The HIV tat gene induces dermal lesions resembling Kaposi's sarcoma in transgenic mice

Expression of the Human Immunodeficiency Virus-Tat Gene in Lymphoid Tissues of Transgenic Mice Is Associated With B-Cell Lymphoma

The human immunodeficiency virus type 1 (HIV-1) Tat gene, a potent transactivator of viral and cellular genes, has been proposed as a key agent in the pathogenesis of acquired immune deficiency syndrome related disorders, including nonHodgkin’s lymphoma. In cultured cells, the HIV-1 Tat protein can induce the expression of the cytokines interleukin-6 (IL-6) and IL-10, which are known to induce proliferation and differentiation of lymphoid cells. Such alterations in cytokine expression, together with a secondary genetic event, are thought to ultimately lead to oncogenic transformation. To address the influence of Tat on lymphoid development in the context of the whole organism, we produced several transgenic mouse lines that express the Tat gene under the control of an actin promoter. We show here that this promoter directs expression to a variety of sites, including spleen, bone marrow, and lymph nodes. Approximately 25% to 30% of the Tat-transgenic population developed enlarged spleens within 1 year after birth. On histological examination, a significant number of spleens from Tat-transgenic mice exhibited malignant lymphoma of B-cell origin. IgG heavy chain rearrangement confirmed the clonal B-cell nature of these lymphoproliferations. In contrast, T-cell receptor genes exhibited a germline (unrearranged) structure. Reverse transcription polymerase chain reaction analysis of transgenic spleens revealed that mRNA encoding cytokines IL-6 and IL-10 was upregulated, suggesting a possible mechanism for the B-cell expansion in vivo.

Inhibition of human immunodeficiency virus type 1 replication in vitro in acutely and persistently infected human CD4+ mononuclear cells expressing murine and humanized anti-human immunodeficiency virus type 1 Tat single-chain variable fragment intrabodies

We have previously reported that a murine anti-Tat sFv intrabody, termed sFvtat1Ck, directed against the proline-rich N-terminal activation domain of HIV-1, is a potent inhibitor of HIV-1 replication [Mhashilkar, A. M., et al. (1995). EMBO J. 14, 1542-1551]. In this study, the protective effect of sFvtat1Ck expression on HIV-1 replication in both acutely infected and persistently infected CD4+ cells was examined. Stably transfected CD4+ SupT1 cells were resistant to HIV-1 infection at high MOI with both the laboratory isolate HxB2 and six syncytium-inducing (SI) primary isolates. Persistently infected U1 cells, which can be induced to increase HIV-1 mRNA synthesis on addition of PMA or TNF-alpha, showed decreased production of HIV-1 in the presence of sFvtat1Ck. In transduced CD4+-selected, CD8+-depleted, and total PMBCs, the sFvtat1Ck-expressing cells showed marked inhibition of HIV-1 replication. The anti-Tat sFv was subsequently humanized by substituting compatible human framework regions that were chosen from a large database of human V(H) and V(L) sequences on the basis of high overall framework matching, similar CDR length, and minimal mismatching of canonical and V(H)/V(L) contact residues. One humanized anti-Tat sFv intrabody, termed sFvhutat2, demonstrated a level of anti-HIV-1 activity that was comparable to the parental murine sFv when transduced PBMCs expressing the murine or humanized sFv intrabodies were challenged with HxB2 and two SI primary isolates. Because Tat is likely to have both direct and indirect effects in the pathogenesis of AIDS through its multiple roles in the HIV-1 life cycle and through its effects on the immune system, the strategy of genetically blocking Tat protein function with a humanized anti-Tat sFv intrabody may prove useful for the treatment of HIV-1 infection and AIDS, particularly when used as an adjuvant gene therapy together with highly active antiretroviral therapies that are currently available.

VEGFs, receptors and angiogenesis

Angiogenesis, the formation of new blood vessels from pre--existing ones, is central for both normal development and homeostasis as well as in certain pathological conditions. The vascular endothelial growth factors (VEGFs) and their receptors are prime regulators of both physiological and pathological angiogenesis. The different VEGFs have overlapping but specific roles in controlling the growth of new blood vessels. The VEGF receptors transduce signals mediating endothelial cell proliferation, migration, organization into functional vessels and remodeling of the vessel network. In recent years, rapid progress has been made in understanding the receptor-ligand interactions that orchestrate the neovascularization process.

Thrombospondin-1 inhibits Kaposi's sarcoma (KS) cell and HIV-1 Tat-induced angiogenesis and is poorly expressed in KS lesions

Kaposi's sarcoma (KS), a neoplasm often associated with iatrogenic and acquired immunosuppression, is characterized by prominent angiogenesis. Angiogenic factors released by both KS and host cells, as well as HHV-8 and HIV viral products, have been implicated in the pathogenesis of this lesion. Angiogenesis is the result of imbalance among angiogenesis promoters and inhibitors, which disrupts homeostasis. The aim of this study was to investigate the expression and mechanism of KS control of thrombospondin-1 (TSP), a physiological inhibitor of angiogenesis. Immunohistochemical analysis of four KS lesions showed only spotty reactivity for TSP in the stroma and in less than 10 per cent of lesional blood vessels. In addition, the typical KS spindle cells were not stained. In agreement with these findings, decreased levels of TSP were measured with an ELISA assay in the supernatants of cultured KS cells, compared with endothelial cells. In vitro, TSP inhibited the endothelial cell proliferation and motility induced by KS cell supernatants. TSP also prevented endothelial cell motility induced by Tat, a product of HIV-1 endowed with angiogenic potential and implicated in the pathogenesis of AIDS-KS. In vivo, TSP inhibited the angiogenic activity exerted by Tat in the Matrigel sponge model. These results suggest that TSP down-regulation might be permissive for the development of KS-associated angiogenesis.

Morphological, histochemical, immunohistochemical, and ultrastructural characterization of tumors and dysplastic and non-neoplastic lesions arising in BK virus/tat transgenic mice

To study the role in AIDS pathogenesis of the human immunodeficiency virus type 1 (HIV-1) Tat protein, a transactivator of viral and cellular genes, we generated transgenic mice with a recombinant DNA containing BK virus (BKV) early region and the HIV-1 tat gene, directed by its own promoter-enhancer. DNA hybridization revealed that the transgene is stably maintained in all organs of transgenic mice as a tandem insertion in a number of copies ranging from 5 to 20 per cell. In addition, tat and BKV RNA were expressed in all tissues. Transgenic mice developed three types of lesions: 1) tumors, 2) hyperplastic and dysplastic lesions, and 3) non-neoplastic lesions. Tumors of different histotypes, such as lymphomas, adenocarcinomas of skin glands, leiomyosarcomas, skin squamous cell carcinomas, hepatomas, hepatocarcinomas, and cavernous liver hemangiomas, developed in 29% of transgenic animals. The majority of tumors were malignant, invasive, and producing metastases. Conversely, tumors of only two histotypes (lymphomas and adenocarcinomas of skin glands) appeared in control mice. Hyperplastic and dysplastic lesions were more frequent in transgenic than in control mice and involved the skin or its adnexes, the liver and the rectum, indicating multiple targets for the activity of the transgene. Pyelonephritis, frequently complicated with hydronephrosis, inflammatory eye lesions, and amyloid depositions represented the most frequent non-neoplastic lesions detected in transgenic mice. Many of the pathological findings observed in this animal model are comparable to similar lesions appearing in AIDS patients, suggesting a relevant role for Tat in the pathogenesis of such lesions during the course of AIDS.

Kaposi's sarcoma in women: A clinicopathologic study

BACKGROUND

Although all epidemiologic subsets of Kaposi's sarcoma (KS) (i.e., sporadic, endemic, epidemic, and iatrogenic) have an association with human herpes virus 8 (HHV8), these subsets occur in patient populations with distinctive clinical features. To a variable degree men outnumber women in all subsets.

OBJECTIVE

A retrospective study of women with histologically proven cutaneous KS was undertaken to determine the clinical and histopathologic features, as well as any associations.

METHODS

Two hundred and fifty cases of cutaneous KS in women from 1975 to 1993 were reviewed.

RESULTS

Of the patients, 80% were more than 60 years of age, and of the patients less than 60 years old, 28 were from areas of the world with endemic KS. All HIV+ patients but one were from areas of endemic KS. Two patients were renal transplant patients. Sixty-four percent of the patients had single lesions and 21% recurrent lesions. Twelve patients had, or were known to develop, internal involvement, and in six patients the cause of death was KS. All but four cases histologically showed areas of solid proliferations of tumour cells consistent with plaque or tumour stage. An angiosarcoma-like histologic pattern appeared to be associated with more aggressive epidemiologic subsets. High mitotic rates were rarely seen and did not correlate with aggressive epidemiologic subsets.

CONCLUSION

Kaposi's sarcoma in women is diagnosed almost exclusively in plaque or tumour stage. The majority of women within our study fit within the epidemiologic subset of sporadic KS.

Characterization of the effects of two polysulfonated distamycin A derivatives, PNU145156E and PNU153429, on HIV type 1 Tat protein

We examined whether two sulfonated distamycin A derivatives, PNU145156E and PNU153529, inhibit the trans-activating and angiogenic effects of HIV-1 Tat protein. The study was carried out by analyzing the activity of the two drugs on: (1) extracellular and intracellular Tat protein, introduced into HL3T1 cells containing an integrated HIV-1 LTR/CAT plasmid; (2) binding of Tat to 3H-labeled heparin and to 14C-labeled PNU145156E; and (3) the angiogenic response induced in vivo by culture medium conditioned by T53c14 cells, which release extracellular Tat. PNU145156E and PNU153429 interacted with extracellular Tat in the culture medium and physically bound the Tat protein, most likely sequestering it in the extracellular space. As a consequence, the two drugs inhibited trans-activation of the HIV-1 LTR on addition of the free Tat protein to HL3T1 cells. However, the two compounds inhibited the activity of intracellular Tat when they were introduced into the cells by lipofection. In vivo experiments showed that the two drugs blocked the neoangiogenesis induced by Tat released in the conditioned medium of T53c14 cells. Owing to the critical role of intracellular and extracellular Tat in HIV-1 replication, these drugs show promise as a means to control the progression of HIV-1 infection as well as the neoplastic and angiogenic effects induced by Tat in the course of AIDS.

EDF-1, a novel gene product down-regulated in human endothelial cell differentiation

Endothelial cell differentiation is a crucial step in angiogenesis. Here we report the identification of EDF-1, a novel gene product that is down-regulated when endothelial cells are induced to differentiate in vitro. The cDNA encoding EDF-1 was isolated by RNA fingerprinting from human endothelial cells exposed to human immunodeficiency virus type 1 Tat, a viral protein known to be angiogenic. The deduced amino acid sequence of EDF-1 encodes a basic intracellular protein of 148 amino acids that is homologous to MBF1 (multiprotein-bridging factor 1) of the silkworm Bombyx mori and to H7, which is implicated in the early developmental events of Dictyostelium discoideum. Interestingly, human immunodeficiency virus type 1 Tat, which affects endothelial functions, and the phorbol ester 12-O-tetradecanoylphorbol-13-acetate and culture on fibrin gels, which promote endothelial differentiation in vitro, all down-regulate EDF-1 expression both at the RNA and protein levels. In addition, the inhibition of EDF-1 translation by an antisense anti-EDF-1 construct results in the inhibition of endothelial cell growth and in the transition from a nonpolar cobblestone phenotype to a polar fibroblast-like phenotype. These data suggest that EDF-1 may play a role in the regulation of human endothelial cell differentiation.

Purified Tat induces inflammatory response genes in Kaposi's sarcoma cells

OBJECTIVE

Kaposi's sarcoma (KS) is a neoplasm strongly associated with HIV-1 infection and marked by leukocytic infiltration. The infiltrating leukocytes are a possible source of inflammatory cytokines, human herpesvirus 8 (HHV8) and the HIV-1 transactivator protein Tat. This study examines whether Tat directly induces expression of cellular adhesion molecules and cytokines in KS cells and whether this induction differs in kinetics and magnitude from induction by tumour necrosis factor (TNF) alpha.

DESIGN AND METHOD

Changes in gene expression in response to recombinant Tat compared with those to TNFalpha were evaluated at the messenger (m) RNA and protein level using cells that were cultured from KS lesions.

RESULTS

Tat induced the expression of the adhesion molecules vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1) and the cytokines monocyte chemoattractant protein 1 (MCP-1) and interleukin 6 (IL-6). The inductions were observed at both the protein and mRNA levels. The pattern of mRNA induction over time in response to Tat differed from that to TNFalpha, with higher peak levels that occurred earlier in response to Tat. The expression of these genes is, in part, regulated by the transcription factor NF-kappaB. Tat and TNFalpha activated comparable levels of NF-kappaB.

CONCLUSIONS

The ability of the HIV-1 Tat to induce the expression of genes with kinetics that are distinct from those seen in TNFalpha induction suggests that mechanisms in addition to activation of NF-kappaB contribute to the observed induction. Tat may contribute to the pathogenesis of AIDS-related KS through induction of cellular genes that are pro-proliferative and proinflammatory and may enhance the recruitment of leukocytes, which are a possible source of further cytokines, Tat and HHV8.

Update on cutaneous manifestations of HIV infection

The skin is affected in virtually all patients with HIV infection. Many articles and several books have been published that deal with these disorders for a number of reasons. First, cutaneous disease may serve as the initial or only problem that the patient suffers for much of the course of the HIV infection. Second, serious opportunistic infections may present for the first time in the skin, so that a skin lesion may be a harbinger of the patient's having a life-threatening illness. Third, skin disorders in these patients may appear unusual and hence may not be accurately diagnosed by clinical inspection alone. Furthermore, response to treatment may be poorer than expected. Thus, skin diseases in the HIV-infected patient are important and, in some cases, may be the most debilitating element of the patient's condition.

HLA-Cw*0602 and HIV-associated psoriasis

The aetiopathogenesis of psoriasis is unknown, but genetic and environmental factors may be involved. Psoriasis may not be one disease but a cutaneous inflammatory reaction pattern consequent upon several different independent or related stimuli in susceptible individuals. There are controversial issues regarding the immunological basis of psoriasis and the role of CD4 vs. CD8 T lymphocytes. Psoriasis has been associated with HLA-Cw6 and Cw7 by serology and specifically with HLA-Cw*0602 by polymerase chain reaction (PCR) typing. Psoriasis is probably no more common in HIV infection than in the general population; however, it may appear for the first time or pre-existing psoriasis may worsen and be difficult to treat in HIV disease. We have investigated the prevalence of HLA-C alleles, in the specific clinical context of HIV infection complicated by type 1 psoriasis, in a case control study of 14 men with HIV disease and type 1 psoriasis and 147 HIV-infected patients without psoriasis. Typing was performed using PCR with sequence-specific amplification primers. Eleven of 14 patients (79%) with psoriasis carried the HLA-Cw*0602 allele compared with 24.5% of those without psoriasis (odds ratio = 11.31; 95% confidence limits 2. 73 to 65.36; P = 0.0001). Two patients without the HLA-Cw*0602 allele carried instead the closely related Cw*0401/3 allele. The results confirm the previously reported association between the HLA-Cw*0602 allele and type 1 psoriasis, and suggest that the association with HLA-Cw*0602 is stronger in HIV-associated psoriasis although this trend needs to be supported by a larger sample. The immunodysregulation resulting from HIV infection may trigger psoriasis in those genetically predisposed by the Cw*0602 allele. As CD8 T cells recognize antigens in the context of class I major histocompatibility complex, the identification of an HLA class I association in HIV-associated psoriasis strengthens the argument for an important role for CD8 + T lymphocytes in the immunopathogenesis of psoriasis. Investigations of the pathogenesis of psoriasis should take account of clinical and other subtypes already identified.

Kaposi's sarcoma-associated herpesvirus

Kaposi's sarcoma (KS) is a vascular tumor predominantly found in the immunosuppressed. Epidemiologic studies suggest that an infective agent is the etiologic culprit. Kaposi's sarcoma-associated herpesvirus (KSHV), or human herpesvirus-8 (HHV-8), is a gamma human herpesvirus present in all epidemiologic forms of KS and also in a rare type of a B cell lymphoma, primary effusion lymphoma (PEL). In addition, this virus is present in most biopsies from human immunodeficiency virus (HIV)-associated multicentric Castleman's disease (MCD). MCD is a lymphoproliferative disorder with, like KS, a prominent microvasculature. The genome of KSHV contains the expected open reading frames (ORFs) encoding for enzymes and viral structural proteins found in other herpesviruses, but it also contains an unprecedented number of ORFs pirated during viral evolution from cellular genes. These include proteins that may alter cellular growth (e.g., Bcl-2 and cyclin homologs), induce angiogenesis (e.g., chemokine, chemokine receptor, and cytokine homologs), and regulate antiviral immunity (e.g., CD21 and interferon regulatory factor homologs). No ORF with sequence similarity to the Epstein-Barr nuclear antigens (EBNAs) and latent membrane proteins (LMPs) of Epstein-Barr virus (EBV) is present, but proteins analogous to these in structure and in latent expression are found [e.g., ORF 73 encoding for KSHV latent nuclear antigen (LNA-1) and K12 encoding for a possible latent membrane protein]. Current serologic assays confirm the strong association of infection with KSHV and risk of KS development. The mechanism of how this new virus may trigger the precipitation of KS is still unclear.

FGF-2 stimulates migration of Kaposi's sarcoma-like vascular cells by HGF-dependent relocalization of the urokinase receptor

The spindle-shaped cell line TTB was recently isolated from highly vascularized skin lesions of BKV/HIV-1 tat transgenic mice and shown to possess an autocrine loop for hepatocyte growth factor (HGF). We show that fibroblast growth factor-2 (FGF-2) stimulates TTB cell migration and promotes polarization of uPAR at the leading edge of migrating cells. FGF-stimulated TTB cells presented the typical migratory phenotype, with a triangular cell shape and concomitant breakdown of actin stress fibers and smooth muscle-specific actin isoform. FGF-2-stimulated migration was blocked by antibodies against urokinase-type plasminogen activator (uPA) or uPA receptor (uPAR) and by neutralizing anti-HGF antibodies. The latter also inhibited uPAR relocalization at the cell surface of FGF-2-treated TTB cells. This points to a crosstalk between FGF-2 and HGF that might mediate TTB cell migration by modulating the localization of cell surface uPAR.

The basic domain in HIV-1 Tat protein as a target for polysulfonated heparin-mimicking extracellular Tat antagonists

Heparin binds extracellular HIV-1 Tat protein and modulates its HIV long terminal repeat (LTR)-transactivating activity (M. Rusnati, D. Coltrini, P. Oreste, G. Zoppetti, A. Albini, D. Noonan, F. d'Adda di Fagagna, M. Giacca, and M. Presta (1997) J. Biol. Chem. 272, 11313-11320). On this basis, the glutathione S-transferase (GST)-TatR49/52/53/55/56/57A mutant, in which six arginine residues within the basic domain of Tat were mutagenized to alanine residues, was compared with GST-Tat for its capacity to bind immobilized heparin. Dissociation of the GST-TatR49/52/53/55/56/57A.heparin complex occurred at ionic strength significantly lower than that required to dissociate the GST-Tat.heparin complex. Accordingly, heparin binds immobilized GST-Tat and GST-TatR49/52/53/55/56/57A with a dissociation constant equal to 0.3 and 1.0 microM, respectively. Also, the synthetic basic domain Tat-(41-60) competes with GST-Tat for heparin binding. Suramin inhibits [3H]heparin/Tat interaction, 125I-GST-Tat internalization, and the LTR-transactivating activity of extracellular Tat in HL3T1 cells and prevents 125I-GST-Tat binding and cell proliferation in Tat-overexpressing T53 cells. The suramin derivative 14C-PNU 145156E binds immobilized GST-Tat with a dissociation constant 5 times higher than heparin and is unable to bind GST-TatR49/52/53/55/56/57A. Although heparin was an antagonist more potent than suramin, modifications of the backbone structure in selected suramin derivatives originated Tat antagonists whose potency was close to that shown by heparin. In conclusion, suramin derivatives bind the basic domain of Tat, prevent Tat/heparin and Tat/cell surface interactions, and inhibit the biological activity of extracellular Tat. Our data demonstrate that tailored polysulfonated compounds represent potent extracellular Tat inhibitors of possible therapeutic value.

Preclinical characterization of an anti-tat ribozyme for therapeutic application

A hammerhead ribozyme retroviral construct, denoted RRz2, targeting the coding region of the human immunodeficiency virus type 1 (HIV-1) tat gene, has shown itself to be effective in a range of test systems. Inhibition of the replication of HIV-1 IIIB and primary drug-resistant strains in pooled transduced CEMT4 cells was consistently found to be more than 80% compared with the control-vector transduced cells, whereas a mutant RRz2 gave approximately 45% inhibition. A multiple HIV-1 passage assay showed the absence of emergence of mutations within the specific viral RNA ribozyme target sequences. This lack of generation of ribozyme "escape mutants" occurred despite the almost complete disappearance of a HIV-1 quasi-species in the testing virus. When RRz2 was tested in peripheral blood lymphocytes (PBLs) from HIV-1-infected patients, paired analysis showed that cell viability in the ribozyme-transduced HIV-1-infected PBLs was significantly higher than that in the vector-transduced cells. This difference in viability (vector versus RRz2) was not observed in PBLs from non-HIV-1-infected donors. Taken together, these results indicate that the transfer of an anti-HIV-1 ribozyme gene into human T lymphocytes could have major impact on viral replication and T cell viability in the HIV-1-infected individual.

Evidence that both HIV and HIV-induced immunodeficiency enhance HCV replication among HCV seroconverters

The objective of this retrospective cohort study is to assess the mechanism by which human immunodeficiency virus type 1 (HIV) influences hepatitis C virus (HCV) replication in injecting drug users. Virological (HCV and HIV RNA levels) and immunological (CD4+, CD8+ cell counts, and anti-CD3 reactivity) parameters were determined in 19 HCV seroconverters in sequential samples over a period of 1 to 9 years. Among these subjects, 10 were HIV-seronegative (HIVneg), 4 were HIV-seropositive (HIVpos), and 5 seroconverted for HIV (HIVsc) during the observation period. HCV RNA levels were higher in HIVpos subjects than in HIVneg subjects. In subjects seroconverting for HIV, HCV, RNA levels increased significantly immediately after HIV seroconversion (P < 0.0001), while they remained stable over time in HIVpos and HIVneg subjects. HCV RNA correlated inversely with CD4+ cell counts in both the HIVpos population (R = -0.22, P < 0.05) and the HIVneg population (R = -0.45, P < 0.0001). In addition, when subjects were stratified according to CD4+ cell counts a significant difference was found in HCV RNA levels between HIVpos and HIVneg subjects with CD4+ cell counts > 500 cells/microliter (P = 0.001), but not in the population with CD4+ cell counts < 500 cells/microliter. In no population was a correlation found between HCV RNA levels and CD8+ cell counts or anti-CD3 reactivity. Both HIV infection and CD4+ cell counts are apparently associated with HCV RNA levels. The direct association, independent of CD4+ cell counts, between HIV infection and HCV replication appears to be stronger than the association between HIV-induced CD4+ cell decline and HCV replication. We conclude that (i) HCV replication is in some way directly influenced by the presence of HIV; (ii) HCV-specific host immunity controls, in part, HCV replication; and (iii) HCV replication increases when the immune system is impaired by HIV.

HIV infection-associated inflammatory musculoskeletal disorders

Inflammatory musculoskeletal complaints are relatively common during the course of HIV infection, although they tend to be more frequent during late stages. The clinical spectrum is varied, ranging from arthralgias to distinct rheumatic disorders, such as Reiter's syndrome and psoriatic arthritis. The therapeutic management often poses a challenge, although most patients respond to conventional first- and second-line anti-inflammatory medications.

Glutathione depletion associated with the HIV-1 TAT protein mediates the extracellular appearance of acidic fibroblast growth factor

Primary murine embryonic fibroblasts transfected with HIV-1 TAT demonstrated decreased levels of high energy phosphates (ATP, GTP, UTP/CTP), adenine nucleotides (ATP, ADP, AMP), and both NAD+/NADH redox pairs, resulting in a substantial loss of redox poise. A greater than 50% decrease in intracellular reduced glutathione (GSH) concentration was accompanied by the extracellular appearance of acidic fibroblast growth factor (FGF-1). Addition of either N-acetyl-L-cysteine or glutathione ester (GSE), but not L-2-oxothiazolidine 4-carboxylate, partially restored intracellular GSH levels and resulted in loss of extracellular FGF-1. Treatment of FGF-1-transduced cells with buthionine sulfoximine (BSO) resulted in a time- and dose-dependent decrease in total cellular GSH concentration that was accompanied by the extracellular appearance of FGF-1. Inclusion of GSE during BSO treatment eliminated the extracellular appearance of FGF-1. BSO treatment of cells transfected with a mutant form of FGF-1, in which all three cysteine residues were replaced with serines, also decreased total cellular GSH concentration but failed to induce the extracellular appearance of FGF-1. Collectively, these results suggest that HIV-1 TAT induces a condition of oxidative stress, which mediates cellular secretion of FGF-1, an observation relevant to the pathophysiologic development and progression of AIDS-associated Kaposi's sarcoma.

Kaposi's sarcoma: a result of the interplay among inflammatory cytokines, angiogenic factors and viral agents

Kaposi's sarcoma (KS) is an angioproliferative disease occurring in 4 clinic-epidemiologic forms. Although the AIDS-associated KS (AIDS-KS) is the most aggressive, all forms of KS share the same immunological and histopathological features suggesting common etiological and pathogenic factors. Recent data indicate that at least in early stage KS is not a real sarcoma but an angiohyperplastic-inflammatory lesion mediated by inflammatory cytokines and angiogenic factors, that is triggered or amplified by infection with human herpesvirus-8. In addition, the human immunodeficiency virus type-1 Tat protein appears to be responsible for the higher grade of aggressiveness of AIDS-KS as compared to the other forms of KS. However, given time, reactive KS may progress to a sarcoma as suggested by evidence of monoclonality in late-nodular lesions.

beta Interferon inhibits HIV-1 Tat-induced angiogenesis: synergism with 13-cis retinoic acid

Kaposi's sarcoma (KS) is a highly angiogenic lesion which frequently presents as an aggressive form in HIV-infected male patients. We have previously shown that the HIV-1 Tat protein induces endothelial cell migration and invasion in vitro and a rapid angiogenic response in vivo, suggesting that it acts as a cofactor in epidemic KS. In this study we tested beta interferon (IFN beta) and retinoic acid (RA) for the inhibition of Tat-induced angiogenesis using in vivo and in vitro models. IFN beta, at a concentration above 2500 U/ml, was an effective inhibitor of Tat-stimulated growth, migration and morphogenesis of an endothelial cell line in vitro and of angiogenesis in vivo. A strong reduction of properties associated with neovascularisation was induced by 10,000 U/ml. In vivo, RA alone was on ineffective inhibitor of angiogenesis, and in vitro gave only a limited inhibition of endothelial cell growth. However, 13-cis RA used in combination with IFN beta impressively potentiated its effects. A combination of lower doses of IFN beta (2500 U/ml) and 13-cis RA induced a virtually complete inhibition of the Tat-related angiogenic phenotype both in vivo and in vitro. The potentiation of the anti-angiogenic activity of IFN beta by 13-cis RA suggests that this combination could be a useful approach for the therapy of epidemic KS.

Transgenic mice expressing human immunodeficiency virus type 1 in immune cells develop a severe AIDS-like disease

We have constructed transgenic (Tg) mice expressing the entire human immunodeficiency virus type 1 (HIV-1) coding sequences in cells targeted by HIV-1 infection in humans. These Tg mice developed a severe AIDS-like disease leading to early death (< 1 month). They developed muscle wasting, severe atrophy and fibrosis of lymphoid organs, tubulointerstitial nephritis, and lymphoid interstitial pneumonitis. In addition the expression of RANTES was increased in various tissues of these Tg mice relative to that in the normal controls. Disease appearance was correlated with the levels of transgene expression. The numerous pathologies observed in these mice are remarkably similar to those observed in human AIDS and, more specifically, in pediatric AIDS.

Human immunodeficiency virus infection and pulmonary hypertension: two new cases and a review of 86 reported cases

In this article, we describe pulmonary hypertension in two men (31 and 43 years of age) with human immunodeficiency virus (HIV) infection who were examined at Mayo Clinic Rochester. Among 88 reported cases (including the two current ones) of HIV- or acquired immunodeficiency syndrome (AIDS)-associated pulmonary hypertension, 61% were male; the age range was 2 to 56 years (mean, 32). Dyspnea was the usual initial symptom. Of the 74 patients in whom pulmonary artery pressure was recorded or calculated by echocardiography, systolic pressures ranged from 49 to 118 mm Hg (mean, 68). Of the 33 cases in which lung tissue was evaluated microscopically, 28 (85%) were of the plexogenic variant of pulmonary arterial hypertension. Of the other five cases examined histologically, three consisted of thrombotic pulmonary arteriopathy (one was due to recurrent thromboembolism, and the other two were due to in situ thrombosis), and two were of pulmonary venoocclusive disease. No correlation existed between either CD4 counts or a history of pulmonary infections and the development of pulmonary hypertension. In 15 of the 88 patients (17%), confounding factors for hypertensive pulmonary vascular disease were present, including coexisting liver disease in 13 and coagulation abnormalities in 2. In 83% of the patients, the development of pulmonary hypertension seems to have been related primarily to the chronic HIV infection. Pulmonary hypertension was more rapidly progressive in patients with HIV or AIDS than in those with primary pulmonary hypertension; the reported time intervals between onset of symptoms and diagnosis were 6 months and 30 months, respectively. The 1-year survival rate for patients with HIV and pulmonary hypertension was 51%, based on the follow-up data compiled from the 63 patients in whom it was described; this compares with a 1-year survival rate of 68% for patients with primary pulmonary hypertension. Death was considered a direct consequence of pulmonary hypertension in 29 (76%) of the 38 fatal cases.

Aetiology of Kaposi's sarcoma: current understanding and implications for therapy

Kaposi's sarcoma is an angiogenic neoplasm composed of endothelial and spindle cells. The enormous increase in Kaposi's sarcoma with HIV infection, and recent discovery that a new human herpesvirus (Kaposi's sarcoma-associated herpesvirus, also called human herpesvirus 8) is present in this tumor, has activated intense interest in the aetiology, epidemiology and pathogenesis of this disease. Today, Kaposi's sarcoma is one of the most frequent neoplasms in men under 50 years old in the USA, and in some African countries it is the most common tumour overall.

Fibronectin modulates endothelial response to HIV type 1 Tat

The normal function of the endothelium is impaired in HIV-1 infection. Disturbances of the local cytokines as well as the release of HIV-1 Tat by infected mononuclear cells play a role in endothelial dysfunction. We studied the effects of Tat on the human endothelial ECV cell line. In this system, Tat inhibited cell proliferation only in the presence of fibronectin as a culture substrate, whereas it did not modulate plasminogen activator activity, cell migration, or synthesis of fibronectin. Because amino acids 49-57 contains a nuclear translocation sequence, we also evaluated the potential intracellular role of Tat in tat-transfected ECV cells. tat transfectants showed inhibition of cell growth, unaffected cell migration and plasminogen activator activity, and a significant induction of the expression of fibronectin.

HIV-1 Tat protein exits from cells via a leaderless secretory pathway and binds to extracellular matrix-associated heparan sulfate proteoglycans through its basic region

OBJECTIVE

To analyze the mechanisms of release and the extracellular fate of the HIV-1 Tat protein and to determine the Tat domain binding to the extracellular matrix.

DESIGN AND METHODS

Release of Tat was studied by pulse-chase experiments with Tat-transfected COS-1 cells in the presence or absence of different serum concentrations, temperatures and drugs inhibiting the classical secretion pathway or endo-exocytosis, such as brefeldin A and methylamine. The binding of extracellular Tat to heparan sulfate proteoglycans (HSPG) was determined by using trypsin, heparin or heparinase in pulse-chase experiments, by gel shift and competition assays with radiolabeled heparin, and by heparin-affinity chromatography. The mapping of the Tat binding site to heparin was defined by functional assays of rescue of Tat-defective HIV-1 proviruses.

RESULTS

Tat is released in the absence of cell death or permeability changes. Tat release is dependent upon the temperature and serum concentration, and it is not blocked by brefeldin A or methylamine. After release, a portion of the protein remains in a soluble form whereas the other binds to extracellular matrix (ECM)-associated HSPG. The HSPG-bound Tat can be retrieved into a soluble form by heparin, heparinase or trypsin. Binding to heparin is competed out by heparin-binding factors such as basic fibroblast growth factor (bFGF), and it is mediated by the Tat basic region which forms a specific complex with heparin which blocks HIV-1 rescue by exogenous Tat and allows purification of a highly biologically active protein.

CONCLUSIONS

These results demonstrate that Tat exits from intact cells through a leaderless secretion pathway which shares several features with that of acid FGF or bFGF. The released Tat binds to HSPG through its basic region and this determines its storage into the ECM, as occurs for bFGF.

HIV-related psoriasis and Reiter's syndrome

Infection with the human immunodeficiency virus (HIV) is associated with the development of psoriasis and related disorders, including psoriatic arthritis, dactylitis and enthesitis, and Reiter's syndrome. The etiologic mechanisms remain unclear but most likely represent a combination of genetic and environmental factors. Therapy for these diseases in the setting of HIV infection is often difficult not only because of their characteristically increased severity, but also because the use of conventionally effective immunosuppressive agents may be counterproductive in this patient population.

Primary pulmonary hypertension and human immunodeficiency virus infection

This report details the case of a 42-year-old homosexual Caucasian male with infection due to human immunodeficiency virus type 1 (HIV-1) who presented with a four-month history of progressive dyspnea and was found to have clinical and hemodynamic evidence of severe pulmonary hypertension. He had had no opportunistic infections, and had a T helper lymphocyte count of 200×10(6)/L. Extensive clinical laboratory and radiological evaluations revealed no underlying cause. Microscopic examination of postmortem lung tissue revealed findings consistent with grade V pulmonary hypertension. Electron microscopic analysis and polyermase chain reaction detection of HIV-DNA from dissected pulmonary arterioles failed to provide any supportive evidence to suggest productive infection of the pulmonary arteriolar endothelial cells by HIV-1. Although HIV-1 likely plays a role in the pathogenesis of primary pulmonary hypertension, evidence for direct infection of pulmonary vessel endothelium was lacking in this case. The pathogenesis of primary pulmonary hypertension associated with HIV remains obscure.

Expression and mutation of the tumor suppressor gene p53 in AIDS-associated Kaposi's sarcoma

Alteration of the p53 gene is the most frequent event reported in human cancer, and p53 mutations have been observed in various neoplasms, including certain forms of skin cancer. Therefore, we postulated that p53 may also be involved in Kaposi's sarcoma associated with AIDS (AIDS-KS). Expression of the p53 gene was examined in freshly isolated tumor biopsy specimens from 15 patients with AIDS-KS. p53 mRNA was detected by reverse transcriptase-polymerase chain reaction (RT-PCR) in both the AIDS-KS tumors and in normal skin control samples. p53 protein was detected in 4 of the 15 AIDS-KS specimens by immunohistochemical staining. Single-strand conformation polymorphism analysis PCR-products (PCR-SSCP) was used for detection of mutations of the p53 gene. One of the p53 positive AIDS-KS samples showed mobilized shifts in exon 6 suggestive of a mutation. Sequencing data showed the mutation to be located in codon 210. We examined other mechanisms that could stabilize p53 protein. SV40 large T antigen and adenovirus E1B protein were not found in the AIDS-KS specimens. MDM2, a p53-binding protein, was also detected in five of the AIDS-KS specimens, two of which also contained p53-positive cells. These observations suggest that the tumor suppressor gene p53 may be involved in the pathogenesis of AIDS-KS.

Upregulation of urokinase-type plasminogen activator by endogenous and exogenous HIV-1 Tat protein in tumour cell lines derived from BK virus/tat-transgenic mice

OBJECTIVE

To demonstrate that Tat modulates the plasminogen-dependent proteolytic activity of tumour cell lines derived from BK virus (BKV)/tat-transgenic mice by affecting the production of plasminogen activators (PA) and the PA inhibitor (PAI)-1 and to demonstrate that this occurs through mechanism(s) that are distinct from those responsible for transactivating activity of extracellular Tat.

DESIGN AND METHODS

To assess whether endogenous Tat is responsible for PA activity in T53 adenocarcinoma cells, cell cultures were transfected with antisense Tat cDNA and evaluated for cell-associated PA activity by a plasmin chromogenic assay. The assay was also used to evaluate PA activity in T53 cells and T111 leiomyosarcoma cells stimulated by extracellular Tat. The type(s) of PA produced were identified by sodium dodecyl sulphate-polyacrylamide gel electrophoresis zymography. The levels of PAI-1 were evaluated by Western blotting. Tat transactivating activity was measured by a chloramphenicol acetyltransferase (CAT) enzyme-linked immunosorbent assay in HL3T1 cells containing integrated copies of an HIV-1 long terminal repeat (LTR)-CAT plasmid.

RESULTS

Transfection of T53 cells with antisense Tat cDNA results in the decrease of Tat production and PA activity. Exogenously added Tat increases PA levels in T53 and in T111 cells. PA activity was identified as urokinase-type PA (uPA). Tat also increases the production of PAI-1 in T111 but not in T53 cells. Chloroquine and heparin have different affects on the LTR-CAT-transactivating and the PA-inducing activities of Tat. The fusion protein glutathione-S-transferase-Tat and the mutant Tat-1e, lacking the second Tat exon, cause LTR-CAT transactivation without stimulating uPA upregulation.

CONCLUSIONS

Tat affects the fibrinolytic activity of tumour cell lines derived from BKV/tat-transgenic mice by modulating the production of both uPA and PAI-1 via autocrine and paracrine mechanisms of action. The capacity of Tat to modulate the plasminogen-dependent proteolytic activity of these tumour cell lines may contribute to their metastatic potential. The uPA-inducing activity of Tat depends upon specific biological and structural features of the Tat protein that are distinct from those responsible for its LTR-CAT-transactivating activity, suggesting distinct mechanisms of induction for the two biological responses.

Acquired immunodeficiency syndrome-associated Kaposi's sarcoma. Biology and management

Kaposi's Sarcoma (KS), the most common AIDS-associated malignancy, occurs with increased frequency in all HIV transmission groups, but at a particularly high rate in homosexual men. Recent studies suggest that KS pathogenesis involves exposure to an infectious agent, altered expression and response to cytokines, and modulation of growth by HIV gene products. KS varies in its clinical presentation from a relatively indolent process to a widely disseminated, aggressive disease. A variety of local and systemic treatments provide effective, but usually temporary, disease palliation. Insights into KS pathogenesis suggest a number of targeted therapeutic approaches that may eventually lead to improved disease management and disease cure.

Population pharmacokinetics and pharmacodynamics of pegylated-liposomal doxorubicin in patients with AIDS-related Kaposi's sarcoma

OBJECTIVE

To characterize the population pharmacokinetics of pegylated-liposomal doxorubicin in patients with acquired immunodeficiency disease (AIDS)-related Kaposi's sarcoma and to explore the relationship between response of the cutaneous Kaposi's sarcoma lesions to treatment and measures of drug exposure.

METHODS

Forty-three male patients (median age, 40 years; age range, 28 to 50 years), body surface area, 1.89 m2; range, 1.5 to 2.3 m2) with AIDS and at least five biopsy-proven cutaneous Kaposi's sarcoma lesions were randomized to receive either a 10 or 20 mg/m2 dose of study drug for their first cycle and the alternate dose 3 weeks later. Patients continued to receive the study drug at a dose of 20 mg/m2 every 3 weeks. Serial blood samples were obtained after the first two doses and analyzed by HPLC for determination of total plasma doxorubicin concentration. Kaposi's sarcoma lesion response was categorized as either progressive disease, stable disease, partial response, or complete response. Classification and regression tree (CART) analysis was used to determine the relationship between drug exposure and categorical lesion response. Iterative two-stage analysis was used to characterize both the pharmacokinetics of pegylated-liposomal doxorubicin and to model the probabilities of achieving a specific lesion response.

RESULTS

The pharmacokinetics of pegylated-liposomal doxorubicin were best described by a two-compartment linear structural model. Lesion response was significantly related to both the average daily maximum doxorubicin concentration (Cmax,avg) and dose intensity.

CONCLUSIONS

The pharmacokinetics of pegylated-liposomal doxorubicin are strikingly different from conventional doxorubicin. Identification of both Cmax,avg and dose intensity as predictors of lesion response will provide guidelines for future dosing regimen designs.

Glucocorticoids Induce Kaposi's Sarcoma Cell Proliferation Through the Regulation of Transforming Growth Factor-β

Glucocorticoid (GC) use is known to induce or enhance the growth of Kaposi's sarcoma (KS) in many clinical settings including human immunodeficiency virus infection, collagen vascular disease, lymphoproliferative disorders, and renal transplantation. Because GCs may induce immune suppression and thus tumor growth, we determined whether GCs had a direct effect on KS growth. We found that GCs directly induce the growth of KS cell lines. In examining the mechanism of action of GCs, we did not observe induction of known autocrine growth factors for KS including interleukin-1 (IL-1), IL-6, oncostatin-M, basic fibroblast growth factor (bFGF ), and vascular endothelial growth factor (VEGF ). We thus examined factor(s) that inhibit KS growth. Transforming growth factor-β (TGF-β) is produced by KS cells and has pleiotropic effects, including inhibiting the growth of hematopoietic and endothelial cells. We show that TGF-β is produced by KS cells in both the latent and active forms, and that TGF-β is an autocrine growth inhibitory factor. We then studied the effects of GCs on the regulation of TGF-β and found that GCs do not inhibit TGF-β transcription, but significantly inhibit TGF-β activation. This effect is mediated through regulation of the TGF-β activation pathway. TGF-β is activated by plasmin which is positively regulated by plasminogen activator (PA) and PA receptor (PAR), and negatively regulated by plasminogen activator inhibitor (PAI). GCs downregulated PAR and upregulated PAI. Thus, glucocorticoids enhance KS cell growth through the regulation of TGF-β activation.

Glucocorticoids Induce Kaposi's Sarcoma Cell Proliferation Through the Regulation of Transforming Growth Factor-β

Glucocorticoid (GC) use is known to induce or enhance the growth of Kaposi's sarcoma (KS) in many clinical settings including human immunodeficiency virus infection, collagen vascular disease, lymphoproliferative disorders, and renal transplantation. Because GCs may induce immune suppression and thus tumor growth, we determined whether GCs had a direct effect on KS growth. We found that GCs directly induce the growth of KS cell lines. In examining the mechanism of action of GCs, we did not observe induction of known autocrine growth factors for KS including interleukin-1 (IL-1), IL-6, oncostatin-M, basic fibroblast growth factor (bFGF ), and vascular endothelial growth factor (VEGF ). We thus examined factor(s) that inhibit KS growth. Transforming growth factor-β (TGF-β) is produced by KS cells and has pleiotropic effects, including inhibiting the growth of hematopoietic and endothelial cells. We show that TGF-β is produced by KS cells in both the latent and active forms, and that TGF-β is an autocrine growth inhibitory factor. We then studied the effects of GCs on the regulation of TGF-β and found that GCs do not inhibit TGF-β transcription, but significantly inhibit TGF-β activation. This effect is mediated through regulation of the TGF-β activation pathway. TGF-β is activated by plasmin which is positively regulated by plasminogen activator (PA) and PA receptor (PAR), and negatively regulated by plasminogen activator inhibitor (PAI). GCs downregulated PAR and upregulated PAI. Thus, glucocorticoids enhance KS cell growth through the regulation of TGF-β activation.

Advances in Kaposi's sarcoma

KS remains a challenge to clinicians and investigators more than a century after its initial description. Debate continues as to the cell of origin, as well as whether or not it is a true cancer. KS appears to be an opportunistic neoplasm, which in its earliest phase retains some features of a benign hyperproliferative process, but in its late stages behaves like an aggressive malignancy. Pathogenesis seems to involve a predisposed individual (genetically susceptible or immunologically compromised) who comes into contact with an infectious agent, most likely a virus. Cytokines appear to play a major role in the growth of the tumor. The exact role of the KSHV in this process will likely be the subject of much investigation in the future.

Kaposi's sarcoma and its management in AIDS patients. Recommendations from a Scandinavian Study Group

KS is the most frequent malignancy in homo/bisexual male AIDS patients, affecting more than 30% of these patients. KS may present itself as a few innocent cutaneous lesions or may show progression resulting in severe morbidity and mortality. Approximately half of the patients may develop severe progressive disease. The prognosis of patients with progressive disease is poor, with a median survival of less than 6 months. There is no cure for AIDS-related KS, but several therapies are available for palliation. The treatment options may be applied locally or systemically. Radiotherapy is efficacious and safe, but only a few lesions may be treated at one time. For severe progressive KS, systemic therapy with various forms of chemotherapy is used. Three regimes in particular have been focused on, namely bleomycin/vincristine (BV), doxorubicin + BV (DBV), or liposomal daunorubicin (LD) administered every 2 weeks. The agents result in a clinically relevant response (in 50-80% of patients) 2-4 weeks after initiation, but few patients have complete remission of the KS (< 10%), and the tumour may relapse after 4-6 months despite continued therapy. BV is less effective but also less toxic compared with the other regimens. Time to response for DBV may be slightly better than for LD, but the overall efficacy of these 2 regimes is similar. LD treatment is associated with significantly fewer episodes of peripheral neuropathy and alopecia than treatment with DBV. Thus, the recommended order of use of chemotherapeutic agents is BV, LD and DBV. Alpha-interferon may have a role in the small percentage of patients with CD4 cell count > 200 mill/L. In conclusion, several therapeutic options are available for palliation of KS. All systemically applied therapies are associated with severe side-effects and the optimal choice of treatment is a careful balance between response and toxicity. The recent discovery of human herpes virus 8 as a putative causative agent for KS and new potent groups of anti-retroviral agents, may lead to the development of more effective treatments of KS.

The angiogenesis induced by HIV-1 tat protein is mediated by the Flk-1/KDR receptor on vascular endothelial cells

The HIV-1 Tat protein transactivates HIV, viral and some host cell genes. Tat can be released by infected cells and acts extracellularly in the microenvironment, regulating functions of immunocompetent and mesenchymal cells. One of the most striking effects of Tat is the induction of a functional program in vascular cells related to angiogenesis and inflammation (migration, proliferation and expression of plasminogen activator inhibitor-1 and E selectin). Tat induces growth of Kaposi's sarcoma (KS) spindle cells and is angiogenic in vivo and in transgenic mice10-12. We previously reported that Tat is a direct angiogenic factor and noted the Tat arginine- and lysine-rich sequence is similar to that of other potent angiogenic growth factors, such as vascular endothelial growth factor-A (VEGF-A). It is possible that Tat mimics one of these factors by interacting with its growth factor tyrosine kinase receptor. Here we demonstrate that Tat specifically binds and activates the Flk-1/kinase insert domain receptor (Flk-1/KDR), a VEGF-A tyrosine kinase receptor (for review see ref. 13), and that Tat-induced angiogenesis is blocked by agents blocking the Flk-1/KDR receptor. Endothelial cell stimulation by Tat occurs in the absence of activation of FLT-1, another VEGF-A tyrosine kinase receptor.

In vivo transcriptional regulation of the human immunodeficiency virus in the central nervous system in transgenic mice

Human immunodeficiency virus type 1 (HIV-1) causes infections of the central nervous system (CNS) and has been implicated as the causative agent of AIDS-associated encephalopathy and the AIDS dementia complex. The development of in vivo models of HIV-1-mediated gene expression has shown that the HIV long terminal repeat (LTR) from the viral isolate HIV(JR-CSF) specifically supports gene expression in adult and developing CNS. To determine the molecular basis for HIV-1 developmental CNS gene expression, in vivo footprinting analysis by the ligation-mediated PCR technique was performed on CNS tissue from the brain stem of a transgenic mouse. The association of cellular proteins in the CNS with sequences in the LTR was found over sequences that defined the TATA region, the Sp-1 and NF-kappaB sites, and two upstream regions (-111 to -150 and -260 to -300). A purine-rich sequence at positions -256 to -296 of the HIV(JR-CSF) LTR but not of the HIV(IIIB) LTR specifically bound protein in nuclear extracts of newborn brain tested in electrophoretic mobility shift assays. No specific protein binding was observed to this region in liver or HeLa cell nuclear extracts. This suggests the presence of a newly identified transcription factor involved in regulation of HIV-1 gene expression in the CNS.

The human immunodeficiency virus type-1 (HIV-1) Tat protein and Bcl-2 gene expression

Tat protein of human immunodeficiency virus type-1 (HIV-1) plays a central role in viral replication and shows pleiotropic effects on the survival and growth of different cell types. Remarkably, Tat represents the first example of a viral protein, that can also be actively secreted by infected cells and shows a cytokine-like activity on both HIV-1 infected and uninfected cells. We previously reported that the stable expression of tat cDNA rescues Jurkat cell lines from apoptosis induced by a variety of stimuli, such as serum withdrawal, engagement of fas antigen or even a productive infection with HIV-1. These findings suggested that Tat was able to modulate the expression of one or more gene(s) relevant for the control of cell survival/death. Consistently, Jurkat cells stably transfected with tat show an upregulated expression of bcl-2. It is still unsettled whether Tat affects cell survival and bcl-2 expression directly or indirectly, modulating the expression of other cellular genes involved in the control of cell survival or encoding for cytokines. Blocking experiments performed with anti-Tat neutralizing antibodies revealed that TAt increases bcl-2 expression and prevent lymphoid T cells from apoptosis by acting, at least in part, through an autocrine/paracrine loop. While high (nM-microM) concentrations of extracellular Tat display a cytotoxic activity on the antigen-mediated induction of T cell proliferation, low (pM) concentrations of Tat were able to protect both Jurkat cells and primary peripheral blood mononuclear cells from apoptosis. Significantly, pM concentrations of Tat were detected in the sera of some HIV-1 infected individuals as well as in the culture supernatant of HIV-1 infected cells, raising the possibility that these levels of Tat protein may be present physiologically in vivo. The potential relevance of Tat-mediated upregulation of bcl-2 for the pathogenesis of HIV-1 disease is discussed.

Effect of HIV type 1 Tat protein on butyric acid-induced differentiation in a hematopoietic progenitor cell line

The trans-activator protein (Tat) of HIV-1 plays an important role in viral pathogenesis. Since Tat has been shown to alter expression of a number of host cellular genes, we have investigated the role of Tat in modulating gene expression and differentiation in hematopoietic progenitor cells. Tat protein was introduced in K562 cells, a human hematopoietic progenitor cell line, by either scrape-loading onto HeLa (HL)-tat cells or direct electroporation of an affinity-purified glutathione S-transferase (GST)-Tat fusion protein. Under these conditions, butyric acid-induced hemoglobin production in K562 cells was suppressed by 65 and 52%, respectively. However, coculturing with wild-type HeLa cells or electroporation with the control GST protein did not decrease hemoglobin production. To confirm the presence of bioactive Tat protein within K562 cells, the cells were transiently transfected with a pHIV/LTR-CAT prior to the introduction of Tat. A 30- to 40-fold induction in CAT gene expression was observed in the transfected K562 cells, which were either cocultured with HL-tat or were electroporated with GST-Tat. Simultaneous transient transfection of K562 cells with a TAR expression plasmid, to compete for the availability of Tat protein, significantly downregulated the HIV LTR trans-activation by Tat. In addition, overexpression of the TAR RNAs in K562 cells was able to downregulate the suppressive effect of Tat on butyric acid-induced differentiation. RT-PCR analysis of the total RNAs isolated from these cells demonstrated that Tat protein suppressed the butyric acid-induced gamma-globin gene expression by an average of 54% without affecting the level of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNAs. These data indicate that the viral Tat protein plays a significant role in abrogating erythroid differentiation in K562 cells.

Myopathy and spontaneous Pasteurella pneumotropica-induced abscess formation in an HIV-1 transgenic mouse model

In an effort to augment human immunodeficiency virus type 1 (HIV-1) gene expression in transgenic mice, an infectious proviral DNA clone was modified by deleting the two NF kappa B binding sites and some adjacent upstream LTR sequences and replacing them with the core enhancer of Moloney murine leukemia virus (MLV). Two independent lines of MLV/HIV transgenic mice were established that expressed HIV-1-specific RNA in lymphoid tissue, striated skeletal muscle, and the eye lens. Heterozygous animals from each transgenic line spontaneously developed an inflammatory disease of the eye associated with the production of copious amounts of purulent lacrimal secretions beginning at 2 weeks of age. Periorbital abscess formation became grossly apparent by 2 months of age and Pasteurella pneumotropica was cultured from the harderian glands and conjunctival surfaces of many of the MLV/HIV animals but not their nontransgenic, cohabiting littermates. This gram-negative commensal bacterium has been previously associated with a similar disease phenotype in immunocompromised (e.g., nude mice) rodent colonies. MLV/HIV mice developed normally until 15 weeks of age, when weight loss and wasting occurred, culminating in premature death (as earlier as 6 months of age). The cachexia was associated with an initially focal and subsequently progressive myopathy, coinciding with age-related increases of HIV gene expression in muscle.

The epidemiology of AIDS--related neoplasms

The magnitude for and risk factors of the two most important AIDS neoplasm, Kaposi's sarcoma and non-Hodgkin's lymphoma, are reviewed in detail. The association between AIDS and other cancers is mostly speculative because surveillance biases tend to favor detecting associations that may be spurious. The overall relative risk of other cancers appears, however, to be only twofold above that in the general population, with associations being most convincing for anal (but not cervical) cancer and leiomyosarcoma and possible also for Hodgkin's disease, testicular cancer, and conjunctival cancers.

Chicken ovalbumin upstream promoter transcription factor, a transcriptional activator of HIV-1 gene expression in human brain cells

Viral infection of the central nervous system by the human immunodeficiency virus type 1 leads to a wide range of neuropathological disorders. However, the molecular mechanisms governing transcription of the human immunodeficiency virus type 1 genome in brain remain unclear. We have recently established that in brain cells, proteins belonging to the steroid/thyroid/retinoic acid receptor family bind to the -352 to -320 region of the long terminal repeat (LTR). Here, by supershift experiments, we have identified chicken ovalbumin upstream promoter transcription factor (COUP-TF), an orphan member of this nuclear receptor family, as one of the major proteins interacting with this LTR site. Cotransfection studies revealed that COUP-TF is able to dramatically activate LTR-directed gene transcription in human oligodendroglioma but not in astrocytoma cells. This activation occurs through two mechanisms, depending on the LTR sequence. Moreover, in neuronal cells COUP-TF and dopamine, a catecholamine neurotransmitter, enhance LTR-directed transcription by acting on the proximal LTR region. These results reveal the importance of COUP-TF and the dopamine signaling pathway as activators of human immunodeficiency virus type 1 gene expression in brain.