A heterocyclic compound inhibits viral release by inducing cell surface BST2/Tetherin/CD317/HM1.24.

The introduction of combined antiretroviral therapy (cART) has greatly improved the quality of life of human immunodeficiency virus type 1 (HIV-1)-infected individuals. Nonetheless, the ever-present desire to seek out a full remedy for HIV-1 infections makes the discovery of novel antiviral medication compelling. Owing to this, a new late-stage inhibitor, Lenacapavir/Sunlenca, an HIV multi-phase suppressor, was clinically authorized in 2022. Besides unveiling cutting-edge antivirals inhibiting late-stage proteins or processes, newer therapeutics targeting host restriction factors hold promise for the curative care of HIV-1 infections. Notwithstanding, bone marrow stromal antigen 2 (BST2)/Tetherin/CD317/HM1.24, which entraps progeny virions is an appealing HIV-1 therapeutic candidate. In this study, a novel drug screening system was established, using the Jurkat/Vpr-HiBiT T cells, to identify drugs that could obstruct HIV-1 release; the candidate compounds were selected from the Ono Pharmaceutical compound library. Jurkat T cells expressing Vpr-HiBiT were infected with NL4-3, and the amount of virus release was quantified indirectly by the amount of Vpr-HiBiT incorporated into the progeny virions. Subsequently, the candidate compounds that suppressed viral release were used to synthesize the heterocyclic compound, HT-7, which reduces HIV-1 release with less cellular toxicity. Notably, HT-7 increased cell surface BST2 coupled with HIV-1 release reduction in Jurkat cells but not Jurkat/KO-BST2 cells. Seemingly, HT-7 impeded simian immunodeficiency virus (SIV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) release. Concisely, these results suggest that the reduction in viral release, following HT-7 treatment, resulted from the modulation of cell surface expression of BST2 by HT-7.

HTLV-1 induces an inflammatory CD4+CD8+ T cell population in HTLV-1-associated myelopathy.

Human T cell leukemia virus type 1 (HTLV-1) is a retrovirus with preferential CD4+ T cell tropism that causes a range of conditions spanning from asymptomatic infection to adult T cell leukemia and HTLV-1-associated myelopathy (HAM), an inflammatory disease of the CNS. The mechanisms by which HTLV-1 induces HAM are poorly understood. By directly examining the ex vivo phenotype and function of T cells from asymptomatic carriers and patients with HAM, we show that patients with HAM have a higher frequency of CD4+CD8+ double-positive (DP) T cells, which are infected with HTLV-1 at higher rates than CD4+ T cells. Displaying both helper and cytotoxic phenotypes, these DP T cells are highly proinflammatory and contain high frequencies of HTLV-1-specific cells. Mechanistically, we demonstrate that DP T cells arise by direct HTLV-1 infection of CD4+ and CD8+ T cells. High levels of CD49d and CXCR3 expression suggest that DP T cells possess the ability to migrate to the CNS, and when cocultured with astrocytes, DP T cells induce proinflammatory astrocytes that express high levels of CXCL10, IFN-γ, and IL-6. These results demonstrate the potential of DP T cells to directly contribute to CNS pathology.

Interaction of TSG101 with the PTAP Motif in Distinct Locations of Gag Determines the Incorporation of HTLV-1 Env into the Retroviral Virion.

Human T-cell tropic virus type 1 (HTLV-1) is known to be mainly transmitted by cell-to-cell contact due to the lower infectivity of the cell-free virion. However, the reasons why cell-free HTLV-1 infection is poor remain unknown. In this study, we found that the retrovirus pseudotyped with HTLV-1 viral envelope glycoprotein (Env) was infectious when human immunodeficiency virus type 1 (HIV-1) was used to produce the virus. We found that the incorporation of HTLV-1 Env into virus-like particles (VLPs) was low when HTLV-1 Gag was used to produce VLPs, whereas VLPs produced using HIV-1 Gag efficiently incorporated HTLV-1 Env. The production of VLPs using Gag chimeras between HTLV-1 and HIV-1 Gag and deletion mutants of HIV-1 Gag showed that the p6 domain of HIV-1 Gag was responsible for the efficient incorporation of HTLV-1 Env into the VLPs. Further mutagenic analyses of the p6 domain of HIV-1 Gag revealed that the PTAP motif in the p6 domain of HIV-1 Gag facilitates the incorporation of HTLV-1 Env into VLPs. Since the PTAP motif is known to interact with tumor susceptibility gene 101 (TSG101) during the budding process, we evaluated the effect of TSG101 knockdown on the incorporation of HTLV-1 Env into VLPs. We found that TSG101 knockdown suppressed the incorporation of HTLV-1 Env into VLPs and decreased the infectivity of cell-free HIV-1 pseudotyped with HTLV-1 Env. Our results suggest that the interaction of TSG101 with the PTAP motif of the retroviral L domain is involved not only in the budding process but also in the efficient incorporation of HTLV-1 Env into the cell-free virus.

CD30 stimulation induces multinucleation and chromosomal instability in HTLV-1-infected cell lines.

A recent report indicated involvement of CD30 in progression of human leukemia virus type 1 (HTLV-1) infection, but the exact roles of CD30 in this process remain unclear. This study was conducted to determine the role of CD30 by stimulating CD30 expressed on HTLV-1-infected cell lines with CD30 ligand and observing its effects. CD30 stimulation increased multinucleated cells and inhibited proliferation of HTLV-1-infected cells. This inhibition was recovered by interruption of CD30 stimulation. Chromatin bridges found in multinucleated cells suggested DNA damage. CD30 stimulation triggered DNA double-strand breaks (DSBs) and chromosomal imbalances. CD30 stimulation induced reactive oxygen species (ROS), which induced DSBs. Generation of ROS and multinucleated cells by CD30 was dependent on phosphoinositide 3-kinase. RNA sequencing showed that CD30 stimulation produced significant changes in gene expression profiles, including upregulation of programmed death ligand 1 (PD-L1). Tax, which has also been shown to induce multinucleation and chromosomal instability, failed to induce CD30. These results suggest that induction of CD30, independent of Tax, triggers morphological abnormalities, chromosomal instability, and alteration of gene expression in HTLV-1-infected cells.

STLV-1 Commonly Targets Neurons in the Brain of Asymptomatic Non-Human Primates.

The human T-cell leukemia virus (HTLV)-1 is responsible for an aggressive neurodegenerative disease (HAM/TSP) and multiple neurological alterations. The capacity of HTLV-1 to infect central nervous system (CNS) resident cells, together with the neuroimmune-driven response, has not been well-established. Here, we combined the use of human induced pluripotent stem cells (hiPSC) and of naturally STLV-1-infected nonhuman primates (NHP) as models with which to investigate HTLV-1 neurotropism. Hence, neuronal cells obtained after hiPSC differentiation in neural polycultures were the main cell population infected by HTLV-1. Further, we report the infection of neurons with STLV-1 in spinal cord regions as well as in brain cortical and cerebellar sections of postmortem NHP. Additionally, reactive microglial cells were found in infected areas, suggesting an immune antiviral response. These results emphasize the need to develop new efficient models by which to understand HTLV-1 neuroinfection and suggest an alternative mechanism that leads to HAM/TSP.

Dynamics and consequences of the HTLV-1 proviral plus-strand burst.

Expression of the transcriptional transactivator protein Tax, encoded on the proviral plus-strand of human T-cell leukaemia virus type 1 (HTLV-1), is crucial for the replication of the virus, but Tax-expressing cells are rarely detected in fresh blood ex vivo. The dynamics and consequences of the proviral plus-strand transcriptional burst remain insufficiently characterised. We combined time-lapse live-cell imaging, single-cell tracking and mathematical modelling to study the dynamics of Tax expression at single-cell resolution in two naturally-infected, non-malignant T-cell clones transduced with a short-lived enhanced green fluorescent protein (d2EGFP) Tax reporter system. Five different patterns of Tax expression were observed during the 30-hour observation period; the distribution of these patterns differed between the two clones. The mean duration of Tax expression in the two clones was 94 and 417 hours respectively, estimated from mathematical modelling of the experimental data. Tax expression was associated with a transient slowing in cell-cycle progression and proliferation, increased apoptosis, and enhanced activation of the DNA damage response pathways. Longer-term follow-up (14 days) revealed an increase in the proportion of proliferating cells and a decrease in the fraction of apoptotic cells as the cells ceased Tax expression, resulting in a greater net expansion of the initially Tax-positive population. Time-lapse live-cell imaging showed enhanced cell-to-cell adhesion among Tax-expressing cells, and decreased cell motility of Tax-expressing cells at the single-cell level. The results demonstrate the within-clone and between-clone heterogeneity in the dynamics and patterns of HTLV-1 plus-strand transcriptional bursts and the balance of positive and negative consequences of the burst for the host cell.

Establishment of a Cynomolgus Macaque Model of Human T-Cell Leukemia Virus Type 1 (HTLV-1) Infection by Direct Inoculation of Adult T-Cell Leukemia Patient-Derived Cell Lines for HTLV-1 Infection.

Human T-cell leukemia virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). However, the precise mechanisms leading to HTLV-1 chronic infection and the onset of the diseases have remained unclear, and effective vaccines for inhibiting the infection and the progression of pathogenesis have therefore not been developed. The use of a nonhuman primate (NHP) model is thought to be important for revealing the mechanisms of the progressive status and for the development of prevention procedures. In this study, we developed a cynomolgus macaque (CM) model of HTLV-1 infection by direct intravenous inoculation of HTLV-1-producing cells derived from ATL patients. The cell line used for infection, ATL-040, was selected as the most infectious one in our cell line library. CMs inoculated intravenously with 1 × 108 ATL-040 cells per animal became persistently infected with HTLV-1, as shown by the HTLV-1 provirus load (PVL) in peripheral blood mononuclear cells and HTLV-1-specific antibodies (2/2 animals). One CM inoculated intravenously with 1 × 107 ATL-040 cells did not have detectable PVLs despite the fact that anti-HTLV-1 antibodies were maintained for more than 2 years. Furthermore, immunological approaches, including CD8+ T cell depletion prior to infection (3/3 animals) and intrathecal inoculation (3/3 animals), led to increased proviral loads in the cynomolgus monkeys. The present method and the cynomolgus monkey model of HTLV-1 infection will be beneficial for immunological and virological studies on HTLV-1 aiming at the development of anti-HTLV-1 prophylactic vaccines and therapy drugs. IMPORTANCE HTLV-1 was discovered in the 1980s as the causative agent of adult T-cell leukemia and HTLV-1-associated myelopathy/tropical spastic paraparesis. However, the precise mechanisms leading to HTLV-1 chronic infection and the onset of the diseases still remain unidentified. Thus, no effective vaccines to inhibit the infection and the progressive of pathogenesis have been developed. The use of appropriate animal models is essential for understanding HTLV-1 infection and pathogenesis. In order to establish a new nonhuman primate model for studies on HTLV-1 infection, cynomolgus monkeys were infected with HTLV-1 under a variety of experimental conditions. Our method, using a cell line generated from an ATL patient as a source of HTLV-1, was able to establish HTLV-1 infection in monkeys with a 100% success rate. This cynomolgus macaque model of HTLV-1 infection will contribute to the elucidation of HTLV-1 infection and its associated disease development.

A protective role of HTLV-1 gp46-specific neutralizing and antibody-dependent cellular cytotoxicity-inducing antibodies in progression to adult T-cell leukemia (ATL).

Human T-cell leukemia virus type-1 (HTLV-1) establishes a long-term persistent infection in humans and causes malignant T-cell leukemia, adult T-cell leukemia (ATL). HTLV-1-specific cytotoxic T lymphocytes have been suggested to play a major role in the immunosurveillance of HTLV-1-infected T cells. However, it remains unclear whether HTLV-1-specific functional antibodies are also involved in the host defense. To explore the role of antibodies in the course of HTLV-1 infection, we quantitated HTLV-1-specific neutralizing and antibody-dependent cellular cytotoxicity (ADCC)-inducing antibody levels in plasma from asymptomatic carriers (ACs) and ATL patients. The levels of neutralizing antibodies, as determined by a syncytium inhibition assay, were significantly lower in acute and chronic ATL patients than in ACs. The levels of ADCC-inducing activity were tested using an autologous pair of HTLV-1-producing cells and cultured natural killer (NK) cells, which showed that the ADCC-inducing activity of IgG at a concentration of 100 µg/ml was comparable between ACs and acute ATL patients. The anti-gp46 antibody IgG levels, determined by ELISA, correlated with those of the neutralizing and ADCC-inducing antibodies. In contrast, the proviral loads did not correlate with any of these antibody levels. NK cells and a monoclonal anti-gp46 antibody reduced the number of HTLV-1 Tax-expressing cells in cultured peripheral blood mononuclear cells from patients with aggressive ATL. These results suggest a protective role for HTLV-1 neutralizing and ADCC-inducing antibodies during the course of HTLV-1 infection.

Time-course of host cell transcription during the HTLV-1 transcriptional burst.

The human T-cell leukemia virus type 1 (HTLV-1) transactivator protein Tax has pleiotropic functions in the host cell affecting cell-cycle regulation, DNA damage response pathways and apoptosis. These actions of Tax have been implicated in the persistence and pathogenesis of HTLV-1-infected cells. It is now known that tax expression occurs in transcriptional bursts of the proviral plus-strand, but the effects of the burst on host transcription are not fully understood. We carried out RNA sequencing of two naturally-infected T-cell clones transduced with a Tax-responsive Timer protein, which undergoes a time-dependent shift in fluorescence emission, to study transcriptional changes during successive phases of the HTLV-1 plus-strand burst. We found that the transcriptional regulation of genes involved in the NF-κB pathway, cell-cycle regulation, DNA damage response and apoptosis inhibition were immediate effects accompanying the plus-strand burst, and are limited to the duration of the burst. The results distinguish between the immediate and delayed effects of HTLV-1 reactivation on host transcription, and between clone-specific effects and those observed in both clones. The major transcriptional changes in the infected host T-cells observed here, including NF-κB, are transient, suggesting that these pathways are not persistently activated at high levels in HTLV-1-infected cells. The two clones diverged strongly in their expression of genes regulating the cell cycle. Up-regulation of senescence markers was a delayed effect of the proviral plus-strand burst and the up-regulation of some pro-apoptotic genes outlasted the burst. We found that activation of the aryl hydrocarbon receptor (AhR) pathway enhanced and prolonged the proviral burst, but did not increase the rate of reactivation. Our results also suggest that sustained plus-strand expression is detrimental to the survival of infected cells.

Acute type adult T-cell leukemia cells proliferate in the lymph nodes rather than in peripheral blood.

A massive increase in the number of mature CD4+ T-cells in peripheral blood (PB) is a defining characteristic of acute type of adult T-cell leukemia (ATL). To date, the site of proliferation of ATL cells in the body has been unclear. In an attempt to address this question, we examined the expression of the proliferation marker, Ki-67, in freshly isolated ATL cells from PB and lymph nodes (LNs) of patients with various types of ATL. Our findings reveal that LN-ATL cells display higher expression of the Ki-67 antigen than PB-ATL cells in acute type patients. The gene expression of T-cell quiescence regulators such as Krüppel-like factor 2/6 and forkhead box protein 1 was substantially high in acute type PB-ATL cells. The expression of human telomerase reverse transcriptase, which is involved in T-cell expansion, was significantly low in PB-ATL cells from acute type patients, similar to that in normal resting T-cells. These findings suggest that ATL cells proliferate in the LNs rather than in PB.

Impact of anti-diabetic sodium-glucose cotransporter 2 inhibitors on tumor growth of intractable hematological malignancy in humans.

Under the dysfunction of mitochondria, cancer cells preferentially utilize both glycolytic and pentose phosphate pathways rather than electron transport chains to desperately generate adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate (reduced form) (NADPH), classically recognized as the Warburg effect. Based on this background, the present study tested the hypothesis that anti-diabetic sodium-glucose cotransporter 2 (SGLT2) inhibitors would exert a tumor-suppressive impact on intractable human hematological malignancies via the modulation of glucose metabolism within cells and cell cycles. The level of mRNA for SGLT2 was remarkably elevated in leukemic cells from patients with adult T-cell leukemia (ATL), one of the most intractable blood cancers in humans, and as well as in two kinds of ATL cell lines (MT-1 and MT-2). Two kinds of SGLT2 inhibitors, Luseogliflozin and Tofogliflozin substantially suppressed the proliferation of MT-1 and MT-2 cells in both adherent and anchorage-independent culture conditions. Such a suppressive effect on tumor cell growth was reproduced by Luseogliflozin in leukemic cells in peripheral blood from patients with ATL. In MT-2 cells, both of SGLT2 inhibitors considerably attenuated glucose uptake, intracellular ATP levels, and NADPH production, resultantly enhancing cell cycle arrest at the G0/G1 phase. From the standpoint of metabolic oncology, the present study suggests that SGLT2 inhibitors would be a promising adjunctive option for the treatment of the most intractable human hematological malignancies like ATL.

Elevation of the Plasma Levels of TNF Receptor 2 in Association with Those of CD25, OX40, and IL-10 and HTLV-1 Proviral Load in Acute Adult T-Cell Leukemia.

Adult T-cell leukemia/lymphoma (ATL) cells express TNF receptor type-2 (TNFR2) on their surface and shed its soluble form (sTNFR2). We previously reported that sTNFR2 levels were highly elevated in the plasma of patients with acute ATL. To investigate whether its quantitation would be helpful for the diagnosis or prediction of the onset of acute ATL, we examined the plasma levels of sTNFR2 in a large number of specimens obtained from a cohort of ATL patients and asymptomatic human T-cell leukemia virus type 1 (HTLV-1) carriers (ACs) and compared them to those of other candidate ATL biomarkers (sCD25, sOX40, and IL-10) by enzyme-linked immunosorbent assays (ELISA) and HTLV-1 proviral loads. We observed that sTNFR2 levels were significantly elevated in acute ATL patients compared to ACs and patients with other types of ATL (chronic, smoldering, and lymphoma). Importantly, sTNFR2 levels were significantly correlated with those of sCD25, sOX40, and IL-10, as well as proviral loads. Thus, the present study confirmed that an increase in plasma sTNFR2 levels is a biomarker for the diagnosis of acute ATL. Examination of plasma sTNFR2 alone or in combination with other ATL biomarkers may be helpful for the diagnosis of acute ATL.

Elucidation of the Mechanism of Host NMD Suppression by HTLV-1 Rex: Dissection of Rex to Identify the NMD Inhibitory Domain.

The human retrovirus human T-cell leukemia virus type I (HTLV-1) infects human T cells by vertical transmission from mother to child through breast milk or horizontal transmission through blood transfusion or sexual contact. Approximately 5% of infected individuals develop adult T-cell leukemia/lymphoma (ATL) with a poor prognosis, while 95% of infected individuals remain asymptomatic for the rest of their lives, during which time the infected cells maintain a stable immortalized latent state in the body. It is not known why such a long latent state is maintained. We hypothesize that the role of functional proteins of HTLV-1 during early infection influences the phenotype of infected cells in latency. In eukaryotic cells, a mRNA quality control mechanism called nonsense-mediated mRNA decay (NMD) functions not only to eliminate abnormal mRNAs with nonsense codons but also to target virus-derived RNAs. We have reported that HTLV-1 genomic RNA is a potential target of NMD, and that Rex suppresses NMD and stabilizes viral RNA against it. In this study, we aimed to elucidate the molecular mechanism of NMD suppression by Rex using various Rex mutant proteins. We found that region X (aa20-57) of Rex, the function of which has not been clarified, is required for NMD repression. We showed that Rex binds to Upf1, which is the host key regulator to detect abnormal mRNA and initiate NMD, through this region. Rex also interacts with SMG5 and SMG7, which play essential roles for the completion of the NMD pathway. Moreover, Rex selectively binds to Upf3B, which is involved in the normal NMD complex, and replaces it with a less active form, Upf3A, to reduce NMD activity. These results revealed that Rex invades the NMD cascade from its initiation to completion and suppresses host NMD activity to protect the viral genomic mRNA.

M-Sec induced by HTLV-1 mediates an efficient viral transmission.

Human T-cell leukemia virus type 1 (HTLV-1) infects target cells primarily through cell-to-cell routes. Here, we provide evidence that cellular protein M-Sec plays a critical role in this process. When purified and briefly cultured, CD4+ T cells of HTLV-1 carriers, but not of HTLV-1- individuals, expressed M-Sec. The viral protein Tax was revealed to mediate M-Sec induction. Knockdown or pharmacological inhibition of M-Sec reduced viral infection in multiple co-culture conditions. Furthermore, M-Sec knockdown reduced the number of proviral copies in the tissues of a mouse model of HTLV-1 infection. Phenotypically, M-Sec knockdown or inhibition reduced not only plasma membrane protrusions and migratory activity of cells, but also large clusters of Gag, a viral structural protein required for the formation of viral particles. Taken together, these results suggest that M-Sec induced by Tax mediates an efficient cell-to-cell viral infection, which is likely due to enhanced membrane protrusions, cell migration, and the clustering of Gag.

Promoter CpG methylation inhibits Krüppel-like factor 2 (KLF2)-Mediated repression of hTERT gene expression in human T-cells.

Constitutive expression of human telomerase reverse transcriptase (hTERT) with DNA methylation of its promoter is a common phenomenon in tumor cells. We recently found that the transcriptional factor Krüppel-like factor 2 (KLF2) binds to the CpG sequences in the hTERT promoter and inhibits hTERT gene expression in normal resting T-cells. The human T-cell line Kit 225 in the resting phase induced by the deprivation of interleukin (IL)-2 showed no decrease in the expression of hTERT, despite the high expression of KLF2. To elucidate the mechanisms of deregulation of hTERT expression in T-cells, we examined the relationship between DNA methylation and KLF2 binding to the hTERT promoter. The hTERT promoter was methylated in Kit 225 cells, resulting in the inhibition of the binding of KLF2 to the promoter. DNA demethylation by the reagent Zebularine recovered KLF2 binding to the hTERT promoter, followed by the downregulation of its gene expression. These findings indicate that the repressive effect of KLF2 on hTERT gene expression is abolished by DNA methylation in T-cell lines.

RLTPR Q575E: A novel recurrent gain-of-function mutation in patients with adult T-cell leukemia/lymphoma.

OBJECTIVES: Adult T-cell leukemia/lymphoma (ATL) is an intractable T-cell malignancy caused by long-term infection with human T-cell leukemia virus type-1 (HTLV-1). While ATL pathogenesis has been associated with HTLV-1-derived oncogenic proteins, including Tax and HBZ, the contribution of genomic aberrations remains poorly defined. METHODS: To elucidate the genomic basis of ATL, whole exome sequencing was performed on cells from 47 patients with aggressive ATL. RESULTS: We discovered the novel mutation RLTPR Q575E in four patients (8.5%) with a median variant allele frequency of 0.52 (range 0.11-0.68). Despite being reported in cutaneous T-cell lymphoma, three ATL patients carrying RLTPR Q575E lacked skin involvement. Patients carrying RLTPR Q575E also harbored CARD11 (75%), PLCG1 (25%), PRKCB (25%), or IKBKB (25%) mutations related to TCR/NF-κB signaling. Jurkat cells transfected with RLTPR Q575E cDNA displayed increased NF-κB activity and significantly increased IL-2 mRNA levels under stimulation. RLTPR Q575E increased the interaction between RLTPR and CARD11, while RLTPR directly interacted with Tax. CONCLUSIONS: We identified, and functionally validated, a novel gain-of-function mutation in patients with aggressive ATL. During TCR activation by Tax or gain-of-function mutations, RLTPR Q575E selectively upregulates NF-κB signaling and may exert oncogenic effects on ATL pathogenesis.

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, Tax301-309-specific activity against HTLV-1, we aimed to develop a Tax-redirected T cell immunotherapy for ATL. TCR-ɑ/ß 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.

Proteomic profiling of HTLV-1 carriers and ATL patients reveals sTNFR2 as a novel diagnostic biomarker for acute ATL.

Adult T-cell leukemia/lymphoma (ATL) is a human T-cell leukemia virus type 1 (HTLV-1)-associated T-cell malignancy with generally poor prognosis. Although only ∼5% of HTLV-1 carriers progress to ATL, early diagnosis is challenging because of the lack of ATL biomarkers. In this study, we analyzed blood plasma profiles of asymptomatic HTLV-1 carriers (ACs); untreated ATL patients, including acute, lymphoma, smoldering, and chronic types; and ATL patients in remission. Through SOMAscan, expression levels of 1305 plasma proteins were analyzed in 85 samples (AC, n = 40; ATL, n = 40; remission, n = 5). Using gene set enrichment analysis and gene ontology, overrepresented pathways in ATL vs AC included angiogenesis, inflammation by cytokines and chemokines, interleukin-6 (IL-6)/JAK/STAT3, and notch signaling. In selecting candidate biomarkers, we focused on soluble tumor necrosis factor 2 (sTNFR2) because of its active role in enriched pathways, extreme significance (Welch's t test P < .00001), high discrimination capacity (area under the curve >0.90), and novelty in ATL research. Quantification of sTNFR2 in 102 plasma samples (AC, n = 30; ATL, n = 68; remission, n = 4) using enzyme-linked immunosorbent assay showed remarkable elevations in acute ATL, at least 10 times those of AC samples, and return of sTNFR2 to AC state levels after achieving remission. Flow cytometry and immunostaining validated the expression of TNFR2 in ATL cells. No correlation between sIL-2 and sTNFR2 levels in acute ATL was found, suggesting the possibility of sTNFR2 as an independent biomarker. Our findings represent the first extensive blood-based proteomic analysis of ATL, suggesting the potential clinical utility of sTNFR2 in diagnosing acute ATL.

Conservation of a Neutralization Epitope of Human T-cell Leukemia Virus Type 1 (HTLV-1) among Currently Endemic Clinical Isolates in Okinawa, Japan.

Approximately one-tenth of the 10 million individuals living with human T-cell leukemia virus type-1 (HTLV-1) worldwide live in Japan. Most of these infected individuals live in the southwest region of Japan, including Okinawa prefecture; however, currently no prophylactic vaccine against HTLV-1 infection is available. For preventing the HTLV-1 spread, we previously generated a humanized monoclonal antibody (hu-LAT-27) that mediates both neutralization and antibody-dependent cellular cytotoxicity (ADCC). The neutralization epitope of LAT-27 is a linear amino acid sequence from residue 191 to 196 (Leu-Pro-His-Ser-Asn-Leu) of the HTLV-1 envelope gp46 protein. Here, we found that the LAT-27 epitope is well conserved among HTLV-1 clinical isolates prevalent in Okinawa. The hu-LAT-27 treatment inhibited syncytium formation by these clinical HTLV-1 isolates. Although an amino acid substitution at residue 192 in the LAT-27 epitope from proline to serine was found in a few HTLV-1 isolates, hu-LAT-27 could still react with a synthetic peptide carrying this amino acid substitution. These findings demonstrate the wide spectrum of hu-LAT-27 reactivity, suggesting that hu-LAT-27 may be a candidate drug for prophylactic passive immunization against HTLV-1 infection.

EOS, an Ikaros family zinc finger transcription factor, interacts with the HTLV-1 oncoprotein Tax and is downregulated in peripheral blood mononuclear cells of HTLV-1-infected individuals, irrespective of clinical statuses.

BACKGROUND: EOS plays an important role in maintaining the suppressive function of regulatory T cells (Tregs), and induces a regulated transformation of Tregs into T helper-like cells, which are capable of secreting proinflammatory cytokines in response to specific inflammatory signals. Meanwhile, significant reduction in Treg activity along with production of proinflammatory cytokines has been reported in patients with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). METHODS: In this study, to examine whether there is an alteration in EOS expression in peripheral blood mononuclear cells (PBMCs) derived from HTLV-1-infected individuals especially HAM/TSP, we investigated the expression of HTLV-1 tax genotype, proviral load (PVL), and the mRNA expression of tax, HBZ and EOS in HTLV-1 infected individuals including adult T-cell leukemia/lymphoma (ATL), HAM/TSP, or asymptomatic carriers. The expression levels of EOS mRNA and protein in various HTLV-1-infected or uninfected human T-cell lines were also investigated. RESULTS: EOS was highly expressed at the protein level in most HTLV-1 infected T-cell lines, and was augmented after the HTLV-1 regulatory factor Tax was induced in a Tax-inducible JPX-9 cell line. Immunoprecipitation experiments demonstrated a physical interaction between EOS and the viral regulatory protein Tax, but not HBZ. Meanwhile, there was a significant decrease in EOS mRNA levels in PBMCs of HTLV-1 infected individuals irrespective of their clinical statuses. We found an inverse correlation between EOS mRNA levels and HTLV-1 PVL in ATL patients, and positive correlations between both EOS mRNA load and PVL, and EOS and HBZ mRNA load in HAM/TSP patients, whereas this correlation was not observed in other clinical statuses. CONCLUSIONS: These findings suggest that both Tax and HBZ can alter the expression of EOS through undetermined mechanisms, and dysregulated expression of EOS in PBMCs of HTLV-1 infected individuals may contribute to the pathological progression of HTLV-1-associated diseases, such as ATL and HAM/TSP.