Human T-lymphotropic Virus Type I Tax Research Articles

Polymorphism in the interleukin-10 promoter affects both provirus load and the risk of human t lymphotropic virus type I (HTLV-I) associated myelopathy/tropical spastic paraparesis

To investigate candidate genes that influence the risk of HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP), we analyzed 6 single nucleotide polymorphisms (SNP) in the interleukin-10 (IL-10) promoter region. METHODS: 280 cases of HAM/TSP patients and 255 HTLV-I seropositive asymptomatic carriers (HCs) from Kagoshima, Japan were studied. All subjects gave written informed consent and the study approved by local ethics committee. PCR-RFLP method used for SNP typing. HTLV-I provirus load was measured by quantitative PCR. RESULTS: The IL-10 -592A/C SNP showed a significant difference in allele frequency between HAM/TSP patients and HCs (p=0.014). Possession of the IL-10 -592 A allele was associated with a >2-fold reduction in the odds of HAM/TSP (2p=0.011, OR=0.50). This effect remains significant even after taking into account the other two known predictors such as provirus load and HLA-A*02 genotype. Given the OR and the observed frequency of the IL-10 -592 A allele, we can estimate that IL-10 -592 A allele prevents 44.7%( 13.1%SD) of potential cases of HAM/TSP in the study population. The presence of the IL-10 592 A allele is also a significant predictor of lower provirus load in the entire cohort (p=0.001). Furthermore, HTLV-I Tax transactivates the IL-10 promoter in the human T-cell line Jurkat and this transactivation was higher with the IL-10 -592 C allele than the A allele. Among more than 90 non-HLA candidate gene loci we have so far examined, IL-10 -592 A/C SNP is the only non-HLA candidate gene locus associated with a significant reduction in both the provirus load and the risk of HAM/TSP. These data demonstrate that the IL-10 -592 A allele influences the provirus load in HTLV-I infected individuals, and defines a further component of the genetic susceptibility to HAM/TSP.

Dysregulation of TGF-β signaling and regulatory and effector T-cell function in virus-induced neuroinflammatory disease

AbstractWe previously demonstrated that CD4+CD25+ T regulatory cells (Tregs), important for the maintenance of immune tolerance and prevention of autoimmune disease, from patients with human T lymphotropic virus type I (HTLV-I)–associated myelopathy/tropical spastic paraparesis (HAM/TSP) exhibit reduced Foxp3 expression and Treg suppressor function compared with healthy donors. Since TGF-β signaling has been previously reported to be critical for both Foxp3 expression and Treg function, we examined whether this signaling pathway was dysregulated in patients with HAM/TSP. Levels of TGF-β receptor II (TGF-βRII) as well as Smad7 (a TGF-β–inducible gene) were significantly reduced in CD4+ T cells in patients with HAM/TSP compared with healthy donors, and the expression of TGF-βRII inversely correlated with the HTLV-I tax proviral load. Importantly, both CD4+CD25+ and CD4+CD25− T cells from HAM/TSP patients exhibited reduced TGF-βRII expression compared with healthy donors, which was associated with functional deficits in vitro, including a block in TGF-β–inducible Foxp3 expression that inversely correlated with the HTLV-I tax proviral load, loss of Treg suppressor function, and escape of effector T cells from Treg-mediated control. This evidence suggests that a virus-induced breakdown of immune tolerance affecting both regulatory and effector T cells contributes to the pathogenesis of HAM/TSP.

HTLV-I Production Based on Activation of Integrin/Ligand Signaling in HTLV-I-Infected T Cell Lines Derived from HAM/TSP Patients

Objective: Activity of integrin/ligand signaling leading to activation of small GTPases might regulate the efficiency of cell-to-cell spread of human T lymphotropic virus type I (HTLV-I) through the virological synapse. We compared both activity of small GTPases and involvement of integrin/ligand signaling in extracellular release of HTLV-I virions between each three HTLV-I-infected T cell lines derived from HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) patients and from other origins as a control. Methods: Activity of small GTPases (Rho, Rac and Cdc42) was analyzed by pull-down assay with suppressive effect of both HTLV-I production and HTLV-I tax mRNA expression by anti-integrin-blocking antibodies. Results: All small GTPases were strongly activated in all cell lines derived from HAM/TSP patients, but not in control cell lines except one cell line. Treatment of all cell lines derived from HAM/TSP patients, but not all control cell lines, with anti-integrin-blocking antibodies significantly suppressed the level of HTLV-I p19 antigen in culture supernatants without downregulation of HTLV-I tax mRNA expression. Conclusion: Significant involvement with integrin/ligand signaling in extracellular release of HTLV-I virions in cell lines derived from HAM/TSP patients suggests that HTLV-I-infected cells in HAM/TSP patients have the potential for the efficient spread of HTLV-I to uninfected cells.

Thymus-derived leukemia-lymphoma in mice transgenic for the Tax gene of human T-lymphotropic virus type I

Adult T-cell leukemia-lymphoma (ATLL) is a group of T-cell malignancies caused by infection with human T-lymphotropic virus type I (HTLV-I). Although the pathogenesis of ATLL remains incompletely understood, the viral regulatory protein Tax is centrally involved in cellular transformation. Here we describe the generation of HTLV-I Tax transgenic mice using the Lck proximal promoter to restrict transgene expression to developing thymocytes. After prolonged latency periods, transgenic mice developed diffuse large-cell lymphomas and leukemia with clinical, pathological and immunological features characteristic of acute ATLL. Transgenic mice were functionally immunocompromised and they developed opportunistic infections. Fulminant disease also developed rapidly in SCID mice after engraftment of lymphomatous cells from transgenic mice. Flow cytometry showed that the cells were CD4(-) and CD8(-), but CD44(+), CD25(+) and cytoplasmic CD3(+). This phenotype is indicative of a thymus-derived pre-T-cell phenotype, and disease development was associated with the constitutive activation of NF-kappaB. Our model accurately reproduces human disease and will provide a tool for analysis of the molecular events in transformation and for the development of new therapeutics.

Interferon‐β1a therapy in human T‐lymphotropic virus type I–associated neurologic disease

Human T-lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is an immune-mediated inflammatory disorder of the central nervous system. Immune activation in the host, which results from high levels of persistent antigenic stimulation and from transactivation of host immunoregulatory genes by HTLV-I, appears important in the pathogenesis of HAM/TSP. In a single-center, open-label trial, 12 patients with HAM/TSP were treated with doses of interferon-beta1a of up to 60mug twice weekly, based on its antiviral and immunomodulatory effects. Primary end points were immunological and virological measures that are potential biomarkers for HAM/TSP. Interferon-beta1a therapy reduced the HTLV-I tax messenger RNA load and the frequency of potentially pathogenic HTLV-I-specific CD8(+) cells. The HTLV-I proviral DNA load remained unchanged. Spontaneous lymphoproliferation, a marker of T-cell activation in HAM/TSP, also was reduced. Some measures of motor function were improved, and no significant clinical progression occurred during therapy. These results indicate that interferon-beta1a may beneficially affect the immune mechanisms central to the pathogenesis of HAM/TSP.

Clinicopathological and virological analyses of familial human T-lymphotropic virus type I–associated polyneuropathy

Human T-lymphotropic virus type I (HTLV-I) is known to be the causative agent of the chronic myelopathy, HTLV-I--associated myelopathy (HAM), and on rare occasions infection is also associated with the development of polyneuropathy. Here the authors present an HTLV-I--positive family of whom four members developed a chronic demyelinating polyneuropathy without HAM. Four female patients in a family from Hokkaido in Japan developed distal dominant paresthesia and muscle weakness in the second and third decades of their life. Neurological findings at ages ranging from 50 to 65 years included mild painful sensorimotor disturbances with atrophy of the distal parts of the extremities but without pyramidal signs or hyperactive tendon reflexes. Magnetic resonance imaging (MRI) findings of brain and spinal cord were unremarkable. Serum HTLV-I antibody levels were elevated at 1:8192 to 1:32,768, whereas those in cerebrospinal fluid were low at 1:4 to 1:8. Electrophysiological studies revealed polyphasic compound muscle action potentials with denervation potentials on nerve conduction studies and neurogenic patterns by electromyography, which were consistent with signs of chronic motor dominant demyelinating polyneuropathy. Sural nerve biopsy showed decreased myelinated fibers, occurrence of globule formation, myelin ovoid and remyelinated fibers, and an infiltration of CD68-positive macrophages with occasional CD4-positive T cells in the nerve fascicles. The polyneuropathy was responsive to steroid therapy. Analyses of serological human leukocyte antigen (HLA) types indicated that none of the patients possessed a high-risk HLA type known to be associated with adult T-cell leukemia (ATL), whereas they did have high responsive alleles to HTLV-I env similar to that observed in HAM. Nucleotide sequence analysis of the HTLV-I tax region demonstrated the B subgroup in all patients. This study suggests that HTLV-I infection can result in the development of a familial form of polyneuropathy that is associated with distinct HLA class I alleles, which might possibly involve a distinct virus subtype.

HTLV-I Tax directly binds the Cdc20-associated anaphase-promoting complex and activates it ahead of schedule

Expression of the human T lymphotropic virus type I (HTLV-I) transactivator/oncoprotein, Tax, leads to faulty mitosis as reflected by chromosome aneuploidy, cytokinesis failure, and formation of micro- and multinucleated cells. Here we show that HTLV-I-transformed T cells progress through S/G(2)/M phases of the cell cycle with a delay. This delay is correlated with a decrease in the levels of cyclin A, cyclin B1, and securin. In tax-expressing cells, the Cdc20-associated anaphase promoting complex (APC(Cdc20)), an E3 ubiquitin ligase that controls metaphase to anaphase transition, becomes active before cellular entry into mitosis as evidenced by premature cyclin B1 polyubiquitination and degradation during S/G(2). Consistent with the notion that Tax activates APC(Cdc20) directly, Tax is found to coimmunoprecipitate with Cdc20 and Cdc27/APC3. The APC(Cdc20) activity prematurely activated by Tax remains sensitive to spindle checkpoint inhibition. Unscheduled activation of APC(Cdc20) by Tax provides an explanation for the mitotic abnormalities in HTLV-I-infected cells and is likely to play an important role in the development of adult T cell leukemia.

HTLV-I Tax induces and associates with Crk-associated substrate lymphocyte type (Cas-L)

Crk-associated substrate lymphocyte type (Cas-L) is a docking protein that is heavily tyrosine phosphorylated by the engagement of beta1 integrins in T cells. In the present study, we attempted to evaluate the role of Cas-L in the pathophysiology of adult T-cell leukemia (ATL). Examination of peripheral blood mononuclear cells from ATL patients as well as ATL-derived T cell lines showed an elevation of Cas-L in these cells. We showed that tyrosine phosphorylation as well as expression of Cas-L was markedly elevated through the induction of human T-lymphotropic virus type I (HTLV-I) Tax in JPX-9 cells, with these cells showing marked motile behavior on the ligands for integrins. We next performed yeast two-hybrid screening of cDNA library from an HTLV-I-transformed T cell line, which resulted in the identification of Tax as a putative binding partner for Cas-L. Co-precipitation experiments revealed that the serine-rich region of Cas-L might serve as the binding site with the highest affinity for Tax. Co-localization study showed that Tax and Cas-L partly merged in the cytoplasm. Finally, we showed that exogenous Cas-L inhibited Tax-mediated transactivation of nuclear factor kappaB (NF-kappaB), while Tax-independent activation of NF-kappaB remained intact, hence indicating that Cas-L might specifically regulate Tax-NF-kappaB pathway.

Cas-L associates with human T-lymphotropic virus type I Tax and regulates its transactivation of NF-κB: possible role of Cas-L in pathophysiology of rheumatoid arthritis

The Crk-associated substrate lymphocyte type (Cas-L) is a docking protein that is heavily tyrosine phosphorylated by FAK and Src family kinases upon the engagement of β1 integrins in T cells. Transfection of Cas-L into Jurkat cells markedly enhances cell motility and IL-2 production by engagement of β1 integrins through its tyrosine phosphorylation. These results clearly indicate the involvement of Cas-L in β1-integrin-mediated costimulation of signal transduction and cell migration. We have recently reported that expression of Cas-L is markedly elevated in human T-lymphotropic virus type I (HTLV-I) tax transgenic mouse, a murine model for rheumatoid arthritis, as well as in rheumatoid arthritis patients. In the present study, we show the interaction of Cas-L and Tax, and its biological significance in detail. We initially found that tyrosine phosphorylation as well as the expression of Cas-L was markedly elevated through the induction of HTLV-I Tax protein in JPX-9 cells, in which Tax is induced under the control of metallothionein promoter. Biochemical study showed that autophosphorylation of Src family PTKs, fyn and lck, were significantly enhanced in correlation to tyrosine phosphorylation of Cas-L. Consistent with our previous result, it was revealed that those cells had remarkably increased motile behavior on a fibronectin-coated Transwell insert. A two-hybrid screen for Cas-L binding proteins resulted in identification of Tax as one of the candidates for Cas-L binding partners. We subsequently confirmed protein–protein interaction of Cas-L and Tax using an overexpression experiment and HTLV-I transformed T-cell lines. Finally, expression of Cas-L was found to inhibit Tax-mediated transactivation of NF-κB, whereas it has virtually no effects on Tax-mediated transactivation of HTLV-I LTR. To date, HTLV-I has been associated with a variety of diseases affecting organs other than malignancies arising from the lymphoid system. Those chronic inflammatory diseases involve the nervous system in HTLV-I-associated myelopathy, the eyes in HTLV-I-associated uveitis, the salivary glands in Sjogren's syndrome, and the articular joints in the case of HTLV-I-associated arthropathy. These results may present the basis for a pathological role as well as for therapeutic application of Cas-L in HTLV-I-related inflammatory diseases.

Cross-reactivity between immunodominant human T lymphotropic virus type I tax and neurons: implications for molecular mimicry.

Human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is associated with immunoreactivity to HTLV-I tax. Antibodies isolated from patients with HAM/TSP and monoclonal antibodies (MAbs) to HTLV-I tax stained neurons. In neuronal extracts, HAM/TSP immunoglobulin G identified heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) as the autoantigen. Importantly, tax MAbs reacted with hnRNP A1. To identify the epitope recognized by the tax MAbs, the fine epitope specificity of the antibodies was determined using overlapping peptides. This analysis identified an epitope at the C-terminus (tax(346-353)), which overlaps a human immunodominant domain. Preincubation of this peptide with tax MAbs inhibited antibody binding to tax, hnRNP A1, and neurons. This indicates that a cross-reactive immune response between HTLV-I tax and neuronal hnRNP A1 is contained within the human immunodominant epitope of tax and suggests that molecular mimicry plays a role in the pathogenesis of HAM/TSP.

Selected cytotoxic T lymphocytes with high specificity for HTLV-I in cerebrospinal fluid from a HAM/TSP patient.

Human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic inflammatory disease of the spinal cord in which HTLV-I Tax-specific cytotoxic T lymphocytes (CTL) have been suggested to be immunopathogenic. However, it is unknown whether the HTLV-I-specific CTL in the central nervous system differ from those in the periphery. We investigated functional T-cell receptor diversity in HTLV-I Tax11-19-specific CTL clones derived from peripheral blood and cerebrospinal fluid (CSF) of a HAM/TSP patient using analogue peptides of the viral antigen. CTL responses to the analogue peptides varied between T-cell clones, however, CTL clones from CSF showed limited recognition of the peptides when compared to those from peripheral blood. This suggests that CTL with highly focused specificity for HTLV-I Tax accumulate in the CSF and may contribute to the pathogenesis of HAM/TSP. Furthermore, this study provides a rationale for analogue peptide-based immunotherapeutic strategies focusing on the immunopathogenic T-cells in HTLV-I-associated neurologic disease.

Transcriptional Activation of JC Virus by Human T-lymphotropic Virus Type I Tax Protein in Human Neuronal Cell Lines

Polyomavirus JC (JCV) causes the human demyelinating disease, progressive multifocal leukoencephalopathy (PML). The recent demonstration of cases of PML in association with human T-lymphotropic virus type I (HTLV-I) infection prompted us to examine whether the HTLV-I-encoded regulatory protein Tax activates JCV transcription. By employing a dual luciferase assay, we initially found that the expression of Tax activated the transcriptional potential of both early and late promoters of JCV in human neuronal but not in non-neuronal cells. We subsequently analyzed the mechanism of Tax-induced activation of the JCV promoter in neuronal cells with the following results: 1) the JCV promoter that lacks the NF-kappaB-binding motif could not be activated by Tax; 2) the overexpression of IkappaBalpha abolished Tax-induced transcriptional activation of the JCV promoter; 3) a Tax mutant (M22) lacking the potential for activation via the NF-kappaB pathway did not activate the JCV promoter. Furthermore, Tax enhances the gene expression of JCV T antigen and VP1. We examined mechanisms of the cell-specific activation of the JCV promoter by Tax. Electrophoretic mobility shift assay demonstrated the presence of Tax-bound protein(s) that were specifically present in non-neuronal cells. This study is the first demonstration of the activation of JCV promoter by HTLV-I Tax in an NF-kappaB-dependent manner.

An altered peptide ligand antagonizes antigen-specific T cells of patients with human T lymphotropic virus type I-associated neurological disease.

Human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is an inflammatory neurologic disease associated with HTLV-I infection, in which chronically activated, HTLV-I-specific CD8+ CTL have been suggested to be immunopathogenic. In HLA-A2 HAM/TSP patients, CD8+ HTLV-I-specific CTLs recognize an immunodominant peptide of the HTLV-I Tax protein, Tax11-19. We examined the functional outcome on activation of both cloned peripheral blood and cerebrospinal spinal fluid-derived CTL and bulk PBMC from HAM/TSP patients by altered peptide ligands (APL) derived from HTLV-I Tax11-19. In CTL clones generated from PBMC and CSF of HLA-A2 HAM/TSP patients, an APL substituted at position 5 significantly decreased CTL responses when compared with the native peptide. Moreover, these ligands were also shown to inhibit CTL responses to the native peptide in bulk PBMC of HLA-A2 HAM/TSP patients. These data suggest that a modification of an antigenic peptide at the central position can manipulate the T cell responses in bulk PBMC from different individuals with an inflammatory disease. Additionally, these results have implications for the potential use of APL-based immunotherapy in this T cell-mediated CNS disease.

Absence of human T-lymphotropic virus type I tax sequences in a population of normal blood donors in the Baltimore, MD/Washington, DC, area: results from a multicenter study.

It was reported recently that sequences corresponding to the human T-lymphotropic virus type I (HTLV-I) tax gene were detected in peripheral blood mononuclear cells from 8 to 11 percent of healthy blood donors without detectable antibodies to HTLV-I. A multicenter blind study was conducted to determine if these results could be independently confirmed. Specimens were collected from 100 anti-HTLV-I-negative healthy blood donors and from 11 anti-HTLV-I- or anti-HTLV-II-positive individuals. All samples were coded and distributed to each of four independent testing laboratories for polymerase chain reaction analysis to detect sequences of the HTLV-I or HTLV-II tax gene, using detailed procedures specified by the laboratory reporting the original observation. Each laboratory also tested a dilution panel of a plasmid containing HTLV-I tax to determine the analytical sensitivity of the procedure. The analytical sensitivity of the screening methods permitted detection of as few as 1 to 10 copies of the tax gene. However, HTLV-I tax sequences could not be detected in any of the anti-HTLV-I-negative blood donors at more than one test site. HTLV-I tax sequences appear not to be present in this population of 100 blood donors negative for anti-HTLV-I.

Expression of murine HOXD9 during embryonic joint patterning and in human T lymphotropic virus type I tax transgenic mice with arthropathy resembling rheumatoid arthritis.

To characterize the expression of murine HOXD9 during normal joint development and in arthritic joints of human T lymphotropic virus type I (HTLV-I) tax transgenic mice and the role of HTLV-I tax in HOXD9 expression. Expression of HOXD9, HOXD1O, HOXD11, HOXD12, and HOXD13 genes in joint tissues at the ankle/foot regions of mouse embryos at day 10 to day 18 of gestation (E10-E18) and neonates within 10 days after birth was determined by reverse transcriptase-polymerase chain reaction and in situ reverse transcription methods. Adult synovial tissues from 5 HTLV-I tax transgenic mice with chronic polyarthritis and 4 nontransgenic (normal) mice were also examined for expression of these HOXD genes. The effect of HTLV-I on HOXD9 expression in cultured synoviocytes was studied by in vitro infection and transfection experiments. Expression of HOXD9 was detected in embryonic joints, preferentially on articular cartilage, only during the early stages of joint development (up to E15), whereas other HOXD genes were expressed throughout the embryonic and neonatal stages. In adult mice, transcripts of HOXD9 were specifically detected in synovial tissues from 4 of 5 arthritic mice, especially in the lining and sublining synovial cells, but not in synovial tissues of normal mice. Activation of HOXD9 was observed in cultured synoviocytes infected with HTLV-I in vitro as well as in those transfected with HTLV-I tax. Our findings suggest that HOXD9 is involved not only in the early stages of normal joint development, but may also be involved in the pathologic process of arthritis. HTLV-I tax appeared as an activator of this HOX gene in cultured synoviocytes.

AN ALTERED PEPTIDE LIGAND ANTAGONIZES ANTIGEN-SPECIFIC CD8+ CTL IN PERIPHERAL BLOOD OF HAM/TSP PATIENTS

P065 Human T lymphotropic virus type I (HTLV-I) associated myelopathy/ tropical spastic paraparesis (HAM/TSP) is an inflammatory neurologic disease associated with HTLV-I infection, in which chronically activated, HTLV-I-specific CD8+ cytotoxic T lymphocytes (CTLs) have been suggested to be immunopathogenic. In HLA-A2 HAM/TSP patients, CD8+ HTLV-I specific CTLs recognize an HTLV-I immunodominant peptide of the HTLV-I tax protein, tax 11-19. We examined the T-cell receptor (TCR) agonism/antagonism in HTLV-I tax 11-19-specific CTL in both cloned CTLs and bulk peripheral blood lymphocytes (PBL) from four HLA-A2 HAM/TSP patients using alanine substituted peptides at the TCR contact residues of the HTLV-I tax peptide. In CTL clones generated from PBL and cerebrospinal fluid of HLA-A2 HAM/TSP patients, an altered peptide ligand (APL) substituted at position five significantly decreased the CTL responses when compared to the native peptide. Moreover, this ligand were also shown to inhibit CTL responses to the native peptide in bulk PBL of HLA-A2 HAM/TSP patients. These data suggest that a modification of antigenic peptide at the central position can manipulate the T cell responses in bulk PBL from different individuals with an inflammatory disease, implying a potential immunotherapy using an APL in antigen-specific T-cell mediated diseases.

Tumours derived from HTLV-I tax transgenic mice are characterized by enhanced levels of apoptosis and oncogene expression.

In order to investigate the role that the human T-lymphotropic virus type I (HTLV-I) tax oncogene plays in apoptosis and transformation in vivo, four lines of HTLV-I tax transgenic mice were generated under the regulatory control of the CD3-epsilon promoter-enhancer sequence. These mice develop a variety of phenotypes including mesenchymal tumours, which develop at wound sites, and salivary and mammary adenomas. In situ DNA fragment labelling and immunocytochemical analysis of these tumours reveals that they display enhanced levels of apoptosis, which is associated with elevated levels of Myc, Fos, Jun, and p53 protein expression. Furthermore, double immunofluorescent staining shows that Tax expression and apoptosis co-localize, indicating that Tax expression is closely associated with apoptosis in vivo.

Neuronal molecular mimicry in immune-mediated neurologic disease.

Molecular mimicry is implicated in the pathogenesis of autoimmune diseases such as diabetes mellitus, rheumatoid arthritis, and multiple sclerosis (MS). Cellular and antibody-mediated immune responses to shared viral-host antigens have been associated with the development of disease in these patients. Patients infected with human T-lymphotropic virus type I (HTLV-I) develop HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP), an immune-mediated disorder of the central nervous system (CNS) that resembles some forms of MS. Damage to neuronal processes in the CNS of HAM/TSP patients is associated with an activated cellular and antibody-mediated immune response. In this study, IgG isolated from HAM/TSP patients was immunoreactive with uninfected neurons and this reactivity was HTLV-I specific. HAM/TSP IgG stained uninfected neurons in human CNS and cell lines but not nonneuronal cells. Neuronal western blots showed IgG reactivity with a single 33-kd band in all HAM/TSP patients tested. By contrast, no neuron-specific IgG reactivity could be demonstrated from HTLV-I seronegative controls and, more important, from HTLV-I seropositive, neurologically asymptomatic individuals. Both immunocytochemical staining and western blot reactivity were abolished by preincubating HAM/TSP IgG with HTLV-I protein lysate but not by control proteins. Staining of CNS tissue by a monoclonal antibody to HTLV-I tax (an immunodominant HTLV-I antigen) mimicked HAM/TSP IgG immunoreactivity. There was no staining by control antibodies. Absorption of HAM/TSP IgG with recombinant HTLV-I tax protein or preincubation of CNS tissue with the monoclonal antibody to HTLV-I tax abrogated the immunocytochemical and western blot reactivity of HAM/TSP IgG. Furthermore, in situ human IgG localized to neurons in HAM/TSP brain but not in normal brain. These data indicate that HAM/TSP patients develop an antibody response that targets uninfected neurons, yet reactivity is blocked by HTLV-I, suggesting viral-specific autoimmune reactivity to the CNS, the damaged target organ in HAM/TSP.

Demonstration of Human T Lymphotropic Virus Type I (HTLV-I) Tax-Specific CD8+ Lymphocytes Directly in Peripheral Blood of HTLV-I-Associated Myelopathy/Tropical Spastic Paraparesis Patients by Intracellular Cytokine Detection

Human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is an inflammatory neurologic disease caused by HTLV-I infection and has been associated with elevated levels of several proinflammatory cytokines in both serum and cerebrospinal fluid. It is unknown what kind of cells secrete these cytokines and if HTLV-I Ags are associated with this phenomenon. Here, we investigated the expression of cytokines in PBL from eight HAM/TSP patients, nine HTLV-I-infected asymptomatic carriers, and seven healthy controls by flow cytometry combined with intracellular cytokine staining. PBL were cultured with brefeldin A without mitogen and IL-2 for 14 h. Under these conditions, CD8+ cells produced proinflammatory cytokines including IFN-gamma, TNF-alpha, and IL-2, which were significantly elevated in HAM/TSP patients. The proportion of CD8+ cells producing IFN-gamma in HAM/TSP patients, asymptomatic carriers, and healthy controls were, on average, 4.9, 0.4, and 0.3%, respectively. IFN-gamma production by these CD8+ cells was suppressed by anti-HLA-class I Ab. Purified CD8+ cells from an HLA-A2 HAM/TSP patient produced IFN-gamma by cocultivation with autologous CD4 cells, the main reservoir of HTLV-I in vivo, or allogenic HLA-A2+ B cells pulsed with a known immunodominant HTLV-I tax peptide. These data suggest that high levels of circulating HTLV-I-specific CD8+ T lymphocytes have the potential to produce proinflammatory cytokines and may promote inflammatory responses to HTLV-I in HAM/TSP patients.

Detection of HTLV-I in peripheral blood lymphocytes from patients with chronic HTLV-I-associated myelopathy/tropical spastic paraparesis and asymptomatic carriers by PCR-in situ hybridization

Less than 5% of people infected with human T-lymphotropic virus type I (HTLV-I) develop HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP), a chronic progressive neurologic disease. A number of factors have been implicated in the development of HAM/TSP including heterogeneity of viral sequences, host-genetic background, viral-specific cellular immune responses and viral load. This study examined the presence of HTLV-1 tax DNA in peripheral blood lymphocytes (PBL) from 2 chronic HAM/TSP patients and 2 asymptomatic HTLV-I carriers by using PCR-in situ hybridization (PCR-ISH) for the in situ presence of proviral HTLV-I tax DNA. By this technique, rare PBL from these HTLV-I-infected individuals contained HTLV-I DNA. PCR-ISH did not detect any difference in the number of infected cells between HAM/TSP patients and asymptomatic carriers. Copyright 1997 S. Karger AG, Basel