Evaluation of the Association of Cytokines, Interleukin 6 Polymorphism, and Proviral Load With Myelopathy, Pain, and Functionality in HTLV1‐Infected Patients

The factors involved in the development of functional dependence, pain and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) could be linked to inflammatory cytokines and proviral load. This study aimed to assess the association between myelopathy, pain, and functionality with proviral load in blood, serum levels of cytokines and the interleukin 6 (IL-6) polymorphism in individuals living with HTLV-1. This was a cross-sectional study. Consecutive HTLV-1-infected patients, with or without HAM/TSP, attending the infectious diseases clinic were included. A semi-structured questionnaire, functional independence measure, and the numerical rating scale for pain intensity were applied and peripheral blood samples were collected. Plasma cytokines were determined by flow cytometry. Genotyping for the IL-6 gene polymorphism rs2069849 (A > G) was performed using a TaqMan allelic discrimination assay. The proviral load was determined by Real-time polymerase chain reaction. 165 patients were included, 72% women (aged 52 ± 13.1 years), 23% were functionally dependent, and 21% had HAM/TSP. Patients functionally dependent had higher IL-6 and IL-8 levels and lower IL-10 levels. HAM/TSP patients also showed higher IL-6 and IL-8. No associations were observed between any cytokine and chronic pain, pain frequency or intensity. Neither IL-6 polymorphism nor proviral load showed any association with myelopathy, pain, or functionality.