Clinical outcomes of a novel therapeutic vaccine with Tax peptide-pulsed dendritic cells for adult T cell leukaemia/lymphoma in a pilot study

Targeted antibody therapy as a treatment strategy for aggressive adult T-cell leukemia/lymphoma

The standard treatment for aggressive adult T-cell leukemia/lymphoma (ATL) is multi-agent chemotherapy, but the use of more intense cytotoxic anticancer agents is becoming more difficult with the aging of patients at the time of diagnosis. As a means of overcoming this hurdle, antibody drugs, which are supposed to be less toxic, have been developed for ATL. The advent of the anti-CC chemokine receptor 4 (CCR4) antibody mogamulizumab has significantly advanced ATL treatment. Real-world data and a phase 2 clinical trial suggest the efficacy and manageable safety profile of mogamulizumab with combination chemotherapy in elderly patients. Interestingly, mogamulizumab has performed well in cases with CCR4 mutations and cutaneous adverse events. In addition, emerging immunotherapies, including Tax peptide dendritic cell vaccines, immune checkpoint inhibitors, and Chimeric Antigen Receptor-T cell therapy, are under investigation. These innovative approaches aim to enhance immunogenic responses and offer hope for better outcomes in this challenging malignancy.

Elimination of residual adult T-cell leukaemia clones by Tax-targeted dendritic cell vaccine

Background

A pilot clinical study of a Tax peptide-pulsed dendritic cell (DC) vaccine for adult T-cell leukaemia/lymphoma (ATL) indicated favourable clinical outcomes.

Methods

We investigated its anti-tumour effect by T cell receptor (TCR) repertoire analysis in samples from an enrolled ATL patient who achieved a 10-year complete remission after DC vaccination.

Results

In this patient, the dominant residual ATL clones that had persisted following previous treatment entirely disappeared within 3 years after DC vaccination. Additionally, the DC vaccine restored TCR repertoire diversity of normal T cells and newly induced functional Tax-specific CD8+ T cell clones.

Conclusions

The recovery of normal T cell immunity mediated by the DC vaccine may contribute to this long-lasting remission.

Therapeutic Vaccines for Hematological Cancers: A Scoping Review of This Immunotherapeutic Approach as Alternative to the Treatment of These Malignancies

Background/Objectives: The need for innovative cancer treatments has brought immunotherapies to the forefront as a promising approach, with therapeutic vaccines demonstrating the potential to mobilize immune cells to eliminate tumor cells. However, challenges such as genetic variability among patients, immune evasion mechanisms, and disease relapse contribute to the complexity of achieving an ideal therapy, especially for hematological cancers. This review systematically identifies and analyzes recent studies focused on the development of therapeutic immunotherapy vaccines, examining critical aspects such as development stages, key assays for therapeutic validation, treatment outcomes, and study limitations. Methods: A scoping review was conducted following the PRISMA extension guidelines (PRISMA-ScR). Literature searches were conducted across Scopus, PubMed, Web of Science, and Science Direct databases using keywords including "immunotherapy", "vaccines", "immunization", "hematological malignancies", "blood cancer", "hematopoietic neoplasms", and "leukemia". Results: A total of 56 articles published from 2013 to 2024 were included in the analysis. The majority of studies are in the preclinical stage, with some advancing to phase 1 and phase 2 clinical trials. Acute myeloid leukemia emerged as the most frequently studied malignancy. While first- and second-generation vaccines dominate the field, innovative approaches, such as dendritic-cell-based vaccines and mRNA vaccines, are gaining prominence. Notably, preclinical models often demonstrate superior outcomes compared to clinical trials, as results observed in animal models are not fully replicated in human studies. Conclusions: Despite challenges related to disease progression and patient loss, the studies reviewed highlight significant advancements in patient prognosis, emphasizing the potential of novel therapeutic vaccines as an effective alternative for the treatment of hematological cancers.

Low Survival Due to Higher Risk of Relapse and Nonrelapse Mortality After Allogeneic HSCT in ATL Compared with AML and ALL

BACKGROUND

Patients with adult T-cell leukemia/lymphoma (ATL) are considered to have worse outcomes after allogeneic hematopoietic stem cell transplantation (allo-HSCT) than patients with other hematological malignancies, owing to high risk of relapse and immunocompromised status. However, no studies have compared transplant outcomes between patients with ATL and those with other hematological malignancies using a large-scale database.

OBJECTIVES

To compare transplant outcomes between patients with ATL and those with other leukemias and to identify factors contributing to worse transplant outcomes in ATL patients.

STUDY DESIGN

Using Japanese registry data, we retrospectively compared transplant outcomes between patients with ATL and those with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). As ATL often develops in patients in their 60s or older, patients with ATL, AML, or ALL aged ≥50 years were included in order to compare patients in the same age group. A total of 7764 patients (ATL, n = 1151; AML, n = 5393; ALL, n = 1220) who underwent their first allo-HSCT between January 1, 2006 and December 31, 2017 were included in this study.

RESULTS

Compared with AML, ATL showed significantly worse overall survival (OS) (hazard ratio [HR], 1.24; 95% confidence interval [CI], 1.14 to 1.34; P < .001) and higher risk of relapse (HR, 1.33; 95% CI, 1.2 to 1.47; P < .001), while there were no significant differences between AML and ALL. Among patients in complete remission (CR) at transplantation, ATL showed worse OS (HR, 1.30; 95% CI, 1.08 to 1.56; P = .006), higher risk of relapse (HR, 1.78; 95% CI, 1.48 to 2.14; P < .001), and higher risk of nonrelapse mortality (NRM) (HR, 1.38; 95% CI, 1.14 to 1.33; P = .001) in comparison with AML, whereas there were no significant differences between AML and ALL.

CONCLUSION

We found that ATL patients have poor transplant outcomes compared with AML or ALL patients. In ATL patients, survival is poor, relapse is more frequent, and NRM is significantly higher, especially in cases of CR. These findings suggest that prevention of relapse and transplant-related complications is important for successful allo-HSCT in ATL.

Spontaneous regression in mature T-cell non-Hodgkin lymphoma

INTRODUCTION

Spontaneous regression (SR) is observed in some patients with mature T-cell non-Hodgkin lymphoma (MTCL), including adult T-cell leukemia/lymphoma (ATL), although the incidence is rare.

AREA COVERED

We extracted 31 cases with MTCL who experienced SR based on a literature search and summarized the patient characteristics and clinical outcomes.

EXPERT OPINION

MTCL with SR included various subtypes, the most common being ATL (n = 17). Five of 24 cases (21%) maintained SR for more than 5 years, and the median duration of SR was 2 years. Sixteen of 31 cases (52%) experienced tumor relapse after SR. Two retrospective studies including ATL cases showed SR rates of 18% and 4%, respectively. Representative triggers are infection and surgical biopsies, and possible mechanisms include immunological mechanisms such as cross-reactivity of virus-specific T cells with tumor antigens. The diagnostic criteria for SR are not standardized among reports, and the clinical outcomes are not fully described. Practically, observation is the only accepted strategy after SR was achieved. In the era of molecular targeted therapy or immunotherapy, new strategies including maintenance therapy after SR could be discussed, although clinical data are lacking.

Unveiling the nexus: The tumor microenvironment as a strategic frontier in viral cancers

Viral infections are a significant factor in the etiology of various cancers, with the tumor microenvironment (TME) playing a crucial role in disease progression. This review delves into the complex interactions between viruses and the TME, highlighting how these interactions shape the course of viral cancers. We explore the distinct roles of immune cells, including T-cells, B-cells, macrophages, and dendritic cells, within the TME and their influence on cancer progression. The review also examines how viral oncoproteins manipulate the TME to promote immune evasion and tumor survival. Unraveling these mechanisms highlights the emerging paradigm of targeting the TME as a novel approach to cancer treatment. Our analysis provides insights into the dynamic interplay between viruses and the TME, offering a roadmap for innovative treatments that leverage the unique characteristics of viral cancers.

Immunological aspects of HTLV-1 persistence; for the prevention and treatment of Adult T-cell leukaemia-lymphoma (ATL)

Human T-cell leukaemia virus type-1 (HTLV-1) causes the highly aggressive malignancy adult T-cell leukaemia-lymphoma (ATL) in approximately 5 % of chronically infected carriers. HTLV-1 persists in the host by enhancing survival of infected-T-cells despite the presence of a strong immune response. Therefore, asymptomatic HTLV-1 carriers have a lifelong balance between infected cell proliferation and the host antiviral immune response. However, this immunological balance is lost in patients with ATL. Reliable treatment options are lacking and there is urgent need for new treatment strategies to improve the dismal prognosis of ATL. In this review, we present a summary of the current knowledge on the immunological aspects of HTLV-1 persistence and the immune alterations observed in ATL, and discuss how the recent emerging advances in adoptive immunotherapy may offer a prevention and treatment option for ATL.

Chemotherapy and allo-HSCT for young patients with aggressive ATL

Adult T-cell leukemia-lymphoma (ATL) is an aggressive malignancy with a poor prognosis, especially for patients with the aggressive subtype. While conventional chemotherapy offers short-term disease control, allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the most promising curative approach for young, transplant-eligible patients. This review focuses on current treatment strategies for aggressive ATL in this specific population. We discuss the rationale for early upfront allo-HSCT following induction chemotherapy. The advent of allo-HSCT using alternative donors, particularly haploidentical HCT, has broadened the applicability of early upfront allo-HSCT in patients with aggressive ATL worldwide. Finally, we address emerging therapies that may improve outcomes in the context of allo-HSCT, paving the way for further advancements in the treatment of aggressive ATL.

Therapeutic advances for the management of adult T cell leukemia: Where do we stand?

Adult T cell leukemia (ATL) is an aggressive blood malignancy secondary to chronic infection with the human T cell leukemia virus type I (HTLV-1) retrovirus. ATL encompasses four subtypes (acute, lymphoma, chronic, and smoldering), which exhibit different clinical characteristics and respond differently to various treatment strategies. Yet, all four subtypes are characterized by a dismal long-term prognosis and a low survival rate. While antiretroviral therapy improves overall survival outcomes in smoldering and chronic subtypes, survival remains poor in lymphoma subtypes despite their good response to intensive chemotherapy. Nonetheless, acute ATL remains the most aggressive form associated with profound immunosuppression, chemo-resistance and dismal prognosis. Targeted therapies such as monoclonal antibodies, epigenetic therapies, and arsenic/IFN, emerged as promising therapeutic approaches in ATL. Allogeneic hematopoietic cell transplantation is the only potentially curative modality, alas applicable to only a small percentage of patients. The recent findings demonstrating the expression of the viral oncoprotein Tax in primary ATL cells from patients with acute or chronic ATL, albeit at low levels, and their dependence on continuous Tax expression for their survival, position ATL as a virus-addicted leukemia and validates the rationale of anti-viral treatment strategies. This review provides a comprehensive overview on conventional, anti-viral and targeted therapies of ATL, with emphasis on Tax-targeted therapied in the pre-clinical and clinical settings.

Applications of cell therapy in the treatment of virus-associated cancers

A diverse range of viruses have well-established roles as the primary driver of oncogenesis in various haematological malignancies and solid tumours. Indeed, estimates suggest that approximately 1.5 million patients annually are diagnosed with virus-related cancers. The predominant human oncoviruses include Epstein-Barr virus (EBV), Kaposi sarcoma-associated herpesvirus (KSHV), hepatitis B and C viruses (HBV and HCV), human papillomavirus (HPV), human T-lymphotropic virus type 1 (HTLV1), and Merkel cell polyomavirus (MCPyV). In addition, although not inherently oncogenic, human immunodeficiency virus (HIV) is associated with immunosuppression that contributes to the development of AIDS-defining cancers (specifically, Kaposi sarcoma, aggressive B cell non-Hodgkin lymphoma and cervical cancer). Given that an adaptive T cell-mediated immune response is crucial for the control of viral infections, increasing research is being focused on evaluating virus-specific T cell therapies for the treatment of virus-associated cancers. In this Review, we briefly outline the roles of viruses in the pathogenesis of these malignancies before describing progress to date in the field of virus-specific T cell therapy and evaluating the potential utility of these therapies to treat or possibly even prevent virus-related malignancies.

HTLV-1 vaccination Landscape: Current developments and challenges

Human T-lymphotropic virus type 1 (HTLV-1) is a retrovirus that is distinguished for its correlation to myelopathy/tropical spastic paraparesis (HAM/TSP) and adult T-cell leukemia/lymphoma (ATLL). As well, HTLV-1 has been documented to have links with other inflammatory diseases, such as uveitis and dermatitis. According to the World Health Organization (WHO), the global distribution of HTLV-1 infection is estimated to extend between 5 and 10 million individuals. Recent efforts in HTLV-1 vaccine development primarily involve selecting viral components, such as antigens, from structural and non-structural proteins. These components are chosen to trigger a vigorous immune response from cytotoxic T lymphocytes (CTLs), helper T lymphocytes (HTLs), and B cells. Investigation into developing a vaccine against HTLV-1 is ongoing, and current surveys have explored several approaches, including viral vector vaccines, DNA vaccines, protein and peptide vaccines, dendritic cell-based vaccines, mRNA vaccines, and other platforms. Despite these investigations have shown promising results, challenges like the necessity for long-term protective immunity, addressing viral diversity, and managing potential side effects remain. It is critical to keep track of the progress made in HTLV-1 vaccination research to comprehend the development status and its possible impacts. The evolving nature of vaccine development underscores the importance of staying informed about advancements as we strive to combat HTLV-1-associated diseases through effective vaccination strategies. In this review, our goal is to provide an overview of the current status of HTLV-1 vaccination efforts, emphasizing the progress, challenges, and potential future directions in this vital area of research.

Tumor Antigens beyond the Human Exome

With the advent of immunotherapeutics, a new era in the combat against cancer has begun. Particularly promising are neo-epitope-targeted therapies as the expression of neo-antigens is tumor-specific. In turn, this allows the selective targeting and killing of cancer cells whilst healthy cells remain largely unaffected. So far, many advances have been made in the development of treatment options which are tailored to the individual neo-epitope repertoire. The next big step is the achievement of efficacious "off-the-shelf" immunotherapies. For this, shared neo-epitopes propose an optimal target. Given the tremendous potential, a thorough understanding of the underlying mechanisms which lead to the formation of neo-antigens is of fundamental importance. Here, we review the various processes which result in the formation of neo-epitopes. Broadly, the origin of neo-epitopes can be categorized into three groups: canonical, noncanonical, and viral neo-epitopes. For the canonical neo-antigens that arise in direct consequence of somatic mutations, we summarize past and recent findings. Beyond that, our main focus is put on the discussion of noncanonical and viral neo-epitopes as we believe that targeting those provides an encouraging perspective to shape the future of cancer immunotherapeutics.

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.

Understanding the Immunopathology of HTLV-1-Associated Adult T-Cell Leukemia/Lymphoma: A Comprehensive Review

Human T-cell leukemia virus type-1 (HTLV-1) causes adult T-cell leukemia/lymphoma (ATL). HTLV-1 carriers have a lifelong asymptomatic balance between infected cells and host antiviral immunity; however, 5-10% of carriers lose this balance and develop ATL. Coinfection with Strongyloides promotes ATL development, suggesting that the immunological status of infected individuals is a determinant of HTLV-1 pathogenicity. As CD4+ T cells play a central role in host immunity, the deregulation of their function and differentiation via HTLV-1 promotes the immune evasion of infected T cells. During ATL development, the accumulation of genetic and epigenetic alterations in key host immunity-related genes further disturbs the immunological balance. Various approaches are available for treating these abnormalities; however, hematopoietic stem cell transplantation is currently the only treatment with the potential to cure ATL. The patient's immune state may contribute to the treatment outcome. Additionally, the activity of the anti-CC chemokine receptor 4 antibody, mogamulizumab, depends on immune function, including antibody-dependent cytotoxicity. In this comprehensive review, we summarize the immunopathogenesis of HTLV-1 infection in ATL and discuss the clinical findings that should be considered when developing treatment strategies for ATL.

Therapeutic approaches for HTLV-1-associated adult T-cell leukemia/lymphoma: a comprehensive review

Adult T-cell leukemia/lymphoma (ATLL), an infrequent malignancy resultant from human T-cell lymphotropic virus type I (HTLV-1), exhibits a spectrum of phenotypes, encompassing acute, smoldering, lymphomatous, and chronic variants, each bearing distinct clinical presentations. The preponderant acute manifestation is characterized by hypercalcemia, systemic manifestations, organomegaly, and dermatological eruptions. Conversely, the chronic phenotype is typified by lymphocytosis and/or cutaneous eruptions, while smoldering ATLL assumes an asymptomatic course. Immunocompromise afflicts ATLL patients, heightening their vulnerability to opportunistic infections that frequently intricately intertwine with disease progression. Therefore, an early diagnosis is crucial to manage the disease appropriately. While conventional chemotherapeutic regimens have shown limited success, especially in acute and lymphoma types, recent studies suggest that allogeneic stem cell transplantation might enhance treatment results because it has shown promising outcomes in some patients. Novel therapeutics, such as interferon and monoclonal antibodies, have also shown promise, but more research is needed to confirm their efficacy. Moreover, the identification of biomarkers for ATLL and genetic changes in HTLV-1 infected cells has led to the development of targeted therapies that have shown remarkable success in clinical trials. These targeted therapies have the potential to offer a more personalized approach to the treatment of ATLL. The aim of our review is to elaborate on conventional and novel therapies and the efficiency of mentioned treatments.

Mouse Models for HTLV-1 Infection and Adult T Cell Leukemia

Adult T cell leukemia (ATL) is an aggressive hematologic disease caused by human T cell leukemia virus type 1 (HTLV-1) infection. Various animal models of HTLV-1 infection/ATL have been established to elucidate the pathogenesis of ATL and develop appropriate treatments. For analyses employing murine models, transgenic and immunodeficient mice are used because of the low infectivity of HTLV-1 in mice. Each mouse model has different characteristics that must be considered before use for different HTLV-1 research purposes. HTLV-1 Tax and HBZ transgenic mice spontaneously develop tumors, and the roles of both Tax and HBZ in cell transformation and tumor growth have been established. Severely immunodeficient mice were able to be engrafted with ATL cell lines and have been used in preclinical studies of candidate molecules for the treatment of ATL. HTLV-1-infected humanized mice with an established human immune system are a suitable model to characterize cells in the early stages of HTLV-1 infection. This review outlines the characteristics of mouse models of HTLV-1 infection/ATL and describes progress made in elucidating the pathogenesis of ATL and developing related therapies using these mice.

Onco-Pathogen Mediated Cancer Progression and Associated Signaling Pathways in Cancer Development

Infection with viruses, bacteria, and parasites are thought to be the underlying cause of about 8-17% of the world's cancer burden, i.e., approximately one in every five malignancies globally is caused by an infectious pathogen. Oncogenesis is thought to be aided by eleven major pathogens. It is crucial to identify microorganisms that potentially act as human carcinogens and to understand how exposure to such pathogens occur as well as the following carcinogenic pathways they induce. Gaining knowledge in this field will give important suggestions for effective pathogen-driven cancer care, control, and, ultimately, prevention. This review will mainly focus on the major onco-pathogens and the types of cancer caused by them. It will also discuss the major pathways which, when altered, lead to the progression of these cancers.

Human T-cell lymphotropic virus type 1 (HTLV-1) proposed vaccines: a systematic review of preclinical and clinical studies

BACKGROUND

Numerous vaccination research experiments have been conducted on non-primate hosts to prevent or control HTLV-1 infection. Therefore, reviewing recent advancements for status assessment and strategic planning of future preventative actions to reduce HTLV-1 infection and its consequences would be essential.

METHODS

MEDLINE, Scopus, Web of Science, and Clinicaltrials.gov were searched from each database's inception through March 27, 2022. All original articles focusing on developing an HTLV-1 vaccine candidate were included.

RESULTS

A total of 47 studies were included. They used a variety of approaches to develop the HTLV-1 vaccine, including DNA-based, dendritic-cell-based, peptide/protein-based, and recombinant vaccinia virus approaches. The majority of the research that was included utilized Tax, Glycoprotein (GP), GAG, POL, REX, and HBZ as their main peptides in order to develop the vaccine. The immunization used in dendritic cell-based investigations, which were more recently published, was accomplished by an activated CD-8 T-cell response. Although there hasn't been much attention lately on this form of the vaccine, the initial attempts to develop an HTLV-1 immunization depended on recombinant vaccinia virus, and the majority of results seem positive and effective for this type of vaccine. Few studies were conducted on humans. Most of the studies were experimental studies using animal models. Adenovirus, Cytomegalovirus (CMV), vaccinia, baculovirus, hepatitis B, measles, and pox were the most commonly used vectors.

CONCLUSIONS

This systematic review reported recent progression in the development of HTLV-1 vaccines to identify candidates with the most promising preventive and therapeutic effects.

Primary cells from patients with adult T cell leukemia/lymphoma depend on HTLV-1 Tax expression for NF-κB activation and survival

Adult T cell leukemia/lymphoma (ATL) is an aggressive malignancy secondary to chronic infection with human T cell leukemia virus type 1 (HTLV-1). The viral oncoprotein Tax initiates T cell transformation through activation of critical cellular pathways, including NF-κB. Unexpectedly, Tax protein is not detectable in most ATL cells, in contrast to the HTLV-1 HBZ protein which antagonizes Tax effects. Here, we demonstrate that primary ATL cells from patients with acute or chronic ATL express very low levels of Tax mRNA and protein. Critically, survival of these primary ATL cells is dependent on continued Tax expression. Mechanistically, Tax extinction results in reversal of NF-κB activation, P53/PML activation and apoptosis. Tax drives interleukin-10 (IL-10) expression and recombinant IL-10 rescues the survival of tax-depleted primary ATL cells. These results demonstrate the critical role of continued Tax and IL-10 expression for the survival of primary ATL cells, highlighting their relevance as therapeutic targets.

How Can We Prevent Mother-to-Child Transmission of HTLV-1?

The perception of human T-cell leukemia virus type 1 (HTlV-1) infection as a "silent disease" has recently given way to concern that its presence may be having a variety of effects. HTLV-1 is known to cause adult T-cell leukemia (ATL), an aggressive cancer of peripheral CD4 T cells; however, it is also responsible for HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Most patients develop ATL as a result of HTLV-1 mother-to-child transmission. The primary route of mother-to-child transmission is through the mother's milk. In the absence of effective drug therapy, total artificial nutrition such as exclusive formula feeding is a reliable means of preventing mother-to-child transmission after birth, except for a small percentage of prenatal infections. A recent study found that the rate of mother-to-child transmission with short-term breastfeeding (within 90 days) did not exceed that of total artificial nutrition. Because these preventive measures are in exchange for the benefits of breastfeeding, clinical applications of antiretroviral drugs and immunotherapy with vaccines and neutralizing antibodies are urgently needed.

Live attenuated VZV vaccination induces antitumor immunity in ATLL patients

Adult T cell leukemia/lymphoma (ATLL) is a CD4-positive peripheral T cell lymphoma caused by human T cell lymphotropic virus type 1 (HTLV-1). Although ATLL is quite difficult to be cured, up-regulation of cellular immunity such as HTLV-1 Tax-specific cytotoxic T lymphocytes (CTLs) has been proved to be important to obtain long-term survival. At present, no efficacious method to activate ATLL-specific cellular immunity is available. This study aimed to investigate whether live attenuated varicella-zoster virus (VZV) vaccination to ATLL can activate HTLV-1 Tax-specific cellular immune response. A total of 3 indolent- and 3 aggressive-type ATLL patients were enrolled. All aggressive-type patients had the VZV vaccination after completing anti-ATLL treatment including mogamulizumab, which is a monoclonal antibody for C-C chemokine receptor 4 antigen, plus combination chemotherapy, whereas all indolent-type patients had the VZV vaccination without any antitumor treatment. Cellular immune responses including Tax-specific CTLs were analyzed at several time points of pre- and post-VZV vaccination. After the VZV vaccination, a moderate increase in 1 of 3 indolent-type patients and obvious increase in all 3 aggressive-type patients in Tax-specific CTLs percentage were observed. The increase in the cell-mediated immunity against VZV was observed in all indolent- and aggressive-type patients after VZV vaccination. To conclude, VZV vaccination to aggressive-type ATLL patients after mogamulizumab plus chemotherapy led to the up-regulation of HTLV-1 Tax-specific CTLs without any adverse event. Suppression of regulatory T lymphocytes by mogamulizumab may have contributed to increase tumor immunity in aggressive-type ATLL patients. Japan Registry of Clinical Trials number, jRCTs051180107.

Diversity of HLA-A2-Restricted and Immunodominant Epitope Repertoire of Human T-Lymphotropic Virus Type 1 (HTLV-1) Tax Protein: Novel Insights among N-Terminal, Central and C-Terminal Regions

The present study sought to search for the immunodominance related to the N-terminal, Central and C-terminal regions of HTLV-1 Tax using novel, cutting-edge peptide microarray analysis. In addition, in silico predictions were performed to verify the presence of nine amino acid peptides present along Tax restricted to the human leukocyte antigen (HLA)-A2.02*01 haplotype, as well as to verify the ability to induce pro-inflammatory and regulatory cytokines, such as IFN-γ and IL-4, respectively. Our results indicated abundant dose-dependent reactivity for HLA-A*02:01 in all regions (N-terminal, Central and C-terminal), but with specific hotspots. Furthermore, the results of fold-change over the Tax11–19 reactivity obtained at lower concentrations of HLA-A*02:01 reveal that peptides from the three regions contain sequences that react 100 times more than Tax11–19. On the other hand, Tax11–19 has similar or superior HLA-A*02:01 reactivity at higher concentrations of this haplotype. The in silico analysis showed a higher frequency of IFN-γ-inducing peptides in the N-terminal portion, while the C-terminal portion showed a higher frequency of IL-4 inducers. Taken together, these results shed light on the search for new Tax immunodominant epitopes, in addition to the canonic Tax11–19, for the rational design of immunomodulatory strategies for HTLV-1 chronic diseases.

Current and emerging therapeutic strategies in adult T-cell leukemia-lymphoma

Adult T-cell leukemia-lymphoma (ATL) is classified into four clinical subtypes: acute, lymphoma, chronic, and smoldering. Chronic ATL is further divided into unfavorable and favorable chronic types according to serum lactate dehydrogenase, blood urea nitrogen, and serum albumin values. Acute, lymphoma, and unfavorable chronic types are categorized as aggressive ATL, whereas favorable chronic and smoldering types are categorized as indolent ATL. Intensive chemotherapy alone is not sufficient to prevent relapse of aggressive ATL. Allogeneic hematopoietic stem cell transplantation is a potential therapeutic option to cure aggressive ATL in younger patients. Reduced-intensity conditioning regimens have decreased transplantation-related mortality, and increased donor availability has dramatically improved transplant access. New agents, including mogamulizumab, brentuximab vedotin, tucidinostat, and valemetostat, have recently become available for patients with aggressive ATL in Japan. Here, I provide an overview of recent advances in therapeutic strategies for ATL.

Vaccination with short-term-cultured autologous PBMCs efficiently activated STLV-1-specific CTLs in naturally STLV-1-infected Japanese monkeys with impaired CTL responses

A small proportion of human T-cell leukemia virus type-1 (HTLV-1)-infected individuals develop adult T-cell leukemia/lymphoma, a chemotherapy-resistant lymphoproliferative disease with a poor prognosis. HTLV-1-specific cytotoxic T lymphocytes (CTLs), potential anti-tumor/virus effectors, are impaired in adult T-cell leukemia/lymphoma patients. Here, using Japanese monkeys naturally infected with simian T-cell leukemia/T-lymphotropic virus type-1 (STLV-1) as a model, we demonstrate that short-term-cultured autologous peripheral blood mononuclear cells (PBMCs) can serve as a therapeutic vaccine to activate such CTLs. In a screening test, STLV-1-specific CTL activity was detectable in 8/10 naturally STLV-1-infected monkeys. We conducted a vaccine study in the remaining two monkeys with impaired CTL responses. The short-term-cultured PBMCs of these monkeys spontaneously expressed viral antigens, in a similar way to PBMCs from human HTLV-1 carriers. The first monkey was subcutaneously inoculated with three-day-cultured and mitomycin C (MMC)-treated autologous PBMCs, and then boosted with MMC-treated autologous STLV-1-infected cell line cells. The second monkey was inoculated with autologous PBMC-vaccine alone twice. In addition, a third monkey that originally showed a weak STLV-1-specific CTL response was inoculated with similar autologous PBMC-vaccines. In all three vaccinated monkeys, marked activation of STLV-1-specific CTLs and a mild reduction in the STLV-1 proviral load were observed. Follow-up analyses on the two monkeys vaccinated with PBMCs alone indicated that STLV-1-specific CTL responses peaked at 3-4 months after vaccination, and then diminished but remained detectable for more than one year. The significant reduction in the proviral load and the control of viral expression were associated with CTL activation but also diminished 6 and 12 months after vaccination, respectively, suggesting the requirement for a booster. The vaccine-induced CTLs in these monkeys recognized epitopes in the STLV-1 Tax and/or Envelope proteins, and efficiently killed autologous STLV-1-infected cells in vitro. These findings indicated that the autologous PBMC-based vaccine could induce functional STLV-1-specific CTLs in vivo.

Viral, genetic, and immune factors in the oncogenesis of adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATL) is a malignancy of mature CD4 + T cells induced by human T-cell leukemia virus type I (HTLV-1). HTLV-1 maintains life-long infection in the human host by clonal proliferation of infected cells and cell-to-cell spread of the virus. Two viral genes, tax and HTLV-1 bZIP factor (HBZ), promote expansion of infected cells through the important roles they play in acceleration of cell proliferation and protection from cell death. Long-term survival of infected clones in vivo causes genetic mutations and aberrant epigenetic changes to accumulate in host genes, resulting in the emergence of an ATL clone. Recent advances in sequencing technology have revealed the broad picture of genetic and transcriptional abnormalities in ATL cells. ATL cells have hyper-proliferative and anti-apoptotic signatures like those observed in other malignancies, but also notably have traits related to immune evasion. ATL cells exhibit a regulatory T-cell-like immuno-phenotype due to both the function of HBZ and mutation of several host genes, such as CCR4 and CIC. These findings suggest that immune evasion is a critical step in the oncogenesis of ATL, and thus novel therapies that activate anti-ATL/HTLV-1 immunity may be effective in the treatment and prevention of ATL.

Advances in preventive vaccine development against HTLV-1 infection: A systematic review of the last 35 years

Introduction

The Human T-lymphotropic virus type 1 (HTLV-1) was the first described human retrovirus. It is currently estimated that around 5 to 10 million people worldwide are infected with this virus. Despite its high prevalence, there is still no preventive vaccine against the HTLV-1 infection. It is known that vaccine development and large-scale immunization play an important role in global public health. To understand the advances in this field we performed a systematic review regarding the current progress in the development of a preventive vaccine against the HTLV-1 infection.

Methods

This review followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA®) guidelines and was registered at the International Prospective Register of Systematic Reviews (PROSPERO). The search for articles was performed in PubMed, Lilacs, Embase and SciELO databases. From the 2,485 articles identified, 25 were selected according to the inclusion and exclusion criteria.

Results

The analysis of these articles indicated that potential vaccine designs in development are available, although there is still a paucity of studies in the human clinical trial phase.

Discussion

Although HTLV-1 was discovered almost 40 years ago, it remains a great challenge and a worldwide neglected threat. The scarcity of funding contributes decisively to the inconclusiveness of the vaccine development. The data summarized here intends to highlight the necessity to improve the current knowledge of this neglected retrovirus, encouraging for more studies on vaccine development aiming the to eliminate this human threat.

Systematic review registration

https://www.crd.york.ac.uk/prospero, identifier (CRD42021270412).

Immunotherapy approaches for hematological cancers

Hematological cancers such as leukemia, lymphoma, and multiple myeloma have traditionally been treated with chemo and radiotherapy approaches. Introduction of immunotherapies for treatment of these diseases has led to patient remissions that would not have been possible with traditional approaches. In this critical review we identify main disease characteristics, symptoms, and current treatment options. Five common immunotherapies, namely checkpoint inhibitors, vaccines, cell-based therapies, antibodies, and oncolytic viruses, are described, and their applications in hematological cancers are critically discussed.

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.

Interplay between innate immunity and the viral oncoproteins Tax and HBZ in the pathogenesis and therapeutic response of HTLV-1 associated adult T cell leukemia

The Human T-cell Leukemia virus type 1 (HTLV-1) causes an array of pathologies, the most aggressive of which is adult T-cell leukemia (ATL), a fatal blood malignancy with dismal prognosis. The progression of these diseases is partly ascribed to the failure of the immune system in controlling the spread of virally infected cells. HTLV-1 infected subjects, whether asymptomatic carriers or symptomatic patients are prone to opportunistic infections. An increasing body of literature emphasizes the interplay between HTLV-1, its associated pathologies, and the pivotal role of the host innate and adoptive immune system, in shaping the progression of HTLV-1 associated diseases and their response to therapy. In this review, we will describe the modalities adopted by the malignant ATL cells to subvert the host innate immune response with emphasis on the role of the two viral oncoproteins Tax and HBZ in this process. We will also provide a comprehensive overview on the function of innate immunity in the therapeutic response to chemotherapy, anti-viral or targeted therapies in the pre-clinical and clinical settings.

The Past, Present, and Future of a Human T-Cell Leukemia Virus Type 1 Vaccine

Human T-cell leukemia virus type 1 (HTLV-1) is an oncogenic human retrovirus which causes a lifelong infection. An estimated 5-10 million persons are infected with HTLV-1 worldwide - a number which is likely higher due to lack of reliable epidemiological data. Most infected individuals remain asymptomatic; however, a portion of HTLV-1-positive individuals will develop an aggressive CD4+ T-cell malignancy called adult T-cell leukemia/lymphoma (ATL), or a progressive neurodegenerative disease known as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Few treatment options exist for HAM/TSP outside of palliative care and ATL carries an especially poor prognosis given the heterogeneity of the disease and lack of effective long-term treatments. In addition, the risk of HTLV-1 disease development increases substantially if the virus is acquired early in life. Currently, there is no realistic cure for HTLV-1 infection nor any reliable measure to prevent HTLV-1-mediated disease development. The severity of HTLV-1-associated diseases (ATL, HAM/TSP) and limited treatment options highlights the need for development of a preventative vaccine or new therapeutic interventions. This review will highlight past HTLV-1 vaccine development efforts, the current molecular tools and animal models which might be useful in vaccine development, and the future possibilities of an effective HTLV-1 vaccine.

A role for an HTLV-1 vaccine?

HTLV-1 is a global infection with 5-20 million infected individuals. Although only a minority of infected individuals develop myelopathy, lymphoproliferative malignancy, or inflammatory disorders, infection is associated with immunosuppression and shorter survival. Transmission of HTLV-1 is through contaminated blood or needles, mother-to-child exposure through breast-feeding, and sexual intercourse. HTLV-1 is a delta retrovirus that expresses immunogenic Gag, Envelope, TAX, and Hbz proteins. Neutralizing antibodies have been identified directed against the surface envelope protein, and cytotoxic T-cell epitopes within TAX have been characterized. Thus far, there have been few investigations of vaccines directed against each of these proteins, with limited responses, thus far. However, with new technologies developed in the last few years, a renewed investigation is warranted in search for a safe and effective HTLV-1 vaccine.

Adult T-Cell Leukemia: a Comprehensive Overview on Current and Promising Treatment Modalities

PURPOSE OF THE REVIEW

Adult T-cell leukemia (ATL) is an aggressive chemo-resistant malignancy secondary to HTLV-1 retrovirus. Prognosis of ATL remains dismal. Herein, we emphasized on the current ATL treatment modalities and their drawbacks, and opened up on promising targeted therapies with special focus on the HTLV-1 regulatory proteins Tax and HBZ.

RECENT FINDINGS

Indolent ATL and a fraction of acute ATL exhibit long-term survival following antiviral treatment with zidovudine and interferon-alpha. Monoclonal antibodies such as mogamulizumab improved response rates, but with little effect on survival. Allogeneic hematopoietic cell transplantation results in long-term survival in one third of transplanted patients, alas only few patients are transplanted. Salvage therapy with lenalidomide in relapsed/refractory patients leads to prolonged survival in some of them. ATL remains an unmet medical need. Targeted therapies focusing on the HTLV-1 viral replication and/or viral regulatory proteins, as well as on the host antiviral immunity, represent a promising approach for the treatment of ATL.

Tumorigenesis and diagnostic practice applied in two oncogenic viruses: Epstein Barr virus and T-cell lymphotropic virus-1-Mini review

To date, seven viruses have been reliably connected to various forms of human cancer: Epstein Barr Virus (EBV), Kaposi's sarcoma-associated herpesvirus (KSHV), high-risk Human papillomavirus (HPV), Merkel Cell Polyomavirus (MCPV), Hepatitis B virus (HBV), hepatitis C virus (HCV), and Human T-cell leukemia virus type 1 (HTLV1). This mini-review summarizes two of these viruses, EPV and HTLV-1, in terms of their general pathway of infection, the key mechanism of cancer induction, and the prominent technologies used to detect the infections. EBV is the first discovered human oncovirus and HTLV - I is the first human retrovirus and both were discovered from patient with distinct lymphoma clinical condition. Both the viruses can immortalize lymphocytes invitro and lymphomas are common manifestation of majority oncogenic viruses. Lymphomagenesis are discovered in associated with EBV, HTLV-I, Human Immunodeficiency virus (HIV), Kaposi sarcoma - associated herpes virus and hepatitis c virus. Later the undefined mechanism behind the induction of cancer by these viruses was unveiled gradually along with the responsible cofactors and mimicry mechanism. These two viruses contrast in their genetic structure, location of the infection, and latency, yet clinically, they generate similar cancer disorders. The major focus of this study is to brief the mechanism of these two unrelated viral cancer promoting agents on how they simulate a condition similar to lymphoma which may or may not undergo mimicry and cofactor utilization process, handpicked and vital genes behind the transformation mechanism are given accordingly.

PD-1 and PD-L1 inhibitors foster the progression of adult T-cell Leukemia/Lymphoma

Immunotherapy through immune checkpoints blockade and its subsequent clinical application has revolutionized the treatment of a spectrum of solid tumors. Blockade of Programmed cell death protein-1 and its ligand has shown promising results in clinical studies. The clinical trials that enrolled patients with different hematopoietic malignancies including non-Hodgkin lymphoma, Hodgkin lymphoma, and acute myeloid leukemia (AML) showed that anti-PD-1 agents could have potential therapeutic effects in the patients. Adult T-cell leukemia/lymphoma (ATLL) is a non-Hodgkin T-cell Lymphoma that is developed in a minority of HTLV-1-infected individuals after a long latency period. The inhibition of PD-1 as a treatment option is currently being investigated in ATLL patients. In this review, we present a summary of the biology of the PD-1/PD-L1 pathway, the evidence in the literature to support anti-PD-1/PDL-1 application in the treatment of different lymphoid, myeloid, and virus-related hematological malignancies, and controversies related to PD-1/PD-L1 blocking in the management of ATLL patients.

How I treat adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATL) is a highly aggressive T-cell malignancy that arises in a proportion of individuals who are long-term carriers of human T-lymphotropic virus type 1. The median survival of aggressive subtypes is 8 to 10 months; with chemotherapy-based approaches, overall survival has remained largely unchanged in the ∼35 years since ATL was first described. Through the use of 4 representative case studies, we highlight advances in the biological understanding of ATL and the use of novel therapies such as mogamulizumab, as well as how they are best applied to different subtypes of ATL. We discuss the implementation of molecular methods that may guide diagnosis or treatment, although we accept that these are not universally available. In particular, we acknowledge discrepancies in treatment between different countries, reflecting current drug licensing and the difficulties in making treatment decisions in a rare disease, with limited high-quality clinical trial data.

Mogamulizumab for adult T-cell leukemia-lymphoma: a multicenter prospective observational study

Monitoring of Immune Responses Following Mogamulizumab-Containing Treatment in Patients with Adult T-Cell Leukemia-Lymphoma (ATL) (MIMOGA) is a multicenter prospective observational study to establish the most effective and safe treatment strategy using mogamulizumab for ATL patients (UMIN000008696). Mogamulizumab-naive patients were enrolled (n = 102), of whom 101 received mogamulizumab-containing treatment (68 acute, 18 lymphoma, 12 chronic, and 3 smoldering subtypes). At enrollment, there was a significant inverse correlation between serum soluble interleukin-2 receptor (sIL-2R) levels and percentages of Tax-specific cytotoxic T lymphocytes (Tax-CTLs) in the entire lymphocyte population or in the CD8+ T cell subset, but there was not a correlation with cytomegalovirus pp65-specific cytotoxic T lymphocytes (CMV-CTLs). The overall response rate was 65%, and median progression-free survival and overall survival (OS) were 7.4 and 16.0 months, respectively. A higher percentage of Tax-CTLs, but not CMV-CTLs, within the entire lymphocyte population or in the CD8+ T cell subset was significantly associated with longer survival. Multivariate analysis identified the clinical subtype (acute or lymphoma type), a higher sIL-2R level, and a lower percentage of CD2-CD19+ B cells in peripheral blood mononuclear cells as significant independent unfavorable prognostic factors for OS. This indicates that a higher percentage of B cells might reflect some aspect of a favorable immune status leading to a good outcome with mogamulizumab treatment. In conclusion, the MIMOGA study has demonstrated that mogamulizumab exerts clinically meaningful antitumor activity in ATL. The patient's immunological status before mogamulizumab was significantly associated with treatment outcome. Further time series immunological analyses, in addition to comprehensive genomic analyses, are warranted.

Loss of interleukin-10 activates innate immunity to eradicate adult T-cell leukemia-initiating cells

Adult T-cell leukemia/lymphoma (ATL) is associated with chronic human T-cell leukemia virus type 1 infection and carries a poor pr o gnosi s. Arsenic tr ioxide (AS) and inter feron-alpha (IFN) together selectively trigger Tax viral oncoprotein degradation and cure Tax-driven murine ATL. AS/IFN/zidovudine treatment achieves a high response rate in patients with chronic ATL. Interleukin 10 (IL-10) is an immuno-suppressive cytokine whose expression is activated by Tax. Here we show that, in ATL, AS/IFN-induced abrogation of leukemiainitiating cell activity requires IL-10 expression shutoff. Loss of IL-10 secretion drives production of inflammatory cytokines by the microenvironment, followed by innate immunity-mediated clearance of Tax-driven leukemic cells. Accordingly, anti-IL-10 monoclonal antibodies significantly increased the efficiency of AS/IFNtherapy. These results emphasize the sequential targeting of malignant ATL cells and their immune microenvironment in leukemia-initiating cell eradication and provide a strong rationale to test the AS/IFN/anti-IL10 combination in ATL.

Adult T-cell leukemia-lymphoma as a viral disease: Subtypes based on viral aspects

Adult T-cell leukemia-lymphoma (ATL) is caused by human T-cell leukemia virus type 1 (HTLV-1) infection. Among HTLV-1 encoded genes, HTLV-1 bZIP factor (HBZ) and tax are critical for the leukemogenesis of ATL. Adult T-cell leukemia-lymphoma needs a long latent period before onset, indicating that both viral genes and alterations (genetic and epigenetic) of the host genome play important roles for leukemogenesis. Viral genes influence genetic and epigenetic changes of the host genome, indicating that the virus is of primary importance in leukemogenesis. HBZ is expressed in all ATL cases, whereas Tax expression is heterogeneous among ATL cases. Different patterns of viral gene expression in tumors are also observed for Epstein-Barr virus. We propose three subtypes of ATL cases based on Tax expression: high, intermittent, and lost expression. HBZ is detected in all ATL cases. Approximately 25% of all ATL cases lost Tax expression at infection of HTLV-1, indicating that HBZ is the only viral gene responsible for leukemogenesis in addition to genetic and epigenetic changes of the host genes in these ATL cases. The host immune responses to Tax are also implicated in the heterogeneity of ATL. Thus, ATL is a heterogeneous disease in terms of its viral gene expression, which is important for pathogenesis of this intractable lymphomatous neoplasm.

Short-term cultured autologous peripheral blood mononuclear cells as a potential immunogen to activate Tax-specific CTL response in adult T-cell leukemia patients

Activation of CD8⁺ Tax‐specific CTL is a new therapeutic concept for adult T‐cell leukemia (ATL) caused by HTLV‐1. A recent clinical study of the dendritic cell vaccine pulsed with Tax peptides corresponding to CTL epitopes showed promising outcomes in ATL patients possessing limited human leukocyte antigen (HLA) alleles. In this study, we aimed to develop another immunotherapy to activate Tax‐specific CTL without HLA limitation by using patients’ own HTLV‐1‐infected cells as a vaccine. To examine the potential of HTLV‐1‐infected T‐cells to activate CTL via antigen presenting cells, we established a unique co–culture system. We demonstrated that mitomycin C‐treated HLA‐A2‐negative HTLV‐1‐infected T‐cell lines or short‐term cultured peripheral blood mononuclear cells (PBMC) derived from ATL patients induced cross–presentation of Tax antigen in co–cultured HLA‐A2‐positive antigen presenting cells, resulting in activation of HLA‐A2‐restricted CD8⁺ Tax‐specific CTL. This effect was not inhibited by a reverse transcriptase inhibitor. IL‐12 production and CD86 expression were also induced in antigen presenting cells co–cultured with HTLV‐1‐infected cells at various levels, which were improved by pre–treatment of the infected cells with histone deacetylase inhibitors. Furthermore, monocyte‐derived dendritic cells induced from PBMC of a chronic ATL patient produced IL‐12 and expressed enhanced levels of CD86 when co–cultured with autologous lymphocytes that had been isolated from the same PBMC and cultured for several days. These findings suggest that short‐term cultured autologous PBMC from ATL patients could potentially serve as a vaccine to evoke Tax‐specific CTL responses.

Human T-cell lymphotropic virus HBZ and tax mRNA expression are associated with specific clinicopathological features in adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATLL) is caused by human T-cell leukemia virus type 1 (HTLV-1). HTLV-1-associated mRNA, including HBZ and tax, is deeply involved in the pathogenesis of ATLL. Using 88 ATLL tissue samples, we performed in situ mRNA analysis of HBZ and tax, and investigated its association with clinicopathological characteristics of ATLL. The median value of HBZ signals (/1000 ATLL cells) was 795.2 (range: 0.4-4013.1) and of tax signals (/1000 ATLL cells) was 5.1 (range: 0.1-891.2). The low-expression HBZ group displayed significant increase in the number of skin lesion (P = 0.0283). The high-expression tax group displayed significant increase in the number of PD-1-positive tumor-infiltrating lymphocytes (P < 0.0001). In addition, we identified patients with very high-expression of tax signals (400 or more signals/1000 ATLL cells). These patients displayed significant reductions in the expression of HLA class I (P = 0.0385) and β2M (P = 0.0124). Moreover, these patients displayed significantly poor overall survival (median survival time [MST] 7.7 months, 95% confidence interval [CI] [4.7-NA]), compared with the survival in patients with less than 400 tax signals (MST 22.6 months, 95% CI [13.7-41.7]) (P = 0.0499). These results suggest that Tax-mediated treatment of ATLL should be performed carefully in the high-expression tax group. More detailed studies could elucidate the clinicopathological significance of HBZ and tax mRNA expressions in ATLL.

In vivo dynamics and adaptation of HTLV-1-infected clones under different clinical conditions

Human T-cell leukemia virus type 1 (HTLV-1) spreads through cell contact. Therefore, this virus persists and propagates within the host by two routes: clonal proliferation of infected cells and de novo infection. The proliferation is influenced by the host immune responses and expression of viral genes. However, the detailed mechanisms that control clonal expansion of infected cells remain to be elucidated. In this study, we show that newly infected clones were strongly suppressed, and then stable clones were selected, in a patient who was infected by live liver transplantation from a seropositive donor. Conversely, most HTLV-1⁺ clones persisted in patients who received hematopoietic stem cell transplantation from seropositive donors. To clarify the role of cell-mediated immunity in this clonal selection, we suppressed CD8⁺ or CD16⁺ cells in simian T-cell leukemia virus type 1 (STLV-1)-infected Japanese macaques. Decreasing CD8⁺ T cells had marginal effects on proviral load (PVL). However, the clonality of infected cells changed after depletion of CD8⁺ T cells. Consistent with this, PVL at 24 hours in vitro culture increased, suggesting that infected cells with higher proliferative ability increased. Analyses of provirus in a patient who received Tax-peptide pulsed dendritic cells indicate that enhanced anti-Tax immunity did not result in a decreased PVL although it inhibited recurrence of ATL. We postulate that in vivo selection, due to the immune response, cytopathic effects of HTLV-1 and intrinsic attributes of infected cells, results in the emergence of clones of HTLV-1-infected T cells that proliferate with minimized HTLV-1 antigen expression.

HTLV-1 spreads in vivo through two routes: de novo infection and clonal proliferation of infected cells. Reverse transcriptase inhibitors and integrase inhibitors do not influence the PVL in HTLV-1-infected individuals, indicating that clonal proliferation is dominant to maintain and increase PVL in vivo in the chronic phase. It is assumed that the host immune responses are critical factors for clonal proliferation. We found that HTLV-1-infected clones dramatically changed during de novo infection whereas the clones in the chronic phase survived long-term after transplantation, indicating that HTLV-1-infected clones are selected for survival in vivo. Surprisingly, depletion of CD8⁺ cells had a small impact on PVL in a STLV-1 infected Japanese macaque, but modified the clonality of infected cells. The cells after depletion of CD8⁺ cells showed a higher proliferative activity during short-term in vitro culture. This study reveals that intrinsic attributes of selected clones contribute to clonal proliferation of infected cells.

The Nature of the HTLV-1 Provirus in Naturally Infected Individuals Analyzed by the Viral DNA-Capture-Seq Approach

The retrovirus human T-cell leukemia virus type 1 (HTLV-1) integrates into the host DNA, achieves persistent infection, and induces human diseases. Here, we demonstrate that viral DNA-capture sequencing (DNA-capture-seq) is useful to characterize HTLV-1 proviruses in naturally virus-infected individuals, providing comprehensive information about the proviral structure and the viral integration site. We analyzed peripheral blood from 98 naturally HTLV-1-infected individuals and found that defective proviruses were present not only in patients with leukemia, but also in those with other clinical entities. We further demonstrated that clones with defective-type proviruses exhibited a higher degree of clonal abundance than those with full-length proviruses. The frequency of defective-type proviruses in HTLV-1-infected humanized mice was lower than that in infected individuals, indicating that defective proviruses were rare at the initial phase of infection but preferentially selected during persistent infection. These results demonstrate the robustness of viral DNA-capture-seq for HTLV-1 infection and suggest potential applications for other virus-associated cancers in humans.

Novel Treatments of Adult T Cell Leukemia Lymphoma

Adult T cell leukemia-lymphoma (ATL) is an aggressive malignancy secondary to chronic infection with the human T cell leukemia virus type I (HTLV-I) retrovirus. ATL carries a dismal prognosis. ATL classifies into four subtypes (acute, lymphoma, chronic, and smoldering) which display different clinical features, prognosis and response to therapy, hence requiring different clinical management. Smoldering and chronic subtypes respond well to antiretroviral therapy using the combination of zidovudine (AZT) and interferon-alpha (IFN) with a significant prolongation of survival. Conversely, the watch and wait strategy or chemotherapy for these indolent subtypes allies with a poor long-term outcome. Acute ATL is associated with chemo-resistance and dismal prognosis. Lymphoma subtypes respond better to intensive chemotherapy but survival remains poor. Allogeneic hematopoietic stem cell transplantation (HSCT) results in long-term survival in roughly one third of transplanted patients but only a small percentage of patients can make it to transplant. Overall, current treatments of aggressive ATL are not satisfactory. Prognosis of refractory or relapsed patients is dismal with some encouraging results when using lenalidomide or mogamulizumab. To overcome resistance and prevent relapse, preclinical or pilot clinical studies using targeted therapies such as arsenic/IFN, monoclonal antibodies, epigenetic therapies are promising but warrant further clinical investigation. Anti-ATL vaccines including Tax peptide-pulsed dendritic cells, induced Tax-specific CTL responses in ATL patients. Finally, based on the progress in understanding the pathophysiology of ATL, and the risk-adapted treatment approaches to different ATL subtypes, treatment strategies of ATL should take into account the host immune responses and the host microenvironment including HTLV-1 infected non-malignant cells. Herein, we will provide a summary of novel treatments of ATL in vitro, in vivo, and in early clinical trials.

Development of a Unique T Cell Receptor Gene-Transferred Tax-Redirected T Cell Immunotherapy for Adult T Cell Leukemia

Adult T cell leukemia/lymphoma (ATL) is an aggressive peripheral T cell neoplasm caused by infection with human T cell lymphotropic virus type-1 (HTLV-1). Its prognosis remains extremely poor. Tax, the most important regulatory protein for HTLV-1, is associated with the aggressive proliferation of host cells and is also a major target antigen for CD8⁺ cytotoxic T cells (CTLs). Based on our previous findings that Tax-specific CTLs with a T cell receptor (TCR) containing a unique amino-acid sequence motif exhibit strong HLA-A*24:02-restricted, Tax_301-309-specific activity against HTLV-1, we aimed to develop a Tax-redirected T cell immunotherapy for ATL. TCR-ɑ/β genes were cloned from a previously established CTL clone and transduced into peripheral blood mononuclear cells (PBMCs) of healthy volunteers using a retroviral siTCR vector. Then the cytotoxic efficacy against HTLV-1-infected T cells or primary ATL cells was assessed both in vitro and in vivo. The redirected CTLs (Tax-siCTLs) produced a large amount of cytokines and showed strong killing activity against ATL/HTLV-1-infected T cells in vitro, although they did not have universal activity against ATL cells. Next, in a xenograft mouse model using an HTLV-1-infected T cell line (MT-2), in all mice treated with Tax-siCTLs, the tumor rapidly diminished and finally disappeared without normal tissue damage, although all mice that were untreated or treated with non-gene-modified PBMCs died because of tumor progression. Our findings confirm that Tax-siCTLs can exert strong anti-ATL/HTLV-1 effects without a significant reaction against normal cells and have the potential to be a novel immunotherapy for ATL patients.

HTLV-1 in Ophthalmology

Human T-cell leukemia virus type 1 (HTLV-1) was the first retrovirus described as a causative agent for human disease. In the field of ophthalmology, a close relationship between HTLV-1 infection and uveitis was identified through a series of clinical and laboratory studies in the late 1980s-1990s. Since then, HTLV-1-related ocular manifestations such as keratoconjunctivitis sicca, interstitial keratitis, optic neuritis and adult T-cell leukemia/lymphoma (ATL)-related ocular manifestations have continuously been reported. During the three decades since the association between HTLV-1 and ocular pathologies was discovered, ophthalmic practice and research have advanced with the incorporation of new technologies into the field of ophthalmology. Accordingly, new findings from recent research have provided many insights into HTLV-1-associated ocular diseases. Advanced molecular technologies such as multiplex polymerase chain reaction (PCR)/broad-range PCR using ocular samples have enabled rapid and accurate diagnosis. Advanced ophthalmic technologies such as widefield fundus camera and optical coherence tomography (OCT) have clarified various features of HTLV-1-associated ocular manifestations, and identified characteristics such as the "knob-like ATL cell multiple ocular infiltration" (KAMOI) sign. Advanced drug delivery methods such as intravitreal injection and sub-Tenon injection have led to progress in preventing disease progression. This article describes global topics and the latest research findings for HTLV-1-associated ocular diseases, with reference to a large-scale nationwide survey of ophthalmologists. Current approaches and unmet needs for HTLV-1 infection in ophthalmology are also discussed.

Molecular biology of human T cell leukemia virus

Human T cell leukemia virus type 1 (HTLV-1) is a horizontally transmitted virus infection of CD4+ lymphocytes which causes adult T cell leukemia-lymphoma (ATLL) and HTLV-associated myelopathy (HAM). The viral genome encodes two oncoproteins, transactivator protein (Tax) and helix basic zipper protein (HBZ), which are considered tumor initiator and maintenance factors, respectively. Tax is the primary inducer of clonal infected T cell expansion, and genetic instability. The immune response to Tax results in the selection of cells with little or no Tax expression, which have undergone genetic and epigenetic alterations that promote T cell activation, proliferation, and resistance to apoptosis. This selection of malignant cells occurs over several decades in 5% of infected individuals. Novel insights into the molecular details of each of these events has led to targeted therapies for ATLL.

HTLV-1 Infection and Rheumatic Diseases

Some major research and clinical questions about human T-cell leukemia virus type 1 (HTLV-1) infection and rheumatic diseases remain: (1) Does HTLV-1 infection cause rheumatic diseases? (2) Do patients with rheumatic diseases display different responses to treatment with anti-rheumatic agents when they are HTLV-1 carriers? (3) Is adult T-cell leukemia/lymphoma (ATL) or HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) more prevalent in HTLV-1 carriers with rheumatic diseases who are treated with anti-rheumatic agents? These questions are important because increasing numbers of patients with rheumatic diseases are currently receiving treatment with aggressive medicines such as immunosuppressants and biologics. Studies on HTLV-1 gene-transgenic mice have shown manifestations resembling rheumatic diseases. Epidemiological studies have shown a high incidence of HTLV-1 infection in patients with rheumatic diseases including rheumatoid arthritis (RA), Sjogren’s syndrome, and polymyositis. HTLV-1-positive and HTLV-1-negative patients with RA have displayed similar immunological features including the seroprevalence of anti-citrullinated peptide antibodies. Conversely, attenuated effectiveness of tumor necrosis factor inhibitors for HTLV-1-positive patients with RA in Japan has been reported. Therefore, although no direct evidence has shown that HTLV-1 infection alone causes rheumatic diseases, HTLV-1 may affect the inflammation of RA. Although the incidence of ATL or HAM/TSP among patients with rheumatic diseases has not been investigated in large-scale studies, ATL or HAM/TSP has developed among HTLV-1-positive patients with rheumatic diseases. HTLV-1 infection may affect the clinical course of patients with rheumatic diseases, particularly after receiving anti-rheumatic agents. Because studies on these issues are limited, further investigation with large sample sizes is necessary.

Sensitive Photodynamic Detection of Adult T-cell Leukemia/Lymphoma and Specific Leukemic Cell Death Induced by Photodynamic Therapy: Current Status in Hematopoietic Malignancies

Adult T-cell leukemia/lymphoma (ATL), an aggressive type of T-cell malignancy, is caused by the human T-cell leukemia virus type I (HTLV-1) infections. The outcomes, following therapeutic interventions for ATL, have not been satisfactory. Photodynamic therapy (PDT) exerts selective cytotoxic activity against malignant cells, as it is considered a minimally invasive therapeutic procedure. In PDT, photosensitizing agent administration is followed by irradiation at an absorbance wavelength of the sensitizer in the presence of oxygen, with ultimate direct tumor cell death, microvasculature injury, and induced local inflammatory reaction. This review provides an overview of the present status and state-of-the-art ATL treatments. It also focuses on the photodynamic detection (PDD) of hematopoietic malignancies and the recent progress of 5-Aminolevulinic acid (ALA)-PDT/PDD, which can efficiently induce ATL leukemic cell-specific death with minor influence on normal lymphocytes. Further consideration of the ALA-PDT/PDD system along with the circulatory system regarding the clinical application in ATL and others will be discussed. ALA-PDT/PDD can be promising as a novel treatment modality that overcomes unmet medical needs with the optimization of PDT parameters to increase the effectiveness of the tumor-killing activity and enhance the innate and adaptive anti-tumor immune responses by the optimized immunogenic cell death.