Distribution of human T cell lymphotropic virus type 1 (HTLV-1) subtypes in Brazil: genetic characterization of LTR and tax region

An overview of sequencing technology platforms applied to HTLV-1 studies: a systematic review

Human T-lymphotropic virus type 1 (HTLV-1) was the first human retrovirus described. The viral factors involved in the different clinical manifestations of infected individuals are still unknown, and in this sense, sequencing technologies can support viral genome studies, contributing to a better understanding of infection outcome. Currently, several sequencing technologies are available with different approaches. To understand the methodological advances in the HTLV-1 field, it is necessary to organize a synthesis by a rigorous review. This systematic literature review describes different technologies used to generate HTLV-1 sequences. The review follows the PRISMA guidelines, and the search for articles was performed in PubMed, Lilacs, Embase, and SciELO databases. From the 574 articles found in search, 62 were selected. The articles showed that, even with the emergence of new sequencing technologies, the traditional Sanger method continues to be the most commonly used methodology for generating HTLV-1 genome sequences. There are many questions that remain unanswered in the field of HTLV-1 research, and this reflects on the small number of studies using next-generation sequencing technologies, which could help address these gaps. The data compiled and analyzed here can help research on HTLV-1, assisting in the choice of sequencing technologies.

Polymorphisms in HTLV-1 Tax-responsive elements in HTLV-1-associated myelopathy/tropical spastic paraparesis patients are associated with reduced proviral load but not with disease progression

Human T-lymphotropic virus type 1 (HTLV-1) provirus expression is mainly directed by Tax-responsive elements (TRE) within the long terminal repeats (LTR). Mutations in TRE can reduce provirus expression and since a high proviral load (PVL) is a risk factor for the development of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), we evaluated polymorphisms in the 5' LTR and the association with PVL and disease progression. HTLV-1 LTR and tax sequences derived from asymptomatic carriers (AC) and HAM/TSP patients followed in a longitudinal study were analysed according to PVL and clinical severity. Individuals infected with HTLV-1 presenting the canonical TRE, considering strain ATK-1 as the consensus, displayed sustained higher PVL. By contrast, an LTR A125G mutation in TRE was associated with slightly reduced PVL only in HAM/TSP patients, although it did not influence the speed of disease progression. Moreover, this polymorphism was frequent in Latin American strains of the HTLV-1 Cosmopolitan Transcontinental subtype. Therefore, polymorphisms in the 5' TRE of HTLV-1 may represent one of the factors influencing PVL in HAM/TSP patients, especially in the Latin American population. Indeed, higher PVL in the peripheral blood has been associated with an increased inflammatory activity in the spinal cord and to a poorer prognosis in HAM/TSP. However, this event was not associated with TRE polymorphisms.

Provirus Mutations of Human T-Lymphotropic Virus 1 and 2 (HTLV-1 and HTLV-2) in HIV-1-Coinfected Individuals

Provirus mutations of human T-lymphotropic virus 1 (HTLV-1), mostly the lack of the 5' long terminal repeat (LTR) genomic region, have been described and associated with severe adult T cell leukemia/lymphoma (ATLL), non-sense point mutations with low proviral load, and Western blotting indeterminate results. Until now, no information concerning provirus mutations of HTLV-2 and its consequences, as well as those of HTLV-1/2 in HIV-coinfected individuals, had been described. Therefore, we searched for these mutations in provirus samples of 44 HIV/HTLV-1- and 25 HIV/HTLV-2-coinfected individuals. Using protocols well established for amplification and sequencing of segments of the LTR, env, and tax regions, we searched for defective type 1 particles that retain LTRs and lack internal sequences and type 2 particles that lack the 5'LTR region. In addition, using as references the prototypes ATK (HTLV-1) and Mo (HTLV-2), we searched for point mutations in the LTR and synonyms and nonsynonymous mutations and non-sense mutations in env and tax regions. Defective HTLV-1 and HTLV-2 provirus type 1 or 2 was detected in 31.8% of HIV/HTLV-1- and 32.0% of HIV/HTLV-2-coinfected individuals. Synonymous and nonsynonymous mutations were identified mostly in HTLV-2 and associated with lower levels of specific antibodies. No non-sense mutations that resulted in premature termination of Env and Tax proteins were detected. On the contrary, mutation in the stop codon of Tax2a produced a long protein characteristic of the HTLV-2c subtype. The clinical significance of these mutations in coinfected individuals remains to be defined, but they confirmed the lower sensitivity of serological and molecular diagnostic tests in HIV/HTLV-1/2 coinfections.IMPORTANCE HTLV-1 and HTLV-2 are endemic to Brazil, and they have different effects in HIV/AIDS disease progression. HIV/HTLV-1 has been described as accelerating the progression to AIDS and death, while HIV/HTLV-2 slows the progression to AIDS. Provirus mutations of HTLV-1 were implicated in severe leukemia development and in problems in the diagnosis of HTLV-1; in contrast, provirus mutations of HTLV-2 had not been confirmed and associated with problems in HTLV-2 diagnosis or disease outcome. Nevertheless, data obtained here allowed us to recognize and understand the false-negative results in serologic and molecular tests applied for HTLV-1 and HTLV-2 diagnosis. Defective proviruses, as well as synonymous and nonsynonymous mutations, were associated with the diagnosis deficiencies. Additionally, since HIV-1 and HTLV-1 infect the same cells (CD4 positive), the production of HIV-1 pseudotypes with HTLV-1 envelope glycoprotein during HIV/HTLV-1 coinfection cannot be excluded. Defective provirus of HTLV-2 and Tax2c is speculated to influence progression to AIDS.

Loop-Mediated Isothermal Amplification (LAMP) Assay for Rapid and Accurate Confirmatory Diagnosis of HTLV-1/2 Infection

Laboratory diagnosis of human T-lymphotropic viruses (HTLV) 1 and 2 infection is performed by serological screening and further confirmation with serological or molecular assays. Thus, we developed a loop-mediated isothermal nucleic acid amplification (LAMP) assay for the detection of HTLV-1/2 in blood samples. The sensitivity and accuracy of HTLV-1/2 LAMP were defined with DNA samples from individuals infected with HTLV-1 (n = 125), HTLV-2 (n = 19), and coinfected with HIV (n = 82), and compared with real-time polymerase chain reaction (qPCR) and PCR-restriction fragment length polymorphism (RFLP). The overall accuracy of HTLV-1/2 LAMP (95% CI 74.8-85.5%) was slightly superior to qPCR (95% CI 69.5-81.1%) and similar to PCR-RFLP (95% CI 79.5-89.3%). The sensitivity of LAMP was greater for HTLV-1 (95% CI 83.2-93.4%) than for HTLV-2 (95% CI 43.2-70.8%). This was also observed in qPCR and PCR-RFLP, which was associated with the commonly lower HTLV-2 proviral load. All molecular assays tested showed better results with samples from HTLV-1/2 mono-infected individuals compared with HIV-coinfected patients, who present lower CD4 T-cell counts. In conclusion, HTLV-1/2 LAMP had similar to superior performance than PCR-based assays, and therefore may represent an attractive alternative for HTLV-1/2 diagnosis due to reduced working time and costs, and the simple infrastructure needed.

Stability of the HTLV-1 glycoprotein 46 (gp46) gene in an endemic region of the Brazilian Amazon and the presence of a significant mutation (N93D) in symptomatic patients

BACKGROUND

The human T-lymphotropic virus type 1 (HTLV-1) affects 2-5 million people worldwide, and is associated with a number of degenerative and infectious diseases. The Envelope glycoproteins (gp) are highly conserved among the different HTLV-1 isolates, although nucleotide substitutions in the region that codifies these proteins may influence both the infectivity and the replication of the virus. The gp46 gene has functional domains which have been associated with the inhibition of the formation of the syncytium, cell-cell transmission, and the production of antibodies. The present study investigated the genetic stability of the gp46 gene of HTLV-1 in an endemic region of Brazilian Amazonia.

METHODS

Index case (IC - a sample of a given family group) carriers of HTLV-1 were investigated in the metropolitan region of Belém (Pará, Brazil) between January 2010 (registered retrospectively) and December 2015. The sequences that codify the gp46 were amplified by PCR, purified and sequenced (MF084788-MF084825). The gene was characterized using bioinformatics and Bayesian Inference.

RESULTS

The 40 patients analyzed had a mean age of 45.2 years and 70% presented some type of symptom, with a predominance of pain and sensitivity, dysautonomia, and motor disorders. All patients presented the aA (Transcontinental Cosmopolitan) genotype, with an extremely low mutation rate, which is characteristic of the codifying region (aA - 1.83 × 10-4 mutations per site per year). The gp46 gene had a nucleotide diversity of between 0.00% and 2.0%. Amino acid mutations were present in 66.6% of the samples of individuals with signs/symptoms or diseases associated with HTLV-1 (p = 0.0091). Of the three most frequent mutations, the previously undescribed N93D mutant was invariably associated with symptomatic cases.

CONCLUSIONS

The aA HTLV-1 subtype is predominant in the metropolitan region of Belém and presented a high degree of genetic stability in the codifying region. The rare N93D amino acid mutation may be associated with the clinical manifestations of this viral infection.

IMPORTANCE

Little is known of the phylogeny of HTLV-1 in the endemic region of Brazilian Amazonia, and few complete gene sequences are available for the gp46 glycoprotein from the local population. The nucleotide sequences of the viral gp46 gene recorded in the present study confirmed the genetic stability of the region, and pointed to a homogeneous viral group, with local geographic characteristics. Further research will be necessary to more fully understand the molecular diversity of this protein, given the potential of this codifying region as a model for an effective HTLV-1 vaccine. The identification of a rare mutation (N93D), present only in symptomatic patients, should also be investigated further as a potential clinical marker.

TRIAL REGISTRATION

ISRCTN 12345678, registered 28 September 2014.

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.

Sexual transmission of human T-cell lymphotropic virus type 1

Human T-cell lymphotropic virus type 1 (HTLV-1) is endemic in many parts of the world and is primarily transmitted through sexual intercourse or from mother to child. Sexual transmission occurs more efficiently from men to women than women to men and might be enhanced by sexually transmitted diseases that cause ulcers and result in mucosal ruptures, such as syphilis, herpes simplex type 2 (HSV-2), and chancroid. Other sexually transmitted diseases might result in the recruitment of inflammatory cells and could increase the risk of HTLV-1 acquisition and transmission. Additionally, factors that are associated with higher transmission risks include the presence of antibodies against the viral oncoprotein Tax (anti-Tax), a higher proviral load in peripheral blood lymphocytes, and increased cervicovaginal or seminal secretions. Seminal fluid has been reported to increase HTLV replication and transmission, whereas male circumcision and neutralizing antibodies might have a protective effect. Recently, free virions were discovered in plasma, which reveals a possible new mode of HTLV replication. It is unclear how this discovery might affect the routes of HTLV transmission, particularly sexual transmission, because HTLV transmission rates are significantly higher from men to women than women to men.

Molecular epidemiology and clinical features of human T cell lymphotropic virus type 1 infection in Spain

Human T cell lymphotropic virus type 1 (HTLV-1) infection in Spain is rare and mainly affects immigrants from endemic regions and native Spaniards with a prior history of sexual intercourse with persons from endemic countries. Herein, we report the main clinical and virological features of cases reported in Spain. All individuals with HTLV-1 infection recorded at the national registry since 1989 were examined. Phylogenetic analysis was performed based on the long terminal repeat (LTR) region. A total of 229 HTLV-1 cases had been reported up to December 2012. The mean age was 41 years old and 61% were female. Their country of origin was Latin America in 59%, Africa in 15%, and Spain in 20%. Transmission had occurred following sexual contact in 41%, parenteral exposure in 12%, and vertically in 9%. HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) was diagnosed in 27 cases and adult T cell leukemia/lymphoma (ATLL) in 17 subjects. HTLV-1 subtype could be obtained for 45 patients; all but one belonged to the Cosmopolitan subtype a. One Nigerian pregnant woman harbored HTLV-1 subtype b. Within the Cosmopolitan subtype a, two individuals (from Bolivia and Peru, respectively) belonged to the Japanese subgroup B, another two (from Senegal and Mauritania) to the North African subgroup D, and 39 to the Transcontinental subgroup A. Of note, one divergent HTLV-1 strain from an Ethiopian branched off from all five known Cosmopolitan subtype 1a subgroups. Divergent HTLV-1 strains have been introduced and currently circulate in Spain. The relatively large proportion of symptomatic cases (19%) suggests that HTLV-1 infection is underdiagnosed in Spain.

Molecular characterization of human T-cell lymphotropic virus type 1 full and partial genomes by Illumina massively parallel sequencing technology

BACKGROUND

Here, we report on the partial and full-length genomic (FLG) variability of HTLV-1 sequences from 90 well-characterized subjects, including 48 HTLV-1 asymptomatic carriers (ACs), 35 HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and 7 adult T-cell leukemia/lymphoma (ATLL) patients, using an Illumina paired-end protocol.

METHODS

Blood samples were collected from 90 individuals, and DNA was extracted from the PBMCs to measure the proviral load and to amplify the HTLV-1 FLG from two overlapping fragments. The amplified PCR products were subjected to deep sequencing. The sequencing data were assembled, aligned, and mapped against the HTLV-1 genome with sufficient genetic resemblance and utilized for further phylogenetic analysis.

RESULTS

A high-throughput sequencing-by-synthesis instrument was used to obtain an average of 3210- and 5200-fold coverage of the partial (n = 14) and FLG (n = 76) data from the HTLV-1 strains, respectively. The results based on the phylogenetic trees of consensus sequences from partial and FLGs revealed that 86 (95.5%) individuals were infected with the transcontinental sub-subtypes of the cosmopolitan subtype (aA) and that 4 individuals (4.5%) were infected with the Japanese sub-subtypes (aB). A comparison of the nucleotide and amino acids of the FLG between the three clinical settings yielded no correlation between the sequenced genotype and clinical outcomes. The evolutionary relationships among the HTLV sequences were inferred from nucleotide sequence, and the results are consistent with the hypothesis that there were multiple introductions of the transcontinental subtype in Brazil.

CONCLUSIONS

This study has increased the number of subtype aA full-length genomes from 8 to 81 and HTLV-1 aB from 2 to 5 sequences. The overall data confirmed that the cosmopolitan transcontinental sub-subtypes were the most prevalent in the Brazilian population. It is hoped that this valuable genomic data will add to our current understanding of the evolutionary history of this medically important virus.

Tax gene characterization of human T-lymphotropic virus type 1 strains from Brazilian HIV-coinfected patients

The tax gene of human T-lymphotropic virus type 1 (HTLV-1) diverges among isolates according to geographic regions and has been classified into two genotypes: taxA and taxB. In Brazil, taxA is the most prevalent genotype in symptomatic and asymptomatic carriers. Few studies have been conducted in HIV-infected patients. The present study characterized the tax gene (1059 bp) in 13 Brazilian HIV-1/HTLV-1-coinfected patients from the south and southeast regions. The results confirmed the transcontinental HTLV-1 subgroup A of the Cosmopolitan subtype and showed high nucleotide similarity both among Brazilian sequences and in relation to the ATK prototype (99.5% and 99.2%, respectively). Six nucleotide substitutions were highly conserved among isolates, ranging from 76.9% to 100%: C7401T, T7914C, C7920T, C7982T, G8231A, and A8367C. The presence of the Brazilian molecular signature of genotype taxA was confirmed in all of the isolates, and they clustered into two Latin American clusters, which confirms the double introduction of HTLV-1 in Brazil.

Aquaporin-4 antibodies are not related to HTLV-1 associated myelopathy

Introduction

The seroprevalence of human T-cell leukemia virus type 1 (HTLV-1) is very high among Brazilians (∼1∶200). HTLV-1 associated myelopathy or tropical spastic paraparesis (HAM/TSP) is the most common neurological complication of HTLV-1 infection. HAM/TSP can present with an acute/subacute form of longitudinally extensive myelitis, which can be confused with lesions seen in aquaporin-4 antibody (AQP4-Ab) positive neuromyelitis optica spectrum disorders (NMOSD) on MRI. Moreover, clinical attacks in patients with NMOSD have been shown to be preceded by viral infections in around 30% of cases.

Objective

To evaluate the frequency of AQP4-Ab in patients with HAM/TSP. To evaluate the frequency of HTLV-1 infection in patients with NMOSD.

Patients and Methods

23 Brazilian patients with HAM/TSP, 20 asymptomatic HTLV-1+ serostatus patients, and 34 with NMOSD were tested for AQP4-Ab using a standardized recombinant cell based assay. In addition, all patients were tested for HTLV-1 by ELISA and Western blotting.

Results

20/34 NMOSD patients were positive for AQP4-Ab but none of the HAM/TSP patients and none of the asymptomatic HTLV-1 infected individuals. Conversely, all AQP4-Ab-positive NMOSD patients were negative for HTLV-1 antibodies. One patient with HAM/TSP developed optic neuritis in addition to subacute LETM; this patient was AQP4-Ab negative as well. Patients were found to be predominantly female and of African descent both in the NMOSD and in the HAM/TSP group; Osame scale and expanded disability status scale scores did not differ significantly between the two groups.

Conclusions

Our results argue both against a role of antibodies to AQP4 in the pathogenesis of HAM/TSP and against an association between HTLV-1 infection and the development of AQP4-Ab. Moreover, the absence of HTLV-1 in all patients with NMOSD suggests that HTLV-1 is not a common trigger of acute attacks in patients with AQP4-Ab positive NMOSD in populations with high HTLV-1 seroprevalence.

Phylogenetic and similarity analysis of HTLV-1 isolates from HIV-coinfected patients from the south and southeast regions of Brazil

HTLV-1 is endemic in Brazil and HIV/HTLV-1 coinfection has been detected, mostly in the northeast region. Cosmopolitan HTLV-1a is the main subtype that circulates in Brazil. This study characterized 17 HTLV-1 isolates from HIV coinfected patients of southern (n=7) and southeastern (n=10) Brazil. HTLV-1 provirus DNA was amplified by nested PCR (env and LTR) and sequenced. Env sequences (705 bp) from 15 isolates and LTR sequences (731 bp) from 17 isolates showed 99.5% and 98.8% similarity among sequences, respectively. Comparing these sequences with ATK (HTLV-1a) and Mel5 (HTLV-1c) prototypes, similarities of 99% and 97.4%, respectively, for env and LTR with ATK, and 91.6% and 90.3% with Mel5, were detected. Phylogenetic analysis showed that all sequences belonged to the transcontinental subgroup A of the Cosmopolitan subtype, clustering in two Latin American clusters.

Seroprevalence and molecular epidemiology of HTLV-1 isolates from HIV-1 co-infected women in Feira de Santana, Bahia, Brazil

HTLV-1/HIV-1 co-infection is associated with severe clinical manifestations, marked immunodeficiency, and opportunistic pathogenic infections, as well as risk behavior. Salvador, the capital of the State of Bahia, Brazil, has the highest HTLV-1 prevalence (1.74%) found in Brazil. Few studies exist which describe this co-infection found in Salvador and its surrounding areas, much less investigate how these viruses circulate or assess the relationship between them. To describe the epidemiological and molecular features of HTLV in HIV co-infected women. To investigate the prevalence of HTLV/HIV co-infection in surrounding areas, as well as the molecular epidemiology of HTLV, a cross sectional study was carried out involving 107 women infected with HIV-1 from the STD/HIV/AIDS Reference Center located in the neighboring City of Feira de Santana. Patient samples were submitted to ELISA, and HTLV infection was confirmed using Western Blot and Polymerase Chain Reaction (PCR). Phylogenetic analysis using Neighbor-Joining (NJ) and Maximum Likelihood (ML) was performed on HTLV LTR sequences in order to gain further insights about molecular epidemiology and the origins of this virus in Bahia. Four out of five reactive samples were confirmed to be infected with HTLV-1, and one with HTLV-2. The seroprevalence of HTLV among HIV-1 co-infected women was 4.7%. Phylogenetic analysis of the LTR region from four HTLV-1 sequences showed that all isolates were clustered into the main Latin American group within the Transcontinental subgroup of the Cosmopolitan subtype. The HTLV-2 sequence was classified as the HTLV-2c subtype. It was also observed that four HTLV/HIV-1 co-infected women exhibited risk behavior with two having parenteral exposure, while another two were sex workers. This article describes the characteristics of co-infected patients. This co-infection is known to be severe and further studies should be conducted to confirm the suggestion that HTLV-1 is spreading from Salvador to surrounding areas.

Ocular lesions in HTLV-1 infected patients from Salvador, State of Bahia: the city with the highest prevalence of this infection in Brazil

In order to determine the prevalence of ocular lesions in HTLV-1 infected patients in Salvador Bahia, a transversal study was conducted on 140 HTLV-1 infected patients (90 asymptomatic and 50 tropical spastic paraparesis/HTLV-1-associated myelopathy) between June 2004 and November 2005. The ophthalmological examination included visual acuity measurement, ocular motility, biomicroscopy of the anterior and posterior chambers, intraocular pressure and evaluation of lachrymal secretion. Observation verified 4 (2.8%) out of 140 patients with uveitis (two patients had intermediate uveitis and two had pan-uveitis) and 39 (36.4%) out of 107 patients with keratoconjunctivitis sicca. The prevalence of Keratoconjunctivitis sicca was significantly higher among the TSP/HAM patients (OR age adjusted=3.64; 95%CI 1.59-8.32). Uveitis and corneal opacities were also important findings, indicating the strong need for periodic ophthalmological follow-up in all HTLV-1 subjects.

Divergent strains of human T-lymphotropic virus type 1 (HTLV-1) within the Cosmopolitan subtype in Argentina

HTLV-1 Cosmopolitan subtype Transcontinental subgroup A has been described among aboriginal communities from the northwest endemic area of Argentina. Moreover, Transcontinental subgroup A and the Japanese subgroup B were reported among blood donors from the nonendemic central region of the country. We carried out the first HTLV-1 phylogenetic study in individuals residing in Buenos Aires capital city. Phylogenetic analysis performed on the LTR region showed that all 44 new strains clustered within the Cosmopolitan subtype, with 42 (95.4%) belonging to Transcontinental subgroup A. Of them, 20 (45.5%) strains grouped in the large Latin American cluster and 4 (9.1%) in the small Latin American cluster. The majority of them belonged to individuals of nonblack origin, grouped with Amerindian strains. Three (6.8%) were closely related to South African references and two monophyletic clusters including only HIV/HTLV-1 coinfected individuals were observed. Interestingly, two (4.5%) new sequences (divergent strains) branched off from all five known Cosmopolitan subgroups in a well-supported clade. In summary, these findings show that HTLV-1 Cosmopolitan subtype Transcontinental subgroup A is infecting residents of Buenos Aires, a nonendemic area of Argentina, and confirm the introduction of divergent strains in the country.

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.

Prevalence ratio of HTLV-1 in nursing mothers from the state of Paraiba, Northeastern Brazil

The human T-cell lymphotropic virus type 1 (HTLV-1) was the first human retrovirus known as a direct causal agent of a malignant disease. The vertical route of HTLV transmission is the most frequent pathway of the virus contamination. This study was performed to determine the prevalence ratio of HTLV-1 infection among nursing women. From January 2004 to January 2005, blood samples from 1033 nursing mothers from Paraíba, Brazil were evaluated for HTLV antibodies by ELISA and HTLV-1 viral particles confirmed by polymerase chain reaction (PCR). HTLV antibodies were detected in 7 women. The overall seroprevalence ratio was 0.68% and HTLV-1 viral sequences were confirmed by PCR in 2 women. These preliminary data suggest that HTLV screening should be introduced as a mandatory test before breastfeeding and breast milk donation in Paraíba, Brazil. Additionally, counseling programs would help reduce the prevalence ratio of HTLV-1 infected individuals in this Brazilian region.

HTLV type 1 molecular study in Brazilian villages with African characteristics giving support to the post-Columbian introduction hypothesis

We performed an HTLV epidemiological study of 986 individuals from 17 villages from the same state of Salvador, the city with the highest HTLV-1 prevalence in Brazil. The HTLV-1 prevalence was 3.85%, 1.56%, and 1.23% in three villages. Phylogenetic analysis of the LTR region demonstrated that all positive samples analyzed belonged to the Transcontinental subgroup of the HTLV-1 Cosmopolitan subtype. Three of the new HTLV-1 sequences formed a well-supported clade within one of the Latin American clusters that contain a South African sequence. This Latin American cluster that segregated from the same ancestor as the other clade contained a Central African sequence. This ancestral relationship could support our previous report that suggests that this subgroup was first introduced into South Africa as a result of the migration of the Bantu population from Central Africa to Southern Africa over the past 3000 years, and afterward to Brazil during the slave trade between the sixteenth and nineteenth centuries.

Phylogeny of human T cell lymphotropic virus type 1 in Peru: a high degree of evolutionary relatedness with South African isolates

We investigated the prevalence and molecular epidemiology of human T cell lymphotropic virus type 1 in Peruvian HIV-1-positive subjects, and found a 10.1% prevalence in a consecutive series of 318 HIV-1-positive patients living in Lima. Phylogenetic analysis of the long terminal repeat of 10 patient isolates showed that all of them belonged to the HTLV-1aA (Transcontinental) subgroup. Although the majority of the Peruvian sequences included in the analysis formed a clade with other Latin American sequences, the isolates of three patients clustered significantly with South African strains. These data show a high prevalence of HTLV-1 infection in HIV-1-positive subjects living in Lima and confirm the presence in Latin America of HTLV-1 strains probably arising from South Africa.

HTLV-1a tax gene and long terminal repeat sequences from Argentinean strains reveal disagreement with tax restriction fragment length polymorphism subtyping

Sequence and cluster analysis have shown two HTLV-1a tax gene subgroups, tax A and tax B, which are related to long terminal repeat (LTR) molecular subtypes. On the basis of subgroup-specific nucleotide substitutions, restriction fragment length polymorphism (RFLP) analysis of the tax gene for subtyping HTLV-1a isolates was proposed. In this study we genetically characterized the tax gene from 63 HTLV-1-positive Argentinean individuals, including 14 patients with HTLV-1-associated myelopathy/tropical spastic paraparesis and 49 healthy HTLV-1 carriers. RFLP analysis showed that 48 samples yielded the tax A profile (76.19%) and that 15 samples contained the uncut tax B profile (23.81%). However, the LTR and tax sequence analysis revealed that in fact only 2 from the 15 samples belonged to the HTLV-1aB subgroup, presenting four tax B subgroup-specific nucleotide substitutions. The tax gene cluster analysis also confirmed that the majority of Argentinean strains belonged to the Transcontinental HTLV-1aA subgroup. These results indicate that the tax gene RFLP assay which has been proposed and used by some authors to screen HTLV-1a subgroups, is not a suitable tool to perform molecular epidemiological characterization of HTLV-1a populations.