Molecular characterization of human T-lymphotropic virus, type 1 (HTLV-1) found in Kuwait: close similarity with HTLV-1 isolates originating from Mashhad, Iran

Immigrating and vicinity are not risk factors in the prevalence and transmission rate of human T-lymphotropic virus type 1: A Survey in an endemic region of Iran and Afghan refugees

Human T-lymphotropic virus type 1 (HTLV-1) is a retrovirus associated with two life-threatening diseases; HAM/TSP and ATLL. Due to the slow-growing HTLV-1 infection worldwide, WHO urged for elimination. A large border with Afghanistan, northeast Iran is an endemic region for HTLV-1 infection. Historically, Afghanistan has common sociocultural similarities to Persian peoples. This study was conducted to evaluate HTLV-1 prevalence in Afghan refugees. Also, the HTLV-1 transmission rate and understanding of whether or not the Silk Road has been the route of HTLV-1 infection to Iran were investigated. This case-control study was conducted in a rural area of Fariman city, with Afghan residents who migrated around 165 years ago, from 1857, the Treaty of Paris at the end of the Anglo-Persian war, and a refugee camp in Torbat-e-Jam city. These populations in HTLV-1 endemic area were compared to a segregated population of Afghan refugees in Semnan, the centre of Iran. Blood samples of 983 volunteers were assessed with the ELISA method for the presence of HTLV-1 antibodies and then confirmed by PCR technique. All samples from Afghan refugee camps, Semnan and Torbat-e-Jam, were negative for HTLV-1 infection. However, the prevalence of HTLV-1 infection in Fariman, a rural population of Afghan origin, was approximately 2.73%. The results showed that HTLV-1 is not endemic in Afghanistan, a war-stricken region with refugees distributed worldwide. The land Silk Road has not been the route of HTLV-1 transmission to Northeastern Iran. Importantly, HTLV-1 endemicity might occur during a long time of living in an endemic area.

Molecular epidemiology, genetic variability and evolution of HTLV-1 with special emphasis on African genotypes

Human T cell leukemia virus (HTLV-1) is an oncoretrovirus that infects at least 10 million people worldwide. HTLV-1 exhibits a remarkable genetic stability, however, viral strains have been classified in several genotypes and subgroups, which often mirror the geographic origin of the viral strain. The Cosmopolitan genotype HTLV-1a, can be subdivided into geographically related subgroups, e.g. Transcontinental (a-TC), Japanese (a-Jpn), West-African (a-WA), North-African (a-NA), and Senegalese (a-Sen). Within each subgroup, the genetic diversity is low. Genotype HTLV-1b is found in Central Africa; it is the major genotype in Gabon, Cameroon and Democratic Republic of Congo. While strains from the HTLV-1d genotype represent only a few percent of the strains present in Central African countries, genotypes -e, -f, and -g have been only reported sporadically in particular in Cameroon Gabon, and Central African Republic. HTLV-1c genotype, which is found exclusively in Australo-Melanesia, is the most divergent genotype. This reflects an ancient speciation, with a long period of isolation of the infected populations in the different islands of this region (Australia, Papua New Guinea, Solomon Islands and Vanuatu archipelago). Until now, no viral genotype or subgroup is associated with a specific HTLV-1-associated disease. HTLV-1 originates from a simian reservoir (STLV-1); it derives from interspecies zoonotic transmission from non-human primates to humans (ancient or recent). In this review, we describe the genetic diversity of HTLV-1, and analyze the molecular mechanisms that are at play in HTLV-1 evolution. Similar to other retroviruses, HTLV-1 evolves either through accumulation of point mutations or recombination. Molecular studies point to a fairly low evolution rate of HTLV-1 (between 5.6E−7 and 1.5E−6 substitutions/site/year), supposedly because the virus persists within the host via clonal expansion (instead of new infectious cycles that use reverse transcriptase).

Clinical features of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) in northeast Iran

This study aimed to introduce clinical manifestations of patients in northeast Iran with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and describe the epidemiological features, as well as risk factors for HTLV-1 infection. This is a cross-sectional study of HTLV-1 infected cases and HAM/TSP patients referred by outpatient neurology clinics as well as Mashhad Blood Transfusion Center from 2005 to 2010. The study comprises 513 cases, including 358 healthy carriers (HCs) and 145 HAM/TSP patients. The majority of carriers were male (73.5%), whereas 67.6% of HAM/TSP sufferers were female (P < 0.001). The mean age of HAM/TSP patients and HCs was 45.9 ± 13.6 and 39.5 ± 11.58 years, respectively (P < 0.001). The history of transfusion, surgery, hospitalization and cupping was observed in a significant greater number of HAM/TSP patients than the HCs (P < 0.001, P < 0.001, P < 0.001 and P = 0.029, respectively). Gait disturbance was the most common complaint in HAM/TSP patients (72.4%). This research develops an HTLV-1 data registry in an endemic area such as Mashhad which can serve useful purposes, including evaluation of clinical and laboratory characteristics of HAM/TSP patients and epidemiological data of HTLV-1-infected cases.

Epidemiological Aspects and World Distribution of HTLV-1 Infection

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 only approximately 1.5 billion of individuals originating from known HTLV-1 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.

Genomic instability and rapid clinical course in adult T-cell lymphoma/leukemia patient

Adult T-cell leukemia/lymphoma is a distinct clinical entity characterized by a clonal proliferation of malignant T-lymphocytes. The etiologic agent of the disease is a Human T-cell lymphotropic virus type I. It occurs almost exclusively in areas where the virus is endemic; however the disease develops only in the minority of patients who are virus carriers. Karyotyping findings and their correlation with clinical features are still limited in T-cell malignancies, complicated by clinical heterogeneity and a plethora of secondary abnormalities. This study describes detailed chromosomal and fluorescence in situ hybridization results observed in a patient with adult T-cell leukemia/lymphoma and correlates them with clinical characteristics.

Epidemiology of human T-cell lymphotropic virus type 1 infection in blood donors, Israel

The prevalence of infection with human T-cell lymphotropic virus type 1 (HTLV-1) in blood donors from Israel is 1 infection/100,000 persons. In donors originating from Eastern Europe, the Middle East, and Latin America, prevalences are 7.7, 14.6, and 20.4, respectively. HTLV-1 prevalence may be high outside areas where HTLV-1 previously was known to be endemic.

Evolutionary inferences of novel simian T lymphotropic virus type 1 from wild-caught chacma (Papio ursinus) and olive baboons (Papio anubis)

A serological survey of 22 wild-caught South African (Transvaal) chacma baboons (Papio ursinus) and eight olive baboons (Papio anubis) from Kenya indicates that 13 P. ursinus and one P. anubis have antibodies reacting with human T cell leukemia/lymphoma virus type 1 (HTLV-1) antigens, whereas three P. ursinus had a indeterminate reactivity on Western blot analysis. With six primer sets specific to either HTLV-1-Simian T-cell leukemia virus type 1 (STLV-1) or HTLV-2 and encompassing long terminal repeat (LTR), gag, pol, env, and tax sequences, polymerase chain reaction was performed on genomic DNA from peripheral blood mononuclear cells of 18 animals, and the presence of HTLV-1-STLV-1-related viruses was determined in 13 seropositive and three seroindeterminate animals but not in the two HTLV seronegative individuals. Proviral DNA sequences from env (522 bp), pol (120 bp), and complete (755 bp) or partial (514 bp) LTR were determined for three STLV-1-infected P. ursinus and one P. anubis. Comparative and phylogenetic analyses revealed that P. anubis (Pan-486) sequence clusters with one (Pan-1621) of two previously described P. anubis STLV-1. Likewise, P. ursinus viruses (Pur-529, Pur-539, and Pur-543) form a distinct group, different from all known HTLV-1 but closely affiliated with two STLV-1 strains from South African vervets (Cercopithecus aethiops pygerythrus). This study, reporting the first STLV-1 sequences from wild-caught P. ursinus and P. anubis, corroborates the hypothesis of cross-species transmissions of STLV-1 in the wild. Further, phylogenetic analyses indicate that the known HTLV-1 strains do not share a common origin with nonhuman primates STLV in South Africa.

Sequence analysis of the first HTLV-I infection in Germany without relations to endemic areas

In most parts of Europe only a limited number of sporadic cases of HTLV-I infections have been identified. So far, the few cases found in Germany have always been linked to individuals with relations to endemic areas. Here we report the first HTLV-I infection from a German ATL patient without any known risk for HTLV-I infection and with no relations to known endemic areas. The DNA sequence of the provirus was determined, and a phylogenetic analysis based on the LTR sequence established a close relationship with HTLV-I sequences previously found in two Romanian patients. Our data suggest the existence of a previously unrecognized cluster of HTLV-I infections in southeastern or central Europe.

Sero-epidemiologic and phylogenetic studies of HTLV-I infection in 2 countries of the Caspian Sea region

Phylogenetic analysis of HTLV-I variants persisting among population of Turkmenistan and the Republic of Georgia (situated on both sides of the Caspian Sea, not far from a known HTLV-I cluster in Northern Iran) has been carried out. HTLV-I isolates from the above countries were obtained in the course of seroepidemiological investigations. In all, 1,510 blood-donor samples from Turkmenistan and 47 blood samples from hematological patients from Georgia, were tested with different screening and confirmatory assays, including commercial ones. As a result, 7 infected individuals (3 blood donors and 4 relatives of one blood donor) from Turkmenistan and 3 infected individuals (one ATL patient and 2 of his relatives) from Georgia were found. In addition, 4 HTLV-I isolates from Turkmenistan and one from Georgia were cloned and part of their LTR was sequenced. Phylogenetic analysis of sequenced isolates allowed us to conclude that these isolates belonged to sub-type A, one of 3 sub-types of the "Cosmopolitan" type. We found that most of the Turkmenian isolates formed a tight cluster and shared common nucleotide substitutions with isolates originating from Northern Iran (Mashhad). The data obtained suggest that there is a new endemic focus of HTLV-I infection in the Caspian Sea region. Further investigations are required to confirm this hypothesis.

HTLV-Is in Argentina are phylogenetically similar to those of other South American countries, but different from HTLV-Is in Africa

To understand the origin and past dissemination of human T-cell leukemia/lymphotropic virus type I (HTLV-I) in Latin America, we conducted a phylogenetic study of five new HTLV-I isolates from Argentina. We sequenced partial fragments of long terminal repeats (LTR) of the new HTLV-Is, and then the sequences were subjected to a phylogenetic analysis for comparison with other HTLV-Is of various geographical origins. Our results indicated that all the isolates were members of the Cosmopolitan group. Furthermore, most (four out of five isolates) of the new HTLV-Is belonged to the Transcontinental (A) subgroup, the most widespread subgroup of the four subgroups in the Cosmopolitan group. In this subgroup, they were closely related to HTLV-Is found in other South American countries including those of Amerindians, and were different from those found in Africa. In contrast, the remaining one HTLV-I (ARGMF) did not show any clear similarity to known HTLV-I isolates belonging to the Cosmopolitan group. The close similarity of South American HTLV-Is strongly suggests a common origin of the virus in this continent. Our results do not support the proposed idea of recent introduction of HTLV-I into South America as a consequence of the slave trade from Africa, where phylogenetically different HTLV-Is predominate.

Phylogenetic analysis of simian T-lymphotropic virus Type I (STLV-I) in common chimpanzees (Pan troglodytes): evidence for interspecies transmission of the virus between chimpanzees and humans in Central Africa

Serum and peripheral blood leukocytes from the chimpanzees (Pan troglodytes) of the colony of the Laboratory of Central Nervous System Studies, National Institute of Neurological Disorders and Stroke, NIH, were tested for the presence of STLV-I-specific antibodies and proviral DNA. Antibodies were determined by gelatin particle agglutination and Western blot (WB) assays utilizing HTLV-I antigens. Proviral DNA was detected by four PCR assays targeting three different regions of STLV-I genome: the fragments of the env and pol genes and LTR. Twenty of twenty-two DNA samples from WB-positive animals were PCR positive. None of the DNA samples from WB-negative (n = 5) and WB-indeterminate (n = 4) animals was PCR positive. The results of the nested and double nested env PCR tests were fully concordant; the seminested LTR PCR test was much less sensitive. The DNA sequences from the env (483 bp) and the pol (200 bp) genes and LTR (705 bp) were determined for six, two, and two chimpanzee STLV-I isolates, respectively. Phylogenetic analysis revealed that chimpanzee STLV-I isolates can be attributed to three clades. The first of these clades (SS-PTR1/CSA) included STLV-I isolates from the chimpanzees and West African subspecies of African green monkeys (Cercopithecus a. sabaeus). The other clades (S-PTR2 and S-PTR3) included STLV-I isolates only from chimpanzees. However, both S-PTR2 and S-PTR3 clustered together with Central African HTLV-I comprising the human/simian clade (HS-HSA/PTR). This pattern of phylogenetic clustering suggests that interspecies transmission of STLV-I occurred between chimpanzees and African green monkey subspecies as well between chimpanzees and human populations in Central Africa.

Common origin of human T-lymphotropic virus type-I from Iran, Kuwait, Israel, and La Réunion Island

We found previously that Kuwaiti HTLV-I isolates had two nucleotide substitutions in the most frequently sequenced regions of HTLV-I genome, namely: T-->C 4783 in the pol and T-->C 6569 the env genes. These substitutions were observed rarely in other HTLV-I isolates and seemed to be good markers of the HTLV-I lineage, the "epicentre" of which was located in Mashhad, Iran. To test this hypothesis we sequenced the fragments of HTLV-I genome including sites 4783 and 6569 from seven isolates obtained from the Iranians either living in (five isolates) or originating from (two isolates) Mashhad. RFLP-based tests were also designed and used for typing of the substitutions. All seven isolates were positive for T-->C 4783 and six, from which env fragment was amplifiable, were also positive for T-->C 6569. It is highly probable that all the isolates from Mashhadi Jews belong to the same HTLV-I lineage, although they were not typed yet for the presence of T-->C 6569 substitution. Only 2 "non-Middle Eastern" HTLV-1, both from La Réunion Island were positive for both of the substitutions. Another possible member of Mashhadi lineage of HTLV-I is one isolate from southern India and two isolates from the American Indians, British Columbia, Canada. The determination of the T-->C 4783 and T-->C 6569 markers in HTLV-I isolates of different geographical/ethnic origin may be useful for the reconstruction of the routes of HTLV-I spread from the Middle East and/or Indian subcontinent to other regions of the world and, possibly, for gaining insights into the origin of HTLV-I in Asia.

Simian T-lymphotropic virus type 1 (STLV-1) infection in wild yellow baboons (Papio hamadryas cynocephalus) from Mikumi National Park, Tanzania

Serum and peripheral blood leukocytes from wild yellow baboons (Papio hamadryas cynocephalus) were tested for the presence of STLV-1-specific antibodies and proviral DNA. Fourteen of 30 sera tested positive by radioimmunoprecipitation assay (RIPA) with HTLV-1. Among 36 DNA samples tested by PCR 15 were positive by double nested PCR for a fragment of the STLV-1 env gene, the most sensitive assay among PCR tests employed. Of 30 animals that were tested both serologically and by PCR in only 1 case were the results discordant (PCR-positive, antibody-negative). The DNA sequences from env (378 bp), pol (212 bp), and LTR (705 bp) were determined for 5, 5, and 2 Mikumi STLV-1 isolates, respectively. The DNA sequences of Mikumi STLV-1 isolates were virtually identical and phylogenetic analysis revealed that they were clearly distinct from previously published baboon STLV-1 sequences, including those STLV-1 isolates presumed to be from yellow baboons. The results of this study suggest that reliable placement of individual STLV-1 within the PTLV-1 phylogeny requires genomic sequences of STLV-1 isolates from wild animals whose taxonomic identity and geographical origin are firmly established and that the LTR is the genomic region of STLV-1 which is the most informative for cladistic analysis of these viruses.

Molecular epidemiology of HTLV-I in the world

The geographic distribution of human T-cell lymphotropic/leukemia virus type I (HTLV-I) was initially believed to be limited to southwestern Japan, the Caribbean basin, and Africa. However, extensive searches in recent years have discovered its existence in other areas of the world as well as in isolated, ethnic populations such as South Amerindians, Australo-Melanesian aborigines, religiously segregated Jews, and Pygmies. Previous genetic analyses indicated that HTLV-I can be phylogenetically classified into three major lineages: Melanesian, Central African, and Cosmopolitan groups. Recently, more detailed characterization using long terminal repeat sequences (the most variable genomic region) has revealed that the Cosmopolitan group consists of four subtypes: (A) Transcontinental, (B) Japanese, (C) West African, and (D) North African. Most HTLV-I isolates of the same ethnic group from distant locations and those from different groups inhabiting the same area showed phylogenetic similarities. These observations indicate the present distribution of this virus should be interpreted from the anthropological backgrounds of the virus-possessing populations as well as spatial contact among them. Thus, the molecular epidemiology of HTLV-I and its simian counterpart, STLV-I, provides us with important clues for understanding not only the origin and dissemination of this retrovirus but past human movements over the globe.