The human T-cell lymphotropic virus type 1 (HTLV-1) is a highly oncogenic retrovirus recognized as the causative agent of adult T-cell leukemia/lymphoma (ATLL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Among the key risk factors for ATLL development are high proviral load, reduced anti-Tax immune responses, and elevated levels of soluble interleukin-2 receptor. Unlike classical oncogenic viruses, HTLV-1 does not encode proto-oncogenes but instead drives cellular transformation through a combination of mechanisms, including viral gene dysregulation, chromatin remodeling, epigenetic reprogramming, persistent clonal expansion, immune evasion, and RNA-based modifications. Despite growing understanding of these molecular pathways, an effective prophylactic vaccine against HTLV-1 remains unavailable. However, several vaccine strategies including viral vector platforms, mRNA-based candidates, peptide vaccines, and dendritic cell-based approaches have shown promise in preclinical models. In this review, we provide a comprehensive synthesis of current knowledge on HTLV-1 oncogenesis, highlight the roles of viral proteins such as Tax and HBZ in immune evasion, and critically examine the state of vaccine development efforts aimed at controlling this neglected human retrovirus.
Vásconez-González et al. (Fri,) studied this question.