Summary. -Many aspects of the pathogenesis of Human T-cell lymphotropic virus type 1 (HTLV-1) still need further elucidations. Previous studies have indicated that oxidative stress occurs during infection with the other retrovirus, human immunodeficiency virus 1 (HIV-1). Similar results have been observed in some other chronic viral infections including hepatitis B (HBV) and hepatitis C (HCV). In order to reveal possible oxidative stress in HTLV-1-infected patients, we evaluated serum total antioxidant capacity (TAC) as an indicator of oxidative stress in these patients. Forty-four HTLV-1-seropositive individuals were included in this study, consisting of 12 symptomatic and 32 asymptomatic (carrier) cases. Controls consisted of 36 apparently healthy, HTLV-1-, HIV-and hepatitis-seronegative individuals. All symptomatic patients had HTLV-1-associated myelopathy/ tropical spastic paraparesis (HAM/TSP). Serum TAC levels in patients and healthy individuals were measured using a quantitative TAC assay. The antioxidant capacity in HTLV-1-seropositive cases was significantly reduced compared to control group (P = 0.001). In addition, TAC was lower in patients with more than 5 years history of HAM/TSP compared to those with ≤5 years duration of the myelopathy (P = 0.03). Our results show a depletion of TAC during HTLV-1 infection, which intensifies along with the disease progress. This finding indicates a role of the oxidative stress in pathogenesis of HTLV-1. These results may prompt further research to evaluate any possible therapeutic effect of antioxidant dietary supplements for HTLV-1 infected individuals.Keywords: HTLV-1; oxidative stress; total antioxidant capacity (TAC) * Corresponding author. E-mail: youssefim@mums.ac.ir; phone: +98-511-8525007. Abbreviations: HAM/TSP = HTLV-1-associated myelopathy/tropical spastic paraparesis; HBV = hepatitis B virus; HCV = hepatitis C virus; HIV = human immunodeficiency virus; HTLV-1 = human T-lymphotropic virus type 1; ROS = reactive oxygen species; TAC = total antioxidant capacity

ST2 is a member of IL-1 receptor family expressed on Th2 cells and regulates Th2 responces. The gene of ST2 encodes soluble ST2 (sST2) and the transmembrane ST2 (ST2L) isoforms through alternative mRNA splicing. The discovery of IL33/ ST2 signaling pathway, has drawn a great scientifi c attention to this system. sST2 has been shown to be an indacating factor in various infl ammatory conditions. This study aims to evaluate serum sST2 levels in HTLV-1 infected patients. This study included 49 HTLV-1 seropositive cases of which 14 were sympthomatic. Controls consisted of 30 healthy volunteers. sST2 level was measured using a quantitative ELISA assay and the results of the study groups were compared. Corroborating the previous reports, sST2 was lower in females (P = 0.003). The sST2 levels was slightly increased in HTLV-1 patients, though such increase was not statistically significant (P = 0.91), in addition sST2 level did not correlate signifi cantly to the disease duration (P = 0.78). Despite some other chronic viral infection, HTLV-1 seems not to induce high serum sST2. However owing to relatively high normal variation of sST2 levels and rather small sample size, we stongly recommend further reseach with preferably larger sample size to evalute sST2 in HTLV-1 infected patients.