“Epidemiology of HTLV-I and HTLV-II in South America

BIGLIONE MM

HTLV. Truths and Questions

Fundacion Cali Colombia

Lugar: Colombia; Año: 1997; p. 51 - 80

It has been 16 years since the human T-cell lymphotropic virus type I (HTLV-I) independently and in parallel by two groups of American and Japanese investigators, was isolated and characterized as the first known human retrovirus, (1, 2). This virus is considered to be the etiological agent of Adult T Cell Leukemia/Lymphoma (ATLL) (3) and has also been linked with a chronic myelopathy referred to as Tropical Spastic Paraparesis or HTLV-I Associated Myelopathy (TSP/HAM) (4). In 1982 the human T cell leukaemia virus type II (HTLV-II) was isolated from an American patient with a T-cell variant of hairy cell leukaemia (5) thus being the second human oncoretrovirus found. It is highly homologous to the HTLV-I, both in the structure of its genome and in its ability to transform lymphocytes in vitro. It is really interesting the fact that HTLV-II has a preferential tropism for CD8+ T lymphocytes in vivo as well as in vitro (6), in opposition to HTLV-1 which preferentially infects CD4+ T lymphocytes. Yet there is no convincing evidence of HTLV-II specific disease after infection (7). It has been linked to chronic progressive myelophaties similar to TSP/HAM, T cell neoplasias and neurological diseases (8). Magnani et al. (9) described the first case of sensory neuropathy due to HTLV-II in an HIV-1/HTLV-II coinfected patient. Two cases of T-cell variant of hairy cell leukaemia (10) and a chronic neurodegenerative disease in an American Native population have been associated with this virus. However, in a serological and molecular study of 169 patients in France, no evidence of HTLV-I/II infection in T CD8 malignant or reactive lymphoproliferative disorders was found (11). Thus, in contrast to HTLV-I, which etiologic role in Adult T-cell Leukaemia is now well established, there is neither epidemiological nor molecular evidence that HTLV-II may be the causative agent of any specific haematological disease. Finally, the role of this virus in human disease has not yet been established and more evidence of its pathogenicity is necessary.