toll-like receptors (TLRs) in the Chinese tree shrew (Tupaia belangeri chinensis)

In mammals, the toll-like receptors (TLRs) play a major role in initiating innate immune responses against pathogens. Comparison of the TLRs in different mammals may help in understanding the TLR-mediated responses and developing of animal models and efficient therapeutic measures for infectious diseases. The Chinese tree shrew (Tupaia belangeri chinensis), a small mammal with a close relationship to primates, is a viable experimental animal for studying viral and bacterial infections. In this study, we characterized the TLRs genes (tTLRs) in the Chinese tree shrew and identified 13 putative TLRs, which are orthologs of mammalian TLR1-TLR9 and TLR11-TLR13, and TLR10 was a pseudogene in tree shrew. Positive selection analyses using the Maximum likelihood (ML) method showed that tTLR8 and tTLR9 were under positive selection, which might be associated with the adaptation to the pathogen challenge. The mRNA expression levels of tTLRs presented an overall low and tissue-specific pattern, and were significantly upregulated upon Hepatitis C virus (HCV) infection. tTLR4 and tTLR9 underwent alternative splicing, which leads to different transcripts. Phylogenetic analysis and TLR structure prediction indicated that tTLRs were evolutionarily conserved, which might reflect an ancient mechanism and structure in the innate immune response system. Taken together, TLRs had both conserved and unique features in the Chinese tree shrew.

Characterization of a MAVS ortholog from the Chinese tree shrew (Tupaia belangeri chinensis)

Human mitochondrial antiviral signaling protein (hMAVS, also known as IPS-1, VISA, or Cardif) is essential for antiviral innate immunity. The Chinese tree shrew (Tupaia belangeri chinenses), a close relative of primates, is emerging as a potential animal model for investigating viral infection. However, there is a lack of biological knowledge about the antiviral innate immunity of the tree shrew. In this study, we identified and characterized the function of the Chinese tree shrew MAVS gene (tMAVS). The cDNA of tMAVS was 2771 bp in length and encoded a polypeptide of 501 amino acids. Phylogenetic analyses based on the amino acid sequences revealed a closer affinity of tMAVS with those of primates. Quantitative real-time PCR analysis indicated that tMAVS mRNA was constitutively expressed in all seven tissues analyzed in this study. The tMAVS mRNA expression was rapidly and significantly increased after RNA virus infections. Ectopic-expression of tMAVS significantly potentiated the virus-triggered activation of IRF3, NF-κB and interferon-β (IFN-β), whereas knockdown of tMAVS displayed the opposite effect. Furthermore, tMAVS mutants lacking the caspase activation and recruitment (CARD) domains or the transmembrane (TM) domain were unable to induce IFN-β. Similar with hMAVS, mitochondrial localization of tMAVS was dependent on its domain. Collectively, this study revealed evolutionary conservation of the MAVS antiviral signaling pathway in the Chinese tree shrew.

Diverse interleukin-7 mRNA transcripts in Chinese tree shrew (Tupaia belangeri chinensis)

Interleukin-7 (IL7) is a pleiotropic cytokine that is actively involved in the immune system. The Chinese tree shrew (Tupaia belangeri chinensis) has been proposed as an alternative experimental animal to primates in biomedical research. However, there is a lack of biological knowledge about the immune system of the tree shrew. In this study, we cloned the IL7 gene (tIL7) in the Chinese tree shrew and quantified the expression of mRNA transcripts in eight tissues (heart, liver, spleen, lung, kidney, intestine, skeletal muscle and brain) from 20 individuals. Eleven tIL7 mRNA transcripts were identified in different tissues. The canonical form (tIL7c) had a length of 1817 bp and encoded a predicted gene product with 177 amino acids. Phylogenetic analyses based on the amino acid sequences revealed a considerably large genetic difference between tree shrew and human. Quantification of mRNA expression of transcripts tIL7c, tIL7-sv1, tIL7-sv2 and tIL7-sv3 showed that these transcripts were expressed in all tissues, albeit the expression levels varied in different tissues. Transcripts tIL7c, tIL7-sv1, and tIL7-sv2 had the lowest expression in brain, and tIL7-sv3 had a dramatically high mRNA expression in skeletal muscle and heart. The mRNA expression levels of tIL7c and tIL7-sv1 were significantly increased upon ploy(I:C) stimulation in tree shrew primary renal cells. As with human full-length IL7, tIL7c, tIL7-sv1, tIL7-sv2 and tIL7-sv3 showed similar a subcellular localization pattern. Our results identified diverse tIL7 transcripts in the Chinese tree shrew, which may play a potential role in modulating IL7-regulated biological effects.

Immunization with a nonpathogenic HSV-1 strain prevents clinical and neuroendocrine changes of experimental HSV-1 encephalitis

We examined whether immunization with the nonpathogenic strain R-15 of herpes simplex virus-1 (HSV-1) may prevent the clinical and neuroendocrine changes induced by the pathogenic HSV-1 strain Syn17+. Inoculation of strain Syn17+ to control rats induced fever, marked motor hyperactivity and aggressive behavior, and increased serum ACTH, corticosterone (CS) and brain prostaglandin-E2 production. Mortality was 100%. Immunization with strain R-15 prior to challenge with Syn17+ induced the production of neutralizing antibodies to HSV-1 Syn17+, and abolished the above clinical and neuroendocrine changes. Mortality was completely prevented. These results indicate that immunization with HSV-1 strain R-15 protects rats from lethal HSV-1 encephalitis and prevents its clinical and neurochemical manifestations.

The genome of cowpox virus contains a gene related to those encoding the epidermal growth factor, transforming growth factor alpha and vaccinia growth factor

Cowpox virus (CPV) is a member of the Orthopoxvirus genus and has the genetic capacity to encode a multitude of genes that interfere with the host inflammatory and immune response or modulate the physiological state of infected and non-infected cells. Among these CPV factors are receptors homologous to interferon and tumor necrosis factor receptors and also a viral cellular serine-proteinase analog. Here we describe the detection of a CPV gene that encodes a protein homologous to epidermal growth factor, transforming growth factor alpha and poxvirus growth factors, such as the vaccinia growth factor (VGF). The VGF and other poxvirus growth factors are produced early in the infection and are secreted into the medium where they bind to the EGF receptors, generating mytotic responses. The cowpox growth factor (CGF) gene was detected in three copies on the virus genome by PCR, and by northern and southern blot hybridization using VGF nucleotide sequences as primers and probes. The CPV gene has a strong nucleotide and predicted amino acid similarity with VGF, and is also produced early in the infection.

Glycoprotein K of herpes simplex virus: a transmembrane protein encoded by the UL53 gene which regulates membrane fusion

Glycoprotein K (gK) encoded by the UL53 gene is the ninth out of eleven HSV glycoproteins (gps). The precursor gK (pgK) is a transmembrane protein with four hydrophobic domains, which consists of 338 amino acids. The UL53 gene has two initiation codons: the upper overlaps with the UL52 ORF, while the lower is located 55 codons downstream and specifies a truncated precursor of the gK polypeptide. The UL53 gene and the upstream located UL52 gene have a common polyadenylation signal downstream from the UL53 stop codon so that the UL53 mRNA is completely nested within the UL52 transcript. The syn1 mutations in several KOSsyn mutants and in the MPsyn virus, which had been fine mapped to DNA coordinates 0.735-0.740, were later on located to the UL53 gene, especially to its portion which specifies the first 120 amino acids (aa) from the N-terminus (most frequently residue 40) and to a less precisely defined locus between aa 301-310 (close to the C-terminus). Point mutations in the N-terminal ectodomain of gK, which are related to syn formation, impair the putative ability of this region to down-regulate membrane fusion. The two N-glycosylated mannose core oligosaccharides are attached to the Asn residues of the gK polypeptide at positions 48 and 58, respectively. In infected cells, gK is localized mainly in the nuclear and endoplasmic reticulum (ER) membranes. It is not clear, whether gK becomes incorporated into the envelope of mature HSV particles. Studies with the insertion/deletion gK mutants showed the importance of gK for capsid envelopment, for the transportation and egress or virions from infected cells. It seems that gK has an essential role in virion egress, even though this glycoprotein acts in accord with gH and with another membrane protein encoded by the UL20 gene.

Identification of the UL56 protein of herpes simplex virus type 1 within the virion by immuno electron microscopy

Recently the UL56 protein of herpes simplex virus type 1 (HSV-1) was shown to be associated with the virion of HSV-1 as determined by Western blot analysis. The detection of the UL56 protein in infected cells and its association with virions of HSV-1 is of particular importance, pointing to a possible involvement of UL56 protein in virus-host interactions. In order to investigate the properties of the UL56 protein further immuno-localization was performed using rabbit hyperimmune serum against fusion recombinant UL56 protein and purified virions of HSV-1 strain F. The UL56 protein was detected in the HSV-1 virions by immuno gold negative staining.

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.

Cyclosporin A resistance of herpes simplex virus-induced "fusion from within" as a phenotypical marker of mutations in the Syn 3 locus of the glycoprotein B gene

We here report research in which nine strains of Herpes simplex virus (HSV) with fusing activity were investigated in order to establish precise phenotypical markers of mutations in the carboxy terminus of glycoprotein B (gB). The gene region encoding the carboxy terminus of gB was isolated, then cloned, and finally sequenced. Our investigation showed that seven strains have different mutations in the syn 3 locus. We observed no base difference in the gB gene region encoding the carboxy terminus of gB of two other strains. Strains with a mutation in the carboxy terminus of gB induced fusion from within (FFWI) in the presence of Cyclosporin A (CyA) at a concentration up to 150 microM. There are two clusters of mutations correlated with the syn 3 locus and selected in the presence of CyA: One group comprised of amino acid substitutions at position 816, the other of changes at positions 853, 854, and 857. In contrast, the fusion induced by strains with mutations in other syn loci is CyA sensitive. CyA inhibits the FFWI at concentrations of 20-60 microM. The results demonstrate the CyA resistance of HSV-induced FFWI should serve as a phenotypical marker of mutations in the carboxy terminus of gB. Moreover, our investigations revealed that fusion from without (FFWO) does not always serve as a phenotypical marker of mutations in the syn 3 locus. On the one hand, all FFWO-positive strains possess a syn 3 locus mutation, whilst, on the other hand, five strains with mutations in the carboxy terminus of gB are FFWO negative.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of herpes simplex virus type-1 UL41 gene on the stability of mRNA from the cellular genes: beta-actin, fibronectin, glucose transporter-1, and docking protein, and on virus intraperitoneal pathogenicity to newborn mice

Infection with HSV-1 is accompanied by the shut-off of cellular gene expression. The virion-associated function is encoded by the viral gene UL41. An HSV-1 mutant, vhs-1, which has a genomic deletion in the UL41 gene, is incapable of inducing the shut-off of cellular gene expression. The effect of HSV-1 infection on the shut-off of the cellular genes (or mRNA degradation) was studied specifically with the cellular genes for beta-actin, fibronectin, glucose transporter-1, and the docking protein. The level of these specific mRNAs was measured in cells infected with several HSV-1 strains and was compared to that of vhs-1- and mock-infected cells. It was possible to demonstrate a marked reduction in the level of the specific mRNA from these cellular genes in cells infected with several HSV-1 strains but not with the vhs-1 mutant. The pathogenicity of the HSV-1 vhs-1 mutant to newborn mice was studied. It was found that the mutant is less pathogenic to newborn mice than its parental strain HSV-1 KOS.

Mutations in the UL53 gene of HSV-1 abolish virus neurovirulence to mice by the intracerebral route of infection

The cell fusion protein, the product of the UL53 gene, is responsible for intracerebral (IC) pathogenicity of HSV-1. Recombinant HSV-1 R15 is apathogenic to mice by the IC route of inoculation, while intratypic recombinants, in which the UL53 gene in R15 was replaced by an analogous sequence from the pathogenic strain R19, regained IC pathogenicity. The nucleotide sequence of the UL53 gene of HSV-1 strains R15 (apathogenic) and R19 (pathogenic) was determined and compared to that of other pathogenic strains. Four mutations were found which are thought to be responsible for the apathogenic phenotype of HSV-1 strain R15. Northern blot hybridization of RNA extracted from BSC-1 cells infected with several HSV-1 strains indicated that all of the virus strains tested expressed equal amounts of UL53 mRNA in infected cell cultures. Demonstration of the expression of UL53 mRNA in brains of mice infected with HSV-1 strains was made possible by the combined use of a rapid method for mRNA extraction (Oligo dT-linked magnetic beads) and a highly sensitive technique for detection of the existence of the UL53-specific mRNA (cDNA synthesis followed by PCR). It was shown that both pathogenic (KOS and P42) and apathogenic (R15) HSV-1 strains expressed the UL53 gene in brains of IC infected mice.

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%.

Importance of the HpaI-P sequence for herpes simplex virus-1 replication in the adrenal glands

The ability of several strains and recombinants of herpes simplex virus 1 (HSV-1) to proliferate in the adrenal glands and to invade the spinal cord was studied. After intraperitoneal infection, pathogenic HSV-1 strains replicated in the adrenal glands, penetrated the spinal cord and migrated to the brain. The nonpathogenic strain HFEM could not replicate in the adrenal glands, but the recombinant virus MLC1 was able to do so after rescue by reinsertion of the HpaI-P sequence into the BamHI fragment of HFEM DNA. However the recombinant MLC1 virus could not penetrate the spinal cord. The effect of HSV-1 infection on the expression of the cellular genes for multidrug resistance (in the adrenal glands) and proenkephalin A (in the spinal cord) was also studied.

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.

Pathogenicity of glycoprotein C negative mutants of herpes simplex virus type 1 for the mouse central nervous system

A previous study from our laboratory showed that a mutant of herpes simplex virus type 1 (HSV-1), strain KOS-321, carrying a deletion in the structural gene for glycoprotein C (gC) had reduced pathogenicity for the mouse central nervous system when compared to the wild-type virus (Kümel et al., 1985). In this study, eight additional gC negative (gC-) mutants derived from KOS-321 were shown to vary widely in their ability to induce lethal encephalitis in female DBA/2 mice following intracerebral inoculation. This variation in virulence showed no correlation with thymidine kinase activity. One less virulent gC- strain, gC-39, was further studied to determine whether the neurovirulent phenotype could be restored by rescue of the gC gene using standard marker rescue cotransfection procedures. The resulting progeny contained 2% gC+ recombinant virions and was tested for its ability to cause encephalitis. Although this progeny had increased virulence, it was not attributable to the acquisition of the gC gene since passive immunization of mice with a pool of anti-gC monoclonal antibodies had no effect on the development of encephalitis and only gC- viruses were isolated from diseased brain tissues. In agreement with these findings, individual plaque-purified gC positive (gC+) virus recombinants were shown not to have been restored to the wild-type virus level of neurovirulence. It is concluded that gC is not a virulence determinant in this mouse model of HSV-induced encephalitis and that cotransfection procedures can induce additional mutations that affect viral pathogenesis.

Role of glycoprotein gIII of pseudorabies virus in virulence

Deletion mutants of pseudorabies virus unable to express glycoprotein gIII, gI, or gp63 or double and triple mutants defective in these glycoproteins were constructed, and their virulence for day-old chickens inoculated intracerebrally was determined. Mutants of wild-type pseudorabies virus defective in glycoprotein gIII, gI, or gp63 were only slightly less virulent (at most, fivefold) for chickens than was the wild-type virus. However, mutants defective in both gIII and gI or gIII and gp63 were avirulent for chickens, despite their ability to grow in cell culture in vitro to about the same extent as mutants defective in gIII alone (which were virulent). These results show that gIII plays a role in virulence and does so in conjunction with gI or gp63. The effect of gIII on virulence was also shown when the resident gIII gene of variants of the Bartha vaccine strain (which codes for gIIIB) was replaced with a gIII gene derived from a virulent wild-type strain (which codes for gIIIKa); gIIIKa significantly enhanced the virulence of a variant of the Bartha strain to which partial virulence had been previously restored by marker rescue. Our results show that viral functions that play a role in the virulence of the virus (as measured by intracerebral inoculation of chickens) may act synergistically to affect the expression of virulence and that the ability of the virus to grow in cell culture is not necessarily correlated with virulence.

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

HSV-1 HFEM, whose genome harbors a deletion of 4.1 kbp (0.762 to 0.789 map units (mu] is avirulent for mice and tree shrews by the intraperitoneal (i.p.) application route. Insertion of the BamHI DNA fragment B (0.738 to 0.809 mu) and/or the MluI DNA fragment (0.7615 to 0.796 mu) molecularly cloned from virulent HSV-1 F, restored the i.p. pathogenicity to strain HFEM and led to the isolation of virulent intratypic recombinants. In order to determine the RNA transcripts mapped in the BamHI DNA fragment B of the HSV-1 HFEM, HSV-1 F, and their intratypic recombinants R15, R19, R26, and R-Ml-C1, a comparative analysis was performed using Northern blot hybridizations. Two novel RNA transcripts of 3.5 and 1.5 kb were detected which hybridize to the left terminus (0.738 to 0.746 mu) of the BamHI DNA fragment B. The 1.5 kb RNA transcript was missing in the avirulent HSV-1 HFEM. Hybridization with the BssHII DNA fragment F (0.760 to 0.762 mu) led to detection of a 3.5 kb RNA transcript by HSV-1 HFEM which was missing in all other viruses tested. In contrast a 1.5 kb RNA transcript was detectable in all other virus strains with the exception of HSV-1 HFEM. The 3.5 kb transcript hybridized to the right-hand flank of the deleted region in the genome of HSV-1 HFEM (Asp718/SalI DNA fragment; 0.786 to 0.79 mu). The detection of the novel 1.5 kb RNA, which is missing in HSV-1 HFEM, and the appearance of the newly transcribed 3.5 kb RNA in HSV-1 HFEM only, indicates a new open reading frame in this particular region as a consequence of the fusion of the DNA sequences at both ends of the deletion in the genome of HSV-1 HFEM.

HSV-1 DNA sequence determining intraperitoneal pathogenicity in mice is required for transcription of viral immediate-early genes in macrophages

The relationship between intraperitoneal (ip) pathogenicity in vivo of herpes simplex virus type 1 (HSV-1) and infection of macrophages (m phi) in vitro was studied. The apathogenic HSV-1 strain HFEM disappeared from the peritoneum of infected mice following ip inoculation, while the pathogenic F strain persisted in the peritoneum and penetrated the mouse nervous system, and eventually the mice died, showing severe neurological signs. When peritoneal m phi were infected in vitro, a direct correlation with pathogenicity in vivo was found with several HSV-1 strains and recombinants. HSV-1 strains (F, KOS, R-M1C1) which were pathogenic for mice by the ip route, induced cytopathic effect (CPE) in m phi in vitro. Strain F transcribed viral immediate-early genes and synthesized viral DNA in m phi that were treated with L-cell conditioned medium (as a source of colony-stimulating factor) prior to infection. Apathogenic HSV-1 strains (HFEM, R-15, R-19) did not cause CPE in m phi. The HFEM strain was already blocked in the transcription of viral alpha genes in the infected m phi, but replicated well in control BSC-1 cells. An intratypic recombinant (R-M1C1), produced by cotransfection of HFEM DNA with a cloned Mlul-Mlul DNA fragment (coordinates 0.7615-0.796) from HSV-1 strain F, that was shown [Becker et al. (1986). Virology 149, 255-259] to have regained partial ip virulence for mice, now transcribed alpha genes, synthesized viral DNA, and induced CPE in m phi. It appears that the viral DNA fragment responsible for ip virulence is involved in tissue-specific recognition of virus by infected m phi, a function necessary for transcription of viral alpha genes.

Heterogeneity of BamHi DNA fragments B and E in several HSV-1 strains and recombinants

The restriction cleavage sites of the BamHI-B and BamHI-E DNA fragments of several Herpes simplex virus type 1 (HVS-1) strains were mapped. These fragments are situated at the ends of the long unique regions and share homologous sequences in the repeat components (TRL and IRL) of the genome. All the strains analyzed were found to have deletions in the Hpal-P fragment, situated in the BamHI-B fragment. Five strains were further analyzed and the deletions were located in the Smal-A fragment (within the Hpal-P fragment). The BamHI-E fragment of four recombinants (obtained by recombination between the HFEM genome and the BamHI-B fragment or part of it from the HSV-1 F strain) were almost identical but differed from another strain [NIH(LP)]. Comparison of the BamHI-B and the BamHI-E fragments of the same strain revealed that the fragments were not identical in all cases.

Genomic characterization of a poxvirus isolated from a child

A poxvirus was isolated from a six-year-old girl. The comparative analyses of the genome of this isolate (H-CP-LSax) which were carried out using the restriction endonucleases BamHI, HindIII, KpnI, MluI, NcoI, SacI, and SmaI revealed that this isolate is a member of the genus orthopoxvirus. Since the girl had never been vaccinated against smallpox, and had close contact to domestic animals, including cats, rabbits and guinea pigs, the genome of H-CP-LSax virus was genetically analysed in comparison with other known orthopoxviruses. The analysis demonstrates clearly that the HindIII cleavage pattern of H-CP-LSax DNA is different from the HindIII DNA cleavage patterns of vaccinia virus, cowpox virus, rabbit poxvirus, cat poxvirus, ectromelia virus, and okapi poxvirus. Surprisingly, it was found that the HindIII and SmaI cleavage patterns of the DNA of one out of six elephant poxviruses which were analysed under the same conditions were virtually identical to the HindIII and SmaI cleavage patterns of H-CP-LSax DNA. Although SmaI and HindIII digestion of both virus genomes gave the same fragment patterns, the viral DNAs can be distinguished from each other by the restriction endonucleases SacI, BamHI, and KpnI, which also show high similarities in the fragmentation patterns of both viruses. The results obtained in this study indicate three possibilities concerning the origin of H-CP-LSax virus. Firstly that the H-CP-LSax virus originated from an unknown animal species. Secondly, that this virus is a variant of elephant poxvirus in which the HindIII and SmaI sites are extremely conserved, and finally that H-CP-LSax can be a recombinant virus of unknown origin.

Determination of the nucleotide sequence flanking the deletion (0.762 to 0.789 map units) in the genome of an intraperitoneally avirulent HSV-1 strain HFEM

Herpes simplex virus type 1 (HSV-1) strain HFEM which harbours a deletion of 4.1 kbp in its genome (0.762 to 0.789 map units, HpaI DNA fragment P of HSV-1), is apathogenic for mice and tree shrews by the intraperitoneal application route. The exact position of this deletion was determined by DNA sequence analysis. This analysis was performed using the recombinant plasmid pU18HSHF-XmI-B which harbours the flanking genome regions (0.752 to 0.762 and 0.789 to 0.7895 map units) of the deletion in the genome of HSV-1 HFEM, and the recombinant plasmids pU18HSF-XmI-B, pU18HSF-AS, and pHSF-BB-BsH-D, harbouring particular regions of the genome of the virulent HSV-1 strain F at the coordinates 0.752 to 0.761, 0.786 to 0.790, and 0.762 to 0.771, respectively. The comparison of the DNA sequence of this region with the DNA sequences of the corresponding genome regions of the pathogenic HSV-1 strain F and HSV-1 strain 17 showed that the 5' end of the deletion in the genome of HSV-1 HFEM starts at the nucleotide position 3774 of the BamHI DNA fragment B from HSV-1/17. This position is 71 bp upstream of the UL/RL junction of the HSV-1 genome. The 3' terminus of the deletion ends at the nucleotide position 7226 of the BamHI DNA fragment B from HSV-1/17. The position is within the incomplete ninth repetitive box (ACTCC-CACGCACCCCC) and is located 36 bp upstream of the 3' end of the IE 110 mRNA.

HSV-1 virulence for mice by the intracerebral route is encoded by the BamHI-L DNA fragment containing the cell fusion gene

The phenotype of pathogenicity by direct intracerebral inoculation of herpes simplex virus type 1 (HSV-1) was mapped in the viral genome. This phenotype could be rescued by cotransfection of unit length HSV-1 DNA of an avirulent strain with the BamHI fragment L (0.70-0.738 map units) cloned from a virulent strain. The virulence function was localized in the 2.0 Kb NruI-BamHI fragment in the right-hand side of BamHI-L, the same region that encodes a virus cell-fusion gene (3). Transduction of virulence was linked with the phenotype of a larger plaque size. It is concluded that a neurovirulence function resides in the BamHI-L fragment of the HSV-1 genome, closely linked to the viral gene for cell fusion.

Nucleotide sequences important in DNA replication are responsible for differences in the capacity of two herpes simplex virus strains to spread from cornea to central nervous system

Two herpes simplex virus (HSV) intertypic recombinants were isolated with genomes composed entirely of HSV-2(186) nucleotide sequences except for a 6.0 kb segment of HSV-1(17) DNA positioned between 0.40 and 0.44 map units. Following corneal infection of mice, HSV-1(17) and the two intertypic recombinants spread from infected eyes into the central nervous system and induced a fatal encephalitis. Ocular infection with the HSV-2(186) parent did not lead to detectable amounts of virus in the brain, and none of the mice developed encephalitis. The 6.0 kb HSV-1(17) DNA inserted within the genome of the two intertypic recombinants contained nucleotide sequences involved in DNA replication. These include the HSV-1(17) oriL, the HSV-1(17) gene for DNA polymerase and portions of the HSV-1(17) gene coding for DNA-binding protein ICP8. Thus, our results indicate that the difference in the capacity of HSV-1(17) and HSV-2(186) to spread from the cornea into the CNS is determined solely by nucleotide sequences associated with DNA replication.

Rapid method for the identification and screening of herpesviruses by DNA fingerprinting combined with blot hybridization

Rapid characterization of herpesvirus isolates exemplified by equine herpesviruses is described. Total DNAs were isolated from virus infected small scale cell cultures. The DNA fragments obtained after restriction enzyme digestion were separated on agarose gels, transferred and immobilized on filter membranes. A radioactively labelled probe derived from the purified DNA of an EHV-1 reference strain was used for hybridization in order to detect the restriction fragments of different EHV-1 field isolates. This method allows the typing of many isolates within a short period of time.

Herpes simplex virus type 1 and 2 in the adrenal glands: replication and histopathology

The adrenal glands were shown to be the most severely infected organs in the early phase of HSV-1 infections (up to 10 days p.i.) after i.p. infections in mice. Virus could be isolated from the adrenal glands as early as one hour after infection with pathogenic and apathogenic strains. Infection of the adrenal glands is a result of viremia. The content of HSV-1 (5 strains) was much higher in the adrenals than in spleen and liver. It peaked at 3-4 days p.i. compared to 1-2 days in spleen and liver. Only strain 17 syn+ produced low tissue titres in the adrenal glands. Morphologic alterations by HSV-1 infections commenced with distinct foci 2 days after infection in the zona fasciculata, detected immunohistochemically by HSV-specific peroxidase-staining. Necrotic cells could be observed. The foci became confluent until day 4 and remained in this status up to day 7 p.i. During infection immunocompetent cells (macrophages, granulocytes, many T-helper--but only few T-cytotoxic/suppressor lymphocytes) could be observed. On day 10 p.i. the viral antigen had been completely eliminated. In contrast, intraperitoneal infections with 5 strains of HSV-2 resulted in infection of the adrenal glands only to a low degree. The titer of virus was low (exception: strain HG 52). This correlates well with the type of disease produced by either HSV-1 or 2. By comparing the replication of different strains of HSV-1 and 2, three types of "tropism" after i.p. infection of mice can be distinguished.

Equine herpesvirus type 1 (EHV-1) induced abortions and paralysis in a Lipizzaner stud: a contribution to the classification of equine herpesviruses

Out of 30 cases of abortion and perinatal deaths in a Lipizzaner stud in Austria 10 mares died after having shown central nervous system disturbances, ataxias and paralysis. The etiological agent of this "abortion storm" was equine herpesvirus type 1 (EHV-1). The restriction enzyme pattern of the DNA from 5 isolates recovered from fetuses has been analyzed and compared with the known reference strains of EHV-1, -2, -4 and an Austrian vaccine strain. The DNA restriction profiles of the Lipizzaner isolates as well as of the vaccine strain could be identified as being typical of abortigenic strains with minor variations. Such variations on the molecular biological level of the DNA do not justify characterization of the strains as neuro-variants. The vaccine strain differed from other isolates investigated with 4 restriction endonucleases (Bam HI, Bgl II, EcoRI, Kpn I) which was due to a deletion in the unique short segment of the genome. The lack of similar DNA bands in two EHV-1 viruses, causing mild respiratory disease, as well as in the vaccine strain Prevaccinol is suggestive of lowered virulence. In contrast to one Lipizzaner isolate tested (strain Austria IV) the Austrian vaccine strain proved to be of strong neurovirulence for suckling mice.

Replacement of the deletion in the genome (0.762-0.789 mu) of avirulent HSV-1 HFEM using cloned MluI DNA fragment (0.7615-0.796 mu) of virulent HSV-1 F leads to generation of virulent intratypic recombinant

The HFEM strain of HSV-1 is apathogenic for the tree shrew by the intraperitoneal (i.p.) route because of a deletion in the genome coordinates 0.762-0.789. Insertion of the MluI DNA fragment (coordinates 0.7615-0.789) cloned from HSV-1 strain F, which is pathogenic for the tree shrew, restored the i.p. pathogenicity to strain HFEM. The recombinant designated R-M1-C1 was highly pathogenic for the tree shrew, but slightly virulent for inbred mouse strain A. It thus appears that the viral DNA sequence involved in the i.p. pathogenicity of HSV-1 is located within the genome coordinates 0.761-0.796. This sequence is recognized differently by the cellular elements involved in HSV-1 infection in the tree shrew and the mouse.

A sequence in HpaI-P fragment of herpes simplex virus-1 DNA determines intraperitoneal virulence in mice

The virulence of herpes simplex virus-1 (HSV-1) strains by the intraperitoneal (ip) route of injection in mice depends on the presence of an intact sequence in the HpaI DNA fragment P within coordinates 0.762 to 0.787. Deletion of the HpaI-P region (e.g., strain HFEM) abrogates the ability of the virus to infect mice by the ip route without affecting pathogenicity by the intracerebral (ic) route. A recombinant virus (M1C1) derived from DNA of the HSV-1 HFEM strain and the MLUIDNA fragment (coordinates 0.761 to 0.796) spanning the HpaI-P sequence of the pathogenic strain F regained pathogenicity for mice by the ip route.

Comparative analysis of the genomes of orthopoxviruses isolated from elephant, rhinoceros, and okapi by restriction enzymes. Brief report

Orthopoxviruses from different zoo-kept mammalian species including Elephas maximus (8 isolates), Ceratotherium simum (1 isolate), and Okapia johnstoni (2 isolates) were characterized by restriction enzyme analysis of the viral genome. The four enzymes BamHI, MluI, NcoI, and SalI were found to be optimal for strain differentiation.

Investigation of the virulence genes of herpes simplex virus 2 by experimental infection in vivo with defined intertypic recombinants of a virulent HSV-2 X an avirulent HSV-1

For determination of the gene loci for virulence and tropism of herpes simplex virus 2 (HSV-2) intertypic recombinants of HSV-1 strain HFEM and HSV-2 strain 3345 were screened for their pathogenicity in the tree shrew. HSV-1 strain HFEM is not pathogenic in the tree shrew and can be recovered as a latent virus only from the spleen of the animals; but HSV-2 strain 3345, the other parental virus of the recombinants, was found to be virulent for the tree shrew and colonized the ganglia of latently infected animals. No clinical pictures were observed when the animals were inoculated with HSV recombinants RS1(3), RB2(3), RB2(8), RB2(9), RB2(10), RB5(2), RB7(3), and RB7(7). It was found, however, that HSV recombinant RB5(0) is pathogenic for the tree show. Studies of the state of viral latency in the animals infected with these recombinants revealed that only HSV recombinant RB5(0) was able to persist as latent virus in the spleen of latently infected animals. The genome of recombinant HSV-RB5(0) contains DNA sequences of HSV-2 strain 3345 with two interruptions at 0.22-0.33 and 0.54-0.59 viral map units. In these regions of HSV-RB5(0), DNA sequences of HSV-strain HFEM at 0.26-0.33 and about 0.57-0.58 viral map units, respectively, had been recombined. The results obtained in this study indicate that the recombinant HSV-RB5(0) acquired the virulent phenotype (v+) from parental virus HSV-2 strain 3345 but lost the phenotype for colonizing the ganglia (g+). Furthermore, it acquired the phenotype of parental virus HSV-1 strain HFEM for persisting in a latent state only in the spleen (s+ and g-) of the latently infected animals.

Pseudorabies virus avirulent strains fail to express a major glycoprotein

The unique short (Us) region of the pseudorabies virus (PRV) genome, which displays high transcriptional activity during the late phase of infection and has been found to code for glycoproteins, is partially deleted in the genomes of three vaccine strains (A57, Norden, and NIA-4). This deletion is located in the SalI subfragment 7A of BamHI fragment 7. To identify possible viral gene products involved in PRV virulence, we investigated the transcriptional and translational pattern of the deleted part of the Us region. Northern blots demonstrated that one major RNA species (3.8 kilobases) transcribed from fragment 7A was missing in the vaccine strains, whereas other transcripts were altered. Radioimmunoprecipitation of in vivo-labeled PRV glycoproteins and of in vitro-translated polypeptides with hyperimmune serum and monoclonal antibodies indicated a lack of glycoprotein gI. Hybrid-selection experiments with subcloned DNA fragments confirmed the absence of gI and of a 40,000-molecular-weight polypeptide. We suggest that both viral proteins are involved in the expression of PRV virulence.

Mapping of the deletion in the genome of HSV-1 strain HFEM responsible for its avirulent phenotype

To determine the exact map position of the deletion in the genome of HSV-1 strain HFEM, the Bam HI DNA fragment B of the HSV-1 strains HFEM, F, and of HSV-R-HFehx-C19 were cloned in the Bam HI site of the bacterial plasmid vector pAT153 and analysed in detail. Analysis of the insert of the three recombinant plasmids harbouring the Bam HI DNA fragment B of HSV-1 strain F (pHSF-B-B), HSV-1 strain HFEM (pHSHF-B-B), and recombinant HSV-R-HFehx-C19 (pHSR19-B-B) was performed using a variety of restriction enzymes and Southern blot hybridization. These comparative studies revealed that the HpaI DNA fragment P of the intact viral genome of HSV-1 strain F is not present in the genome of HSV-1 strain HFEM, indicating that the deletion in HSV-1 strain HFEM corresponds to this fragment, which spans the coordinates 0.762 to 0.790 of the HSV-1 DNA. The size of the deletion was found to be 4.1 kbp, corresponding to 2.7 Md.