Parallel conduction of the phase I preventive and therapeutic trials based on the Tat vaccine candidate.

The native HIV-1 Tat protein was chosen as vaccine candidate for phase I clinical trials in both uninfected (ClinicalTrials.gov identifier: NCT00529698) and infected volunteers (ClinicalTrials.gov identifier: NCT00505401). The rationale was based on the role of Tat in the natural infection and AIDS pathogenesis, on the association of Tat-specific immune responses with the asymptomatic stage and slow-progression rate as well as on its sequence conservation among HIV clades (http://www.hiv1tat-vaccines.info/). The parallel conduction in the same clinical centers of randomized, double blind, placebo-controlled phase I studies both in healthy, immunologically competent adults and in HIV-infected, clinically asymptomatic, individuals represents a unique occasion to compare the vaccine-induced immune response in both the preventive and therapeutic setting. In both studies, the same lot of the native Tat protein was administered 5 times, every four weeks, subcute (SC) with alum adjuvant or intradermic (ID), in the absence of adjuvant, at 7.5 microg, 15 microg or 30 microg doses, respectively. The primary and secondary endpoints of these studies were the safety and immunogenicity of the vaccine candidate, respectively. The study lasted 52 weeks and monitoring was conducted for on additional 3 years. The results of both studies indicated that the Tat vaccine is safe and well tolerated both locally and systemically and it is highly immunogenic at all the dosages and by both routes of administration. Vaccination with Tat induced a balanced immune response in uninfected and infected individuals. In particular, therapeutic immunization induced functional antibodies and partially reverted the marked Th1 polarization of anti-Tat immunity seen in natural infection, and elicited a more balanced Th1/Th2 immune response. Further, the number of CD4 T cells correlated positively with anti-Tat antibody titers. Based on these results, a phase II study is ongoing in infected drug-treated individuals (http://www.hiv1tat-vaccines.info/).

Improved automated perimetry performance following exposure to Mozart.

AIM: To evaluate the performance on automated perimetry (AP) after listening to a Mozart sonata in normal subjects naive to AP. METHODS: 60 naive normal subjects underwent AP (SITA 24-2). The study group (30 subjects) underwent AP after listening to Mozart's Sonata for Two Pianos in D Major and the control group (30 subjects) underwent AP without previous exposure to the music. RESULTS: The study group had significantly less fixation loss, false positive, and false negative rates compared to controls (p < 0.05). CONCLUSION: Listening to Mozart seems to improve AP performance in normal naive subjects.

Red blood cell-mediated delivery of recombinant HIV-1 Tat protein in mice induces anti-Tat neutralizing antibodies and CTL.

The immunotherapeutic potential of biologically active HIV-1 Tat protein coupled to autologous red blood cells (RBCs) was evaluated in a mouse model. HIV-1 Tat expressed in Escherichia coli and purified to homogeneity was found to be active in viral trans activation and efficiently internalised by monocyte-derived dendritic cells (MDDCs). The product of HIV-Tat biotinylation and coupling to RBCs by means of a biotin-avidin-biotin bridge, (RBC-Tat), showed no trans activation activity and was still efficiently internalized by MDDCs as compared to uncoupled Tat.Balb/c mice were then immunized with 10 microg of soluble Tat in complete Freund's adjuvant or with 40 ng of Tat coupled on RBCs surface and boosted at week 3, 6 and 25 with 5 microg soluble Tat in incomplete Freund's adjuvant or with 20 ng of RBC-coupled Tat, respectively. Anti-Tat antibody response was similar in both groups; however, 2/6 animals immunized with soluble Tat and 6/6 animals immunized with RBC-Tat developed anti-Tat neutralizing antibodies. In addition, at week 28 cytolytic anti-Tat CTLs were detected in all animals although they were slightly higher in mice immunized with RBC-Tat. These results indicate that RBC-mediated delivery of HIV-1 Tat, in amounts 250 times lower than soluble Tat, is safe and induces specific CTL responses and neutralizing antibodies.

Lymphomononuclear cells from multiple sclerosis patients spontaneously produce high levels of oncostatin M, tumor necrosis factors alpha and beta, and interferon gamma.

Proinflammatory cytokines are deemed to play a pivotal role in the pathogenesis of multiple sderosis (MS). They provide signals for T-cell activation and inflammatory cell recruitment in the brain and might directly alter neuroglial and neuronal cell survival and function. We found that peripheral blood mononuclear cells (PBMCs) from MS patents spontaneously produce high levels of TNFalpha, TNFbeta, IFNgamma, and oncostatin M (oncM), a proinflammatory cytokine actng on cells of neural, vascular, hematopoietic, and lymphoid origin. Spontaneous production of these cytokines was significantly higher (p < 0.01) in PBMC short-term culture supernatants from MS patients than in blood donors (HC). On average, lectin-induced production of these cytokines by PBMC was higher in MS patents than in HC significantly so only for TNFalpha (p = 0.013). Determination of TNFalpha, TNFbeta IFNgamma, and oncM in corresponding sera showed that on average, oncM levels were higher in MS patients than in HC, though the results were not statistically significant whereas levels of TNFalpha, TNFbeta and IFNgamma were below the assay threshold in most patients. The finding that MS PBMCs are primed in vivo to produce and release high levels of proinflammatory cytokines suggests the presence of a basal activation of the immune system which, in turn, may play a role in the complex circuitry of molecular and cellular interactions responsible for neurologic damage in MS.

Endogenous cytokine production protects T cells from spontaneous apoptosis during highly active antiretroviral therapy.

BACKGROUND: The availability of therapeutic regimens that effectively interfere with HIV-1 replication provides novel opportunities to investigate mechanisms of T-cell depletion as well as repopulation in infected individuals. METHODS: Nineteen HIV-1-infected individuals were investigated during one-year follow-up of highly active retroviral therapy (HAART). The frequencies of apoptotic T cells, as determined by propidium iodide, staining, TUNEL assay and analysis of annexin V, were assessed either in the absence or in the presence of anti-interleukin (IL)2 and anti-IL-4 neutralizing Ab. Spontaneous and lectin-induced cytokine production were assessed by ELISA. RESULTS: Increments of both naive and memory CD4 and CD8 T cells during HAART are accompanied by a decrease of T-cell apoptosis that, after 12 months of HAART, reaches normal levels. This is associated with increments of both spontaneous and activation-induced production of IL-2 and IL-4 by peripheral blood mononuclear cells (PBMCs), though only the latter was found defective at enrolment. During HAART, blocking of either IL-2 or IL-4 production by PBMCs using neutralizing Ab restores levels of T-cell apoptosis consistent with those determined at enrolment. These data suggest that both IL-2 and IL-4 produced by PBMCs during HAART provide anti-apoptotic signals that can contribute to an increased survival of T cells and may thus play a part in long-term immune reconstitution. CONCLUSIONS: An effective viral suppression and, possibly, effects of PI on molecular targets other than viral components, can support a progressive normalization of T-cell survival that, at least in part, depends upon the restoration of proper soluble signals. These results provide evidence of a supporting role of endogenous cytokine production in peripheral T-cell repopulation during an effective and prolonged viral suppression. This may be relevant for the definition of immune-intervention targets aimed at immune reconstitution in HIV-1-infected patients.

Distribution of the natural killer-related receptor for HLA-C during highly active antiretroviral therapy for human immunodeficiency virus infection.

Receptors interacting with Major Histocompatibility Complex class I molecules have been initially found on the surface of human natural killer (NK) cells, where they deliver inhibitory signals to the lysis, being thus defined killer inhibitory receptors (KIR). Subsequently, they were detected also on the surface of T-CD8(+) lymphocytes and are particularly expanded during human immunodeficiency virus (HIV) infection, where they downregulate HIV-specific cytolysis. The expression of KIR recognizing human leukocyte antigen-C alleles was assessed in HIV-infected patients, undergoing highly active antiretroviral therapy (HAART). To this end, the combined expression of CD16/CD56, of CD3 and CD8 as well as of KIR (CD158a and CD158b) surface molecules was analyzed on peripheral blood mononuclear cells by monoclonal antibodies, and flow cytometry. An increase of CD3(+)CD8(+)CD158b(+) cells was found after 6 months of HAART. This finding may have implications for the regulation of T-cell mediated cytolysis during HAART.

Role of immune-derived diffusible mediators in AIDS-associated neurological disorders.

Neurologic abnormalities are common in HIV-1 infected patients and often represent the dominant clinical manifestation of pediatric AIDS. Although the neurological dysfunction has been directly related to CNS invasion by HIV-1, the pathogenesis of neurologic disorders remains unclear. This review will first discuss the spectrum of potential interactions between HIV-1 and neural (neuronal and glial) cells, in the face of experimental data. Next, we will focus on the role of immune-derived cytokines and other soluble compounds which have been proposed to act as neurotoxic mediators and appear to play a role in the pathogenesis of AIDS-associated neurodegeneration.

Decreased T cell apoptosis and T cell recovery during highly active antiretroviral therapy (HAART).

T cell apoptosis represents a common mechanism of T cell depletion in HIV-1-infected individuals reflecting maturational and functional T cell abnormalities either directly or indirectly induced by the virus. In the present study, the effects of highly active antiretroviral therapy (HAART) on the spontaneous apoptosis of distinct T cell subsets were investigated during a 6-month follow-up in a cohort of HIV-1-infected individuals with CD4(+) cell counts between 100 and 500 cells/microliter and plasma HIV-1 RNA levels >/=10, 000 copies/ml. We determined that the rapid and sustained increase of both naive (CD45RA(+)CD62L(+)) and memory (CD45R0(+) and CD45RA(+)/CD62L(-)) CD4(+) and, to as lesser extent, CD8(+) T cells in peripheral blood was associated with a significant decrease of apoptotic CD4(+) and CD8(+) as well as CD3(+)CD4(-)CD8(-) T cells. Among CD4(+) lymphocytes, at enrollment, the highest frequency of apoptotic cells was observed within the memory compartment, as defined by CD45R0 expression. During HAART, however, the frequency of CD4(+)CD45R0(+) apoptotic T cells progressively decreased in association with a significant downregulation of surface activation markers that indicated decreased levels of systemic immune stimulation. These results indicate that effective viral suppression can contribute to progressive normalization of maturational and functional T cell abnormalities responsible for the high levels of T cell apoptosis in HIV-1-infected individuals. This, in turn, may contribute to a reduced rate of T cell loss and immune reconstitution during HAART.

CCR5 and CXCR4 chemokine receptor expression and beta-chemokine production during early T cell repopulation induced by highly active anti-retroviral therapy.

Expression of chemokine receptors and beta-chemokine production by peripheral blood mononuclear cells (PBMC) were determined in HIV-1-infected individuals before and after highly active anti-retroviral therapy (HAART) and their relationship to viral load, T cell phenotype and the expression of immunological activation markers was examined. We found that the expression of CCR5 is up-regulated in HIV-1-infected individuals while CXCR4 appears down-regulated on both CD4 and CD8 T cells compared with normal controls. These alterations are associated with the high levels of viral load. In addition, a relationship was observed between the degree of immune activation and chemokine receptor expression on T cells. However, after 3 months of combined anti-retroviral regimen, expression of CXCR4 significantly increased while CCR5 decreased when compared with pretherapy determinations. This was seen in strict association with a dramatic decrease of viral load and an increase of both CD45RA+/CD62L+ (naive) and CD45RA-/CD62L+ or CD45RA+/CD62L- (memory) T cells accompanied by a significant decrease of the expression of immune activation markers such as HLA-DR and CD38. At enrolment, both spontaneous and lectin-induced RANTES, macrophage inflammatory protein-1alpha (MIP-1alpha) and MIP-1beta production by PBMC were higher in HIV-1-infected individuals compared with normal controls, although differences for MIP-1beta were not statistically significant. However, RANTES and MIP-1alpha production decreased during HAART at levels closer to that determined with normal controls, while MIP-1beta production was less consistently modified. These data indicate that the expression of chemokine receptors CCR5 and CXCR4 and the production of beta-chemokines are altered in HIV-infected individuals, and suggest that their early modifications during HAART reflect both the peripheral redistribution of naive/memory T cell compartments and the decrease in levels of T cell activation. Such modifications in the expression of host determinants of viral tropism and the production of anti-viral molecules may play a role in the emergence of virus variants when a failure of HAART occurs.

The Tat protein of human immunodeficiency virus type-1 promotes vascular cell growth and locomotion by engaging the alpha5beta1 and alphavbeta3 integrins and by mobilizing sequestered basic fibroblast growth factor.

The Tat protein of human immunodeficiency virus type-1 (HIV-1) has been shown to be released during acute infection of T cells by HIV-1 and to promote angiogenesis and Kaposi's sarcoma (KS) development in infected individuals. In this study, we investigated the molecular mechanisms responsible for the angiogenic effects of Tat. The results shown herein indicate that two different Tat domains cooperate to induce these effects by different pathways. The arginine-glycine-aspartic acid (RGD) sequence present at the carboxyterminal of Tat mediates vascular cell migration and invasion by binding to the alpha5beta1 and alphavbeta3 integrins. This interaction also provides endothelial cells with the adhesion signal they require to grow in response to mitogens. At the same time, the Tat basic sequence retrieves into a soluble form extracellular basic fibroblast growth factor (bFGF) bound to heparan sulfate proteoglycans by competing for heparin-binding sites. This soluble bFGF mediates Tat-induced vascular cell growth. These effects resemble those of extracellular matrix proteins, suggesting that Tat enhances angiogenesis and promotes KS progression by a molecular mimicry of these molecules.

Immune-derived cytokines in the nervous system: epigenetic instructive signals or neuropathogenic mediators?

The investigation of the effects of inflammatory cytokines (IC) on the growth and differentiation of neural cells has provided new insights on the role of such soluble mediators in nervous system development and/or plastic remodeling as well as in the pathogenesis of inflammatory neurodegenerative disorders, which are characterized by chronic IC dysregulation in the central nervous system (CNS). Thus, the study of the interaction between CNS and immune-derived soluble signals in physiological or pathological conditions is of increasing interest. This review first discusses experimental evidence supporting the instructive/permissive role of immune-derived cytokines on CNS development and plasticity. Next, we focus on human neurological disease states such as multiple sclerosis and the neurodegeneration associated to the acquired immune deficiency syndrome in which different inflammatory cytokines have been proposed as potential neuropathogenic mediators.

Inflammatory cytokines and HIV-1-associated neurodegeneration: oncostatin-M produced by mononuclear cells from HIV-1-infected individuals induces apoptosis of primary neurons.

Neurologic abnormalities are common in HIV-1-infected patients and often represent the dominant clinical manifestation of pediatric AIDS. The neurological dysfunction has been directly related to CNS invasion by HIV-1 that is principally, if not exclusively, supported by blood-derived monocytes/macrophages and lymphocytes. By using primary long term cultures of human fetal sensory neurons as well as sympathetic precursors-like neuronal cells, we determined that blood-derived mononuclear cells from HIV-1-infected individuals spontaneously release soluble mediators that can potently inhibit the growth and survival of developing neurons as well as the viability of postmitotic neuronal cells by inducing apoptotic cell death. Analysis of the cytokines produced by lymphomonocytic cells, HIV-1 infected or activated, indicated that oncostatin M (oncM) is a major mediator of these effects. Since low TGF-beta1 concentrations were capable of enhancing oncM-mediated neuronal alterations, our data indicate that by acting in concert with other cytokines, oncM may induce neuronal demise in both the developing and the mature brain. Thus, this cytokine may contribute to the setting of the neuronal cell damage observed in HIV-1-infected individuals.

IFN-gamma induces endothelial cells to proliferate and to invade the extracellular matrix in response to the HIV-1 Tat protein: implications for AIDS-Kaposi's sarcoma pathogenesis.

Previous studies indicated that the Tat protein of HIV functions as a progression factor in Kaposi's sarcoma (KS), an angioproliferative disease common and aggressive in HIV-1-infected individuals (AIDS-KS). In particular, Tat that is released by infected cells stimulates the growth and invasion of spindle cells of endothelial origin derived from KS lesions (KS cells). Other work suggested that inflammatory cytokines may act as initiating factors in KS since they induce normal endothelial cells to acquire the same phenotype and functional features of KS cells, including the responsiveness to Tat. In this study, we show that among the inflammatory cytokines increased in AIDS-KS lesions, IFN-gamma alone is sufficient to induce endothelial cells to proliferate and to invade the extracellular matrix in response to Tat. This is because IFN-gamma up-regulates the expression and activity of the receptors for Tat identified as the integrins alpha5beta1 and alpha(v)beta3. These results suggest that, by triggering Tat effects, IFN-gamma plays a major role in AIDS-KS pathogenesis.

Basic fibroblast growth factor supports human olfactory neurogenesis by autocrine/paracrine mechanisms.

Throughout life, olfactory sensory neurons are renewed from a population of dividing stem cells. Little is known about the molecular mechanisms that regulate the activation, self-renewal and differentiation of olfactory neuronal precursors; however, evidence indicates that soluble mediators may play a central role in olfactory neurogenesis. To identify molecules that regulate olfactory self-renewal and differentiation, we have recently established, cloned and propagated in vitro primary long-term cell cultures from the human fetal olfactory neuroepithelium. Here we show that primary human olfactory neuroblasts synthesize and release biologically active basic fibroblast growth factor which, in turn, supports neuroblast growth by autocrine/paracrine mechanisms. The growth-promoting activity of basic fibroblast growth factor is dose dependent and is accompanied by morphological changes of the cells and by an increase in the expression of neuronal-related genes. These observations indicate that endogenous basic fibroblast growth factor participates in controlling olfactory self-renewal and suggest that this cytokine represents a key regulatory element of olfactory neurogenesis.

gamma-Interferon produced by CD8+ T cells infiltrating Kaposi's sarcoma induces spindle cells with angiogenic phenotype and synergy with human immunodeficiency virus-1 Tat protein: an immune response to human herpesvirus-8 infection?

Kaposi's sarcoma (KS) is an angioproliferative disease associated with infection by the human herpesvirus-8 (HHV-8). HHV-8 possesses genes including homologs of interleukin-8 (IL-8) receptor, Bcl-2, and cyclin D, which can potentially transform the host cell. However, the expression of these genes in KS tissues is very low or undetectable and HHV-8 does not seem to transform human cells in vitro. In addition, KS may not be a true cancer at least in the early stage. This indicated that besides its transforming potential, HHV-8 may act in KS pathogenesis also through indirect mechanisms. Evidence suggests that KS may start as an inflammatory-angiogenic lesion mediated by cytokines. However, little is known on the nature of the inflammatory cell infiltration present in KS, on the type of cytokines produced and on their role in KS, and whether this correlates with the presence of HHV-8. Here we show that both acquired immunodeficiency syndrome (AIDS)-KS and classical KS (C-KS) lesions are infiltrated by CD8+ T cells and CD14+/CD68+ monocytes-macrophages producing high levels of gamma-interferon (gamma IFN) which, in turn, promotes the formation of KS spindle cells with angiogenic phenotype. gamma IFN, in fact, induces endothelial cells to acquire the same features of KS cells, including the spindle morphology and the pattern of cell marker expression. In addition, endothelial cells activated by gamma IFN induce angiogenic lesions in nude mice closely resembling early KS. These KS-like lesions are accompanied by production of basic fibroblast growth factor, an angiogenic factor highly expressed in primary lesions that mediates angiogenesis and spindle cell growth. The formation of KS-like lesions is upregulated by the human immunodeficiency virus Tat protein demonstrating its role as a progression factor in AIDS-KS. Finally, gamma IFN and HLA-DR expression correlate with the presence of HHV-8 in lesional and uninvolved tissues from the same patients. As HHV-8 infects both mononuclear cells infiltrating KS lesions and KS spindle cells, these results suggest that HHV-8 may elicit or participate in a local immune response characterized by infiltration of CD8+ T cells and intense production of gamma IFN which, in turn, plays a key role in KS development.

gamma-Interferon production in peripheral blood mononuclear cells and tumor infiltrating lymphocytes from Kaposi's sarcoma patients: correlation with the presence of human herpesvirus-8 in peripheral blood mononuclear cells and lesional macrophages.

Evidence indicates that, at least in the early stage, Kaposi's sarcoma (KS) is a cytokine-mediated disease and that it is consistently associated with a novel herpesvirus termed human herpesvirus-8 (HHV-8). To gain insights into the mechanisms by which cytokines and HHV-8 may cooperate in disease pathogenesis, we examined the phenotype, the Th1 (gamma-interferon [gamma IFN]) and Th2 (interleukin-4 [IL-4] cytokine profile and the presence of HHV-8 in peripheral blood mononuclear cells (PBMC), tumor-infiltrating lymphocytes (TIL), and spindle cell cultures derived from skin lesions of patients affected by classical KS (C-KS) and acquired immunodeficiency syndrome (AIDS)-associated KS (AIDS-KS). TIL and spindle cell cultures were examined at day 0 or after culture in conditioned media from activated T cells (TCM) that contain the same cytokines increased in KS tissues. No differences were found in the immunophenotype of PBMC from C-KS patients versus controls, except for AIDS-KS patients who showed a T-CD8+ expansion. However, a preferential infiltration of T-CD8+ cells was found in all KS lesions examined, which was maintained after culture of TIL in TCM. gamma IFN production was found in both PBMC and cultures derived from all KS examined; some IL-4 positive supernatants were found only in three AIDS-KS cases. Uninvolved skin did not show appreciable lymphocyte infiltration or cytokine production. The culture conditions of the lesional skin allowed also the appearance of adherent, spindle-like cells bearing markers of tissue macrophages. Finally, most or all of the PBMC, lesions, and macrophagic cell cultures from the skin lesions were found to be positive for HHV-8 infection by nested polymerase chain reaction (PCR). These findings indicate that patients with KS express a Th1 phenotype with a prevalent gamma IFN production, likely accounted for by the local T-CD8+ infiltration. By analogy with other viral infections (i.e., Epstein-Barr virus), this suggests that in loco recruitment of lymphoid cells and the subsequent gamma IFN production may be in response to or elicited by HHV-8 that was found in both PBMC and macrophagic cell cultures from the lesions of the same patients.

HIV-1 infection and the developing nervous system: lineage-specific regulation of viral gene expression and replication in distinct neuronal precursors.

Neurologic abnormalities are common in HIV-1 infected patients and often represent the dominant clinical manifestation of pediatric AIDS. Although the neurological dysfunction has been directly related to CNS invasion by HIV-1, the pathogenesis of neurologic disorders remains unclear. Microglia and macrophages are major HIV-1 targets in the brain, whereas HIV-1 infected neurons or glial cells have been rarely reported. This suggests that indirect mechanisms may account for the severe neuronal damage observed in these patients. Nevertheless, immature, mitotically active neuronal and glial cells, which are present during fetal development, are susceptible to HIV-1 infection and replication in vitro, suggesting that HIV-1 infection during organ development may present unique features. To better characterize virus-host cells interactions in the developing CNS, we have examined the susceptibility of embryologically and biochemically distinct neuronal cell lines to HIV-1 infection. Here we show that mitotically active, immature neurons of distinct lineages, have different susceptibilities to HIV-1 infection and replication and different abilities to support viral gene expression. Mutational analysis of HIV-1 LTR reveals that a region of the viral promoter between nucleotide -255 to -166 is responsible for most quantitative and qualitative differences in viral transactivation among different neuroblasts. This suggests that specific regions of the viral promoter and cellular factors, either lineage- or differentiation-dependent, which bind to those regions, may contribute to control the levels of virus replication and possibly restrict the viral tropism in the developing brain. This may contribute to the establishment of a virus reservoir in the immature CNS and participate by either direct or indirect mechanisms to the severity of the AIDS-related pediatric neurological dysfunction.

New developments: a look to the future.

Inflammatory cytokines plus the human immunodeficiency virus Tat protein apparently trigger the development of early Kaposi's sarcoma. Activated spindle cells provide a self-perpetuating, autocrine-supported mechanism for further development of hyperplastic lesions. In more advanced stages, a true neoplastic process may develop.

HIV-1 infection of primary human neuroblasts.

Central nervous system (CNS) disorders are frequent in HIV-1-infected individuals, particularly in newborns and children, and are accompanied by histological alterations resulting in neuronal loss. Although several tumor-derived neuroectodermal cell lines can be infected by HIV-1, it has been reported that primary neural cells cannot be infected after they differentiate. However, pediatric AIDS is often the result of HIV-1 infection occurring during fetal development and early postnatal life, when neural cells are not yet differentiated. Here we show that primary cell cultures derived from the human fetal olfactory system which are representative of the developing CNS can be infected by both HIV-1 strains, the monocyte-macrophagotropic BaL and the lymphotropic HTLV-IIIB, although they do not express the CD4 molecule. In addition, the levels of viral replication are higher with the HIV-1 BaL than with the IIIB isolate. These results suggest that (1) during development immature neurons are susceptible to HIV-1 infection; (2) monocyte-macrophagotropic HIV-1 strains may preferentially be involved in the productive infection of the nervous system; and (3) a mechanism(s) other than the CD4-mediated viral entry is responsible for HIV-1 infection of immature neurons.

Cytokines from activated T cells induce normal endothelial cells to acquire the phenotypic and functional features of AIDS-Kaposi's sarcoma spindle cells.

Kaposi's sarcoma (KS) is a proliferative disease of vascular origin particularly frequent in HIV-1-infected homosexual men (AIDS-KS) and characterized by proliferating spindle-shaped cells, angiogenesis, and inflammatory cell infiltration. Previous work has suggested that KS spindle cells are of endothelial cell origin and that chronic immune activation via the release of inflammatory cytokines may cooperate with basic fibroblast growth factor (bFGF) and the HIV-1 Tat protein in the induction and progression of AIDS-KS. Here we show that KS spindle cells have features of activated endothelial cells, and that conditioned media from activated T cells, rich in the same inflammatory cytokines increased in HIV-1-infected individuals, induce normal endothelial cells to acquire the phenotypic and functional features of KS cells. These include (a) acquisition of a similar pattern of cell surface antigen expression; (b) similar proliferative response to bFGF; (c) induction of the responsiveness to the mitogenic effect of extracellular HIV-1 Tat protein that is now able to promote the G1-S transition of endothelial cell cycle; and (d) induction in nude mice of vascular lesions closely resembling early KS as well as the lesions induced by inoculation of KS cells. These results suggest that chronic immune activation, via release of inflammatory cytokines, may play a role in the induction of KS.