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

Interactions of human immunodeficiency virus type 1 transactivator of transcription protein with signal transduction pathways

The current state of knowledge investigating Tat interactions with signal transduction pathways is still in its infancy but has made significant progress toward understanding HIV pathology. This area is of great interest because Tat is among a small group of newly discovered RNA-based regulators of transcription. What is more important, however, are the implications of understanding these interactions concerning HIV-infected individuals. With the failure to develop effective HIV vaccines after years of development, it is becoming more feasible to conjecture therapies that target Tat as a means to keep HIV in its quiescent state rather than to eliminate the virus. In either case, the intense study of Tat and signal transduction pathways promises to provide a wealth of information about transcriptional control as well as the regulation of immune cell activation.

Role of scatter factor and the c-met protooncogene in the pathogenesis of AIDS-associated Kaposi's sarcoma

Kaposi's sarcoma is a highly lethal tumor in patients with sexually acquired AIDS. A number of etiologic agents have been implicated in the development of this disease in this patient population and there is ample evidence that aberrant production of and responsiveness to KS tumor and host cell-derived cytokines plays a central role in the pathogenesis of AIDS-KS. In this review we propose that aberrant expression SF and c-met is central to the pathogenesis of KS. KS is a serious and life-threatening consequence for many patients with AIDS. Unfortunately, current therapeutic strategies for the treatment of this complex neoplasm have met with only limited success. In view of the poor survival rates for AIDS-KS patients which continue to decline at an alarming rate, it is eminently clear that a better understanding of the etiology and pathogenesis of this form of KS is needed if novel therapeutic strategies designed to successfully combat this disease are to be developed. If our hypothesis is validated, one could envision several approaches whereby the modulation of SF/c-met function or production might lead to a reduction in the incidence and severity of KS lesions. Antibody therapy directed against either SF-producing tumor cells or against the c-met receptor might decrease the incidence of new tumors by limiting their clonal expansion and lead to regression of established tumors by blocking SF-mediated tumor cell proliferation and neovascularization. It might also be possible to suppress production of SF or accessory cytokines involved in the induction SF production and thus short circuit SF/c-met growth-promoting effects. We have outlined a novel hypothesis for understanding the mechanism underlying the development of AIDS-associated KS. This is most certainly not the whole story, however. Clearly, other cytokines and alterations in natural host defenses and the immune system contribute significantly to the development of AIDS-associated KS. We believe, however, that recognition of SF/c-met as a participant in this disease is necessary if we are to more fully understand the pathogenesis of AIDS-associated KS.

Transactivation of cellular genes by human retroviruses

We have focused this chapter on interactions with two of the best characterized transregulatory genes, tax for HTLV-I/II and Tat for HIV-1. Both genes illustrate the complex interplay between retroviral regulatory genes and cellular gene regulation. In both instances a viral gene of relatively straightforward function in the viral context appears to cause extensive dysregulation of cellular genes, either directly or as a consequence of altered cellular differentiation. Understanding this viral/cellular gene cross-talk may elucidate mechanisms leading to malignant transformation autoimmune disease and to neurologic and paraneoplastic complications such as hypercalcemia for HTLV-I/II, as well as the pathogenesis of immune dysfunction and opportunistic malignancy in HIV-I/II-infected individuals. An understanding of functional mechanisms of these transregulatory viral genes will undoubtedly afford better explanations for the myriad manifestations of retroviral infection.

Gene-targeted inhibition of transactivation of human immunodeficiency virus type-1 (HIV-1)-LTR by antisense oligonucleotides

We have used an in vitro approach to study the efficiency of antisense oligonucleotides in inhibiting LTR-(HIV-1)-directed CAT expression catalyzed by tat protein, the functional protein of the transactivator gene. We selected the target sequence localized near the 5' end of the tat mRNA. The following conclusions can be drawn from the data presented here: a) Antisense oligonucleotides modified by conjugation of cholesterol at the 3' end have a severalfold higher inhibitory response, b) inhibitory response is dependent on the mode of introducing oligonucleotides, and c) the inhibition by antisense oligonucleotides is sequence specific and directed towards the targeted region. This approach could be useful for targeting functional regions of regulatory gene products and designing gene-targeted inhibitors of virus replication.

Identification of herpesvirus-like DNA sequences in AIDS-associated Kaposi's sarcoma

Representational difference analysis was used to isolate unique sequences present in more than 90 percent of Kaposi's sarcoma (KS) tissues obtained from patients with acquired immunodeficiency syndrome (AIDS). These sequences were not present in tissue DNA from non-AIDS patients, but were present in 15 percent of non-KS tissue DNA samples from AIDS patients. The sequences are homologous to, but distinct from, capsid and tegument protein genes of the Gammaherpesvirinae, herpesvirus saimiri and Epstein-Barr virus. These KS-associated herpesvirus-like (KSHV) sequences appear to define a new human herpesvirus.

Kaposi's sarcoma in HIV infected women in Germany: more evidence for sexual transmission. A report of 10 cases and review of the literature

OBJECTIVE

To assess the natural history of Kaposi's sarcoma (KS) in HIV-positive women living in Germany.

METHODS

All physicians reporting the diagnosis of KS in a female patient were contacted and asked for detailed information.

DESIGN

Descriptive study of clinical, epidemiological and immunological data of ten women with biopsy-proven KS living in Germany were evaluated. The results are compared with those of other previously published studies of women with KS from Italy, France and the USA.

SETTING

Five centres in Germany.

RESULTS

Of 765 German women with AIDS, only 10 (1.3%) were reported to suffer from Kaposi's sarcoma (KS) compared with 1771 of 8128 men (21.8%). Mean age in these women was 39.7 years. KS was the first AIDS defining event in nine women and the reason for HIV-testing in three. The mean CD4 count was 215/microliters. Two patients were of African origin, had only recently come to Germany and were most likely to have acquired their HIV-infection in Africa. Three patients were i.v.-drug users (IVDU). Two of these (and most likely all three) had worked as prostitutes. Of five women who had contracted HIV via heterosexual contacts, one worked as a prostitute and the other four were married to or were living together with a bisexual HIV-positive man. All four male partners have also developed KS. The course of the disease seems to be particularly aggressive in female patients with eight of 10 women presenting with or progressing to widely disseminated disease with extensive involvement of internal organs. In this cohort survival was longer in females who acquired their HIV infection heterosexually compared to IVDU and was strongly correlated with higher CD4-counts at diagnosis.

CONCLUSIONS

KS seems to run a particularly aggressive course in women. Our data are consistent with a sexually transmittable aetiological agent of KS. Prostitution, an issue yet to be addressed by other authors reporting series of women with KS, was reported in four of our patients. Further studies are needed to clarify the significance of this finding.

Retrovirus-mediated transfer and long-term expression of HIV type 1 tat gene in murine hematopoietic tissues

Replication of the human immunodeficiency virus (HIV) is regulated tightly by the tat and rev genes. The tat gene of HIV is a potent trans-activator of virus gene expression. trans-Activation is mediated through the tat-responsive element (TAR). Tat also has been shown to affect transcription of cellular genes and to trans-activate other viral promoters. In transgenic animals, tat expression in skin was implicated in the development of lesions resembling Kaposi's sarcoma (KS). More recently, evidence has been presented that suggests that Tat might play a role in the maintenance of KS cells. To study the possible role(s) of Tat in pathogenesis and disease progression, we have developed a retroviral vector for the transfer of tat into murine bone marrow cells. We used this transduced bone marrow to repopulate recipient animals, which expressed the tat gene in peripheral blood 6 months after transplantation as determined by PCR amplification of first-strand cDNA. Analysis of the hematopoietic tissues of mice 6 months posttransplantation indicated persistence of the tat gene and its expression in thymus, lymph nodes, spleen, bone marrow, and peripheral blood. Although tat expression was sustained in all hematopoietic tissues, no gross abnormalities were observed. The presence of tat in all hematopoietic tissues strongly suggests transduction of stem or multipotential progenitor cells.

Modulation of cellular gene expression of HIV type 1 infection as determined by subtractive hybridization cloning: downregulation of thymosin beta 4 in vitro and in vivo

Chronic infection with HIV-1 has profound effects on host cell growth and function. We used subtractive hybridization cloning to identify genes whose expression is modulated by HIV-1 infection in the T leukemia cell line CEM. The gene encoding thymosin beta 4, a ubiquitous polypeptide associated with hematopoietic differentiation, showed two- to threefold reduced transcription in HIV-1-infected CEM cells and other HIV-1-infected T cells and macrophages in vitro. Solid-phase radioimmunoassay revealed about a threefold decrease in the level of thymosin beta 4 protein in lysates of infected cells. Northern blot analysis of RNA samples from lymphocytes of five AIDS patients reveals an up to fivefold reduction in the level of thymosin beta 4 mRNA. These results indicate that HIV-1 infection may directly influence the expression of certain physiologically important proteins.

Gastrointestinal disease in the immunocompromised patient

Gastrointestinal (GI) disease is frequent in all types of immunocompromised patients but occurs with greatest frequency in patients with acquired immunodeficiency syndrome (AIDS). Thus, much of this review deals with human immunodeficiency virus (HIV)-related GI diseases. Gastrointestinal diseases in other immunocompromised patients are compared with those in patients with AIDS. Conditions unique to transplant recipients, such as graft-versus-host disease (GVHD) and posttransplant lymphoproliferative disorders (PTLDs), are discussed separately. We have divided these GI diseases into four main categories: (1) HIV-related inflammatory conditions other than opportunistic infections (HIV-related enteropathy, proctocolitis, and CD8 lymphocytosis); (2) inflammatory conditions unrelated to HIV or opportunistic infections (neutropenic enterocolitis, regional enteritislike enteropathy, and GVHD); (3) opportunistic infections (illnesses caused by herpesvirus, cytomegalovirus, and miscellaneous other viruses; Mycobacterium, Candida, Histoplasma, Cryptococcus, Cryptosporidium, Microsporida, Isospora, Leishmania, Toxoplasma and Strongyloides organisms as well as Pneumocystitis carinii; and (4) neoplasias (Kaposi's sarcoma [KS], AIDS-related non-Hodgkin's lymphoma [NHL], HIV-related Hodgkin's disease [HD], PTLDs, and miscellaneous neoplasms). The prevalence, pathogenesis, clinical manifestations, gross pathological findings, and microscopic features of each disease entity are discussed.

Synergy between basic fibroblast growth factor and HIV-1 Tat protein in induction of Kaposi's sarcoma

Basic fibroblast growth factor (bFGF) and human immunodeficiency virus type 1 (HIV-1) Tat protein synergize in inducing angiogenic Kaposi's sarcoma-like lesions in mice. Synergy is due to Tat, which enhances endothelial cell growth and type-IV collagenase expression in response to bFGF mimicking extracellular matrix proteins. The bFGF, extracellular Tat and Tat receptors are present in HIV-1-associated KS, which may explain the higher frequency and aggressiveness of this form compared to classical Kaposi's sarcoma where only bFGF is present.

Characterization of transgenic mice containing adenovirus early region 3 genomic DNA

Human adenoviruses (Ad) contain a complex transcription region (E3) which codes for proteins that interact with several arms of the immune system. However, E3 genes are not essential for replication in tissue culture. An E3-encoded 19,000-molecular-weight (19K) glycoprotein (gp19K) binds to the class I major histocompatibility complex (MHC) in the endoplasmic reticulum and prevents MHC transport to the cell surface. Three other E3 proteins are involved in the inhibition of apoptosis by tumor necrosis factor alpha. The entire E3 genomic DNA was utilized to produce transgenic mice to study the effect of the E3 proteins on pathogenesis of various infectious agents and to investigate the in vivo synthesis and processing of the multiple E3 mRNAs and proteins. There was basal expression of the E3 promoter in the thymus, kidneys, uterus, and testes and at all levels of the gastrointestinal tract. In addition, the E3 promoter of the transgene could be activated in some other organs, including the liver, by infection of these animals with an E3-deficient Ad (Ad7001) which contains a functional E1A region. Transactivation in vivo could also be demonstrated by infusion of bacterial lipopolysaccharide. There appeared to be differential ratios of expression between several of the E3 mRNAs in transgenic lung fibroblasts and primary kidney cells cultured from the transgenic animals. This observation suggested that there was differential mRNA splicing that was organ specific. These transgenic animals should provide a useful model for studying the effects of the E3 proteins on the immune system and on diseases affected either by control of MHC or by selected functions of tumor necrosis factor that are inhibitable by Ad E3 proteins.

Indirect mechanisms of HIV pathogenesis: how does HIV kill T cells?

Although twelve years have passed since the identification of HIV as the cause of AIDS, we do not yet know how HIV kills its target, the CD4+ T cell, nor how this killing cripples the immune system. Prominent theories include direct killing of infected CD4+ T cells by the action or accumulation of cytopathic viral DNA, transcripts or proteins, or by virus-specific cytotoxic T lymphocytes, and indirect killing of uninfected CD4+ T cells (and other immune cells) by autoimmune mechanisms, cytokines, superantigens, or apoptosis. In the past year, studies have provided tantalizing clues as to why infected cells may not die and how these infected cells kill innocent bystander cells.

Cerebral glial tumors and human immunodeficiency virus-1 infection. More than a coincidental association

BACKGROUND

The authors describe the clinical and morphologic patterns in four patients with acquired immune deficiency syndrome (AIDS) who developed intracranial glial tumors.

METHODS

This retrospective study reports 70 patients at various stages of human immunodeficiency virus-1 (HIV-1) infection who underwent stereotactic brain biopsy for an intracerebral space-occupying lesion.

RESULTS

Of these patients, four had glial tumors: one astroblastoma, two astrocytomas, and one glioblastoma. Glial tumors probably arise from a complex interplay of factors; possibilities include the activation of a dominant oncogene or viral inactivation of a tumor suppressor gene by a viral promoter (like the tat protein), impairment of immune defenses (which facilitates the growth of astrocytomas in acute lymphoblastic leukemia), production of cellular growth factors, cytokines, possible infection of glial cells by HIV, and the potentiation of a coinfectious agent.

CONCLUSIONS

These cases illustrate that glial tumors should be considered in the differential diagnosis of brain masses in HIV-1 infection, especially because specific treatment for these tumors is available. Moreover, the occurrence of glial tumors in AIDS patients is not only an important event from a clinical point of view, but may also have implications for the pathogenesis of tumors in AIDS.

HIV type 1 Tat protein induces immunoglobulin and interleukin 6 synthesis by uninfected peripheral blood mononuclear cells

Tat is a potent trans-activating protein encoded by the HIV genome. It is essential for viral replication, but has pleiotropic effects on host cells as well. We demonstrated that exogenous recombinant Tat increases immunoglobulin (Ig) and interleukin 6 (IL-6) production in vitro by normal uninfected peripheral blood mononuclear cells by 100-500%. The optimal Tat concentration was 100 ng/ml, but even a low concentration of 1 ng/ml induced a response in most subjects. The observed induction was inhibited by monoclonal anti-Tat antibodies and 2,3-dimercapto-1-propanol. Both anti-IL-6 antibodies and IL-6 antisense oligonucleotides inhibited Tat-induced IgG and IgA synthesis to some degree, whereas induction of IgM appeared to be independent of IL-6. We conclude that Tat can function in vitro in the absence of any other viral structures and induce Ig and IL-6 production; the clinical significance of these findings remains as yet undetermined.

Role of scatter factor in the pathogenesis of AIDS-related Kaposi sarcoma

Kaposi sarcoma (KS) is a complex multicellular neoplasm that is commonly associated with AIDS. The pathogenesis of KS is not well understood. KS tumor cells grow poorly in vitro and require medium conditioned by retrovirus-infected T lymphocytes. We observed that conditioned medium (CM) from type II human T-cell leukemia virus (HTLV-II)-infected T cells (HTLV-II CM) induces conversion of endothelial cells (ECs) to a KS tumor cell-like phenotype. ECs grown in HTLV-II CM acquired a spindle-shaped morphology, the ability to express factor XIIIa and other KS cell markers, and a cytokine production profile similar to that of KS cells. We found that HTLV-II CM contains large quantities of scatter factor (SF), an angiogenic cytokine that stimulates cell motility. SF induced ECs to become spindle-shaped and express factor XIIIa. Moreover, SF was found to be a mitogen for KS cells in vitro and was identified within KS lesions in vivo. SF mRNA was present in KS cells in vitro, and antibodies against SF inhibited the growth of KS cells. The receptor for SF, the c-met protein, was expressed by ECs, dermal dendrocytes, and KS tumor cells in vitro and in vivo. HTLV-II CM was highly angiogenic in vivo, which was blocked by antibodies against SF. Based on these findings, we suggest that SF plays a role in the initiation and maintenance of KS lesions.

Central nervous system-derived cells express a kappa B-binding activity that enhances human immunodeficiency virus type 1 transcription in vitro and facilitates TAR-independent transactivation by Tat

The Tat protein of human immunodeficiency virus type 1 (HIV-1) is a potent activator of long terminal repeat-directed transcription. While in most cell types, activation requires interaction of Tat with the unusual transcription element TAR, astrocytic glial cells support TAR-independent transactivation of HIV-1 transcription by Tat. This alternative pathway of Tat activation is mediated by the viral enhancer, a kappa B domain capable of binding the prototypical form of the transcription factor nuclear factor kappa B (NF-kappa B) present in many cell types, including T lymphocytes. Tat transactivation mediated by the kappa B domain is sufficient to allow replication of TAR-deleted mutant HIV-1 in astrocytes. The present study demonstrates the existence of kappa B-specific binding factors present in human glial astrocytes that differ from prototypical NF-kappa B. The novel astrocyte-derived kappa B-binding activity is retained on an HIV-1 Tat affinity column, while prototypical NF-kappa B from Jurkat T cells is not. In vitro transcription studies demonstrate that astrocyte-derived kappa B-binding factors activate transcription of the HIV-1 long terminal repeat and that this activation is dependent on the kappa B domain. Moreover, TAR-independent transactivation of HIV-1 transcription is reproduced in vitro in an astrocyte factor-dependent manner which correlates with kappa B-binding activity. The importance of the central nervous system-enriched kappa B transcription factor in the regulation of HIV-1 expression is discussed.

[Kaposi disease and sex hormones: apropos of a case, review of the literature]

The authors report one case of AIDS-related-like Kaposi's sarcoma (KS) in a 59-year-old bisexual man without HIV-1 and HIV-2 infection. KS developed while the patient was receiving both androgen and steroid therapy for aplastic anemia, and regressed after their simultaneous interruption, despite the persistence of aplastic anemia. The authors discuss the etiology of KS in the patient, with a special regard to a putative role of the androgen therapy. The authors examine the arguments of the literature, probably underestimated, that may suggest a role of sex hormones in the pathogenesis of KS.

HIV-1 transactivator protein Tat induces proliferation and TGF beta expression in human articular chondrocytes

The human immunodeficiency virus-1 (HIV-1) protein Tat binds to cell surface antigens and can regulate cellular responses. Tat has similar immunosuppressive effects as transforming growth factor-beta (TGF beta) and both inhibit lymphocyte proliferation. TGF beta is expressed by primary human articular chondrocytes and is their most potent growth factor. The present study analyzed the interactions of TGF beta and HIV Tat in the regulation of human articular chondrocytes. Synthetic or recombinant full-length Tat (1-86) induced chondrocyte proliferation and this was of similar magnitude as the response to TGF beta. Tat peptides that did not contain the RGD motif had similar chondrocyte stimulatory activity as full-length Tat. Among a series of Tat peptides, peptide 38-62 which contains the basic domain was the only one active, suggesting that this region is responsible for the effects on chondrocyte proliferation. Full-length Tat and peptide 38-62 synergized with TGF beta and induced proliferative responses that were greater than those obtained with any combination of the known chondrocyte growth factors. Further characterization of the interactions between Tat and TGF beta showed that Tat increased synthesis and TGF beta activity and TGF beta 1 mRNA levels. The stimulatory effects of Tat and peptide 38-62 on chondrocyte proliferation were reduced by neutralizing antibodies to TGF beta and by TGF beta antisense oligonucleotides. These results identify a virally encoded protein and a synthetic peptide derived from it as novel and potent chondrocyte growth stimuli which act at least in part through the induction of TGF beta.

Tat-mediated delivery of heterologous proteins into cells

The Tat protein of human immunodeficiency virus 1 (HIV-1) can enter cells efficiently when added exogenously in tissue culture. To assess if Tat can carry other molecules into cells, we chemically cross-linked Tat peptides (residues 1-72 or 37-72) to beta-galactosidase, horseradish peroxidase, RNase A, and domain III of Pseudomonas exotoxin A (PE) and monitored uptake colorimetrically or by cytotoxicity. The Tat chimeras were effective on all cell types tested, with staining showing uptake into all cells in each experiment. In mice, treatment with Tat-beta-galactosidase chimeras resulted in delivery to several tissues, with high levels in heart, liver, and spleen, low-to-moderate levels in lung and skeletal muscle, and little or no activity in kidney and brain. The primary target within these tissues was the cells surrounding the blood vessels, suggesting endothelial cells, Kupffer cells, and/or splenic macrophages. Tat-mediated uptake may allow the therapeutic delivery of macromolecules previously thought to be impermeable to living cells.

Activation of HIV-1 transcription by Tat in cells derived from the CNS: evidence for the participation of NF-kappa B--a review

Human immunodeficiency virus type 1 (HIV-1) is the etiologic agent of acquired immune deficiency syndrome (AIDS). The Tat protein of HIV-1 is a potent activator of transcription directed by the viral long terminal repeat. It has been widely reported that this activation requires a specific interaction between Tat and a RNA target termed TAR in the 5'-leader sequence of HIV-1 mRNAs. In this report we present data and describe results which illustrate that under appropriate conditions activation of transcription by Tat occurs independent of the TAR element. The ability to mediate TAR-independent transactivation by Tat is constitutive in some central nervous system cells and requires prior activation in others such as T lymphocytes. Evidence implicating a specific transcription factor in mediating Tat activation is also presented. Studies with site-directed mutants demonstrate that the RNA-binding domain of Tat is dispensable for TAR-independent activation of HIV-1. In contrast, the requirement for specific components of the Tat activation domain suggests that common targets exist for this viral activation factor to exert its activity in TAR-independent and TAR-dependent transactivation pathways of HIV-1 transcriptional activation. A working model of TAR-independent transactivation, which we believe may be responsible for the activation of cellular genes which contribute to AIDS pathology, is presented.

Identification of an 80-kilodalton membrane glycoprotein important for human T-cell leukemia virus type I and type II syncytium formation and infection

Human T-cell leukemia virus type I and type II (HTLV-I and HTLV-II, respectively) infect certain sublines of the BJAB human B-cell line. We observed that the WH subline, but not the CC/84 subline, of BJAB cells were infectible by cell-free HTLV-I or HTLV-II and formed syncytia with cells infected by these retroviruses. This suggests that the BJAB-CC/84 cells possibly lack a membrane molecule(s) important for syncytium formation and infectibility. In order to identify this antigen, we generated polyclonal anti-BJAB-WH antisera which were adsorbed on BJAB-CC/84 cells. The adsorbed antisera bound only BJAB-WH and BJAB-CC/79 cells as demonstrated by complement-dependent cytotoxicity and flow cytometric assays. Furthermore, this adsorbed antisera bound several human T-cell clones, including SupT-1, as determined by flow cytometric assays. The adsorbed antiserum was monospecific as it immunoprecipitated only one 78- to 80-kDa protein from lysates of metabolically labeled BJAB-WH, BJAB-CC/79, and SupT-1, but not BJAB-CC/84, cells. The monospecific antisera detected a glycoprotein composed of a 64- to 66-kDa core protein containing tunicamycin-sensitive N-linked oligosaccharides. This membrane glycoprotein appears to be involved in HTLV-I- and HTLV-II-induced fusion and infection, as the monospecific antisera were capable of inhibiting both of these processes. The monospecific antisera diluted 1:50 and 1:90 inhibited 85 to 90% of syncytium formation induced in BJAB-WH, BJAB-CC/79, and SupT-1 cells cultured with HTLV-I- or HTLV-II-infected MT2, MoT, or FLW human T- or B-cell lines. At the same dilution, antisera inhibited 70 to 80% of infection of BJAB-WH cells by cell-free HTLV-I or HTLV-II. Thus, these studies indicate a role for a 78- to 80-kDa glycoprotein in HTLV-I or HTLV-II infection and syncytium formation.

Endemic Kaposi's sarcoma in Africa and local volcanic soils

Endemic Kaposi's sarcoma (KS) in Africa has been attributed to a geographically-determined environmental factor. Endemic KS, a chronic nodular condition predominantly affecting the feet and legs, is believed to arise in the lymphatic endothelium and is associated with chronic lymphoedema. As such, KS bears a resemblance to podoconiosis (non-filarial elephantiasis). The prevalence of both conditions in highland areas close to volcanoes suggests a shared pathogenetic relationship to exposure to volcanic soils. The lymphatics and lymph nodes of patients with podoconiosis contain particulate alumino-silicates in macrophages consistent with the theory that ultrafine clay minerals are absorbed through the feet. The resulting chronic lymphatic irritation, inflammation, and collagenosis causes obstruction and lymphoedema. The geographical proximity of endemic KS to areas containing volcanic clay minerals, its lympho-endothelial origin, predilection for the feet and legs, and its prevalence among rural peasants and cultivators, suggest a common aetiology. Other features point to the participation of a low-grade, possibly sexually-transmitted, infective agent that becomes more pathogenic in the presence of immunosuppression. Damage to the dermal lymphatics of the feet and legs by absorbed clays could impair local immunity to such an agent. Endemic KS would then occur in exposed individuals who harbour the KS infective agent and are susceptible to the KS phenotype (males).

Changes in cellular proteins associated with the expression of human immunodeficiency virus type 1 trans-activator protein Tat

Earlier studies have revealed a distinct class of regulatory proteins known as trans-activator proteins in diverse biological systems. These proteins have been shown to act on both homologous and heterologous promoter targets. Activation of heterologous targets is speculated to be an integral part of virus-induced pathogenesis. To verify this hypothesis, stable Tat-producing human rhabdomyosarcoma (RD) cell lines were generated. These cell lines produced significant levels of functional Tat, as measured by transfection with the reporter plasmid pLTR-CAT. Tat-producing cells, although morphologically similar to the control, exhibited a slower growth rate. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of the cellular proteins from control (tat-) and tat+ cells revealed increased quantities of 34- and 40-kD proteins along with the appearance of a new 74-kD protein in tat+ cells. Subsequent two-dimensional gel analysis revealed several additional differences. Tat+ cell lines produced two proteins of M(r) 19.5 and 44 kD anew, while proteins with M(r) 14.5, 42, and 52.5 kD were in greater abundance. Interestingly, a 26-kD protein that was originally present in the G418+/tat- (control) sample disappeared in the presence of Tat. These data support a possible modulator role for Tat in cellular gene expression.

Expression of fibroblast growth factors and their receptors in acquired immunodeficiency syndrome-associated Kaposi sarcoma tissue and derived cells

BACKGROUND

Fibroblast growth factors (FGF), such as basic FGF, have been implicated in the development of Kaposi sarcoma (KS) in vitro. The expression of several genes of the FGF family and their receptors in KS tumor lesions and KS-derived cells were evaluated.

METHODS

Cultures of KS-derived cells were established. The expression of FGF family members and their receptors in these cells and in fresh biopsies from KS tumors was evaluated by reverse transcription polymerase chain reaction (RTPCR). The RTPCR products were confirmed by nucleotide sequencing.

RESULTS

The expression of basic FGF and FGF receptor-1 (flg) was detected in all the samples tested. Acidic FGF (aFGF) and FGF-5 were detected in two of six and four of six KS tumor specimens, respectively, whereas both of these growth factors were expressed in all of the cell cultures, including six KS-derived cell cultures and human endothelial cells and smooth muscle cells. FGF-6 was expressed in two of six KS tumor specimens, but was not expressed in any of the cultured KS cells. Like flg, bek was expressed in all tissue samples and KS-derived cell cultures except in one KS specimen obtained from the patient's tongue showing expression of a high level of FGF-6.

CONCLUSIONS

These results suggest that the expression of FGF in KS tumors with the coexpression of FGF receptors may provide a basis for autocrine and paracrine mechanisms contributing to the development of KS.

Human immunodeficiency virus type 1 infection of the brain

Direct infection of the central nervous system by human immunodeficiency virus type 1 (HIV-1), the causative agent of AIDS, was not appreciated in the early years of the AIDS epidemic. Neurological complications associated with AIDS were largely attributed to opportunistic infections that arose as a result of the immunocompromised state of the patient and to depression. In 1985, several groups succeeded in isolating HIV-1 directly from brain tissue. Also that year, the viral genome was completely sequenced, and HIV-1 was found to belong to a neurotropic subfamily of retrovirus known as the Lentivirinae. These findings clearly indicated that direct HIV-1 infection of the central nervous system played a role in the development of AIDS-related neurological disease. This review summarizes the clinical manifestations of HIV-1 infection of the central nervous system and the related neuropathology, the tropism of HIV-1 for specific cell types both within and outside of the nervous system, the possible mechanisms by which HIV-1 damages the nervous system, and the current strategies for diagnosis and treatment of HIV-1-associated neuropathology.

Case report: bacillary angiomatosis with massive visceral lymphadenopathy

Bacillary angiomatosis is a newly characterized infectious disease occurring mainly in patients with AIDS. Most patients have cutaneous angiomatosis lesions resembling Kaposi's sarcoma or pyogenic granuloma. Although the disease may be life-threatening if not treated, it is curable with appropriate antibiotic therapy. A patient had a fever, nightsweats, abdominal pain, pleural effusions, and asymmetric peripheral lymphadenopathy. Computed tomography of the chest and abdomen revealed a unique pattern of enhancement of lymph nodes that, to this research team's knowledge, has not been reported previously with this condition. Appropriate antibiotic therapy resulted in a complete resolution of the disease. Included is a discussion of the clinical presentation, etiology, histology, and treatment of bacillary angiomatosis.

Spinal epidural leiomyoma occurring in an HIV-infected man. Case report

A case of spinal epidural leiomyoma is reported in a 52-year-old man infected with the human immunodeficiency virus (HIV). The tumor arose in the epidural region at the T-3 vertebral level, and the patient presented with radicular pain in the right T-3 dermatome. While soft-tissue tumors such as Kaposi's sarcoma and lymphomas have been well documented in association with HIV infection, this is the first reported case of primary spinal leiomyoma. Isolated cases of leiomyomas and leiomyosarcomas in unusual locations have been reported, notably in pediatric HIV-positive patients, perhaps indicating a causal relationship. This case may represent further evidence of such an association.

Cutaneous neoplasms in a military population of HIV-1-positive patients. Military Medical Consortium for the Advancement of Retroviral Research

BACKGROUND

In HIV-1-positive patients there have been no prospective studies that show an increase in cutaneous neoplasms.

OBJECTIVE

We observed HIV-1-positive patients to determine whether or not there was an increased incidence of cutaneous malignancies.

METHODS

A total of 724 HIV-1-positive patients were examined during a 36-month period for the development of cutaneous malignancies.

RESULTS

The most common cutaneous neoplasm found was Kaposi's sarcoma, especially in patients with late-stage disease. Basal cell carcinomas were the next most frequent tumor. We have also seen three malignant melanomas and two squamous cell carcinomas. Five patients had malignant lymphoma. One patient had a primary lymphoma of subcutaneous soft tissue; in one patient multiple cutaneous lesions developed.

CONCLUSION

The distribution and prevalent types of cutaneous neoplasms in HIV-1-positive patients appear to differ from those found in other immunosuppressed populations. This may be the result of the different patterns and periods of immunosuppression in these patients and/or associated cocarcinogens to which these patients frequently are exposed.

The Tat protein of human immunodeficiency virus type 1, a growth factor for AIDS Kaposi sarcoma and cytokine-activated vascular cells, induces adhesion of the same cell types by using integrin receptors recognizing the RGD amino acid sequence

Spindle-shaped cells of vascular origin are the probable tumor cells of Kaposi sarcoma (KS). These cells, derived from patients with KS and AIDS, proliferate in response to extracellular Tat protein of human immunodeficiency virus type 1. Normal vascular cells, believed to be the progenitors of AIDS-KS cells, acquire spindle morphology and become responsive to the mitogenic effect of Tat after culture with inflammatory cytokines. Such cytokines are increased in human immunodeficiency virus type 1-infected people, suggesting that immune stimulation (rather than immune deficiency) is a component of AIDS-KS pathogenesis. Here we show that (i) Tat promotes adhesion of AIDS-KS and normal vascular cells; (ii) adhesion of normal vascular cells to Tat is induced by exposure of the cells to the same cytokines; (iii) adhesion is associated with the amino acid sequence RGD of Tat through a specific interaction with the integrin receptors alpha 5 beta 1 and alpha v beta 3, although it is augmented by the basic region; and (iv) the expression of both integrins is increased by the same cytokines that promote these cells to acquire spindle morphology and become responsive to the adhesion and growth effects of Tat. The results also suggest that RGD-recognizing integrins mediate the vascular cell-growth-promoting effect of Tat.

Tat protein of human immunodeficiency virus type 1 represses expression of manganese superoxide dismutase in HeLa cells

Using a HeLa cell line stably transfected with the tat gene from human immunodeficiency virus type 1, we have found that the expression of the regulatory Tat protein suppresses the expression of cellular Mn-containing superoxide dismutase (Mn-SOD). This enzyme is one of the cell's primary defenses against oxygen-derived free radicals and is vital for maintaining a healthy balance between oxidants and antioxidants. The parental HeLa cells expressed nearly equivalent amounts of Cu,Zn- and Mn-SOD isozymes. Those cells expressing the Tat protein, however, contained 52% less Mn-SOD activity than parental cells, whereas that of the Cu,Zn enzyme was essentially unchanged. The steady-state levels of Mn-SOD-specific RNAs were also lower in the HeLa-tat cell line than in the parental line. No difference was seen in the steady-state levels of Cu,Zn-SOD-specific RNAs. In addition to the decreased Mn-SOD-activity, HeLa-tat cell showed evidence of increased oxidative stress. Carbonyl proteins were markedly higher, and total cellular sulfhydryl content decreased in cell extracts at a faster rate, probably reflecting ongoing lipid peroxidation. HeLa and HeLa-tat extracts were incubated with radiolabeled Mn-SOD transcripts, and the reaction products were subjected to UV crosslinking, digestion with ribonuclease A, and electrophoretic analysis. The results suggest a direct interaction between Tat protein and Mn-SOD gene transcripts.

Histopathological observation of joint lesions of extremities in mice transferred genome

Pathological examination of arthritic lesions in transgenic mice produced by the pX region of the human T-cell leukemia virus type-1 (HTLV-1) was carried out. Clinically, erythema, swelling and/or ataxia of the limb joints were observed in many transgenic mice about 1 month-old. Histopathologically, proliferation of synovial lining cells, infiltration of inflammatory cells with lymphoid structures and formation of pannus with cartilage and/or subchondral bone destructions were observed in various joints of transgenic mice. The frequency of abnormalities in the joints was higher in females than in males. These histopathological findings were very similar to those of human rheumatoid arthritis (RA). Present results indicate that the pX genome of the HTLV-1 is an etiological agent for the incidence of arthritic lesions in the transgenic mice.

Marked pulmonary function abnormalities in a case of HIV-associated pulmonary hypertension

Recent reports have suggested an association between primary pulmonary hypertension and human immunodeficiency virus (HIV) infection. This appears to be an accelerated syndrome, associated with a relatively brief duration of symptoms, yet prominent right ventricular failure and severe pulmonary hypertension on presentation. We present a case of a primary pulmonary hypertension in a 35-year-old HIV-seropositive hemophiliac. His accelerated clinical course is consistent with previously reported cases of HIV-related pulmonary hypertension. However, this patient's pulmonary function tests revealed marked hyperinflation, a decreased diffusing capacity, and no airflow obstruction. To our knowledge, this very usual constellation of pulmonary function changes has not been described previously in this syndrome.

Cloned spindle and epithelioid cells from murine Kaposi's sarcoma-like tumors are of endothelial origin

Kaposi's sarcoma (KS) is a complex neoplasm comprising spindle cells, vascular structures, erythrocytes, and an inflammatory infiltrate. The pathogenesis of this disorder is not yet understood, which is a major impediment to the design of safe and effective new therapies. We previously reported a murine model in which simian virus 40 (SV40) T-antigen-transformed murine endothelial cells induce lesions with the histopathologic features of KS. We have now cloned by limiting dilution seven morphologically distinct tumor-derived lines, all of which express the SV40 T antigen. Because SV40 is non-permissive in mouse cells, the presence of this viral marker permits definitive identification of cellular origin. We report here that both spindle cell and epithelioid cell clones from these KS-like tumors are derived from endothelial cells.

HIV-1 infection stimulates T cell invasiveness and synthesis of the 92-kDa type IV collagenase

Tissue-specific localization of HIV-1-infected lymphoid cells may contribute to clinical manifestations of AIDS. Therefore we investigated the effect of HIV-1 infection on mechanisms of T lymphocyte invasion, a process required for movement of cells into and out of the circulation. In the present study, we demonstrate that HIV-1-infected human lymphocytes secrete increased amounts of the human 92-kDa type IV collagenase when compared to uninfected lymphocytes. Furthermore, HIV-1-infected lymphocytes degrade the extracellular matrix proteins collagen IV and fibronectin, and they are more invasive through a reconstituted basement membrane when compared to uninfected cells. The addition of either antibody to the 92-kDa collagenase or TIMP-2, a type IV collagenase inhibitor, abolishes invasive activity. These data suggest that HIV-1-infected lymphocytes express phenotypic characteristics that are consistent with an enhanced ability to leave the circulation and to localize in target tissues. Local viral infection or the release of viral proteins, cytokines, or proteolytic enzymes in tissues may contribute to pathogenesis.

The foamy virus family: molecular biology, epidemiology and neuropathology

The family of foamy viruses designates a group of retroviruses which share a specific morphology and provoke characteristic cytopathic effects in cultured cells. Like HTLV and HIV, foamy viruses are complex viruses encoding a number of ancillary genes in addition to gag, pol and env, including a transcriptional transactivator. Foamy viruses are endemic in various primate species, and human foamy viruses (HFV) have been isolated from patients with various neoplastic and degenerative diseases. Despite a growing body of knowledge on the biology of foamy viruses, it has not yet been possible to identify a disease specifically caused by foamy virus infection. After reviewing the epidemiology and molecular biology of the various animal foamy viruses, this article focuses on the pathogenic properties of HFV in transgenic mouse systems. HFV transgenes exhibit a striking neurotropism and elicit a progressive degenerative disease of the central nervous system and striated muscle. Similarly to patients with HIV-associated encephalopathy, HFV transgenic mice develop accumulations of syncytial giant cells in their brains. The relevance of these findings for human neuropathology is discussed.

Cytotoxic effect on lymphocytes of Tat from human immunodeficiency virus (HIV-1)

The human immunodeficiency virus type 1 (HIV-1) genome codes for trans-activator Tat, an 86-residue protein whose expression is critical for viral replication. Full-length Tat and Tat peptides from HIV-1 were chemically synthesized using optimized solid phase technique. Synthetic Tat2-86 was found not only to inhibit antigen-induced human peripheral blood lymphocyte (PBL) proliferation in vitro, as described by Viscidi et al. [1989, Science 246, 1606-1608], but also mitogen-induced PBL proliferation, with 50% inhibition obtained at 0.9 and 8 microM, respectively. To assess the mechanism by which Tat exert its inhibitory effect, we analysed its interaction and effect on CD4(+)-cells. Direct fluorescence and indirect immunofluorescence assays analysed by flow cytometry showed that fluorescein isothiocyanate-labeled and -unlabeled Tat interact (> 0.2 microM) with CD4-expressing lymphoid cells (CEM cell line). Experiments of chromium-51 release and Trypan blue exclusion on these tumor cells in vitro have demonstrated the capacity of Tat to modify cellular membrane permeability and cell viability, in a dose-dependent manner. The use of Tat peptides revealed that those containing the Tat basic region from 49 to 57 were able to bind to the cell membrane and to exhibit a cytotoxic activity on lymphocytes. Together, the data suggest that the potential cytotoxicity of Tat on lymphocytes could be directly implicated in virus-induced immune dysfunction observed in HIV-1 infected patients.

Cutaneous disorders and viral gene expression in HIV-1 transgenic mice

Patients infected with HIV-1 experience several hyperproliferative skin disorders, including seborrheic dermatitis, ichthyosis, and psoriasis. Transgenic mice carrying a subgenomic HIV-1 proviral construct lacking the gag and pol genes were found to develop proliferative epidermal lesions, manifested as diffuse epidermal hyperplasia in homozygous transgenic mice and benign papillomas in heterozygous transgenic mice. Nonpapillomatous skin from both homozygotes and heterozygotes expressed viral RNA, and the viral envelope protein gp120 was localized to the suprabasal keratinocyte. Papillomas contained increased amounts of both viral mRNA and envelope glycoprotein. Exposure of transgenic mice to doses of ultraviolet B (UV-B) irradiation that induced cutaneous injury increased viral gene expression and resulted in the development of papillomas within 14-21 days. Cutaneous injury induced by phenol and liquid nitrogen had similar effects. These data support a role for HIV-1 gene products in the pathogenesis of proliferative epidermal disorders associated with HIV-1 infection. Further, they suggest that the process of wound repair increases HIV-1 gene expression in this transgenic mouse model.

Kaposi's sarcoma. Epidemiology, pathogenesis, histology, clinical spectrum, staging criteria and therapy

The acquired immunodeficiency syndrome (AIDS) epidemic has had a profound impact on our understanding of Kaposi's sarcoma (KS). Epidemiologic features suggest a sexually transmitted cofactor in the pathogenesis of AIDS-associated KS (AIDS-KS), and several putative agents have received intense scrutiny. Cell culture studies suggest that the angiogenesis of AIDS-KS is stimulated by both human immunodeficiency virus proteins and growth factors that may be involved in the development and progression of AIDS-KS, thereby providing a rationale for new therapeutic interventions. The dermatologist is uniquely qualified to provide care for the majority of patients with KS, as many patients have cutaneous lesions amendable to local therapy (cryotherapy, intralesional therapy, simple excision). Patients requiring more aggressive local therapy (radiation therapy) or systemic therapies (interferon, chemotherapy) can be easily recognized. Standardized staging criteria provide assistance for determining appropriate local or systemic therapy and for evaluating and comparing responses to new therapies. This article reviews the epidemiology, pathogenesis, histologic features, clinical spectrum, staging criteria, and treatment of KS.

Kinetics of expression of prion protein in uninfected and scrapie-infected N2a mouse neuroblastoma cells

The scrapie prion protein, PrPSc, is formed from its isoform, the cellular PrPc. There is evidence available indicating that PrPSc is a necessary component of the infectious prion particle to cause a series of transmissible spongiform encephalopathies. We have used immunocytochemistry and RNA blotting techniques to investigate if infection with prions results in an increased PrP gene expression. For the experiments we used N2a cells which had been infected with prions (ScN2a cells). We demonstrated by confocal laser scanning microscopy that PrP-protein was present in the nucleus (predominantly in the nucleoli) of ScN2a cells. Analysis of the PrP-mRNA levels both in N2a- and in ScN2a cells using cDNA encoding PrPc revealed no marked alteration of the mRNA steady state level between the two cell strains. Likewise, in run-off experiments no changes in either PrP-specific transcription or in general transcriptional activity were found. The half-life of PrP-mRNA was found to be identical in both cell strains (7h). Taken together, these results show that PrPSc and/or PrPc is present in the nucleus (nucleoli) of ScN2a cells but does not display an effect on the expression of the PrP gene.

Induction of cell differentiation by human immunodeficiency virus 1 vpr

Cell lines from rhabdomyosarcomas, which are tumors of muscle origin, have been used as models of CD4-independent HIV infection. These cell lines can be induced to differentiate in vitro. We report here that the vpr gene of HIV1 is sufficient for the differentiation of the human rhabdomyosarcoma cell line TE671. Differentiated cells are characterized by great enlargement, altered morphology, lack of replication, and high level expression of the muscle-specific protein myosin. We have also observed the morphological differentiation and inhibition of proliferation of two other transformed cell lines. vpr-transfected cells remain fully viable in culture for extended periods. These observations elucidate a potential role for vpr in the virus life cycle and raise the possibility that some aspects of HIV-induced pathologies may be caused by a disturbance of cells by vpr.

Expression of the Tat protein of HIV1 in human promonocytic U937 cells

Numerous studies have shown that, upon HIV1 infection, human promonocytic U937 cells were induced to differentiate, as indicated, for example, by increased expression of adhesion molecules. One of the viral proteins involved in this process might be the Tat protein. Indeed, this viral protein, which is essential for productive infection, has also been shown to display growth-stimulating properties and immunomodulatory activities. In order to apprehend the role of the HIV1 tat gene in inducing the differentiation of HIV1-infected U937 cells, we have successfully introduced this gene into U937 cells by infecting them with retroviral particles transducing tat. The effect of the Tat protein constitutively expressed by these cells upon their differentiation was then evaluated by looking for the expression of the c-fos and of the c-fms proto-oncogenes which are linked to the differentiation of myelomonoblastic cells. Northern blot analysis revealed in these cells, an increase in the transcription of these two proto-oncogenes, and this increase was amplified after treatment with phorbol myristate acetate. No such increase was observed in control U937 cells. These results indicate that, among HIV1 gene products, the Tat protein appears to trigger monocytic differentiation, and suggests that this viral protein directs progenitors of the monocyte/macrophage lineage towards a differentiation stage in which production of viral antigens and virions might be more efficient.