Role of Interleukin-17 cytokine family in human T-cell lymphotropic virus type 1 (HTLV-1) infection and associated diseases

•HTLV is an oncogenic virus causes two main associated diseases, ATLL and HAM/TSP.•As a part of the immune system, IL-7 plays a significant role in HTLV-1 infection and the development of associated diseases.•IL-17A is directly connected to developing HTLV-derived inflammatory diseases and is an independent determinant of patients’ clinical status.•IL-17 is negatively correlated with the development of ATLL and boosting the IL-17 signaling pathway might improve the prognosis of ATLL patients. Human T-lymphotropic virus (HTLV-1) is a neglected virus with worldwide distribution of over 10 million people and is the cause of two main associated diseases Adult T cell Leukemia-Lymphoma (ATLL), and HTLV-1-associated Myelopathy/Tropical Spastic paraparesis (HAM/TSP). The IL-17 cytokine family plays a crucial role in the host immunity against HTLV-1 and the development of associated disease. A systematic review was conducted to analyze all research reporting on the levels or expression of the IL-17 HTLV-1 infection and associated diseases. The literature search was conducted in electronic databases including PubMed/Medline and Web of Sciences until January 31st, 2024, followed by the PRISMA guidelines. Our search revealed 20 eligible articles to be included in our study. The total number of cases studied was 1420, of which 386 were carriers without any symptoms, and were 176 ATLL and 237 HAM/TSP. The IL-17 cytokine family production or mRNA expression was higher in HAM/TSP patients but showed a trend toward reduction in the case of ATLL. Our results showed that while The IL-17 cytokine family plays a significant role in the immunopathogenesis of disease and clinical status of patients with inflammatory disorders such as HAM/TSP, IL-17 production is diminished and the RORC/IL-17 signaling pathway is downregulated during ATLL. Our data suggest that boosting the RORC/IL-17 signaling pathway in ATLL and using anti-IL-17 agents in HAM/TSP and other HTLV-related inflammatory conditions might benefit patients and improve their outcomes.