Assessment In Vitro of a Novel Therapeutic Strategy for Glioma, Combining Herpes Simplex Virus HSV1716-mediated Oncolysis with Gene Transfer and Targeted Radiotherapy

Genetically engineered herpes simplex virus ICP34.5 null mutants replicate only in dividing cells and have shown potential for the treatment of malignant disease, including glioma. Phase I trials have demonstrated the safety of these viruses in various clinical settings but it is envisaged that for full efficacy they will be used in combination with other therapeutic modalities. To enhance virus-induced tumour cytotoxicity, we have engineered an ICP34.5 null mutant (HSV1716) of HSV1 which expresses the noradrenaline transporter gene (NAT). This virus is designated HSV1716/NAT. We have shown previously that introduction of the NAT gene into a range of tumour cells, via plasmid-mediated transfection, conferred the capacity for active uptake of the radiopharmaceutical [131I]MIBG and resulted in dose-dependent toxicity. In this study, combination therapy utilising HSV1716/NAT and [131I]MIBG was assessed in vitro by the MTT assay. We demonstrate that the NAT gene, introduced by HSV1716/NAT into cultured glioma cells, was expressed 1 h after viral infection, enabling active uptake of [131I]MIBG. The combination of viral oncolysis and induced radiopharmaceutical uptake resulted in significantly enhanced cytotoxicity compared to either agent alone and the response was dose- and time-dependent. These studies show that the combination of oncolytic HSV therapy with targeted radiotherapy has the potential for effective tumour cell kill and warrants further investigation as a treatment for malignant glioma.

HSV1716 injection into the brain adjacent to tumour following surgical resection of high-grade glioma: safety data and long-term survival

Following standard treatment, the prognosis remains poor in patients with high-grade glioma and new therapies are urgently required. Herpes simplex virus 1716 (HSV1716) is an ICP34.5 null mutant that is selectively replication competent and shown to be safe and to replicate following injection into high-grade glioma. We demonstrate that following surgical resection, HSV1716 is safe when injected into the brain adjacent to excised tumour. In all, 12 patients with recurrent or newly diagnosed high-grade glioma underwent maximal resection of the tumour. HSV1716 was injected into eight to 10 sites around the resulting tumour cavity with the intent of infecting residual tumour cells. As clinically indicated, patients proceeded to further radiotherapy or chemotherapy. There has been no clinical evidence of toxicity associated with the administration of HSV1716. Longitudinal follow-up has allowed the assessment of overall survival compared to that of similar patients not treated with HSV1716. Three patients remain alive and clinically stable at 15, 18 and 22 months postsurgery and HSV1716 injection. Remarkably, the first patient in the trial, who had extensive recurrent disease preprocedure, is alive at 22 months since injection of HSV1716 and 29 months since first diagnosis. Imaging has demonstrated a reduction of residual tumour over the 22-month period despite no further medical intervention since the surgery and HSV1716 injection. In this study, we demonstrate that on the basis of clinical observations, there has been no toxicity following the administration of HSV1716 into the resection cavity rim in patients with high-grade glioma. The survival and imaging data, in addition to the lack of toxicity, give us confidence to proceed to a clinical trial to demonstrate efficacy of HSV1716 in glioma patients.

Up-regulation of a growth arrest and DNA damage protein (GADD34) in the ischaemic human brain: implications for protein synthesis regulation and DNA repair

GADD34 is a growth arrest and DNA damage inducible gene up-regulated in response to DNA damage, cell cycle arrest and apoptosis. It is thought that GADD34 may play a crucial role in cell survival in ischaemia. GADD34 expression was assessed immunohistochemically in post-mortem human hippocampal tissue obtained from patients surviving for defined periods (0-24 h; 24 h-7 days) after a cardiac arrest and in age-matched control subjects. In control brain, cytoplasm staining in GADD34 immunopositive cells was faint but present throughout the hippocampus and cortex. There was minimal change in GADD34 expression in the group surviving 0-24 h after cardiac arrest. However GADD34 immunostaining was markedly increased in selectively vulnerable regions in the 24 h-7 day survival group. Increased GADD34 staining was present in ischaemic neurones and in some morphologically normal neurones after cardiac arrest. Extensive ischaemic damage was found to correlate with elevated GADD34 immunostaining in the CA1 layer of the hippocampus (**P < 0.0016). In addition, GADD34 was found to colocalize with proliferating cell nuclear antigen in some neurones. The up-regulation of GADD34 in response to global ischaemia in the human brain plus its influence on protein synthesis and DNA repair suggests that this protein may have the potential to influence cell survival.

HSV Growth, Preparation, and Assay

Whether herpes simplex virus (HSV) is viewed as a pathogen or as a model eukaryotic system, it is virtually certain that any experimental work will require the virus to be grown and assayed. The following chapter is therefore seen as the fundamental first step before embarking on more intellectually and technically challenging technology. Its importance should not however be underestimated. It never fails to surprize us that people who describe themselves as virologists have little understanding of the basic requirements needed to attain a contamination-free, high-titer, low particle:plaque-forming units (PFU) ratio, genetically pure virus stock.

HSV1716 persistence in primary human glioma cells in vitro

HSV1716 is a selectively replication competent mutant of herpes simplex virus which is in trial in glioma patients. We have demonstrated that HSV1716 is non-toxic when delivered into tumour or into brain adjacent to tumour, yet replicates within tumour cells. Tumour tissue, from one patient treated 2.5 years previously with intra-tumoural HSV1716, was put into culture. The cultured cells were shown to be glial in origin with no evidence of residual HSV1716. These cells were subsequently infected at a MOI of 0.1 with either HSV1716 or wild-type HSV17(+). The HSV17(+) infected cells were completely rounded up or lysed within 72 h. Although the cells supported HSV1716 replication and also became rounded or lysed, a proportion (approximately 20%) remained viable. These cells continued to divide and shed low levels of HSV1716 up to 31 days after infection when there was evidence of rapid virus replication resulting in complete cell lysis. These data demonstrate that HSV1716 can 'persist' in human glioma cells at least in vitro and gives credence to the possibility that in tumours in vivo a similar phenomenon may take place. If this were the case, then HSV1716 has the potential to kill tumour cells over a prolonged period of time.

Specific expression of the cell cycle regulation proteins, GADD34 and PCNA, in the peri-infarct zone after focal cerebral ischaemia in the rat

Cell cycle proteins play key roles in cell survival or death under pathological conditions. Expression of growth arrest and DNA damage-inducible protein, GADD34 and proliferating cell nuclear antigen (PCNA) have been investigated in the core and peri-infarct zone at 2 and 24 h after middle cerebral artery occlusion (MCAO). At these times after MCAO, numerous GADD34-positive cells were present, particularly in the peri-infarct zone (e.g. 24 +/- 4 and 52 +/- 6 immunopositive cells/0.25 mm2 at 2 and 24 h, respectively, in cortex). PCNA-immunopositive cells were barely detectable in the peri-infarct zone at 2 h; however, numerous PCNA-immunopositive cells were present in this zone by 24 h (0.7 +/- 0.3 and 10.6 +/- 1.5 immunopositive cells/0.25 mm2, respectively) as well as in the adjacent cortex and in the contralateral cingulate cortex. Most GADD34-immunopositive cells coexpressed the neuronal marker Neu-N with a smaller number coexpressing the microglial marker, Mrf-1. Evidence of morphologically 'abnormal' and 'normal' GADD34 immunopositive neurons was found within the peri-infarct zone. The majority of PCNA immunopositive cells were Mrf-1 positive with a smaller number Neu-N positive. Double-labelling revealed colocalization of GADD34 and PCNA in some cells within the peri-infarct zone and in the ependymal cells lining the ventricles. The presence of GADD34 and PCNA in a key anatomical location pertinent to the evolving ischaemic lesion indicates that GADD34, either alone or in combination with PCNA, has the potential to influence cell survival in ischaemically compromised tissue.

The potential for efficacy of the modified (ICP 34.5(-)) herpes simplex virus HSV1716 following intratumoural injection into human malignant glioma: a proof of principle study

We have previously demonstrated the safety of intratumoural administration of the selectively replication-competent herpes simplex virus mutant HSV1716 in patients with high-grade glioma (HGG). Here we show its potential for efficacy by demonstrating that the virus survives and replicates when injected into the tumours of patients. Since HSV replication is a cytolytic process it must result in tumour cell killing. Twelve patients with biopsy-verified HGG received an intratumoural injection of 10(5) plaque-forming units (p.f.u.) of HSV1716. Four to 9 days after inoculation, tumours were removed and assayed for evidence of viral replication. In two patients, HSV1716, in excess of the input dose was recovered from the injection site. HSV DNA was detected by PCR at the sites of inoculation in 10 patients and at distal tumour sites in four. HSV-specific antigen was detected in tumour tissue from two patients. In five patients an immunological response to HSV1716, as detected by changes in levels of IgG and IgM, was demonstrated. This study demonstrates that HSV1716 replicates in HGG without causing toxicity in both HSV-seropositive and -seronegative patients.

Evidence for a slow time-scale of interaction for magnetic fields inhibiting tamoxifen's antiproliferative action in human breast cancer cells

One critical biophysical feature of environmental-level magnetic field (MF) interactions with biological systems is the time-scale of interaction. A recently proposed fast/slow hypothesis states that a fast mechanism can only sense the instantaneous absolute value of the MF, and that a slow mechanism is potentially capable of sensing features such as frequency and relative orientation and magnitude of the field components. Here we applied the fast/slow hypothesis to a breast cancer model system: A 1.2 microT (rms), 60-Hz field inhibits tamoxifen's (TAM's) cytostatic action in MCF-7 cells via a MF interaction. We measured the growth of MCF-7 cells treated with TAM over 7 d, within different MFs: a sinusoidal, 60-Hz, 0.2-microT(rms) field; a sinusoidal, 60-Hz, 1.2-microT(rms) field; and a full-wave rectified version of the 1.2-microT(rms) sinusoidal field. A fast mechanism should not be able to distinguish between the latter two exposures. We observe that the rectified 1.2-microT field does not inhibit TAM's action, but that the 1.2-microT sinusoidal field does. Therefore, the 1.2-microT MF inhibition of TAM's cytostatic action operates via a relatively slow mechanism, and we predict that there exists a biologically dynamic complex capable of sensing a 1.2-microT, 60-Hz sinusoidal MF with an intrinsic time-scale of 17 ms or longer, the period of the 60-Hz applied field.

Toxicity evaluation of replication-competent herpes simplex virus (ICP 34.5 null mutant 1716) in patients with recurrent malignant glioma

The herpes simplex virus (HSV) ICP34.5 null mutant 1716 replicates selectively in actively dividing cells and has been proposed as a potential treatment for cancer, particularly brain tumours. We present a clinical study to evaluate the safety of 1716 in patients with relapsed malignant glioma. Following intratumoural inoculation of doses up to 10(5) p.f.u., there was no induction of encephalitis, no adverse clinical symptoms, and no reactivation of latent HSV. Of nine patients treated, four are currently alive and well 14-24 months after 1716 administration. This study demonstrates the feasibility of using replication-competent HSV in human therapy.

A comparison of proxy measures of abdominal obesity in Chinese, European and South Asian adults

AIMS

To assess whether four proxy measures of abdominal obesity (waist circumference; waist-to-hip ratio (WHR); waist-to-height ratio and C index, a measure of body shape) were uniformly associated with features of the metabolic syndrome (triglycerides, high density lipoprotein (HDL) cholesterol, 2-h glucose) in three ethnic groups.

METHODS

Anthropometric and biochemical data were collected in 629 Europeans (320 men, 309 women), 380 Chinese (183 men, 197 women) and 597 South Asians (275 men, 322 women) aged 25-64 years in Newcastle upon Tyne, UK. Linear regression models were used to determine whether relationships differed between ethnic groups.

RESULTS

Linear regression analysis showed that most proxy measures of abdominal obesity were associated with features of the metabolic syndrome. There were significant interactions between WHR and ethnicity and C index and ethnicity in the relationship with log triglycerides when comparing European and Chinese women. Interactions existed between all proxy measures and ethnicity in the relationship with log triglycerides and HDL cholesterol when comparing European and South Asian women. In men, interactions between ethnicity and waist circumference, WHR and C index when comparing Europeans and South Asians, and between ethnicity and WHR and C index when comparing South Asian and Chinese for log 2-h glucose were significant (P < 0.001). All interactions remained significant when differences in smoking, alcohol and physical activity were taken into account.

CONCLUSIONS

Not all the proxy measures of abdominal obesity were consistently related to features of the metabolic syndrome across the ethnic groups studied. However, waist circumference and waist to height ratio were the most consistent and WHR the least when comparing across the ethnic groups.

The Newcastle exercise project: a randomised controlled trial of methods to promote physical activity in primary care

OBJECTIVE

To evaluate the effectiveness of combinations of three methods to promote physical activity.

DESIGN

Randomised controlled trial. Baseline assessment with post-intervention follow up at 12 weeks and 1 year.

SETTING

One urban general practice, 1995-7.

PARTICIPANTS

523 adults aged 40 to 64 years, randomised to four intervention groups and a control group.

INTERVENTIONS

Brief (one interview) or intensive (six interviews over 12 weeks) motivational interviewing based on the stages of change model of behaviour change, with or without financial incentive (30 vouchers entitling free access to leisure facilities).

MAIN OUTCOME MEASURES

Physical activity score; sessions of moderate and vigorous activity in the preceding four weeks.

RESULTS

Response rate was 81% at 12 weeks and 85% at one year. More participants in the intervention group reported increased physical activity scores at 12 weeks than controls (38% v 16%, difference 22%, 95% confidence interval for difference 13% to 32%), with a 55% increase observed in those offered six interviews plus vouchers. Vigorous activity increased in 29% of intervention participants and 11% of controls (difference 18%, 10% to 26%), but differences between the intervention groups were not significant. Short term increases in activity were not sustained, regardless of intensity of intervention.

CONCLUSIONS

The most effective intervention for promoting adoption of exercise was the most intensive. Even this did not promote long term adherence to exercise. Brief interventions promoting physical activity that are used by many schemes in the United Kingdom are of questionable effectiveness.

Heterogeneity of coronary heart disease risk factors in Indian, Pakistani, Bangladeshi, and European origin populations: cross sectional study

OBJECTIVE

To compare coronary risk factors and disease prevalence among Indians, Pakistanis, and Bangladeshis, and in all South Asians (these three groups together) with Europeans.

DESIGN

Cross sectional survey.

SETTING

Newcastle upon Tyne.

PARTICIPANTS

259 Indian, 305 Pakistani, 120 Bangladeshi, and 825 European men and women aged 25-74 years.

MAIN OUTCOME MEASURES

Social and economic circumstances, lifestyle, self reported symptoms and diseases, blood pressure, electrocardiogram, and anthropometric, haematological, and biochemical measurements.

RESULTS

There were differences in social and economic circumstances, lifestyles, anthropometric measures and disease both between Indians, Pakistanis, and Bangladeshis and between all South Asians and Europeans. Bangladeshis and Pakistanis were the poorest groups. For most risk factors, the Bangladeshis (particularly men) fared the worst: smoking was most common (57%) in that group, and Bangladeshis had the highest concentrations of triglycerides (2.04 mmol/l) and fasting blood glucose (6.6 mmol/l) and the lowest concentration of high density lipoprotein cholesterol (0.97 mmol/l). Blood pressure, however, was lowest in Bangladeshis. Bangladeshis were the shortest (men 164 cm tall v 170 cm for Indians and 174 cm for Europeans). A higher proportion of Pakistani and Bangladeshi men had diabetes (22.4% and 26.6% respectively) than Indians (15.2%). Comparisons of all South Asians with Europeans hid some important differences, but South Asians were still disadvantaged in a wide range of risk factors. Findings in women were similar.

CONCLUSION

Risk of coronary heart disease is not uniform among South Asians, and there are important differences between Indians, Pakistanis, and Bangladeshis for many coronary risk factors. The belief that, except for insulin resistance, South Asians have lower levels of coronary risk factors than Europeans is incorrect, and may have arisen from combining ethnic subgroups and examining a narrow range of factors.

Comparison of the current WHO and new ADA criteria for the diagnosis of diabetes mellitus in three ethnic groups in the UK. American Diabetes Association

The American Diabetes Association have recommended that the fasting plasma glucose level for the diagnosis of diabetes is lowered and that this becomes the main diagnostic test. We have used population-based data from three ethnic groups in Newcastle upon Tyne to examine the implications of this change. Data were available on 824 European (25-74 years), 375 Chinese (25-64 years), and 680 South Asian (25-74 years) subjects. All subjects apart from those reporting a prior diagnosis of diabetes underwent a standard 75 g oral glucose tolerance test (WHO criteria) which included the measurement of fasting glucose. The prevalence of diabetes was higher in all three ethnic groups using the new ADA criteria compared to the WHO criteria: 7.1% vs 4.8% in Europeans; 6.2% vs 4.7% in Chinese; and 21.4% vs 20.1% in South Asians. There was much variation in individuals categorized by the ADA and WHO criteria. Agreement between the two for the diagnosis of previously unknown diabetes was only moderate (kappa statistics 0.42 to 0.59). Thus in the populations studied the new criteria would increase the prevalence of diabetes in addition to classifying some individuals diabetic by current criteria as non-diabetic. It should be stressed however that diagnosis of the individual should not be based on a single test.

The herpes simplex virus virulence factor ICP34.5 and the cellular protein MyD116 complex with proliferating cell nuclear antigen through the 63-amino-acid domain conserved in ICP34.5, MyD116, and GADD34

The herpes simplex virus (HSV) virulence factor ICP34.5, the mouse myeloid differentiation protein MyD116, and the hamster growth arrest and DNA damage protein GADD34 share a 63-amino-acid carboxyl domain which has significant homologies to otherwise divergent proteins. Here we report that both ICP34.5 and its cellular homolog MyD116 complex through the conserved domain with proliferating cell nuclear antigen. In addition, HSV infection induces a novel 70-kDa cellular protein detectable by antisera to both ICP34.5 and GADD34, demonstrating that this novel protein possesses homology with the 63-amino-acid conserved domain.

Body mass index, waist circumference, waist-hip ratio, and glucose intolerance in Chinese and Europid adults in Newcastle, UK

OBJECTIVE

To compare the prevalence of glucose intolerance (impaired glucose tolerance and diabetes), and its relationship to body mass index (BMI) and waist-hip ratio in Chinese and Europid adults.

DESIGN

This was a cross sectional study.

SETTING

Newcastle upon Tyne.

SUBJECTS

These comprised Chinese and Europid men and women, aged 25-64 years, and resident in Newcastle upon Tyne, UK.

MAIN OUTCOME MEASURES

Two hour post load plasma glucose concentration, BMI, waist circumference, and waist-hip ratio.

METHODS

Population based samples of Chinese and European adults were recruited. Each subject had a standard WHO oral glucose tolerance test.

RESULTS

Complete data were available for 375 Chinese and 610 Europid subjects. The age adjusted prevalences of glucose intolerance in Chinese and Europid men were 13.0% (p = 0.04). Mean BMIs were lower in Chinese men (23.8 v 26.1) and women (23.5 v 26.1) than in the Europids (p values < 0.001), as were waist circumferences (men, 83.3 cm v 90.8, p < 0.001; women, 77.3 cm v 79.2, p < 0.05). Mean waist-hip ratios were lower in Chinese men (0.90 v 0.91, p = 0.02) but higher in Chinese women (0.84 v 0.78, p < 0.001) compared with Europids. In both Chinese and Europid adults, higher BMI, waist circumference, and waist-hip ratio were associated with glucose intolerance.

CONCLUSIONS

The prevalence of glucose intolerance in Chinese men and women, despite lower BMIs, is similar to or higher than that in local Europid men and women and intermediate between levels found in China and those in Mauritius. It is suggested that an increase in mean BMI to the levels in the Europid population will be associated with a substantial increase in glucose intolerance in Chinese people.

ICP34.5 influences herpes simplex virus type 1 maturation and egress from infected cells in vitro

We have previously demonstrated that efficient replication of mutant herpes simplex virus which fails to synthesize the polypeptide ICP34.5 is cell type and cell state dependent. ICP34.5 negative viruses do not grow in stationary state mouse embryo fibroblast 3T6 cells whereas the growth kinetics in BHK cells are indistinguishable from those of wild-type. We now demonstrate that this defect is not due to an inability of mutant virus to adsorb to 3T6 cells but rather to an inability to spread from the initially infected cells. Electron microscopic studies with wild-type HSV in both BHK and 3T6 cells revealed virus particles equally distributed between nucleus and cytoplasm, and additionally in the extracellular matrix. In BHK cells infected with the ICP34.5 negative mutant 1716, virus is likewise distributed between nucleus and cytoplasm but in 50% of the infected cells there is marked delamination and swelling of the nuclear membrane. In addition there is evidence of a significant number of particles trapped between the nuclear lamellae. When 1716 is used to infect 3T6 cells, over 90% of the virus particles are confined to the nuclei and the number of infected cells remains constant between 24 and 48 h with no increase in the proportion of extracellular virus. Failure to express ICP34.5 appears therefore to result in a defect in virus maturation and egress from the nuclei of infected cells. Egress of HSV from the nuclei to the extracellular space is thought to occur via two pathways. We postulate that lack of expression of ICP34.5 results in one of these pathways being blocked. In BHK cells this leads to overloading of the alternative pathway with a buildup of particles in the nuclear lamellae and associated endoplasmic reticulum. In stationary state 3T6 cells, it appears that there is no functional alternative pathway. We conclude that ICP34.5 exerts an effect on HSV maturation by controlling the passage of virus through infected cells.

Cell type and cell state determine differential in vitro growth of non-neurovirulent ICP34.5-negative herpes simplex virus types 1 and 2

The herpes simplex virus (HSV) gene RL1 encodes the protein ICP34.5, which is a specific neurovirulence factor. Null mutants in RL1 fail to replicate in the central nervous system of mice and are therefore totally non-neurovirulent. Additionally, they fail to replicate in neurons of the peripheral nervous system, although they are capable of establishing and reactivating from a latent infection. As the precise function of ICP34.5 in HSV-neuronal interactions is unknown, we have studied the role of ICP34.5 in vitro by examining in detail the phenotypes of RL1-negative viruses in two defined tissue culture systems. The first was mouse embryo fibroblast 3T6 cells, in which RL1-negative mutants are impaired and the in vivo phenotype is mimicked. This impairment is amplified when the cells are in the stationary state. The second was mouse embryo testicular carcinoma F9 cells which, in the undifferentiated state, provide a reversal of phenotype; wild-type virus fails to grow but RL1-negative virus replicates efficiently. Differentiation results in the ability to support wild-type virus growth. The stage at which the replication cycle is blocked plus the role of cellular factors is addressed in both tissue culture systems. Evidence is provided that cell type and cell state are crucial to ICP34.5-cellular interaction and hence, based on these parameters, ICP34.5 can be defined as a host-range determinant. Identification of cellular proteins that specifically interact with or are homologues of ICP34.5 may lead to the identification of neuron-specific proteins that have a similar role.

Cholesterol and lipoprotein(a) as risk factors for coronary heart disease in elderly subjects

The changes in lipoprotein(a) concentration that occur with age as a result of its association with an increased risk of coronary artery disease were investigated. Lipoprotein(a) concentrations were measured in serum samples from healthy volunteers, individuals with premature coronary artery disease, individuals with hyperlipidaemia but without evidence of premature coronary artery disease, and also in elderly men and women who had hyperlipidaemia. Concentrations in individuals with premature coronary artery disease were the same as those of the healthy volunteers, while in both these groups they were lower than those found in hyperlipidaemic elderly men and women, and those found in hyperlipidaemic women aged 36-68 years. No association between raised lipoprotein(a) concentration and mortality as a result of premature coronary artery disease was demonstrated. Raised lipoprotein(a) levels found in the hyperlipidaemic individuals also suggested that it may not be an independent risk factor.

Experimental evidence for 60 Hz magnetic fields operating through the signal transduction cascade. Effects on calcium influx and c-MYC mRNA induction

We tested the hypothesis that early alterations in calcium influx induced by an imposed 60 Hz magnetic field are propagated down the signal transduction (ST) cascade to alter c-MYC mRNa induction. To test this we measured both ST parameters in the same cells following 60 Hz magnetic field exposures in a specialized annular ring device (220 G (22 mT), 1.7 mV/cm maximal E(induced), 37 degrees C, 60 min). Ca2+ influx is a very early ST marker that precedes the specific induction of mRNA transcripts for the proto-oncogene c-MYC, an immediate early response gene. In three experiments influx of 45Ca2+ in the absence of mitogen was similar to that in cells treated with suboptimal levels of Con-A (1 micrograms/ml). However, calcium influx was elevated 1.5-fold when lymphocytes were exposed to Con-A plus magnetic fields; this co-stimulatory effect is consistent with previous reports from our laboratory [FEBS Lett. 301 (1992) 53-59; FEBS Lett. 271 (1990) 157-160; Ann. N.Y. Acad. Sci. 649 (1992) 74-95]. The level of c-MYC mRNA transcript copies in non-activated cells and in suboptimally-activated cells was also similar, which is consistent with the above calcium influx findings. Significantly, lymphocytes exposed to the combination of magnetic fields plus suboptimal Con-A responded with an approximate 3.0-fold increase in band intensity of c-MYC mRNA transcripts. Importantly, transcripts for the housekeeping gene GAPDH were not influenced by mitogen or magnetic fields. We also observed that lymphocytes that failed to exhibit increased calcium influx in response to magnetic fields plus Con-A, also failed to exhibit an increase in total copies of c-MYC mRNA. Thus, calcium influx and c-MYC mRNA expression, which are sequentially linked via the signal transduction cascade in contrast to GAPDH, were both increased by magnetic fields. These findings support the above ST hypothesis and provide experimental evidence for a general biological framework for understanding magnetic field interactions with the cell through signal transduction. In addition, these findings indicate that magnetic fields can act as a co-stimulus at suboptimal levels of mitogen; pronounced physiological changes in lymphocytes such as calcium influx and c-MYC mRNA induction were not triggered by a weak mitogenic signal unless accompanied by a magnetic field. Magnetic fields, thus, have the ability to potentiate or amplify cell signaling.

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.

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.

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.

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.

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.

Generation of a herpes simplex virus type 2 variant devoid of XbaI sites: removal of the 0.91 map coordinate site results in impaired synthesis of glycoprotein G-2

Herpes simplex virus (HSV) type 2 (strain HG52) has four XbaI sites at map coordinates (m.c.) 0.45, 0.7, 0.91 and 0.94, i.e. two in the unique long and two in the unique short regions of the genome. Previously, we had isolated a genome containing only the 0.45 and 0.94 XbaI sites. Here we report the isolation of a mutant (JH2611) in which all four XbaI sites have been removed using an enrichment selection procedure, without any loss of viability. Removal of each site has been shown to be due to a base change or small undetectable deletion/insertion of less than 100 bp. In HSV-1, the XbaI site at 0.45 m.c. is in an open reading frame coding for a polypeptide of 14K. Both the 0.7 and 0.94 m.c. HSV-2 XbaI sites are in intergenic positions. The 0.91 m.c. XbaI site has been shown to be within the coding sequence of the glycoprotein gG-2. Synthesis of gG-2 by JH2611 and two other mutants, JH2610 (formerly HG52X163X3) and JH2609 (formerly HG52X163X21), in which the 0.91 m.c. site has been deleted was analysed by immunoprecipitation using the gG-2-specific monoclonal antibodies AP1 and LP5 and the anti-peptide serum 14713. In the mutants JH2610 and JH2611 neither gG-2 nor its precursor were detected but the monoclonal antibodies detected two polypeptides migrating above the normal positions of gG-2 and the gG-2 precursor; these were not precipitated by the anti-peptide serum. With the mutant JH2609 neither gG-2 nor its precursors could be detected by either the monoclonal antibodies or the anti-peptide serum. The results strongly suggest that gG-2 is non-essential for the growth of HSV-2 in vitro.

Three mutants of herpes simplex virus type 2: one lacking the genes US10, US11 and US12 and two in which Rs has been extended by 6 kb to 0.91 map units with loss of Us sequences between 0.94 and the Us/TRs junction

In the process of generating restriction endonuclease site deletion mutants, we have isolated and characterized three mutants of herpes simplex virus type 2 (HSV-2), strain HG52, with large genomic deletions in Us and TRs. The deleted sequences (7.5 kb) extend from 0.94 map coordinates (m.c.) to 0.99 m.c. and are presumed to contain the HSV-2 gene equivalents of US10, 11 and 12, one copy of immediate early (IE) gene 3 and one copy of an origin of replication (ORIs). One of the mutants (HG52X163X12) has a simple deletion whereas in the two others (HG52X163X14 and HG52X163X21) the deleted sequences have been replaced by inverted duplications of Us/IRs sequences between 0.83 and 0.91 m.c. such that the molecules have short region inverted repeats extended by 6 kb on either side. All three are viable, stable and grow in tissue culture indicating that the polypeptides coded by the HSV-2 genes equivalent to US10, 11 and 12 are non-essential for lytic growth in BHK21/C13 cells. In addition the lack of one copy of the HSV-2 equivalent of IE gene 3 and ORIs in HG52X163X12 shows that only one copy of each suffices for viability. However the temperature restriction of the mutants at 38.5 degrees C suggests that one or more of the polypeptides coded by the deleted sequences may be required in conjunction with another polypeptide(s) for viral growth or stability at the higher temperature.

Isolation and characterization of deletion mutants of herpes simplex virus type 2 (strain HG52)

We provide evidence that: (i) two variants lacking the XbaI site at map coordinate 0.7 have been selected following XbaI treatment of the DNA of herpes simplex virus type 2 strain HG52; (ii) one of these mutants had lost the 0.7 restriction site due to a deletion of approximately 150 base pairs and in the other the site loss was due to a similar sized sequence insertion; (iii) following XbaI treatment, four variants with deletions ranging in size from 1.5 kb (in both TRL and IRL) to 9 kb in IRL were isolated; (iv) substantial deletions in the long terminal repeat regions of HG52 are present with a frequency of 24% of genomes in the elite stock, a variant with a 3.75 kb deletion in IRL making up 10% and one with a 1.5 kb deletion in both IRL and TRL making up 14%; (v) two of the variants isolated after XbaI treatment of viral DNA were identical to the deletion prototype within the elite stock, suggesting that these variants were not generated as a result of XbaI treatment but pre-existed in the viral DNA pool; (vi) the deletion variants were stably maintained during routine stock propagation, were viable and could be propagated as cloned populations; (vii) the deletions did not have a marked deleterious effect on the one-step growth kinetics of the virus.

Isolation of restriction endonuclease site deletion mutants of herpes simplex virus

We provide evidence that (i) variants lacking individual herpes simplex virus type 1 (HSV-1) XbaI sites can be selected following extensive XbaI treatment of the viral DNA and can be recombined to produce HSV-1 variants lacking two of the four sites normally found, (ii) all XbaI sites can be removed from a viable intertypic recombinant HSV genome, (iii) following XbaI treatment, different mutants with deletions (0.15 to 8.8 kb) in the long repeat ( TRL or IRL ) and long unique regions can be readily isolated, as well as mutants with novel XbaI sites, (iv) several mutants with deletions in one of the repeats ( TRL or IRL ) have a measurable growth disadvantage in tissue culture.

Changes in some Enzymes involved in DNA Biosynthesis following Induction of Division in Cultured Plant Cells

The biosynthetic enzymes DNA polymerase, thymidine kinase (TdR kinase) and thymidine monophosphate kinase (dTMP kinase) show characteristic patterns of activity associated with cell division in synchronously dividing tissue cultures of the Jerusalem artichoke. In each case the first major increase in enzyme activity is coincident with and dependent upon DNA replication. In addition the increased activities of all 3 enzymes are not due to the activation of pre-existing enzyme or to the removal of inhibitors. A theory is advanced to account for the close correlation between DNA synthesis and the major rise in activity of the 3 enzymes.