Clinical efficacy of monotherapy with stavudine compared with zidovudine in HIV-infected, zidovudine-experienced patients. A randomized, double-blind, controlled trial. Bristol-Myers Squibb Stavudine/019 Study Group

BACKGROUND

Stavudine is a promising antiretroviral agent, but its clinical efficacy has not been determined.

OBJECTIVE

To evaluate the clinical effect of stavudine (2',3'-didehydro-3'-deoxythymidine) monotherapy in patients with human immunodeficiency virus (HIV) infection.

DESIGN

Randomized, controlled, double-blind trial.

SETTING

56 outpatient clinics in private practices, universities, and contract research organizations in the United States, France, and Italy.

PATIENTS

822 HIV-infected adults who had 50 to 500 CD4+ cells/mm3 and had previously received at least 6 months of zidovudine treatment.

INTERVENTION

Monotherapy with peroral stavudine capsules or peroral zidovudine capsules.

MEASUREMENTS

The primary end point was clinical progression, which was defined as all occurrences of acquired immunodeficiency syndrome (AIDS)-defining events or death.

RESULTS

Patients receiving stavudine reached clinical end points at a rate of 26 per 100 person-years, compared with 32 per 100 person-years for patients receiving zidovudine (relative risk, 0.75 [95% CI, 0.58 to 0.98]; P = 0.03). The risk for death alone was 26% lower in the stavudine group than in the zidovudine group, but the comparison was not statistically significant (relative risk, 0.74 [CI, 0.53 to 1.02]; P = 0.066). The benefit of stavudine therapy was seen in all CD4+ cell strata (< or = 100 cells/mm3, 101 to 300 cells/mm3, and > 300 cells/mm3) and clinical stages of HIV disease (asymptomatic, symptomatic, and AIDS). Four weeks after treatment began, CD4+ cell counts were 30 cells/mm3 higher in the stavudine group than in the zidovudine group; this difference was sustained for 96 weeks (P < 0.001). Nausea and vomiting were more common in patients receiving zidovudine (P < 0.01), and neuropathy occurred more frequently in those receiving stavudine (12% in the stavudine group compared with 4% in the zidovudine group; P < 0.001). Neuropathy resolved completely in many patients (63%) after interruption of stavudine treatment; these patients could resume stavudine therapy at a lower dose.

CONCLUSIONS

Stavudine was well tolerated and delayed progression of HIV disease in patients who had previously received 6 or more months of zidovudine treatment. Benefits were apparent in all CD4+ cell strata and clinical stages of HIV disease. Stavudine is an important agent to consider for trials of combination chemotherapy.

A novel ubiquitin-specific protease is dynamically associated with the PML nuclear domain and binds to a herpesvirus regulatory protein

Herpes simplex virus type 1 immediate-early protein Vmw110 is a non-specific activator of gene expression and is required for efficient initiation of the viral lytic cycle. Since Vmw110-deficient viruses reactivate inefficiently in mouse latency models it has been suggested that Vmw110 plays a role in the balance between the latent and lytic states of the virus. The mechanisms by which Vmw110 achieves these functions are poorly understood. Vmw110 migrates to discrete nuclear structures (ND10) which contain the cellular PML protein, and in consequence PML and other constituent proteins are dispersed. In addition, Vmw110 binds to a cellular protein of approximately 135 kDa, and its interactions with the 135 kDa protein and ND10 contribute to its ability to stimulate gene expression and viral lytic growth. In this report we identify the 135 kDa protein as a novel member of the ubiquitin-specific protease family. The protease is distributed in the nucleus in a micropunctate pattern with a limited number of larger discrete foci, some of which co-localize with PML in ND10. At early times of virus infection, the presence of Vmw110 increases the proportion of ND10 which contain the ubiquitin-specific protease. These results identify a novel, transitory component of ND10 and implicate a previously uncharacterized ubiquitin-dependent pathway in the control of viral gene expression.

High-resolution magnetic resonance imaging of normal porcine cartilaginous epiphyseal maturation

The aim of this study was to determine whether high-resolution magnetic resonance (MR) imaging could differentiate epiphyseal and articular cartilage in the cartilaginous epiphysis and demonstrate its developmental changes. T1- and T2-weighted (T1W and T2W) spin-echo sequences at 50-mm field of view (FOV) of hip joints were obtained from 14 piglets (newborn to 6 months). Subsequently, high-resolution MR images (15-mm FOV) of a biopsy core of the proximal femoral cartilaginous epiphysis were correlated with histology. Newborn cartilaginous epiphysis demonstrated homogeneous signal intensity on T1W and T2W imaging with abundant cartilage canals. From 2 weeks of age, the cartilaginous epiphysis showed a diminution of cartilage canals, with three zones evident on T2W imaging consisting of a low-signal middle zone separating two higher signal zones. Histologic evaluation demonstrated four distinct morphologic laminas with a decrease in overall cartilage thickness with age. The laminas were not as well defined in the newborn compared with the older piglets. No simple correlation was found between the MR zonal pattern and the morphological laminas on histology. No distinct demarcation between the articular cartilage and epiphyseal cartilage was present. MR can visualize cartilage canals and demonstrate changes in the cartilaginous epiphysis that occur with maturation. What component of the cartilaginous epiphysis that accounts for the MR differences seen between newborn and older piglets remains unclear.

Intracellular localisation of herpes simplex virus type 1 ribonucleotide reductase subunits during infection of cultured cells

We have analysed the intracellular localisation of herpes simplex virus type 1 ribonucleotide reductase during infection of cultured cells by indirect immunofluorescence using polyclonal and monoclonal antibodies specific for the R1 and R2 subunits. Three different viruses were used to infect cells, wild-type strain 17+ and two temperature-sensitive mutants, ts 1222, which produces R1 only, and ts 1207, which expresses a normal R2 and an altered R1 that fails to interact with R2 at the nonpermissive temperature because of an amino acid substitution in R1. R1 was detected 2 hr postinfection with all three viruses and remained evenly distributed throughout the cytoplasm. R2 was not observed until 4 hr postinfection and, in contrast to the even distribution of R1, was localised in discrete cytoplasmic foci close to the nucleus. In double-labelling experiments both R1 and R2 were found in these foci where they presumably associate to form the active enzyme. As expected R2 was not detectable in cells infected with ts 1222. In ts 1207-infected cells it formed wild-type-like foci, indicating that interaction with R1 is not required for R2 focus formation. R1 was present in a twofold excess over R2 in wild-type-infected cells. We suggest that the uncomplexed R1 could perform a role associated with the protein kinase present in the N-terminal domain.

Monoclonal antibody blocking tests for the detection of HSV-1- and HSV-2-specific humoral responses: comparison with western blot assay

Monoclonal antibody blocking radioimmunoassays (MAb block RIAs) which detect specific humoral responses to each of the two human herpes simplex virus (HSV) types are described. RIAs were compared with Western blot assay (WBA) in a blind study of 64 sera obtained from clinically well-documented cases of genital herpes. WBA and MAb block RIA each detected HSV-1 antibodies in 16/17 (94%) sera from confirmed HSV-1 genital infections (first episodes and recurrent infections). Detection of HSV-2 antibody in 21 sera from HSV-2 first episodes was more effective by WBA which identified homologous antibody in 19 (96%), whereas MAb block RIA detected HSV-2 antibody in 16 (76%). HSV-2 antibody was detected in 24/25 (96%) sera from recurrent HSV-2 infections by WBA and by MAb block RIA, the highest degree of concordance for both methods. In addition, the MAb block RIA may be more effective in detecting the presence of HSV-1 antibody in sera from recurrent HSV-2 cases. Prevalence of HSV-1 and HSV-2 antibody was measured by the MAb block RIAs in 3 UK human study populations which consisted of 100 children/young adolescents, 104 adult blood donors and 80 genito-urinary medicine clinic attenders.

The early and periodic screening, diagnosis and treatment program: opportunities for nurse practitioners

The Early and Periodic Screening, Diagnosis and Treatment (EPSDT) Program is intended to provide comprehensive preventive health care services for children and young adults from low-income families on Medicaid. Unfortunately, only a fraction of the individuals eligible for care actually receive EPSDT services, often because of a shortage of providers who offer these services. Nurse practitioners are ideally suited to offer such services and, in states where they are allowed to function independently, can receive direct Medicaid reimbursement for them. Because many nurse practitioners are unfamiliar with the EPSDT program, this article describes the key components of the program and explains how nurse practitioners can provide EPSDT services.

The importance of a lipopolysaccharide-initiated, cytokine-mediated host defense mechanism in mice against extraintestinally invasive Escherichia coli

Extraintestinally invasive Escherichia coli (EC) that possess both a complete LPS and K1 capsule evade both complement-mediated bacteriolysis and neutrophil-mediated killing. Since C3H/HeJ mice that are hyporesponsive to LPS were uniquely susceptible to lethal infection with EC of this phenotype, we speculated there was an LPS-initiated host defense mechanism against this pathogenic phenotype. The LPS-normoresponsive C3H/HeN as well as the C3H/HeJ mice cleared these EC from the circulation within 4 h of intravenous administration. Whereas electron micrographs of the liver demonstrated these EC undergoing degeneration within the phagolysosomes of of both macrophages and Kupffer cells of C3H/HeN mice, these EC replicated within these cells of the C3H/HeJ mice. Restoration of anti-EC activity of C3H/HeJ mice occurred with activation of Kupffer cells and peritoneal macrophages in vivo with BCG and in vitro with IFN-gamma, but not with LPS. Pretreatment of C3H/HeJ mice with a combination of recombinant murine IL-1 and TNF-alpha also restored the killing of K1(+)-EC but did not enhance the killing of a K1(-)-EC mutant. These data are consistent with the hypothesis that (a) there is no intrinsic inability of C3H/HeJ phagocytes to kill EC, but (b) an LPS-initiated, cytokine-mediated host defense mechanism is required for such killing. These studies emphasize the importance of bacterial surface characteristics in the interaction with specific host defenses.

Dose-related activity of stavudine in patients infected with human immunodeficiency virus

In a multicenter, randomized, open-label, dose-ranging study to determine the relative effects of three dose levels of stavudine on CD4 lymphocyte count, weight gain, and hematologic variables in patients infected with human immunodeficiency virus (HIV), 152 patients with CD4 lymphocyte counts < or = 600/mm3 received stavudine at 0.1 mg/kg/day (n = 51), 0.5 mg/kg/day (n = 53), or 2.0 mg/kg/day (n = 48). The study was designed to evaluate the activity of stavudine after 10 weeks of therapy and permitted extended dosing and follow-up for long-term safety. A significant dose effect on increases in CD4 lymphocyte counts and declines in HIV titer in peripheral blood mononuclear cells was observed. Stavudine was well-tolerated; the only dose-related, dose-limiting adverse event was peripheral neuropathy, which usually was reversible. In this trial, the most favorable therapeutic index was seen at 0.5 mg/kg/day.

Design and implementation of the stavudine parallel-track program

In a randomized, double-blind, large, simple trial, the safety and efficacy of two weight-adjusted dose levels of stavudine were evaluated in patients with advanced human immunodeficiency virus (HIV) infection. All patients were refractory to or intolerant of both zidovudine and didanosine. Patients weighing > or = 60 kg received 20 or 40 mg of stavudine twice daily. The dose was reduced to 15 or 30 mg for patients weighing 40-59 kg and to 10 or 20 mg for those weighing < 40 kg. The primary efficacy end points were survival and time to clinical progression of HIV disease. The primary safety end point was time to dose-limiting neuropathy. A total of 8127 patients were enrolled as of 31 July 1993. Although many patients who might have benefitted from stavudine were reached by the parallel-track program, a review of demographic data revealed disproportionate representation by white men from large metropolitan areas on both coasts.

Stavudine in patients with AIDS and AIDS-related complex: AIDS clinical trials group 089

In a phase I trial of stavudine in AIDS or AIDS-related complex (ARC), antiviral effects and safety were assessed in 41 patients treated with dosages of 0.5-12.0 mg/kg/day. Among evaluable patients, 10% increases in CD4 lymphocyte counts were sustained in 24 (60%) of 40 during treatment; an NAUC response (normalized area under the CD4 cell count-versus-time curve > 1.0) was observed in 31 (91%) of 34 at 10 weeks and in 20 (80%) of 25 at 24 weeks; 15 (83%) of 18 had decreases in p24 antigenemia; and 24 (60%) of 40 gained > or = 2.5 kg body weight. Median CD4 lymphocyte levels remained above baseline for 6 months in patients receiving > 0.5 mg/kg/day. Median serum p24 antigen levels remained below baseline for > or = 1 year in patients with p24 antigen responses. The principal toxicity was peripheral neuropathy, which generally resolved after drug discontinuation but limited the dosage to < or = 2.0 mg/kg/day. Additional trials assessing the effect of stavudine on overall morbidity and mortality are ongoing.

Identification of structural domains within the large subunit of herpes simplex virus ribonucleotide reductase

The large subunit (R1) of herpes simplex virus (HSV) ribonucleotide reductase is a bifunctional protein consisting of a unique N-terminal protein kinase domain and a ribonucleotide reductase domain. Previous studies showed that the two functional domains are linked by a protease sensitive site. Here we provide evidence for two subdomains, of 30K and 53K, within the reductase domain. The two fragments, which were produced by limited proteolysis and were resistant to further degradation, remained tightly associated in a complex containing two molecules of each. They were capable of binding the R2 subunit of HSV ribonucleotide reductase with approximately the same affinity as the intact protein but the complex did not complement the small subunit (R2) to give an active enzyme. At low concentrations (0.4 micrograms/ml) of trypsin or V8 protease, cleavage between the subdomains was prevented by the presence of the N-terminal protein kinase domain. At higher protease concentrations (1 micrograms/ml) the N-terminal domain is extensively proteolysed and the 30K and 53K domains were generated. Identical results were obtained using purified R1 isolated from infected cell extracts or following expression in Escherichia coli. The origin of the two domains was investigated by N-terminal sequencing of the 53K fragment and by examining their reactivity with a panel of R1-specific monoclonal antibodies which we isolated and epitope mapped for that purpose. The trypsin cleavage site was found to lie between arginine 575 and asparagine 576, and proteolysis in this region was not prevented by the presence of R2 or the nonapeptide YAGAVVNDL. We propose that the ribonucleotide reductase region of HSV R1 exists in a two domain structure, and that the interdomain linking region is protected by the unique N terminus.

Safety and immunogenicity of a polyvalent Escherichia coli vaccine in human volunteers

Since a limited number of O serogroups account for nearly 70% of bacteremic and meningitic Escherichia coli isolates, a polyvalent vaccine was made by conjugating a Pseudomonas aeruginosa exotoxin A carrier protein to the O polysaccharide of 12 serogroups of E. coli (O1, O2, O4, O6-O8, O12, O15, O16, O18, O25, O75). No serious reactions occurred in 88 vaccinees. Four-fold or greater increases in ELISA antibody levels over baseline were greatest (> 60% of vaccinees) for O1, O2, O6-O8 and O15; intermediate (approximately 50%) for O18 and O75, and poorest (> or = 45%) for O4, O12, O16, and O25. Responses with functionally active opsonophagocytic antibody generally paralleled ELISA antibody responses. With the availability of a safe, immunogenic E. coli vaccine, active and passive immunization strategies merit further development as adjunctive treatment for E. coli bacteremia and neonatal meningitis.

High-energy phosphate metabolism in a neonatal model of hydrocephalus before and after shunting

The authors studied the effects of hydrocephalus on the high-energy phosphate metabolism of the brain and the impact of ventriculoperitoneal (VP) shunting on these changes in an experimental model of hydrocephalus. High-energy phosphate metabolism was analyzed using in vivo magnetic resonance (MR) imaging and 31P MR spectroscopy. Hydrocephalus was produced in 34 1-week-old kittens by cisternal injection of 0.05 ml of a 25% kaolin solution. Sixteen litter mates were used as controls. A VP shunt with a distal slit valve was implanted in 17 of the 34 hydrocephalic animals 10 days after induction of hydrocephalus. Both MR imaging and 31P MR spectroscopy were obtained 1 and 3 weeks after either kaolin or distilled water injection. Untreated hydrocephalic animals had marked dilatation of the lateral ventricles and periventricular edema. Magnetic resonance spectroscopy showed a significant decrease in the energy index ratio of phosphocreatine (PCR): inorganic phosphate (PI) and an increase in the PI:adenosine triphosphate (ATP) ratio. There was a direct correlation between the decrease in the energy index and ventricular size. Compared with preoperative scans, shunted animals showed no periventricular edema, and the ventricles decreased in size. Also, PCR:PI and PI:ATP ratios were within the levels of controls. This study suggests that neonatal hydrocephalus results in a mild hypoxic/ischemic insult that is treatable by VP shunting.

Specific inhibition of herpes virus replication by receptor-mediated entry of an antiviral peptide linked to Escherichia coli enterotoxin B subunit

Mimetic peptides capable of selectively disrupting protein-protein interactions represent potential therapeutic agents for inhibition of viral and cellular enzymes. This approach was first suggested by the observation that the peptide YAGAVVNDL, corresponding to the carboxyl-terminal 9 amino acids of the small subunit of ribonucleotide reductase of herpes simplex virus, specifically inhibited the viral enzyme in vitro. Evaluation and use of this peptide as a potential antiviral agent has, however, been thwarted by its failure to inhibit virus replication in vivo, presumably because the peptide is too large to enter eukaryotic cells unaided. Here, we show that the nontoxic B subunit of Escherichia coli heat-labile enterotoxin can be used as a recombinant carrier for the receptor-mediated delivery of YAGAVVNDL into virally infected cells. The resultant fusion protein specifically inhibited herpes simplex virus type 1 replication and ribonucleotide reductase activity in quiescent Vero cells. Preincubation of the fusion protein with soluble GM1 ganglioside abolished this antiviral effect, indicating that receptor-mediated binding to the target cell is necessary for its activity. This provides direct evidence of the usefulness of carrier-mediated delivery to evaluate the intracellular efficacy of a putative antiviral peptide.

Sampling for vaginal candidosis: how good is it?

In defined patient populations attending a genitourinary medicine department, screening for vaginal candidosis resulted in 26.3% positive rate. Microscopy using Gram-stained slide was useful in early diagnosis and resulted in the detection of 64.8% of symptomatic cases. Samples from the anterior fornix proved most sensitive for culture diagnosis while the left lateral vaginal wall proved least sensitive (positive predictive value 0.88 cf 0.81).

Chlormethiazole as an efficient inhibitor of cytochrome P450 2E1 expression in rat liver

Ethanol-inducible cytochrome P450 (CYP) 2E1 (CYP2E1) is responsible for the metabolism of many xenobiotics which exert toxic effects in humans. Specific inhibitors might constitute valuable tools in the elucidation of the pharmacological and toxicological roles of this isozyme in vivo. In the present investigation we have evaluated the effects of a drug used for treatment of ethanol withdrawal states, chloromethiazole (CMZ), on CYP2E1 expression in rat liver. A 4-fold induction of CYP2E1 was observed after 3 days of starvation, accompanied by a similar increase in the level of the corresponding mRNA. CMZ specifically inhibited the elevation of CYP2E1 mRNA and protein, but did not prevent CYP2B1 and CYP3A1 or CYP1A1 induction caused by treatment with phenobarbital or beta-naphthoflavone, respectively. From nuclear run-off experiments it was apparent that the rate of the CYP2E1 gene transcription was inhibited greatly by CMZ treatment. Rats treated with ethanol in a total enteral nutrition model had higher CYP2E1-dependent hepatic microsomal activities of p-nitrophenol hydroxylase and carbon tetrachloride-induced lipid peroxidation than controls, and simultaneous CMZ treatment abolished the ethanol-dependent induction. In vitro experiments with rat liver microsomes showed that CMZ did not act as an inhibitor of CYP2E1-dependent catalytic activities or as an inhibitor of microsomal NADPH and CYP2E1-dependent lipid peroxidation. In conclusion, we suggest that CMZ might constitute an efficient and specific inhibitor of CYP2E1 expression suitable for in vivo experiments.

Didanosine compared with continuation of zidovudine in HIV-infected patients with signs of clinical deterioration while receiving zidovudine. A randomized, double-blind clinical trial. The Bristol-Myers Squibb AI454-010 Study Group

OBJECTIVE

To determine the benefits of switching to didanosine compared with continuing zidovudine among patients infected with human immunodeficiency virus (HIV) who have previously used zidovudine and have signs of clinical deterioration.

DESIGN

Randomized, double-blind, two-armed, parallel, comparative clinical trial with a blinded, compassionate crossover provision at 12 weeks.

SETTING

Outpatient clinics at 19 tertiary care medical centers.

PATIENTS

312 patients infected with HIV who had received zidovudine for 6 months or more, had CD4 cell counts of 300/mm3 or less, and had signs of clinical deterioration within 12 weeks before study entry.

INTERVENTION

Peroral didanosine tablets (600 mg/d adjusted for weight, "high dose") or zidovudine capsules (600 mg/d).

MEASUREMENTS

Primary study end points were death, a new acquired immunodeficiency syndrome (AIDS)--defining event, or the combination of two new or recurrent HIV-related diagnoses with a 50% decrease in CD4 cells.

RESULTS

Switching to didanosine was associated with fewer end points than continuing zidovudine (relative risk [RR] for zidovudine:didanosine = 1.5; 95% Cl, 1.1 to 2.0). This benefit was consistent across subgroups of patients with either AIDS-related complex or AIDS and was most apparent among those with a CD4 count at entry of 100/mm3 or more (RR = 2.2; Cl, 1.1 to 4.4).

CONCLUSIONS

This study shows a positive treatment effect for switching from zidovudine to didanosine among patients with either AIDS-related complex or AIDS and validates the common practice of using clinical signs or a decrease in the CD4 count as an indication for changing therapy.

Stability of high-energy substrates in fast- and slow-twitch muscle: comparison of enzymatic assay of biopsy with in vivo 31P nuclear magnetic resonance spectroscopy

The purpose of this study was to investigate the stability of ATP and PCr levels in stored muscle samples and extracts. ATP and PCr levels were measured by fluorimetric analysis in freeze-clamped biopsies of soleus, extensor digitorum longus, and gastrocnemius muscles of the rat after storage in a freezer at -70 degrees C as (i) intact wet muscle, (ii) freeze-dried muscle, and (iii) an extract of freeze-dried muscle. Assays were performed within 24 h of taking the biopsy and after variable periods of storage from 1 to 4 weeks. The data for the gastrocnemius muscles were compared with those obtained, in the same rat, by in vivo 31P NMR spectroscopy. In the biopsies, the ATP levels were stable irrespective of the duration or method of storage. The PCr levels fell by 13-16% compared with the values obtained from the assay done within 24 h of taking the biopsy, irrespective of the method of storage, but could be corrected in the freeze-dried stored muscle by expressing the data in relation to the total creatine levels. The fluorimetrically measured PCr, in whole muscle extracts of the gastrocnemius, assayed within 24 h, were comparable to those obtained from 31P NMR spectroscopy. We concluded that PCr levels in muscle are not stable during storage at -70 degrees C and should be assayed within 24 h of taking a muscle biopsy to ensure that the values are the same as those obtained by 31P NMR.

Reduction of macular oedema by acetazolamide in patients with chronic iridocyclitis: a randomised prospective crossover study

Thirty patients with cystoid macular oedema secondary to chronic iridocyclitis were enrolled in a two period, prospective, randomised, double masked, crossover study that compared sustained release acetazolamide (500 mg twice a day) with a placebo to measure the effects on the reduction of cystoid macular oedema and improvement of visual acuity. All patients were treated for 1 month with either acetazolamide or placebo, received no treatment for 1 month, and were then treated for 1 month with the other medication. Statistically significant improvement in visual acuity was seen at 14 and 28 days in the treated patients. No improvement was seen when patients received placebo. Improved visual acuity was not associated with race or sex. However, younger patients (under age 55 years) were more likely to benefit from treatment. Results of vitreous fluorophotometry, obtained at baseline and 4 weeks, demonstrated an improvement in posterior vitreous penetration ratios and mid vitreous penetration ratios after treatment with acetazolamide but not with placebo.

Herpes simplex virus type 1 ribonucleotide reductase large subunit: regions of the protein essential for subunit interaction and dimerization

We have constructed a series of random N-terminal deletions of the large subunit (R1) of the herpes simplex virus type 1 ribonucleotide reductase. Deletions extended throughout the R1 gene open reading frame and, in total, 31 different truncated polypeptides were expressed in Escherichia coli using the T7 expression system. N-Terminal truncations were analyzed for their interaction with the small subunit (R2) of ribonucleotide reductase using a sensitive enzyme-linked immunosorbent assay (ELISA) method and for their ability to complement R2 in ribonucleotide reductase assays. Truncated proteins were also tested for homodimerization using gel-filtration chromatography. The results identified a region of R1 between amino acids 349 and 373 which was essential for subunit interaction. Proteins lacking up to 348 amino-terminal residues associated with R2 and complemented R2 in ribonucleotide reductase assays. Proteins commencing at amino acid 373 and beyond did not interact with R2 and were inactive in enzyme assays. Using a plasmid which expressed an N-terminal deleted protein commencing at amino acid 247, we constructed two defined C-terminal deletions to give proteins comprising amino acids 247-434 and 247-996 of R1. Neither of these truncated proteins bound R2 and we concluded that a second region between amino acids 996 and 1137 (the C-terminus) is required for interaction with R2. Gel-filtration studies indicated that deletion of the first 420 amino acids from R1 did not affect dimerization. However, deletions of 457 amino acids and larger gave proteins which existed as monomers.(ABSTRACT TRUNCATED AT 250 WORDS)

A truncated form of herpes simplex virus type 1 immediate-early protein Vmw110 is expressed in a cell type dependent manner

Herpes simplex virus type 1 (HSV-1) encodes five immediate-early (IE) genes, at least three of which are involved in the regulation of gene expression. Gene IE-1 is one of the few HSV-1 genes whose pre-mRNAs are spliced; the IE-1 pre-mRNA contains two introns, the second of which contains an in-frame stop codon which would terminate IE-1 translation if the intron were not excised. Previous work has shown that plasmids which have been constructed so as to express only the first two exons of Vmw110 can inhibit gene expression in transfection assays, whereas the normal intact protein is an activator of gene expression. In this paper we show that this predicted truncated Vmw110 protein is expressed during normal HSV-1 infection, and that it must be translated from IE-1 pre-mRNAs which retain the in-frame stop codon in the second intron. This truncated product is produced in amounts which depend upon the cell type infected. The possible consequences of these observations are discussed.

Epitope mapping identifies an exposed loop between the unique amino- and conserved carboxy-domains of the large subunit of herpes simplex virus type 1 ribonucleotide reductase

The large subunits of herpes simplex virus types 1 and 2 ribonucleotide reductases contain unique amino-terminal regions comprising 311 and 318 residues respectively, which are not found in ribonucleotide reductases from other sources. We report the mapping of the epitope recognized by monoclonal antibody 1026, which is specific for the large subunit (R1) of HSV-1, and then deduce the structural relationship of the amino-terminal region of R1 with the rest of the protein. A panel of 10 fusion proteins containing sequences spanning the entire R1 subunit were constructed. They were used together with proteolytic fragments of R1 and several synthetic peptides to show that the epitope is discontinuous and appears to be a loop structure centered on a previously located trypsin-sensitive site at residue 305. The existence of the loop was suggested by the observation that reactivity of the antibody with R1 could be blocked by peptides corresponding to residues 289 to 303 and 308 to 313 which flank the trypsin-sensitive site. Our results suggest that the unique amino-terminal region of R1 consists of a structurally distinct domain which is linked to the conserved carboxy region by an exposed loop.

An epitope within the DNA-binding domain of the herpes simplex virus immediate early protein Vmw175 is conserved in the varicella-zoster virus gene 62 protein

We have isolated a panel of monoclonal antibodies that recognize the DNA-binding domain of the herpes simplex virus type 1 (HSV-1) immediate early polypeptide Vmw175. The mice used for the fusions had been immunized with the isolated Vmw175 DNA-binding domain. This had been purified from bacteria that carried a phage T7 expression plasmid with the DNA-binding domain coding region. The epitopes recognized by the monoclonal antibodies were mapped by using a family of truncated versions of the DNA-binding domain, which had also been expressed in the bacterial expression system. The monoclonal antibodies divided into at least four different groups according to this mapping. Several of the monoclonal antibodies recognized Vmw175 expressed in infected BHK cells by HSV-1 strain 17 in Western blots. One of them also recognized the corresponding protein of varicella-zoster virus gene 62. This is further illustration of the relatedness of the two polypeptides.

Effect of fasting, hypocaloric feeding, and refeeding on the energetics of stimulated rat muscle as assessed by nuclear magnetic resonance spectroscopy

A previous study suggested that muscles from hypocalorically fed rats were limited in their ability to rephosphorylate ADP. During muscle contraction hydrolysis of ATP results in an increase in phosphorus, free ADP, delta GATP, and a reduction in phosphocreatine levels that is reversed during rest by rephosphorylation of ADP to ATP and the resynthesis of phosphocreatine by ATP. We therefore hypothesized that these changes would be restored more slowly during postcontraction rest in hypocalorically fed rats as compared with controls. We compared controls fed ad lib to 2-d fasted and hypocalorically fed rats, losing 20% of their weight. We also compared hypocalorically fed rats that had been refed ad lib for 7 d with age-matched controls fed ad lib. The results showed that ATP, muscle pH, and total muscle creatine levels were not different in all groups. The raised phosphorus and delta GATP levels and lower phosphocreatine/phosphorus ratio at the end of contraction changed more slowly during rest in the hypocaloric rats. These abnormalities were partially corrected by refeeding. The data taken as a whole support the concept of impaired rephosphorylation of ADP in malnourished muscle that is not completely restored by refeeding in stimulated muscle.