Efficacy of the herpes simplex virus types 1 and 2 mutant viruses to confer protection against zosteriform spread in mice

Two mutant viruses, HSV-2 XD192 and HSV-1 1716, failed to generate zosteriform lesions when injected in high dose into BALB/c and C3H mice. Mice exposed to mutant viruses were solidly immune to challenge by wild-type homologous or heterologous virus. However, at lower immunizing doses protection was evident against lethality, but not skin lesions, especially in the case of mutant XD192. Protection could be conferred with lymphoid cells from mutant virus immune mice and again, protection against lethality was more frequent than prevention of skin lesions. On the basis of cell fractionation studies, protection against lethality was assumed to be principally the function of CD8+ T lymphocytes. The implications of the results in terms of vaccine development were briefly discussed.

A HSV-1 variant (1720) generates four equimolar isomers despite a 9200-bp deletion from TRL and sequences between 9200 np and 97,000 np in inverted orientation being covalently bound to sequences 94,000-126,372 np

The genome structure of a spontaneously generated HSV-1 strain 17 variant, 1720, has been determined by restriction endonuclease and Southern blot analysis. The short segment of 1720 is unaltered compared to the parental strain 17 genome, whereas the long segment is extensively rearranged. Almost all of TRL (approximately 9.2 kb) has been deleted and consequently IRL is converted into unique sequence. Sequences from approximately 9200 nucleotide position (np) to 97,000 np are present in inverted orientation, covalently bound to sequences in the prototype orientation from approximately 94,000 np to the L/S junction at 126,372 np. Thus, sequences from 94,000 np to 97,000 np are now diploid, with one copy in the normal orientation and location, and the other at the long terminus as an inverted repeat; no inversion of the intervening unique sequences occurs about this novel inverted repeat. In contrast, normal inversions of the long and short segments occur to give four equimolar genomic isomers, indicating that the novel long terminus has gained an "a" sequence. The duplication of sequences between 94,000 np and 97,000 np results in a genome containing two copies of UL43 and one complete and one partial copy each of genes UL42 and UL44 encoding the 65 kD DNA-binding protein and glycoprotein C, respectively. The variant has been shown to grow normally in vitro following high multiplicity infection.

Peripheral replication and latency reactivation kinetics of the non-neurovirulent herpes simplex virus type 1 variant 1716

The terminal portion of the herpes simplex virus (HSV) genome long repeat region has been shown to contain a neurovirulence gene. Both HSV-1 and HSV-2 mutants deleted in this gene fail to cause central nervous system (CNS) disease in mice. The HSV-1 strain 17 variant 1716, which has a 759 bp deletion encompassing the gene, grows normally in tissue culture but fails to grow following intracerebral inoculation of mice. This paper demonstrates that 1716 is capable of peripheral replication in the footpads of mice. However, no acute replication of virus is detectable in dorsal root ganglia up to 10 days after footpad inoculation. These results imply that the replication defect in 1716 is not host-specific, but is tissue- and/or cell type-specific. Latency reactivation kinetics demonstrate that 1716 is capable of establishing a latent infection, but the kinetics of reactivation are significantly impaired compared to wild-type virus and are dose-dependent. Lack of acute ganglionic replication combined with impaired reactivation kinetics support the conclusion that a proportion of 1716 genomes initiate a lytic infection which then aborts, and a proportion enter the latent state. The results with 1716 imply that its inability to replicate in CNS and peripheral nervous system neurons is specific, and that the block in replication is beyond the stage of adsorption and entry. A prerequisite for any live attenuated HSV vaccine is an inability to initiate CNS involvement following peripheral inoculation. In this respect, 1716 has prototype vaccine potential with the proviso that a direct extrapolation is being made from mouse to man.

Analysis of intrastrain recombination in herpes simplex virus type 1 strain 17 and herpes simplex virus type 2 strain HG52 using restriction endonuclease sites as unselected markers and temperature-sensitive lesions as selected markers

The viral and host factors involved in herpes simplex virus (HSV) recombination are little understood. To identify features of the process, recombination in HSV-1 and HSV-2 has been studied by analysing the segregation of unselected markers in the form of restriction endonuclease (RE) sites. By confining parental interactions to only one strain of virus of each serotype, restrictions imposed by non-homology are overcome and differential growth phenotypes can be discounted. The analysis of unselected and selected recombinants using RE sites in conjunction with temperature-sensitive mutations is consistent with (i) HSV being highly recombinogenic, (ii) parental and progeny molecules taking part in the process, (iii) the four genomic isomers participating in recombination, (iv) genome alignment being part of the recombination process and (v) cellular factors in conjunction with genome homology influencing the efficiency of recombination.

Setting up an 'EPO' system. Management of patients receiving recombinant human erythropoietin

As more people with end stage renal disease are treated with erythropoietin for their anaemia, a well-coordinated system is essential to monitor their response to treatment. This is best achieved by keeping management of the system in the hands of one or two people.

In vivo and in vitro reactivation impairment of a herpes simplex virus type 1 latency-associated transcript variant in a rabbit eye model

Many recent studies of latent herpes simplex virus type 1 (HSV-1) infections within the nervous system have focused on the diploid genes encoding the latency-associated transcripts (LATs). The impaired explant reactivation of LAT variants from mouse trigeminal ganglia has implicated the LATs in the efficiency or speed of the reactivation process (D. A. Leib, C. L. Bogard, M. Kosz-Vnenchak, K. A. Hicks, D. M. Coen, D. M. Knipe, and P. A. Schaffer, J. Virol. 63:2893-2900, 1989; I. Steiner, J. G. Spivack, R. P. Lirette, S. M. Brown, A. R. MacLean, J. H. Subak-Sharpe, and N. W. Fraser, EMBO J. 8:505-511, 1989). However, it is not known how closely explant reactivation mimics the reactivation process in vivo. In the current study, a LAT variant (1704), parental strain (17+), and rescuant (1704R) were compared in vivo for reactivation of latent infection by iontophoresis in the rabbit eye model and in vitro by explant cocultivation of trigeminal ganglia from rabbits. Following iontophoresis, 17+ and 1704R reactivated in vivo from 76 and 64% of rabbits, respectively, while 1704 reactivated only from 4% (1 of 25) of the animals. In explant reactivation experiments, 17+ and 1704R reactivated from 98 and 67% of rabbit trigeminal ganglia, while 1704 reactivated from only 28% of trigeminal ganglia. The mean time required for the appearance of reactivated 1704 in explant culture, 17 days, was significantly longer than for 17+ and 1704R, 8 to 9 days. Thus, the explant reactivation kinetics in rabbit trigeminal ganglia reflect the behavior of LAT variant 1704 in vivo in the rabbit eye model. These data support the role of the LATs in the reactivation process and support the hypothesis that explant reactivation is a suitable system for analyzing the biological behavior of HSV-1 variants with defined genetic alterations in the LAT gene.

Abolition of the RL neurovirulence phenotype of herpes simplex virus type 2 strain HG52 does not require deletion of the DR1 element of the 'a' sequence

We have characterized a spontaneous variant of herpes simplex virus type 2 (HSV-2) strain HG52, 2616, which has 786 bp of both copies of RL deleted, but which retains 782 bp upstream of the 5' end of immediate early gene 1 and 463 bp downstream of the 'a' sequence. Variant 2616 is avirulent following intracerebral inoculation of BALB/c mice, thus showing in vivo characteristics similar to those of variant 2604, described previously (a 1488 bp deletion incorporating the DR1 element of the 'a' sequence), but not to those of variant 2701, which has an intermediate neurovirulence phenotype. The deletions in variants 2616 and 2604 remove the conserved HSV-1 and -2 RL open reading frame entirely and extend downstream from it, whereas the deletion in variant 2701 removes only the 5' part. The data show that deletion of part of the 'a' sequence is not required for the production of the RL avirulence phenotype in HSV-2 strain HG52.

Sequence analysis of the herpes simplex virus type 1 strain 17 variants 1704, 1705 and 1706 with respect to their origin and effect on the latency-associated transcript sequence

The precise endpoints of the deletions/insertions in three variants (1704, 1705 and 1706) of herpes simplex virus type 1 (HSV-1) strain 17 have been determined by dideoxynucleotide sequence analysis. The analysis was undertaken to discover whether the three variants had arisen from the same initial event and the extent of the deletions with respect to the latency-associated transcripts (LATs) and the proposed LAT promoter region. It is not possible from the deletion boundaries to determine unequivocally whether the three variants had arisen from the same recombination event although 1706 could be descended from 1705 by illegitimate recombination. The results demonstrate that spontaneous deletions can occur at random within RL, the extent of the deletions in UL is constrained by the essential nature of UL genes in vitro but is otherwise arbitrary and deletions in 1704 completely remove both copies of the LAT promoter region and in IRL extend into the 5' end of the LAT sequence.

The RL neurovirulence locus in herpes simplex virus type 2 strain HG52 plays no role in latency

We have demonstrated that the variant JH2604 of the herpes simplex virus type 2 (HSV-2) strain HG52 is completely avirulent in BALB/c mice following intracranial inoculation, with an LD50 of greater than 10(7) p.f.u./mouse compared to the wild-type LD50 of less than 10(2) p.f.u./mouse. In JH2604, a 1.5 kbp deletion extends from the DR1/Ub junction of the 'a' sequence to 511 bp upstream of the 5' end of IE1 in both long repeats. We have since constructed a second variant (2701) in which only 850 bp are removed from the RL. This deletion lies entirely within the sequences deleted in JH2604 and leaves intact most of a short 189 bp open reading frame (ORF) highly conserved between HSV-1 and HSV-2. Like JH2604, 2701 shows wild-type growth characteristics and is neither host range- nor temperature-restricted. This was most noteworthy in the case of mouse 3T6 cells. 2701 has an LD50 of 5 x 10(5) p.f.u./mouse on intracranial inoculation, a value intermediate between those of HG52 and JH2604. In assays for intracranial replication, JH2604 exhibits no detectable growth with a rapid decline in virus titre, 2701 shows limited growth over the first 24 to 36 h post-inoculation before the titre again declines and HG52 grows rapidly, reaching a high titre until the mice die. Taken together these results suggest that a region of the genome upstream of IE1 encodes a gene product essential for HSV replication in neurons of the central nervous system. It is highly likely that the conserved ORF is in an important region of a polypeptide essential for neurovirulence, although the upstream sequences present in 2701 but absent from JH2604 must also play a role. Although JH2604 and 2701 are avirulent, they both establish latent infection in the dorsal root ganglia of BALB/c mice and reactivate in vitro in a manner indistinguishable from HG52. This suggests a distinct separation of the factors involved in neurovirulence and the establishment of/reactivation from latency.

Herpes simplex virus type 1 deletion variants 1714 and 1716 pinpoint neurovirulence-related sequences in Glasgow strain 17+ between immediate early gene 1 and the 'a' sequence

Dideoxynucleotide sequence analysis of a spontaneously isolated deletion variant (1714) of Glasgow strain 17+ of herpes simplex virus type 1 (HSV-1) demonstrates that the deletion is 759 bp in length and is located within each copy of the BamHI s fragment (0 to 0.02 and 0.81 to 0.83 map units) of the long repeat region of the genome. The deletion removes one complete copy of the 18 bp DR1 element of the 'a' sequence and terminates 1105 bp upstream of the 5' end of immediate early (IE) gene 1. The variant grows to high titre, is not temperature-sensitive and is not host cell type-restricted in vitro. In vivo studies demonstrate that 1714 is totally avirulent for BALB/c mice following intracerebral inoculation, with an LD50 of 7 x 10(6) p.f.u./mouse compared to less than 10 p.f.u./mouse for the parental wild-type strain 17+. In vivo growth kinetics show that the non-neurovirulent phenotype is due to an inability to replicate in mouse brain. Because 1714 was in a genomic background in which the four XbaI sites had been removed and because the phenotype was thymidine kinase-negative, the 759 bp deletion was introduced into an otherwise totally wild-type background. The resulting variant (1716) is non-neurovirulent for mice, with an LD50 of 7 x 10(6) p.f.u./mouse. The deletion does not prevent the virus from establishing a latent infection or reactivating from it in vitro. The results demonstrate that sequences between IE-1 and the 'a' sequence produce neurovirulence in Glasgow strain 17+ and, in conjunction with the non-neurovirulence of the HSV-2 HG52 variant JH2604, identify a common function conserved in HSV-1 and -2.

Structure and expression of cytosolic cyclophilin/peptidyl-prolyl cis-trans isomerase of higher plants and production of active tomato cyclophilin in Escherichia coli

cDNA clones encoding proteins of approximately 18 kDa in which 83% of the amino acids are conserved relative to the published sequences of mammalian cyclophilin/rotamase (CyP) have been isolated from tomato, maize, and Brassica napus. In correspondence with the mammalian genes, but in contrast with the Neurospora gene and one yeast CyP gene, the plant CyP genes encode only mature proteins lacking transit peptides. RNA blot analyses demonstrate that CyP genes are expressed in all plant organs tested. Southern blots of genomic DNA indicate that there are small families (two to eight members) of CyP-related genes in maize and B. napus. A vector was constructed for expression of the tomato cDNA in E. coli. SDS/polyacrylamide gels show that extracts of appropriately induced cells harboring this vector contain nearly 40% of the protein as a single approximately 18-kDa band. While the majority of this protein is sequestered in insoluble inclusion bodies, the soluble extracts have higher levels of peptidyl-prolyl cis-trans isomerase (rotamase) activity than extracts of wild-type cells. This additional activity is sensitive to inhibition by the cyclic undecapeptide cyclosporin A.

Intrauterine spermatic cord torsion in the newborn: sonographic and pathologic correlation

In five newborn patients with spermatic cord torsion, sonography demonstrated an enlarged and globular testis, hydrocele, and skin thickening. In four of these patients the testicular parenchyma was heterogeneous. Peripheral hypoechoic areas were seen in two of the four patients; the other two had a central hypoechoic region and a peripheral echogenic rim. The testis in the fifth patient was diffusely hyperechoic. Duplex Doppler sonography performed in two patients failed to demonstrate any signal in the spermatic cord in either the abnormal or contralateral hemiscrotum. Scintigraphic findings were positive for testicular torsion in two patients and equivocal in three patients. Surgery was performed 2-12 days after sonography and established the diagnosis of spermatic cord torsion. Pathologic examination demonstrated hemorrhagic infarction of the entire testis as well as scattered calcifications. The authors conclude that a solid globular testicular mass seen during the neonatal period is suggestive of intrauterine spermatic cord torsion.

Multigenic control of virus virulence in intertypic recombinants of herpes simplex virus

The virulence of herpes simplex virus (HSV) type 1 x type 2 intertypic recombinants was determined following infection of corneas of outbred New Zealand White rabbits. None of the four recombinants was as virulent for rabbits as type 1 parent. All the four recombinants having an insert of type 2 virus genome between 0.35 and 0.576 map units (m.u.) and/or 0.82 and 1.00 m.u. exhibited intermediate virulence between their type 1 and type 2 parents. The results indicate that intertypic recombinants are moderated in their virulence independent of their parental virulence and therefore there exists a multigenic control of HSV virulence.

Peri-operative anxiety in patients undergoing extracorporeal piezolithotripsy

Twenty-four patients undergoing extracorporeal piezolithotripsy took part in this study and underwent treatment on a Wolf Piezolith 2300 Lithotripter, which does not require any type of anaesthesia and enables the patient to be treated as an out-patient. Previous work has investigated anxiety states of patients during investigative procedures and found that information given prior to the procedure is beneficial in reducing the levels of anxiety reported. Modern urological surgery carried out to remove kidney stones has progressed to non-invasive techniques with the introduction of extracorporeal piezolithotripsy (EPL). However, little work has examined the patient's reaction to this new procedure. Since patients undergoing EPL are awake throughout the procedure, it is possible to perform continuous assessment of anxiety by measurement of palmar sweat. The results demonstrated significantly increased levels of palmar sweat throughout treatment, with a return to pre-treatment levels afterwards. This was demonstrated by just under 50% (n = 10) of patients who appeared to be agitated during treatment, and by the comments made by patients about their treatment. One-third of patients (n = 8) described pain as far more severe than had been anticipated when asked if they could identify a cause for anxiety. It is recommended that adequate patient preparation and education prior to the procedure should be provided, but that such education must also include a warning that some discomfort may occur.

Quantitative measurement of anxiety in patients undergoing surgery for renal calculus disease

The anxiety experienced by patients undergoing surgical procedures is well documented and may affect the outcome of any operation. This has not been considered in modern urological surgery which is moving away from highly-invasive techniques towards minimal and even non-invasive procedures. Little work has been carried out to examine the patient's reaction to this new technology. This work has two aims: to assess patient anxiety before and after different procedures for renal calculus removal and to identify, where possible, factors that contribute to pre- and post-operative anxiety. The main method of quantifying stress was the measurement of palmar sweat by means of an evaporimeter. Other measurements used were a bi-polar visual analogue scale and the Spielberger State Anxiety Questionnaire. The results of the study demonstrated a highly significant reduction in the palmar sweat production (P less than 0.0001) and score obtained for the analogue scale (P less than 0.05) following open surgery, but no changes before and after treatment in any of the variables in patients undergoing percutaneous nephrolithotomy or lithotripsy. Analysis of the data in relation to the surgery demonstrated a significantly higher preoperative analogue score in patients undergoing open surgery compared with lithotripsy (P less than 0.05). Post-operatively, patients undergoing lithotripsy had a significantly higher palmar sweat response compared with patients undergoing open surgery (P less than 0.01). Pre-operatively, fear of a general anaesthetic was identified as a factor contributing to anxiety and post-operatively, pain was the most commonly identified stressor. The implications of these results to the patient and to both nursing and medical staff in terms of practice are discussed. This must include a careful pre-operative explanation.

The JH2604 deletion variant of herpes simplex virus type 2 (HG52) fails to produce necrotizing encephalitis following intracranial inoculation of mice

The pathological changes and distribution of virus antigen in mouse brains were studied following intracranial inoculation of 3 week old BALB/c mice with the herpes simplex virus (HSV) type 2 strain HG52 and its deletion variant JH2604. The variant JH2604 failed to produce necrotizing encephalitis compared to the parental HG52. The morphological changes induced in JH2604-infected brains consisted of localized perivascular cuffing by lymphocytes and infiltration by immune cells. Immunohistochemical studies using polyclonal anti-HSV serum showed that JH2604 antigens were localized at the site of inoculation with no evidence of neuronal involvement. Wild-type HSV-infected brains demonstrated a wide distribution of antigens both in neuronal and supporting cells. These data provide evidence that the non-neurovirulent phenotype of JH2604 is due to inability to replicate within neuronal cells of the central nervous system and pinpoints a precise role for the HG52 sequences contained within the 1488 bp subfragment of TRL/IRL deleted in JH2604.

Herpes simplex virus genes controlling reactivation from latency in rabbit eye model

Using the rabbit eye model of latency, herpes simplex virus type 1 strain McKrae invariably reactivated after epinephrine iontophoresis, whereas type 2(HSV-2) virus strain HG 52 failed to reactivate. Both strains established a latent infection with the same frequency. To identify the viral genes involved in this reactivation difference, intertypic recombinants were selected following cotransfection of intact McKrae DNA and Xba I or Hpa I cleaved HG52 DNA. Eleven separately obtained recombinants containing HG52 inserts between 0.35-0.56 and/or 0.82-1.0 map units (mu) were isolated but as four that were tested reactivated with the same frequency as the parental Mckrae virus, it was established that the genes encoded between these map coordinates do not determine the reactivation difference.

A herpes simplex virus type 1 variant, deleted in the promoter region of the latency-associated transcripts, does not produce any detectable minor RNA species during latency in the mouse trigeminal ganglion

In peripheral sensory ganglia latently infected with herpes simplex virus type 1 (HSV-1) transcription is restricted. A set of viral latency-associated transcripts, the LATs, have been characterized by Northern blotting and in situ hybridization. These transcripts have previously been mapped to a 3 kb region of the viral genome within the repeat long region. However, transcription from adjacent regions of the genome can be detected by in situ hybridization, which cannot be detected by Northern blotting. These RNAs are termed minor LATs or m-LAT. In this study we show that in ganglia latently infected with the HSV-1 variant 1704, which is deleted in one complete copy of the LAT gene and in the promoter and 5' portion of the other copy, m-LATs are not detected by in situ hybridization. Furthermore, the levels of DNA in nervous system tissue latently infected with the parental and the 1704 variant virus are similar. Thus we propose that the sequence elements necessary for initiating transcription or stabilizing m-LATs are within the region deleted in variant 1704 that codes for the promoter and the 5' end of the LATs.

Characterization of a gene family abundantly expressed in Oenothera organensis pollen that shows sequence similarity to polygalacturonase

We have isolated and characterized cDNA clones of a gene family (P2) expressed in Oenothera organensis pollen. This family contains approximately six to eight family members and is expressed at high levels only in pollen. The predicted protein sequence from a near full-length cDNA clone shows that the protein products of these genes are at least 38,000 daltons. We identified the protein encoded by one of the cDNAs in this family by using antibodies to beta-galactosidase/pollen cDNA fusion proteins. Immunoblot analysis using these antibodies identifies a family of proteins of approximately 40 kilodaltons that is present in mature pollen, indicating that these mRNAs are not stored solely for translation after pollen germination. These proteins accumulate late in pollen development and are not detectable in other parts of the plant. Although not present in unpollinated or self-pollinated styles, the 40-kilodalton to 45-kilodalton antigens are detectable in extracts from cross-pollinated styles, suggesting that the proteins are present in pollen tubes growing through the style during pollination. The proteins are also present in pollen tubes growing in vitro. Both nucleotide and amino acid sequences are similar to the published sequences for cDNAs encoding the enzyme polygalacturonase, which suggests that the P2 gene family may function in depolymerizing pectin during pollen development, germination, and tube growth. Cross-hybridizing RNAs and immunoreactive proteins were detected in pollen from a wide variety of plant species, which indicates that the P2 family of polygalacturonase-like genes are conserved and may be expressed in the pollen from many angiosperms.

The herpes simplex virus type 2 (HG52) variant JH2604 has a 1488 bp deletion which eliminates neurovirulence in mice

The herpes simplex virus type 2 (HG52) deletion variant JH2604 is avirulent (LD50 greater than 10(7) p.f.u./mouse) for mice compared to the parental wild-type virus (LD50 less than 10(2) p.f.u./mouse) and fails to replicate in vivo. JH2604 has a 1488 bp deletion within the 3 kb BamHI v fragment (0 to 0.02 and 0.81 to 0.83 map units) which removes one copy of the 17 bp direct repeat DR1 element of the 'a' sequence and terminates 522 bp upstream of the 5' end of the immediate early gene 1. In vivo selection after transfection of intact JH2604 DNA with the BamHI g (v + u) joint fragment of HG52 results in the isolation of wild-type virus with an LD50 of less than 10(2) p.f.u./mouse. These results show that a 1488 bp sequence within the terminal portion of the genome long repeat region confers neurovirulence on strain HG52.

A herpes simplex virus type 2 variant in which a deletion across the L-S junction is replaced by single or multiple reiterations of extraneous DNA

We have isolated and characterized a novel variant of herpes simplex virus type 2 (HSV-2) strain HG52 which has a deletion of 13.5 kb across the L-S junction of the genome, resulting in all of the IRL region, half of the IRS region and the intervening L-S junction 'a' sequence(s) being removed. The deleted DNA has been replaced by single or multiple (up to 14) reiterations of a DNA sequence approximately 1 kb in length. Individual genomes within the population range in size from approximately 12 kb smaller than unit length to unit length or marginally larger. The L component of the genome is fixed in the prototype orientation while the S component inverts inefficiently. The variant is viable in tissue culture, is not temperature-sensitive, demonstrates impaired single-cycle growth characteristics and, apart from altered mobility of a single species (29.5K), its polypeptide profile in infected cells appears normal. Southern blot analysis has failed to identify the inserted sequences as being derived from HSV-2.

Analysis of unselected HSV-1 McKrae/HSV-2 HG 52 recombinants demonstrates preferential recombination between intact genomes and restriction endonuclease fragments containing an origin of replication

To identify viral genes involved in reactivation of herpes simplex virus from latency, intertypic HSV-1 strain McKrae/HSV-2 strain HG 52 recombinants were selected following cotransfection of intact McKrae DNA and XbaI or HpaI cleaved HG 52 DNA. Eleven separately obtained recombinants containing HG 52 inserts between 0.35-0.56 and/or 0.82-1.0 map units (mu) were isolated. It was noted that with HpaI digested HG 52 DNA, only recombinants containing type 2 inserts from HpaI d (0.35-0.57) and/or containing an intact type 2 [S] region were isolated. Similarly with XbaI cleaved HG 52 DNA only recombinants containing type 2 sequences from XbaI c (0-0.45) were isolated. In effect, the type 2 insert always contained one or both origins of replication (ORIL/ORIS). In reciprocal experiments isolation of two recombinants from cotransfection of HpaI cleaved McKrae DNA with intact HG 52 DNA confirmed this finding; one contained both copies of ORIS and the intervening short region sequences of McKrae, the other contained approximately 3 kb of McKrae in which ORIL is located. These results indicate that either (a) the presence of an origin of replication in a RE fragment amplifies the fragment thereby increasing its concentration and hence recombination potential with intact genomes; and/or (b) recombination and replication may be correlated. In either case isolation of recombinants containing ORIL and ORIS from the restricted DNA parent strongly suggests that both origins are functional in vitro.

A variant of herpes simplex virus type 2 strain HG52 with a 1.5 kb deletion in RL between 0 to 0.02 and 0.81 to 0.83 map units is non-neurovirulent for mice

The virulence of a deletion variant of herpes simplex virus type 2 (HSV-2) strain HG52 has been determined by intracranial inoculation of 3-week-old BALB/c mice. The variant JH2604 has a 1.5 kb deletion within each copy of the long repeat region (RL) of the genome between 0 to 0.02 and 0.81 to 0.83 map units. JH2604 is avirulent for mice compared to the parental wild-type virus, and fails to replicate in mouse brain in vivo. Correction of the deletion by marker rescue resulted in the isolation of recombinants which gave LD50 values comparable to those of individual plaque stocks of the parental HG52. Introduction of the deletion into wild-type virus resulted in recombinants which on intracranial inoculation of mice were avirulent. The results imply that sequences within the 3 kb terminal portion of RL are required for virulence of HSV-2 strain HG52.