Human T lymphotropic virus type 1 (HTLV-1) is an exogenous retrovirus that persistently infects 20–30 million people worldwide. This virus is etiologically related to the development of adult T-cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) a chronic disease of the central nervous system. The majority of HTLV-1-infected individuals remain lifelong asymptomatic carriers (ACs) of the virus. However, about 3-5% can develop ATL or HAM/TSP. The virus preferentially infects CD4+ T cells – main host cell of HTLV-1 – and rapidly induces cell activation and proliferation and expression of many host genes, including IFN-γ. The exact mechanism underlying these immunological and clinical events still remains unknown. In the current study, we evaluated the peripheral immune response and correlated with clinical symptoms like spasticity and weakness of the lower extremities, and gait abnormalities. 28 HTLV-1 infected patients were studied. Eight of them developed HAM/TSP and 20 were ACs. Total RNA was extracted from peripheric limphomononuclear cells using the TrizolR reagent (Invitrogen, Carlsbad, CA, USA). The quantitative real-time PCR was performed to quantify IFN-γ, IL-4, IL-5 and IL-10. Total RNA (1μg) of each sample was subjected to reverse transcription with Superscript III (Invitrogen). Real-time PCR was performed in StepOne Plus (Applied Biosystems, Foster City, CA) and signal detection was obtained with the Sybr Green reagent (Applied Biosystems). The amount of mRNA in the sample was expressed as the relative amount to the GAPDH and β-actin genes, according to the formula 2-ΔCT, where ΔCT is CTgene – CThousekeeping. The clinical symptoms of each patient were examined. Spasticity was assessed on the Modified Ashworth Scale, the weakness of the lower limb was measured using a manual scale, and the gait was given scores to the devices that assist in gait. The HAM/TSP patients showed higher expression of IFN-γ (Median: 2,9 x 10-3) than Acs (Median: 1,1 x 10-3), with p = 0,0710. The IFN-γ expression was positively correlated to spasticity (r = 0,2795), weakness (r = 0,6580) and gait (r = 0,7216). Interestingly, patients who need wheelchairs had a higher IFN-γ expression than those who don’t need wheelchair (p = 0,0371). The HAM/TSP patients showed higher Th1 response than ACs. The higher IFN-γ expression is correlated with the development and progression of the HAM/TSP.
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