Pathogenesis of HTLV-1 infection and progression biomarkers: An overview

ABSTRACT Infection by human T-cell lymphotropic virus type 1 (HTLV-1) occurs in lymphocytes, which travel throughout the body, thus affecting several target organs and causing varied clinical outcomes, particularly in populations that are underserved and do not have access to healthcare. However, the mechanism of pathogenesis is not yet fully understood. The TAX and HTLV-1 basic leucine zipper factor (HBZ) proteins maintain viral persistence and affect pathogenesis through cell proliferation and immune and inflammatory responses that accompany each clinical manifestation. TAX expression leads to inhibition of transcription error control, OX40 overexpression, and cell proliferation in adult T-cell leukemia (ATL). OX40 levels are elevated in the central nervous system (CNS), and the expression of TAX in the CNS causes neuronal damage and loss of immune reactivity among patients with HTLV-1-associated myelopathy (HAM). HBZ reduces viral replication and suppresses the immune response. Its cell compartmentalization has been associated with the pathogenesis of HAM (cytoplasmic localization) and ATL (nuclear localization). TAX and HBZ seem to act antagonistically in immune responses, affecting the pathogenesis of HTLV-1 infection. The progression from HTLV-1 infection to disease is a consequence of HTLV-1 replication in CD4+ T and CD8+ T lymphocytes and the imbalance between proinflammatory and anti-inflammatory cytokines. The compartmentalization of HBZ suggests that this protein may be an additional tool for assessing immune and inflammatory responses, in addition to those already recognized as potential biomarkers associated with progression from infection to disease (including human leukocyte antigen (HLA), killer immunoglobulin-like receptors (KIR), interleukin (IL)-6, IL-10, IL-28, Fas, Fas ligand, interferon (IFN)-γ, tumor necrosis factor (TNF)-α, and mannose-binding lectin).

Co-expression of HBZ, TAX and FOXp3 and HTLV-1-associated myelopathy/tropical spastic paraparesis development in HTLV-1-infected individuals: A systematic review

Human T-cell lymphotropic virus type 1 (HTLV-1) is associated with the development of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). It has been reported that the HTLV-1 proteins (specifically TAX and HBZ) can modulate FOXp3, resulting in an immune imbalance that can favor the progression of HAM/TSP. This review aims to summarize the literature in order to clarify the relationship between the expression of HTLV-1 mRNAs and/or viral proteins (TAX and HBZ) with the expression of mRNA and/or protein FOXp3 and their correlation with HAM/TSP development. This systematic review was conducted according to the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analysis. The search strategy was performed on the Medical Literature Analysis and Retrieval System Online and Latin American and Caribbean Literature in Health Sciences Platform using subject descriptors. After screening, six articles were included in this review. The studies suggested that TAX and HBZ have a directly proportional correlation with FOXp3 in individuals with HAM/TSP, which also presented an increased expression of FOXp3 compared to asymptomatic controls and/or healthy donors. This systematic review indicates that TAX and HBZ can interact with FOXp3 and that interaction may influence HAM/TSP development.

Evaluation of the role of TAX, HBZ, and HTLV-1 proviral load on the survival of ATLL patients

BACKGROUND: Adult T-cell leukemia/lymphoma (ATLL) is an aggressive malignancy with very poor prognosis and short survival, caused by the human T-lymphotropic virus type-1 (HTLV-1). The HTLV-1 biomarkers trans-activator x (TAX) and HTLV-1 basic leucine zipper factor (HBZ) are main oncogenes and life-threatening elements. This study aimed to assess the role of the TAX and HBZ genes and HTLV-1 proviral load (PVL) in the survival of patients with ATLL. METHODS: Forty-three HTLV-1-infected individuals, including 18 asymptomatic carriers (AC) and 25 ATLL patients (ATLL), were evaluated between 2011 and 2015. The mRNA expression of TAX and HBZ and the HTLV-1 PVL were measured by quantitative PCR. RESULTS: Significant differences in the mean expression levels of TAX and HBZ were observed between the two study groups (ATLL and AC, P=0.014 and P=0.000, respectively). In addition, the ATLL group showed a significantly higher PVL than AC (P=0.000). There was a significant negative relationship between PVL and survival among all study groups (P=0.047). CONCLUSION: The HTLV-1 PVL and expression of TAX and HBZ were higher in the ATLL group than in the AC group. Moreover, a higher PVL was associated with shorter survival time among all ATLL subjects. Therefore, measurement of PVL, TAX, and HBZ may be beneficial for monitoring and predicting HTLV-1-infection outcomes, and PVL may be useful for prognosis assessment of ATLL patients. This research demonstrates the possible correlation between these virological markers and survival in ATLL patients.