Effect of human T lymphotropic retrovirus-I exposure on cultured human glioma cell lines

Serum mitogenic activity on in vitro glial cells in Neurofibromatosis type 1

Glial mitogenic effect was investigated in sera from the following groups of subjects: group (1) 31 patients clinically and genetically affected by Neurofibromatosis type 1 (NF1) belonging to different families; group (2) 42 patients without family history of NF1 affected by sporadic neoplasms of the same histogenetic origin as the proliferative lesions that are present in NF1; group (3) 51 healthy volunteers without family history of NF1 nor of neoplastic disease; group (4) 54 clinically healthy relatives of the NF1 patients included in the first group. All NF1 patients and 3/54 healthy relatives had alterations of exons 31 or 32 of NF1 gene. Glial proliferation, measured by [3H]thymidine incorporation, was significantly increased by sera from all NF1 patients and from 23/54 of clinically healthy relatives, as compared to sera from healthy volunteers. This serum mitogenic activity strongly suggests the existence of soluble glial proliferating molecules in NF1 families. The molecular weight (3-30 kDa), the heat- and freeze-stability and the specificity for glial cells, suggest that the molecules responsible for this mitogenic effect are different from the growth factors previously described in NF1-associated tumor extracts and from lymphokines. Within each NF1 family, the maximal serum dilution stimulating glial proliferation was similar both in affected members and in their clinically healthy relatives. Since none of the clinically healthy relatives showing serum mitogenic activity was positive for the NF1 mutation analysis and, conversely, those having altered exons 31 or 32 of NF1 gene did not show any mitogenic activity; these results suggest that the phenotype expression of NF1 might depend not only on the NF1 mutations per se, but also on other genetic or epigenetic factors, such as serum glial proliferating molecules.

Anti-beta 2-glycoprotein I antibodies bind to central nervous system

Anti-beta 2-GPI antibodies (a beta 2-GPI) were found in serum from patients with anti-phospholipid syndrome (APS) and/or systemic lupus erythematosus (SLE). Since a beta 2-GPI are often found in patients with anti-cardiolipin antibodies (aCL), their role in thrombosis as well as other central nervous system (CNS) manifestations in APS is unclear. We, therefore, investigated whether affinity-purified a beta 2-GPI bind the CNS. Astrocyte and neuron cell lines and histological sections were used as CNS substrates. Indirect immunofluorescence and/or streptavidin-biotin-peroxidase techniques revealed that astrocytes, neurons and vascular endothelium were bound by purified a beta 2-GPI (mouse monoclonal, rabbit polyclonal, human serum Ig a beta 2-GPI). This suggests a potential role for a beta 2-GPI in the CNS damage, as a beta 2-GPI might contribute to CNS pathology by either a direct interaction with astrocytes and neurons or an interaction with cerebral vascular endothelial cells. CNS immunoreaction was also demonstrated using six a beta 2-GPI-positive sera from patients (four with neurological manifestations). No binding to CNS was seen using a beta 2-GPI-negative sera, i.e. five from SLE patients (two with CNS involvement) and six healthy donors, or a monoclonal aCL without a beta 2-GPI immunoreactivity. Thus, the CNS reactivity by the a beta 2-GPI-positive sera appears specifically due to a beta 2-GPI and independent from aCL. Because of the presence of aCL in all patient sera, and the CNS involvement in three control patients, it is not possible to attribute a direct role for a beta 2-GPI in neurological diseases in this study.

Transactivation of human T-cell leukemia virus type 1 by herpes simplex virus type 1

HTLV-1 transcription depends upon activation by the HTLV-1 tax gene product. In addition, various substances and cellular transcription factors are also known to activate the HTLV-1 long terminal repeat (LTR)-mediated transcription in the absence of Tax. In this work we demonstrate that infection of either Jurkat or 293 cell lines with herpes simplex I (HSV-1), a widespread infectious virus of humans, activates HTLV-1 LTR-mediated gene expression. Further investigation revealed that each of the immediate-early (IE) gene products--ICPO, ICP4, and ICP27--of HSV-1 transactivates the HTLV-1 LTR-mediated gene expression in the absence of Tax. The HSV-1 activation is additive to Tax activation in its presence in the cell. Three 21 base repeats upstream of the TATA box are known as the TAX responsive elements (TRE). Recombinant HTLV-1 minimal promoter composed of the HTLV-1 TATA box fused to a synthetic 21 base TRE is responsive to Tax but not to HSV-1 activation. It thus can be concluded that HSV-1 IE gene products and Tax transactivates HTLV-1 LTR mediated gene expression through different transcription complexes. The results presented in this work may point to one possible way for the transition of HTLV-1 from a quiescent to an actively replicating stage.

Comparative analysis of the antibody response to the HTLV-I gag and env proteins in HTLV-I asymptomatic carriers and HAM/TSP patients: an isotype and subclass analysis

We have compared the immunoglobulin isotype and IgG subclass and the titre of neutralizing antibody responses to the human T cell lymphotropic virus type I (HTLV-I) between a group of asymptomatic HTLV-I infected individuals and a group with the neurological disease HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP). A western blot titration assay and an envelope peptide ELISA were used to determine the presence and titre of isotype and IgG subclass responses to the gag p19 and p24 proteins and to the envelope protein. Significant increases were observed in the number of individuals seropositive for a particular isotype and IgG subclass in the HAM/TSP group versus the asymptomatic group particularly for IgM and IgE and to a lesser extent, IgA. The predominant IgG subclasses to the HTLV-I p19, p24 and envelope proteins were IgG1 and IgG3. This finding was also observed in the titres of the antibody responses to these HTLV-I proteins. The HAM/TSP group also exhibited significantly higher neutralizing antibody titres than the asymptomatic group. This evidence suggests that some form of chronic immune stimulation might be involved in the immunopathogenesis of HAM/TSP. In addition, by following the Western blot titre to the IgM and IgE isotypes in particular, it may be possible to identify asymptomatic individuals progressing to HAM/TSP.

Identification of human T-cell lymphotropic virus type I 21-base-pair repeat-specific and glial cell-specific DNA-protein complexes

The human T-cell lymphotropic virus type I (HTLV-I)-encoded protein, Tax, is capable of trans-activating HTLV-I transcription by interacting with specific sequences in the HTLV-I long terminal repeat (LTR) which comprise an inducible enhancer containing three imperfect tandem repeats of a 21-bp sequence. There is no evidence that purified Tax can bind to DNA in the absence of cellular factors, suggesting that Tax most likely regulates transcription via interaction with cellular factors. Since HTLV-I is a documented agent of adult T-cell leukemia and tropical spastic paraparesis, disorders of the immune and nervous systems, respectively, characterization of cellular factors of lymphoid and neuroglial origin which interact with the 21-bp repeat elements is essential to understanding of the mechanisms involved in basal and Tax-mediated transcription in cells of immune and nervous system origin. Utilizing electrophoretic mobility shift (EMS) analyses, we have detected both 21-bp repeat-specific and glial cell-specific DNA-protein complexes. Several 21-bp repeat-specific DNA-protein complexes were detected when nuclear extracts derived from cells of lymphoid (Jurkat, SupT1, and H9), neuronal (IMR-32 and SK-N-MC), and glial (U-373 MG, Hs683, and U-118) origin were used in reactions with each of the three 21-bp repeat elements. In addition, a glial cell-specific DNA-protein complex was detected when nuclear extracts derived from U-373 MG, Hs683, and U-118 glial cell lines reacted with the promoter-distal and central 21-bp repeat elements. Furthermore, EMS analyses performed with nuclear extracts derived from lymphocytic and glial cell origin and a 223-bp fragment of the HTLV-I long terminal repeat encompassing the three 21-bp repeat elements (designated Tax-responsive elements 1 and 2, TRE-1/-2) have also resulted in the detection of glial cell type-specific DNA-protein complexes. Competition EMS analyses with oligonucleotides containing transcription factor binding site sequences indicate the involvement of a cyclic AMP response element binding protein in the formation of DNA-protein complexes which form with all three 21-bp repeat elements and the glial cell-specific DNA-protein complex as well as the involvement of Sp1 or an Sp1-related factor in the formation of the 21-bp repeat III-specific DNA-protein complexes.

Neuroaxonal dystrophy in HTLV-1-associated myelopathy/tropical spastic paraparesis: neuropathologic and neuroimmunologic correlations

Detailed neuropathologic and immunohistologic analysis of a case of serologically and polymerase chain reaction-confirmed human immunodeficiency virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is reported in a 73-year-old North American black woman. In addition to the usual neuropathologic features of HAM/TSP, including tractal degeneration of the spinal cord, leptomeningeal and perivascular fibrosis, perivascular demyelination and chronic inflammation, neuroaxonal spheroids were prominent in the spinal cord. Neuroaxonal dystrophy was characterized by neurofilamentous masses that were immunoreactive for phosphorylated neurofilament epitopes, but not ubiquitin. Neuroimmunologic analysis of the inflammatory reaction revealed a prevalence of CD8+ T cells and class I major histocompatibility molecules (MHC) (HLA-ABC and beta 2-microglobulin), but very few CD4+ T cells. Microglia were highly reactive for class II MHC (HLA-DR alpha) and this was attributed to activation, rather than CD4 interaction, since CD4 presence was minimal. Inflammatory cytokine immunoreactivity was also detected in glia. It is concluded that the cumulative effects of cytotoxic T cell (CD8) infiltration and the possible involvement of cytokines were responsible for the unusual degree of neuroaxonal dystrophy and vascular fibrosis, as well as the observed demyelination in this case.

Protective effect of interferon beta on human T cell leukaemia virus type I infection of CD4+ T cells isolated from human cord blood

The present study shows the effect of human interferon beta (IFN beta) on the susceptibility of highly purified cord blood CD4+ T cells to infection with the human T cell leukaemia virus type I (HTLV-I). Unfractionated cord blood mononuclear cells (CBMC), or a separated CD4+ T cell subpopulation (CBCD4) were exposed to HTLV-I by cocultivation with a chronically infected virus-donor cell line. The results show that presence of proviral DNA as well as virus transcription was markedly reduced by IFN beta in both populations, indicating that this cytokine protects not only unfractionated CBMC but also purified CBCD4 cells from virus infection. Moreover IFN beta treatment caused 60%-80% inhibition of virus expression in CBCD4, assayed as the presence of virus core protein p19. This study demonstrates that IFN beta is able to inhibit HTLV-I infection of CBMC through a mechanism that does not necessarily involve cell-mediated natural or antigen-dependent immunity afforded by CBMC subpopulations distinct from targets of HTLV-I infection. Therefore it is reasonable to conclude that IFN beta has a direct protective effect on CBCD4, through induction of antiviral resistance/activity in target cells.

Gene therapy of malignant brain tumors: a rat glioma line bearing the herpes simplex virus type 1-thymidine kinase gene and wild type retrovirus kills other tumor cells

Tumor cells infected with a retrovirus vector (VIK) containing the herpes simplex virus thymidine kinase (HSV-TK) gene can be selectively killed by treatment with nucleoside analogues, such as ganciclovir. To mediate delivery of the HSV-TK gene to "recipient" tumor cells, "donor" C6 rat glioma cells infected with the VIK vector (C6VIK) were superinfected with wild type Moloney murine leukemia virus (WT Mo-MLV). These modified donor cells (C6VIKWT) produced both wild type retrovirus and the VIK vector. In culture, C6VIKWT cells were 300-fold more sensitive to the toxicity of ganciclovir than were C6VIK cells, suggesting that the presence of wild type retrovirus contributed to the toxicity. Co-culture of C6VIKWT cells with the C6 subline, C6BAG, sensitized the latter to ganciclovir treatment. Nude mice inoculated subcutaneously with a mixture of C6VIKWT and C6BAG cells showed regression of subsequent tumors when treated with ganciclovir. The observations show that tumor cells modified in culture by infection with a retrovirus bearing the HSV-TK gene and wild type retrovirus are not only sensitive to ganciclovir, but can transfer this sensitivity to neighboring "naive" tumor cells in culture and in vivo.

Correlation between P19 presence and MHC class II expression in human fetal astroglial cells cocultured with HTLV-I donor cells

The possibility of a direct infection of human brain by HTLV-I, has been studied using an in vitro model. Human fetal astroglial cells were cocultivated with irradiated HTLV-I donor cell line MT-2, and assayed for the presence of HTLV-I core protein p19 after 1 week. Fifty-six per cent of GFAP positive astrocytes showed the viral core protein p19 and increased expression of Class II MHC antigens. Electron microscopy of astroglial cells exposed to HTLV-I revealed the presence of vacuoli-like structures containing viral core protein p19. Cell intermediate filament cytoskeleton was also disorganized. Even if this study does not provide direct evidence for virus replication inside astroglial cells, all these findings suggest that HTLV-I can indeed enter the cell and exert a cytopathic effect. Therefore the results of the present study are consistent with the hypothesis that astroglial cells could be involved in demyelination processes occurring in the HTLV-I associated neurological disorders, such as human associated myelopathy and tropical spastic paraparesis.