Post-mortem diagnosis of human T lymphotrophic virus type-1 (HTLV-1) associated myelopathy by detection of HTLV-1 DNA in the spinal cord of a patient with post-transfusional myelopathy

Advances in the treatment of human T-cell lymphotropic virus type-I associated myelopathy

INTRODUCTION

Nearly 2-3% of those 10 to 20 million individuals infected with the Human T-cell lymphotropic virus type-1 (HTLV-1); are predisposed to developing HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). It is a neuro-inflammatory disease; differentiated from multiple sclerosis based on the presence of typical neurologic symptoms, confirmation of HTLV-1 infection, and other molecular biomarkers.

AREAS COVERED

A brief review of the epidemiology, host immune responses, and molecular pathogenesis of HAM/TSP is followed by detailed discussions about the host-related risk factors for developing HAM/TSP and success/failure stories of the attempted management strategies.

EXPERT OPINION

Currently, there is no effective treatment for HAM/TSP. Anti-retroviral therapy, peculiar cytokines (IFN-α), some anti-oxidants, and allograft bone marrow transplantation have been used for treating these patients with limited success. Under current conditions, asymptomatic carriers should be examined periodically by a neurologist for early signs of spinal cord injury. Then it is crucial to determine the progress rate to adapt the best management plan for each patient. Corticosteroid therapy is most beneficial in those with acute myelitis. However, slow-progressing patients are best managed using a combination of symptomatic and physical therapy. Additionally, preventive measures should be taken to decrease further spread of HTLV-1 infection.

Inflammation in neuroviral diseases

During any viral infection of the central nervous system (CNS), the extent and nature of neural cell alterations are dictated by the localization of virus replication and, possibly, persistence. However, one additional source of CNS damage comes from the immune response that develops following CNS viral infection. Indeed, despite of its major role in controlling virus spread in the infected CNS, the immune system is equipped with numerous molecular effectors shared with the nervous system that may greatly alter the homeostasis and function of neural cells. Proinflammatory cytokines and metalloproteases belong to this inflammatory cascade. Besides neurovirulence, the crosstalk engaged between neural and immune cells is a major factor determining the outcome of neuroviral infections.

Detection of human T lymphotropic virus type I proviral DNA in patients with diffuse panbronchiolitis

In Japan a number of reported cases of diffuse panbronchiolitis (DPB) have been associated with human T lymphotropic virus type I (HTLV-I) infection. In this study the hypothesis that HTLV-I proviral DNA may be prevalent in DPB was examined using polymerase chain reaction (PCR) for the region of env or the two-step PCR for the pX region of this virus. The presence of HTLV-I proviral DNA was studied in the peripheral blood mononuclear cells (PBMC) obtained from 10 patients with DPB. The presence of proviral DNA in PBMC in 12 patients with chronic obstructive pulmonary disease (COPD), eight patients with idiopathic interstitial pneumonia (IIP), four patients disease were also studied as relevant controls. The lung tissue obtained from 11 patients with DPB, 12 patients with diffuse aspiration bronchiolitis (DAB) at autopsy, and the surgical lung samples obtained from 12 patients with bronchogenic cancer were also studied. Peripheral blood mononuclear cells obtained from one DPB patient and one bronchogenic carcinoma patient were positive for the HTLV-I pX region. The presence of the pX region was also found in the lung tissue of three DPB patients (27.3%) and one DAB patient (8.3%). None of other subjects were positive for HTLV-I proviral DNA, In conclusion, HTLV-I is not the causative virus in the pathogenesis of COPD, IIP, bronchiectasis and bronchogenic carcinoma. There is a likelihood that HTLV-I infection is associated with some cases of DPB; however this association needs further verification.

Human T cell leukemia virus type I infection and chronic myelopathy

The central nervous system (CNS) pathology of HTLV-I associated myelopathy or tropical spastic paraparesis (HAM/TSP) is reviewed, based mainly on 12 autopsy cases of Japanese HAM/TSP with a serological confirmation of HTLV-I infection. The essential histopathological feature of HAM/TSP is a chronic progressive inflammatory process heralded by parenchymal infiltration of memory CD4 cells. The inflammation involves both the grey and white matter of the spinal cord, and progresses for more than three years after the onset of neurological symptoms, resulting in preferential degeneration of the white matter. In cases with a history of more than nine years, however, the spinal cord lesions appears degenerative rather than inflammatory. Both the inflammation and the white matter degeneration are most conspicuous in the lower thoracic cord. The lateral funiculus is always and most severely affected. Although the parenchymal tissue degeneration is not confined to any particular long tracts, symmetrical degeneration of the lateral pyramidal tract is evident in all cases. The involvement of the posterior and anterior funiculi is variable and neurons are relatively well preserved. Since evidence for HTLV-I infection in the CNS is limited to detection of proviral DNA by the polymerase chain reaction (PCR) and isolation of the virus from CSF cells, autoimmune nature of the disease is suspected, but is supported by ample evidence for derangements of the host immune system compatible with those of autoimmune diseases. Recent studies on induction of white matter degeneration in the rat with a topographical similarity to human HAM/TSP is also briefly reviewed. However, in the rat disease, inflammatory cell infiltrations are inconspicuous.