Tropical spastic paraparesis: clinical, immunological, and virological studies in two patients from Martinique

Elevated LGI1-IgG CSF index predicts worse neurological outcome

To determine whether CSF leucine‐rich glioma‐inactivated 1(LGI1)‐IgG titer, index or IgG subclass has prognostic significance, we tested serum and CSF specimens collected concomitantly from 39 seropositive patients. LGI1‐IgG index was elevated (>1) in 21 patients (54%), suggesting intrathecal synthesis. Patients with worse outcome at last follow‐up (modified Rankin Scale >2) had significantly higher index (median 6.57 vs. 0.5, P = 0.048) compared to those with better outcome. Higher CSF LGI1‐IgG4 subclass‐specific titer and index correlated with worse outcome (P < 0.005 for both). These data suggest that evidence of intrathecal LGI1‐IgG synthesis may correlate with neuronal injury and warrant consideration of aggressive immunotherapy.

Proposal for diagnostic criteria of tropical spastic paraparesis/HTLV-I-associated myelopathy (TSP/HAM)

After the first description of TSP/HAM in 1985 and the elaboration of WHO's diagnostic criteria in 1988, the experience of the professionals in this field has increased so that a critical reappraisal of these diagnostic guidelines was considered timely. Brazilian neurologists and observers from other countries met recently to discuss and propose a modified model for diagnosing TSP/HAM with levels of ascertainment as definite, probable, and possible, according to myelopathic symptoms, serological findings, and/or detection of HTLV-I DNA and exclusion of other disorders.

HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) pathogenesis hypothesis. A shift of homologous peptides pairs, central nervous system (CNS)/HTLF-1, HTLV-1/thymus, thymus/CNS, in a thymus-like CNS environment, underlies the pathogenesis of HAM/TSP

Determinants shared by thymus, brain and HTLV-1 induce lymphocytic neurotropism and demyelinization in HAM/TSP, within the framework thymus-like brain environment. The disease evolves in two phases. The first phase of the disease would be dependent on CD4 T-lymphocytes specific for thymic autoantigens, reactivated by viral antigens homologous to thymus and CNS autoantigens. During this phase, demyelinization could be due initially to a stop in the synthesis of myelin following an altered expression of adhesion proteins at the surface of oligodendrocytes and neurons. The second phase, which covers the inflammatory and chronic character of the disease, would be dependent, on the one hand, on CD8 T-lymphocytes specific for viral peptides, and on the other hand, on CD8 T-lymphocytes specific for peptides arising from the cell-proteases induced progressive proteolysis of protein components from the myelin layers and other protein components of the CNS. Non-specific inflammatory and non-inflammatory cytokines keep the activation going of the different cellular types. The thoracic spinal cord cell-location specificity would be linked to a peptidic coherence between HTLV-1 (significant agent), thymus and thoracic spinal cord antigens, genetically peculiar to HAM/TSP patients.

Neuroaxonal dystrophy in HTLV-1-associated myelopathy/tropical spastic paraparesis: neuropathologic and neuroimmunologic correlations

Detailed neuropathologic and immunohistologic analysis of a case of serologically and polymerase chain reaction-confirmed human immunodeficiency virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is reported in a 73-year-old North American black woman. In addition to the usual neuropathologic features of HAM/TSP, including tractal degeneration of the spinal cord, leptomeningeal and perivascular fibrosis, perivascular demyelination and chronic inflammation, neuroaxonal spheroids were prominent in the spinal cord. Neuroaxonal dystrophy was characterized by neurofilamentous masses that were immunoreactive for phosphorylated neurofilament epitopes, but not ubiquitin. Neuroimmunologic analysis of the inflammatory reaction revealed a prevalence of CD8+ T cells and class I major histocompatibility molecules (MHC) (HLA-ABC and beta 2-microglobulin), but very few CD4+ T cells. Microglia were highly reactive for class II MHC (HLA-DR alpha) and this was attributed to activation, rather than CD4 interaction, since CD4 presence was minimal. Inflammatory cytokine immunoreactivity was also detected in glia. It is concluded that the cumulative effects of cytotoxic T cell (CD8) infiltration and the possible involvement of cytokines were responsible for the unusual degree of neuroaxonal dystrophy and vascular fibrosis, as well as the observed demyelination in this case.

Prevalence of HTLV-I antibody among two distinct ethnic groups inhabiting the Amazon region of Brazil

HTLV-I seroprevalences of 3.63% (02/55), 12.19% (10/82) and 13.88% (10/72) were demonstrated among Tiryio, Mekranoiti and Xicrin Amazonian Indians, respectively, by the Western blotting enzyme assay (WBEI). By indirect immunoelectron microscopy (IIEM), 2 Tiriyo, 9 Mekranoiti and 6 Xicrin Amerindians were reactive. Of 44 serum samples from Japanese immigrants, none reacted by any of the techniques before mentioned. One, 8 and 6 serum samples from Tiryio, Mekranoiti and Xicrin Indians, respectively, were both WBEI and IIEM positive. Our results strongly suggest that HTLV-I and/or an HTLV-I antigenic variant circulate (s) among populations living in the Amazon region of Brazil.

Treatment of HTLV-I-associated myelopathy with high-dose intravenous gammaglobulin

Fourteen patients with HTLV-1-associated myelopathy were treated with high-dose intravenous gammaglobulin (IVGG). Ten received 10 g/day of IVGG and 4 received 400 mg/kg of body-weight/day of IVGG for 5 consecutive days. Improvement of spastic paraparesis was observed in 10 within 7 days of the commencement of IVGG. The therapeutic effects were sustained for more than 3 weeks in some patients. There were no side effects. Analysis of factors of relevance to the clinical improvement with IVGG showed that the beneficial response was preferentially found in patients having a high CSF titre of anti-HTLV-I antibodies, a high CSF IgG level and a marked brain MRI abnormality.

Human T-cell leukemia virus type I trans activator induces class I major histocompatibility complex antigen expression in glial cells

Transfection of the tax gene encoding the trans activator of human T-cell leukemia virus type I into glial line cells induced class I major histocompatibility complex (MHC) antigens on these cells. This occurred through the interaction of tax protein with the gene encoding class I MHC antigens but not through any soluble factors, such as interferons, or factors from glial cells. Since neural cells do not usually express MHC antigens, this novel mechanism may be an intermediate event between viral infection and subsequent immune-mediated pathology in the central nervous system.

Elevated levels of interleukin-6 in serum and cerebrospinal fluid of HTLV-I-associated myelopathy/tropical spastic paraparesis

A significant elevation of interleukin-6 (IL-6) level was observed both in serum (mean 0.455 +/- 0.251) and in cerebrospinal fluid (CSF) (mean 0.043 +/- 0.016) obtained from 13 patients with HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) when compared to that of either asymptomatic carriers (mean 0.181 +/- 0.074 and 0.021 +/- 0.015, respectively) or controls (mean 0.208 +/- 0.119 and 0.021 +/- 0.015, respectively). The differences were statistically significant between HAM/TSP and asymptomatic carrier for serum (P less than 0.05) or CSF (P less than 0.01). The correlation indexes between serum IL-6 and anti-HTLV-I antibody titers in serum and CSF were 0.61 (P less than 0.06) and 0.67 (P less than 0.05), respectively. Both the cell count and protein level in CSF correlated with CSF IL-6 activity at 0.68 (P less than 0.01) and 0.56 (P less than 0.05), respectively. The results demonstrate that IL-6 may contribute to the production of anti-HTLV-I antibody, and signs of slight inflammation are present in the central nervous system in HAM/TSP.

Tropical spastic paraparesis: a model of virus-induced, cytotoxic T-cell-mediated demyelination?

Tropical spastic paraparesis is a neurological disorder that is most commonly seen in certain tropical (mainly Caribbean) areas and that presents as a progressive spastic paraparesis and urinary dysfunction. Recent studies have revealed an association between tropical spastic paraparesis and human T-cell lymphotropic virus type I (HTLV-I) infection. We report the results of a detailed morphological and immunocytochemical study of a patient with tropical spastic paraparesis. Lesions were restricted to the spinal cord and optic nerve, where demyelination, inflammation, and fiber loss were common features. Lymphocytes were seen closely applied to nerve fibers within which were changes resembling those seen in myelinated central nervous system cultures exposed to cytokines. Immunocytochemically, HTLV-I p19 core protein and a predominance of CD8+ (suppressor/cytotoxic) T cells and expression of class I major histocompatibility antigen were demonstrated in spinal cord lesions. It is postulated that cytotoxic T cells, either directly or via cytokines, induce lysis of the myelin sheath and subsequently the axon, resulting in a mixed picture of demyelination and axonal loss with secondary tractal degeneration. Despite this destruction, extensive remyelination was evident within affected areas of spinal cord.

Tropical spastic paraparesis. A clinical study of 50 patients from Tumaco (Colombia) and review of the worldwide features of the syndrome

Tropical spastic paraparesis (TSP) is a chronic and slowly progressive endemic myelopathy occurring in geographical isolates in the Caribbean, South India, South Africa, the Seychelles, and Colombia. A detailed clinical and laboratory study was performed on 50 TSP patients from the island of Tumaco (Colombia), in a tropical rain forest area. Most patients were middle-aged blacks, 29 (58%) men and 21 women. In every case, neurological examination confirmed the presence of pyramidal signs in the lower limbs, plus, in 58%, moderate decrease in vibratory perception distally in the feet, bilaterally and symmetrically. Absent ankle jerks were found in 28%. Slow onset and chronic progression were documented in most patients. Positive treponemal serology, from yaws infection in childhood, was found in the serum in 92%, and in 19% also in the cerebrospinal fluid (CSF). No pleocytosis was documented on 27 CSF samples, but increased protein content occurred in 86%, with elevation of gamma-globulins in 78%. Treatment of 20 patients with high doses of penicillin produced no change in the clinical picture. TSP emerges from this review of the literature as a remarkably homogeneous clinical entity worldwide. A retrovirus-human T-lymphotropic virus type 1 (HTLV-1)--has been recently implicated as a possible etiology of the syndrome.

Infection of human T-lymphotropic virus type I to astrocytes in vitro with induction of the class II major histocompatibility complex

To clarify the pathogenesis of human T-lymphotropic virus type I (HTLV-I)-associated myelopathy (HAM), we examined whether HTLV-I infects normal human glial cells in vitro with induction of the major histocompatibility complex (HMC) class II antigen by immunofluorescence method. It was found that about 10% of astrocytes were infected with HTLV-I with induction of class II MHC antigen. Fluorescence-conjugated HTLV-I was adsorbed to 10% of astrocytes. On the contrary, there was no class II MHC antigen expression and very few HTLV-I infection on oligodendrocytes. We speculated that in patients with HAM, HTLV-I-specific, MHC class II antigen restricted, activated CD4+ cells could damage the MHC class II antigen + HTLV-I-infected astrocytes, leading to the disturbance of blood-brain barrier and to the destructive lesion in the central nervous system.