Association between high proviral load, cognitive impairment, and white matter brain lesions in HTLV-1-infected individuals.

The association between high proviral load (PVL) in peripheral blood mononuclear cells (PBMC), cognitive disturbance and white matter brain lesions in HTLV-1-infected individuals is still undefined. A cross-sectional study included 62 participants: 22 asymptomatic carriers (mean age 43.4 ± 13.1 years old), 22 patients with HTLV-1-associated myelopathy (HAM/TSP) (mean age 51.5 ± 8.7 years old), and 18 uninfected controls (mean age 52.3 ± 11.1 years old). All individuals fulfilled the following criteria: between 18 and 65 years of age, more than 4 years of formal education, and completed neuropsychological evaluation and HTLV-1 serology. Infected individuals underwent brain conventional magnetic resonance imaging and PVL quantitative PCR (qPCR). Statistical analysis was adjusted in the models by age and education. Cognitive deficit was observed in all groups. Patients with HAM/TSP showed higher neurocognitive deviation in attention and motor skills, higher frequency (84%) of brain white matter lesions, and higher PVL median (range) 8.45 (0.5-71.4) copies/100 PBMC. Brain white matter lesion was associated with verbal memory deficit in HTLV-1-infected individuals (HAM/TSP and asymptomatic carriers) (p = 0.026). In addition, there was a correlation between higher PVL and neurocognitive dysfunction score (processing speed of visuomotor information and visuoconstructive praxis) in HTLV-1-infected patients. The study demonstrates an association between HTLV-1 infection, neurocognitive disorder, and white matter brain lesions on MRI as well as a correlation with higher HTLV-1 PVL, suggesting that the central nervous system involvement by HTLV-1 is not restricted to the spinal cord but involves the whole neuro-axis. HTLV-1-infected individuals should be tested for cognitive impairment.