Procyanidin trimer C1 derived from Theobroma cacao reactivates latent human immunodeficiency virus type 1 provirus

Despite remarkable advances in combination antiretroviral therapy (cART), human immunodeficiency virus type 1 (HIV-1) infection remains incurable due to the incomplete elimination of the replication-competent virus, which persists in latent reservoirs. Strategies for targeting HIV reservoirs for eradication that involves reactivation of latent proviruses while protecting uninfected cells by cART are urgently needed for cure of HIV infection. We screened medicinal plant extracts for compounds that could reactivate the latent HIV-1 provirus and identified a procyanidin trimer C1 derived from Theobroma cacao as a potent activator of the provirus in human T cells latently infected with HIV-1. This reactivation largely depends on the NF-κB and MAPK signaling pathways because either overexpression of a super-repressor form of IκBα or pretreatment with a MEK inhibitor U0126 diminished provirus reactivation by C1. A pan-PKC inhibitor significantly blocked the phorbol ester-induced but not the C1-induced HIV-1 reactivation. Although C1-induced viral gene expression persisted for as long as 48 h post-stimulation, NF-κB-dependent transcription peaked at 12 h post-stimulation and then quickly declined, suggesting Tat-mediated self-sustainment of HIV-1 expression. These results suggest that procyanidin C1 trimer is a potential compound for reactivation of latent HIV-1 reservoirs.

Sulfated polysaccharide, curdlan sulfate, efficiently prevents entry/fusion and restricts antibody-dependent enhancement of dengue virus infection in vitro: a possible candidate for clinical application

Curdlan sulfate (CRDS), a sulfated 1→3-β-D glucan, previously shown to be a potent HIV entry inhibitor, is characterized in this study as a potent inhibitor of the Dengue virus (DENV). CRDS was identified by in silico blind docking studies to exhibit binding potential to the envelope (E) protein of the DENV. CRDS was shown to inhibit the DENV replication very efficiently in different cells in vitro. Minimal effective concentration of CRDS was as low as 0.1 µg/mL in LLC-MK2 cells, and toxicity was observed only at concentrations over 10 mg/mL. CRDS can also inhibit DENV-1, 3, and 4 efficiently. CRDS did not inhibit the replication of DENV subgenomic replicon. Time of addition experiments demonstrated that the compound not only inhibited viral infection at the host cell binding step, but also at an early post-attachment step of entry (membrane fusion). The direct binding of CRDS to DENV was suggested by an evident reduction in the viral titers after interaction of the virus with CRDS following an ultrafiltration device separation, as well as after virus adsorption to an alkyl CRDS-coated membrane filter. The electron microscopic features also showed that CRDS interacted directly with the viral envelope, and caused changes to the viral surface. CRDS also potently inhibited DENV infection in DC-SIGN expressing cells as well as the antibody-dependent enhancement of DENV-2 infection. Based on these data, a probable binding model of CRDS to DENV E protein was constructed by a flexible receptor and ligand docking study. The binding site of CRDS was predicted to be at the interface between domains II and III of E protein dimer, which is unique to this compound, and is apparently different from the β-OG binding site. Since CRDS has already been tested in humans without serious side effects, its clinical application can be considered.

There is no specific approved antiviral and vaccine for treatment or prevention of dengue, an acute mosquito-transmitted viral disease that affects more than 50 million people each year. Dengue virus (DENV) entry is a critical step that establishes the infection and enables virus replication. Curdlan sulfate (CRDS) is known to inhibit the entry and propagation of HIV-1 in the laboratory. Here we applied a computational binding site identification strategy, which suggested that CRDS could be a probable entry inhibitor of the viral surface E protein. CRDS potently blocked DENV infection at an early stage of the virus lifecycle in vitro. In addition, CRDS prevented antibody dependent enhancement, which is considered to be one of the most important clinical observations in DENV-infected patients. CRDS shows a favorable selectivity index against all serotypes of DENV. Further computational docking indicates that the compound binds to a pocket on the DENV E protein. Since CRDS has already been tested in humans without serious side effects, it can be a good candidate for clinical application.

Fully human monoclonal antibody directed to proteolytic cleavage site in severe acute respiratory syndrome (SARS) coronavirus S protein neutralizes the virus in a rhesus macaque SARS model

Background. There is still no effective method to prevent or treat severe acute respiratory syndrome (SARS), which is caused by SARS coronavirus (CoV). In the present study, we evaluated the efficacy of a fully human monoclonal antibody capable of neutralizing SARS-CoV in vitro in a Rhesus macaque model of SARS.

Methods. The antibody 5H10 was obtained by vaccination of KM mice bearing human immunoglobulin genes with Escherichiacoli–producing recombinant peptide containing the dominant epitope of the viral spike protein found in convalescent serum samples from patients with SARS.

Results. 5H10, which recognized the same epitope that is also a cleavage site critical for the entry of SARS-CoV into host cells, inhibited propagation of the virus and pathological changes found in Rhesus macaques infected with the virus through the nasal route. In addition, we analyzed the mode of action of 5H10, and the results suggested that 5H10 inhibited fusion between the virus envelope and host cell membrane. 5H10 has potential for use in prevention and treatment of SARS if it reemerges.

Conclusions. This study represents a platform to produce fully human antibodies against emerging infectious diseases in a timely and safe manner.

Pycnogenol, a procyanidin-rich extract from French maritime pine, inhibits intracellular replication of HIV-1 as well as its binding to host cells

A procyanidin-rich extract from French maritime pine, Pycnogenol(R) (PYC), is known as an antioxidant that exerts a variety of physiological activities and is widely used in human beings. We report here that PYC inhibits not only human immunodeficiency virus type-1 (HIV-1) binding to host cells, but also its replication after entry in susceptible cells in vitro. Prominent biochemical alterations induced by PYC were the elevated expression of an intracellular antioxidant protein, manganese superoxide dismutase (Mn-SOD), and the inhibition of phosphorylation of the ribosomal S6 protein. Interestingly, ectopic expression of Mn-SOD inhibited HIV-1 replication as well. Inhibition of HIV-1 replication associated with induced expression of Mn-SOD in cells treated with PYC suggests the potential of this natural antioxidant inducer as a new anti-HIV-1 agent.

Utilization of host SR protein kinases and RNA-splicing machinery during viral replication

Although the viral genome is often quite small, it encodes a broad series of proteins. The virus takes advantage of the host-RNA-processing machinery to provide the alternative splicing capability necessary for the expression of this proteomic diversity. Serine-arginine-rich (SR) proteins and the kinases that activate them are central to this alternative splicing machinery. In studies reported here, we use the HIV genome as a model. We show that HIV expression decreases overall SR protein/activity. However, we also show that HIV expression is significantly increased (20-fold) when one of the SR proteins, SRp75 is phosphorylated by SR protein kinase (SRPK)2. Thus, inhibitors of SRPK2 and perhaps of functionally related kinases, such as SRPK1, could be useful antiviral agents. Here, we develop this hypothesis and show that HIV expression down-regulates SR proteins in Flp-In293 cells, resulting in only low-level HIV expression in these cells. However, increasing SRPK2 function up-regulates HIV expression. In addition, we introduce SR protein phosphorylation inhibitor 340 (SRPIN340), which preferentially inhibits SRPK1 and SRPK2 and down-regulates SRp75. Although an isonicotinamide compound, SPRIN340 (or its derivatives) remain to be optimized for better specificity and lower cytotoxicity, we show here that SRPIN340 suppresses propagation of Sindbis virus in plaque assay and variably suppresses HIV production. Thus, we show that SRPK, a well known kinase in the cellular RNA-processing machinery, is used by at least some viruses for propagation and hence suggest that SRPIN340 or its derivatives may be useful for curbing viral diseases.

The development of vaccines against SARS corona virus in mice and SCID-PBL/hu mice

We have investigated to develop novel vaccines against SARS CoV using cDNA constructs encoding the structural antigen; spike protein (S), membrane protein (M), envelope protein (E), or nucleocapsid (N) protein, derived from SARS CoV. Mice vaccinated with SARS-N or -M DNA using pcDNA 3.1(+) plasmid vector showed T cell immune responses (CTL induction and proliferation) against N or M protein, respectively. CTL responses were also detected to SARS DNA-transfected type II alveolar epithelial cells (T7 cell clone), which are thought to be initial target cells for SARS virus infection in human. To determine whether these DNA vaccines could induce T cell immune responses in humans as well as in mice, SCID-PBL/hu mice was immunized with these DNA vaccines. As expected, virus-specific CTL responses and T cell proliferation were induced from human T cells. SARS-N and SARS-M DNA vaccines and SCID-PBL/hu mouse model will be important in the development of protective vaccines.

Highly potent anti-HIV-1 activity isolated from fermented Polygonum tinctorium Aiton

A water-soluble extract of fermented Polygonum tinctorium Aiton (Polygonaceae) called Sukumo, exhibited a potent inhibitory activity against HIV type 1 in vitro. The extract potently suppressed acute HIV-1 (III_B) infection in MT-4 cells with EC₅₀ values of 0.5 μg/ml but exhibited low cytotoxicity to MT-4 cells even at a high concentration (CC₅₀ > 1000 μg/ml). It also inhibited giant cell formation in co-cultures of HIV-infected cells and uninfected Molt-4 cells. Sukumo extract was found to interact with both the viral envelope glycoprotein and cellular receptors, thus blocking virus-cell binding and virus-induced syncytium formation. There was a good correlation between the extract's anti-HIV-1 activity and its inhibitory effects on HIV-1 binding. It also suppressed replication of herpes simplex virus type 1 in Vero cells with an EC₅₀ of 11.56 μg/ml. On the other hand, there was no appreciable activity against influenza A virus, poliovirus or SARS corona virus when tested at concentrations ranging from 3.2–400 μg/ml as shown by microscopic image analysis for cytopathic effect (CPE). Physico-chemical studies revealed that the anti-HIV activity in the extract was essentially maintained after boiling at 100 °C in 1N HCl or 1N NaOH, and after treatment with 100 mM NaIO₄. The inhibitory activity of the extract was also not reduced after pronase digestion. The active factor in the extract is likely to be a novel compound(s) having a polyanionic substructure and a molecular weight of 10,000–50,000.

HIV protease inhibitor nelfinavir inhibits replication of SARS-associated coronavirus

A novel coronavirus has been identified as an etiological agent of severe acute respiratory syndrome (SARS). To rapidly identify anti-SARS drugs available for clinical use, we screened a set of compounds that included antiviral drugs already in wide use. Here we report that the HIV-1 protease inhibitor, nelfinavir, strongly inhibited replication of the SARS coronavirus (SARS-CoV). Nelfinavir inhibited the cytopathic effect induced by SARS-CoV infection. Expression of viral antigens was much lower in infected cells treated with nelfinavir than in untreated infected cells. Quantitative RT-PCR analysis showed that nelfinavir could decrease the production of virions from Vero cells. Experiments with various timings of drug addition revealed that nelfinavir exerted its effect not at the entry step, but at the post-entry step of SARS-CoV infection. Our results suggest that nelfinavir should be examined clinically for the treatment of SARS and has potential as a good lead compound for designing anti-SARS drugs.

Effects of mepartricin (S-160) on spontaneous canine benign prostatic hyperplasia

OBJECTIVE

The effects of mepartricin (S-160) on spontaneous canine benign prostatic hyperplasia (BPH) were investigated by histological, histochemical and biochemical analysis.

METHODS

Aged beagle dogs (5-9 years old) with spontaneously developed BPH were treated orally with a placebo or S-160 (5, 10 or 20 mg/kg/day) for 8 weeks. The methodology included measurement of prostatic volume by transrectal ultrasonography, qualitative evaluation of prostatic morphology, determination of plasma and intraprostatic estradiol level by radioimmunoassay and immunohistochemical detection of estrogen receptors and androgen receptors in the prostate.

RESULTS

S-160 significantly reduced the prostatic volume and regressed histologically the hyperplastic grade of prostate, and also fairly decreased the plasma and intraprostatic estradiol concentration and the estrogen and androgen receptors in the prostate.

CONCLUSIONS

These results suggest that the reduction of estradiol and estrogen receptors in the prostate may play a crucial role in the regression of BPH by S-160.

Induction of manganese-superoxide dismutase in MRC-5 cells persistently infected with an alphavirus, sindbis

Sindbis virus (SV), a single-stranded positive-sense RNA virus, multiplies in a variety of cells and causes various outcomes of infection. As we described acute infection of SV induces stress response of small heat shock protein HSP27 and activation of mitogen-activated protein kinase (MAP) signaling pathway (Nakatsue, T., et al., Biochem. Biophys. Res. Commun. 253, 59-64, 1998). In contrast to lytic infection in Vero cells, MRC-5 cells, a human fetus lung cell line, resulted in persistent infection by SV. Here we investigated a cellular factor involved in persistent infection of MRC-5 cells infected with SV. Partial sequence analysis of a 25 kilodalton (kDa) protein, accumulated in large amounts in the cells, showed that manganese-superoxide dismutase (Mn-SOD) was induced during the infections. When Mn-SOD was overexpressed in Vero cells, 20% of the cells survived more than one month, in contrast with the death of 99% of the vehicle-transfected Vero cells at 48 h after infection with SV. These data strongly suggest that a cellular factor which regulates the oxidative pathway modulates the outcome of SV infection.

Effects of mepartricin, a polyene macrolide agent, on fecal excretion and serum concentration of estrogen and number of prostatic estrogen receptors in immature rats

BACKGROUND

Mepartricin, an antifungal agent, was investigated for effects on fecal excretion and serum concentration of sex steroids and the number of sex steroid prostatic receptors in immature rats.

METHODS

Mepartricin was orally administered at 2.5, 5, and 10 mg/kg once daily for 2 weeks. Fecal estrogen and testosterone excretions, serum estrogen, testosterone and luteinizing hormone concentrations, and numbers of prostatic estrogen and androgen receptors were assayed. Prostate weight was also monitored.

RESULTS

Fecal estrogen excretion showed a dose-dependent increase, which was significant for the two higher dosages. Conversely, the serum estrogen concentration and prostatic estrogen receptors were significantly decreased. No significant changes in fecal testosterone excretion, serum testosterone and luteinizing hormone concentrations, and prostatic androgen receptors were observed. Prostate weight was significantly reduced at 5 mg/kg, but we did not observe dose-dependency.

CONCLUSIONS

Mepartricin increases fecal excretion of estrogen by binding with it in the intestinal tract, which results in reducing the serum estrogen concentration and number of prostatic estrogen receptors.

Acute infection of Sindbis virus induces phosphorylation and intracellular translocation of small heat shock protein HSP27 and activation of p38 MAP kinase signaling pathway

In general, viral infection is supposed to induce stress responses in the host cell. However, very few detailed observations about virus-induced stress responses have been reported. Here we investigated specific stress responses in Vero cells infected with Sindbis virus (SV), a single-stranded RNA virus, acute infection with which is known to cause apoptotic cell death in the host cells. Prior to the onset of apoptosis, p38 mitogen-activated protein kinase (MAPK) and c-Jun NH2-terminal kinases (JNKs) were activated. Subsequently, a 27-kDa heat shock protein (HSP27) became phosphorylated, and intracellular distribution of HSP27 was changed from the cytoplasm to the perinuclear region. These results indicate that the cellular signaling cascades activated by pro-inflammatory cytokines and environmental stresses are also activated as a result of lytic infection with SV. These responses may contribute to the delayed onset of apoptosis in the host cells and the facilitation of viral replication.

Ubiquitin is covalently attached to the p6Gag proteins of human immunodeficiency virus type 1 and simian immunodeficiency virus and to the p12Gag protein of Moloney murine leukemia virus

Host proteins are incorporated into retroviral virions during assembly and budding. We have examined three retroviruses, human immunodeficiency virus type 1 (HIV-1), simian immunodeficiency virus (SIV), and Moloney murine leukemia virus (Mo-MuLV), for the presence of ubiquitin inside each of these virions. After a protease treatment to remove exterior viral as well as contaminating cellular proteins, the proteins remaining inside the virion were analyzed. The results presented here show that all three virions incorporate ubiquitin molecules at approximately 10% of the level of Gag found in virions. In addition to free ubiquitin, covalent ubiquitin-Gag complexes were detected, isolated, and characterized from all three viruses. Our immunoblot and protein sequencing results on treated virions showed that approximately 2% of either HIV-1 or SIV p6Gag was covalently attached to a single ubiquitin molecule inside the respective virions and that approximately 2 to 5% of the p12Gag in Mo-MuLV virions was monoubiquitinated. These results show that ubiquitination of Gag is conserved among these retroviruses and occurs in the p6Gag portion of the Gag polyprotein, a region that is likely to be involved in assembly and budding.

Alterations of the cytoskeletal organization in tumor cell lines by a cardiotonic drug, vesnarinone, through protein tyrosine phosphorylation

We describe nonspecific and moderate activation of cellular protein tyrosine phosphorylation by a chemical compound, vesnarinone, which results in enhanced synthesis and/or assembly of cytoskeletal proteins and morphological alterations in several transformed cells. In A431 cells, vesnarinone induced tyrosine phosphorylation of the overexpressed epidermal growth factor receptors (EGFR) as well as other unidentified proteins, increased the synthesis of cytokeratins, and caused amplification of the intermediate filament networks and cell flattening. The drug effects were abolished by tyrphostin, a protein tyrosine kinase inhibitor. Two other cell lines responded to the drug with increased synthesis of a cell type-specific cytoskeletal protein: vimentin in QG56 human lung carcinoma cells and alpha-tubulin in NIH3T3 cells transformed with v-src. In all cell lines tested, the drug-induced tyrosine phosphorylation was localized in cell-cell and cell-substrate contacts as detected by immunofluorescent staining. Responsive protein substrates and their sensitivity to the drug varied from one cell line to another as observed by immunoblot analysis. Vesnarinone exerted neither activating nor inhibitory effect on in vitro enzyme reactions including EGFR tyrosine kinase, v-src kinase, and protein tyrosine phosphatases. This suggests that vesnarinone indirectly activates tyrosine phosphorylation of membrane proteins related to cell adhesion, which influences a signaling pathway linked to the stress fiber assembly in certain cell lines. The possible mechanism by which vesnarinone induces the cellular responses is discussed.

How the developing septo-preoptic medical basal hypothalamus stimulates the development of placode-derived LHRH neurons

We examined the effects of the developing cerebral cortex (CC) and septo-preoptic medial basal hypothalamus (S-MBH) on the development of LHRH neurons in vitro. The serum-free basal culture medium (BCM) was supplemented with CC or S-MBH extracts prepared from 18.5-day-old embryos or from 2-day-old newborns, and the olfactory placode (NAP) of 12-day-old embryos was cultured. The migration of LHRH neurons was found on Day 3 in the cultures supplemented with the embryonic S-MBH extract (Group 3), where the cell development proceeded showing a numerical increase of the cells and the elongation of neurites. In cultures supplemented with the newborn S-MBH extract (Group 5), the cell development was less intensive in comparison with that of Group 3, while in cultures which had no brain extracts (Group 1), the neurons failed to survive a long term culture. The effects of the CC were less than of S-MBH extracts. Analysis of the protein composition of the extracts by electrophoretic and immunoblotting examinations demonstrated a protein spot of 70-kD in the embryonic S-MBH extract. Because the protein spot was identified to be alpha-fetoprotein (AFP), we further examined the effects of AFP. When the anti-AFP immunoglobulin was added to the Group 3 culture, the stimulative effects of the embryonal extract were inhibited, and the addition of AFP to Group 1 cultures did not show stimulative effects. We conclude that the developing S-MBH, the migrating target of LHRH neurons, contains some essential factors for the development of LHRH neurons, but further analysis is needed to determine the chemical natures of these factors.

Entrapment and inhibition of human immunodeficiency virus proteinase by alpha 2-macroglobulin and structural changes in the inhibitor

The inhibitory effect of alpha 2-macroglobulin (alpha 2M), a major plasma proteinase inhibitor, on human immunodeficiency virus (HIV) proteinase was investigated. The activity of HIV proteinase toward the Moloney murine sarcoma virus-derived gag protein (a high-molecular-mass substrate) was found to be inhibited by alpha 2M at pH 5.5-7.4. On the other hand, the activity toward the B chain of oxidized insulin (a low-molecular-mass substrate) was scarcely inhibited. The complex of alpha 2M and HIV proteinase was isolated by gel filtration and the enzyme was shown to be significantly protected by the complex formation from autoinactivation under nonreducing conditions. The stoichiometry of the complex formation was found to be 2:1 (enzyme: alpha 2M, mol/mol). These results demonstrate the entrapment and concomitant inhibition of HIV proteinase by alpha 2M.

Bovine leukemia virus RNA sequences involved in dimerization and specific gag protein binding: close relation to the packaging sites of avian, murine, and human retroviruses

In vitro detection of a specific complex of the bovine leukemia virus (BLV) MA(p15) protein and the 5'-terminal RNA dimer led to the hypothesis that the NH2-terminal domain of retrovirus gag protein precursor is involved in the selective viral RNA packaging mechanism. Here we describe mapping of the BLV RNA for dimer-forming and MA(p15)-binding abilities by a simple cDNA probing method followed by mutation analyses with the reactive U5-5' gag RNA. The RNA dimerization is mediated by the region harboring U5, the primer binding site (PBS), and the 30 bases immediately downstream of PBS. This conclusion is supported by computer-assisted RNA secondary-structure analysis which predicted a multibranched stem-loop folding throughout the dimer region determined. Another region from PBS to the 5'-terminal 60 residues of the gag gene, partially overlapping the dimer region, likely provides essential elements for the MA(p15) binding reaction, although the presence of either the 3' or 5' neighboring sequences increases the complex-forming efficiency significantly, and each of the substructures predicted within the core region has, if any, only very weak affinity to MA(p15). These in vitro characterizations of the BLV RNA may reflect general features of the specific protein-RNA interaction in the packaging events of various retroviruses. 5'-terminal folded structures of retroviral RNA molecules and their biological activities are discussed.

The role of the Maternal and Child Health Handbook system in reducing perinatal mortality in Japan

OBJECTIVE

The purpose of this paper is to demonstrate the direct and indirect roles of the Maternal and Child Health (MCH) Handbook in promoting overall improvement in maternal health and child care and to attempt to clarify the relationship between the use of the MCH Handbook and the reduced perinatal mortality in Japan. Another important objective is to propose possible future applications of the MCH Handbook, especially with respect to the networking function of providing client-care provider feedback, and the exchange of health data between the authorities and relevant medical societies.

RESULTS

Japan has achieved a decline in neonatal mortality in the 30-year period from 1960 to 1990, from 17.0 to 2.6 per 1,000 live births. There is a correlation between the ratio of the number of Handbooks distributed and the actual number of births and the perinatal mortality.

CONCLUSIONS

The wide use of the MCH Handbook system seems to have played an important role in bringing about this reduction and in maintaining the figure as one of the lowest in the world. The reduction of perinatal mortality through the use of the MCH Handbook in this country suggests a similar possibility for application in other nations. The Handbook could aid in the early recognition of high-risk pregnancy and thus reduce inappropriate use of medical resources. The system, with the establishment of a feedback system between the client and the authorities via the care provider, may improve health care in such areas as maternal mortality, toxemia of pregnancy, and diabetes mellitus.

In vitro accurate transcription from the cap site of bovine leukemia virus (BLV) dependent on the BLV-infected cell nuclear lysate

The cell-free transcriptional system initiating from the cap site in bovine leukemia virus (BLV) LTR by RNA polymerase II was constructed. The transcription was completely dependent on the template DNA and the nuclear lysate isolated from BLV-infected bat lung cells (TB1Lu). The relative transcriptional rates estimated using several deletion mutants around the promoter sequence in BLV LTR as templates closely corresponded to that obtained by transient expression assay in cultured cells using these plasmids and tax-producing plasmid. The partial purification of the factor(s) involving to the transcriptional activation from the nuclear lysate suggested that the factor(s) was different from tax and rex, the regulatory factors encoded on viral genome. The transcription from the caps site of adenovirus E3 was also stimulated in the presence of the nuclear lysate from BLV-infected cells.

[Quality management in healthcare. Evaluation and improvement]

Quality in healthcare is a concept ultimately determined by the satisfaction of the patient, or more broadly stated, society's needs. Improvement in quality begins with the review of health care organizations, in the degree to which their current role and function can and do meet these needs. Recent trends in quality evaluation have been along the lines of patients satisfaction, as well as structure, process, and outcome oriented aspects of health care delivery. Quality entails not only the science of medicine itself, but also health care delivery, as well as social and individual concerns. In 1990, Japan Hospital Quality Assurance Society was founded. The secretariat is located at this department. Currently, more than 60 hospitals participate for the development of standards and survey to the hospitals. The quality improvement effort has slowly begun to put the concept into practice. The public's growing concern is directed toward holding healthcare organizations accountable for the services they provide. The healthcare field, in turn, is recognizing the needs and merit of voluntary commitment to quality, and are placing emphasis on identifying pressing society needs, and developing effective leadership. Moving the entire healthcare field in the direction of continuous quality improvement will be the key to the survival into the 21st century.

Bovine leukemia virus matrix-associated protein MA(p15): further processing and formation of a specific complex with the dimer of the 5'-terminal genomic RNA fragment

The retrovirus precursor protein has an arrangement of several characteristic domains with which it achieves selective and efficient packaging of the genome RNA during particle assembly. In this study, we analyzed the composition of the bovine leukemia virus (BLV) gag proteins and examined their RNA-binding properties in gel mobility shift assays, using various genomic RNA probes synthesized in vitro. Results obtained in amino acid sequence and composition analyses indicate that the matrix-associated protein MA(p15) is further processed by the BLV protease (PR) to generate MA(p10), a short peptide of seven amino acid residues, and p4. The gag precursor is now mapped as NH2-MA(p10)-p4-CA(p24)-NC(p12)-COOH. MA(p15) formed a specific complex with the dimer RNA of the U5-5' gag region presumed to contain the BLV packaging signal but not with other RNAs. The NH2-terminal cleavage product, MA(p10), bound all RNA fragments tested, while the COOH-terminal peptides with a sequence common to mammalian type C retroviruses had little affinity for RNA. The nucleocapsid protein NC(p12) bound to RNAs nonspecifically and randomly in the presence or absence of zinc ions. These results suggest a possible interaction of the NH2 terminus of the gag precursor with the 5' terminus of the genomic RNA in an early phase of particle assembly, when the conserved structure between the MA and CA domains might be involved.

Retrovirus protease characterized as a dimeric aspartic proteinase

Retroviruses and retroviruslike elements have a protease for specific cleavage of their polyprotein precursors. On the basis of amino acid sequences conserved among species and the sensitivity to protease inhibitors, it was proposed that the retrovirus protease could be classified as an aspartic proteinase. Since the virus protease molecule is comparable to a single domain of aspartic proteinases having two symmetrical domains, we hypothesized and examined the dimer formation of the protease. The results of biochemical molecular mass determination and cross-linking experiments demonstrated that the virus protease molecules self-assemble into dimers. An inhibitory effect of fragmented protease molecules suggests the possibility that the intermolecular association is required for their activity. Other experiments of chemical inactivation suggest a close resemblance of the catalytic features of retrovirus and aspartic proteinases. Characterizations of these bovine and avian virus proteases would provide basic knowledge for the design of retrovirus protease-specific inhibitors, which is one of the possible strategies against human immunodeficiency virus infection.

Bovine leukemia virus trans-activator p38tax activates heterologous promoters with a common sequence known as a cAMP-responsive element or the binding site of a cellular transcription factor ATF

The genome of bovine leukemia virus (BLV) encodes a transcriptional trans-activator p38tax (also referred to as pXBL-I) which amplifies the virus gene expression driven by its long terminal repeat (LTR). It was proposed that activation of cellular gene expression by p38tax might be involved in the mechanism of B-cell transformation caused in vivo by BLV infection. Here, we report that the U3 region of BLV LTR contains multiple regulatory elements responsive to p38tax. A core element composing the p38tax-inducible U3 structure is suggested to be a heptanucleotide motif of 5'TGACGTCA3', the consensus sequence proposed for a cAMP-responsive element (CRE) and for the binding sites of a cellular transcription factor (ATF). Adenovirus-5 E3 and E4, c-fos and somatostatin regulatory regions containing CRE/ATF-element exhibited responsiveness to p38tax in a chloramphenicol acetyltransferase transient expression assay. These suggest that in BLV-infected cells, cellular gene expression might be induced abnormally by the virus trans-activator through ATF or ATF-like factors.

Inhibition of retroviral protease activity by an aspartyl proteinase inhibitor

Retrovirus protease is an enzyme that cleaves gag and gag-pol precursor polyproteins into the functional proteins of mature virus particles. The correct processing of precursor polyproteins is necessary for the infectivity of virus particles: in vitro mutagenesis which introduces deletions into the murine leukaemia virus genome produces a protease-defective virus of immature core form and lacking infectivity. A therapeutic drug effective against disease caused by retrovirus proliferation could likewise interfere with virus maturation. The primary structure has so far been determined for the protease of avian myeloblastosis virus, and of murine, feline and bovine leukaemia viruses. Amino acid sequencing of the retrovirus proteases, either after their purification or from prediction from the nucleotide sequence, shows that they possess the Asp-Thr-Gly sequence characteristic of the aspartyl proteinases. In this report we show that retrovirus proteases belong to the aspartyl proteinase group and demonstrate an inhibition by the aspartyl proteinase-specific inhibitor, pepstatin A, on the activity of bovine leukaemia, Moloney murine leukaemia and human T-cell leukaemia virus proteases.

The bovine leukemia virus X region encodes a trans-activator of its long terminal repeat

We constructed a fusion plasmid, pMX-I, by which the major open reading frame, X-I, of the bovine leukemia virus (BLV) X gene was expressed under control of the mouse metallothionein promoter. pMX-I was cotransfected into CV1 monkey kidney cells together with another construct containing the BLV long terminal repeat (LTR) linked to the chloramphenicol acetyltransferase (CAT) structural gene. The result of assay of CAT synthesis suggests that the X-I product functions as a trans-acting activation factor of the BLV LTR.

Inhibition of 3,4-diaminopyridine-induced coronary oscillation by adenyl compounds

3,4-Diaminopyridine (DAP) contracted the isolated canine coronary arteries rhythmically. Together with the contractions, plateau potentials which were often preceded by spike-like potentials were recorded with glass microelectrodes. Adenosine inhibited both the DAP-induced contraction and the depolarization. ATP, ADP and AMP inhibited the contraction similarly. Cyclic AMP had a slight inhibitory effect on the contraction and dibutyryl cyclic AMP had no effect on it. Aminophylline antagonized the inhibitory effect of adenosine, ATP and ADP. Dilazep potentiated the effect of adenosine and indomethacin did not affect it. These results show that adenosine occupies the P1-purinoceptor and blocks the DAP-induced repetitive contractions of isolated canine coronary arteries by suppressing the rhythmic depolarization.

The effect of cerulenin on Moloney murine leukemia virus morphogenesis

Cerulenin is an antibiotic that interferes with fatty acid synthesis in eukaryotic cells. It had been shown by Schultz and Oroszlan (1983), that murine leukemia virus (MuLV) Pr65gag, the polyprotein precursor to the virion core proteins contains the fatty acid myristate at its NH2 terminus. We showed that when 20 micrograms/ml of cerulenin is added for 3 h to mouse fibroblasts chronically infected with Moloney (M)-MuLV it causes a greater than 4-fold decrease in virus production. This is accompanied by an accumulation of uncleaved Pr65gag in the infected cells. Further, thin-section electron micrographs of cerulenin-treated cells show a 2-fold increase in the number of nascent-budding forms, as well as the appearance of aberrant viral forms at the cell membrane. This suggests that the failure to add myristic acid to Pr65gag prevents their proper assembly into viral particles.

Bovine leukemia virus protease: purification, chemical analysis, and in vitro processing of gag precursor polyproteins

Bovine leukemia virus protease was purified to homogeneity and assayed by using murine leukemia virus Pr65gag, a polyprotein precursor of the viral core structural proteins, as the substrate. A chemical analysis of the protease, including an amino acid composition and NH2- and COOH-terminal amino acid sequence analysis, revealed that it has an Mr of 14,000 and is encoded by a segment of the viral RNA located between the gag gene and the putative reverse transcriptase gene. As expected from the nucleotide sequence data (Rice et al., Virology 142:357-377, 1985), the reading frame for the protease is different from both the gag and reverse transcriptase reading frames. The 5' end of the protease open reading frame extends 38 codons upstream from the codon for the NH2-terminal residue of the mature viral protease and overlaps the gag open reading frame by 7 codons. The 3' end of the protease open reading frame extends 26 codons beyond the codon for the COOH-terminal residue of the mature protease and overlaps 8 codons of the reverse transcriptase open reading frame. Several lines of evidence, such as protein mapping of the gag polyprotein precursor, the characteristic structure of the mRNA, and promotion of the synthesis of a gag polyprotein precursor by lysine tRNA in vitro, suggest that the protease could be translated by frameshift suppression of the gag termination codon. In vitro synthesized bovine leukemia virus gag-related polyproteins were cleaved by the protease into fragments which were the same size as the known components of bovine leukemia virus, suggesting that the specificity of cleavage catalyzed in vitro by the purified protease is the same as the specificity of cleavage found in the virus.

Analysis by electrophoretic transfer blotting of Japanese cedar pollen allergens which react with IgG and IgE antibodies in the serum of patients

Crude extract of Japanese cedar pollen was fractionated by DEAE-cellulose chromatography to separate the major allergenic components. In order to analyze which antigens react with IgG or IgE antibodies in the serum of Japanese cedar pollinosis patients, an electrophoretic transfer blotting was performed. Both IgE and IgG antibodies reacted with several common antigens, while IgG additionally reacted with some low-molecular-weight proteins.

Antibody assay of rabbit sera for outer membrane vesicles of Haemophilus influenzae by enzyme-linked immunosorbent assay

Enzyme-linked immunosorbent assay (ELISA) was applied to the detection of IgG and IgM antibodies against outer membrane vesicles (OMV) antigen of Haemophilus influenzae type b. In this ELISA system, IgG antibody titers were about 40 fold higher than those in indirect hemagglutination assay (IHA). The IgG antibody titers by this ELISA of rabbit sera obtained after immunization were comparable with those by radioimmunoassay (RIA) of the same sera. A significant correlation was established between these two assays (r = 0.973, P less than 0.001).

Murine leukemia virus maturation: protease region required for conversion from "immature" to "mature" core form and for virus infectivity

Murine leukemia virus (MuLV) genome encodes a protease (Y. Yoshinaka, I. Katoh, T.D. Copeland, and S. Oroszlan (1985), Proc. Natl. Acad. Sci. USA 82, 1618-1622), which has been shown to cause maturation, specified as morphological conversion from "immature" to "mature" form of virus cores. To examine whether "immature" particles have infectivity or not, we constructed mutant DNAs with deletions in the protease region. The NIH/3T3 cells transfected with mutant DNAs produced "immature" particles, having immature morphology and containing Pr65gag, a polyprotein precursor of core proteins. The specific infectivity of the extracellularly released and purified particles was shown to be greatly reduced based on reverse transcriptase activity and protein content as compared with the "mature" particles obtained from wild-type DNA-transfected cells. The mutant genomes encoded functionally normal surface glycoprotein, gp70. These results strongly suggest that maturation of MuLV from "immature" to "mature" form of virus particles is indispensable to virus infectivity. The importance of processing of gag and pol, as well as transmembrane protein precursors by the viral protease is discussed.

Bovine leukemia virus post-envelope gene coded protein: evidence for expression in natural infection

Partial sequence analysis of a 14 kilodalton protein (p14), synthesized by in vitro translation of bovine leukemia virus genomic RNA, showed that it is encoded in the 'X' region of proviral DNA, located between the env gene and the 3' long terminal repeat. The 'X' gene contains a short and a long open reading frame (X-SORF and X-LORF) which overlap. BLV p14x is specified by X-SORF and not X-LORF as seen with the related human T-cell leukemia virus which expresses p38-40x. Antibodies in sera from animals with BLV induced tumors were shown to recognize p14x. Expression of this protein in natural infection might be important for virus replication and/or for BLV induced oncogenesis.

Murine leukemia virus protease is encoded by the gag-pol gene and is synthesized through suppression of an amber termination codon

We have purified from Moloney murine leukemia virus (Mo-MuLV) a protease that has the capacity of accurately cleaving the polyprotein precursor Pr65gag into the mature viral structural proteins. Both the NH2- and COOH-terminal amino acid sequences have been determined and aligned with the amino acid sequence deduced from the DNA sequence of Mo-MuLV by other workers. The results show that: (i) the protease is located at the 5' end of the pol gene, and the first four amino acids are overlapped with the 3' end of the gag gene; (ii) the fifth amino acid residue is glutamine, which is inserted by suppression of the UAG termination codon at the gag-pol junction; and (iii) the protease is composed of 125 amino acids with calculated Mr = 13,315, and the COOH terminus of the protease is adjacent to the NH2 terminus of reverse transcriptase. The map order of the gag-pol gene is proposed to be 5'-p15-p12-p30-p10-protease-reverse transcriptase-endonuclease-3'.

In vitro cleavage of Pr65gag by the Moloney murine leukaemia virus proteolytic activity yields p30 whose NH2-terminal sequence is identical to virion p30

In vitro cleavage of Gazdar murine sarcoma virus Pr65gag, which has all of the antigenic determinants of Moloney murine leukaemia virus Pr65gag, i.e. p15, p12, p30 and p10, by the Moloney murine leukaemia virus proteolytic activity yielded a p30 whose partial NH2-terminal sequence was identical to Moloney murine leukaemia virus. Both [3H]leucine-labelled and unlabelled Pr65gag were used to generate the cleaved p30.

Murine retrovirus Pr65gag forms a 130K dimer in the absence of disulfide reducing agents

Gazdar-murine sarcoma virus (Gz-MSV) particles, obtained from tissue culture fluids of chronically infected HTG-2 hamster cells are immature in morphology and contain uncleaved Pr65gag as the predominant protein (greater than 95% Coomassie blue stain) (A. Pinter and E. deHarven, 1979, Virology 99, 103-110; Y. Yoshinaka and R. B. Luftig, 1982, Virology 118, 380-388). When Gz-MSV particles are disrupted in 1% sodium dodecyl sulfate (SDS) and then analyzed by SDS-polyacrylamide gel electrophoresis (PAGE) in the absence of reducing agents, such as beta-mercaptoethanol (beta-MSH) almost half of the Pr65gag Coomassie blue-stained band is detected as a band at a Mr of 130K. Electrophoretic blotting studies with monospecific antisera against MuLV p30, p15, p12, and p10 showed that the 130K band cross-reacted with all four antigens suggesting that it was a dimer of Pr65gag. Two-dimensional (2D) SDS-PAGE where the first dimension was run under nonreducing conditions and the second with beta-MSH, supported the contention that the 130K band was a dimeric complex of Pr65gag. One also saw minor amounts of a 260K and higher polymeric forms of Pr65gag on the SDS gels, suggesting that polymeric forms may exist as well. When 32P-labeled Gz-MSV particles obtained by in vivo labeling of infected HTG-2 cells with [32P]PPi were electrophoresed on SDS-PAGE, only 10% of the 32P label was detected at the 130K position. In contrast, 30% of the Coomassie blue-stained Pr65gag material was found at 130K on the 2D gels. This suggests that unphosphorylated Pr65gag is more likely to participate in dimer formation than phosphorylated Pr65gag. Pr65gag of Moloney murine leukemia virus (M-MuLV), which is present as a minor (5% of stain) protein band on SDS-PAGE also showed 130K dimers. Further, in beta-MSH-deficient SDS preparations of Gz-MSV, electrophoresed after trypsin treatment, a 32K band that stained with p15, but not p10, p12, nor p30, antisera was observed. If beta-MSH was added, this band was no longer present. Thus Pr65gag dimerization in immature MuLV particles appears to at least involve the p15 region of the polyprotein. Since p15 is an extremely hydrophobic protein, formation of Pr65gag dimers may occur when virion precursor proteins are brought to the cell membrane during virus assembly.

Murine leukaemia virus p30 heterogeneity as revealed by two-dimensional gel electrophoresis is not an artefact of the technique

We have utilized two-dimensional (2D) gel electrophoresis [the first dimension being a linear pH gradient (5 to 8) and the second and 8 to 15% acrylamide gradient] to characterize the virion protein, p30, from several strains of purified murine leukaemia virus (MuLV). In all cases, we found that there was a predominant (70 to 90%) Coomassie Brilliant Blue-staining p30 spot, as well as several other species which differed in pI. The major p30 spot differed in pI among different MuLV strains and the minor spots varied depending on the host cell used to grow the virus. Specifically, (i) Moloney (M)-MuLV/NIH-3T3 showed two spots, a major one at pI 6.3 and a more acidic one, (ii) AKR/NIH-3T3, AKR/mouse embryo, and Gross/NIH-3T3 showed four spots, with the two basic, minor spots of AKR/NIH-3T3 appearing relatively decreased in intensity, and (iii) Rauscher (R)-MuLV/JLS-V9 (BALB/c) showed two spots, a major one with greater than 90% of the estimated Coomassie Brilliant Blue stain at a pI of 6.5 and a minor, acidic one. The major spots of AKR and M-MuLV viruses also differed in pI. The major spot of the AKR and Gross N-tropic viruses had a pI of 6.7 while that of NB-tropic virus M-MuLV had a pI of 6.3. The possibility that the heterogeneity observed in p30 was an artefact of the 2D gel technique had to be considered since urea was used to denature proteins in the first dimension of the gel. This possibility was made unlikely by our finding that another technique, chromatofocusing, gave the same results. Specifically, M-MuLV/JLS-V9 p30, when separated on chromatofocusing columns under non-denaturing conditions yielded three peaks, each of which directly corresponded to the three spots (pI: 6.1, 6.3, 6.6) observed on 2D gels. Furthermore, tryptic peptide maps of the major (pI 6.3) and one of the minor (pI 6.6) M-MuLV spots, although very similar in peptide composition, showed about five clearly defined differences. These results indicate (i) that the p30s of several N- and NB-tropic viruses are heterogeneous in pI, and (ii) for one particular MuLV, the p30 heterogeneity can be explained by a difference in amino acid composition. These findings of p30 charge heterogeneity may reflect either the presence of several different p30s in each virus particle and/or a heterogeneity in the virus population.

Separation of a murine leukaemia virus protein kinase activity from its Pr65gag polyprotein substrate after DNA--cellulose chromatography

We have recently found that, in vitro, the murine leukaemia virus (MuLV)-associated protein kinase activity predominantly phosphorylates Pr65gag, a virus protein present in relatively small amounts in partially purified virus preparations. Other virus proteins, such as p10, Pr27gag and Pr40gag, are also phosphorylated in vitro, but to a lesser degree. Furthermore, when immature core subparticles which are enriched in Pr65gag are prepared from virions by Sepharose 6B exclusion column chromatography, about 50% of the kinase activity (as assayed with the exogenous substrate phosvitin) remains associated with the cores. We report here that this core-associated activity is distinct from Pr65gag since it can be separated from Pr65gag by chromatography on denatured DNA--cellulose columns followed by centrifugation of the 0.2 M-NaCl-eluted fraction. Under these conditions, Pr65gag is pelleted while the kinase activity, which can phosphorylate both endogenous (MuLV Pr65gag and p10) as well as exogenous (phosvitin) substrates, remains in the supernatant. Interestingly, when the amount of Pr65gag is reduced, as in such preparations, p10 then becomes more heavily phosphorylated.