Isolation of a TRAIL antagonist from the serum of HIV-infected patients.

Virus-host interactions are characterized by the selection of adaptive mechanisms by which to evade pathogenic and defense mechanisms, respectively. In primary T cells infected with HIV, HIV infection up-regulates TNF-related apoptosis inducing ligand (TRAIL) and death-inducing TRAIL receptors, but blockade of TRAIL:TRAIL receptor interaction does not alter HIV-induced cell death. Instead, HIV infection results in a novel splice variant that we call TRAIL-short (TRAIL-s), which antagonizes TRAIL-R2. In HIV patients, plasma TRAIL-s concentration increases with increasing viral load and renders cells resistant to TRAIL-induced death. Knockdown of TRAIL-s abrogates this resistance. We propose that TRAIL-s is a novel adaptive mechanism of apoptosis resistance acquired by HIV-infected cells to avoid their elimination by TRAIL-dependent effector mechanism.

Hold on to your memories: how recent findings will impact plant-based drug discovery.

It is accepted that genetic traits favoring the survival and reproduction of individual organisms are more successful and more likely to be passed on, and that this process of natural selection underlies the broader adaptations of species. However, the demonstration that an individual plant is able to impart 'untested' transgenerational changes to its offspring challenges this paradigm, and indicates an injection point for novelty into the overall adaptation process of plants. Understanding the basis of these newly discovered variations in metabolite expression will have broad implications for the field of ethnobotany. This discipline is predicated on knowledge garnered from generations of trial and error experimentation to identify medicinal properties in plants. Thus, the discovery of novel pathways to alter metabolite profiles in plant progeny also alter a fundamental assumption of the discipline: that plants with medicinal properties a thousand years ago will still have medicinal properties today.

A randomized Phase I study of Atuna racemosa: a potential new anti-MRSA natural product extract.

AIM: We previously reported significant antimicrobial activity against Gram-positive bacteria from the extract of the Atun tree (Atuna racemosa), identified through rapid digital bioprospecting of a 400-year-old historic herbal text. Toxicity studies in human cell lines showing safety, combined with the ethnomedical descriptions of botanical use, suggested that this extract might be clinically useful against topical Gram-positive bacteria infections. MATERIALS AND METHODS: Using a minimal inhibitory concentration assay, we examined the susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) to an extract of the kernel of the Atun tree (Atuna racemosa). Additionally, a maximum tolerated topical application of the extract was determined in a randomized, double-blind, placebo-controlled pilot clinical trial. RESULTS: Here we report that the effectiveness of this Atuna racemosa extract against MRSA (MIC=16-32microg/mL) is on par with currently available last-line antibiotics, while it remains well tolerated in short-term topical applications of 10 times the minimally inhibitory concentration. CONCLUSIONS: Although further studies are needed to determine safety and clinical efficacy, this effective extract, identified in a 400-year-old historic herbal text, may prove to be clinically useful in the treatment of MRSA.

Human immunodeficiency virus type 1 protease cleaves procaspase 8 in vivo.

Human immunodeficiency virus type 1 (HIV-1) infection causes apoptosis of infected CD4 T cells as well as uninfected (bystander) CD4 and CD8 T cells. It remains unknown what signals cause infected cells to die. We demonstrate that HIV-1 protease specifically cleaves procaspase 8 to create a novel fragment termed casp8p41, which independently induces apoptosis. casp8p41 is specific to HIV-1 protease-induced death but not other caspase 8-dependent death stimuli. In HIV-1-infected patients, casp8p41 is detected only in CD4(+) T cells, predominantly in the CD27(+) memory subset, its presence increases with increasing viral load, and it colocalizes with both infected and apoptotic cells. These data indicate that casp8p41 independently induces apoptosis and is a specific product of HIV-1 protease which may contribute to death of HIV-1-infected cells.

Glycoprotein 120 binding to CXCR4 causes p38-dependent primary T cell death that is facilitated by, but does not require cell-associated CD4.

HIV-1 infection causes the depletion of host CD4 T cells through direct and indirect (bystander) mechanisms. Although HIV Env has been implicated in apoptosis of uninfected CD4 T cells via gp120 binding to either CD4 and/or the chemokine receptor 4 (CXCR4), conflicting data exist concerning the molecular mechanisms involved. Using primary human CD4 T cells, we demonstrate that gp120 binding to CD4 T cells activates proapoptotic p38, but does not activate antiapoptotic Akt. Because ligation of the CD4 receptor alone or the CXCR4 receptor alone causes p38 activation and apoptosis, we used the soluble inhibitors, soluble CD4 (sCD4) or AMD3100, to delineate the role of CD4 and CXCR4 receptors, respectively, in gp120-induced p38 activation and death. sCD4 alone augments gp120-induced death, suggesting that CXCR4 signaling is principally responsible. Supporting that model, AMD3100 reduces death caused by gp120 or by gp120/sCD4. Finally, prevention of gp120-CXCR4 interaction with 12G5 Abs blocks p38 activation and apoptosis, whereas inhibition of CD4-gp120 interaction with Leu-3a has no effect. Consequently, we conclude that gp120 interaction with CXCR4 is required for gp120 apoptotic effects in primary human T cells.

Acquired T-cell sensitivity to TRAIL mediated killing during HIV infection is regulated by CXCR4-gp120 interactions.

BACKGROUND: Sensitivity towards apoptosis induced by ligation of the tumor necrosis factor family of death receptors is controlled in part by death receptor expression. Whereas cellular activation enhances Fas receptor expression and induces Fas sensitivity, such cellular activation neither alters TRAIL receptor expression nor induces TRAIL sensitivity. Cells infected by HIV acquire sensitivity to TRAIL induced death, although the mechanisms by which this is achieved are undefined. OBJECTIVE: To define the mechanism by which cells from HIV infected patients acquire sensitivity to TRAIL mediated killing. DESIGN: In vitro assessment of TRAIL receptor expression and TRAIL sensitivity. METHODS: Treatment of Jurkat T cells, peripheral blood lymphocytes from HIV negative donors, or human osteogenic seroma (HOS) cells expressing CD4, CXCR4 or CCR5 with T tropic gp120, M tropic gp120, or agonistic antibodies against CD4, CXCR4 or CCR5. TRAIL receptors were measured by flow cytometry or reverse transcription-PCR and TRAIL sensitivity was assessed by incubation with recombinant TRAIL followed by Annexin V fluorescein isothiocyanate/Propidium Iodide (PI) staining. RESULTS: Treatment of uninfected Jurkat T cells, as well as primary T cells with gp120 results in the upregulation of TRAIL death receptor expression and acquired sensitivity to TRAIL mediated cell death. The increase in TRAIL death receptor expression and acquisition of TRAIL sensitivity requires the chemokine coreceptor CXCR4 but not CCR5 or the CD4 receptor. CONCLUSIONS: These results indicate that chemokine receptor interactions regulate TRAIL receptor expression and provide an explanation for the acquired T cell sensitivity to TRAIL mediated killing death during HIV infection.

Techniques: Bioprospecting historical herbal texts by hunting for new leads in old tomes.

Ethnobotany has led to the identification of novel pharmacological agents but many challenges to using ethnobotany as a research tool remain. In particular, the loss of traditional knowledge together with the advent of high-throughput screening has made ethnobotanical techniques laborious and potentially unnecessary. However, historical herbal texts provide a preexisting resource that documents the traditional uses of various species as medicines. As generational losses of traditional knowledge accrue, these herbal texts become increasingly valuable. The methodology for extracting useful information contained within these resources had been cumbersome and consuming. However, the application of new bioinformatics data-mining systems to herbal texts holds great promise for identifying novel pharmacotherapeutic leads for bioactive compounds.

Differential effects of interleukin-7 and interleukin-15 on NK cell anti-human immunodeficiency virus activity.

The ability of interleukin-7 (IL-7) and IL-15 to expand and/or augment effector cell functions may be of therapeutic benefit to human immunodeficiency virus (HIV)-infected patients. The functional effects of these cytokines on innate HIV-specific immunity and their impact on cells harboring HIV are unknown. We demonstrate that both IL-7 and IL-15 augment natural killer (NK) function by using cells (CD3(-) CD16(+) CD56(+)) from both HIV-positive and -negative donors. Whereas IL-7 enhances NK function through upregulation of Fas ligand, the effect of IL-15 is mediated through upregulation of tumor necrosis factor-related apoptosis-inducing ligand. The difference in these effector mechanisms is reflected by the ability of IL-15-treated but not IL-7-treated NK cells to reduce the burden of replication-competent HIV in autologous peripheral blood mononuclear cells (PBMC) (infectious units per million for control NK cells, 6.79; for IL-7-treated NK cells, 236.17; for IL-15-treated cells, 1.01; P = 0.01 versus control). In addition, the treatment of PBMC with IL-15-treated but not IL-7-treated NK cells causes undetectable HIV p24 (five of five cases), HIV RNA (five of five cases), or HIV DNA (three of five cases). These results support the concept of adjuvant immunotherapy of HIV infection with either IL-7 or IL-15 but suggest that the NK-mediated antiviral effect of IL-15 may be superior.