Human T-lymphotropic Virus Type I (HTLV-I) Proviral Load and Clinical Features in Iranian HAM/TSP Patients

HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is the most common neurological manifestation of HTLV-I. The northeast of Iran is an endemic area for this virus. Host genetic and viral factors play important roles in developing HAM/TSP. The aim of this study was to evaluate the proviral load, and clinical features of HAM/TSP among Iranian to compare with other endemic parts of the world. In this systematic retrospective study, HTLV-I proviral load of 102 Iranian patients with HAM/TS,P and 34 healthy carriers in peripheral blood mononuclear cells (PBMCs) were measured using real-time quantitative PCR assay. The diagnosis of HAM/TSP was made in accordance with the World Health Organization criteria. The mean HTLV-I proviral load of Iranian HAM/TSP patients (626 ± 53.03 copies/ 104 PBMCs) was lower than other populations (in Japanese about 800 copies/104 PBMCs and in Brazilians 912.5 ± 778.6 copies/104 PBMCs). In contrast, the mean HTLV-I proviral load amongst Iranian healthy carriers (193 ± 44.375 copies/104 PBMCs) was higher than that of Japanese healthy carriers (about 140 copies/104 PBMCs), and lower than Brazilians (240.5 ± 452.8 copies/104 PBMCs according to the literatures). The most common HAM/TSP neurological symptoms among Iranian, Japanese, and Brazilian populations were gait disturbance, urinary disturbance, paresthesias, weakness, constipation, and lower back pain. The HTLV-I proviral load in HAM/TSP patients and healthy carriers was not significantly associated with age and gender. Differences in HTLV-I proviral load and consequently clinical manifestations among Iranian and other endemic populations might be due the differences in host genetic background and environmental conditions of these populations.