Fibroblast Growth Factor-2 and the HIV-1 Tat Protein Synergize in Promoting Bcl-2 Expression and Preventing Endothelial Cell Apoptosis: Implications for the Pathogenesis of AIDS-Associated Kaposi's Sarcoma

Kaposi's sarcoma (KS) is a vascular tumor frequently occurring in Human Immunodeficiency Virus- (HIV-) 1-infected individuals. Our previous work indicated that the angiogenic fibroblast growth factor (FGF)-2 and the Tat protein of HIV-1, both expressed in KS lesions of HIV-infected patients, synergize at inducing angioproliferative, KS-like lesions in mice. Here we show that the development of angioproliferative lesions promoted in mice by combined Tat and FGF-2 associates with an increase in the levels of expression of the antiapoptotic Bcl-2 protein. Upregulation of Bcl-2 expression by combined FGF-2 and Tat occurs also in vitro, and this protects human primary endothelial cells from programmed cell death. As Bcl-2 is expressed in human KS lesions in a fashion paralleling the progression of the disease, these findings suggest a molecular mechanism by which Tat and FGF-2 cooperate in KS maintenance and progression in HIV-infected individuals

HIV-1 tat protein enters dysfunctional endothelial cells via integrins and renders them permissive to virus replication

Previous work has shown that the Tat protein of Human Immunodeficiency Virus (HIV)-1 is released by acutely infected cells in a biologically active form and enters dendritic cells upon the binding of its arginine-glycine-aspartic acid (RGD) domain to the α5β1, αvβ3, and αvβ5 integrins. The up-regulation/activation of these integrins occurs in endothelial cells exposed to inflammatory cytokines that are increased in HIV-infected individuals, leading to endothelial cell dysfunction. Here, we show that inflammatory cytokine-activated endothelial cells selectively bind and rapidly take up nano-micromolar concentrations of Tat, as determined by flow cytometry. Protein oxidation and low temperatures reduce Tat entry, suggesting a conformation- and energy-dependent process. Consistently, Tat entry is competed out by RGD-Tat peptides or integrin natural ligands, and it is blocked by anti-α5β1, -αvβ3, and -αvβ5 antibodies. Moreover, modelling-docking calculations identify a low-energy Tat-αvβ3 integrin complex in which Tat makes contacts with both the αv and β3 chains. It is noteworthy that internalized Tat induces HIV replication in inflammatory cytokine-treated, but not untreated, endothelial cells. Thus, endothelial cell dysfunction driven by inflammatory cytokines renders the vascular system a target of Tat, which makes endothelial cells permissive to HIV replication, adding a further layer of complexity to functionally cure and/or eradicate HIV infection

Kaposi's Sarcoma Lesion Progression in {BKV}-Tat Transgenic Mice Is Increased by Inflammatory Cytokines and Blocked by Treatment with Anti-Tat Antibodies

Kaposi’s sarcoma (KS) is an angioproliferative tumor showing an increased frequency and ag-gressiveness in HIV-infected subjects (AIDS-KS), due to the combined effects of inflammatory cytokines (IC), angiogenic factors, and the HIV-1 Tat protein. While the introduction of effective combined antiretroviral regimens greatly improved AIDS-KS incidence and course, it continues to be an incurable disease and the development of new rational targeted therapies is warranted. We used the BKV/Tat transgenic mouse model to evaluate the effects of IC and anti-Tat antibod-ies (Abs) treatment on KS-like lesions arising in BKV/Tat mice . We demonstrated here that IC-treatment increases the severity and delays the regression of KS-like lesions arising in BKV/Tat mice. Further, anti-Tat Abs reduced KS-like lesion severity developing in IC-treated mice when anti-Tat Abs were administered at an early-stage of lesion development as compared to more advanced lesions. Early anti-Tat Abs treatment also accelerated KS-like lesion regres-sion and reduced the rate of severe-grade lesions. This effect was more evident in the first weeks after Ab treatment, suggesting that a longer treatment with anti-Tat Abs might be even more ef-fective, particularly if administered just after lesion development. Although preliminary, these results are encouraging, and the approach deserves further studies for the development of an-ti-Tat Ab-based therapies for AIDS-KS. Clinical studies specifically addressing the effect of an-ti-Tat antibodies in treating AIDS-KS are not yet available. Nevertheless, the effectiveness of an-ti-Tat antibodies in controlling HIV/AIDS progression, likely due to the neutralization of extra-cellular Tat activities, is suggested by several cross-sectional and longitudinal clinical studies, indicating that anti-Tat Ab treatment or Tat-based vaccines may be effective to treat AIDS-KS pa-tients or prevent the tumor in individuals at risk

Macrophages Transmit Human Immunodeficiency Virus Type 1 Products to CD4-Negative Cells: Involvement of Matrix Metalloproteinase 9▿

It was previously reported that human immunodeficiency virus type 1 (HIV-1) spreads in CD4 lymphocytes through cell-to-cell transmission. Here we report that HIV-1-infected macrophages, but not lymphocytes, transmit HIV-1 products to CD4-negative cells of either epithelial, neuronal, or endothelial origin in the absence of overt HIV-1 infection. This phenomenon was detectable as early as 1 h after the start of cocultivation and depended on cell-to-cell contact but not on the release of viral particles from donor cells. Transfer of HIV-1 products occurred upon their polarization and colocalization within zones of cell-to-cell contact similar to virological synapses. Neither HIV-1 Env nor Nef expression was required but, interestingly, we found that an HIV-1-dependent increase in matrix metalloproteinase 9 production from donor cells significantly contributed to the cell-to-cell transmission of the viral products. The macrophage-driven transfer of HIV-1 products to diverse CD4-negative cell types may have a significant role in AIDS pathogenesis

Mechanism of Paclitaxel Activity in Kaposi’s Sarcoma

Kaposi's sarcoma (KS) is an angioproliferative disease characterized by proliferation of spindle-shaped cells predominantly of endothelial cell origin, neoangiogenesis, inflammatory cell infiltration, and edema. At least in early stage, KS behaves as a reactive lesion sustained by the action of inflammatory cytokines and growth factors, has a polyclonal nature, and can regress. However, in time it can become monoclonal, especially in the nodular stage, evolving into a true sarcoma, likely in association with the increased expression of antiapoptotic oncogenes. We have recently demonstrated by immunohistochemical analysis that Bcl-2, a proto-oncogene known to prolong cellular viability and to antagonize apoptosis, is highly expressed in spindle cells and vessels of both AIDS-KS and classical KS lesions and that its expression increases with lesion stage. Paclitaxel, a microtubule-stabilizing drug known to inhibit Bcl-2 antiapoptotic activity and to be highly effective in the treatment of certain neoplasms, has recently been found to be active also in patients with advanced HIV-associated KS. In this report we investigated the mechanism(s) of paclitaxel activity in KS. By using a model of experimental KS induced by the inoculation of KS-derived spindle cells in nude mice and primary cultures of KS spindle cells, we found that paclitaxel promotes regression of KS lesions in vivo and that it blocks the growth, migration, and invasion of KS cells in vitro. Furthermore, paclitaxel treatment promoted apoptosis and down-regulated Bcl-2 protein expression in KS cells in vitro and in KS-like lesions in mice. Our results suggest that paclitaxel interferes with KS by down-regulating Bcl-2 antiapoptotic effect

Ritonavir or saquinavir impairs the invasion of cervical intraepithelial neoplasia cells via a reduction of MMP expression and activity.

Objective and design: Treatment of human immunodeficiency virus (HIV)-infected women with the highly active antiretroviral therapy (HAART) has reduced the onset of uterine cervical intraepithelial neoplasia (CIN), and halted its progression to cervical carcinoma. We and others demonstrated that the HIV protease inhibitors (HIV-PIs) used in HAART can exert direct antitumour activities also in HIV-free preclinical or clinical models. As uterine cervical carcinoma is a leading cause of death in women independently of HIV infection, herein we assessed the impact of therapeutic concentrations of HIV-PIs including indinavir (IDV), saquinavir (SQV) or ritonavir (RTV) on cells obtained from CIN or cervical carcinoma lesions of HIV-negative women. Methods: HIV-PI effects were evaluated by cell invasion, growth or toxicity assays, and by RNA, protein or zymogram analyses. Results: Both SQV and RTV inhibited CIN cell invasion, and this was paralleled by a reduced expression and proteolytic activity of the matrix metalloproteinase (MMP)-2 and 9 in treated cells. SQV and RTV also reduced CIN cell growth rate, but did not affect the invasion or growth of cells derived from highly progressed cervical carcinoma. Conclusion: As MMP-2 and MMP-9 have a key role in CIN evolution into cervical carcinoma, these results support the use of SQV or RTV for the block of CIN clinical progression in either HIV-infected or uninfected patients

HIV-1 Tat Promotes Integrin-Mediated HIV Transmission to Dendritic Cells by Binding Env Spikes and Competes Neutralization by Anti-HIV Antibodies

none44Use of Env in HIV vaccine development has been disappointing. Here we show that, in the presence of a biologically active Tat subunit vaccine, a trimeric Env protein prevents in monkeys virus spread from the portal of entry to regional lymph nodes. This appears to be due to specific interactions between Tat and Env spikes that form a novel virus entry complex favoring R5 or X4 virus entry and productive infection of dendritic cells (DCs) via an integrin-mediated pathway. These Tat effects do not require Tat-transactivation activity and are blocked by anti-integrin antibodies (Abs). Productive DC infection promoted by Tat is associated with a highly efficient virus transmission to T cells. In the Tat/Env complex the cysteine-rich region of Tat engages the Env V3 loop, whereas the Tat RGD sequence remains free and directs the virus to integrins present on DCs. V2 loop deletion, which unshields the CCR5 binding region of Env, increases Tat/Env complex stability. Of note, binding of Tat to Env abolishes neutralization of Env entry or infection of DCs by anti-HIV sera lacking anti-Tat Abs, which are seldom present in natural infection. This is reversed, and neutralization further enhanced, by HIV sera containing anti-Tat Abs such as those from asymptomatic or Tat-vaccinated patients, or by sera from the Tat/Env vaccinated monkeys. Thus, both anti-Tat and anti-Env Abs are required for efficient HIV neutralization. These data suggest that the Tat/Env interaction increases HIV acquisition and spreading, as a mechanism evolved by the virus to escape anti-Env neutralizing Abs. This may explain the low effectiveness of Env-based vaccines, which are also unlikely to elicit Abs against new Env epitopes exposed by the Tat/Env interaction. As Tat also binds Envs from different clades, new vaccine strategies should exploit the Tat/Env interaction for both preventative and therapeutic interventions. © 2012 Monini et al.openMonini P.; Cafaro A.; Srivastava I.; Moretti S.; Sharma V.; Andreini C.; Chiozzini C.; Ferrantelli F.; Pavone Cossut M.; Tripiciano A.; Nappi F.; Longo O; Bellino S.; Picconi O.; Fanales-Belasio E.;Borsetti A.; Toschi E.; Schiavoni I.; Bacigalupo I.; Kan E.; Sernicola L.; Maggiorella M.; Montin K.;Porcu M.; Leone P.; Leone P; Collacchi B.; Palladino C.; Ridolfi B.; Falchi M.; Macchia I.; UlmerJ.B.; Butto` S.; Sgadari C.; Magnani M.; Federico M.; Titti F.; Banci L.; Dallocchio F.; Rappuoli R.; Ensoli F.; Barnett S.W.; Garaci E.; Ensoli B.Monini, P.; Cafaro, A.; Srivastava, I.; Moretti, S.; Sharma, V.; Andreini, C.; Chiozzini, C.; Ferrantelli, F.; Pavone Cossut, M.; Tripiciano, A.; Nappi, F.; Longo, O; Bellino, S.; Picconi, O.; Fanales Belasio, E.; Borsetti, A.; Toschi, E.; Schiavoni, I.; Bacigalupo, I.; Kan, E.; Sernicola, L.; Maggiorella, M.; Montin, Katy; Porcu, M.; Leone, P.; Leone, P; Collacchi, B.; Palladino, C.; Ridolfi, B.; Falchi, M.; Macchia, I.; U. l. m. e. r. J., B.; Butto`, S.; Sgadari, C.; Magnani, M.; Federico, M.; Titti, F.; Banci, L.; Dallocchio, Franco Pasquale Filippo; Rappuoli, R.; Ensoli, F.; Barnett, S. W.; Garaci, E.; Ensoli, Barbar