Minimally constrained model of self-organized helical states in reversed-field pinches.

We show that the self-organized single-helical-axis (SHAx) and double-axis (DAx) states in reversed field pinches can be reproduced in a minimally constrained equilibrium model using only five parameters. This is a significant reduction on previous representations of the SHAx which have required an infinite number of constraints. The DAx state, which has a nontrivial topology, has not previously been reproduced using an equilibrium model that preserves this topological structure. We show that both states are a consequence of transport barrier formation in the plasma core, in agreement with experimental results. We take the limit of zero pressure in this work, although the model is also valid for finite pressure.

Heterozygosity for a defective gene for CC chemokine receptor 5 is not the sole determinant for the immunologic and virologic phenotype of HIV-infected long-term nonprogressors.

HIV-1-infected long-term nonprogressors are a heterogeneous group of individuals with regard to immunologic and virologic markers of HIV-1 disease. CC chemokine receptor 5 (CCR5) has recently been identified as an important coreceptor for HIV-1 entry into CD4+ T cells. A mutant allele of CCR5 confers a high degree of resistance to HIV-1 infection in homozygous individuals and partial protection against HIV disease progression in heterozygotes. The frequency of CCR5 heterozygotes is increased among HIV-1- infected long-term nonprogressors compared with progressors; however, the host defense mechanisms responsible for nonprogression in CCR5 heterozygotes are unknown. We hypothesized that nonprogressors who were heterozygous for the mutant CCR5 gene might define a subgroup of nonprogressors with higher CD4+ T cell counts and lower viral load compared with CCR5 wild-type nonprogressors. However, in a cohort of 33 HIV-1-infected long-term nonprogressors, those who were heterozygous for the mutant CCR5 gene were indistinguishable from CCR5 wild-type nonprogressors with regard to all measured immunologic and virologic parameters. Although epidemiologic data support a role for the mutant CCR5 allele in the determination of the state of long-term nonprogression in some HIV-1- infected individuals, it is not the only determinant. Furthermore, long-term nonprogressors with the wild-type CCR5 genotype are indistinguishable from heterozygotes from an immunologic and virologic standpoint.

Isolation of HIV-1 from plasma of infected individuals: an analysis of experimental conditions affecting successful virus propagation.

Experimental conditions affecting the successful propagation of HIV-1 from the plasma of seropositive individuals were examined. It was determined that whole blood samples collected with lithium heparin as the anticoagulant, immediate plasma separation, and immediate culturing were best suited for obtaining viable virus from plasma. Virus was isolated by infecting fresh phytohemagglutinin-stimulated normal donor peripheral blood mononuclear cells (PBMCs) with plasma followed by weekly cocultivation with new target cells. The plasma virus isolation rate was the greatest and HIV-1 titers were the highest for those individuals with less than 200 CD4+ cells/mm3 and decreased as the level of CD4+ cells approached normal values. We were able to obtain positive cultures from 29.5% of those patients with CD4+ counts greater than 500/mm3. HIV-1 titers in plasma also correlated with high serum p24 antigen levels when serum was treated with glycine to dissociate antigen-antibody complexes.

Metamorphosis of plasma turbulence-shear-flow dynamics through a transcritical bifurcation.

The structural properties of an economical model for a confined plasma turbulence governor are investigated through bifurcation and stability analyses. A close relationship is demonstrated between the underlying bifurcation framework of the model and typical behavior associated with low- to high-confinement transitions such as shear-flow stabilization of turbulence and oscillatory collective action. In particular, the analysis evinces two types of discontinuous transition that are qualitatively distinct. One involves classical hysteresis, governed by viscous dissipation. The other is intrinsically oscillatory and nonhysteretic, and thus provides a model for the so-called dithering transitions that are frequently observed. This metamorphosis, or transformation, of the system dynamics is an important late side-effect of symmetry breaking, which manifests as an unusual nonsymmetric transcritical bifurcation induced by a significant shear-flow drive.

Statistical characterization of the interchange-instability spectrum of a separable ideal-magnetohydrodynamic model system.

A Suydam-unstable circular cylinder of plasma with periodic boundary conditions in the axial direction is studied within the approximation of linearized ideal magnetohydrodynamics (MHD). The normal mode equations are completely separable, so both the toroidal Fourier harmonic index n and the poloidal index m are good quantum numbers. The full spectrum of eigenvalues in the range 1< or = m < or = m(max) is analyzed quantitatively, using asymptotics for large m, numerics for all m, and graphics for qualitative understanding. The density of eigenvalues scales like m(2)(max) as m(max) -->infinity . Because finite-m corrections scale as 1/ m(2)(max) , their inclusion is essential in order to obtain the correct statistics for the distribution of eigenvalues. Near the largest growth rate, only a single radial eigenmode contributes to the spectrum, so the eigenvalues there depend only on m and n as in a two-dimensional system. However, unlike the generic separable two-dimensional system, the statistics of the ideal-MHD spectrum departs somewhat from the Poisson distribution, even for arbitrarily large m(max) . This departure from Poissonian statistics may be understood qualitatively from the nature of the distribution of rational numbers in the rotational transform profile.

Quasilinear theory of collisionless Fermi acceleration in a multicusp magnetic confinement geometry.

Particle motion in a cylindrical multiple-cusp magnetic field configuration is shown to be highly (though not completely) chaotic, as expected by analogy with the Sinai billiard. This provides a collisionless, linear mechanism for phase randomization during monochromatic wave heating. A general quasilinear theory of collisionless energy diffusion is developed for particles with a Hamiltonian of the form H0+H1, motion in the unperturbed Hamiltonian H0 being assumed chaotic, while the perturbation H1 can be coherent (i.e., not stochastic). For the multicusp geometry, two heating mechanisms are identified-cyclotron resonance heating of particles temporarily mirrortrapped in the cusps, and nonresonant heating of nonadiabatically reflected particles (the majority). An analytically solvable model leads to an expression for a transit-time correction factor, exponentially decreasing with increasing frequency. The theory is illustrated using the geometry of a typical laboratory experiment.

Strong "quantum" chaos in the global ballooning mode spectrum of three-dimensional plasmas.

The spectrum of ideal magnetohydrodynamic (MHD) pressure-driven (ballooning) modes in strongly nonaxisymmetric toroidal systems is difficult to analyze numerically owing to the singular nature of ideal MHD caused by lack of an inherent scale length. In this paper, ideal MHD is regularized by using a k-space cutoff, making the ray tracing for the WKB ballooning formalism a chaotic Hamiltonian billiard problem. The minimum width of the toroidal Fourier spectrum needed for resolving toroidally localized ballooning modes with a global eigenvalue code is estimated from the Weyl formula. This phase-space-volume estimation method is applied to two stellarator cases.

Synthesis and processing of human immunodeficiency virus type 1 envelope proteins encoded by a recombinant human adenovirus.

A recombinant adenovirus was constructed by inserting the human immunodeficiency virus type 1 (HIV-1) envelope gene downstream from the early region 3 (E3) promoter of adenovirus type 5 (Ad5), replacing the coding sequences of E3. The recombinant virus replicated as efficiently as the parent virus in all cell lines tested. Human cells infected with the recombinant virus synthesized the HIV-1 envelope precursor gp160, which was efficiently processed to the envelope glycoproteins gp120 and gp41. A human T-lymphoblast line (Molt-4) infected with the recombinant virus expressed HIV-1 envelope glycoproteins on the cell surface, leading to syncytium formation. The envelope gene was expressed from the E3 promoter at early times after infection and at late times from the major late promoter. When cotton rats were infected with the recombinant virus, antibodies against the HIV-1 envelope glycoproteins could be expressed in an immunoreactive form by the recombinant adenovirus, further illustrating the usefulness of adenoviruses as expression vectors.

Biosynthesis and processing of human immunodeficiency virus type 1 envelope glycoproteins: effects of monensin on glycosylation and transport.

When human immunodeficiency virus type 1 envelope glycoproteins were expressed in 293 cells by using a recombinant adenovirus expression vector, the envelope precursor (gp160) was initially glycosylated by cotranslational addition of N-linked high-mannose oligosaccharide units to the protein backbone and then cleaved to gp120 and gp41. The subunits gp120 and gp41 were then further modified by the addition of fucose, galactose, and sialic acid, resulting in glycoproteins containing a mixture of hybrid and complex oligosaccharide side chains. A fraction of glycosylated gp160 that escaped cleavage was further modified by the terminal addition of fucose and galactose, but the addition of sialic acid did not occur, consistent with the notion that it is compartmentalized separately from the gp120 envelope protein. Processing and transport of gp160 were blocked by the monovalent ionophore monensin, which at high concentrations (25 microM and above) was a potent inhibitor of the endoproteolytic cleavage of gp160; at lower concentrations (1 to 10 microM), it selectively blocked the secondary glycosylation steps so that smaller products were produced. Monensin (1 microM) treatment also resulted in a reduction in syncytium formation, which was observed when recombinant infected cells were cocultivated with CD4-bearing HeLa cells. The infectivity of human immunodeficiency virus type 1 was also reduced by monensin treatment, a decrease that may be due to incompletely glycosylated forms of gp120 that have a lower affinity for the CD4 receptor.

Comparison of the Quantiplex version 3.0 assay and a sensitized Amplicor monitor assay for measurement of human immunodeficiency virus type 1 RNA levels in plasma samples.

This study evaluated correlation and agreement between version 3 of the Quantiplex human immunodeficiency virus type 1 (HIV-1) RNA assay (v3 branched DNA [bDNA]) and a sensitized Amplicor HIV-1 Monitor assay (reverse transcription [RT]-PCR) for the measurement of HIV RNA. Three hundred eighteen samples from 59 randomly selected, HIV-1-seropositive persons on various drug protocols from the National Institute of Allergy and Infectious Diseases HIV outpatient clinic were studied. The results indicate that v3 bDNA and RT-PCR are highly correlated (r = 0.98) and are in good agreement (mean difference in log(10) copies/ml +/- 2 standard deviations = 0.072 +/- 0.371). The relationship between values obtained by both assays is given by the following equation: log(10)v3 bDNA = -0.0915 + 1. 0052. log(10)RT-PCR. This represents a 1.026-fold difference between log(10)RT-PCR values and log(10)v3 bDNA values.

The effect of thalidomide on the pathogenesis of human immunodeficiency virus type 1 and M. tuberculosis infection.

Tumor necrosis factor alpha (TNF-alpha), a cytokine produced during the host defense against infection, is associated with fevers, weakness, and progressive weight loss. Thalidomide inhibits the synthesis of TNF-alpha both in vitro and in vivo and may have clinical usefulness. We therefore initiated a pilot study of thalidomide treatment in patients with human immunodeficiency virus type 1 (HIV-1)-associated wasting with or without concomitant infection with tuberculosis. Thirty-nine patients were randomly allocated to treatment with either thalidomide or placebo in a double-blind manner for 21 days. Thirty-two patients completed the study. In patients with concomitant HIV-1 and tuberculosis infections, thalidomide therapy was associated with a reduction in both plasma TNF-alpha levels and HIV-1 levels. No significant reduction in either TNF-alpha or HIV- 1 levels was observed in patients with HIV-1 infection only. During the study period, patients receiving thalidomide treatment (n=16) showed a significant weight gain (mean +/- SEM: 6.5 +/- 1.2%; p<0.02) relative to placebo-treated patients (n=16). Patients with simultaneous HIV-1 and tuberculosis infections experienced a higher mean weight gain during thalidomide treatment than the group of patients with HIV-1 infection only. The results of this pilot study suggest that thalidomide may have a clinical role in enhancing weight gain and possibly reducing TNF-alpha and HIV-1 levels in patients with HIV-1 and concomitant mycobacterial infections.

Passive hemagglutination test for detection of antibodies to human immunodeficiency virus type 1 and comparison of the test with enzyme-linked immunosorbent assay and Western blot (immunoblot) analysis.

A passive hemagglutination test (PHA) was developed for detecting antibodies to human immunodeficiency virus type 1 (HIV-1) utilizing sheep erythrocytes cross-linked with purified envelope glycoprotein (gp160) of HIV-1. In an analysis of 216 human serum samples, 100% correlation was observed in 86 reactive and 124 nonreactive serum samples between PHA and commercial enzyme-linked immunosorbent assays and Western blot (immunoblot) analysis. Serum samples from gp160-immunized chimpanzees also reacted equally well in PHA. The test is simple, rapid, and inexpensive, thus providing an alternate, quick method of detecting HIV antibodies. These advantages and the thermal stability of the reagents that are used make this an attractive alternative for detecting prior exposure of individuals to HIV-1.

Human immunodeficiency virus type 1 quasi species that rebound after discontinuation of highly active antiretroviral therapy are similar to the viral quasi species present before initiation of therapy.

In an effort to identify the sources of the viruses that emerge after discontinuation of therapy, analyses of human immunodeficiency virus (HIV) quasi species were done for 3 patients with sustained levels of HIV RNA of <50 copies/mL for 1-3 years. The sequences found in the rebounding plasma virus were closely related to those of the actively replicating form of viruses present before the initiation of combination therapy. All quasi species found in the rebounding plasma virus were also present in proviral DNA, cell-associated RNA in peripheral blood mononuclear cells (PBMC), and virion RNA derived from PBMC coculture during periods when plasma HIV RNA levels were <50 copies/mL. These findings suggest that the rapid resurgence of plasma viremia observed after discontinuation of therapy and the viruses cocultured from PBMC are derived from a relatively stable pool of the replicating form of virus rather than from activation of a previously latent pool.

Plasma viremia as a sensitive indicator of the antiretroviral activity of L-697,661.

L-697,661 is a non-nucleoside analogue with potent, selective inhibitory activity against the reverse transcriptase of human immunodeficiency virus type 1 (HIV-1). The present study evaluated the potential role of this compound in the treatment of HIV-1-infected patients in a double-blinded, placebo- and zidovudine-controlled trial using plasma viremia as a marker of antiviral activity and real-time phenotypic evaluation of viral isolates for the emergence of resistance. Participants received 12 weeks of either placebo, 25 mg twice a day, 100 mg three times a day, or 500 mg twice a day of L-697,661, or zidovudine, 100 mg five times a day. Mean logarithmic reciprocal titers of plasma virus in patients taking either L-697,661 or zidovudine decreased by week 4 of therapy; for L-697,661 recipients these changes were dose-dependent and, at the highest dose tested, were comparable in magnitude to those seen with zidovudine. Viral suppression induced by L-697,661 persisted through 8 weeks of treatment but decreased by week 12. This rebound paralleled emergence of viral isolates showing resistance to L-697,661. We conclude that although L-697,661 has potent antiretroviral activity in vivo, its utility may be compromised by rapid emergence of L-697,661-resistant virus. Plasma viremia is a highly sensitive technique affording considerable utility in the early testing of such agents.

Application of branched DNA signal amplification to monitor human immunodeficiency virus type 1 burden in human plasma.

A branched DNA (bDNA)-based quantitation of plasma human immunodeficiency virus type 1 (HIV-1) RNA was used to monitor the virologic status of 102 patients (29-906 CD4 cells/mm3) enrolled in clinical trials of antiretroviral and immune-based therapies. Virion-associated RNA was measurable in plasma of 74% of patients tested (10,000-10,000,000 RNA equivalents/mL). Virus levels measured by the bDNA assay exceeded titers obtained by quantitative plasma culture and were inversely correlated (r = -.378; P < .05) with total CD4 cell counts. The assay was used to demonstrate a significant decline (mean, 5-fold; range, 0- to 30-fold), relative to pretreatment, in virus load after beginning antiviral therapy and a transient increase (mean, 15-fold; range, 2- to 50-fold) after treatment with interleukin-2. The decrease in RNA was more dramatic than changes in serum p24 antigen. The bDNA assay yields reproducible results, is relatively easy, and should be useful in measuring HIV-1 RNA in patients in clinical trials.

Immunologic and virologic effects of subcutaneous interleukin 2 in combination with antiretroviral therapy: A randomized controlled trial.

CONTEXT: While interleukin 2 (IL-2) is capable of inducing a marked expansion of the CD4 T-lymphocyte pool, limited data exist on whether IL-2 treatment can add significantly to the immunologic and virologic effects of potent antiretroviral therapy (ART). OBJECTIVE: To determine the rate and magnitude of CD4 cell recovery and viral suppression when using a combination therapy of IL-2 and ART compared with ART alone. DESIGN AND SETTING: Randomized, controlled multicenter trial conducted from April 1996 through April 1998 at 8 clinical sites in the United States. PATIENTS: Eighty-two adult outpatients who were infected with human immunodeficiency virus (HIV) and had baseline CD4 cell counts of 200 x 10(6)/L to 500 x 10(6)/L and baseline RNA levels of fewer than 10,000 copies/mL were randomized; 78 completed the study. INTERVENTIONS: Thirty-nine patients were randomly assigned to receive a combination therapy of subcutaneous IL-2 (administered in 5-day courses every 8 weeks at a starting dosage of 7.5 mIU twice per day) and ART; 43 were to receive ART therapy alone. MAIN OUTCOME MEASURES: Interleukin 2 safety and differential effects on CD4 cell counts, CD4 cell percentages, and plasma HIV RNA levels. RESULTS: The mean (SD) percentage increase in CD4 cell counts at 1 year for patients who received IL-2 was 112% (113%) compared with 18% (35%) in recipients of ART alone (P<.001). Both groups had mean (SD) increases in CD4 cell percentage: from 20.4% (6.3%) to 32.3% (12.4%) for the combination therapy group compared with 20.4% (5.1%) to 23.0% (7.2%) for recipients of ART alone (P<.001). Using a sensitive viral RNA assay, mean viral load changes were -0.28 and 0.09 log(10) copies for IL-2 recipients and control patients, respectively (P=.03). Twenty (67%) of 30 evaluable patients receiving IL-2 achieved final viral loads of fewer than 50 copies/mL compared with 13 (36%) of 36 control patients (P=.02). Toxic effects were common among patients who received IL-2 and were managed with antipyretics, hydration, rest, and dosage reduction as needed. CONCLUSIONS: Intermittent therapy with IL-2 and ART produced a substantially greater increase in CD4 cells and was associated with a larger decrease in viral load than ART alone. Clinical end-point trials will be necessary to determine whether the enhanced viral suppression and CD4 cell increases associated with IL-2 therapy will translate into improved clinical outcomes. JAMA. 2000;284:183-189

Effects of intermittent interleukin-2 therapy on plasma and tissue human immunodeficiency virus levels and quasi-species expression.

To characterize the effects of intermittent interleukin (IL)-2 therapy on human immunodeficiency virus (HIV), 11 patients underwent detailed virological evaluation during a year of IL-2 therapy. Six patients showed a >0.5 log increase in plasma HIV during at least 1 IL-2 cycle, with 2 experiencing an increase in >50% of cycles. Three of the remaining 5 patients had a >0.5 log decrease during at least 1 IL-2 cycle, and the remaining patients exhibited <0.5 log changes. No changes in lymphoid (tonsil) levels of HIV were seen during the year. Quasi-species analysis in a separate cohort demonstrated that the virus induced by IL-2 most commonly resembled pre-IL-2 plasma quasi species. Thus, intermittent IL-2 does not result in sustained increases in either plasma or tissue levels of HIV and does not result in sustained expression of a previously silent quasi species.

Impact of HIV-1 infection and highly active antiretroviral therapy on the kinetics of CD4+ and CD8+ T cell turnover in HIV-infected patients.

To evaluate the effects of HIV infection on T cell turnover, we examined levels of DNA synthesis in lymph node and peripheral blood mononuclear cell subsets by using ex vivo labeling with BrdUrd. Compared with healthy controls (n = 67), HIV-infected patients (n = 57) had significant increases in the number and fraction of dividing CD4(+) and CD8(+) T cells. Higher percentages of dividing CD4(+) and CD8(+) T cells were noted in patients with the higher viral burdens. No direct correlation was noted between rates of T cell turnover and CD4(+) T cell counts. Marked reductions in CD4(+) and CD8(+) T cell proliferation were seen in 11/11 patients 1-12 weeks after initiation of highly active antiretroviral therapy (HAART). These reductions persisted for the length of the study (16-72 weeks). Decreases in naive T cell proliferation correlated with increases in the levels of T cell receptor rearrangement excision circles. Division of CD4(+) and CD8(+) T cells increased dramatically in association with rapid increases in HIV-1 viral loads in 9/9 patients 5 weeks after termination of HAART and declined to pre-HAART-termination levels 8 weeks after reinitiation of therapy. These data are consistent with the hypothesis that HIV-1 infection induces a viral burden-related, global activation of the immune system, leading to increases in lymphocyte proliferation.

Interleukin-2 induced immune effects in human immunodeficiency virus-infected patients receiving intermittent interleukin-2 immunotherapy.

To characterize the immunological effects of intermittent IL-2 therapy, which leads to selective increases in CD4+ T lymphocytes in HIV-infected patients, 11 patients underwent extensive immunological evaluation. While IL-2 induced changes in both CD4+ and CD8+ cell number acutely, only CD4+ cells showed sustained increases following discontinuation of IL-2. Transient increases in expression of the activation markers CD38 and HLA-DR were seen on both CD4+ and CD8+ cells, but CD25 (a chain of the IL-2 receptor) increased exclusively on CD4+ cells. This increase in CD25 expression was sustained for months following discontinuation of IL-2, and was seen in naive as well as memory cells. IL-2 induced cell proliferation, but tachyphylaxis to these proliferative effects developed after 1 week despite continued IL-2 administration. It thus appears that sustained CD25 expression selectively on CD4+ cells is a critical component of the immunological response to IL-2, and that intermittent administration of IL-2 is necessary to overcome the tachyphylaxis to IL-2-induced proliferation.

Short-cycle structured intermittent treatment of chronic HIV infection with highly active antiretroviral therapy: effects on virologic, immunologic, and toxicity parameters.

Although continuous highly active antiretroviral therapy (HAART) is effective for many HIV-infected patients, it can be toxic and prohibitive in cost. By decreasing the total amount of time patients receive medications, intermittent HAART could reduce toxicity and cost. Therefore, we initiated a pilot study in which 10 HIV-infected individuals receiving effective therapy that resulted in levels of HIV RNA <50 copies per ml of plasma and CD4(+) T cell counts >300 cells per mm(3) of whole blood received repeated cycles of 7 days on HAART followed by 7 days off of HAART. Patients maintained suppression of plasma viremia for 32-68 weeks. There was no significant increase in HIV proviral DNA or replication-competent HIV in peripheral CD4(+) T cells or HIV RNA in peripheral blood or lymph node mononuclear cells. There was no significant change in CD4(+) T cell counts, no significant increase in CD4(+) or CD8(+) T cells expressing activation markers or producing IFN-gamma in response to HIV, no increase in CD4(+) T cell proliferation to p24 antigen, and no evidence for the development of resistance to HAART medications. There was a significant decrease in serum cholesterol and triglyceride levels. Thus, in this proof-of-concept study, short-cycle intermittent HAART maintained suppression of plasma viremia as well as HIV replication in reservoir sites while preserving CD4(+) T cell counts. In addition, there was a decrease in serum cholesterol and triglyceride levels. Intermittent therapy may be an important strategy to reduce cost and toxicity for HIV-infected individuals.