Infection of human synovial cells by human T cell lymphotropic virus type I. Proliferation and granulocyte/macrophage colony-stimulating factor production by synovial cells

Effect of HTLV-1 Infection on the Clinical Course of Patients with Rheumatoid Arthritis

Human T-cell leukemia virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia/lymphoma (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The effects of HTLV-1 on health are not fully elucidated. Epidemiological studies have shown that the prevalence of HTLV-1 infection is high in patients with rheumatic diseases. The prevalence of comorbidities, such as Sjögren’s syndrome and rheumatoid arthritis (RA), is higher in patients with HAM/TSP than the in general population. Studies have shown the effects of HTLV-1-infection on the clinical course of RA. Major questions on the association between HTLV-1 infection and RA: (1) Is it possible that HTLV-1 infection causes RA? (2) Do patients with RA who are infected with HTLV-1 have different clinical features? (3) Are immunosuppressants associated with an increased prevalence of HAM/TSP or ATL in RA patients with HTLV-1 infection? Is ATL an immunosuppressive therapy-associated lymphoproliferative disorder? No large-scale studies have investigated the incidence of ATL in patients with RA. However, several studies have reported the development of ATL in patients with RA who have HTLV-1 infection. This review aimed to shed light on the association between HTLV-1 infection and RA and summarize the unmet medical needs of RA patients with HTLV-1 infection.

The Association of Increase of Human T-Cell Leukemia Virus Type-1 (HTLV-1) Proviral Load (PVL) With Infection in HTLV-1-Positive Patients With Rheumatoid Arthritis: A Longitudinal Analysis of Changes in HTLV-1 PVLs in a Single Center Cohort Study

Objective

We evaluated changes of HTLV-1 proviral loads (PVLs) during treatment for rheumatoid arthritis (RA) and investigated whether these changes affect the clinical course in HTLV-1-positive RA patients.

Methods

A total of 41 HTLV-1-positive RA patients were analyzed. Their clinical picture including disease activity [Disease Activity Score in 28 joints-erythrocyte sedimentation rate (DAS28-ESR), DAS28-CRP, simplified disease activity index (SDAI), and clinical disease activity index (CDAI)] and comorbidity were evaluated over a 2-year period. PVLs from peripheral blood mononuclear cells were investigated by real-time polymerase chain reaction (PCR). We investigated whether HTLV-1 PVLs is altered, or which clinical characteristics affect changes of HTLV1-PVLs during 2-year treatment.

Results

Clinical disease activity was not changed during the 2-year observational period. The mean HTLV-1 PVL value change from baseline to 2 years was -1.2 copies/1000 PBMCs, which was not statistically significant. No baseline clinical characteristics influenced changes in HTLV-1 PVL. However, a numerical change of HTLV-1 PVLs was increased in 4 patients initiating the new biological/targeted synthetic disease-modifying antirheumatic drugs (b/tsDMARDs) at 2−10 months after starting the new b/ts DMARDs (numerical increase was 24.87 copies/1000 PBMCs). Infection occurred in 4 patients, and 3 of those patients showed an increased HTLV-1 PVL. Univariate analysis revealed an association between increase of HTLV-1 PVL and incidence of infection.

Conclusions

Over 2 years, HTLV-1 PVL did not significantly change in our HTLV-1-positive RA patients. Individual changes in HTLV-1 PVL were correlated with incidence of infection but not disease activity which indicate that we may take precaution toward infection at the uptick of HTLV-1 PVL in HTLV-1-positive RA patients.

Does HTLV-1 Infection Show Phenotypes Found in Sjögren's Syndrome?

Viruses are a possible cause for Sjögren's syndrome (SS) as an environmental factor related to SS onset, which exhibits exocrine gland dysfunction and the emergence of autoantibodies. Although retroviruses may exhibit lymphocytic infiltration into exocrine glands, human T-cell leukemia virus type 1 (HTLV-1) has been postulated to be a causative agent for SS. Transgenic mice with HTLV-1 genes showed sialadenitis resembling SS, but their phenotypic symptoms differed based on the adopted region of HTLV-1 genes. The dominance of tax gene differed in labial salivary glands (LSGs) of SS patients with HTLV 1-associated myelopathy (HAM) and adult T-cell leukemia. Although HTLV-1 was transmitted to salivary gland epithelial cells (SGECs) by a biofilm-like structure, no viral synapse formation was observed. After infection to SGECs derived from SS patients, adhesion molecules and migration factors were time-dependently released from infected SGECs. The frequency of the appearance of autoantibodies including anti-Ro/SS-A, La/SS-B antibodies in SS patients complicated with HAM is unknown; the observation of less frequent ectopic germinal center formation in HTLV-1-seropositive SS patients was a breakthrough. In addition, HTLV-1 infected cells inhibited B-lymphocyte activating factor or C-X-C motif chemokine 13 through direct contact with established follicular dendritic cell-like cells. These findings show that HTLV-1 is directly involved in the pathogenesis of SS.

Association of human T-cell leukemia virus type 1 with prevalent rheumatoid arthritis among atomic bomb survivors: A cross-sectional study

Previous studies have suggested that human T-cell leukemia virus type 1 (HTLV-1) might act as a pathogen in rheumatoid arthritis (RA), but epidemiological evidence of an association is scarce. We measured anti-HTLV-1 antibodies among Nagasaki atomic bomb survivors to determine whether HTLV-1 is related to RA and whether radiation exposure is associated with HTLV-1 and RA prevalence.This is a cross-sectional study among atomic bomb survivors who participated in biennial health examinations from 2006 to 2010. Serum levels of anti-HTLV-1 antibodies were measured using a chemiluminescent enzyme immunoassay and confirmed by Western blotting. Association between HTLV-1 and RA was analyzed by a logistic regression model.Of 2091 participants (women 61.5%; median age, 73 years), 215 (10.3%) had anti-HTLV-1 antibodies. HTLV-1 prevalence was higher among women (13.1% vs 5.8%; P < .001). Twenty-two participants (1.1%) were diagnosed with RA. HTLV-1 prevalence among RA participants was significantly higher than that among non-RA participants (27.3% vs 10.1%; P = .020). After adjustment for age, sex, and hepatitis C virus infection, HTLV-1 was significantly associated with prevalent RA (odds ratio, 2.89; 95% confidence interval, 1.06, 7.03). There was no association between radiation dose and either the prevalence of HTLV-1 or RA.This study, among a well-defined group of atomic bomb survivors, suggests that HTLV-1 is associated with RA.

Tocilizumab has no direct effect on cell lines infected with human T-cell leukemia virus type 1

Objective

It remains unclear whether human T-cell leukemia virus type 1 (HTLV-1) infection influences therapeutic responses in patients with rheumatic diseases and whether immunosuppressive treatments increase the risk of HTLV-1-related complications in HTLV-1 carriers with rheumatic diseases. We examined the effects of tocilizumab (TCZ), an interleukin (IL)-6 receptor antagonist, on two HTLV-1-infected T-cell lines (HCT-5 and MT-2) in vitro.

Methods

We evaluated production of cytokines and chemokines, expression of HTLV-I associated genes, HTLV-1 proviral load (PVL), expression of HTLV-1 structural proteins, and apoptosis.

Results

There were no significant differences in cytokine and chemokine levels in the culture supernatants of HCT-5 and MT-2 cells treated with phosphate-buffered saline (PBS) or TCZ. No significant differences were detected in mRNA abundance of Tax or HBZ, PVL, expression of the HTLV-1 structural protein GAG, or apoptosis among HCT-5 and MT-2 cells treated with PBS or TCZ.

Conclusions

TCZ had no effect the cytokine profiles, HTLV-1 gene and protein expression, PVL, or apoptosis in HTLV-1-infected T-cell lines. Thus, TCZ treatment has no effect on HTLV-1 infection in vitro.

Inhibitory effect of HTLV-1 infection on the production of B-cell activating factors in established follicular dendritic cell-like cells

Introduction

The low frequency of ectopic germinal center in labial salivary glands of patients with human T‐cell leukemia virus type 1 (HTLV‐1) antibody‐positive Sjögren's syndrome (SS) suggests that HTLV‐1 has some effects on follicular dendritic cells (FDCs).

Methods

We used flow cytometry, immunofluorescence, and enzyme‐linked immunosorbent assays (ELISAs) to investigate the direct effect of HTLV‐1 on B‐cell activating factors produced by established FDC like cells obtained from excised human tonsils. We then measured the serum B‐cell activating factor (BAFF) and C‐X‐C motif ligand (CXCL) 13 concentrations of the HTLV‐1‐seropositive SS patients and the HTLV‐1‐seronegative SS patients by ELISA.

Results

Among the 31 isolated specimens, 22 showed morphological characteristics of FDCs. Day 2‐cultured specimens showed expressions of CD14, CD23, CD40, intracellular adhesion molecule‐1 (ICAM‐1), and vascular cell adhesion molecule‐1. After 2 weeks, 12 of these specimens expressed ICAM‐1, FDC, and fibroblast cell marker. Intracellular BAFF and CXCL13 were constitutively expressed regardless of stimulation. After direct coculture with the HTLV‐1‐infected T‐cell line HCT‐5 or MT‐2, the BAFF and CXCL13 expressions on the FDC‐like cells were decreased in accord with the increased number of HCT‐5 and MT‐2 cells with styliform change and without HTLV‐1 Gag protein expression. Interferons upregulated the concentration of BAFF (but not CXCL13) in the culture supernatant, which showed a declining trend under the presence of HCT‐5 or MT‐2. The serum concentrations of BAFF and CXCL13 in the HTLV‐1‐seropositive SS patients were lower than those of the HTLV‐1 seronegative SS patients.

Conclusions

HTLV‐1 partially inhibited the BAFF and CXCL13 expressions of established FDC‐like cells.

HTLV-1 targets human placental trophoblasts in seropositive pregnant women

Human T cell leukemia virus type 1 (HTLV-1) is mainly transmitted vertically through breast milk. The rate of mother-to-child transmission (MTCT) through formula feeding, although significantly lower than through breastfeeding, is approximately 2.4%-3.6%, suggesting the possibility of alternative transmission routes. MTCT of HTLV-1 might occur through the uterus, birth canal, or placental tissues; the latter is known as transplacental transmission. Here, we found that HTLV-1 proviral DNA was present in the placental villous tissues of the fetuses of nearly half of pregnant carriers and in a small number of cord blood samples. An RNA ISH assay showed that HTLV-1-expressing cells were present in nearly all subjects with HTLV-1-positive placental villous tissues, and their frequency was significantly higher in subjects with HTLV-1-positive cord blood samples. Furthermore, placental villous trophoblasts expressed HTLV-1 receptors and showed increased susceptibility to HTLV-1 infection. In addition, HTLV-1-infected trophoblasts expressed high levels of viral antigens and promoted the de novo infection of target T cells in a humanized mouse model. In summary, during pregnancy of HTLV-1 carriers, HTLV-1 was highly expressed in placental villous tissues, and villous trophoblasts showed high HTLV-1 sensitivity, suggesting that MTCT of HTLV-1 occurs through the placenta.

Effectiveness and safety of non-tumor necrosis factor inhibitor therapy for anti-human T-cell leukemia virus type 1 antibody-positive rheumatoid arthritis

OBJECTIVES

Our previous study showed that the effectiveness of tumor necrosis factor (TNF) inhibitors was attenuated in anti-human T-cell leukemia virus type 1 (HTLV-1) antibody-positive patients with rheumatoid arthritis (RA). We aimed to evaluate the effectiveness and safety of non-TNF inhibitors in anti-HTLV-1 antibody-positive patients with RA.

METHODS

We reviewed patients with RA who received abatacept or tocilizumab as the first biologic agent. We used the data of patients treated with TNF inhibitors from our previous study to compare the effectiveness between the anti-HTLV-1 antibody-positive patients treated with TNF inhibitors and non-TNF inhibitors using the inverse probability of treatment weights (IPTW) method.

RESULTS

A total of 359 patients were divided into anti-HTLV-1 antibody-negative and -positive patients of 332 and 27, respectively. No statistically significant difference was observed in the change in the clinical disease activity index between the anti-HTLV-1 antibody-positive and -negative patients. The results using the IPTW method showed a significant association between the non-TNF inhibitors treatment and a better response. None of the patients developed adult T-cell leukemia/lymphoma or HTLV-1-associated myelopathy/tropical spastic paraparesis during the 24 weeks.

CONCLUSION

Our results indicate that non-TNF inhibitors treatment is safety, and the effectiveness is not attenuated also in anti-HTLV-1 antibody-positive patients.

Role of Viral Infections in the Pathogenesis of Sjögren's Syndrome: Different Characteristics of Epstein-Barr Virus and HTLV-1

Viruses are possible pathogenic agents in several autoimmune diseases. Sjögren’s syndrome (SS), which involves exocrine dysfunction and the appearance of autoantibodies, shows salivary gland- and lacrimal gland-oriented clinical features. Epstein-Barr virus (EBV) is the most investigated pathogen as a candidate that directly induces the phenotype found in SS. The reactivation of the virus with various stimuli induced a dysregulated form of EBV that has the potential to infect SS-specific B cells and plasma cells that are closely associated with the function of an ectopic lymphoid structure that contains a germinal center (GC) in the salivary glands of individuals with SS. The involvement of human T-cell leukemia virus type 1 (HTLV-1) in SS has been epidemiologically established, but the disease concept of HTLV-1-associated SS remains unexplained due to limited evidence from basic research. Unlike the cell-to-cell contact between lymphocytes, biofilm-like structures are candidates as the mode of HTLV-1 infection of salivary gland epithelial cells (SGECs). HTLV-1 can infect SGECs with enhanced levels of inflammatory cytokines and chemokines that are secreted from SGECs. Regardless of the different targets that viruses have with respect to affinitive lymphocytes, viruses are involved in the formation of pathological alterations with immunological modifications in SS.

Initial human T-cell leukemia virus type 1 infection of the salivary gland epithelial cells requires a biofilm-like structure

The initial phase of the human T cell leukemia virus-1 (HTLV-1) infection of salivary gland epithelial cells (SGECs) was examined. SGECs of patients with Sjögren's syndrome (SS) and non-SS subjects were co-cultured with the HTLV-1-infected cell line HCT-5 or MOLT-4, then immunofluorescence (IF), scanning and transmission electron microscopy (SEM/TEM) were employed. The extracellular matrix and linker proteins galectin-3, agrin, and tetherin were expressed on the surfaces of both HCT-5 and MOLT-4 cells. HTLV-1 Gag-positive spots were observed on adjacent SGECs after 1 h of co-culture with HCT-5. Both in subjects with and those without SS, agrin and tetherin were co-expressed with HTLV-1 Gag on SGECs after co-culture with HCT-5, although no polarization of HTLV-1 Gag and relevant molecules was observed. SEM showed HTLV-1 virions that were found on HCT-5 were observed in the interfaces between HCT-5 cells and SGECs. TEM imaging showed that HTLV-1 virions were transmitted to SGECs at the interface with thin film-like structure, while HTLV-1 virions were released from the surface of HCT-5 cells. No endogenous retroviruses were observed. These results showed that the initial phase of HTLV-1 infection toward SGECs of SS was mediated not by viral synapses, but by biofilm-like components.

What is the evidence for Sjögren's syndrome being triggered by viral infection? Subplot: infections that cause clinical features of Sjögren's syndrome

PURPOSE OF REVIEW

To clarify the involvement of viral infections in the pathogenesis of Sjögren's syndrome and to discuss whether viruses can be a trigger for the development of Sjögren's syndrome.

RECENT FINDINGS

Although some viruses are candidate triggers of Sjögren's syndrome, we focus on human T lymphotropic virus type I (HTLV-I). Clinicoepidemiological studies show a relationship between HTLV-I and Sjögren's syndrome with a low frequency of salivary gland damage in magnetic resonance imaging, autoantibody production and ectopic germinal center in HTLV-I-associated myelopathy (HAM) patients with Sjögren's syndrome. Our recent study showed that HTLV-I has the potential to infect salivary gland epithelial cells (SGECs). After a coculture of HCT-5 (an HTLV-I-infected T-cell line derived from the cerebrospinal fluid) of an HAM patient and SGECs, we observed time-dependent increases in the levels of soluble intracellular adhesion molecule1, interferon gamma-induced protein 10 kDa and regulated on activation, normal T-cell expressed and secreted. In addition, SGECs themselves express these molecules along with the expression of HTLV-I proteins.

SUMMARY

HTLV-I is involved in the pathogenesis of HTLV-I-seropositive patients with Sjögren's syndrome. By infecting CD4 T cells in vivo, HTLV-I induces specific clinicopathological conditions. In addition, HTLV-I-infected SGECs have the potential to augment the expression of molecules involved in cell adhesion, inflammation and migration.

Inflammatory manifestations of HTLV-1 and their therapeutic options

Human T lymphotropic virus type 1 (HTLV-1) is one of the most intriguing retroviruses infecting humans. Most commonly, infection remains undetected, since it does not cause obvious harm, yet in 4-9% of patients, this infection can be devastating, causing adult T-cell leukemia/lymphoma and/or HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP). This review concentrates on all inflammatory aspects of HTLV-1 infection: HAM/TSP, HTLV-1 associated uveitis, HTLV-1 associated conjunctivitis, sicca syndrome and interstitial keratitis, HTLV-1 associated Sjögren's syndrome, Hashimoto's thyroiditis and Graves' disease, HTLV-1 associated pulmonary disease, infective dermatitis associated with HTLV-1, HTLV-1 associated inflammatory myositis and HTLV-1 associated arthritis. With the exception of HAM/TSP treatment, studies of these conditions are sparse and even for HAM/TSP, the level of evidence is limited. While control or elimination of infection remains a goal, most therapy beyond symptomatic management is directed at the immune response to HTLV-1.

The immunobiology of viral arthritides

A large range of human viruses are associated with the development of arthritis or arthralgia. Although there are many parallels with autoimmune arthritides, there is little evidence that viral arthritides lead to autoimmune disease. In humans viral arthritides usually last from weeks to months, can be debilitating, and are usually treated with non-steroidal anti-inflammatory drugs, but with variable success. Viral arthritides likely arise from immunopathological inflammatory responses directed at viruses and/or their products residing and/or replicating within joint tissues. Macrophages recruited by monocyte chemoattractant protein-1 (MCP-1/CCL2) and activated by interferon, and proinflammatory mediators like tumour necrosis factor alpha, interferon gamma, interleukin-6 and interleukin-1beta appear to be common elements in this group of diseases. The challenge for new treatments is to target excessive inflammation without compromising anti-viral immunity. Recent evidence from mouse models suggests targeting MCP-1 or complement may emerge as viable new treatment options for viral arthritides.

Human T-cell leukemia virus type I infects human lung epithelial cells and induces gene expression of cytokines, chemokines and cell adhesion molecules

Background

Human T-cell leukemia virus type I (HTLV-I) is associated with pulmonary diseases, characterized by bronchoalveolar lymphocytosis, which correlates with HTLV-I proviral DNA in carriers. HTLV-I Tax seems to be involved in the development of such pulmonary diseases through the local production of inflammatory cytokines and chemokines in T cells. However, little is known about induction of these genes by HTLV-I infection in lung epithelial cells.

Results

We tested infection of lung epithelial cells by HTLV-I by coculture studies in which A549 alveolar and NCI-H292 tracheal epithelial cell lines were cocultured with MT-2, an HTLV-I-infected T-cell line. Changes in the expression of several cellular genes were assessed by reverse transcription-polymerase chain reaction, enzyme-linked immunosorbent assay and flow cytometry. Coculture with MT-2 cells resulted in infection of lung epithelial cells as confirmed by detection of proviral DNA, HTLV-I Tax expression and HTLV-I p19 in the latter cells. Infection was associated with induction of mRNA expression of various cytokines, chemokines and cell adhesion molecule. NF-κB and AP-1 were also activated in HTLV-I-infected lung epithelial cells. In vivo studies showed Tax protein in lung epithelial cells of mice bearing Tax and patients with HTLV-I-related pulmonary diseases.

Conclusion

Our results suggest that HTLV-I infects lung epithelial cells, with subsequent production of cytokines, chemokines and cell adhesion molecules through induction of NF-κB and AP-1. These changes can contribute to the clinical features of HTLV-I-related pulmonary diseases.

Human T cell leukemia virus type I-infected patients with Hashimoto's thyroiditis and Graves' disease

CONTEXT

Autoimmune thyroid diseases have been reported to be associated with human T cell leukemia virus type I (HTLV-I) infection. HTLV-I proviral load is related to the development of HTLV-I-associated myelopathy/tropical spastic paraparesis and has also been shown to be elevated in the peripheral blood of HTLV-I-infected patients with uveitis, arthritis, and connective tissue disease.

OBJECTIVE

The objective of the study was to evaluate the proviral load in HTLV-I-infected patients with Hashimoto's thyroiditis (HT) or Graves' disease (GD) and ascertain the ability of HTLV-I to infect thyroid cells.

PATIENTS AND METHODS

A quantitative real-time PCR assay was developed to measure the proviral load of HTLV-I in peripheral blood mononuclear cells from 26 HTLV-I-infected patients with HT, eight HTLV-I-infected patients with GD, or 38 asymptomatic HTLV-I carriers. Rat FRTL-5 thyroid cells were cocultured with HTLV-I-infected T cell line MT-2 or uninfected T cell line CCRF-CEM. After coculture with T cell lines, changes in Tax and cytokine mRNA expression were studied by RT-PCR.

RESULTS

HTLV-I proviral load was significantly higher in the peripheral blood of patients with HT and GD than asymptomatic HTLV-I carriers. In the peripheral blood from HTLV-I-infected patients with HT, HTLV-I proviral load did not correlate with the thyroid peroxidase antibody or thyroglobulin antibody titer. After coculture with MT-2 cells, FRTL-5 cells expressed HTLV-I-specific Tax mRNA. These cocultured FRTL-5 cells with MT-2 cells expressed IL-6 mRNA and proliferated more actively than those cocultured with CCRF-CEM cells.

CONCLUSION

Our findings suggest the role of the retrovirus in the development of autoimmune thyroid diseases in HTLV-I-infected patients.

Treatment for HTLV-I associated arthropathy: a case study and synovial tissue culture analysis

OBJECTIVE

There are few reports regarding the treatment of HTLV-I associated arthropathy (HAAP). This is a case study describing the treatment of a patient diagnosed with HAAP. We also analyzed the effects of various agents on cultured synovial tissue explants from the patient.

METHODS

Arthroscopic synovectomy of the left knee was performed. We investigated the effects of pirarubicin (THP), bestatin, betamethasone, and hyaluronic acid (HA) in synovial tissue culture to evaluate the efficacy of these medications.

RESULTS

Swelling and pain of the left knee was transiently diminished after synovectomy. However, bilateral swelling of the knees and C reactive protein (CRP) concentrations were increased. In the explant culture experiments, CD8+ cells decreased with the addition of bestatin, betamethasone, and HA. The structure of synovial cells was preserved by the addition of HA. However, the addition of THP induced fibrosis of synovial tissues, increased cells without nuclei, and diminished fascin-expressing cells.

CONCLUSION

THP inhibited, but HA preserved the structure of hypertrophic synovial cells. Scopic synovectomy effectively improved joint effusion and pain; however, the effect was transient, and additional treatment with predonisolone was required. Therefore, it is important to develop a more effective treatment for HAAP.

Increased proviral load in HTLV-1-infected patients with rheumatoid arthritis or connective tissue disease

BACKGROUND

Human T-lymphotropic virus type 1 (HTLV-1) proviral load is related to the development of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and has also been shown to be elevated in the peripheral blood in HTLV-1-infected patients with uveitis or alveolitis. Increased proliferation of HTLV-1-infected cells in, or migration of such cells into, the central nervous system is also seen in HAM/TSP. In the present study, we evaluated the proviral load in a cohort of HTLV-1-infected patients with arthritic conditions.

RESULTS

HTLV-1 proviral load in the peripheral blood from 12 patients with RA and 6 patients with connective tissue disease was significantly higher than that in matched asymptomatic HTLV-1 carriers, but similar to that in matched HAM/TSP controls. HAM/TSP was seen in one-third of the HTLV-1-infected patients with RA or connective tissue disease, but did not account for the higher proviral load compared to the asymptomatic carrier group. The proviral load was increased in the synovial fluid and tissue from an HTLV-1-infected patient with RA, the values suggesting that the majority of infiltrated cells were HTLV-1-infected. In the peripheral blood from HTLV-1-infected patients with RA or connective tissue disease, HTLV-1 proviral load correlated with the percentages of memory CD4+ T cells and activated T cells, and these percentages were shown to be markedly higher in the synovial fluid than in the peripheral blood in an HTLV-1-infected patient with RA.

CONCLUSIONS

These biological findings are consistent with a role of the retrovirus in the development of arthritis in HTLV-1-infected patients. A high level of HTLV-1-infected lymphocytes in the peripheral blood and their accumulation in situ might play a central role in the pathogenesis of HTLV-1-associated inflammatory disorders. Alternatively, the autoimmune arthritis, its etiological factors or treatments might secondarily enhance HTLV-1 proviral load.

Protection of mitochondrial perturbation by human T-lymphotropic virus type 1 tax through induction of Bcl-xL expression

This study was designed to determine the inhibitory role of human T-lymphotropic virus type 1 (HTLV-1) tax against apoptotic cell death. We used JPX-9 cells, a Jurkat subclone generated by the stable introduction of a tax expression-plasmid vector, and induced tax expression in JPX-9 cells with CdCl2. Expression of Bcl-2, Bcl-xL, and Bax in JPX-9 cells was assessed with Western blot analysis. Both tax-negative and tax-positive JPX-9 cells were incubated in the presence of several apoptogenic stimuli, and sensitivity to apoptogenic stimuli was also evaluated. Compared with tax-negative JPX-9 cells, Bcl-xL expression was clearly augmented in tax-positive JPX-9 cells. These cells were resistant to both receptor-mediated apoptosis (induced by anti-Fas IgM and tumor necrosis factor-related apoptosis-inducing ligand) and chemical-induced apoptosis (induced by pyrrolidine dithiocarbamate, etoposide, and staurosporine), as evidenced by the presence of hypodiploid DNA-positive cells, activation of caspase-3 and caspase-9, disruption of mitochondrial transmembrane potential (DeltaPsim) and inhibition of cytochrome c release in tax-positive JPX-9 cells compared with tax-negative JPX-9 cells. Our results suggest that tax-mediated Bcl-xL expression inhibits apoptosis of activated T-cells in HTLV-1-seropositive subjects, which consequently promotes the onset of autoimmune disorders such as Sjögren's syndrome.

HTLV-1 proviruses encoding non-functional TAX in adult T-cell leukemia

Adult T-cell leukemia (ATL) is associated with prior infection with human T-cell leukemia virus type 1 (HTLV-1). TAX, the major transactivator of HTLV-1, has been implicated in the immortalization of infected T-cells, but molecular mechanisms of in vivo malignant cell transformation induced by HTLV-1 remain unclear. To investigate the role of TAX in the monoclonal proliferation of ATL cells, we determined the nucleotide sequence of tax DNA clones obtained from 6 ATL patients and analysed the biological function of their products. We found that ATL cells from 2 of these patients possessed tax with a nonsense or frame-shift mutation resulting in the premature termination of its protein product, which was no longer functional. This strongly argued against an indispensable role of TAX for the maintenance of ATL cells in vivo. On the other hand, the frequency of nucleotide substitutions found in non-functional tax DNA clones from these patients was significantly lower than those in functional tax DNA clones from the others, suggesting a role for TAX in the genome instability of infected cells. Although mismatch repair defects in the microsatellite markers, including those in hMSH3, hMSH6, BAX, TGF-beta RII, and E2F4 genes, were infrequent, we found an increase in the number of CAG repeats of the E2F4 microsatellite marker in 1 patient. These findings indicate that while TAX may be a necessary prerequisite for malignant transformation of infected cells, it is not essential for the maintenance of ATL cells in vivo.

Inhibition of Caspase Cascade by HTLV-I Tax Through Induction of NF-κB Nuclear Translocation

NF-κB is required for prevention of apoptosis. We examined the importance of human T-cell leukemia virus–I (HTLV-I) Tax protein to stimulate NF-κB nuclear translocation, thus preventing apoptosis. Jurkat cells and JPX-9 cells in which the inducible Tax expression plasmid vector was stably transfected were used in the present study. Both Jurkat and Tax− JPX-9 cells had small amounts of basal nuclear NF-κB activity. The addition of NF-κB inhibitors suppressed NF-κB nuclear translocation of the cells, thus inducing apoptosis. Sequential activation of caspases from caspase-8 to caspase-3 was shown during this process. NF-κB nuclear translocation in JPX-9 cells was stimulated through Tax expression, and both the activation of caspases and apoptosis induced by NF-κB inhibitors were significantly suppressed in the Tax+ JPX-9 cells. The expression of Bcl-2, Bax, and Bcl-x was not changed among Jurkat, Tax− JPX-9, and Tax+ JPX-9 cells in the presence or absence of NF-κB inhibitors. X-chromosome–linked inhibitor of apoptosis (XIAP) protein expression in Tax−JPX-9 cells was significantly suppressed by NF-κB inhibitors, however, its expression in Tax+ JPX-9 cells was maintained even by the addition of NF-κB inhibitors. Our results suggest that the activation of NF-κB via Tax protein in HTLV-I infected cells renders the cells resistant to apoptosis. The expression of anti-apoptotic gene products such as XIAP to suppress caspase cascade, results in an increase of cytokine production and cell proliferation; one of the proposed mechanisms that promotes autoimmune disorders such as Sjögren’s syndrome and rheumatoid arthritis found in HTLV-I seropositive subjects.

Inhibition of Caspase Cascade by HTLV-I Tax Through Induction of NF-κB Nuclear Translocation

NF-κB is required for prevention of apoptosis. We examined the importance of human T-cell leukemia virus–I (HTLV-I) Tax protein to stimulate NF-κB nuclear translocation, thus preventing apoptosis. Jurkat cells and JPX-9 cells in which the inducible Tax expression plasmid vector was stably transfected were used in the present study. Both Jurkat and Tax− JPX-9 cells had small amounts of basal nuclear NF-κB activity. The addition of NF-κB inhibitors suppressed NF-κB nuclear translocation of the cells, thus inducing apoptosis. Sequential activation of caspases from caspase-8 to caspase-3 was shown during this process. NF-κB nuclear translocation in JPX-9 cells was stimulated through Tax expression, and both the activation of caspases and apoptosis induced by NF-κB inhibitors were significantly suppressed in the Tax+ JPX-9 cells. The expression of Bcl-2, Bax, and Bcl-x was not changed among Jurkat, Tax− JPX-9, and Tax+ JPX-9 cells in the presence or absence of NF-κB inhibitors. X-chromosome–linked inhibitor of apoptosis (XIAP) protein expression in Tax−JPX-9 cells was significantly suppressed by NF-κB inhibitors, however, its expression in Tax+ JPX-9 cells was maintained even by the addition of NF-κB inhibitors. Our results suggest that the activation of NF-κB via Tax protein in HTLV-I infected cells renders the cells resistant to apoptosis. The expression of anti-apoptotic gene products such as XIAP to suppress caspase cascade, results in an increase of cytokine production and cell proliferation; one of the proposed mechanisms that promotes autoimmune disorders such as Sjögren’s syndrome and rheumatoid arthritis found in HTLV-I seropositive subjects.

Involvement of simultaneous multiple transcription factor expression, including cAMP responsive element binding protein and OCT-1, for synovial cell outgrowth in patients with rheumatoid arthritis

OBJECTIVE

To elucidate possible roles of several transcription factors in the pathogenesis of rheumatoid arthritis (RA), the transcription factor expression in RA synovial tissue and their contribution to RA synovial cell functions were studied.

METHODS

Single cell suspension of dissociated synovial tissue was cultured to induce in vitro tissue outgrowth of RA synovial cells. Transcription factors were immunohistochemically identified in RA synovial tissue obtained by joint surgery and in the in vitro tissue outgrowth, and confirmed by western blotting and gel shift assays.

RESULTS

Immunohistochemical examination of RA synovial tissue revealed simultaneous expression of various transcription factors (NF-kappa B, c-Jun (a component of AP-1), cAMP responsive element binding protein (CREB), and OCT-1). The same set of transcription factors was expressed in the in vitro tissue outgrowth of RA patients. The early passage RA synovial cells were treated with interleukin 1 beta (IL1 beta) and confirmed translocation of transcription factors into the nucleus by western blotting, and their DNA binding activity by gel shift assays.

CONCLUSION

This study emphasises the importance of the simultaneous expression of several transcription factors for the hyperactivity of RA synovial cells that leads to tissue outgrowth.

Ribozyme-based gene cleavage approach to chronic arthritis associated with human T cell leukemia virus type I: induction of apoptosis in synoviocytes by ablation of HTLV-I tax protein

OBJECTIVE

To develop gene therapy for patients with human T cell leukemia virus type I (HTLV-I)-associated arthropathy (HAAP), we investigated the effects of ribozyme-mediated cleavage of HTLV-I tax/rex messenger RNA (mRNA) on synovial overgrowth.

METHODS

We introduced 2 hammerhead ribozymes targeted against HTLV-I tax/rex mRNA into synovial cells obtained from patients with HAAP and from patients with HTLV-I-negative rheumatoid arthritis (RA) and examined the ribozyme-mediated ablation of Tax expression. Using standard methods, we also determined the cells' ability to stop proliferating and to undergo apoptosis.

RESULTS

The ribozymes successfully cleaved tax/rex mRNA in HAAP patient synoviocytes. Both tax mRNA expression and Tax protein synthesis were inhibited significantly, resulting in inhibition of synovial cell growth and induction of apoptosis. In contrast, synovial cells from RA patients were not affected.

CONCLUSION

In vitro results suggest that ribozyme-mediated gene therapy can inhibit the growth of HTLV-I-infected synovial cells, which is maintained by Tax protein, in HTLV-I-related diseases including HAAP.

Signal transduction of granulocyte macrophage-colony stimulating factor in a human endothelium-derived cell line

Granulocyte macrophage-colony stimulating factor (GM-CSF) regulates the growth and differentiation of hematopoietic cells and is also involved in angiogenesis. The induction of protein tyrosine phosphorylation is critical for cytokines and growth factor-mediated signal transduction. The protein tyrosine kinase (PTK), JAK2 is involved in signaling through a number of cytokine receptors, including GM-CSF receptors. In the present study, we investigated the effect of GM-CSF on the cell cycle and protein tyrosine phosphorylation in a human endothelial cell-derived cell line, EA.hy 926 cells. GM-CSF induced the cell cycle progression and tyrosine phosphorylation of cellular proteins including JAK2 kinase in EA.hy 926 cells. Herbimycin A, a PTK inhibitor, completely blocked the GM-CSF-induced cell cycle progression, protein tyrosine phosphorylation and JAK2 kinase activation in EA.hy 926 cells. Our results demonstrate that protein tyrosine phosphorylation and JAK2 kinase activation are closely related to the GM-CSF-mediated signal transduction and growth in vascular endothelial cells, and suggest the efficacy of herbimycin A in controlling angiogenesis.

Human T-Cell Leukemia Virus Type I Tax Transactivates the Promoter of Human Prointerleukin-1β Gene Through Association With Two Transcription Factors, Nuclear Factor–Interleukin-6 and Spi-1

The human T-cell leukemia virus type I (HTLV-I), which infects a wide variety of mammalian cells including monocytes and macrophages, encodes a transactivating protein designated as Tax. We now report that Tax induces the human prointerleukin-1β (IL1B) gene promoter in monocytic cells. In our transient transfection assays using human THP-1 monocytic cells, a chloramphenicol acetyltransferase (CAT) construct containing the IL1B promoter sequence between positions −131 and +12 showed an approximately 90-fold increase in activity following cotransfection of a Tax expression vector. Moreover, Tax synergized with lipopolysaccharide (LPS) to induce the IL1B promoter activity. Analyses of specific nucleotide substitutions further indicated that the Tax-induced transcriptional activation requires two transcription factor binding motifs within the IL1B promoter; one is a binding site for nuclear factor (NF)-IL6 (CCAAT/enhancer binding protein β, C/EBPβ), which belongs to the basic region-leucine zipper (bZIP) family and the other for Spi-1 (PU.1), which is an Ets family protein found principally in monocytes, macrophages, and B lymphocytes. In electrophoretic mobility shift assays (EMSA) using in vivo THP-1 nuclear extracts, Tax expression in THP-1 monocytic cells significantly increased binding of the two factors to their target IL1B promoter sequences. However, in contrast to NF-IL6 and Spi-1, DNA binding activity of Oct-1, an ubiquitously expressed octamer-binding protein was not affected by Tax. Additional EMSA using in vitro translated proteins also showed that recombinant Tax enhances DNA binding of both of recombinant NF-IL6 and Spi-1 proteins. These data were supported by our glutathione S-transferase (GST)-pulldown data, which indicated that Tax physically interacts with the two proteins. Based on the results obtained from the present study, we conclude that the IL1B promoter is a Tax-responsive sequence as a result of ability of Tax to induce binding of NF-IL6 and Spi-1 to the IL1B promoter sequence through protein-protein interaction.

Arthritis syndromes associated with human T cell lymphotropic virus type I infection

Arthritis syndromes occur associated with HTLV-I infection both in the presence and in the absence of clinical ATL, and polyarthritis may be the presenting manifestation of HTLV-I-associated ATL. In both clinical settings, HTLV-I-infected T cells home to affected joints, and tax-transgenic mouse studies have suggested a pathogenic role for the HTLV-I tax gene in inducing synovial cell proliferation in HAA. Understanding the pathogenesis of rheumatoid arthritis-like arthritis syndromes that occur in the setting of HTLV-I infection should also provide insights into understanding of cellular and molecular mechanisms of synovial cell proliferation in HTLV-I-negative rheumatoid arthritis.

Cytokine production by endothelial cells infected with human T cell lymphotropic virus type I

OBJECTIVE

To investigate the ability of human T cell lymphotropic virus type I (HTLV-I) to infect endothelial cells and induce cytokine production by these cells.

METHODS

Human umbilical vein endothelial cells (HUVEC) were cocultured with HTLV-I infected T cell line (MT-2 cells) or uninfected T cell line (CEM cells).

RESULTS

Following coculture with MT-2 cells, endothelial cells expressed HTLV-I specific core antigens. Endothelial cells cocultured with MT-2 cells produced significant amounts of several cytokines, including interleukin (IL)-1 alpha, IL-6, granulocyte colony stimulating factor (G-CSF), and granulocyte/macrophage colony stimulating factor (GM-CSF), compared with endothelial cells cocultured with CEM cells. Coculturing of endothelial cells with MT-2 and CEM cells failed to produce detectable amounts of IL-1 beta and tumour necrosis factor alpha (TNF-alpha). The production of cytokines by endothelial cells cocultured with MT-2 cells was more persistent than that by endothelial cells cocultured with CEM cells after several passages. Furthermore, the production was blocked by cocultivation of endothelial cells and MT-2 cells using the Millicell system. Finally, after cocultivation of endothelial cells and MT-2 cells, endothelial cells positive for HTLV-I antigen were stained by anti-GM-CSF antibody.

CONCLUSIONS

HTLV-I can infect endothelial cells, resulting in their active production of several cytokines, such as IL-1 alpha, IL-6, G-CSF, and GM-CSF. These findings strongly suggest that the excess production of these cytokines by HTLV-I infected endothelial cells may be involved in the pathogenesis of HTLV-I associated inflammatory diseases.

HAM/TSP: recent perspectives in Japan

Neurologic diseases associated with human T-cell lymphotropic virus type I (HTLV-I) infection have a clinical spectrum that includes myelopathy (HTLV-I-associated myelopathy/tropical spastic paraparesis, HAM/TSP) as the central manifestation. Many clinical signs of involvement outside the central nervous system (CNS) have been described in some patients with HAM/TSP and have triggered and advanced the discovery of some HTLV-I-associated concepts in HTLV-I-infected individuals without signs of CNS involvement. Most of these HTLV-I-associated diseases exhibit common viroimmunologic characteristics that include a distributional bias of HTLV-I activation between the blood flow and the affected lesions and accumulated cellular immune responses in the lesions. These facts suggest that the vulnerable tissue(s) in some HTLV-I-infected individuals may not be defined by an exclusive tissue specificity, but that common steps of HTLV-I-versus-host interactions may have an important role in the pathologic process(es) in these diseases. This review summarizes the recent perspectives of the clinical spectrum and the pathogenesis of HAM/TSP in Japan. Furthermore, the feasible pathogenic involvement of cellular interactions between infected cells and responding immunocompetent cells in the affected tissues is emphasized.

HTLV-I-induced T-cell activation

Infection by the human T-cell lymphotropic virus type I (HTLV-I) causes T-cell activation by at least two separate mechanisms. One mechanism involves activation of the T cells harboring the virus and is exemplified by in vivo infected nonimmortalized T-cell clones that display a prolonged state of activation. This HTLV-I-induced T-cell activation is inhibited by rapamycin, a drug that inhibits p70 S6-kinase and blocks cell cycle in G1, but is not inhibited by FK506 or cyclosporin A, both of which inhibit interleukin-2 (IL-2) production. The phenotype of this pathway is consistent with an hyperactive IL-2R pathway or CD28 pathway, indicating that HTLV-I may contribute a costimulatory signal to the infected T cell. As a separate mechanism, HTLV-I-infected T cells can induce activation of uninfected T cells via T-T-cell interaction mediated by the LFA-3-CD2 pathway. This may induce IL-2 production from the uninfected T cells, leading to a more generalized activation of the immune system that potentially could provide a basis for some of the diseases associated with HTLV-I. Moreover, this THTLV-I-T-cell interaction could explain the spontaneous proliferation observed in patients with HTLV-I-associated myelopathy/tropical spastic paraparesis.

Prevalence of serum and salivary antibodies to HTLV-1 in Sjögren's syndrome

There is accumulating evidence that human T-lymphotropic virus-1 (HTLV-1) infection contributes to the development of various inflammatory disorders. To elucidate the relation between the infection and Sjögren's syndrome, seroepidemiological and virological studies were conducted on patients with this syndrome in Nagasaki Prefecture, Japan, an area heavily endemic for HTLV-1. The HTLV-1 seroprevalence rate among the patients with Sjögren's syndrome (17/74, 23%) was significantly higher than that among blood donors (916/27,284, 3%), whereas the difference between patients with systemic lupus erythematosus and blood donors was insignificant. Moreover, among Sjögren's syndrome patients the seroprevalence was high irrespective of age, unlike that among blood donors, which rose with age. Titres of serum antibodies in the HTLV-1 seropositive patients with Sjögren's syndrome were similar to those among patients with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and significantly higher than those among healthy carriers. IgM class antibodies were commonly detected in the serum of patients with Sjögren's syndrome. However, unlike that in HAM/TSP patients, the viral load in peripheral-blood mononuclear cells was not necessarily high in the seropositive Sjögren syndrome group. Salivary IgA antibodies to HTLV-1 were common among seropositive patients with Sjögren's syndrome (5/7), which might be due to increased viral activity in the salivary glands. These antibodies were barely detectable in HAM/TSP patients (prevalence 1/10) or in healthy carriers (0/11). The findings strongly suggest that HTLV-1 is involved in the pathogenesis of the disease in a subset of patients with Sjögren's syndrome in endemic areas.

Expression of human T lymphotropic virus type 1 (HTLV-1) tax/rex gene in fresh bronchoalveolar lavage cells of HTLV-1-infected individuals

Accumulating evidence has suggested the involvement of HTLV-1 in the inflammatory lesions of various organs, including the lung. However, the causal relationship between HTLV-1 and inflammatory responses in the organs remains to be elucidated. In order to evaluate the expression of HTLV-1 and its effects in the lung, we examined the expression of mRNA for the HTLV-1 tax/rex gene in fresh bronchoalveolar lavage cells (BALC) and peripheral blood mononuclear cells (PBMC) of 23 seropositive individuals, including six patients with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), by use of an improved method of reverse transcription-polymerase chain reaction (RT-PCR). The tax/rex mRNA was more frequently detected in BALC than in PBMC. All the HAM/TSP patients and eight of 17 carriers without neurological symptoms showed the expression of tax/rex mRNA in the BALC. IgM class antibodies to HTLV-1 were preferentially detected in sera of the tax/rex mRNA-positive individuals. The detection of tax/rex mRNA correlated closely with the presence of lymphocytosis accompanied by an elevated proportion of IL-2 receptor-bearing T cells in the BALC. Our findings indicate the crucial role of viral expression in the inflammatory response in the lung in HTLV-1-infected individuals.

Mechanism of inhibitory effect of dextran sulfate and heparin on human T-cell lymphotropic virus type I (HTLV-I)-induced syncytium formation in vitro: role of cell-to-cell contact

Cell-to-cell contact is usually essential for syncytium formation by HTLV-I-infected cell lines. The present study was undertaken to determine the inhibitory effect of polyanionic compounds, dextran sulfate and heparin, on HTLV-I-induced syncytium formation, as demonstrated by the fusion of HTLV-I-infected cells with target cells. These two compounds almost completely blocked syncytium formation in the early phase of the reaction at a concentration of 125 micrograms/ml, but dextran, as a control, did not inhibit it at concentrations up to 625 micrograms/ml. 50% inhibition of syncytium formation was detected at a concentration of 2 micrograms/ml of dextran sulfate 5000, 3 micrograms/ml of dextran sulfate 8000 and 8 micrograms/ml of heparin. The binding of radiolabeled HTLV-I-infected cells (HCT-1) to the target cells was inhibited by addition of dextran sulfate and heparin, and the inhibitory effects were concentration-dependent. No marked changes were detected in the expression of adhesion molecules on the virus-infected cells and target cells, and in the expression of envelope proteins on the virus-infected cells after exposing them to the polyanionic compounds. These results suggest that the blocking of cell-to-cell contact by polyanionic compounds, probably independent of surface adhesion molecules, is important for their inhibitory effect on HTLV-I-induced syncytium formation.