Immunohistochemistry of degenerative changes in the central nervous system in spastic paraparesis associated to human T lymphotropic virus type I (HTLV-I)]

Background: Human T lymphotropic virus type I is associated with tropical spastic paraparesis, that is a chronic and progressive disease which damages specially the cortiespinal tracts. The pathogenesis of this degenerative process remains unknown. Aim: To identify histopathological aspects that could suggest a pathogenic hypothesis we studied immunohistochemical features in spinal cords obtained from patients that died due to progressive spastic paraparesis. Patients and Methods. Five males and five females, who died between 1990 and 2000, with a mean age of 52 years and mean disease duration of 8.6, were studied. All bad a complete clinical and virological diagnosis. Samples were obtained from the frontal motor cortex and spinal cord (cervical, dorsal and lumbar segments), were fixed in formol (10016), included in paraffin, and stained with Haematoxylin and Luxol-fast-blue. Immunohistochemical study was made with anti-neurofilament antibodies 1: 100 (MO 762, DAKO), anti-APP 1:20 (Rabbit Pre Amyloid protein 51-2700 ZYMED), antitau 1:100 (A0024 DAKO) and anti-ubiquitine 1:50 (NCL UBIQm Novocastra). Results: All cases bad demyelinization and axonal loss in the cortico-spinal tracts; distal and segmental demyelinization of Goll tract; axonal thickening, amyloid precursor protein deposits in the white matter; tau protein aggregation in the spinal cord oligodendrocytes; axonal ubiquitination of sensitive and motor tracts, and subcortical white matter Neuronal injury was absent. Conclusions. The systematic damage of motor and sensitive tracts of the spinal-cord and the absence of neuronal damage, defines a degenerative process limited to axons. This central axonopathie could be caused by a disturbance of axoplasmic transport.