Comparison of Serum TNF-α Levels and HTLV-1 Proviral Load between Patients with HAM/TSP and Asymptomatic HTLV-1 Carriers

Abstract

Background: Infection with human T-lymphotropic virus type 1 (HTLV-1) remains clinically silent in most of those infected; only a small minority develop HTLV-1–associated myelopathy/tropical spastic paraparesis (HAM/TSP). Tumour necrosis factor alpha (TNF-α) has been proposed as a mediator of this transition, but evidence from peripheral blood is inconsistent, and to our knowledge no such data have been reported from Iraq. Objective: To compare serum TNF-α concentrations and HTLV-1 proviral load between patients with HAM/TSP and asymptomatic HTLV-1 carriers. Materials and Methods: Cross-sectional study of 33 HTLV-1–seropositive individuals aged 17 to 85 years attending neurology clinics in Najaf, Iraq: 17 with clinically defined HAM/TSP and 16 asymptomatic carriers. Serum TNF-α was measured by sandwich ELISA. Proviral load was quantified by albumin-normalised real-time PCR in 30 participants (14 HAM/TSP, 16 carriers) and expressed as copies per 10⁴ peripheral blood mononuclear cells (PBMC). Groups were compared using independent-samples t tests with Welch’s correction and Mann–Whitney U tests, proviral load after log₁₀ transformation; sex was compared using Fisher’s exact test. Effect estimates are reported with 95% confidence intervals (CI). Results: Serum TNF-α did not differ between groups (HAM/TSP 1.57 ± 0.36 pg/mL vs carriers 1.60 ± 0.31 pg/mL; mean difference −0.03 pg/mL, 95% CI −0.27 to 0.21; t = −0.27, p = 0.79; Cohen’s d = −0.09). Proviral load was approximately twice as high in patients as in carriers (geometric means 1,597 vs 781 copies/10⁴ PBMC; ratio 2.05, 95% CI 0.79 to 5.31; p = 0.14), a difference in the expected direction that did not reach statistical significance. The groups did not differ significantly in age (p = 0.20); the sex distribution differed at borderline significance (p = 0.057). Conclusions: Serum TNF-α showed no association with HAM/TSP status in this cohort. The confidence interval excludes a large difference, although the precision of that exclusion is itself limited by the analytical range of the assay, since most measured concentrations fell below its lowest calibrator. Proviral load was higher in patients, consistent with previous reports, but the study was too small to establish this difference. These data do not support serum TNF-α as a peripheral marker distinguishing symptomatic from asymptomatic HTLV-1 infection.