Epidemiological Aspects and World Distribution of HTLV-1 Infection

CNRS, URA3015 Paris, France.
Frontiers in Microbiology (Impact Factor: 3.99). 11/2012; 3:388. DOI: 10.3389/fmicb.2012.00388
Source: PubMed


The human T-cell leukemia virus type 1 (HTLV-1), identified as the first human oncogenic retrovirus 30 years ago, is not an ubiquitous virus. HTLV-1 is present throughout the world, with clusters of high endemicity located often nearby areas where the virus is nearly absent. The main HTLV-1 highly endemic regions are the Southwestern part of Japan, sub-Saharan Africa and South America, the Caribbean area and foci in Middle East and Australo-Melanesia. The origin of this puzzling geographical or rather ethnic repartition is probably linked to a founder effect in some groups with the persistence of a high viral transmission rate. Despite different socio-economic and cultural environments, the HTLV-1 prevalence increases gradually with age, especially among women in all highly endemic areas. The three modes of HTLV-1 transmission are mother to child, sexual transmission and transmission with contaminated blood products. Twenty years ago, de Thé and Bomford estimated the total number of HTLV-1 carriers to be 10-20 millions people. At that time, large regions had not been investigated, few population-based studies were available and the assays used for HTLV-1 serology were not enough specific. Despite the fact that there is still a lot of data lacking in large areas of the world and that most of the HTLV-1 studies concern only blood donors, pregnant women or different selected patients or high-risk groups, we shall try based on the most recent data, to revisit the world distribution and the estimates of the number of HTLV-1 infected persons. Our best estimates range from 5-10 millions HTLV-1 infected individuals. However, these results were based on approximately 1.5 billion of individuals originating from known endemic areas with reliable available epidemiological data. Correct estimates in other highly populated regions such as China, India, the Maghreb and East Africa is currently not possible, thus, the current number of HTLV-1 carriers is very probably much higher.

Download full-text


Available from: Olivier Cassar
    • "Human T-cell leukemia virus type 1 (HTLV-1 -Family Retroviridae, genus BLV-HTLV retroviruses, Species Human T-lymphotropic virus 1) is present throughout the world, whereas the Southwestern part of Japan, sub-Saharan Africa and South America, the Caribbean area, and spots in Middle East and Australo-Melanesia are characterized as the main HTLV-1 highly endemic regions [Gessain and Cassar, 2012]. HTLV-1 is associated with adult T-cell leukemia/lymphoma (ATL) and with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), besides other inflammatory conditions, but only a few percentage of infected individuals develop diseases associated to the virus[Cook et al., 2013]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The human T-cell leukemia virus type 1 (HTLV-1) is present throughout the world and is associated with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and other inflammatory conditions. The pathogenesis of HAM/TSP involves a chronic inflammatory response in central nervous system (CNS), with the presence of HTLV-1 infected cells and HTLV-1-specific CD8+ lymphocytes. Chemokines may have a role in the infiltration of these cells into the CNS. In this context the present study analyzed the level of plasmatic chemokines CCL2 (MCP-1), CCL5 (RANTES), IL8 (CXCL8), CXCL9 (MIG) and CXCL10 (IP-10) and HTLV-1 proviral load from peripheral blood in 162 asymptomatic carriers and 136 HAM/TSP patients to determine the differences that be associated with the clinical status of the HTLV-1 infection. The results showed that patients with HAM/TSP have significant higher levels of IL8 and CXCL9, and that the level of IL8, CXCL9 and CXCL10 was significantly greater in HTLV-1 infected individuals with high (> 1%) than those with low proviral load (< 1%). However, the levels of the chemokines tested have not showed high sensitivity to discriminate HAM/TSP patients from asymptomatic carriers. In addition, chemokine profiles in asymptomatic carriers and HAM/TSP groups were similar, with no significant increased frequency of higher producers of chemokines in HAM/TSP individuals. Results indicate that the heterogeneity of the individuals in the groups regarding time of infection, duration of disease, proviral load level and other possible confound factors may impair the use of chemokines levels to monitor HTLV-1 carriers in clinical practice. This article is protected by copyright. All rights reserved
    No preview · Article · Jan 2016 · Journal of Medical Virology
  • Source
    • "Nowadays, it is known that HTLV-1 persistently infects CD4+ T cells throughout the individual's whole life. It is estimated that HTLV-1 currently infects approximately 5–10 million individuals throughout the world [2]. HTLV-1 infection is usually asymptomatic; however, it can cause mainly an aggressive and fatal CD4+ T-cell malignancy, the adult T-cell leukemia (ATL), and a neurodegenerative and disabling disorder of central nervous system, HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) in up to 5% of infected individuals. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The human T-cell lymphotropic virus type 1 (HTLV-1) is a retrovirus associated with both proliferative and inflammatory disorders. This virus causes a persistent infection, mainly in CD4+ T lymphocyte. The ability to persist in the host is associated with the virus capacity to evade the immune response and to induce infected T-cell proliferation, once the HTLV-1 maintains the infection mainly by clonal expansion of infected cells. There are several evidences that ORF-I encoded proteins, such as p12 and p8, play an important role in this context. The present study will review the molecular mechanisms that HTLV-1 ORF-I encoded proteins have to induce dysregulation of intracellular signaling, in order to escape from immune response and to increase the infected T-cell proliferation rate. The work will also address the impact of ORF-I mutations on the human host and perspectives in this study field.
    Full-text · Article · Nov 2015 · Journal of Immunology Research
  • Source
    • "Human T-cell lymphotropic virus 1 (HTLV-1) is a member of the Retroviridae family and Deltaretrovirus genus [1]. HTLV- 1 infection occurs worldwide and affects approximately 15 to 20 million individuals on all continents [2] [3] [4]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The present study investigated the association between the rs12979860 polymorphism in the IL-28B gene and HTLV-1 infection as well as the development of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HTLV-1-infected patients (26 HAM/TSP symptomatic and 53 asymptomatic) and 300 seronegative healthy controls were investigated. Plasma levels of the cytokines TNF-α, TNF-β, IL-8, IL-10, IL-6, and IFN-γ from infected patients were measured using an indirect enzyme-linked immunosorbent assay. The HTLV proviral load was measured using a real-time PCR assay, and T-cell subset counts were determined by flow cytometry. Real-time PCR was used to genotype the rs12979860 SNP. The allelic and genotypic distributions displayed no significant differences among the investigated groups. No significant association between the serum cytokine levels and the presence of the rs12979860 SNP in symptomatic and asymptomatic subjects was observed. A positive correlation ( p = 0.0015 ) between TNF-β and IFN-γ was observed in the asymptomatic group, but a positive correlation was only observed ( p = 0.0180 ) between TNF-α and IL-6 in the HAM/TSP group. The proviral load was significantly higher in HAM/TSP patients than in asymptomatic subjects. The present results do not support a previous report indicating an association between the SNP rs12979860 and HAM/TSP outcome.
    Full-text · Article · Nov 2015 · Mediators of Inflammation
Show more