The three human T-lymphotropic virus type I subtypes arose from three geographically distinct simian reservoirs

Safety of intraocular anti-VEGF antibody treatment under in vitro HTLV-1 infection

Introduction

HTLV-1 (human T-cell lymphotropic virus type 1) is a retrovirus that infects approximately 20 million people worldwide. Many diseases are caused by this virus, including HTLV-1-associated myelopathy, adult T-cell leukemia, and HTLV-1 uveitis. Intraocular anti-vascular endothelial growth factor (VEGF) antibody injection has been widely used in ophthalmology, and it is reportedly effective against age-related macular degeneration, complications of diabetic retinopathy, and retinal vein occlusions. HTLV-1 mimics VEGF₁₆₅, the predominant isoform of VEGF, to recruit neuropilin-1 and heparan sulfate proteoglycans. VEGF₁₆₅ is also a selective competitor of HTLV-1 entry. Here, we investigated the effects of an anti-VEGF antibody on ocular status under conditions of HTLV-1 infection in vitro.

Methods

We used MT2 and TL-Om1 cells as HTLV-1-infected cells and Jurkat cells as controls. Primary human retinal pigment epithelial cells (HRPEpiCs) and ARPE19 HRPEpiCs were used as ocular cells; MT2/TL-Om1/Jurkat cells and HRPEpiCs/ARPE19 cells were co-cultured to simulate the intraocular environment of HTLV-1-infected patients. Aflibercept was administered as an anti-VEGF antibody. To avoid possible T-cell adhesion, we lethally irradiated MT2/TL-Om1/Jurkat cells prior to the experiments.

Results

Anti-VEGF antibody treatment had no effect on activated NF-κB production, inflammatory cytokines, chemokines, HTLV-1 proviral load (PVL), or cell counts in the retinal pigment epithelium (RPE) under MT2 co-culture conditions. Under TL-Om1 co-culture conditions, anti-VEGF antibody treatment did not affect the production of activated NF-κB, chemokines, PVL, or cell counts, but production of the inflammatory cytokine IL-6 was increased. In addition, anti-VEGF treatment did not affect PVL in HTLV-1-infected T cells.

Conclusion

This preliminary in vitro assessment indicates that intraocular anti-VEGF antibody treatment for HTLV-1 infection does not exacerbate HTLV-1-related inflammation and thus may be safe for use.

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.

Human T-Cell Leukemia Virus Type 1-Related Diseases May Constitute a Threat to the Elimination of Human Immunodeficiency Virus, by 2030, in Gabon, Central Africa

The Joint United Nations Program on HIV/AIDS (UNAIDS) has adopted the Sustainable Development Goals (SDGs) to end the HIV/AIDS epidemic by 2030. Several factors related to the non-suppression of HIV, including interruptions of antiretroviral therapy (ART) and opportunistic infections could affect and delay this projected epidemic goal. Human T-Cell leukemia virus type 1 (HTLV-1) appears to be consistently associated with a high risk of opportunistic infections, an early onset of HTLV-1 and its associated pathologies, as well as a fast progression to the AIDS phase in co-infected individuals, when compared to HIV-1 or HTLV-1 mono-infected individuals. In Gabon, the prevalence of these two retroviruses is very high and little is known about HTLV-1 and the associated pathologies, leaving most of them underdiagnosed. Hence, HTLV-1/HIV-1 co-infections could simultaneously imply a non-diagnosis of HIV-1 positive individuals having developed pathologies associated with HTLV-1, but also a high mortality rate among the co-infected individuals. All of these constitute potential obstacles to pursue targeted objectives. A systematic review was conducted to assess the negative impacts of HTLV-1/HIV-1 co-infections and related factors on the elimination of HIV/AIDS by 2030 in Gabon.

Seronegative human T-cell lymphotropic virus 1 carriers in blood banks: A potential viral source for silent transmission?

BACKGROUND AND OBJECTIVES

Transfusion-transmitted viruses count among the greatest threats to blood safety. In Argentina, current laws oblige testing all donated blood for the presence of antibodies against human T-cell lymphotropic viruses 1 and 2 (HTLV-1/2). In endemic zones of the country, a high rate of seronegative HTLV-1 individuals with clear evidence of infection because of symptoms and/or presence of tax sequences of HTLV-1 and/or IgG anti-Tax antibodies has been recently described. Migration from endemic to nonendemic zones of Argentina is very frequent.

MATERIALS AND METHODS

During a 1-year period, in the blood bank of Córdoba city, we performed molecular screening of all donors who were born in or arose from endemic zones for HTLV-1/2 in Argentina and neighbouring countries.

RESULTS

By screening 219 bp of HTLV-1/2 tax gene, 0.6% (2/317) of the blood donors proved to be positive for HTLV-1 tax sequence. One of the donors presented anti-Tax antibodies, demonstrating the transcriptional activity of the tax gene, and the other donor was also positive for LTR and pol gene sequences. The HTLV-1 genetic analysis of the LTR sequence determined that it belonged to the Cosmopolitan subtype HTLV-1aA.

CONCLUSION

These findings suggest potential limitations of some currently approved screening assays for HTLV-1 detection applied in some donor populations and the possibility of an HTLV-1 seronegative carrier state with the potential for silent transmission by blood.

Human T-Lymphotropic virus type 1 infection in absence of tax gene: A challenge for molecular diagnosis

This is the first report of HTLV-1 infection without detectable tax gene. Even though the tax gene of HTLV-1 presents high genetic stability, in the case presented here no sequence of tax was detected by three different and widely used molecular assays targeting several sequences of the gene. Nevertheless, HTLV-1 pol and env genes and LTR region were properly detectable. Several PCRs targeting tax sequences have been developed and largely used for molecular diagnosis of HTLV infection since the tax gene of HTLV-1 is known to be well preserved and intolerant to changes or mutations. In the case reported here, molecular detection of the virus was challenging. HTLV prevalence is complex and in many regions remains unknown. The identification of HTLV-infected individuals is important to determine its actual prevalence and design strategies to reduce viral spread. The finding and communication of HTLV-1 defective-provirus strains is important and necessary to guide the selection of representative target sequences on HTLV genome to design molecular assays, highlighting that different sequences should be combined to ensure adequate diagnosis. The latter is especially relevant in cases when discordant results between serological and molecular assays. This report contributes to the knowledge of the overall molecular epidemiology of HTLV-1 and encourages the need of surveillance of HTLV-1 "missed tax gene profiles" and the evaluation of the impact of these defective viral variants on molecular diagnosis and human health.

First Description of Seronegative HTLV-1 Carriers in Argentina

In some areas of Argentina endemic for human T-lymphotropic virus type 1 (HTLV-1), tropical spastic paraparesis is frequent in subjects who lack antibodies against the virus; however, the relevance of this seronegative status in the country has not been investigated. In neighboring countries, HTLV-1 seronegative status has been described in patients with different diseases; however, data regarding features of seronegative HTLV-1 carriers are scarce. We investigated the seronegative status in 124 relatives of 28 HTLV-1 infected subjects from an endemic area in Northwest Argentina. Blood samples and clinical/epidemiological data were collected. Human T-lymphotropic virus type 1 infection was diagnosed by serology and long terminal repeat (LTR) sequence, env and tax gene detection. IgG anti-Tax HTLV-1 antibody, tax gene sequence, and DNA proviral load were also evaluated. Seventy-five percent of the 124 relatives were negative for HTLV-1/2 antibodies; 35.5% were also negative by molecular assays and 64.5% were negative for HTLV-1 LTR and env sequences, but positive for two sequences of HTLV-1 tax gene. Also, 35.7% of these subjects had IgG anti-Tax antibodies. The seronegative HTLV-1 status was significantly associated with male gender, youth, and sensory symptoms/autonomic nervous system dysfunction. High rates of seronegative symptomatic and asymptomatic HTLV-1 carriers in Argentina are described. The evidence highlights that HTLV-1 prevalence may be underestimated worldwide. Larger cohort studies are required to assess disease outcome in these seronegative subjects. Also, the findings emphasize the limitations of ongoing screening assays for diagnosis and blood safety. Therefore, algorithms for HTLV-1 diagnosis should include not only serological but also molecular assays.

Re-emergence of human T-lymphotropic viruses in West Africa

Human T-lymphotropic viruses (HTLV) are Deltaretroviruses that infect millions of individuals worldwide via the same transmission routes as HIV. With the aim of exposing the possible re-emergence of HTLV in West Africa since discovery, a systematic review was carried out, focusing on the distribution of the virus types and significance of frequent indeterminate reports, while highlighting the need for mandatory routine blood screening. Capturing relevant data from discovery till date, sources searched were Google Scholar, CrossRef, NCBI (PubMed), MEDLINE, Research Gate, Mendeley, abstracts of Conferences and Proceedings, organization websites and reference lists of selected papers. A total of 2626 references were initially retrieved using search terms: Worldwide prevalence of HTLV, HTLV in Africa, HTLV in West Africa, HTLV subtypes, HTLV 3 and 4 in Africa, HTLV of African origin, HTLV seroindeterminate results, Spread of HTLV. These references were rigorously trimmed down to 76. Although evidence shows that HTLV is still endemic in the region, West Africa lacks recent epidemiological prevalence data. Thorough investigations are needed to ascertain the true cause of indeterminate Western Blot results. It is imperative that routine screening for HTLVs be mandated in West African health care facilities.

Transmission, Evolution, and Endogenization: Lessons Learned from Recent Retroviral Invasions

Viruses of the subfamily Orthoretrovirinae are defined by the ability to reverse transcribe an RNA genome into DNA that integrates into the host cell genome during the intracellular virus life cycle. Exogenous retroviruses (XRVs) are horizontally transmitted between host individuals, with disease outcome depending on interactions between the retrovirus and the host organism. When retroviruses infect germ line cells of the host, they may become endogenous retroviruses (ERVs), which are permanent elements in the host germ line that are subject to vertical transmission. These ERVs sometimes remain infectious and can themselves give rise to XRVs. This review integrates recent developments in the phylogenetic classification of retroviruses and the identification of retroviral receptors to elucidate the origins and evolution of XRVs and ERVs. We consider whether ERVs may recurrently pressure XRVs to shift receptor usage to sidestep ERV interference. We discuss how related retroviruses undergo alternative fates in different host lineages after endogenization, with koala retrovirus (KoRV) receiving notable interest as a recent invader of its host germ line. KoRV is heritable but also infectious, which provides insights into the early stages of germ line invasions as well as XRV generation from ERVs. The relationship of KoRV to primate and other retroviruses is placed in the context of host biogeography and the potential role of bats and rodents as vectors for interspecies viral transmission. Combining studies of extant XRVs and "fossil" endogenous retroviruses in koalas and other Australasian species has broadened our understanding of the evolution of retroviruses and host-retrovirus interactions.

Origin and prevalence of human T-lymphotropic virus type 1 (HTLV-1) and type 2 (HTLV-2) among indigenous populations in the Americas

Human T-lymphotropic virus type 1 (HTLV-1) is found in indigenous peoples of the Pacific Islands and the Americas, whereas type 2 (HTLV-2) is widely distributed among the indigenous peoples of the Americas, where it appears to be more prevalent than HTLV-1, and in some tribes of Central Africa. HTLV-2 is considered ancestral in the Americas and is transmitted to the general population and injection drug users from the indigenous population. In the Americas, HTLV-1 has more than one origin, being brought by immigrants in the Paleolithic period through the Bering Strait, through slave trade during the colonial period, and through Japanese immigration from the early 20^th century, whereas HTLV-2 was only brought by immigrants through the Bering Strait. The endemicity of HTLV-2 among the indigenous people of Brazil makes the Brazilian Amazon the largest endemic area in the world for its occurrence. A review of HTLV-1 in all Brazilian tribes supports the African origin of HTLV-1 in Brazil. The risk of hyperendemicity in these epidemiologically closed populations and transmission to other populations reinforces the importance of public health interventions for HTLV control, including the recognition of the infection among reportable diseases and events.

Origin of HTLV-1 in hunters of nonhuman primates in Central Africa

Of 78 Gabonese individuals who had received bites from nonhuman primates (NHPs) while hunting, 7 were infected with human T lymphotropic virus (HTLV-1). Five had been bitten by gorillas and were infected with subtype B strains; however, a 12-year-old girl who was severely bitten by a Cercopithecus nictitans was infected with a subtype D strain that was closely related to the simian T lymphotropic virus (STLV-1) that infects this monkey species. Her mother was infected with a subtype B strain. These data confirm that hunters in Africa can be infected by HTLV-1 that is closely related to the strains circulating among local NHP game. Our findings strongly suggest that a severe bite represent a risk factor for STLV-1 acquisition.

Phylogeography of Human T-lymphotropic Virus Type 1 (HTLV-1) Lineages Endemic to Japan

We conducted phylogenetic analyses and an estimation of coalescence times for East Asian strains of HTLV-1. Phylogenetic analyses showed that the following three lineages exist in Japan: "JPN", primarily comprising Japanese isolates; "EAS", comprising Japanese and two Chinese isolates, of which one originated from Chengdu and the other from Fujian; and "GLB1", comprising isolates from various locations worldwide, including a few Japanese isolates. It was estimated that the JPN and EAS lineages originated as independent lineages approximately 3,900 and 6,000 years ago, respectively. Based on archaeological findings, the "Out of Sunda" hypothesis was recently proposed to clarify the source of the Jomon (early neolithic) cultures of Japan. According to this hypothesis, it is suggested that the arrival of neolithic people in Japan began approximately 10,000 years ago, with a second wave of immigrants arriving between 6,000 and 4,000 years ago, peaking at around 4,000 years ago. Estimated coalescence times of the EAS and JPN lineages place the origins of these lineages within this 6,000-4,000 year period, suggesting that HTLV-1 was introduced to Japan by neolithic immigrants, not Paleo-Mongoloids. Moreover, our data suggest that the other minor lineage, GLB1, may have been introduced to Japan by Africans accompanying European traders several centuries ago, during or after "The Age of Discovery." Thus, the results of this study greatly increase our understanding of the origins and current distribution of HTLV-1 lineages in Japan and provide further insights into the ethno-epidemiology of HTLV-1.

Distribution of Two Subgroups of Human T-Lymphotropic Virus Type 1 (HTLV-1) in Endemic Japan

Endemic areas of human T-lymphotropic virus type 1 (HTLV-1) have been reported in Japan as well as tropical Africa, Central and South America and Melanesia. The existence of two subgroups, i.e., the transcontinental and Japanese subgroups, was reported in Japan. In the present study, we provide data on the ratio of the two subgroups in each endemic area and infection foci and examine the distribution of HTLV-1 in Japan and neighboring areas. A 657 bp fragment of env region of HTLV-1 proviral genome was successfully amplified for 183 HTLV-1 positive DNA samples. The subgroup determination was done by RFLP reactions using endonucleases HpaI and HinfI. The northern part of mainland Kyushu, represented by Hirado and Kumamoto, was monopolized by the Japanese subgroup, while the transcontinental subgroup ranged from 20 to 35% in the Pacific coast areas of Shikoku (Kochi), the Ryukyu Archipelago (Kakeroma and Okinawa) and Taiwan. An interesting finding in the present study is the presence of the transcontinental subgroup in Kochi, suggesting the endemicity of the transcontinental subgroup along the Kuroshio Current.

New STLV-3 strains and a divergent SIVmus strain identified in non-human primate bushmeat in Gabon

BACKGROUND

Human retroviral infections such as Human Immunodeficiency Virus (HIV) or Human T-cell Lymphotropic Virus (HTLV) are the result of simian zoonotic transmissions through handling and butchering of Non-Human Primates (NHP) or by close contact with pet animals. Recent studies on retroviral infections in NHP bushmeat allowed for the identification of numerous Simian Immunodeficiency Viruses (SIV) and Simian T-cell Lymphotropic Viruses (STLV) to which humans are exposed. Nevertheless, today, data on simian retroviruses at the primate/hunter interface remain scarce. We conducted a pilot study on 63 blood and/or tissues samples derived from NHP bushmeat seized by the competent authorities in different locations across the country.

RESULTS

SIV and STLV were detected by antibodies to HIV and HTLV antigens, and PCRs were performed on samples with an HIV or/and HTLV-like or indeterminate profile. Fourteen percent of the samples cross-reacted with HIV antigens and 44% with HTLV antigens. We reported STLV-1 infections in five of the seven species tested. STLV-3 infections, including a new STLV-3 subtype, STLV-1 and -3 co-infections, and triple SIV, STLV-1, STLV-3 infections were observed in red-capped mangabeys (C.torquatus). We confirmed SIV infections by PCR and sequence analyses in mandrills, red-capped mangabeys and showed that mustached monkeys in Gabon are infected with a new SIV strain basal to the SIVgsn/mus/mon lineage that did not fall into the previously described SIVmus lineages reported from the corresponding species in Cameroon. The same monkey (sub)species can thus be carrier of, at least, three distinct SIVs. Overall, the minimal prevalence observed for both STLV and SIV natural infections were 26.9% and 11.1% respectively.

CONCLUSIONS

Overall, these data, obtained from a restricted sampling, highlight the need for further studies on simian retroviruses in sub-Saharan Africa to better understand their evolutionary history and to document SIV strains to which humans are exposed. We also show that within one species, a high genetic diversity may exist for SIVs and STLVs and observe a high genetic diversity in the SIVgsn/mon/mus lineage, ancestor of HIV-1/SIVcpz/SIVgor.

The epidemiology of human retrovirus-associated illnesses

Human T-cell leukemia/lymphoma virus type 1 (HTLV-1) was the first oncogenic human retrovirus discovered in 1980. It is estimated that around 10-20 million people are infected with HTLV-1 worldwide. However, HTLV-1 is not a ubiquitous virus. Indeed, HTLV-1 is present throughout the world with clusters of high endemicity including mainly southern Japan, the Caribbean region, parts of South America and intertropical Africa, with foci in the Middle East and Australia. The origin of this puzzling geographical repartition is probably linked to a founder effect in certain human groups. In the high endemic areas, 0.5 to 50% of the people have antibodies against HTLV-1 antigens. HTLV-1 seroprevalence increases with age, especially in women. HTLV-1 has 3 modes of transmission: mother to child, mainly through prolonged breastfeeding (> 6 months); sexual, mainly but not exclusively occurring from male to female; and by blood products contaminated by infected lymphocytes. HTLV-1 is mainly the etiological agent of two very severe diseases: a malignant T CD4+ cell lymphoproliferation of very poor prognosis, named adult T-cell leukemia/lymphoma (ATLL), and a chronic neuro-myelopathy named tropical spastic paraparesis/HTLV-1-associated myelopathy (TSP/HAM). HTLV-1 is also associated with rare anterior uveitis, infective dermatitis and myositis in some high HTLV-1 endemic areas. The repartition of the different molecular subtypes or genotypes is mainly linked to the geographical origin of the infected persons but not to the associated pathology. HTLV-1 possesses a remarkable genetic stability probably linked to viral amplification via clonal expansion of infected cells rather than by reverse transcription. This stability can be used as a molecular tool to gain better insights into the origin, evolution and modes of dissemination of HTLV-1 and infected populations. HTLV-1 originated in humans through interspecies transmission from STLV-1, a very closely related retrovirus, highly endemic in several populations of apes and Old World monkeys.

Short communication: epidemiological evidence that simian T-lymphotropic virus type 1 in Macaca fuscata has an alternative transmission route to maternal infection

Serological inspection of Simian T-lymphotropic Virus Type 1 was conducted for a wild colony of Macaca fuscata, which was captured in the middle Honshu, Japan. The increase of positive rate after the juvenile stage with the positive rate reaching 100% (or 35/35) in youngster and adult stages, was observed. This finding suggests that, in contrast with human T-lymphotropic Virus Type 1, horizontal transmission play an important role in increasing prevalence of STLV-1 with age among M. fuscata.

HTLV type 1 genetic types among native descendants in Argentina

The province of San Salvador de Jujuy, located in the northwest of Argentina, is a highly endemic area for HTLV-1 infection and a foci of tropical spastic paraparesis/HTLV-1-associated myelopathy (HAM/TSP). Therefore, to better understand this, we carried out a genetic characterization of a large set of HTLV-1 strains (n = 65) of descendants of Amerindians from this region. The LTR and env regions were analyzed. The genetic analysis showed that all of these new HTLV-1 isolates from Argentina belong to the Transcontinental subgroup A of the HTLV-1a Cosmopolitan subtype, with the exception of three isolates that cluster within the Japanese subgroup B. Interestingly, the majority of the sequences from Jujuy province belonged to a distinct cluster within the Latin America Transcontinental subgroup, referred to here as the Jujuy subcluster, and were characterized by specific signatures in the LTR. Given that the samples analyzed in this study belong to the Amerindian population and the high prevalence of HTLV-1 in Jujuy in contrast to the low prevalence of this virus in the country, it could be that HTLV-1aA was spread in Argentina from the Amerindians to the cosmopolitan population. Moreover, this is the first report of an HTLV-1aB or Japanese subgroup in descendants of non-Japanese people in South America.

Identification and molecular characterization of new STLV-1 and STLV-3 strains in wild-caught nonhuman primates in Cameroon

Humans and simian species are infected by deltaretroviruses (HTLV and STLV respectively), which are collectively called primate T-cell lymphotropic viruses (PTLVs). In humans, four types of HTLV have been described (HTLV-1 to -4) with three of them having closely related simian virus analogues named STLV-1, 2 and 3. In this study, our aim was to search for a simian HTLV-4-related virus and to document and characterize further the diversity of STLV infections in wild primate populations. We screened 1297 whole blood samples from 13 different primate species from southern Cameroon. Overall, 93 samples gave HTLV-1, HTLV-2 or dual HTLV-1/-2 INNOLIA profiles, 12 were HTLV positive but untypeable and 14 were indeterminate. Subsequently, we performed generic and specific (STLV-1 to -3) tax-rex PCRs to discriminate the different PTLV types, completed with phylogenetic analysis of 450-bp LTR sequences for STLV-1 and 900 bp pX-LTR sequences for STLV-3. We show for the first time that Lophocebus albigena and Cercopithecus cephus carry both STLV-1 and a divergent STLV-3. We also identified a new STLV-1 lineage in one C. cephus. Finally, we identify relative divergence levels in the tax/rex phylogeny suggesting that additional types of PTLV should be defined, particularly for the highly divergent STLV-1(MarB43) strain that we provisionally name STLV-5.

Human T-cell lymphotropic virus type 3: complete nucleotide sequence and characterization of the human tax3 protein

We and others have recently uncovered the existence of human T-cell lymphotropic virus type 3 (HTLV-3), the third member of the HTLV family. We have now sequenced the full-length HTLV-3Pyl43 provirus. As expected, HTLV-3Pyl43 contains open reading frames corresponding to the gag, pol, env, tax, and rex genes. Interestingly, its long terminal repeat (LTR) includes only two Tax-responsive elements, as is the case for type 3 simian T-cell lymphotropic viruses (STLV-3). Phylogenetic analyses reveal that HTLV-3Pyl43 is closely related to central African STLV-3. Unexpectedly, the proximal pX region of HTLV-3Pyl43 lacks 366 bp compared to its STLV-3 counterpart. Because of this deletion, the previously described RorfII sequence is lacking. At the amino acid level, Tax3Pyl43 displays strong similarities with HTLV-1 Tax, including the sequence of a PDZ class I binding motif. In transient-transfection assays, Tax3Pyl43 activates the transcriptions from HTLV-3, HTLV-1, and HTLV-2 LTRs. Mutational analysis indicates that two functional domains (M22 and M47) important for transactivation through the CREB/ATF or NF-kappaB pathway are similar but not identical in Tax1 and Tax3Pyl43. We also show that Tax3Pyl43 transactivates the human interleukin-8 and Bcl-XL promoters through the induction of the NF-kappaB pathway. On the other hand, Tax3Pyl43 represses the transcriptional activity of the p53 tumor suppressor protein as well as the c-Myb promoter. Altogether, these results demonstrate that although HTLV-3 and HTLV-1 have only 60% identity, Tax3Pyl43 is functionally closely related to the transforming protein Tax1 and suggest that HTLV-3, like HTLV-1, might be pathogenic in vivo.

Molecular epidemiology of simian T-cell lymphotropic virus type 1 in wild and captive sooty mangabeys

A study was conducted to evaluate the prevalence and diversity of simian T-cell lymphotropic virus (STLV) isolates within the long-established Tulane National Primate Research Center (TNPRC) colony of sooty mangabeys (SMs; Cercocebus atys). Serological analysis determined that 22 of 39 animals (56%) were positive for STLV type 1 (STLV-1). A second group of thirteen SM bush meat samples from Sierra Leone in Africa was also included and tested only by PCR. Twenty-two of 39 captive animals (56%) and 3 of 13 bush meat samples (23%) were positive for STLV-1, as shown by testing with PCR. Nucleotide sequencing and phylogenetic analysis of viral strains obtained demonstrated that STLV-1 strains from SMs (STLV-1sm strains) from the TNPRC colony and Sierra Leone formed a single cluster together with the previously reported STLV-1sm strain from the Yerkes National Primate Research Center. These data confirm that Africa is the origin for TNPRC STLV-1sm and suggest that Sierra Leone is the origin for the SM colonies in the United States. The TNPRC STLV-1sm strains further divided into two subclusters, suggesting STLV-1sm infection of two original founder SMs at the time of their importation into the United States. STLV-1sm diversity in the TNPRC colony matches the high diversity of SIVsm in the already reported colony. The lack of correlation between the lineage of the simian immunodeficiency virus from SMs (SIVsm) and the STLV-1sm subcluster distribution of the TNPRC strains suggests that intracolony transmissions of both viruses were independent events.

Genetic markers on the HTLV-1 p12I protein sequences from Brazilian HAM/TSP patients and asymptomatic HTLV-1 carrier isolates

The human T cell leukemia/lymphotropic virus type-1 (HTLV-1) genome has approximately 9 kb and contains the pX region that codes for regulatory and accessory proteins. The pX ORF-I encodes for the p12 protein, a 99 aa peptide, which presents several functional putative domains, such as leucine zipper motifs, SH3- binding motifs, and a dileucine motif, p12I. Also, a rare p12IK88 allele was found mainly in HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) patients, suggesting it is a marker of pathogenesis, although recent studies showed p12IK in asymptomatic HTLV-1 carriers. To extend the observations on p12I motifs, we sequenced 26 p12I from HAM/TSP patients and asymptomatic HTLV-1 carriers. Amino acid analysis of 48 p12I motifs demonstrated the presence of several alleles, but the allelic variation, including p12IK, was not prevalent in HAM/TSP isolates. Nonetheless, some genetic markers were recognized in association with isolates from HTLV-1a subgroup B and Brazilian HTLV-1aA strains.

A Bayesian statistical analysis of human T-cell lymphotropic virus evolutionary rates

HTLV is a genetically-stable retrovirus that is considered to have evolved partly in concert with human migrations. Its rate of evolution is low and therefore, difficult to estimate reliably. In the first part of this study, we provide an improved estimate of HTLV evolutionary rate using anthropological calibration of phylogenetic nodes. We investigate two different anthropological calibrations using a Bayesian method that implements a relaxed molecular clock model and can combine data from multiple genes. The analysis shows that the two calibrations are compatible. In the second part, we develop a Bayesian statistical model to combine and compare the anthropology-based estimates of evolutionary rate with a rate recently calculated using pedigree data from vertically HTLV-infected families. We compare the statistical power of the two estimates and show that the current pedigree estimate, although resulting in considerably higher evolutionary rates, is too statistically weak to warrant a re-examination of the commonly used anthropology-based estimates. Statistical uncertainty burdens HTLV rate estimates based on both anthropological calibrations and on pedigree data; the former method rests on an untested assumption, whilst that latter is affected by small sample sizes.

Two distinct STLV-1 subtypes infecting Mandrillus sphinx follow the geographic distribution of their hosts

The mandrill (Mandrillus sphinx) has been shown to be infected with an STLV-1 closely related to HTLV-1. Two distinct STLV-1 subtypes (D and F) infect wild mandrills with high overall prevalence (27.0%) but are different with respect to their phylogenetic relationship and parallel to the mandrills' geographic range. The clustering of these new STLV-1mnd sequences with HTLV-1 subtype D and F suggests first, past simian-to-human transmissions in Central Africa and second, that species barriers are easier to cross over than geographic barriers.

High variety of different simian T-cell leukemia virus type 1 strains in chimpanzees (Pan troglodytes verus) of the Taï National Park, Côte d'Ivoire

We found human T-cell leukemia virus type 1- and simian T-cell leukemia virus type 1 (STLV-1)-related infections in 5 of 10 chimpanzees originating from three groups of wild chimpanzees. The new virus isolates showed a surprising heterogeneity not only in comparison to STLV-1 described previously in other primate species but also between the different chimpanzee groups, within a group, or even between strains isolated from an individual animal. The interdisciplinary combination of virology, molecular epidemiology, and long-term behavioral studies suggests that the primary route of infection might be interspecies transmission from other primates, such as red colobus monkeys, that are hunted and consumed by chimpanzees.

High prevalence of human T-lymphotropic virus type 1 (HTLV-1) in immigrant male-to-female transsexual sex workers with HIV-1 infection

Human T-lymphotropic virus type 1 and 2 (HTLV-1 and HTLV-2) infections in Europe are limited to intravenous drug users and migrants coming from areas in which they are endemic. A survey was undertaken of HTLV-1 and HTLV-2 infections in 393 recent immigrants: 167 HIV-1 positive subjects (including 52 male-to-female transsexual sex workers) and 226 pregnant HIV-1 negative women. The prevalence of HTLV-1 was 3.6% in the HIV-1 positive group and 0.9% in the HIV-1 negative group. The highest HTLV-1 prevalence in both groups was found in persons from Latin America, particularly those born in Peru (up to 26% in the HIV-1 positive group). All of the HIV-1/HTLV-1 co-infected individuals were male-to-female transsexual sex workers in whom the overall prevalence of HTLV-1 infection was 11.5%. HTLV-2 was only found in the HIV-1 positive group (prevalence 1.2%); all of the infected subjects were transsexual sex workers from Brazil (overall prevalence 6.4%). Phylogenetic analysis showed that all of the HTLV-1 isolates were of the cosmopolitan type, clustering with other strains circulating in the patients' birthplaces; the HTLV-2 isolates were of subtype 2a, and clustered significantly with other Brazilian strains. These results suggest the independent origin of each infection in the patient's birthplace. The data raise concerns about the further spread of HTLV infections mainly through the sexual route.

Characterization of a new simian T-lymphocyte virus type 1 (STLV-1) in a wild living chimpanzee (Pan troglodytes verus) from Ivory Coast: evidence of a new STLV-1 group?

A new strain of simian T-lymphotropic virus type 1 in blood samples from a chimpanzee that lived in the tropical rainforest of Ivory Coast is described. The sequence obtained from the long terminal repeat region of the genome is significantly divergent from all known human and nonhuman primate T-lymphotropic virus type 1 strains (963% homology to the closest related strains from Central African subtype B) and clusters with none of the established clades. The tax sequences reveal two sequence differences that seem to be unique as they are not found in any of the HTLV-1 or STLV-1 tax sequences from the public databases.

Molecular and phylogenetic analyses of 16 novel simian T cell leukemia virus type 1 from Africa: close relationship of STLV-1 from Allenopithecus nigroviridis to HTLV-1 subtype B strains

A serological survey searching for antibodies reacting with human T-cell leukemia virus type 1 (HTLV-1) antigens was performed on a series of 263 sera/plasma obtained from 34 monkey species or subspecies, originating from different parts of Africa. Among them, 34 samples exhibited a typical HTLV-1 Western blot pattern. Polymerase chain reaction was performed with three primer sets specific either to HTLV-1/STLV-1 or HTLV-2 and encompassing gag, pol, and tax sequences, on genomic DNA from peripheral blood mononuclear cells of 31 animals. The presence of HTLV-1/simian T-cell leukemia virus type 1 (STLV-1) related viruses was determined in the 21 HTLV-1 seropositive animals tested but not in the 10 HTLV-1 seronegative individuals. Proviral DNA sequences from the complete LTR (750 bp) and a portion of the env gene (522 bp) were determined for 16 new STLV-1 strains; some of them originating from species for which no STLV-1 molecular data were available as Allenopithecus nigroviridis and Cercopithecus nictitans. Comparative and phylogenetic analyses revealed that these 16 new sequences belong to five different molecular groups. The A. nigroviridis STLV-1 strains exhibited a very strong nucleotide similarity with HTLV-1 of the subtype B. Furthermore, four novel STLV-1, found in Cercocebus torquatus, C. m. mona, C. nictitans, and Chlorocebus aethipos, were identical to each other and to a previously described Papio anubis STLV-1 strain (PAN 503) originating from the same primate center in Cameroon. Our data extend the range of the African primates who could be permissive and/or harbor naturally STLV-1 and provide new evidences of cross-transmission of African STLV-1 between different monkey species living in the same environment and also of STLV-1 transmissions from some monkeys to humans in Central Africa.

Phylogenetic characterization of a new HTLV type 1 from the Ainu in Japan

Human T cell leukemia virus type 1 (HTLV-1) is endemic among three ethnically distinguishable populations in Japan (the Ainu, Ryukyuans, and Wajin), which, together, account for most of the population in Japan. While much is known about the phylogeny of the Ryukyuan and Wajin strains of HTLV-1, only one Ainu strain has been phylogenetically analyzed. We report here a new HTLV-1 strain from the Ainu. The new isolate (U8306), as well as the previously reported isolate, are members of the Cosmopolitan group and further belong to the Transcontinental subgroup. This subgroup also predominates among the Ryukyuans, whereas the Japanese subgroup is the major subgroup among the Wajin. The predominance of subgroup A in the Ainu and Ryukyuans suggests that they share a common origin of HTLV-1.

Dating the origin of the African human T-cell lymphotropic virus type-i (HTLV-I) subtypes

To investigate the origin of the African PTLV-I virus, we phylogenetically analyzed the available HTLV-I and STLV-I strains. We also attempted to date the presumed interspecies transmissions that resulted in the African HTLV-I subtypes. Molecular-clock analysis was performed using the Tamura-Nei substitution model and gamma distributed rate heterogeneity based on the maximum-likelihood topology of the combined long-terminal-repeat and env third-codon-position sequences. Since the molecular clock was not rejected and no evidence for saturation was found, a constant rate of evolution at these positions for all 33 HTLV-I and STLV-I strains was reasonably assumed. The spread of PTLV-I in Africa is estimated to have occurred at least 27,300 +/- 8,200 years ago. Using the available strains, the HTLV-If subtype appears to have emerged within the last 3,000 years, and the HTLV-Ia, HTLV-Ib, HTLV-Id, and HTLV-Ie subtypes appear to have diverged between 21,100 and 5,300 years ago. Interspecies transmissions, most probably simian to human, must have occurred around that time and probably continued later. When the synonymous and nonsynonymous substitution ratios were compared, it was clear that purifying selection was the driving force for PTLV-I evolution in the env gene, irrespective of the host species. Due to the small number of strains in some of the investigated groups, these data on selective pressure should be taken with caution.

CHAT oral polio vaccine was not the source of human immunodeficiency virus type 1 group M for humans

A book published in 1999 hypothesized that the scientists who worked with the CHAT type 1 attenuated poliomyelitis strain, tested in the former Belgian Congo in the late 1950s, had covertly prepared the vaccine in chimpanzee kidney cells contaminated with a simian immunodeficiency virus, which evolved into human immunodeficiency virus type 1 group M. This article summarizes the results of the investigation conducted by the author to determine the legitimacy of the accusation. Testimony by eyewitnesses, historical documents of the time, epidemiological analysis, and analysis of ancillary phylogenetic, virological, and polymerase chain reaction data all indicate that this hypothesis is false.

HTLV-I/HTLV-II coinfection in an AIDS patient from São Paulo, Brazil

A serological survey for HTLV infection identified an AIDS patient with HTLV-I/HTLV-II dual seroreactivity. Two further sequential blood samples were collected (samples A and B) for PCR, restriction fragment length polymorphism (RFLP), and sequence analyses of HTLV-I and HTLV-II strains. PCR analyses confirmed dual infection in both samples. Restriction digests of the env region amplified from sample A showed the presence of an HTLV-IIa subtype; the HTLV-II provirus was found to be defective in the pol and env regions in the second sample from this patient. RFLP analysis of the HTLV-II LTR region of both samples confirmed this finding and identified an a5/bzl restriction type. Nucleotide sequence analyses revealed full homology in the HTLV-I env and LTR regions and in the HTLV-II LTR region between the two samples. These findings document the first case of an HTLV-I/HTLV-II coinfection that was fully confirmed and characterized by means of molecular analyses.

Tempo and mode of human and simian T-lymphotropic virus (HTLV/STLV) evolution revealed by analyses of full-genome sequences

We investigated the tempo and mode of evolution of the primate T-lymphotropic viruses (PTLVs). Several different models of nucleotide substitution were tested on a general phylogenetic tree obtained using the 20 full-genome HTLV/STLV sequences available. The likelihood ratio test showed that the Tamura and Nei model with discrete gamma-distributed rates among sites is the best-fitting substitution model. The heterogeneity of nucleotide substitution rates along the PTLV genome was further investigated for different genes and at different codon positions (cdp's). Tests of rate constancy showed that different PTLV lineages evolve at different rates when first and second cdp's are considered, but the molecular-clock hypothesis holds for some PTLV lineages when the third cdp is used. Negative selection was evident throughout the genome. However, in the gp46 region, a small fragment subjected to positive selection was identified using a Monte Carlo simulation based on a likelihood method. Employing correlations of the virus divergence times with anthropologically documented migrations of their host, a possible timescale was estimated for each important node of the PTLV tree. The obtained results on these slow-evolving viruses could be used to fill gaps in the historical records of some of the host species. In particular, the HTLV-I/STLV-I history might suggest a simian migration from Asia to Africa not much earlier than 19,500-60,000 years ago.

Different models, different trees: the geographic origin of PTLV-I

Using nucleotide sequences from three genomic regions of the human and simian T-cell lymphotropic virus type I (HTLV-I/STLV-I)-consisting of 69 sequences from a 140-bp segment of the pol region, 98 sequences from a 503-bp segment of the LTR, and 154 sequences from a 386-bp segment of the env region-we tested two hypotheses concerning the geographic origin and evolution of STLV-I and HTLV-I. First, we tested the assumption of equal rates of evolution along STLV-I and HTLV-I lineages using a likelihood ratio test to ascertain whether current levels of genomic diversity can be used to determine ancestry. We demonstrated that unequal rates of evolution along HTLV-I and STLV-I lineages have occurred throughout evolutionary time, thus calling into question the use of pairwise distances to assign ancestry. Second, we constructed phylogenetic trees using multiple phylogenetic techniques to test for the geographic origin of STLV-I and HTLV-I. Using the principle of likelihood, we chose a statistically justified model of evolution for each data set. We demonstrated the utility of the likelihood ratio test to determine which model of evolution should be chosen for phylogenetic analyses, revealing that using different models of evolution produces conflicting results, and neither the hypothesis of an African origin nor the hypothesis of an Asian origin can be rejected statistically. Our best estimates of phylogenetic relationships, however, support an African origin of PTLV for each gene region.

Nucleotide sequence analysis of human T-cell lymphotropic virus type I pX and LTR regions from patients with sicca syndrome

Human T-cell lymphotropic virus type I (HTLV-I) is associated with adult T-cell leukemia (ATL) and tropical spastic paraparesis/HTLV-I-associated myelopathy (TSP/HAM). Other inflammatory disorders may occur in HTLV-I-infected patients, such as sicca syndrome resembling Sjögren's syndrome. The sicca syndrome may be the unique clinical manifestation of HTLV-I infection, but is associated frequently with TSP/HAM, which could suggest that sicca syndrome might be an early event in disease progression to TSP/HAM in some cases. We investigated whether peculiar pX and LTR mutations could be related to sicca syndrome, or might argue the existence of clinical progression to TSP/HAM. pX, especially pX(I), pX(II), and pX(IV) ORFs corresponding to Tax cytotoxic T-lymphocyte epitopes, and LTR regions from Caribbean patients who have sicca syndrome with or without TSP/HAM, ATL patients, and healthy carriers were sequenced. The sequences were aligned and compared with ATK-1 prototype and published sequences. LTR sequences exhibited 1.5-2.4% of divergence with ATK-1. pX-sequenced regions showed a lower homology within p12(I) encoding sequences. Only few mutations were found within functionally important regions, but were not associated specifically with the clinical status. Finally, no mutations that could be related to sicca syndrome or argue the existence of clinical progression to TSP/HAM were found. It would be of interest to study the clinical evolution of HTLV-I-sicca syndrome in patients and to determine HTLV-I sequences from peripheral blood and salivary glands at different stages.

Sequence of the env gene of some KwaZulu-Natal, South African strains of HTLV type I

Phylogenetic analysis of HTLV-I suggests three main subtypes, namely, cosmopolitan, Central African, and Australo-Melanesian. HTLV-I is endemic in KwaZulu-Natal, South Africa. However, sequence data on the local strains are limited to the LTR region. The env gene of the local strain was amplified and sequenced from the peripheral blood of five seropositive individuals. Four had HTLV-I-associated myelopathy and one had infective eczema. The sequence analysis of the env gene showed a greater then 99% homology of the local strains. They were closely related to the North American strains (99.3%), followed by the Japanese strains (98.3-98.9%). Phylogenetic studies linked the local strains to the cosmopolitan subtype. This study provides new sequence data on the env gene of the local HTLV-I strain.

The discovery of two new divergent STLVs has implications for the evolution and epidemiology of HTLVs

We have isolated and characterised two divergent simian T-lymphotropic viruses (STLV), not belonging to the established human and simian T-lymphotropic virus lineages HTLV-1/STLV-1 and HTLV-2. STLV-L, from an Eritrean sacred baboon (Papio hamadryas), has been typed as a third type of simian T-lymphotropic virus, distinct from HTLV-1/STLV-1 and HTLV-2. The other virus, isolated from Congolese bonobos (Pan paniscus), is a distinct member of the HTLV-2 clade and has been designated STLV-2. The isolation of these two simian viruses shows that the spectrum of HTLVs/STLVs is larger than previously expected. Our data indicate that the two lineages STLV-L and HTLV-2/STLV-2 are of African origin, while the HTLV-1/STLV-1 lineage has been shown to be of Asian origin. These data, together with our phylogenetic analyses, suggest an African origin of the HTLV/STLV ancestor, which provides new clues about virus dissemination. Furthermore, the atypical serological profiles exhibited by STLV-L or STLV-2 infected animals in western blot, raise questions about the efficiency of current screening methods to type highly divergent HTLVs/STLVs. Considering the growing interest in xenotransplantations, more epidemiological and biological knowledge of simian and human T-lymphotropic viruses is necessary to estimate the risk of interspecies transmissions.

The origin and evolution of human T-cell lymphotropic virus type II (HTLV-II) and the relationship with its replication strategy

In this review, the origin and evolution of the human T-cell lymphotropic virus type II (HTLV-II) are discussed, with particular emphasis on its high genomic stability. In particular, it appears that the virus originated in the African continent and has been infecting human populations for several thousands of years. The very low divergence accumulated on average between different viral strains during such a long period could be explained by considering that in infected individuals the viral amplification could be due mainly to the clonal expansion of the infected cells, via cellular mitosis, rather than to reverse transcription. HTLV-II was introduced into the American continent during one or more migrations of HTLV-II-infected Asian populations over the Bering land bridge, some 15,000-35,000 years ago. Finally, during the last few decades, HTLV-II has been transmitted from native Amerindians to injecting drug users (IDUs). It might be speculated that at least two separate introductions of HTLV-II in European IDUs from US IDUs have occurred, due to the practice of needle-sharing among IDUs.

Genomic Evolution, Patterns of Global Dissemination, and Interspecies Transmission of Human and Simian T-cell Leukemia/Lymphotropic Viruses

Using both env and long terminal repeat (LTR) sequences, with maximal representation of genetic diversity within primate strains, we revise and expand the unique evolutionary history of human and simian T-cell leukemia/lymphotropic viruses (HTLV/STLV). Based on the robust application of three different phylogenetic algorithms of minimum evolution–neighbor joining, maximum parsimony, and maximum likelihood, we address overall levels of genetic diversity, specific rates of mutation within and between different regions of the viral genome, relatedness among viral strains from geographically diverse regions, and estimation of the pattern of divergence of the virus into extant lineages. Despite broad genomic similarities, type I and type II viruses do not share concordant evolutionary histories. HTLV-I/STLV-I are united through distinct phylogeographic patterns, infection of 20 primate species, multiple episodes of interspecies transmission, and exhibition of a range in levels of genetic divergence. In contrast, type II viruses are isolated from only two species (Homo sapiens and Pan paniscus) and are paradoxically endemic to both Amerindian tribes of the New World and human Pygmy villagers in Africa. Furthermore, HTLV-II is spreading rapidly through new host populations of intravenous drug users. Despite such clearly disparate host populations, the resultant HTLV-II/STLV-II phylogeny exhibits little phylogeographic concordance and indicates low levels of transcontinental genetic differentiation. Together, these patterns generate a model of HTLV/STLV emergence marked by an ancient ancestry, differential rates of divergence, and continued global expansion.

The risk of using baboons as transplant donors. Exogenous and endogenous viruses

African nonhuman primates harbor several exogenous and endogenous retroviruses which deserve further consideration in the transplant setting. In particular, simian foamy viruses (SFV), simian T-cell lymphotropic virus (STLV), baboon endogenous virus (BaEV), and simian endogenous retrovirus (SERV) are all carried by baboons and may be transmitted to humans by transplantation. We have found baboons to have high seroprevalence rates to both SFV and STLV, and molecular and serologic methods have been developed to detect such agents. In addition, current nonhuman primate breeding programs have thus far not focused on eliminating these viruses. In summary, the close genetic relationship with humans and number of persistent viral infections in baboons translates into a much greater infectious disease risk when compared to that of other domesticated species.

The HTLV type I sequence from an asymptomatic German blood donor is related to sequences from South America

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 were individuals from endemic areas or with relations to endemic areas. Here we report an HTLV-I infection from an asymptomatic female German blood donor whose only known potential risk was a former partner from South America, where HTLV-I is known to be endemic. The DNA sequence of the LTR region was determined and a phylogenetic analysis indeed suggested homologies with HTLV-I sequences from South America.

Simian T-cell lymphotropic virus type 1 from Mandrillus sphinx as a simian counterpart of human T-cell lymphotropic virus type 1 subtype D

A recent serological and molecular survey of a semifree-ranging colony of mandrills (Mandrillus sphinx) living in Gabon, central Africa, indicated that 6 of 102 animals, all males, were infected with simian T-cell lymphotropic virus type 1 (STLV-1). These animals naturally live in the same forest area as do human inhabitants (mostly Pygmies) who are infected by the recently described human T-cell lymphotropic virus type 1 (HTLV-1) subtype D. We therefore investigated whether these mandrills were infected with an STLV-1 related to HTLV-1 subtype D. Nucleotide and/or amino acid sequence analyses of complete or partial long terminal repeat (LTR), env, and rex regions showed that HTLV-1 subtype D-specific mutations were found in three of four STLV-1-infected mandrills, while the remaining monkey was infected by a different STLV-1 subtype. Phylogenetic studies conducted on the LTR as well as on the env gp21 region showed that these three new STLV-1 strains from mandrills fall in the same monophyletic clade, supported by high bootstrap values, as do the sequences of HTLV-1 subtype D. These data show, for the first time, the presence of the same subtype of primate T-cell lymphotropic virus type 1 in humans and wild-caught monkeys originating from the same geographical area. This strongly supports the hypothesis that mandrills are the natural reservoir of HTLV-1 subtype D, although the possibility that another monkey species living in the same area could be the original reservoir of both human and mandrill viruses cannot be excluded. Due to the quasi-identity of both human and monkey viruses, interspecies transmission episodes leading to such a clade may have occurred recently.

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.

Two new human T-lymphotropic virus type I phylogenetic subtypes in seroindeterminates, a Mbuti pygmy and a Gabonese, have closest relatives among African STLV-I strains

Six new HTLV-I strains from seroindeterminate individuals were analyzed: four from Gabon, one from a Mbuti Efe pygmy in Congo (formerly Zaire), and one from a Congolese patient residing in Belgium. The LTR and env regions were sequenced and phylogenetic analyses were performed to characterize the new strains. Nucleotide divergence and phylogeny results showed that four of the new strains belong to the HTLV-Ib Central African subtype. The other two strains, one from the Efe pygmy and one from Gabon, lie on distinct branches of the LTR and env trees with respect to the four major HTLV-I subtypes. Despite the low bootstrap values, likelihood mapping analyses proved that these strains can be considered two new HTLV-I molecular subtypes, putatively named HTLV-Ie and HTLV-If. A relation exists in the phylogenetic trees and in the likelihood maps between the new subtypes and African STLV-I strains from Papio spp. and Cercopithecus spp., suggesting one or more interspecies transmission events in the past. This study demonstrates that the phylogenetic subtyping of HTLV-I in the African continent is far from being completed and that samples presenting an indeterminate serology can potentially belong to new subtypes in humans. In addition, present day serological tests do not reliably type strains within the HTLV-Ib Central African subtype.

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.

African origin of human T-lymphotropic virus type 2 (HTLV-2) supported by a potential new HTLV-2d subtype in Congolese Bambuti Efe Pygmies

We identified a potential new subtype within human T-cell lymphotropic virus type 2 (HTLV-2), HTLV-2d, present in members of an isolated Efe Bambuti Pygmy tribe. Two of 23 Efe Pygmies were HTLV-2 seropositive, with HTLV-2 Western blot and enzyme-linked immunosorbent assay reactivities. From one of them the entire genome of the HTLV-2 strain Efe2 could be amplified and sequenced. In all gene regions analyzed, this strain was the most divergent HTLV-2 strain, differing by 2.4% (tax/rex) to 10.7% (long terminal repeat) from both subtypes HTLV-2a and HTLV-2b, yet major functional elements are conserved. The similarity between the HTLV-2 Efe2 Gag and Env proteins and the corresponding HTLV-2a and -2b proteins is consistent with the observed serological reactivity. In the proximal pX region, one of the two alternative splice acceptor sites is abolished in HTLV-2 Efe2. Another interesting feature of this potential new subtype is that it has a Tax protein of 344 amino acids (aa), which is intermediate in length between the HTLV-2a Tax protein (331 aa) and the HTLV-2b and -2c Tax proteins (356 aa) and similar to the simian T-cell lymphotropic virus type 2 (STLV-2) PP1664 Tax protein. Together these two findings suggest a different phenotype for the HTLV-2 Efe2 strain. Phylogenetic analyses confirmed that the Pygmy Efe2 strain potentially belonged to a new and quite divergent subtype, HTLV-2d. When the STLV-2 bonobo viruses PP1664 and PanP were used as an outgroup, it was clear that the Pygmy HTLV-2 Efe2 strain had the longest independent evolution and that HTLV-2 evolution is consistent with an African origin.

The simian T-lymphotropic virus STLV-PP1664 from Pan paniscus is distinctly related to HTLV-2 but differs in genomic organization

We have isolated a highly divergent simian T-lymphotropic virus, STLV-PP1664, from a wild-caught bonobo (Pan paniscus). Previous phylogenetic analysis suggested that this virus represents an additional type of STLV but this has now become a matter of discussion. We have now obtained and analyzed the entire genome of STLV-PP1664. All major genes and their corresponding viral messengers were identified. Sequence comparison and phylogenetic analysis indicated that this virus, together with the closely related panp isolate, belongs to an early lineage within the PTLV-2 clade, differing from HTLV-2 by about 25%. In contrast to the HTLV-1 and HTLV-2 LTR, only two 21-bp repeats instead of three were found in the STLV-PP1664 LTR. Additional messengers, resulting from alternative splicing, potentially encode five different accessory proteins from open reading frames in the pX region: prorfI, porfII, ptorfV', and two isoforms of Rex. The amino acid sequences of these proteins are only distinctly related to the accessory proteins from HTLV-2. These data suggest a different genomic organization of the STLV-PP1664 pX region than that of HTLV-2. We conclude that STLV-PP1664, although related to HTLV-2, has some distinct features in the LTR and the pX regions, the impact of which needs further investigation. Although arguments pro and contra a distinct classification are nearly equally balanced, we propose to classify this virus as an STLV-2, designated STLV-2PP1664.

Wild primate populations in emerging infectious disease research: the missing link?

Wild primate populations, an unexplored source of information regarding emerging infectious disease, may hold valuable clues to the origins and evolution of some important pathogens. Primates can act as reservoirs for human pathogens. As members of biologically diverse habitats, they serve as sentinels for surveillance of emerging pathogens and provide models for basic research on natural transmission dynamics. Since emerging infectious diseases also pose serious threats to endangered and threatened primate species, studies of these diseases in primate populations can benefit conservation efforts and may provide the missing link between laboratory studies and the well-recognized needs of early disease detection, identification, and surveillance.