The clinical impact of human T-lymphotrophic virus type 1 (HTLV-1) infection on the development of adult T-cell leukemia-lymphoma (ATL) or HTLV-1-associated myelopathy (HAM) / atypical HAM after allogeneic hematopoietic stem cell transplantation (allo-HSCT) and renal transplantation

Integrated molecular and immunological features of human T-lymphotropic virus type 1 infection and disease progression to adult T-cell leukaemia or lymphoma

The human T-lymphotropic virus type 1 (HTLV-1) retrovirus infects 10-20 million people globally, with endemic regions in southwestern Japan, the Caribbean basin, Africa, and central Australia. HTLV-1 is associated with lifelong infection and immune suppression, resulting in a range of serious sequalae, including adult T-cell leukaemia or lymphoma (ATLL) in 5% of cases. To date, there are no preventive or curative treatments for HTLV-1 and treatment outcomes for ATLL remain generally poor. Depending on the disease subtype, overall survival is 8-55 months. Recent advancements in the past decade have identified genetic, molecular, and immunological events occurring throughout the lives of individuals infected with HTLV-1 and of those who progress to ATLL. In addition, updated guidelines for clinical management have been published. With the aim of focusing research efforts on the development of treatments for both HTLV-1 infections and ATLL, we have conceptualised a four-step disease model for HTLV-1-associated ATLL: (1) viral exposure, (2) establishment of chronic infection, (3) cellular transformation and evolution, and (4) disease presentation and management. For each stage we describe the clinical features, molecular and immunological factors involved, potential biomarkers of disease progression, and the therapeutic applicability of individual targets. We also discuss emerging concepts and novel treatment approaches. Our hope is that this model will promote research interest and guide the testing of new treatments for this neglected virus and its associated rare cancer.

Hijacking Host Immunity by the Human T-Cell Leukemia Virus Type-1: Implications for Therapeutic and Preventive Vaccines

Human T-cell Leukemia virus type-1 (HTLV-1) causes adult T-cell leukemia/lymphoma (ATLL), HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and other inflammatory diseases. High viral DNA burden (VL) in peripheral blood mononuclear cells is a documented risk factor for ATLL and HAM/TSP, and patients with HAM/TSP have a higher VL in cerebrospinal fluid than in peripheral blood. VL alone is not sufficient to differentiate symptomatic patients from healthy carriers, suggesting the importance of other factors, including host immune response. HTLV-1 infection is life-long; CD4+-infected cells are not eradicated by the immune response because HTLV-1 inhibits the function of dendritic cells, monocytes, Natural Killer cells, and adaptive cytotoxic CD8+ responses. Although the majority of infected CD4+ T-cells adopt a resting phenotype, antigen stimulation may result in bursts of viral expression. The antigen-dependent "on-off" viral expression creates "conditional latency" that when combined with ineffective host responses precludes virus eradication. Epidemiological and clinical data suggest that the continuous attempt of the host immunity to eliminate infected cells results in chronic immune activation that can be further exacerbated by co-morbidities, resulting in the development of severe disease. We review cell and animal model studies that uncovered mechanisms used by HTLV-1 to usurp and/or counteract host immunity.

Panuveitis induced by donor-derived CD8+ T cells after allogeneic hematopoietic stem cell transplantation for adult T-cell leukemia

Purpose

This article presents a case of panuveitis that occurred after unrelated allogeneic hematopoietic stem cell transplantation (allo-HSCT) in a patient with lymphoma-type human T-cell leukemia virus type-1 (HTLV-1)-associated adult T-cell leukemia (ATL).

Observations

A 45-year-old man developed unilateral panuveitis 18 months after undergoing allo-HSCT. He underwent vitrectomy, and depositions of grey-white granules localized on the retinal artery were observed in the eye. Cytological examination of the vitreous aspirates showed that the atypical lymphoid cells stained positive for CD3 and CD8, but negative for CD4, B-cell markers, and cytomegalovirus antigen. Interphase fluorescence in situ hybridization using X‐ and Y‐chromosome probes revealed complete donor chimerism in CD8⁺ T cells in the vitreous aspirates.

Conclusions and importance

Donor-derived CD8⁺ T lymphocytes can induce panuveitis like HTLV-1-assiciated uveitis after allo-HSCT in patients with ATL. Pathological diagnosis of vitreous infiltration by vitrectomy is helpful in patients with ATL. Donor-derived CD8⁺ T lymphocytes-induced panuveitis is recurrent but susceptible to regional corticosteroid treatment.

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/This is a primary case of panuveitis induced by donor-derived CD8⁺ T lymphocytes in a patient with aggressive ATL after allo-HSCT.

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/Pathological diagnosis of vitreous infiltration by vitrectomy is helpful in patients with ATL to determine the phenotypes of cells infiltrating the eye of ATL patients.

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/Donor-derived CD8⁺ T lymphocytes-induced panuveitis is recurrent but susceptible to regional corticosteroid treatment.

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.

Epidemiology of HTLV-1 Infection and ATL in Japan: An Update

Adult T-cell leukemia-lymphoma (ATL) is an aggressive T-cell malignancy caused by human T-cell leukemia virus type 1 (HTLV-1) infection that often occurs in HTLV-1-endemic areas, such as Japan, the Caribbean islands, Central and South America, Intertropical Africa, and the Middle East. In Japan, the nationwide estimation of the number of HTLV-1 carriers was at least 1.08 million in 2006–2007. Furthermore, in 2016, the nationwide annual incidence of newly infected with HTLV-1 was first estimated to be 3.8 per 100,000 person-years based on the age-specific seroconversion rates of blood donors in almost all areas of Japan. The incidence rate was three times higher in women than in men, and it was estimated that at least 4,000 new HTLV-1 infections occur yearly among adolescents and adults in Japan. As well known that HTLV-1 infection alone is not a sufficient condition for ATL to develop. To date, a variety of molecular abnormalities and host susceptibilities have been reported as candidate progression factors for the development of ATL in HTLV-1-carriers. In particular, quite recently in Japan, a variety of immunosuppressive conditions have been recognized as the most important host susceptibilities associated with the development of ATL from HTLV-1-carrier status. Furthermore, in 2013–2016 in Japan, a new nationwide epidemiological study of ATL was conducted targeting patients newly diagnosed with ATL in 2010–2011, from which the most current knowledge about the epidemiological characteristics of Japanese patients with ATL was updated as follows: (1) continuing regional unevenness of the distribution of people with HTLV-1, (2) further aging, with the mean age at diagnosis being 67.5 years, (3) declining M/F ratio, (4) increase of the lymphoma subtype, (5) sex differences in subtype distribution, (6) age differences in subtype distribution, and (7) comorbidity condition. In particular, 32.2% of ATL patients had comorbid malignancies other than ATL. However, the number of deaths due to ATL in Japan has been relatively stable, at around 1,000 patients annually, without significant decline from 1999 to 2017. Because the current epidemiological evidence about HTLV-1 and ATL is insufficient, further epidemiological studies are required.

A Nationwide Antenatal Human T-Cell Leukemia Virus Type-1 Antibody Screening in Japan

Japan has been running a nationwide antenatal human T-cell leukemia virus type-1 (HTLV-1) antibody screening program since 2010 for the prevention of HTLV-1 mother-to-child transmission. As part of the program, pregnant women are invited to take an HTLV-1 antibody screening test, usually within the first 30 weeks of gestation, during regular pregnancy checkups. Pregnant women tested positive on the antibody screening test undergo a confirmatory test, either western blotting or line immunoassay. In indeterminate case, polymerase chain reaction (PCR) is used as a final test to diagnose infection. Pregnant women tested positive on a confirmatory or PCR test are identified as HTLV-1 carriers. As breastfeeding is a predominant route of postnatal HTLV-1 mother-to-child transmission, exclusive formula feeding is widely used as a postnatal preventive measure. Although there is insufficient evidence that short-term breastfeeding during ≤3 months does not increase the risk of mother-to-child transmission compared to exclusive formula feeding, this feeding method is considered if the mother is eager to breastfeed her child. However, it is important that mothers and family members fully understand that there is an increase in the risk of mother-to-child transmission when breastfeeding would be prolonged. As there are only a few clinical studies on the protective effect of frozen-thawed breastmilk feeding on mother-to-child transmission of HTLV-1, there is little evidence to recommend this feeding method. Further study on the protective effects of these feeding methods are needed. It is assumed that the risk of anxiety or depression may increase in the mothers who selected exclusive formula feeding or short-term breastfeeding. Thus, an adequate support and counseling for these mothers should be provided. In addition to raising public awareness of HTLV-1 infection, epidemiological data from the nationwide program needs to be collected and analyzed. In most cases, infected children are asymptomatic, and it is necessary to clarify how these children should be followed medically.

Clinical features and human T-cell leukemia virus type-1 (HTLV-1) proviral load in HTLV-1-positive patients with rheumatoid arthritis: Baseline data in a single center cohort study

Objective: Recently, Human T-cell leukemia virus type-1 proviral load (HTLV-1 PVL) has been evaluated as an important predictor of adult T-cell leukemia/lymphoma (ATL) in HTLV-1 carriers. We aimed to evaluate whether HTLV-1 PVL is also important for the development of ATL among HTLV-1-positive patients with rheumatoid arthritis (RA).Methods: We established a cohort of 82 HTLV-1-positive RA patients between 2017 and 2018. Of those, 27 (32.9%) were treated with biological disease-modifying anti-rheumatic drugs (bDMARDs) with/without methotrexate. We measured HTLV-1 PVL in peripheral blood mononuclear cells (PBMCs) at study entry and compared the value by clinical status and treatment options.Results: The median PVL for all was 9.6 copies per 1000 PBMCs without sex difference (male 17.2 and female 8.6; p = .24). The median PVL was significantly higher for patient's comorbid bronchiectasis, malignancies, and opportunistic infectious diseases, compared with patients without comorbidity. There were no significant differences in PVL levels among types of bDMARDs, although the level was tended to be higher for patients treated with JAK inhibitor.Conclusions: HTLV-1 seropositive RA patients comorbid for any diseases having higher HTLV-1 PVLs will be a higher risk for developing ATL. Careful follow-up of these patients is necessary to detect ATL development.