Dumith Chequer Bou-Habib

Antileishmanial Activity of an Indole Alkaloid from Peschiera australis

ABSTRACT In this study, we show the leishmanicidal effects of a chloroform fraction (CLF) and a purified indole alkaloid obtained from crude stem extract of Peschiera australis againstLeishmania amazonensis, a causative agent of cutaneous leishmaniasis in the New World. In a bioassay-guided chemical fractionation, the leishmanicidal activity in CLF completely and irreversibly inhibited promastigote growth. This fraction was also active against amastigotes in infected murine macrophages. Chemical analysis of CLF identified an iboga-type indole alkaloid coronaridine as one of its major compounds. Coronaridine showed potent antileishmanial activity, inhibiting promastigote and amastigote growth. Promastigotes and amastigotes treated with CLF or coronaridine showed pronounced alterations in their mitochondria as assessed by transmission electron microscopy.

Increased Leishmania Replication in HIV-1–Infected Macrophages Is Mediated by Tat Protein through Cyclooxygenase-2 Expression and Prostaglandin E2 Synthesis

Protozoan parasites of the genus Leishmania frequently occur as opportunistic pathogens in human immunodeficiency virus type 1 (HIV-1)-infected individuals, but the mechanisms underlying protozoan growth in this context are poorly understood. Here, we demonstrate that the HIV-1 Tat protein drives Leishmania replication in primary human macrophages. We found that Leishmania growth doubled in HIV-1-infected macrophages and that anti-Tat antibodies reduced the exacerbated protozoan replication by 70%. Recombinant Tat increased Leishmania replication and overrode the leishmanicidal effect induced by interferon-gamma , allowing Leishmania replication even in the presence of this cytokine. Tat induced cyclooxygenase (COX)-2 expression and prostaglandin E2 (PGE2) synthesis, and a COX-2 inhibitor abolished the Tat-mediated augmentation of Leishmania replication. Moreover, PGE2 increased Leishmania growth, which was abrogated by anti-transforming growth factor (TGF)- beta1 monoclonal antibodies. Neutralization of TGF-beta1 reduced parasite growth in Leishmania-infected macrophages exposed to Tat by 50%. Our findings suggest that Tat generates a milieu permissive to Leishmania growth in individuals infected with HIV-1.

The replication of human immunodeficiency virus type 1 in macrophages is enhanced after phagocytosis of apoptotic cells.

Clearance of apoptotic cells increases macrophage secretion of antiinflammatory mediators and might modulate viral replication in human immunodeficiency virus (HIV) type 1-infected macrophages. To study this, primary macrophages were infected with HIV-1 and exposed to apoptotic cells. It was found that phagocytosis of apoptotic cells potently enhanced HIV-1 growth. The peptide Arg-Gly-Asp-Ser, which binds to integrin receptors, inhibited the uptake of apoptotic cells and the subsequent enhancement of HIV-1 replication. Viral replication was preceded by increased secretion of transforming growth factor (TGF)-beta1 and partially reverted by anti-TGF-beta1 antibodies. Moreover, anti-TGF-beta1 antibodies inhibited HIV-1 replication in macrophages not exposed to apoptotic cells. A positive correlation was observed between TGF-beta1 production and HIV-1 growth, and the addition of TGF-beta1 amplified HIV-1 replication in macrophages from low TGF-beta1 producers. The findings suggest that TGF-beta1 favors HIV-1 replication in macrophages and that the clearance of apoptotic cells by HIV-1-infected macrophages contributes to persistent viremia in patients infected with HIV-1.

Novel role for the double-stranded RNA-activated protein kinase PKR: modulation of macrophage infection by the protozoan parasite Leishmania.

The evolution of Leishmania infection depends on the balance between microbicidal and suppressor macrophage functions. Double‐stranded RNA (dsRNA)‐activated protein kinase R (PKR), a classic antiviral protein, is able to regulate a number of signaling pathways and macrophage functions. We investigated the possible role of PKR in the modulation of Leishmania infection. Our data demonstrated that Leishmania amazonensis infection led to PKR activation and increased PKR levels. Consistently, in macrophages from PKR knockout 129Sv/Ev mice and RAW‐264.7 cells stably expressing a dominant‐negative (DN) construct of PKR (DN‐PKR), L. amazonensis infection was strongly reduced. The treatment of infected macrophages with the synthetic double‐stranded RNA poly(I:C), a potent PKR inductor, increased L. amazonensis intracellular proliferation. This effect was reversed by 2‐aminopurine (2‐AP), a pharmacological inhibitor of PKR, as well as by the expression of DN‐PKR. NO release induced by dsRNA treatment was inhibited by L. amazonensis through NF‐κB modulation. PKR activation induced by dsRNA also resulted in IL‐10 production, whose neutralization with specific antibody completely abrogated L. amazonensis proliferation. Our data demonstrated a new role of PKR in protozoan parasitic infection through IL‐10 modulation.—Pereira, R. M. S., Teixeira, K. L. D., Barreto‐de‐Souza, V. Calegari‐Silva, T. C., De‐Melo, D. B., Soares, D. C., Bou‐Habib, D. C., Silva, A. M., Saraiva, E. M., Lopes, U. G. Novel role for the double‐stranded RNA‐activated protein kinase PKR: modulation of macrophage infection by the protozoan parasite Leishmania. FASEB J. 24, 617–626 (2010). www.fasebj.org

Elevated levels of Macrophage Migration Inhibitory Factor (MIF) in the plasma of HIV-1-infected patients and in HIV-1-infected cell cultures: a relevant role on viral replication

The cytokine macrophage migration inhibitory factor (MIF) is involved in the pathogenesis of inflammatory and infectious diseases, however its role in HIV-1 infection is unknown. Here we show that HIV-1-infected patients present elevated plasma levels of MIF, that HIV-1-infected peripheral blood mononuclear cells (PBMCs) release a greater amount of MIF, and that the HIV-1 envelope glycoprotein gp120 induces MIF secretion from uninfected PBMCs. The HIV-1 replication in PBMCs declines when these cells are treated with anti-MIF antibodies, and exposure of HIV-1-infected cells to the ABC-transporter inhibitor probenecid results in inhibition of MIF secretion. The addition of recombinant MIF (rhMIF) to HIV-1-infected PBMCs enhances viral replication of CCR5- or CXCR4-tropic HIV-1 isolates. Using a T CD4(+) cell lineage containing an HIV long terminal repeats (LTR)-Luciferase construct, we detected that rhMIF promotes transcription from HIV-1 LTR. Our results show that HIV-1 induces MIF secretion and suggest that MIF influences the HIV-1 biology through activation of HIV-1 LTR.

Prevalence of the CCR5Δ32 mutation in Brazilian populations and cell susceptibility to HIV-1 infection

Abstract. We investigated the occurrence of the CCR5Δ32 mutation in various regional ethnic groups in Brazil and tested the resistance of mutant peripheral blood mononuclear cells (PBMCs) to infection by HIV-1 in vitro. The heterozygous prevalence was 5.3% in uninfected African descendents and 8.8% in HIV-1-positive individuals (neither population had Δ32/Δ32). German descendents were 11% heterozygous and l% Δ32/Δ32. Amerindians were exclusively CCR5/CCR5. Heterozygous uninfected PBMCs showed partial resistance to R5-HIV-1 strains in vitro, but no resistance to X4 virus. HIV-1-positive CCR5/CCR5 had higher viral loads than did heterozygous cells.

Dolabelladienetriol, a compound from Dictyota pfaffii algae, inhibits the infection by Leishmania amazonensis

Background Chemotherapy for leishmaniasis, a disease caused by Leishmania parasites, is expensive and causes side effects. Furthermore, parasite resistance constitutes an increasing problem, and new drugs against this disease are needed. In this study, we examine the effect of the compound 8,10,18-trihydroxy-2,6-dolabelladiene (Dolabelladienetriol), on Leishmania growth in macrophages. The ability of this compound to modulate macrophage function is also described. Methodology/Principal Findings Leishmania-infected macrophages were treated with Dolabelladienetriol, and parasite growth was measured using an infectivity index. Nitric oxide (NO), TNF-α and TGF-β production were assayed in macrophages using specific assays. NF-kB nuclear translocation was analyzed by western blot. Dolabelladienetriol inhibited Leishmania in a dose-dependent manner; the IC50 was 44 µM. Dolabelladienetriol diminished NO, TNF-α and TGF-β production in uninfected and Leishmania-infected macrophages and reduced NF-kB nuclear translocation. Dolabelladienetriol inhibited Leishmania infection even when the parasite growth was exacerbated by either IL-10 or TGF-β. In addition, Dolabelladienetriol inhibited Leishmania growth in HIV-1-co-infected human macrophages. Conclusion Our results indicate that Dolabelladienetriol significantly inhibits Leishmania in macrophages even in the presence of factors that exacerbate parasite growth, such as IL-10, TGF-β and HIV-1 co-infection. Our results suggest that Dolabelladienetriol is a promising candidate for future studies regarding treatment of leishmaniasis, associated or not with HIV-1 infection.

HIV-1 infection and HIV-1 Tat protein permit the survival and replication of a non-pathogenic trypanosomatid in macrophages through TGF-β1 production

Monoxenic trypanosomatids, which usually are non-pathogenic in humans, have been detected in AIDS patients, but the mechanisms underlying the establishment of these protozoa in HIV-1-infected individuals are poorly understood. Here we addressed the role of HIV-1 and the HIV-1 Tat protein in the replication of the monoxenic trypanosomatid Blastocrithidia culicis in HIV-1-infected primary human macrophages. We found that HIV-1 and B. culicis replication augmented almost three times in co-infected macrophages, and that Tat antiserum significantly reduced the exacerbated protozoan growth. Exposure of B. culicis only infected macrophages to Tat protein also resulted in enhanced protozoan proliferation, reaching a twofold increase at 100 ng/mL. Electron microscopy analysis revealed that B. culicis and HIV-1 co-habit the same cells, and showed protozoan dividing forms inside macrophages. Protozoan replication diminished when B. culicis only infected macrophages were treated with Tat protein in the presence of anti-TGF-beta1 antibodies, suggesting a participation of this cytokine in the augmentation of protozoan multiplication. In fact, exogenous TGF-beta1 promoted the trypanosomatid replication in macrophages. Overall, our results suggest that HIV-1 infection deactivates the macrophage microbicidal activity, permitting the survival and multiplication of an otherwise non-pathogenic protozoan in these cells, a process partially mediated by Tat protein, via TGF-beta1 secretion.

Activation of Toll-like receptor 2 increases macrophage resistance to HIV-1 infection

Patients infected with HIV-1, the etiological agent of AIDS, have increased intestinal permeability, which allows for the passage of microbial products, including Toll-like receptor (TLR) ligands, into circulation. The exposure of HIV-1-infected cells to certain TLR agonists affects viral replication, but studies associating viral production with the activation of TLR2 in HIV-1-infected cells are rare and controversial. Here, we report that the TLR2 ligands Zymosan and Pam3CSK4 potently inhibit HIV-1 replication in acutely infected monocyte-derived macrophages and the exposure to TLR2 ligands prior to infection renders macrophages refractory to HIV-1 production. Macrophage treatment with Pam3CSK4 did not change the cellular expression of the HIV-1 entry receptors CD4 and CCR5. Both TLR2 ligands increased the macrophage production of β-chemokines and IL-10, and the blockage of these soluble factors prevented the inhibitory effect of TLR2 activation on HIV-1 replication. Our findings show that the direct engagement of TLR2 in HIV-1-infected macrophages increase cellular resistance to HIV-1 infection, and that controlling HIV-1 replication with agonists for TLR2 might have implications for the development of antiretroviral therapies.

The nerve growth factor reduces APOBEC3G synthesis and enhances HIV-1 transcription and replication in human primary macrophages

Macrophages infected with HIV-1 sustain viral replication for long periods of time, functioning as viral reservoirs. Therefore, recognition of factors that maintain macrophage survival and influence HIV-1 replication is critical to understanding the mechanisms that regulate the HIV-1-replicative cycle. Because HIV-1-infected macrophages release the nerve growth factor (NGF), and NGF neutralization reduces viral production, we further analyzed how this molecule affects HIV-1 replication. In the present study, we show that NGF stimulates HIV-1 replication in primary macrophages by signaling through its high-affinity receptor Tropomyosin-related Kinase A (TrKA), and with the involvement of reticular calcium, protein kinase C, extracellular signal-regulated kinase, p38 kinase, and nuclear factor-κB. NGF-induced enhancement of HIV-1 replication occurred during the late events of the HIV-1-replicative cycle, with a concomitant increase in viral transcription and production. In addition, NGF reduced the synthesis of the cellular HIV-1 restriction factor APOBEC3G and also overrode its interferon-γ-induced up-regulation, allowing the production of a well-fitted virus. Because NGF-TrKA signaling is a crucial event for macrophage survival, it is possible that NGF-induced HIV-1 replication plays a role in the maintenance of HIV-1 reservoirs. Our study may contribute to the understanding of the immunopathogenesis of HIV-1 infection and provide insights about approaches aimed at limiting viral replication in HIV-1 reservoirs.