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Biomedical subjects

Joseph M McCune

Publications and source records attributed to Joseph M McCune.

31 records · Page 2Linked to original sources
PubMed2004

Strong cell-mediated immune responses are associated with the maintenance of low-level viremia in antiretroviral-treated individuals with drug-resistant human immunodeficiency virus type 1.

Antiretroviral (ARV)-treated patients often maintain low to moderate levels of viremia, despite the emergence of drug-resistant human immunodeficiency virus (HIV). We studied host and viral factors that may contribute to the control of viral replication in a cohort of 189 adults. Among ARV-treated patients with detectable viremia, there was a bell-shaped relationship between Gag-specific CD4+ T cell responses and viremia, with the highest cellular immune responses observed in patients with plasma HIV RNA levels of 1000-10,000 copies/mL. In contrast, there was a negative association between Gag-specific CD4+ T cell responses and viremia among ARV-untreated individuals with wild-type HIV. Strong cellular immune responses among individuals with drug-resistant HIV predicted subsequent lack of virological progression. Finally, there was a positive correlation between replicative capacity and viremia. Collectively, these data suggest that the selection of drug-resistance mutations may reduce the pathogenic potential of HIV, which leads to a balanced state of enhanced cellular immunity and low-level viremia.

Acquired Immunodeficiency Syndrome↗
PubMed2004

Isolation of peripheral blood CD4(+) T cells using RosetteSep and MACS for studies of DNA turnover by deuterium labeling.

Tracking deuterium ((2)H) incorporation into cellular DNA, after administration of (2)H(2)O or (2)H(2)-glucose, is a recently developed, broadly applicable method for measuring in vivo cell proliferation and turnover that can be used safely in humans. This approach has been used to evaluate the turnover of T-cell subpopulations purified from the peripheral blood of HIV-1-infected patients using fluorescence-activated cell sorting (FACS). A requirement for widespread adoption of this approach for medical decision-making and for use in larger clinical trials is a simple, reproducible, high-throughput method for isolation of highly purified CD4(+) T cells from peripheral blood. Here, we present a simple method, which does not require FACS, for isolating these cells in sufficient purity and yield for analysis of (2)H incorporation into DNA. When blood from HIV-1-infected patients was used, neither the depletion of unwanted cell lineages by erythrocyte crosslinking (RosetteSep) nor the enrichment of CD4(+) cells by immunomagnetic beads (MACS) individually resulted in sufficient purity. The successive application of the two techniques, however, permitted isolation of >95% pure CD4(+) T cells in adequate yield (>10(6) cells/10 ml blood) from healthy donors and HIV-1-infected patients with CD4 counts between 300 and 700 cells/microl. Moreover, (2)H incorporation into cellular DNA after administration of (2)H(2)O to HIV-1-infected patients was indistinguishable between CD4(+) T cells isolated by RosetteSep/MACS and FACS. Thus, both FACS and the new method isolate a similar mixture of long- and short-lived CD4(+) T cells. In practice, the RosetteSep/MACS method is simple, rapid, robust and capable of high throughput.

Administration, Oral↗
PubMed2003

Short-term effects of cannabinoids in patients with HIV-1 infection: a randomized, placebo-controlled clinical trial.

BACKGROUND: Cannabinoid use could potentially alter HIV RNA levels by two mechanisms: immune modulation or cannabinoid-protease inhibitor interactions (because both share cytochrome P-450 metabolic pathways). OBJECTIVE: To determine the short-term effects of smoked marijuana on the viral load in HIV-infected patients. DESIGN: Randomized, placebo-controlled, 21-day intervention trial. SETTING: The inpatient General Clinical Research Center at the San Francisco General Hospital, San Francisco, California. PARTICIPANTS: 67 patients with HIV-1 infection. INTERVENTION: Participants were randomly assigned to a 3.95%-tetrahydrocannabinol marijuana cigarette, a 2.5-mg dronabinol (delta-9-tetrahydrocannabinol) capsule, or a placebo capsule three times daily before meals. MEASUREMENTS: HIV RNA levels, CD4+ and CD8+ cell subsets, and pharmacokinetic analyses of the protease inhibitors. RESULTS: 62 study participants were eligible for the primary end point (marijuana group, 20 patients; dronabinol group, 22 patients; and placebo group, 20 patients). Baseline HIV RNA level was less than 50 copies/mL for 36 participants (58%), and the median CD4+ cell count was 340 x 109 cells/L. When adjusted for baseline variables, the estimated average effect versus placebo on change in log10 viral load from baseline to day 21 was -0.07 (95% CI, -0.30 to 0.13) for marijuana and -0.04 (CI, -0.20 to 0.14) for dronabinol. The adjusted average changes in viral load in marijuana and dronabinol relative to placebo were -15% (CI, -50% to 34%) and -8% (CI, -37% to 37%), respectively. Neither CD4+ nor CD8+ cell counts appeared to be adversely affected by the cannabinoids. CONCLUSIONS: Smoked and oral cannabinoids did not seem to be unsafe in people with HIV infection with respect to HIV RNA levels, CD4+ and CD8+ cell counts, or protease inhibitor levels over a 21-day treatment.

Administration, Oral↗
PubMed2003

Effects of IL-7 on early human thymocyte progenitor cells in vitro and in SCID-hu Thy/Liv mice.

IL-7 is a critical component of thymopoiesis in animals and has recently been shown to play an important role in T cell homeostasis. Although there is increasing interest in the use of IL-7 for the treatment of lymphopenia caused by the HIV type 1, evidence that IL-7 may accelerate HIV replication has raised concerns regarding its use in this setting. We sought to identify the effects of IL-7 on human thymocyte survival and to determine the impact of IL-7 administration on in vivo HIV infection of the human thymus. Using in vitro analysis, we show that IL-7 provides potent anti-apoptotic and proliferative signals to early thymocyte progenitors. Analysis of CD34(+) subpopulations demonstrates that surface IL-7 receptor is expressed on most CD34(high)CD5(+)CD1a(-) thymocytes and that this subpopulation appears to be one of the earliest maturation stages responsive to the effects of IL-7. Thus, IL-7 provides survival signals to human thymocytes before surface expression of CD1a. CD4(+)CD8(+) thymocytes are relatively unresponsive to IL-7, although IL-7 protects these cells from dexamethasone-induced apoptosis. IL-7 has a predominantly proliferative effect on mature CD4(+)CD3(+)CD8(-) and CD8(+)CD3(+)CD4(-) thymocytes. In contrast to the in vitro findings, we observe that in vivo administration of IL-7 to SCID-hu Thy/Liv mice does not appear to enhance thymocyte survival nor does it appear to accelerate HIV infection. Given the growing interest in the use of IL-7 for the treatment of human immunodeficiency, these findings support additional investigation into its in vivo effects on thymopoiesis and HIV infection.

Animals↗
PubMed2003

Comparison of the ELISPOT and cytokine flow cytometry assays for the enumeration of antigen-specific T cells.

The enumeration of antigen-specific T cell responses has been greatly facilitated in recent years by the development of methods based on the detection of cytokines. In particular, the enzyme-linked immunospot (ELISPOT) and cytokine flow cytometry (CFC) assays have become popular. Since both assays are likely to continue to be in widespread use, it is important to evaluate whether their results are comparable. In the current study, we compared the results obtained in the ELISPOT and CFC assays using peptide pools corresponding to CMV and HIV-1 proteins in chronically HIV-1-infected individuals. Analysis of T cell responses to peptide pools indicated that the CMV pp65 and HIV-1 Gag CFC and ELISPOT-derived results were statistically correlated. However, the results obtained with each assay differed in important ways: the magnitude of the response was consistently higher in the CFC assay while the CFC assay was less likely than the ELISPOT assay to detect low-level responses. Furthermore, there was a lack of numeric agreement between ELISPOT and CFC results. For studies that require the detection of low-level responses, or definition of responses as positive or negative, the ELISPOT assay may be preferable. In contrast, the CFC has a greater dynamic range and allows for phenotypic discrimination of responding cells, making it the assay of choice for most other applications.

CD4 Lymphocyte Count↗
PubMed2003

Human immunodeficiency virus type 1 Nef-mediated downregulation of CD4 correlates with Nef enhancement of viral pathogenesis.

The nef gene products encoded by human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus type 1 (SIV-1) increase viral loads in infected hosts and accelerate clinical progression to AIDS. Nef exhibits a spectrum of biological activities, including the ability to downregulate surface expression of CD4 and major histocompatibility complex (MHC) class I antigens, to alter the state of T-cell activation, and to enhance the infectivity of viral particles. To determine which of these in vitro functions most closely correlates with the pathogenic effects of Nef in vivo, we constructed recombinant HIV-1 NL4-3 viruses carrying mutations within the nef gene that selectively impair these functions. These mutant viruses were evaluated for pathogenic potential in severe combined immunodeficiency (SCID) mice implanted with human fetal thymus and liver (SCID-hu Thy/Liv mice), in which virus-mediated depletion of thymocytes is known to be Nef dependent. Disruption of the polyproline type II helix (Pxx)4 within Nef (required for binding of Hck and p21-activated kinase-like kinases, downregulation of MHC class I, and enhancement of HIV-1 infectivity in vitro but dispensable for CD4 downregulation) did not impair thymocyte depletion in virus-infected Thy/Liv human thymus implants. Conversely, three separate point mutations in Nef that compromised its ability to downregulate CD4 attenuated thymocyte depletion while not diminishing viral replication. These findings indicate that the functional ability of Nef to downregulate CD4 and not MHC class I downregulation, Hck or PAK binding, or (Pxx)4-associated enhancement of infectivity most closely correlates with Nef-mediated enhancement of HIV-1 pathogenicity in vivo. Nef-mediated CD4 downregulation merits consideration as a new target for the development of small-molecule inhibitors.

Alleles↗
PubMed2003

Subpopulations of long-lived and short-lived T cells in advanced HIV-1 infection.

Antigenic stimulation of T cells gives rise to short-lived effector cells and long-lived memory cells. We used two stable isotope-labeling techniques to identify kinetically distinct subpopulations of T cells and to determine the effect of advanced infection with HIV-1. Long-term deuterated water (2H2O) incorporation into DNA demonstrated biphasic accrual of total and of memory/effector (m/e)-phenotype but not naive-phenotype T cells, consistent with the presence of short-lived and longer-lived subpopulations within the m/e-phenotype T cell pool. These results were mirrored by biphasic die-away kinetics in m/e- but not naive-phenotype T cells after short-term 2H-glucose labeling. Persistent label retention was observed in a subset of m/e-phenotype T cells (presumably memory T cells), confirming the presence of T cells with very different life spans in humans. In advanced HIV-1 infection, much higher proportions of T cells were short-lived, compared to healthy controls. Effective long-term anti-retroviral therapy restored values to normal. These results provide the first quantitative evidence that long-lived and quiescent T cells do indeed predominate in the T cell pool in humans and determine T cell pool size, as in rodents. The greatest impact of advanced HIV-1 infection is to reduce the generation of long-lived, potential progenitor T cells.

Anti-HIV Agents↗
PubMed2002

Generation of CD3+CD8low thymocytes in the HIV type 1-infected thymus.

Infection with the HIV type 1 (HIV-1) can result both in depletion of CD4(+) T cells and in the generation of dysfunctional CD8(+) T cells. In HIV-1-infected children, repopulation of the peripheral T cell pool is mediated by the thymus, which is itself susceptible to HIV-1 infection. Previous work has shown that MHC class I (MHC I) molecules are strongly up-regulated as result of IFN-alpha secretion in the HIV-1-infected thymus. We demonstrate in this study that increased MHC I up-regulation on thymic epithelial cells and double-positive CD3(-/int)CD4(+)CD8(+) thymocytes correlates with the generation of mature single-positive CD4(-)CD8(+) thymocytes that have low expression of CD8. Treatment of HIV-1-infected thymus with highly active antiretroviral therapy normalizes MHC I expression and surface CD8 expression on such CD4(-)CD8(+) thymocytes. In pediatric patients with possible HIV-1 infection of the thymus, a low CD3 percentage in the peripheral circulation is also associated with a CD8(low) phenotype on circulating CD3(+)CD8(+) T cells. Furthermore, CD8(low) peripheral T cells from these HIV-1(+) pediatric patients are less responsive to stimulation by Ags from CMV. These data indicate that IFN-alpha-mediated MHC I up-regulation on thymic epithelial cells may lead to high avidity interactions with developing double-positive thymocytes and drive the selection of dysfunctional CD3(+)CD8(low) T cells. We suggest that this HIV-1-initiated selection process may contribute to the generation of dysfunctional CD8(+) T cells in HIV-1-infected patients.

CD3 Complex↗
PubMed2002

Increased thymic mass and circulating naive CD4 T cells in HIV-1-infected adults treated with growth hormone.

OBJECTIVE: To determine whether treatment with growth hormone (GH) enhances thymopoiesis in individuals infected with HIV-1. METHODS: Five HIV-1-infected adults were treated with GH for 6-12 months in a prospective open-label study. Immunological analyses were performed before GH treatment and repeated at 3 month intervals after GH initiation. Thymic mass was analysed using computed tomography with quantitative density and volume analysis. Analysis of circulating lymphocytes, including naive and memory T cell subsets, was performed using multiparameter flow cytometry. RESULTS: GH treatment was associated with a marked increase in thymic mass in all GH recipients. Circulating naive CD4 T cells also increased significantly in all patients during GH therapy, suggesting an enhancement of thymopoiesis. CONCLUSION: GH has significant effects on the human immune system, including the reversal of thymic atrophy in HIV-1-infected adults. De-novo T cell production may thus be inducible in immunodeficient adults.

Adult↗
PubMed2002

CD4+ T cell kinetics and activation in human immunodeficiency virus-infected patients who remain viremic despite long-term treatment with protease inhibitor-based therapy.

T cell dynamics were studied in human immunodeficiency virus-infected patients who continued using antiretroviral therapy despite detectable plasma viremia (RNA copies >2500 /mL). CD4(+) cell fractional replacement rates, measured by the deuterated glucose technique, were lower in treated patients with detectable viremia than in untreated patients and were similar to those in patients with undetectable viremia. Cell cycle and activation markers exhibited similar trends. For any level of viremia, CD4(+) cell fractional replacement rates were lower in patients with drug-resistant virus than in patients with wild-type virus, which suggests that the resistant variant was less virulent. Interruption of treatment in patients with drug-resistant viremia resulted in increased CD4(+) cell activation, increased CD4(+) cell turnover, and decreased CD4(+) cell counts. These data indicate that partial virus suppression reduces CD4(+) cell turnover and activation, thereby resulting in sustained CD4(+) cell gains, and that measurements of T cell dynamics may provide an in vivo marker of viral virulence.

Adult↗
PubMed2002

IFN-alpha secretion by type 2 predendritic cells up-regulates MHC class I in the HIV-1-infected thymus.

The ability of HIV-1 to evade the host immune response leads to the establishment of chronic infection. HIV-1 has been reported to up-regulate MHC I molecules on the surface of thymocytes from HIV-1-infected thymus. We demonstrate in this study that HIV-1 up-regulates MHC I on both HIV-1-infected and uninfected thymocytes in a manner that is independent of Nef, proportional to viral replication, and entirely mediated by IFN-alpha. IL-3Ralpha+ type 2 predendritic cells (preDC2) resident in the thymic medulla secrete IFN-alpha, which acts on IFN-alphabetaR-expressing immature thymocytes to induce MHC I expression. Furthermore, thymic preDC2 are permissive for HIV-1 infection and positive for intracellular p24. These data demonstrate the ability of IFN-alpha secreted by preDC2 to induce MHC I up-regulation in the HIV-1-infected human thymus.

Animals↗
PubMed2002

Short-term effects of cannabinoids on immune phenotype and function in HIV-1-infected patients.

Cannabinoids, including smoked marijuana and delta9-tetrahydrocannabinol (THC) (dronabinol, Marinol), have been used to treat human immunodeficiency virus-1 (HIV)-associated anorexia and weight loss. Concerns have been raised, however, that these compounds might have adverse effects on the immune system of subjects with HIV infection. To determine whether such effects occur, the authors designed a randomized, prospective, controlled trial comparing the use of marijuana cigarettes (3.95% THC), dronabinol (2.5 mg), and oral placebo in HIV-infected adults taking protease inhibitor-containing highly active antiretroviral therapy (HAART). Assays of immune phenotype (including flow cytometric quantitation of T cell subpopulations, B cells, and natural killer [NK] cells) and immunefunction (including assays for induced cytokine production, NK cell function, and lymphoproliferation) were performed at baseline and weekly thereafter. On the basis of these measurements and during this short 21-day study period, few statistically significant effects were noted on immune system phenotypes orfunctions in this patient population.

Acquired Immunodeficiency Syndrome↗