Quantification of T cell clonality in human T cell leukaemia virus type-1 carriers can detect the development of adult T cell leukaemia early

Anti-HTLV-1 immunity combined with proviral load as predictive biomarkers for adult T-cell leukemia-lymphoma

Human T-cell leukemia virus type 1 (HTLV-1) establishes chronic infection in humans and induces a T-cell malignancy called adult T-cell leukemia-lymphoma (ATL) and several inflammatory diseases such as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Persistent HTLV-1 infection is established under the pressure of host immunity, and therefore the immune response against HTLV-1 is thought to reflect the status of the disease it causes. Indeed, it is known that cellular immunity against viral antigens is suppressed in ATL patients compared to HAM/TSP patients. In this study, we show that profiling the humoral immunity to several HTLV-1 antigens, such as Gag, Env, and Tax, and measuring proviral load are useful tools for classifying disease status and predicting disease development. Using targeted sequencing, we found that several carriers whom this profiling method predicted to be at high risk for developing ATL indeed harbored driver mutations of ATL. The clonality of HTLV-1-infected cells in those carriers was still polyclonal; it is consistent with an early stage of leukemogenesis. Furthermore, this study revealed significance of anti-Gag proteins to predict high risk group in HTLV-1 carriers. Consistent with this finding, anti-Gag cytotoxic T lymphocytes (CTLs) were increased in patients who received hematopoietic stem cell transplantation and achieved remission state, indicating the significance of anti-Gag CTLs for disease control. Our findings suggest that our strategy that combines anti-HTLV-1 antibodies and proviral load may be useful for prediction of the development of HTLV-1-associated diseases.

HTLV-1 cell-free DNA in plasma as a potential biomarker in HTLV-1 carriers and adult T-cell leukemia-lymphoma

Viral cell-free DNA (cfDNA) in plasma has been widely evaluated for detecting cancer and monitoring disease in virus-associated tumors. We investigated whether the amount of cfDNA of human T-cell leukemia virus type 1 (HTLV-1) correlates with disease state in adult T-cell leukemia-lymphoma (ATL). HTLV-1 cfDNA in aggressive ATL was significantly higher than that in indolent ATL and asymptomatic carriers. Notably, patients with lymphoma type represented higher HTLV-1 cfDNA amount than chronic and smoldering subtypes, though they had no abnormal lymphocytes in the peripheral blood. HTLV-1 cfDNA can be a universal biomarker that reflects the expansion of ATL clones.

Prospects of early therapeutic interventions for indolent adult T-cell leukemia/lymphoma based on the chronic lymphocytic leukemia progression model

Adult T-cell leukemia/lymphoma (ATLL) has aggressive clinical behaviors, and improving its prognosis is a great challenge. A disease progression model from asymptomatic human T-cell leukemia virus type 1 carrier to aggressive-type ATLL has been proposed, and indolent ATLL comprising a smoldering or favorable chronic type is located at the midpoint. Even the most favorable smoldering type has a 4-year overall survival rate of <60%. Although watchful waiting is pervasive in patients with indolent ATLL, early therapeutic intervention is discussed among hematologists. Indolent ATLL was once termed T-cell-derived chronic lymphocytic leukemia (CLL). Unlike indolent ATLL, several molecular-targeted agents at the initial treatment have dramatically improved CLL prognosis. Recent studies on CLL have revealed a similar progression model involving premalignant monoclonal B-cell lymphocytosis (MBL). In particular, individuals with high-count MBL have an increased lymphoma risk. Considering the unsatisfactory long-term prognosis of indolent ATLL, further treatment strategies, including precision medicine, are warranted.

The transcriptome of HTLV-1-infected primary cells following reactivation reveals changes to host gene expression central to the proviral life cycle

Infections by Human T cell Leukaemia Virus type 1 (HTLV-1) persist for the lifetime of the host by integrating into the genome of CD4+ T cells. Proviral gene expression is essential for proviral survival and the maintenance of the proviral load, through the pro-proliferative changes it induces in infected cells. Despite their role in HTLV-1 infection and a persistent cytotoxic T lymphocyte response raised against the virus, proviral transcripts from the sense-strand are rarely detected in fresh cells extracted from the peripheral blood, and have recently been found to be expressed intermittently by a small subset of cells at a given time. Ex vivo culture of infected cells prompts synchronised proviral expression in infected cells from peripheral blood, allowing the study of factors involved in reactivation in primary cells. Here, we used bulk RNA-seq to examine the host transcriptome over six days in vitro, following proviral reactivation in primary peripheral CD4+ T cells isolated from subjects with non-malignant HTLV-1 infection. Infected cells displayed a conserved response to reactivation, characterised by discrete stages of gene expression, cell division and subsequently horizontal transmission of the virus. We observed widespread changes in Polycomb gene expression following reactivation, including an increase in PRC2 transcript levels and diverse changes in the expression of PRC1 components. We hypothesize that these transcriptional changes constitute a negative feedback loop that maintains proviral latency by re-deposition of H2AK119ub1 following the end of proviral expression. Using RNAi, we found that certain deubiquitinases, BAP1, USP14 and OTUD5 each promote proviral transcription. These data demonstrate the detailed trajectory of HTLV-1 proviral reactivation in primary HTLV-1-carrier lymphocytes and the impact on the host cell.

HTLV-1 persistence and the oncogenesis of adult T-cell leukemia/lymphoma

Human T-cell leukemia virus type 1 (HTLV-1), also known as human T-lymphotropic virus type 1, causes the aggressive malignancy known as adult T-cell leukemia/lymphoma (ATL) in 5% of infected people and a chronic progressive inflammatory disease of the central nervous system, HTLV-1-associated myelopathy, in ∼0.3% to 4% of them, varying between regions where it is endemic. Reliable treatments are lacking for both conditions, although there have been promising recent advances in the prevention and treatment of ATL. Because ATL typically develops after several decades of infection, it is necessary to understand how the virus persists in the host despite a strong immune response, and how this persistence results in oncogenesis.

HAS-Flow May Be an Adequate Method for Evaluating Human T-Cell Leukemia Virus Type 1 Infected Cells in Human T-Cell Leukemia Virus Type 1-Positive Rheumatoid Arthritis Patients Receiving Antirheumatic Therapies: A Retrospective Cross-Sectional Observation Study

The study aims to assess the usefulness of human T-cell leukemia virus type 1 (HTLV-1)-infected cell analysis using flow cytometry (HAS-Flow) as a monitoring method for adult T-cell leukemia (ATL) development in HTLV-1-positive patients with rheumatoid arthritis (RA) under treatment with antirheumatic therapies. A total of 13 HTLV-1-negative and 57 HTLV-1-positive RA patients participated in this study, which was used to collect clinical and laboratory data, including HAS-Flow and HTLV-1 proviral load (PVL), which were then compared between the two groups. CADM1 expression on CD4+ cells in peripheral blood (PB) was used to identify HTLV-1-infected cells. The population of CADM1+ CD4+ cells was significantly higher in HTLV-1-positive RA patients compared to HTLV-1-negative RA patients. The population of CADM1+ CD4+ cells was correlated with HTLV-1 PVL values. There were no antirheumatic therapies affecting both the expression of CADM1 on CD4+ cells and PVLs. Six HTLV-1-positive RA patients who indicated both high HTLV-1 PVL and a predominant pattern of CADM1+ CD7neg CD4+ cells in HAS-Flow can be classified as high-risk for ATL progression. HAS-Flow could be a useful method for monitoring high-risk HTLV-1-positive RA patients who are at risk of developing ATL during antirheumatic therapies.

CAR-iNKT cells targeting clonal TCRVβ chains as a precise strategy to treat T cell lymphoma

Introduction

Most T cell receptor (TCR)Vβ chain-expressing T cell lymphomas (TCL) including those caused by Human T cell leukaemia virus type-1 (HTLV-1) have poor prognosis. We hypothesised that chimeric antigen receptor (CAR)-mediated targeting of the clonal, lymphoma-associated TCRβ chains would comprise an effective cell therapy for TCL that would minimally impact the physiological TCR repertoire.

Methods

As proof of concept, we generated CAR constructs to target four TCRVβ subunits. Efficacy of the CAR constructs was tested using conventional T cells as effectors (CAR-T). Since invariant NKT (iNKT) cell do not incite acute graft-versus-host disease and are suitable for 'off-the-shelf' immunotherapy, we generated anti-TCRVβ CAR-iNKT cells.

Results

We show that anti-TCRVβ CAR-T cells selectively kill their cognate tumour targets while leaving >90% of the physiological TCR repertoire intact. CAR-iNKT cells inhibited the growth of TCL in vivo, and were also selectively active against malignant cells from Adult T cell leukaemia/lymphoma patients without activating expression of HTLV-1.

Discussion

Thus we provide proof-of-concept for effective and selective anti-TCRVβ CAR-T and -iNKT cell-based therapy of TCL with the latter providing the option for 'off-the-shelf' immunotherapy.

HTLV-1-related adult T-cell leukemia/lymphoma: insights in early detection and management

PURPOSE OF REVIEW

Adult T-cell leukemia-lymphoma (ATL) is an aggressive mature T-cell malignancy that arises in approximately 5% of carriers of human T-lymphotropic virus type 1 (HTLV-1), but this risk is not random among carriers. We describe recent advance in pathogenesis, risk factors and for early detection of ATL.

RECENT FINDINGS

Unraveling ATL molecular genetics has shed light on pathogenesis and provides insights into novel therapeutic targets. Moreover, an important step in improving outcomes is identifying asymptomatic carriers who are at high risk of progression to ATL, which has traditionally relied on quantifying the proviral load (PVL). This can be done by quantifying oligoclonality- and in particular the expanded clone- with molecular and flow cytometric techniques, that can be applied to a clinical setting. Studies using these methods have shown that carriers with oligoclonal populations are at an increased risk of transformation, beyond that that predicted by PVL alone.

SUMMARY

There is an urgent unmet need for developing novel therapies in ATL in order to improve survival. Recent advances in the molecular and epigenetic landscape of ATL, and the early detection of disease offer the potential to intervene early, before disease becomes aggressive, and to offer tailored therapeutic strategies.

Cabotegravir, the Long-Acting Integrase Strand Transfer Inhibitor, Potently Inhibits Human T-Cell Lymphotropic Virus Type 1 Transmission in vitro

Human T-cell lymphotropic virus type 1 (HTLV-1) is a deltaretrovirus most prevalent in southwestern Japan, sub-Saharan Africa, Australia, South America, and the Caribbean. Latest figures approximate 10 million people worldwide to be infected with HTLV-1. This is likely a significant underestimation due to lack of screening in endemic areas and absence of seroconversion symptoms. The two primary diseases associated with HTLV-1 infection are adult T cell leukaemia-lymphoma, a malignant and, sometimes, aggressive cancer; and HTLV-1 associated myelopathy/tropical spastic paraparesis, a debilitating neurological degenerative disease. Unfortunately, despite the poor prognosis, there is currently no effective treatment for HTLV-1 infection. We previously showed that integrase strand transfer inhibitors (INSTIs) clinically used for human immunodeficiency virus type 1 (HIV-1) prophylaxis and treatment are also effective against HTLV-1 transmission in vitro. In 2021 a new INSTI, cabotegravir, was approved by the FDA for HIV-1 treatment. We thus set out to evaluate its efficacy against HTLV-1 infection in vitro. Strand transfer assays performed using recombinant HTLV-1 integrase treated with increasing concentrations of cabotegravir, effectively inhibited strand transfer activity, displaying an IC₅₀ of 77.8 ± 22.4 nM. Furthermore, cabotegravir blocked HTLV-1 transmission in tissue culture; we determined an EC₅₀ of 0.56 ± 0.26 nM, similar to bictegravir. Alu-PCR confirmed the block in integration. Thus, there are four INSTIs and one reverse transcriptase inhibitor approved by the FDA for HIV-1 treatment, that potently block HTLV-1 infection in vitro. This should strongly encourage the establishment of a new standard of HTLV-1 treatment – particularly for pre-exposure prophylaxis and prevention of mother-to-child transmission.

Improved survival of patients with aggressive ATL by increased use of allo-HCT: a prospective observational study

Aggressive adult T-cell leukemia/lymphoma (ATL) is a hematological malignancy that is difficult to treat with chemotherapy alone, and allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative therapy. We conducted a multicenter, prospective, observational study to clarify the treatment outcomes of aggressive ATL in the current era. Between 2015 and 2018, 113 patients aged 70 years or younger with newly diagnosed aggressive ATL were enrolled. The median age at diagnosis was 61 years. Treatment outcomes were compared with those of 1792 ATL patients diagnosed between 2000 and 2013 in our previous retrospective study. The inclusion criteria were the same in both studies. The prospective cohort demonstrated better overall survival (OS) than the retrospective cohort (2-year OS, 45% vs 29%, respectively; P < .001), with a much higher proportion of patients receiving allo-HCT (80% vs 34%, respectively; P < .001) and a shorter interval from diagnosis to allo-HCT (median, 128 vs 170 days, respectively; P < .001). Among the 90 patients who received allo-HCT (cord blood, n = 30; HLA-haploidentical related donors, n = 20; other related donors, n = 14; other unrelated donors, n = 26), the 2-year probabilities of OS, non-relapse mortality (NRM), and disease progression were 44%, 23%, and 46%, respectively. OS and NRM did not differ statistically according to donor type. Our results suggest that increased application of allo-HCT improved the survival of patients with aggressive ATL. The use of cord blood or HLA-haploidentical donors may be feasible for aggressive ATL when HLA-matched related donors are unavailable. This study was registered at the UMIN Clinical Trials Registry as #000017672.