Triple Therapy with Prednisolone, Pegylated Interferon and Sodium Valproate Improves Clinical Outcome and Reduces Human T-Cell Leukemia Virus Type 1 (HTLV-1) Proviral Load, Tax and HBZ mRNA Expression in Patients with HTLV-1-Associated Myelopathy/Tropical Spastic Paraparesis

HTLV-1-associated myelopathy in Spain

BACKGROUND

HTLV-1 infection is a neglected disease. Over 10 million people are infected worldwide, with hot spots of high endemicity across all continents. Roughly 5% of HTLV-1 carriers develop HTLV-1-associated myelopathy (HAM), a progressive subacute neurological disabling disease.

METHODS

We report the main features of patients diagnosed with HAM up to date in Spain, a non-endemic country with a relatively high migrant flow from Latin America and Equatorial Africa, where HTLV-1 is endemic.

RESULTS

A total of 451 cases of HTLV-1 had been recorded in Spain until the end of year 2022. HAM had been diagnosed in 58 (12.9%). The current incidence is of 2-3 new cases per year. Women represent 76%. Mean age at diagnosis is 49 years-old. Nearly 60% are Latin Americans. Although sexual transmission is the most likely route of HTLV-1 acquisition, up to 6 individuals had been infected following solid organ transplantation. Rapid onset myelopathy developed in all but one of these transplant recipients from three HTLV-1-positive donors. HTLV-1 subtype 1a transcontinental was the only variant recognized in HAM patients. HTLV-1 proviral load was significantly greater in HAM patients than in asymptomatic HTLV-1 carriers (677 vs 104 HTLV-1 DNA copies/104 PBMC; p = 0.012). Symptom relief medications and physiotherapy have been the only treatment providing some benefit to HAM patients. Neither significant clinical nor virological efficacy was noticed using antiretrovirals in at least 9 HAM patients. Two thirds of HAM patients ended up in a wheelchair and with urinary/fecal sphincter incontinence.

CONCLUSION

HAM is the most frequent clinical manifestation of HTLV-1 infection in Spain, a non-endemic country. Middle aged women migrants from Latin America are the most frequently affected. Two thirds end up in a wheelchair despite using antiretroviral therapy.

HTLV-1 Proviral Load Absolute RT-qPCR Development for Assessing on Clinical Outcomes in HAM/TSP Patients

Background

The significance of HTLV-1 proviral load as a prognostic biomarker in HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) has been a subject of controversy. This study aims to assess the impact of HTLV-1 proviral load (PVL) on the clinical outcome in patients with HAM/TSP.

Methods

An absolute quantitative HTLV-1 PVL RT-qPCR, TaqMan method was developed with 100% sensitivity and specificity. Then, from 2005-2018, the HTLV-1 PVL of 90 eligible newly diagnosed HAM/TSP patients were assessed for demographic, clinical symptoms and their associations with HTLV-1-PVL.

Results

The quality control of the designed RT-qPCR showed a sensitivity and specificity of 100%. Spasticity in lower limbs in 58.9% and urinary symptoms in 17.8% of HAM/TSPs were observed. Using this designed RT-qPCR, the HTLV-1-PVL strongly affected spasticity and sphincter disturbance (p=0.05). The multivariate logistic test showed that only the beginning of lower limb weakness along with tremor was associated with PVL (OR: 2.78. 95% CI (0.99-1.02) and p=0.05). Urinary incontinence was prevalent among these patients; however, no association was identified with the HTLV-1 proviral load (PVL).

Conclusions

The absolute RT-qPCR developed for measuring HTLV-1 proviral load (PVL) demonstrated reliable results. Despite a high prevalence of urinary incontinence in these patients, no association was observed with the PVL. Consequently, it appears that HTLV-1 proviral load is specifically associated with developing spasticity in HAM/TSP.

Advances in the treatment of human T-cell lymphotropic virus type-I associated myelopathy

INTRODUCTION

Nearly 2-3% of those 10 to 20 million individuals infected with the Human T-cell lymphotropic virus type-1 (HTLV-1); are predisposed to developing HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). It is a neuro-inflammatory disease; differentiated from multiple sclerosis based on the presence of typical neurologic symptoms, confirmation of HTLV-1 infection, and other molecular biomarkers.

AREAS COVERED

A brief review of the epidemiology, host immune responses, and molecular pathogenesis of HAM/TSP is followed by detailed discussions about the host-related risk factors for developing HAM/TSP and success/failure stories of the attempted management strategies.

EXPERT OPINION

Currently, there is no effective treatment for HAM/TSP. Anti-retroviral therapy, peculiar cytokines (IFN-α), some anti-oxidants, and allograft bone marrow transplantation have been used for treating these patients with limited success. Under current conditions, asymptomatic carriers should be examined periodically by a neurologist for early signs of spinal cord injury. Then it is crucial to determine the progress rate to adapt the best management plan for each patient. Corticosteroid therapy is most beneficial in those with acute myelitis. However, slow-progressing patients are best managed using a combination of symptomatic and physical therapy. Additionally, preventive measures should be taken to decrease further spread of HTLV-1 infection.

Molecular insight into the study of adult T-cell leukemia/lymphoma (ATLL): Ten-year studies on HTLV-1 associated diseases in an endemic region

The outcome of successful infection, including human T-cell leukemia virus type 1 (HTLV-1), is determined by the interactions between the host and the infectious agent. Ten years of work on HTLV-1-associated diseases in an endemic region of Iran have been critically compared in the present study. The outstanding findings of RNA-seq, system biology analysis, and gene expression measurements on adult T-cell leukemia/lymphoma (ATLL) and enzootic bovine leukosis(EBL) in our lab encouraged us to investigate the significant role of oncogenes in the ATLL malignancy. Most studies assessed such interactions by the proviral load (PVL), Tax, and HBZ regulatory proteins in HTLV-1 and the host's immunological and cell cycle factors. The current study is a comprehensive comparing view of our previously published and unpublished results investigating the HTLV-1-host interactions leading to the transformation of the infected cell. The main focus has been on the essential proteins implicated in the virus dissemination, cell survival, and proliferation of infected cells toward leukemia development and progression. Similar to its homolog BLV-AS-1-2 in EBL, the HTLV-1-HBZ is a pivotal factor in the maintenance and progression of the ATLL. In addition, the inappropriate activities of the PI3K/Akt pathway, BRCAs, and RAD51 in the DNA repair system, which are orchestrating many other immortalization pathways, might be the central factors in the manifestation of ATLL. HTLV-1-HBZ and the host PI3K/Akt pathway, BCAs, and RAD51 could be suggested as influential targets for the prognosis and proper therapy of ATLL.

Coevolution of HTLV-1-HBZ, Tax, and proviral load with host IRF-1 and CCNA-2 in HAM/TSP patients

Background HTLV-1-associated myelopathy (HAM/TSP) is a progressive neurodegenerative inflammatory condition of HTLV-1 infection. Viral-host interactions are a significant contributor to the symptoms of HTLV-1-associated diseases. Therefore, in this study, the expression of the main regulatory viral factors and proviral load (PVL) and two host transcription molecules were evaluated in HAM/TSP patients. Materials and methods The study population included 17 HAM/TSP patients, 20 asymptomatic carriers (ACs), and 19 healthy controls (HCs). RNA and DNA were extracted from PBMCs for assessment of the gene expressions and PVL assessment using RT-qPCR and TaqMan method. Results HTLV-1-PVL was higher in HAM/TSPs (395.80 ± 99.69) than ACs (92.92 ± 29.41) (P = 0.001). The Tax expression in HAM/TSPs (7.8 ± 5.7) was strongly higher than ACs (0.06 ± 0.04) (P = 0.02), while HTLV-1-HBZ was only increased around three times in HAM/TSPs (3.17), compared to ACs (1.20) and not significant. The host IRF1 expression in HAM/TSPs (0.4 ± 0.31) was higher than ACs (0.09 ± 0.05) (P = 0.02) and also HCs (0.16 ± 0.07) (P = 0.5), but lower in ACs than HCs (p = 0.01). Although, in HAM/TSPs (0.13 ± 0.09) and ACs (0.03 ± 0.02) CCNA-2 expression was statistically fewer than HCs (0.18 ± 0.06) (P = 0.03, P = 0.001, respectively), in HAM/TSP was higher than ACs (P = 0.1), but did not meet a 95% confidence interval. Conclusion The study showed that HTLV-1-PVL and Tax, along with host IRF-1, could be considered biomarkers in HAM/TSP development. Furthermore, IRF-1, as an essential transcription factor, can be considered a pivotal target in HAM/TSPs treatment.

TAX and HBZ: hFc Ɣ 1 proteins as targets for passive immunotherapy

Objective(s):

Human T leukemia virus type one (HTLV-1) causes two life-threatening diseases in around five percent of infected subjects, a T cell malignancy and a neurodegenerative disease. TAX and HBZ are the main virulence agents implicated in the manifestation of HTLV-1–associated diseases. Therefore, this study aims to produce these HTLV-1 factors as recombinant Fc fusion proteins to study the structures, their immunogenic properties as vaccines, and their capability to produce specific neutralization antibodies.

Materials and Methods:

TAX and HBZ sequences were chosen from the NCBI-nucleotide database, then designed as human Fc chimers and cloned into Pichia pastoris. Produced proteins were purified by HiTrap affinity chromatography and subcutaneously injected into rabbits. Rabbit Abs were purified by batch chromatography, and their neutralization activities for the HTLV-1-infected MT-2 cell line were assessed. Furthermore, the protective abilities of recombinant proteins were evaluated in Tax or HBZ immunized rabbits by MT-2 cell line inoculation and measurement of HTLV-1-proviral load.

Results:

Specific Abs against Tax and HBZ can eliminate 2 million MT-2 cells in 1/1000 dilution in vitro. In challenging assays, the immunization of the animals using Tax or HBZ had no protective activity as HTLV-1 PVL was still positive.

Conclusion:

The result suggests that recombinant TAX and HBZ: hFcγ1 proteins can produce a proper humoral immune response. Therefore, they could be considered a passive immunotherapy source for HTLV-1-associated diseases, while total TAX and HBZ proteins are unsuitable as HTLV-1 vaccine candidates.

HTLV-1 oncovirus-host interactions: From entry to the manifestation of associated diseases

Human T lymphotropic virus type-1 (HTLV-1) is a well-known human oncovirus, associated with two life-threatening diseases, adult T cell leukaemia/lymphoma (ATL) and HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP). The study of this oncogenic virus is significant from two different aspects. First, HTLV-1 can be considered as a neglected public health problem, which may spread slowly worldwide. Second, the incidence of HTLV-1 associated diseases due to oncogenic effects and deterioration of the immune system towards autoimmune diseases are not fully understood. Furthermore, knowledge about viral routes of transmission is important for considering potential interventions, treatments or vaccines in endemic regions. In this review, novel characteristics of HTLV-1, such as the unusual infectivity of virions through the virological synapse, are discussed in the context of the HTLV-1 associated diseases (ATL and HAM/TSP).

HTLV-I and Strongyloides in Australia: The worm lurking beneath

Strongyloidiasis and HTLV-I (human T-lymphotropic virus-1) are important infections that are endemic in many countries around the world with an estimated 370 million infected with Strongyloides stercoralis alone, and 5-10 million with HTVL-I. Co-infections with these pathogens are associated with significant morbidity and can be fatal. HTLV-I infects T-cells thus causing dysregulation of the immune system which has been linked to dissemination and hyperinfection of S. stercoralis leading to bacterial sepsis which can result in death. Both of these pathogens are endemic in Australia primarily in remote communities in Queensland, the Northern Territory, and Western Australia. Other cases in Australia have occurred in immigrants and refugees, returned travellers, and Australian Defence Force personnel. HTLV-I infection is lifelong with no known cure. Strongyloidiasis is a long-term chronic disease that can remain latent for decades, as shown by infections diagnosed in prisoners of war from World War II and the Vietnam War testing positive decades after they returned from these conflicts. This review aims to shed light on concomitant infections of HTLV-I with S. stercoralis primarily in Australia but in the global context as well.

High proviral load of human T cell lymphotropic virus type-1 facilitates coronary artery diseases

Objective(s):

Coronary artery disease (CAD) is known as a life threatening disease, worldwide. In this study the role of HTLV-1 infection was evaluated on cardiac involvement in an endemic region of northeastern Iran.

Materials and Methods:

Serologic and molecular tests for HTLV-1 infection were carried out in subjects who had coronary angiography. A real-time PCR, TaqMan method, to quantify HTLV-1 proviral load (PVL), and routine hematological and biochemical tests were performed for study subjects.

Results:

Twenty nine patients were HTLV-1+CAD+ and 13 cases were HTLV-1+CAD-. Although, there were no significant differences for risk factors like FBS, HDL, triglyceride, systolic and diastolic blood pressure (Cbp, Dbp), waist circumference (WC), hip circumference (WL), cholesterol (P=0.003), and LDL (P=0.007) levels, and monocyte count (P=0.05) had meaningful differences. The mean HTLV-1 PVL in HTLV-1+CAD+ subjects was 992.62±120 which was higher compared with HTLV-1+CAD- group (406.54±302 copies/104 PBMCs). Moreover, HTLV-1 PVL in males (833±108) was lower compared with females (1218±141 copies/104 PBMCs) (P=0.05). Patients with HTLV-1-PVL of more than 500 copies/104 had more diffused atherosclerosis plaque than patients with less than 500 (OR=6.87, 95% CI=1.34-35.05; P=0.016). Furthermore, patients with diffused coronary atherosclerosis had significantly higher levels of HTLV-1 PVL than patients with middle, proximal, and normal location of coronary sclerotic lesions (P<0.05).

Conclusion:

Taken together, in endemic area, HTLV-1 infection, more likely is a facilitating factor for heart complications and the high HTLV-1 PVL might affect CAD manifestations.

Acupuncture in the treatment of HTLV-I-associated myelopathy / tropical spastic Paraparesis

We investigate the possible effects of acupuncture on the improvement of neurological problems in HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP)disease. Twenty patients with HAM/TSP were studied in this pre and post-test clinical trial. Urinary incontinence, global motor disability, spasticity, and pain severity were evaluated before, one month, and three-month after the intervention. Analyses demonstrated a significant reduction of urinary symptoms one month after acupuncture (P = 0.023). A significant improvement was observed in patients' pain and the spasticity at the upper extremity joints, one and three-month after the intervention (P < 0.05). This study suggests that body acupuncture can be used as a complementary treatment to improve HAM/TSP neurological symptoms.

An insight to HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) pathogenesis; evidence from high-throughput data integration and meta-analysis

BACKGROUND

Human T-lymphotropic virus 1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a progressive disease of the central nervous system that significantly affected spinal cord, nevertheless, the pathogenesis pathway and reliable biomarkers have not been well determined. This study aimed to employ high throughput meta-analysis to find major genes that are possibly involved in the pathogenesis of HAM/TSP.

RESULTS

High-throughput statistical analyses identified 832, 49, and 22 differentially expressed genes for normal vs. ACs, normal vs. HAM/TSP, and ACs vs. HAM/TSP groups, respectively. The protein-protein interactions between DEGs were identified in STRING and further network analyses highlighted 24 and 6 hub genes for normal vs. HAM/TSP and ACs vs. HAM/TSP groups, respectively. Moreover, four biologically meaningful modules including 251 genes were identified for normal vs. ACs. Biological network analyses indicated the involvement of hub genes in many vital pathways like JAK-STAT signaling pathway, interferon, Interleukins, and immune pathways in the normal vs. HAM/TSP group and Metabolism of RNA, Viral mRNA Translation, Human T cell leukemia virus 1 infection, and Cell cycle in the normal vs. ACs group. Moreover, three major genes including STAT1, TAP1, and PSMB8 were identified by network analysis. Real-time PCR revealed the meaningful down-regulation of STAT1 in HAM/TSP samples than AC and normal samples (P = 0.01 and P = 0.02, respectively), up-regulation of PSMB8 in HAM/TSP samples than AC and normal samples (P = 0.04 and P = 0.01, respectively), and down-regulation of TAP1 in HAM/TSP samples than those in AC and normal samples (P = 0.008 and P = 0.02, respectively). No significant difference was found among three groups in terms of the percentage of T helper and cytotoxic T lymphocytes (P = 0.55 and P = 0.12).

CONCLUSIONS

High-throughput data integration disclosed novel hub genes involved in important pathways in virus infection and immune systems. The comprehensive studies are needed to improve our knowledge about the pathogenesis pathways and also biomarkers of complex diseases.

HTLV-1-host interactions on the development of adult T cell leukemia/lymphoma: virus and host gene expressions

Background

Adult T-cell leukemia/lymphoma (ATLL) is a lymphoproliferative disorder of HTLV-1-host interactions in infected TCD4+ cells. In this study, the HTLV-1 proviral load (PVL) and HBZ as viral elements and AKT1, BAD, FOXP3, RORγt and IFNλ3 as the host factors were investigated.

Methods

The study was conducted in ATLLs, HTLV-1-associated myelopathy/tropical spastic paraparesis patients (HAM/TSPs) and HTLV-1-asympthomatic carriers (ACs). The DNA and mRNA from peripheral blood mononuclear cells were extracted for gene expression assessments via qRT-PCR, TaqMan assay, and then confirmed by western blotting.

Results

As it was expected, the HTLV-1-PVL were higher in ATLLs than ACs (P = 0.002) and HAM/TSP (P = 0.041). The HBZ expression in ATLL (101.76 ± 61.3) was radically higher than in ACs (0.12 ± 0.05) and HAM/TSP (0.01 ± 0.1) (P = 0.001). Furthermore, the AKT1 expression in ATLLs (13.52 ± 4.78) was higher than ACs (1.17 ± 0.27) (P = 0.05) and HAM/TSPs (0.72 ± 0.49) (P = 0.008). However, BAD expression in ATLL was slightly higher than ACs and HAM/TSPs and not significant. The FOXP3 in ATLLs (41.02 ± 24.2) was more than ACs (1.44 ± 1) (P = 0.007) and HAM/TSP (0.45 ± 0.15) (P = 0.01). However, RORγt in ATLLs (27.43 ± 14.8) was higher than ACs (1.05 ± 0.32) (P = 0.02) but not HAM/TSPs. Finally, the IFNλ3 expression between ATLLs (31.92 ± 26.02) and ACs (1.46 ± 0.63) (P = 0.01) and ACs and HAM/TSPs (680.62 ± 674.6) (P = 0.02) were statistically different, but not between ATLLs and HAM/TSPs.

Conclusions

The present and our previous study demonstrated that HTLV-1-PVL and HBZ and host AKT1 and Rad 51 are novel candidates for molecular targeting therapy of ATLL. However, high level of RORγt may inhibit Th1 response and complicated in ATLL progressions.

HTLV-1 infection-induced motor dysfunction, memory impairment, depression, and brain tissues oxidative damage in female BALB/c mice

AIMS

The HTLV-1 infection is associated with a neuro-inflammatory disease. In the present study, the behavioral consequences and brain oxidative damages were evaluated in HTLV-1-infected BALB/c mice.

MATERIAL AND METHODS

20 female BALB/c mice were divided into two groups comprising control and HTLV-1-infected. The HTLV-1-infected group was inoculated with a 10⁶ MT-2 HTLV-1-infected cell line. Two months later, the behavioral tests were conducted. Finally, oxidative stress was assessed in the cortex and hippocampus tissues.

KEY FINDINGS

In the HTLV-1-infected group, running time and latency to fall, travel distance and time spent in the peripheral zone, total crossing number and total traveled distance in open field test, the latency of entrance into the dark compartment in the passive avoidance test, the new object exploration percentage, and discrimination ratio were significantly lower than in the control group. The immobility time, time spent in the dark compartment in passive avoidance test, and total exploration time significantly increased in the HTLV-1-infected group compared to the control group. In the cortical tissue of the HTLV-1 group, the malondialdehyde levels were elevated while the total thiol levels decreased in comparison to the control group. The activity of superoxide dismutase in the cortical and hippocampal tissues, and catalase activity in cortical tissue significantly decreased in the HTLV-1 group in comparison to the control group.

SIGNIFICANCE

The HTLV-1 infection seems to induce depression-like behavior, motor dysfunction, disruption in working and fear memory and also oxidative stress in the cortex and hippocampus.

HTLV-1, the Other Pathogenic Yet Neglected Human Retrovirus: From Transmission to Therapeutic Treatment

Going back to their discovery in the early 1980s, both the Human T-cell Leukemia virus type-1 (HTLV-1) and the Human Immunodeficiency Virus type-1 (HIV-1) greatly fascinated the virology scene, not only because they were the first human retroviruses discovered, but also because they were associated with fatal diseases in the human population. In almost four decades of scientific research, both viruses have had different fates, HTLV-1 being often upstaged by HIV-1. However, although being very close in terms of genome organization, cellular tropism, and viral replication, HIV-1 and HTLV-1 are not completely commutable in terms of treatment, especially because of the opposite fate of the cells they infect: death versus immortalization, respectively. Nowadays, the antiretroviral therapies developed to treat HIV-1 infected individuals and to limit HIV-1 spread among the human population have a poor or no effect on HTLV-1 infected individuals, and thus, do not prevent the development of HTLV-1-associated diseases, which still lack highly efficient treatments. The present review mainly focuses on the course of HTLV-1 infection, from the initial infection of the host to diseases development and associated treatments, but also investigates HIV-1/HTLV-1 co-infection events and their impact on diseases development.

Altered Expression of Cell Cycle Regulators in Adult T-Cell Leukemia/ Lymphoma Patients

BACKGROUND

Adult T-cell leukemia/lymphoma (ATLL) is caused by human T-cell lymphotropic virus type-1 (HTLV-1). HTLV-1 oncogenes can induce malignancy through controlled gene expression of cell cycle checkpoints in the host cell. HTLV-I genes play a pivotal role in overriding cell cycle checkpoints and deregulate cellular division. In this study, we aimed to determine and compare the HTLV-1 proviral load and the gene expression levels of cyclin-dependent kinase-2 (CDK2), CDK4, p53, and retinoblastoma (Rb) in ATLL and carrier groups.

METHODS

A total of twenty-five ATLL patients (12 females and 13 males) and 21 asymptomatic carriers (10 females and 11 males) were included in this study. TaqMan real-time polymerase chain reaction assay was used for evaluation of proviral load and gene expression levels of CDK2, CDK4, p53, and Rb. Statistical analysis was used to compare proviral load and gene expression levels between two groups, using SPSS version 18.

RESULTS

The mean scores of the HTLV-1 proviral load in the ATLL patients and healthy carriers were 13067.20±6400.41 and 345.79±78.80 copies/10⁴ cells, respectively (P=0.000). There was a significant correlation between the gene expression levels of CDK2 and CDK4 (P=0.01) in the ATLL group.

CONCLUSION

Our findings demonstrated a significant difference between the ATLL patients and healthy carriers regarding the rate of proviral load and the gene expression levels of p53 and CDK4; accordingly, proviral load and expression levels of these genes may be useful in the assessment of disease progression and prediction of HTLV-1 infection outcomes.

Evaluation of HTLV-1 HBZ and proviral load, together with host IFN λ3, in pathogenesis of HAM/TSP

Human T-cell lymphotropic virus 1 (HTLV-1) is associated with two progressive diseases: HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and adult T-cell leukemia/lymphoma (ATLL). Although HTLV-1 proviral load (PVL) has been introduced as a risk factor for these diseases' progression, it is not sufficient on its own to yield an accurate estimation of the outcome of the infection. In the present study, PVL and HTLV-1 basic leucine zipper factor (HBZ) expression level as viral factors, and IFN λ3 as a host factor, were evaluated in HAM/TSP patients and HTLV-1 asymptomatic carriers (ACs). During 2014-2015, 12 HAM/TSP patients and 18 ACs who had been referred to the HTLV-1 Clinic, Ghaem Hospital, Mashhad University of Medical Sciences (MUMS), Mashhad, Iran, were enrolled in this study. Peripheral blood mononuclear cells (PBMCs) were isolated and the DNA and mRNA were extracted for quantification of HBZ, IFN λ3 expression, and PVL using real-time PCR (TaqMan method). Although the PVL was higher in the HAM/TSP group, with a 94% confidence interval, there were no considerable differences in terms of HBZ mRNA and PVL between ACs and HAM patients. IFN λ3 expression in the HAM/TSP group was significantly higher than in the ACs (P = 0.02). To the best of our knowledge, no study has evaluated the expression level of IFN λ3 in HTLV-1 positive patients. The immune response against HTLV-1 viral antigens and virulent factors will therefore further refine our knowledge of interactions between the virus and host in the pathogenesis of HTLV-1-related disorders. The virus PVL and the host IFN λ3 can be used as pathogenic factors of HTLV-1 infected patients at risk of HAM/TSP manifestation. J. Med. Virol. 89:1102-1107, 2017. © 2016 Wiley Periodicals, Inc.

Role of IL-21 in HTLV-1 infections with emphasis on HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP)

Interleukin-21 (IL-21) enhances the survival and cytotoxic properties of cytotoxic T cells (CTLs) and exhibits essential roles in controlling chronic viral infections. HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic progressive inflammatory disease of the nervous system. The main determinant of disease progression is efficiency of the CTL response to Human T lymphotropic virus types I (HTLV-1). In this study, the expression of host IL-21 and HTLV-I Tax and proviral load (PVL) was evaluated to understand the role and mechanism of IL-21 in HTLV-1 infections and the subsequent development of HAM/TSP. A cross-sectional study was carried out on 20 HAM/TSP patients, 20 asymptomatic HTLV-1 carriers (ACs) and 20 healthy controls (HCs) to evaluate the expression of IL-21 and Tax and PVL in non-activated and phorbol myristate acetate (PMA)-ionomycin-activated peripheral blood mononuclear cells (PBMCs). The mean mRNA expression of IL-21 in the non-activated and activated PBMCs was higher (by 5-13 times) in the HAM/TSP patients than in ACs and HCs (p < 0.05); however, there was no significant difference between ACs and HCs. In contrast to the IL-21 mRNA expression, the serum level of the IL-21 protein was significantly lower in the HAM/TSP patients than in ACs and HCs (p < 0.05). Furthermore, higher expression of Tax and PVL was observed in the HAM/TSP subjects than ACs (p < 0.05). In addition, Tax gene expression was positively correlated with PVL (R = 0.595, p = 0.000) and IL-21 gene expression (R = 0.395, p = 0.021) in the HTLV-1-infected subjects. In conclusion, the increase in IL-21 mRNA expression may reflect the attempt of infected T cells to induce an appropriate antiviral response, and the decrease in IL-21 protein expression may reflect the inhibition of IL-21 mRNA translation by viral factors in favour of virus evasion and dissemination.