Establishment of T-lymphoid cell lines from Morroccan patients with tropical spastic paraparesis

Geographic distribution, clinical epidemiology and genetic diversity of the human oncogenic retrovirus HTLV-1 in Africa, the world's largest endemic area

The African continent is considered the largest high endemic area for the oncogenic retrovirus HTLV-1 with an estimated two to five million infected individuals. However, data on epidemiological aspects, in particular prevalence, risk factors and geographical distribution, are still very limited for many regions: on the one hand, few large-scale and representative studies have been performed and, on the other hand, many studies do not include confirmatory tests, resulting in indeterminate serological results, and a likely overestimation of HTLV-1 seroprevalence. For this review, we included the most robust studies published since 1984 on the prevalence of HTLV-1 and the two major diseases associated with this infection in people living in Africa and the Indian Ocean islands: adult T-cell leukemia (ATL) and tropical spastic paraparesis or HTLV-1-associated myelopathy (HAM/TSP). We also considered most of the book chapters and abstracts published at the 20 international conferences on HTLV and related viruses held since 1985, as well as the results of recent meta-analyses regarding the status of HTLV-1 in West and sub-Saharan Africa. Based on this bibliography, it appears that HTLV-1 distribution is very heterogeneous in Africa: The highest prevalences of HTLV-1 are reported in western, central and southern Africa, while eastern and northern Africa show lower prevalences. In highly endemic areas, the HTLV-1 prevalence in the adult population ranges from 0.3 to 3%, increases with age, and is highest among women. In rural areas of Gabon and the Democratic Republic of the Congo (DRC), HTLV-1 prevalence can reach up to 10-25% in elder women. HTLV-1-associated diseases in African patients have rarely been reported in situ on hospital wards, by local physicians. With the exception of the Republic of South Africa, DRC and Senegal, most reports on ATL and HAM/TSP in African patients have been published by European and American clinicians and involve immigrants or medical returnees to Europe (France and the UK) and the United States. There is clearly a huge underreporting of these diseases on the African continent. The genetic diversity of HTLV-1 is greatest in Africa, where six distinct genotypes (a, b, d, e, f, g) have been identified. The most frequent genotype in central Africa is genotype b. The other genotypes found in central Africa (d, e, f and g) are very rare. The vast majority of HTLV-1 strains from West and North Africa belong to genotype a, the so-called 'Cosmopolitan' genotype. These strains form five clades roughly reflecting the geographic origin of the infected individuals. We have recently shown that some of these clades are the result of recombination between a-WA and a-NA strains. Almost all sequences from southern Africa belong to Transcontinental a-genotype subgroup.

Description of a "trans-Saharan" strain of human T-lymphotropic virus type 1 in West Africa

The aim of this study was to assess the prevalence and the molecular epidemiology of human T-lymphotropic virus type 1 (HTLV-1) in a group of pregnant women living in Guinea Bissau. We studied 427 consecutive pregnant women attending 10 centers for HIV-1 infection monitoring in Bissau. HTLV-1 infection was found in 2.6% of the patients. Phylogenetic analysis of the long terminal repeat region showed that 10 isolates were of the cosmopolitan subtype (HTLV-1a) and that only 1 was of the widespread Central African subtype (HTLV-1b). All the cosmopolitan isolates belonged to the HTLV-1aD subgroup, which was first described in North Africa and clustered with other Senegal and Guinea isolates to form a significant West African clade. Our data show a high prevalence of HTLV-1 in Guinea Bissau and suggest the existence of a trans-Saharan strain distributed in North and West Africa, which probably crossed the desert in the past as a result of contacts between nomadic and sedentary populations or along trading routes.

Tropical spastic paraparesis/HTLV-I-associated myelopathy in Europe and in Africa: clinical and epidemiologic aspects

We review here the epidemiologic and clinical aspects of tropical spastic paraparesis, human T-cell lymphotropic virus type I (HTLV-I)-associated myelopathy (TSP/HAM) as observed in Europe and in Africa. Europe is not an endemic region for HTLV-I (seroprevalence in blood donors, < 0.03%), and TSP/HAM is thus rarely observed in European countries. Most of the few patients suffering from TSP/HAM are first- or second-generation immigrants from HTLV-I endemic areas (mostly the West Indies), and the clinicoepidemiologic aspects of these patients are similar to those seen in endemic areas. However, rare cases occur in European-born subjects with or without risk factors for HTLV-I infection, which raises the possibility of limited foci areas in Europe. Although Africa is considered as a primary HTLV-I endemic area, with at least a few million infected inhabitants, epidemiologic data on the situation of TSP/HAM in Africa remain scarce. Relatively few cases of patients with TSP/HAM have been reported in Africa, including some clusters in Zaire (prevalence, 50/100,000) and in South Africa and sporadically in the main cities of some Western, Central, and Eastern African countries. The paucity of clinical and epidemiologic data on TSP/HAM may be linked to several factors, including the paucity of neurologists, the lack of laboratory and radiologic facilities, and the chronicity of the disease, along with the limited number of field epidemiologic studies performed on this topic and the wide diversity of causes (toxic, nutritional, and infectious) of chronic myelopathies as seen on the African continent.