Prostratin Hiv Activation

Sigma-Aldrich offers abstracts and full-text articles by Joaquín Rullas, Mercedes Bermejo, Javier García-Pérez, Manuela Beltán, Nuria González, Marjan Hezareh.

IMMUNOBIOLOGY Prostratin: activation of latent HIV-1 expression suggests a potential inductive adjuvant therapy for HAART Joseph Kulkosky, Derek M. Culnan.

HIV-1 infection can be treated effectively in many patients in the developed world, using combinations of antiretroviral therapeutics, called Highly Active Anti-Retroviral Therapy HAART. However, despite prolonged treatment with HAART, the persistence of HIV-1 reservoirs harboring transcriptionally silent but replication-competent proviruses represents the major hurdle to virus eradication. These latently-infected cells are a permanent source for virus reactivation and lead to a rebound of the viral load after interruption of HAART. Therefore, current anti-HIV-1 research efforts are increasingly focused on strategies aimed at reducing the size of these persistent reservoirs of latent HIV-1 by forcing viral gene expression. This kind of strategy would allow latently-infected cells to die from viral cytopathic effects or host cytolytic effector mechanisms following viral reactivation, while the antiretroviral therapy would prevent spreading of the infection by the neosynthetized virus 1, 2.

Acetylation level of histone and non-histone proteins, controlled by deacetylases HDACs and acetyltransferases HATs, is a key element regulating HIV-1 transcription. In agreement, we have previously reported that treatment of latently HIV-1-infected cell lines with HDAC inhibitors HDACIs induces viral transcription and remodeling of the repressive nucleosome nuc-1, located immediately after the HIV-1 transcription start site under latency conditions 3, 4. Similar results were observed in transiently or stably transfected HIV-1 Long Terminal Repeat LTR reporter constructs 5, 6, 7, and on in vitro chromatin-reconstituted HIV-1 templates 8, 9. Based on these observations, administration of HDACIs together with efficient HAART has been proposed as an inductive adjuvant therapy for the decay of latent reservoirs 10, 11, 12, 13. The Margolis group has reported that VPA valproic acid, in the presence of IL-2, induces rescue of replication-competent HIV-1 from purified resting CD4 T cells obtained from HAART-treated patients with undetectable viral load 14. Later, in a clinical trial performed by same group, four patients receiving HAART and the viral entry inhibitor enfuvirtide were given VPA for three months, and a modest but significant decrease in the frequency of latently-infected cells was noted in three of the four patients 15. However, given that at least two studies have demonstrated that intensification of anti-HIV therapy decreases the half-life of this population 16, 17, it is unclear whether VPA or intensification of HAART with enfuvirtide was the critical factor for the decay of the latent reservoir. Recent reports have failed to show a decay of resting CD4 T cell infection in patients who were prescribed VPA for clinical reasons while receiving standard HAART 18, 19, 20. These results led to question the therapeutic potential of VPA, at least when used alone, to reduce the size of the latent HIV-1 reservoirs.

We have previously demonstrated a strong synergistic activation of HIV-1 promoter activity by the HDACI trichostatin A TSA and the NF-κB inducer TNFα in the postintegration latency model cell line U1 3, 21, suggesting that combinations of two independent factors NF-κB and chromatin involved in HIV-1 reactivation from latency might be potent tools to decrease the pool of latently-infected reservoirs. However, because of their toxicity, the therapeutic use of TNFα and TSA is not possible. Here, we investigated the HIV-1 reactivating potential of a treatment combining HDACIs used in human clinical trials or therapies such as VPA and suberoylanilide hydroxamic acid SAHA and an NF-κB inducer with no tumor-promoting effects, prostratin. This compound is an inducer of protein kinase C activity which stimulates HIV-1 expression in latently-infected lymphoid and myeloid cell lines and primary cells 22, 23, 24, 25, 26, 27, 28, 29 with minimal effects on the immune system 26 and causing minimal cell cycle progression 26, 29. Moreover, prostratin also inhibits de novo HIV-1 infection via posttranscriptional downregulation of the cellular HIV-1 receptors CD4 and CXCR4 CXC chemokine receptor 4 24, 27, 30, 31, 32. Therefore, the antimitogenic property of prostratin coupled with its dual activity on HIV-1 infection inhibition of viral infection and upregulation of latent provirus expression, its relatively non-toxic behavior and its potential widespread effect on different HIV-1 reservoirs, make this compound a good candidate for viral purging. Although the suitability of prostratin for use in humans is unknown since preclinical testing in compliance with Food and Drug Administration regulations is reportedly still underway 12, 33, preliminary pharmacokinetic studies are encouraging as they show that 5 of 5 mice survived with no obvious effects at 100 µmol/Kg intragastric dose of prostratin with plasma concentrations reaching up to 1.42 µmol/L 24. These results are not surprising as plant extracts of Homalanthus nutans a source of prostratin have already been used by the Samoan healers to treat individuals with certain medical conditions such as hepatitis 34, 35.

Here, we demonstrated that a combination of prostratin VPA or prostratin SAHA reactivated more efficiently than each compound alone HIV-1 production both in several latently-infected cell lines U1 and J-Lat clones and in CD8 -depleted peripheral blood mononuclear cells PBMCs isolated from HIV-1-infected patients receiving HAART and with undetectable viral load. Mechanistically, HDACI increased prostratin-induced NF-κB activation and potentiated nuc-1 remodeling. Moreover, prostratin HDACI combined treatment caused a synergistic activation of HIV-1 transcriptional initiation and elongation. Our results constitute a proof-of-concept for the coadministration of two different types of therapeutically promising HIV-1 inducers one acting on the NF-κB pathway and the other acting on the protein acetylation status together with HAART as a therapeutic perspective to decrease the pool of latent HIV-1 reservoirs.

Our Progress in Developing Prostratin. Significant progress has been made in the study of prostratin and its possible role as a novel anti-HIV therapeutic work.

Prostratin Antagonizes HIV Latency by Activating NF-κB Samuel A. Williams.

Prostratin: activation of latent HIV-1 expression suggests a potential inductive adjuvant therapy for HAART.

Prostratin, we have analysed the effect of prostratin on HIV activation and HIV receptor and coreceptors surface expression in human lymphocytes. Peripheral blood.

Highly active antiretroviral therapy HAART often reduces human immunodeficiency virus HIV viral loads below detection levels and can greatly prolong the time to progression to AIDS 21. However, replication-competent HIV persists in latently infected resting CD4 T cells despite HAART 7, 10, 26. It remains unclear to what extent the existence of viral reservoirs in latently infected resting T cells affects the prospects for long-term control or cure of HIV infection. The viral rebound that almost always occurs following cessation of HAART is largely due to residual replication that continues despite HAART 8, 11. However, the lifetime of the latently infected resting T-cell reservoir suggests that it could ultimately prevent the eradication of HIV from an infected individual 9. Given the lack of effective anti-HIV immune responses in infected individuals, even following effective HAART 2, long-lasting viral reservoirs represent a fundamental barrier to the eventual cure for HIV infection.

One proposed method to overcome this latent barrier is to induce the replication of HIV in latently infected resting T cells while preventing the spread of the newly produced virions to uninfected cells by providing HAART simultaneously 5, 15. For this purpose, activation of the latently infected resting T cells would accelerate the rate of decay of this viral reservoir either by the cytopathic effects of replicating virus or by exposing these cells to immune surveillance as a result of the expression of viral antigens.

Prostratin is a phorbol ester isolated from Homalanthus nutans, a plant used by healers in Western Samoa as a traditional remedy for illnesses such as yellow fever 14. Unlike many phorbol esters, prostratin is not tumor promoting 14, 23, 24, 25. It has been demonstrated that prostratin activates the replication of HIV in two latently infected cell lines 13, 14. However, a phorbol ester might not necessarily affect primary cells in the same manner as infected cell lines. Furthermore, these cell lines may not accurately reflect postintegration HIV latency in primary cells.

Recently, we reported that latently infected primary T cells can be generated in a severe combined immunodeficient mouse containing human fetal thymus and liver cells SCID-hu Thy/Liv mouse 4. During thymopoiesis, immature hematopoietic precursor cells undergo a series of replication, differentiation, and selection steps that result in the eventual export of mature CD4 and CD8 T lymphocytes into the peripheral blood. As thymocytes mature, the transcriptionally active immature cells become transcriptionally quiescent. We previously used the HIV-infected SCID-hu Thy/Liv mouse model to establish that reactivatible HIV can be generated at high frequency during thymopoiesis and that latently infected mature cells can be exported into the periphery of the animal 4. This provides a unique model to study agents that could potentially activate the latent T-cell reservoir. Therefore, to investigate the potential of prostratin to activate latent HIV infection, we evaluated the T-cell-stimulating activity of prostratin in primary cultures of human peripheral blood lymphocytes PBLs and in ex vivo cultures of latently infected human thymocytes and peripheral cells from the SCID-hu model.

Human immunodeficiency virus HIV replication is linked to cellular gene transcription and requires target cell activation. The latent reservoir of HIV-1 in.

Jun 30, 2009  Synergistic activation of HIV-1 production by prostratin and clinically used HDACIs. HDACIs present several advantages for HIV-1 purging strategies.