Human T-cell lymphotropic virus type 1 gag indeterminate western blot patterns in Central Africa: relationship to Plasmodium falciparum infection

Malignancy and viral infections in Sub-Saharan Africa: A review

The burden of malignancy related to viral infection is increasing in Sub-Saharan Africa (SSA). In 2018, approximately 2 million new cancer cases worldwide were attributable to infection. Prevention or treatment of these infections could reduce cancer cases by 23% in less developed regions and about 7% in developed regions. Contemporaneous increases in longevity and changes in lifestyle have contributed to the cancer burden in SSA. African hospitals are reporting more cases of cancer related to infection (e.g., cervical cancer in women and stomach and liver cancer in men). SSA populations also have elevated underlying prevalence of viral infections compared to other regions. Of 10 infectious agents identified as carcinogenic by the International Agency for Research on Cancer, six are viruses: hepatitis B and C viruses (HBV and HCV, respectively), Epstein-Barr virus (EBV), high-risk types of human papillomavirus (HPV), Human T-cell lymphotropic virus type 1 (HTLV-1), and Kaposi's sarcoma herpesvirus (KSHV, also known as human herpesvirus type 8, HHV-8). Human immunodeficiency virus type 1 (HIV) also facilitates oncogenesis. EBV is associated with lymphomas and nasopharyngeal carcinoma; HBV and HCV are associated with hepatocellular carcinoma; KSHV causes Kaposi's sarcoma; HTLV-1 causes T-cell leukemia and lymphoma; HPV causes carcinoma of the oropharynx and anogenital squamous cell cancer. HIV-1, for which SSA has the greatest global burden, has been linked to increasing risk of malignancy through immunologic dysregulation and clonal hematopoiesis. Public health approaches to prevent infection, such as vaccination, safer injection techniques, screening of blood products, antimicrobial treatments and safer sexual practices could reduce the burden of cancer in Africa. In SSA, inequalities in access to cancer screening and treatment are exacerbated by the perception of cancer as taboo. National level cancer registries, new screening strategies for detection of viral infection and public health messaging should be prioritized in SSA's battle against malignancy. In this review, we discuss the impact of carcinogenic viruses in SSA with a focus on regional epidemiology.

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.

Development and Validation of a Rapid Screening Test for HTLV-I IgG Antibodies

Initial diagnosis of human T cell lymphotropic virus (HTLV) infections is mainly based by detecting antibodies in plasma or serum using laboratory-based methods. The aim of this study was to develop and evaluate a rapid screening test for HTLV-I antibodies. Our rapid screening test uses HTLV-I p24 antigen conjugated to gold nanoparticles and an anti-human IgG antibody immobilized to a nitrocellulose strip to detect human HTLV-I p24-specific IgG antibodies via immunochromatography. Performance of the rapid screening test for HTLV-I was conducted on a total of 118 serum specimens collected in Salvador, Bahia, the epicenter for HTLV-1 infection in Brazil. Using a Western blot test as the comparator, 55 serum specimens were HTLV-I positive, 5 were HTLV-I and HTLV-II positive, and 58 were negative. The sensitivity of the rapid screening test for HTLV-1 was 96.7% and the specificity was 100%. The rapid screening test did not show cross-reaction with serum specimens from individuals with potentially interfering infections including those caused by HTLV-II, HIV-I, HIV-II, hepatitis A virus, hepatitis B virus, hepatitis C virus, herpes simplex virus, Epstein-Barr virus, SARS-CoV-2, Chlamydia trachomatis, Neisseria gonorrhoeae, Treponema pallidum, Toxoplasma gondii, and Plasmodium falciparum. The rapid screening test also did not show cross-reaction with potentially interfering substances. Strategies for HTLV diagnosis in non- and high-endemic areas can be improved with low-cost, rapid screening tests.

Bioprospection and Selection of Peptides by Phage Display as Novel Epitope-Based Diagnostic Probes for Serological Detection of HTLV-1 and Use in Future Vaccines

Human T-lymphotropic virus 1 (HTLV-1) is endemic worldwide and the infection results in severe diseases, including Adult T-cell Leukemia (ATL) and HTLV-1 associated myelopathy (HAM). There are some limitations of employing the present commercial serological assays for both diagnostic and epidemiological purposes in different geographical areas of the Brazil, such as the Amazon Region. Currently, methods for diagnosis are usually expensive to adapt for routine use. The aim of this work was to identify and characterize specific ligands to IgG that mimic HTLV-1 epitopes through the Phage Display technique, which could be used for diagnosis and as future vaccine candidates. Initially, IgG from 10 patients with HTLV-1 and 20 negative controls were covalently coupled to protein G-magnetic beads. After biopanning, genetic sequencing, bioinformatics analysis and Phage-ELISA were performed. The technique allowed the identification of 4 clones with HTLV-1 mimetic peptides, three aligned with gp46, A6 (SPYW), B6 (SQLP) and D7 (PLIL), and one with the protease and Tax, A8 (SPPR). Clones A6 and B6 showed higher values of accessibility, antigenicity and hydrophilicity. The reactivity of the clones evaluated by the Receiver Operating Characteristic (ROC) curve showed that the B6 clone had the highest Area Under Curve (0.83) and sensitivity and specificity values (both were 77.27 %; p < 0.001). The study showed that the Phage Display technique is effective for the identification of HTLV-1-related peptides. Clone B6 indicated to be a good marker for bioprospecting diagnostic test for HTLV-1 infection and could be used as a possible vaccine candidate for future studies.

Clinical and Public Health Implications of Human T-Lymphotropic Virus Type 1 Infection

Human T-lymphotropic virus type 1 (HTLV-1) is estimated to affect 5 to 10 million people globally and can cause severe and potentially fatal disease, including adult T-cell leukemia/lymphoma (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The burden of HTLV-1 infection appears to be geographically concentrated, with high prevalence in discrete regions and populations. While most high-income countries have introduced HTLV-1 screening of blood donations, few other public health measures have been implemented to prevent infection or its consequences. Recent advocacy from concerned researchers, clinicians, and community members has emphasized the potential for improved prevention and management of HTLV-1 infection. Despite all that has been learned in the 4 decades following the discovery of HTLV-1, gaps in knowledge across clinical and public health aspects persist, impeding optimal control and prevention, as well as the development of policies and guidelines. Awareness of HTLV-1 among health care providers, communities, and affected individuals remains limited, even in countries of endemicity. This review provides a comprehensive overview on HTLV-1 epidemiology and on clinical and public health and highlights key areas for further research and collaboration to advance the health of people with and at risk of HTLV-1 infection.

Extracellular vesicles from HTLV-1 infected cells modulate target cells and viral spread

BACKGROUND

The Human T-cell Lymphotropic Virus Type-1 (HTLV-1) is a blood-borne pathogen and etiological agent of Adult T-cell Leukemia/Lymphoma (ATLL) and HTLV-1 Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP). HTLV-1 has currently infected up to 10 million globally with highly endemic areas in Japan, Africa, the Caribbean and South America. We have previously shown that Extracellular Vesicles (EVs) enhance HTLV-1 transmission by promoting cell-cell contact.

RESULTS

Here, we separated EVs into subpopulations using differential ultracentrifugation (DUC) at speeds of 2 k (2000×g), 10 k (10,000×g), and 100 k (100,000×g) from infected cell supernatants. Proteomic analysis revealed that EVs contain the highest viral/host protein abundance in the 2 k subpopulation (2 k > 10 k > 100 k). The 2 k and 10 k populations contained viral proteins (i.e., p19 and Tax), and autophagy proteins (i.e., LC3 and p62) suggesting presence of autophagosomes as well as core histones. Interestingly, the use of 2 k EVs in an angiogenesis assay (mesenchymal stem cells + endothelial cells) caused deterioration of vascular-like-tubules. Cells commonly associated with the neurovascular unit (i.e., astrocytes, neurons, and macrophages) in the blood-brain barrier (BBB) showed that HTLV-1 EVs may induce expression of cytokines involved in migration (i.e., IL-8; 100 k > 2 k > 10 k) from astrocytes and monocyte-derived macrophages (i.e., IL-8; 2 k > 10 k). Finally, we found that EVs were able to promote cell-cell contact and viral transmission in monocytic cell-derived dendritic cell. The EVs from both 2 k and 10 k increased HTLV-1 spread in a humanized mouse model, as evidenced by an increase in proviral DNA and RNA in the Blood, Lymph Node, and Spleen.

CONCLUSIONS

Altogether, these data suggest that various EV subpopulations induce cytokine expression, tissue damage, and viral spread.

Human T-cell lymphotropic virus type 1 transmission dynamics in rural villages in the Democratic Republic of the Congo with high nonhuman primate exposure

The Democratic Republic of the Congo (DRC) has a history of nonhuman primate (NHP) consumption and exposure to simian retroviruses yet little is known about the extent of zoonotic simian retroviral infections in DRC. We examined the prevalence of human T-lymphotropic viruses (HTLV), a retrovirus group of simian origin, in a large population of persons with frequent NHP exposures and a history of simian foamy virus infection. We screened plasma from 3,051 persons living in rural villages in central DRC using HTLV EIA and western blot (WB). PCR amplification of HTLV tax and LTR sequences from buffy coat DNA was used to confirm infection and to measure proviral loads (pVLs). We used phylogenetic analyses of LTR sequences to infer evolutionary histories and potential transmission clusters. Questionnaire data was analyzed in conjunction with serological and molecular data. A relatively high proportion of the study population (5.4%, n = 165) were WB seropositive: 128 HTLV-1-like, 3 HTLV-2-like, and 34 HTLV-positive but untypeable profiles. 85 persons had HTLV indeterminate WB profiles. HTLV seroreactivity was higher in females, wives, heads of households, and increased with age. HTLV-1 LTR sequences from 109 persons clustered strongly with HTLV-1 and STLV-1 subtype B from humans and simians from DRC, with most sequences more closely related to STLV-1 from Allenopithecus nigroviridis (Allen's swamp monkey). While 18 potential transmission clusters were identified, most were in different households, villages, and health zones. Three HTLV-1-infected persons were co-infected with simian foamy virus. The mean and median percentage of HTLV-1 pVLs were 5.72% and 1.53%, respectively, but were not associated with age, NHP exposure, village, or gender. We document high HTLV prevalence in DRC likely originating from STLV-1. We demonstrate regional spread of HTLV-1 in DRC with pVLs reported to be associated with HTLV disease, supporting local and national public health measures to prevent spread and morbidity.

A Strategy for Screening and Confirmation of HTLV-1/2 Infections in Low-Endemic Areas

Serological tests have been widely used for detecting human T-cell lymphotropic virus type 1/2 (HTLV-1/2) antibodies in the endemic areas, but their performance in low-risk populations is rarely reported. The aim of this study was to evaluate the performance of four HTLV-1/2 screening assays and to discuss a strategy for diagnosis of HTLV-1/2 infection in a non-endemic area. At the present study, 1546 specimens repeatedly reactive (RR) by one screening ELISA were collected from blood centers/banks from January 2016 to April 2019. Avioq-ELISA, Murex-ELISA, Roche-ECLIA and Fujirebio-CLIA were independently performed on each plasma sample and compared to WB and LIA confirmatory tests. Positive or indeterminate specimens with blood available were quantified by qPCR. The results showed that 48 samples were finally confirmed as HTLV-1 positive, 13 were HTLV positive, 151 were indeterminate, and 387 were negative. All the WB-positive samples were also LIA-positive. Roche-ECLIA showed the highest sensitivity that was able to detect 91.8% positives and combined with the Murex-ELISA would significantly increase the positive detection rate (98.4%). In addition, LIA yield more indeterminate and HTLV-untyped results than WB (152 vs. 27), but was able to resolve infection status of some individuals with an indeterminate WB. Besides, 3 WB indeterminate and 1 LIA-untyped samples were confirmed as HTLV-1 positive by qPCR. Based on these findings, we put forward a proper test strategy for HTLV-1/2 diagnosis in low-prevalence areas. If possible, the Roche-ECLIA with the highest sensitivity is suggested as a second screening assay in primary labs. If not, all RR specimens are recommended to be firstly retested by Roche-ECLIA and Murex-ELISA in the reference lab. Secondly, samples reactive to any one of the two tests were quantified by qPCR, and then the NAT-negatives were furtherly submitted to LIA for confirmation. Thereby, the cost can be reduced and the diagnostic accuracy would be improved.

Nanotechnology based strategies for HIV-1 and HTLV-1 retroviruses gene detection

Early detection of retroviruses including human T-cell lymphotropic virus and human immunodeficiency virus in the human body is indispensable to prevent retroviral infection propagation and improve clinical treatment. Until now, diverse techniques have been employed for the early detection of viruses. Traditional methods are time-consuming, resource-intensive, and laborious performing. Therefore, designing and constructing a selective and sensitive diagnosis system to detect serious diseases is highly demanded. Genetic detection with high sensitivity has striking significance for the early detection and remedy of disparate pathogenic diseases. The nucleic acid biosensors are based on the identification of specific DNA sequences in biological samples. Nanotechnology has an important impact on the development of sensitive biosensors. Different kinds of nanomaterials include nanoparticles, nanoclusters, quantum dots, carbon nanotubes, nanocomposites, etc., with different properties have been used to improve the performance of biosensors. Recently, DNA nanobiosensors are developed to provide simple, fast, selective, low-cost, and sensitive detection of infectious diseases. In this paper, the research progresses of nano genosensors for the detection of HIV-1 and HTLV-1 viruses, based on electrochemical, optical, and photoelectrochemical platforms are overviewed.

Line Immunoassay for Confirmation and Discrimination of Human T-Cell Lymphotropic Virus Infections in Inconclusive Western Blot Serum Samples from Brazil

Difficulties in confirming and discriminating human T-cell lymphotropic virus type 1 (HTLV-1) and HTLV-2 infections by serological Western blot (WB) assays (HTLV Blot 2.4; MP Biomedicals) have been reported in Brazil, mainly in HIV/AIDS patients, with a large number of WB-indeterminate and WB-positive but HTLV-untypeable results. Nonetheless, a line immunoassay (LIA) (INNO-LIA HTLV-I/II; Fujirebio) provided enhanced specificity and sensitivity for confirming HTLV-1/2 infections.

Difficulties in confirming and discriminating human T-cell lymphotropic virus type 1 (HTLV-1) and HTLV-2 infections by serological Western blot (WB) assays (HTLV Blot 2.4; MP Biomedicals) have been reported in Brazil, mainly in HIV/AIDS patients, with a large number of WB-indeterminate and WB-positive but HTLV-untypeable results. Nonetheless, a line immunoassay (LIA) (INNO-LIA HTLV-I/II; Fujirebio) provided enhanced specificity and sensitivity for confirming HTLV-1/2 infections. To add information concerning the improved ability of the LIA in relation to WB when applied to samples of individuals from different risk groups from Brazil, we performed the present study. Three groups were analyzed: group 1 (G1), with 62 samples from HIV/AIDS patients from São Paulo, SP (48 WB indeterminate and 14 HTLV untypeable); group 2 (G2), with 24 samples from patients with hepatitis B or hepatitis C from São Paulo (21 WB indeterminate and 3 HTLV untypeable; 17 HIV seropositive); and group 3 (G3), with 25 samples from an HTLV outpatient clinic in Salvador, Bahia (16 WB indeterminate and 9 HTLV untypeable; all HIV seronegative). Overall, the LIA confirmed HTLV-1/2 infection (HTLV-1, HTLV-2, or HTLV) in 66.1% (G1), 83.3% (G2), and 76.0% (G3) of samples. Interestingly, the majority of WB-indeterminate results were confirmed by the LIA as being HTLV-2 positive in G1 and G2 but not in G3, in which the samples were defined as being HTLV-1 or HTLV positive. These results agree with the virus types that circulate in such patients of different regions in Brazil and emphasize that the LIA is the best serological test for confirming HTLV-1 and HTLV-2 infections, independently of being applied in HTLV-monoinfected or HTLV-coinfected individuals.

Blood transfusion safety in sub-Saharan Africa: A literature review of changes and challenges in the 21st century

BACKGROUND

Access to a safe, adequate blood supply has proven challenging in sub-Saharan Africa, where systemic deficiencies spanning policy, collections, testing, and posttransfusion surveillance have long been recognized. Progress in transfusion safety in the early 2000s was in large part due to intervention by the World Health Organization and other foreign governmental bodies, coupled with an influx of external funding.

STUDY DESIGN AND METHODS

A review of the literature was conducted to identify articles pertaining to blood safety in sub-Saharan Africa from January 2009 to March 2018. The search was directed toward addressing the major elements of the blood safety chain, in the countries comprising the World Health Organization African region. Of 1380 articles, 531 met inclusion criteria and 136 articles were reviewed.

RESULTS

External support has been associated with increased recruitment of voluntary donors and expanded testing for the major transfusion-transmitted infections (TTIs). However, the rates of TTIs among donors remain high. Regional education and training initiatives have been implemented, and a tiered accreditation process has been adopted. However, a general decline in funding for transfusion safety (2009 onwards) has strained the ability to maintain or improve transfusion-related services. Critical areas of need include data collection and dissemination, epidemiological surveillance for TTIs, donor recruitment, quality assurance and oversight (notably laboratory testing), and hemovigilance.

CONCLUSION

Diminishing external support has been challenging for regional transfusion services. Critical areas of deficiency in regional blood transfusion safety remain. Nonetheless, substantive gains in education, training, and accreditation suggest durable gains in regional capacity.

A genosensor for detection of HTLV-I based on photoluminescence quenching of fluorescent carbon dots in presence of iron magnetic nanoparticle-capped Au

Carbon dots and Fe₃O₄@Au were synthesized to develop a new biosensor to detect DNA target. We investigated the photoluminescence property of carbon dots (CDs) in the presence of Fe₃O₄-capped Au (Fe₃O₄@Au). Firstly, we designed two dedicated probes for unique long sequence region of human T-lymphotropic virus type 1 genome. One of the probes was covalently bound to the CDs. In the absence of target, CDs-probe was adsorbed on the surface of Fe₃O₄@Au through two possible mechanisms, leading to quenching the fluorescence emission of CDs. The fluorescence emission of CDs was recovered in the presence of target since double-stranded DNA cannot adsorb on the Fe₃O₄@Au. Also, Fe₃O₄@Au can adsorb the unhybridized oligonucleotides and improves the accuracy of detection. The specificity of the proposed biosensor was confirmed by BLAST search and assessed by exposing the biosensor to other virus targets. The experimental detection limit of the biosensor was below 10 nM with linear range from 10 to 320 nM.

Risk factors for HTLV-1 infection in Central Africa: A rural population-based survey in Gabon

BACKGROUND

Human T-Lymphotropic Virus type 1 (HTLV-1) is a human oncoretrovirus that infects at least 5 to 10 million people worldwide and is associated with severe diseases. Africa appears as the largest HTLV-1 endemic area. However, the risk factors for the acquisition of HTLV-1 remain poorly understood in Central Africa.

METHODS

We conducted an epidemiological survey between 2013 and 2017, in rural areas of 6 provinces of Gabon, in a rainforest environment. Epidemiological data were obtained and blood samples were collected after informed consent. Plasma were screened for HTLV-1 antibodies by ELISA and the positive samples were then tested by Western blot (WB). Genomic DNA derived from buffy-coat was subjected to two semi-nested PCRs amplifying either HTLV-1 env gene or LTR region fragments.

RESULTS

We recruited 2,060 individuals over 15 years old, including 1,205 men and 855 women (mean age: 49 years). Of these, 299 were found to be ELISA HTLV-1/2 seropositive. According to WB criteria, 136 were HTLV-1 (6.6%), 25 HTLV-1/2 (1.2%) and 9 HTLV seroreactive (0.4%). PCR results showed that 146 individuals were positive for at least one PCR: 104 for the env gene and 131 for the LTR region. Based on both serological and molecular results, 179 individuals were considered infected with HTLV-1, leading to an overall prevalence of 8.7%. The distribution of HTLV-1 infection was heterogeneous across the country. Based on multivariable analyses, female gender, increasing age, ethnicity (Pygmy) and multiple hospitalizations (more than 5 times) were found to be independent risk factors for HTLV-1 infection. Furthermore, a non-human primate bite appeared to be marginally associated with a higher risk of HTLV-1 infection.

CONCLUSION

Based on state-of-the-art serological and molecular methods, we have demonstrated that rural adult populations in Gabon are highly endemic for HTLV-1. Our results regarding risk factors should lead to public health actions aiming to reduce HTLV-1 transmission.

Proviral Features of Human T Cell Leukemia Virus Type 1 in Carriers with Indeterminate Western Blot Analysis Results

Western blotting (WB) for human T cell leukemia virus type 1 (HTLV-1) is performed to confirm anti-HTLV-1 antibodies detected at the initial screening of blood donors and in pregnant women. However, the frequent occurrence of indeterminate results is a problem with this test. We therefore assessed the cause of indeterminate WB results by analyzing HTLV-1 provirus genomic sequences. A quantitative PCR assay measuring HTLV-1 provirus in WB-indeterminate samples revealed that the median proviral load was approximately 100-fold lower than that of WB-positive samples (0.01 versus 0.71 copy/100 cells). Phylogenic analysis of the complete HTLV-1 genomes of WB-indeterminate samples did not identify any specific phylogenetic groups. When we analyzed the nucleotide changes in 19 HTLV-1 isolates from WB-indeterminate samples, we identified 135 single nucleotide substitutions, composed of four types, G to A (29%), C to T (19%), T to C (19%), and A to G (16%). In the most frequent G-to-A substitution, 64% occurred at GG dinucleotides, indicating that APOBEC3G is responsible for mutagenesis in WB-indeterminate samples. Moreover, interestingly, five WB-indeterminate isolates had nonsense mutations in Pol and/or Tax, Env, p12, and p30. These findings suggest that WB-indeterminate carriers have low production of viral antigens because of a combination of a low proviral load and mutations in the provirus, which may interfere with host recognition of HTLV-1 antigens.

A Novel Human T-lymphotropic Virus Type 1c Molecular Variant in an Indigenous Individual from New Caledonia, Melanesia

BACKGROUND

Human T-Lymphotropic Virus type 1 (HTLV-1) is endemic among people of Melanesian descent in Papua New Guinea, Solomon Islands and Vanuatu, and in Indigenous populations from Central Australia. Molecular studies revealed that these Australo-Melanesian strains constitute the highly divergent HTLV-1c subtype. New Caledonia is a French overseas territory located in the Southwest Pacific Ocean. HTLV-1 situation is poorly documented in New Caledonia and the molecular epidemiology of HTLV-1 infection remains unknown.

OBJECTIVES

Studying 500 older adults Melanesian natives from New Caledonia, we aim to evaluate the HTLV-1 seroprevalence and to molecularly characterize HTLV-1 proviral strains.

STUDY DESIGN

Plasma from 262 men and 238 females (age range: 60-96 years old, mean age: 70.5) were screened for anti-HTLV-1 antibodies by particle agglutination (PA) and indirect immunofluorescence assay (IFA). Serological confirmation was obtained using Western blot assay. DNAs were extracted from peripheral blood buffy coat of HTLV-1 seropositive individuals, and subjected to four series of PCR (LTR-gag; pro-pol; pol-env and tax-LTR). Primers were designed from highly common conserved regions of the major HTLV-1 subtypes to characterize the entire HTLV-1 proviral genome.

RESULTS

Among 500 samples, 3 were PA and IFA positive. The overall seroprevalence was 0.6%. The DNA sample from 1 New Caledonian woman (NCP201) was found positive by PCR and the complete HTLV-1 proviral genome (9,033-bp) was obtained. The full-length HTLV-1 genomic sequence from a native woman from Vanuatu (EM5), obtained in the frame of our previous studies, was also characterized. Both sequences belonged to the HTLV-1c Australo-Melanesian subtype. The NCP201 strain exhibited 0.3% nucleotide divergence with the EM5 strain from Vanuatu. Furthermore, divergence reached 1.1% to 2.9% with the Solomon and Australian sequences respectively. Phylogenetic analyses on a 522-bp-long fragment of the gp21-env gene showed the existence of two major clades. The first is composed of strains from Papua New Guinea; the second includes strains from all neighboring archipelagos (Solomon, Vanuatu, New Caledonia), and Australia. Interestingly, this second clade itself is divided into two sub-clades: strains from Australia on one hand, and strains from Solomon Islands, Vanuatu and New Caledonia on the other hand.

CONCLUSIONS

The HTLV-1 seroprevalence (0.6%) in the studied adult population from New Caledonia appears to be low. This seroprevalence is quite similar to the situation observed in Vanuatu and Solomon Islands. However it is very different to the one encountered in Central Australia. Taken together, these results demonstrated that Australo-Melanesia is endemic for HTLV-1 infection with a high diversity of HTLV-1c strains and a clear geographic clustering according to the island of origin of HTLV-1 infected persons.

Serological and Molecular Methods to Study Epidemiological Aspects of Human T-Cell Lymphotropic Virus Type 1 Infection

We estimated that at least 5-10 million individuals are infected with HTLV-1. Importantly, this number is based on the study of nearly 1.5 billion people living in known human T-cell lymphotropic virus type 1 (HTLV-1) endemic areas, for which reliable epidemiological data are available. However, for some highly populated regions including India, the Maghreb, East Africa, and some regions of China, no consistent data are yet available which prevents a more accurate estimation. Thus, the number of HTLV-1 infected people in the world is probably much higher. The prevalence of HTLV-1 prevalence varies depending on age, sex, and economic level in most HTLV-1 endemic areas. HTLV-1 seroprevalence gradually increases with age, especially in women. HTLV-1 has a simian origin and was originally acquired by humans through interspecies transmission from STLV-1 infected monkeys in the Old World. Three main modes of HTLV-1 transmission have been described; (1) from mother-to-child after prolonged breast-feeding lasting more than six months, (2) through sexual intercourse, which mainly, but not exclusively, occurs from male to female and lastly, (3) from contaminated blood products, which contain HTLV-1 infected lymphocytes. In specific areas, such as Central Africa, zoonotic transmission from STLV-1 infected monkeys to humans is still ongoing.The diagnostic methods used to study the epidemiological aspects of HTLV-1 infection mainly consist of serological assays for the detection of antibodies specifically directed against different HTLV-1 antigens. Screening tests are usually based on enzyme-linked immunoabsorbent assay (ELISA), chemiluminescence enzyme-linked immunoassay (CLEIA) or particle agglutination (PA). Confirmatory tests include mostly Western blots (WB)s or innogenetics line immunoassay (INNO-LIA™) and to a lesser extent immunofluorescence assay (IFA). The search for integrated provirus in the DNA from peripheral blood cells can be performed by qualitative and/or quantitative polymerase chain reaction (qPCR). qPCR is widely used in most diagnostic laboratories and quantification of proviral DNA is useful for the diagnosis and follow-up of HTLV-1 associated diseases such as adult T-cell leukemia (ATL) and tropical spastic paraparesis/HTLV-1 associated myelopathy (TSP/HAM). PCR also provides amplicons for further sequence analysis to determine the HTLV-1 genotype present in the infected person. The use of new generation sequencing methodologies to molecularly characterize full and/or partial HTLV-1 genomic regions is increasing. HTLV-1 genotyping generates valuable molecular epidemiological data to better understand the evolutionary history of this virus.

Seroprevalence of HTLV-1 and HTLV-2 amongst mothers and children in Malawi within the context of a systematic review and meta-analysis of HTLV seroprevalence in Africa

OBJECTIVES

Human T-lymphotropic virus (HTLV)-1 causes T-cell leukaemia and myelopathy. Together with HTLV-2, it is endemic in some African nations. Seroprevalence data from Malawi are scarce, with no reports on associated disease incidence. HTLV seroprevalence and type were tested in 418 healthy mothers from Malawi. In addition, we tested the sera of 534 children to investigate mother-to-child transmission. To provide context, we conducted a systematic review and meta-analysis of HTLV seroprevalence in African women and children.

METHODS

Stored samples from a previous childhood cancer and BBV study were analysed. ELISA was used for HTLV screening followed by immunoblot for confirmation and typing. Standard methods were used for the systematic review.

RESULTS

HTLV seroprevalence was 2.6% (11/418) in mothers and 2.2% (12/534) in children. Three mothers carried HTLV-1 alone, seven had HTLV-2 and one was dually infected. Three children carried HTLV-1 alone, seven had HTLV-2 and two were dually infected. Only two corresponding mothers of the 12 HTLV-positive children were HTLV positive. The systematic review included 66 studies of women and 13 of children conducted in 25 African countries. Seroprevalence of HTLV-1 varied from 0 to 17% and of HTLV-2 from 0 to 4%.

CONCLUSIONS

In contrast to findings from other studies in Africa, the seroprevalence of HTLV-2 was higher than that of HTLV-1 in Malawi and one of the highest for the African region. The lack of mother-child concordance suggests alternative sources of infection among children. Our data and analyses contribute to HTLV prevalence mapping in Africa.

Infection with human T-lymphotropic virus types-1 and -2 (HTLV-1 and -2): Implications for blood transfusion safety

Many countries currently perform antibody screening for HTLV-1 infection in blood donors, and this intervention is likely cost-effective in preventing HTLV-1 related diseases in high prevalence countries. However, a number of high-income countries with low prevalence of HTLV-1 infection also perform universal HTLV-1 screening and debate has arisen regarding the cost-effectiveness of these strategies. Filter-based leukoreduction is likely to substantially reduce HTLV-1 transmission by removing infected lymphocytes, but actual laboratory data on its efficacy is currently lacking. Similarly, cost-effectiveness research on HTLV-1 prevention strategies is limited by poor data on prevalence, transmission efficacy and the cost of treating HTLV1 diseases.

Low Proviral Load is Associated with Indeterminate Western Blot Patterns in Human T-Cell Lymphotropic Virus Type 1 Infected Individuals: Could Punctual Mutations be Related?

BACKGROUND

indeterminate Western blot (WB) patterns are a major concern for diagnosis of human T-cell lymphotropic virus type 1 (HTLV-1) infection, even in non-endemic areas.

OBJECTIVES

(a) to define the prevalence of indeterminate WB among different populations from Argentina; (b) to evaluate if low proviral load (PVL) is associated with indeterminate WB profiles; and (c) to describe mutations in LTR and tax sequence of these cases.

RESULTS

Among 2031 samples, 294 were reactive by screening. Of them, 48 (16.3%) were WB indeterminate and of those 15 (31.3%) were PCR+. Quantitative real-time PCR (qPCR) was performed to 52 HTLV-1+ samples, classified as Group 1 (G1): 25 WB+ samples from individuals with pathologies; Group 2 (G2): 18 WB+ samples from asymptomatic carriers (AC); and Group 3 (G3): 9 seroindeterminate samples from AC. Median PVL was 4.78, 2.38, and 0.15 HTLV-1 copies/100 PBMCs, respectively; a significant difference (p=0.003) was observed. Age and sex were associated with PVL in G1 and G2, respectively. Mutations in the distal and central regions of Tax Responsive Elements (TRE) 1 and 2 of G3 were observed, though not associated with PVL.The 8403A>G mutation of the distal region, previously related to high PVL, was absent in G3 but present in 50% of WB+ samples (p = 0.03).

CONCLUSIONS

indeterminate WB results confirmed later as HTLV-1 positive may be associated with low PVL levels. Mutations in LTR and tax are described; their functional relevance remains to be determined.

Infection with human retroviruses other than HIV-1: HIV-2, HTLV-1, HTLV-2, HTLV-3 and HTLV-4

HIV-1 is the most prevalent retrovirus, with over 30 million people infected worldwide. Nevertheless, infection caused by other human retroviruses like HIV-2, HTLV-1, HTLV-2, HTLV-3 and HTLV-4 is gaining importance. Initially confined to specific geographical areas, HIV-2, HTLV-1 and HTLV-2 are becoming a major concern in non-endemic countries due to international migration flows. Clinical manifestations of retroviruses range from asymptomatic carriers to life-threatening conditions, such as AIDS in HIV-2 infection or adult T-cell lymphoma/leukemia or tropical spastic paraparesis in HTLV-1 infection. HIV-2 is naturally resistant to some antiretrovirals frequently used to treat HIV-1 infection, but it does have effective antiretroviral therapy options. Unfortunately, HTLV still has limited therapeutic options. In this article, we will review the epidemiological, clinical, diagnostic, pathogenic and therapeutic aspects of infections caused by these human retroviruses.

Screening for hepatitis C virus infection in a high prevalence country by an antigen/antibody combination assay versus a rapid test

In low-income-countries, screening for hepatitis C virus (HCV) infection is often based on rapid tests (RT). Their lower sensitivity compared to enzyme immunoassay (EIA) suggests that newer HCV Antigen/Antibody (Ag/Ab) combination assays might have a role in such countries. To test this idea, 1998 blood donors were tested at the University Teaching Hospital blood bank in Yaoundé, Cameroon simultaneously with a RT (HCV rapid test, Human Diagnostics, Berlin, Germany) according to standard practice (S1) and with an Ag/Ab assay (Monolisa HCV Ag/Ab Ultra, Biorad, France) (S2). All discordant, borderline and reactive samples were submitted to confirmatory testing by immunoblot and/or HCV-RNA. Of the 86 (4.3%) samples positive with one or both strategies, 29 were confirmed negative, 37 positive and 20 were false positive or resolved infection. There was a significant difference in test sensitivity (p=0.01) between S1 (70.3%) and S2 (91.9%) but not in test specificity (99.4% and 98.6%, respectively). The benefit of the Ag/Ab assay in the detection of recent HCV seronegative infections could not be evaluated since no Antigen-only donations were identified. However, better Ag/Ab test sensitivity compared to RT supports the implementation of these newer immunoassays for HCV screening in the African blood bank setting.

Association of inconclusive sera for human immunodeficiency virus infection with malaria and Epstein-Barr virus infection in Central Africa

Among 464 sera from adults in Cameroon, 56 (12.1%) gave inconclusive HIV serology. All were negative for HIV-1 DNA; 44.6% (n = 25) were significantly associated with Plasmodium (42.8%) or Epstein-Barr virus (EBV) (17.8%) infections. In Central Africa, sera giving inconclusive results for HIV are frequently associated with malaria, EBV infection, or both.

Human T-cell lymphotropic virus type 1 subtype C molecular variants among indigenous australians: new insights into the molecular epidemiology of HTLV-1 in Australo-Melanesia

Background

HTLV-1 infection is endemic among people of Melanesian descent in Papua New Guinea, the Solomon Islands and Vanuatu. Molecular studies reveal that these Melanesian strains belong to the highly divergent HTLV-1c subtype. In Australia, HTLV-1 is also endemic among the Indigenous people of central Australia; however, the molecular epidemiology of HTLV-1 infection in this population remains poorly documented.

Findings

Studying a series of 23 HTLV-1 strains from Indigenous residents of central Australia, we analyzed coding (gag, pol, env, tax) and non-coding (LTR) genomic proviral regions. Four complete HTLV-1 proviral sequences were also characterized. Phylogenetic analyses implemented with both Neighbor-Joining and Maximum Likelihood methods revealed that all proviral strains belong to the HTLV-1c subtype with a high genetic diversity, which varied with the geographic origin of the infected individuals. Two distinct Australians clades were found, the first including strains derived from most patients whose origins are in the North, and the second comprising a majority of those from the South of central Australia. Time divergence estimation suggests that the speciation of these two Australian clades probably occurred 9,120 years ago (38,000–4,500).

Conclusions

The HTLV-1c subtype is endemic to central Australia where the Indigenous population is infected with diverse subtype c variants. At least two Australian clades exist, which cluster according to the geographic origin of the human hosts. These molecular variants are probably of very ancient origin. Further studies could provide new insights into the evolution and modes of dissemination of these retrovirus variants and the associated ancient migration events through which early human settlement of Australia and Melanesia was achieved.

The Human T-lymphotropic virus type 1 (HTLV-1) infects at least 5–10 million persons worldwide. In Oceania, previous studies have shown that HTLV-1 is present in a few ancient populations from remote areas of Papua New Guinea, the Solomon Islands, the Vanuatu archipelago and central Australia. The latter comprise one of the most socio-economically disadvantaged groups within any developed country. Characterization of the few available HTLV-1 viruses from Oceania indicates that these belong to a specific HTLV-1 genotype, the Australo-Melanesian c-subtype. In this study, we provide details for 23 HTLV-1 viruses derived from the Indigenous population of central Australia, a vast remote area of 1,000,000 km². We reveal considerable genetic diversity of HTLV-1c subtype viruses and the existence of two HTLV-1c clades within which a high degree of genetic diversity was also apparent. These newly described HTLV-1c clades clustered according to the geographic origin of their human hosts. Indigenous Australians from the North of central Australia harbor HTLV-1c subtype viruses that are distinct from those of individuals from regions to the South. These data suggest that HTLV-1 was probably introduced to Australia during ancient migration events and was then confined to isolated Indigenous communities in central Australia.

Epidemiological Aspects and World Distribution of HTLV-1 Infection

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

A new and frequent human T-cell leukemia virus indeterminate Western blot pattern: epidemiological determinants and PCR results in central African inhabitants

Human T-cell leukemia virus (HTLV) indeterminate Western blot (WB) serological patterns are frequently observed in plasma/serum from persons living in intertropical areas. In the framework of ongoing projects on HTLV-1/2 and related viruses in Central Africa, we systematically analyzed plasma from villagers living in South Cameroon by WB. The group included 1,968 individuals (mean age, 44 years; age range, 5 to 90 years; 978 women/990 men), both Bantus (1,165) and Pygmies (803). Plasma samples were tested by WB analysis (MPD HTLV Blot 2.4) and interpreted according to the manufacturer's instructions. Only clear bands were considered in the analysis. Among the 1,968 plasma samples, 38 (1.93%) were HTLV-1, 13 (0.66%) were HTLV-2, and 6 (0.3%) were HTLV WB seropositive. Furthermore, 1,292 (65.65%) samples were WB sero-indeterminate, including 104 (5.28%) with an HTLV-1 Gag-indeterminate pattern (HGIP) and 68 (3.45%) with a peculiar yet unreported pattern exhibiting mostly a strong shifted GD21 and a p28. The other 619 (31.45%) samples were either WB negative or exhibited other patterns, mostly with unique p19 or p24 bands. DNA, extracted from peripheral blood buffy coat, was subjected to PCR using several primer pairs known to detect HTLV-1/2/3/4. Most DNAs from HTLV-1- and HTLV-seropositive individuals were PCR positive. In contrast, all the others, from persons with HTLV-2, HGIP, new WB, and other indeterminate patterns, were PCR negative. Epidemiological determinant analysis of the persons with this new peculiar WB pattern revealed that seroprevalence was independent from age, sex, or ethnicity, thus resembling the indeterminate profile HGIP rather than HTLV-1. Moreover, this new pattern persists over time.

Frequent and recent human acquisition of simian foamy viruses through apes' bites in central Africa

Human infection by simian foamy viruses (SFV) can be acquired by persons occupationally exposed to non-human primates (NHP) or in natural settings. This study aimed at getting better knowledge on SFV transmission dynamics, risk factors for such a zoonotic infection and, searching for intra-familial dissemination and the level of peripheral blood (pro)viral loads in infected individuals. We studied 1,321 people from the general adult population (mean age 49 yrs, 640 women and 681 men) and 198 individuals, mostly men, all of whom had encountered a NHP with a resulting bite or scratch. All of these, either Pygmies (436) or Bantus (1085) live in villages in South Cameroon. A specific SFV Western blot was used and two nested PCRs (polymerase, and LTR) were done on all the positive/borderline samples by serology. In the general population, 2/1,321 (0.2%) persons were found to be infected. In the second group, 37/198 (18.6%) persons were SFV positive. They were mostly infected by apes (37/39) FV (mainly gorilla). Infection by monkey FV was less frequent (2/39). The viral origin of the amplified sequences matched with the history reported by the hunters, most of which (83%) are aged 20 to 40 years and acquired the infection during the last twenty years. The (pro)viral load in 33 individuals infected by a gorilla FV was quite low (<1 to 145 copies per 10⁵ cells) in the peripheral blood leucocytes. Of the 30 wives and 12 children from families of FV infected persons, only one woman was seropositive in WB without subsequent viral DNA amplification. We demonstrate a high level of recent transmission of SFVs to humans in natural settings specifically following severe gorilla bites during hunting activities. The virus was found to persist over several years, with low SFV loads in infected persons. Secondary transmission remains an open question.

Most of the viral pathogens that have emerged in humans during the last decades have a zoonotic origin. After the initial interspecies transmission, these viruses have followed different evolutionary routes and have spread among humans through distinct mechanisms. The understanding of the initial steps of the emergence of several viruses and associated diseases often remains quite poor. Human infection by simian foamy viruses (SFV) can be acquired by persons occupationally exposed to non-human primates (NHP) or in natural settings. Epidemiological and microbiological studies in specific high-risk populations are necessary to gain new insights into the early events of the emergence process, and the potential to spread or cause disease among humans. The present study found that hunting is still a very common and risky activity for SFV infection in forest areas of South Cameroon. Indeed, recent interspecies transmission of SFVs to young adults is still very frequent, as 1 person out of 5 among the hunters who have reported a bite or scratch by a non-human primate and 2 persons out of a thousand in the general population are persistently infected by a SFV, mostly from an ape. Secondary transmission to other family members and presence of a disease in infected persons are still open questions that are being investigated.

Decline in prevalence and asymmetric distribution of human T cell lymphotropic virus 1 and 2 in blood donors, State of Minas Gerais, Brazil, 1993 to 2007

INTRODUCTION

Human T cell lymphotropic virus types 1 and 2 (HTLV-1/2) are endemic in Brazil and are screened for in transfusion services since 1993. This study evaluated the evolution of the prevalence of HTLV-1 and 2 in blood donors of the Hemominas Foundation from 1993 to 2007, and its geographical distribution in State of Minas Gerais, Brazil.

METHODS

The Hemominas Foundation is a centralized blood center in Minas Gerais, Brazil. The sources of data were the Hemominas Foundation Technical Bulletin and files from the centralized serological laboratory. Donors were tested in the period using enzyme linked immuno sorbent assays (ELISA), followed by Western blot, when repeatedly reactive. The data were analyzed by EPIINFO 6.2 and TABWIN 3.5 softwares.

RESULTS

The average seroprevalence in the period 1993-2007 was 0.1%. A steady decline occurred from 0.4% in 1993 to below 0.1% in 2002 and later, with a transient peak of 0.5% in 1994. HTLV reactivity distribution was asymmetrical in the state, with regions of higher prevalence, interspersed with low prevalence areas. Comparison of positive and negative donors verified that increasing age was proportional to virus positivity. Odds ratio for age ranged from 1.43 (30 to 39 years-old) to 3.09 (50 to 65 years-old). Women had a greater chance of being positive (OR-1.64), as previously described.

CONCLUSIONS

Possible explanations for HTLV-1/2 prevalence decline are the exclusion of positive donors from the donor pool, an increase in repeat donors and ELISA test improvement, with reduction in the number of false positive results.

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.

HTLV-3/STLV-3 and HTLV-4 viruses: discovery, epidemiology, serology and molecular aspects

Human T cell leukemia/lymphoma virus Type 1 and 2 (HTLV-1 and HTLV-2), together with their simian counterparts (STLV-1, STLV-2), belong to the Primate T lymphotropic viruses group (PTLV). The high percentage of homologies between HTLV-1 and STLV-1 strains, led to the demonstration that most HTLV-1 subtypes arose from interspecies transmission between monkeys and humans. STLV-3 viruses belong to the third PTLV type and are equally divergent from both HTLV-1 and HTLV-2. They are endemic in several monkey species that live in West, Central and East Africa. In 2005, we, and others reported the discovery of the human homolog (HTLV-3) of STLV-3 in two asymptomatic inhabitants from South Cameroon whose sera exhibited HTLV indeterminate serologies. More recently, two other cases of HTLV-3 infection in persons living in Cameroon were reported suggesting that this virus is not extremely rare in the human population living in Central Africa. Together with STLV-3, these human viral strains belong to the PTLV-3 group. A fourth HTLV type (HTLV-4) was also discovered in the same geographical area. The overall PTLV-3 and PTLV-4 genomic organization is similar to that of HTLV-1 and HTLV-2 with the exception of their long terminal repeats (LTRs) that contain only two 21 bp repeats. As in HTLV-1, HTLV-3 Tax contains a PDZ binding motif while HTLV-4 does not. An antisense transcript was also described in HTLV-3 transfected cells. PTLV-3 molecular clones are now available and will allow scientists to study the viral cycle, the tropism and the possible pathogenicity in vivo. Current studies are also aimed at determining the prevalence, distribution, and modes of transmission of these viruses, as well as their possible association with human diseases. Here we will review the characteristics of these new simian and human retroviruses, whose discovery has opened new avenues of research in the retrovirology field.

HTLV-2B strains, similar to those found in several Amerindian tribes, are endemic in central African Bakola Pygmies

BACKGROUND

The presence and origin of endemic foci of human T-lymphotropic virus type 2 (HTLV2) infection in Africa remain a matter of debate.

METHODS

To better appreciate such determinants, we performed a survey of 1918 inhabitants from Cameroon forest areas, including 1051 Bakola Pygmies and 867 Bantus.

RESULTS

The overall HTLV-1/2 seroprevalence was 4% (49 cases of HTLV-1 and 27 cases of HTLV-2 infection). Both infections were mainly restricted to the Bakola Pygmies, with surprisingly no HTLV-2 infections in the Bantu population. Both HTLV-1 and HTLV-2 seroprevalences increased with age. There was evidence of ongoing HTLV-2 transmission in this population. Lymphoid T cell lines producing HTLV-2 were established. HTLV-2 long terminal repeat sequences (672 base pairs) obtained from 7 infected Bakola were highly similar to each other (<1% nucleotide divergence), as well as to Amerindian HTLV-2B strains. Analyses on a complete sequence (8954 base pairs) confirmed that it was a typical HTLV-2 subtype B strain. Along with molecular clock analysis, these data strongly suggest that HTLV-2 has been endemic in the Bakola Pygmy population for a long time.

CONCLUSIONS

This study demonstrates clearly an HTLV-2 endemicity with ongoing transmission in an African population. Furthermore, it give insights into central questions regarding the origins and evolution rate of HTLV-2 and the migrations of infected populations.

Molecular analysis of human T cell lymphotropic virus type 1 and 2 (HTLV-1/2) seroindeterminate blood donors from Northeast Iran: evidence of proviral tax, env, and gag sequences

Human T cell lymphotropic virus type 1 and 2 (HTLV-1/2) Western blot indeterminate results are a problem for blood banks in endemic areas. To determine the prevalence of HTLV-1/2 infection among indeterminate donors, we analyzed 130 cases from Mashhad, an HTLV-1/2 endemic area in Northeast Iran. The most frequent Western blot bands were GD21 alone (37.2%) followed by rgp46-2 alone (32.1%). We further tested 40 available DNA samples of these cases by PCR for viral sequences, tax, gag, and pol, and found five cases (12.5%) to be positive for two or three HTLV-1 genes. There were no significant age, sex, and blood group differences between PCR-positive and PCR-negative cases. Among PCR-positive individuals, the most prevalent Western blot bands were variable combinations of rgp46-1, GD21, and gp21. The mean of the optical density (OD) of the enzyme-linked immunosorbent assay (ELISA) test was significantly higher in PCR-positive individuals. The frequency of the rgp46-1 band was also significantly higher in PCR-positive cases compared to PCR-negative ones. In conclusion, the majority of HTLV-indeterminate donors lack the HTLV provirus and therefore are not considered infected. However, in some cases with higher ODs in the ELISA test and seroreactivity to env proteins, rgp46-1 and GD21 in particular may be indicative of infection and need further evaluation by molecular methods.

Long-term serological follow-up of blood donors with an HTLV-indeterminate western blot: antibody profile of seroconverters and individuals with false reactions

The high proportion of indeterminate results of the screening test for human T-lymphotropic virus (HTLV) infection has been a challenge worldwide. In this study, 60 persons with seroindeterminate results for HTLV were followed until their serological status was defined. At least two independent serological tests (EIA and WB) from sequential samples were performed at an average interval of 4.4 years, totaling 141 serum samples tested. Seroconversion occurred in 12 individuals (reactive by EIA, positive by WB and PCR), and 48 were classified as false reactions (non-reactive EIA and negative PCR, but indeterminate WB). The seroconverter group had epidemiological features similar to those seen in HTLV-1 carriers, and the average time of follow-up for seroconversion was 4 years. In the group with false reactions, the most frequent indeterminate WB pattern in the samples was the presence of p24 alone. This pattern was absent in the seroconverter group, suggesting that p24 alone is an indicator of false reactivity. In contrast, the presence of p19 and p24 seems to be an indicator of true reactivity, since this pattern was frequent (66.7%) among the seroconverters and much less common (10.4% of the first samples) among the individuals with false reactions (P = 0.0001). Thus, HTLV infection may be suspected when reactivity to p19 and p24 is observed. Individuals with an indeterminate WB pattern should be followed-up and retested. The improvement of the HTLV algorithm screening of blood donors has been necessary to reduce inconclusive results and to avoid unnecessary follow-up to define the status of infection.

The imprint of the Slave Trade in an African American population: mitochondrial DNA, Y chromosome and HTLV-1 analysis in the Noir Marron of French Guiana

Background

Retracing the genetic histories of the descendant populations of the Slave Trade (16^th-19^th centuries) is particularly challenging due to the diversity of African ethnic groups involved and the different hybridisation processes with Europeans and Amerindians, which have blurred their original genetic inheritances. The Noir Marron in French Guiana are the direct descendants of maroons who escaped from Dutch plantations in the current day Surinam. They represent an original ethnic group with a highly blended culture. Uniparental markers (mtDNA and NRY) coupled with HTLV-1 sequences (env and LTR) were studied to establish the genetic relationships linking them to African American and African populations.

Results

All genetic systems presented a high conservation of the African gene pool (African ancestry: mtDNA = 99.3%; NRY = 97.6%; HTLV-1 env = 20/23; HTLV-1 LTR = 6/8). Neither founder effect nor genetic drift was detected and the genetic diversity is within a range commonly observed in Africa. Higher genetic similarities were observed with the populations inhabiting the Bight of Benin (from Ivory Coast to Benin). Other ancestries were identified but they presented an interesting sex-bias. Whilst male origins spread throughout the north of the bight (from Benin to Senegal), female origins were spread throughout the south (from the Ivory Coast to Angola).

Conclusions

The Noir Marron are unique in having conserved their African genetic ancestry, despite major cultural exchanges with Amerindians and Europeans through inhabiting the same region for four centuries. Their maroon identity and the important number of slaves deported in this region have maintained the original African diversity. All these characteristics permit to identify a major origin located in the former region of the Gold Coast and the Bight of Benin; regions highly impacted by slavery, from which goes a sex-biased longitudinal gradient of ancestry.

Anti-Tax antibody levels in asymptomatic carriers, oligosymptomatic carriers, patients with rheumatologic disease or with HAM/TSP do not correlate with HTLV-1 proviral load

BACKGROUND

HTLV-1 infects millions of people around the world and induces myelopathy (HAM/TSP), adult T-cell leukemia (ATL) or other inflammatory or rheumatologic diseases. The host-virus interaction causes asymptomatic carriers to develop HAM/TSP. Biomarkers are needed to predict patients who are at risk for HAM/TSP. Tax is highly immunogenic and is a major target protein recognized by cytotoxic T lymphocytes. Anti-Tax antibodies are involved in HAM/TSP pathogenesis.

OBJECTIVES

To assess anti-Tax IgG reactivity with a flow cytometry assay (FCA) using an infection/transfection system with Vaccinia virus and pLW44/Tax-expressing Tax and to correlate the anti-Tax response and the HTLV-1 proviral load.

STUDY DESIGN

: We enrolled 81 individuals: 9 HTLV-1 seronegative (NP) and 72 HTLV-1 positive (23 HTLV-1 asymptomatic carriers (AC), 12 oligosymptomatic patients (OL), 7 with rheumatologic diseases (DR) and 30 with HAM/TSP (HT)). Anti-Tax reactivity was assessed by FCA, and HTLV-1 proviral load was measured with real time PCR.

RESULTS

The HT and DR groups showed greater anti-Tax IgG reactivity (p<0.001 and p<0.05 comparing HT to the OL and AC group, respectively; p<0.05 comparing DR to the OL group), and the reactivity in the DR+HT group was significantly different when compared to the AC group (p<0.05) and to the OL group (p<0.001). The proviral load was higher in the HT group compared to the OL (p<0.001) and in the HT+DR group compared to OL (p<0.001). There was no correlation between anti-Tax IgG reactivity and proviral load in any of the HTLV-1-infected groups.

CONCLUSION

These findings suggest that although anti-Tax IgG reactivity and the HTLV-1 proviral load are important markers of the development of HTLV-1-associated diseases, their levels are not correlated.

Neither molecular diversity of the envelope, immunosuppression status, nor proviral load causes indeterminate HTLV western blot profiles in samples from human T-cell lymphotropic virus type 2 (HTLV-2)-infected individuals

Although human T-cell lymphotropic virus type 2 (HTLV-2) is considered of low pathogenicity, serological diagnosis is important for counseling and monitoring. The confirmatory tests most used are Western blot (WB) and PCR. However, in high-risk populations, about 50% of the indeterminate WB were HTLV-2 positives by PCR. The insensitivity of the WB might be due to the use of recombinant proteins of strains that do not circulate in our country. Another possibility may be a high level of immunosuppression, which could lead to low production of virus, resulting in low stimulation of antibody. We found one mutation, proline to serine in the envelope region in the position 184, presented at least 1/3 of the samples, independent the indeterminate WB profile. In conclusion, we found no correlation of immune state, HTLV-2 proviral load, or env diversity in the K55 region and WB indeterminate results. We believe that the only WB kit available in the market is probably more accurate to detect HTLV-1 antibodies, and some improvement for HTLV-2 detection should be done in the future, especially among high-risk population.

Emergence of a novel and highly divergent HTLV-3 in a primate hunter in Cameroon

The recent discovery of human T-lymphotropic virus type 3 (HTLV-3) in Cameroon highlights the importance of expanded surveillance to better understand the prevalence and public health impact of this new retrovirus. HTLV diversity was investigated in 408 persons in rural Cameroon who reported simian exposures. Plasma from 29 persons (7.2%) had reactive serology. HTLV tax sequences were detected in 3 persons. Phylogenetic analysis confirmed HTLV-1 infection in two individuals and HTLV-3 infection in a third person (Cam2013AB). The complete proviral genome from Cam2013AB shared 98% identity and clustered tightly in distinct lineage with simian T-lymphotropic virus type 3 (STLV-3) subtype D recently identified in two guenon monkeys near this person's village. These results document a fourth HTLV-3 infection with a new and highly divergent strain we designate HTLV-3 (Cam2013AB) subtype D demonstrating the existence of a broad HTLV-3 diversity likely originating from multiple zoonotic transmissions of divergent STLV-3.

Adult T-Cell Leukemia/Lymphoma (ATLL): Report of Two Fully Documented Hellenic Patients

ATLL is etiologically associated with HTLV-I retrovirus. A population of 10 to 20 million worldwide is estimated to be infected by the virus, but only 1-4% develop ATLL during a 70-year lifespan. The latency period is more than 30 years. The aim of this study was to report two cases of ATLL in Greek patients with the concomitant study of their family members. A 55-year-old woman and a 59-year-old man presented with leucocytosis and lymphocytosis. Both were asymptomatic and physical examination was unremarkable except for minimal lymphadenopathy in the second patient. In both patients blood smears showed small-to-medium-sized, multilobulated lymphocytes, with different degrees of nuclear irregularity. Immunophenotypic study was as follows: CD2 + (97%), CD3 + (95%), CD5 + (95%), CD3/CD4 + (93%), CD3/CD25 + (84%), CD7 -/CD4 + (89%) CD2 + /HLA-DR + (53%), TCRabeta + (96%) and CD7-(7%). Bone marrow biopsy revealed a normal cellularity with dyserythropoiesis and scattered small lymphocytes (CD4 + on immunostaining) Serum HTLV I and II antibodies were positive. T-cell receptor gamma-chain rearrangement was positive in blood lymphocytes by PCR. Cytogenetic analysis showed complex karyotypic abnormalities. DNA analysis by PCR demonstrated the integration of the HTLV-I DNA in the DNA of the neoplastic T cells. Both patients rapidly developed acute type ATLL. In the first patient multiple subcutaneous nodules on the palmar surface of both hands were also observed. She received deoxycoformycin, which was stopped because of autoimmune hemolytic anemia. Corticosteroid treatment was initiated, with gradual improvement. She suffered from recurrent opportunistic infections. She is currently under interferon and zidovudine therapy with stable blood parameters. Chemotherapy was administered to the other patient with > 50% initial response. Both patients' families were tested for serum anti HTLV-I antibodies and their mates were found to be positive; they also had detectable viral DNA by PCR analysis while asymptomatic, with no abnormal clinical findings and normal white blood cell count and morphology. In conclusion, the two aforementioned patients are the first fully documented ATLL patients described in Greece. Investigation for HTLV-I antibodies should be mandatory in all patients with T-cell lymphoproliferative disorders.

Confirming the presence of HTLV-1 infection and the absence of HTLV-2 in blood donors from Arequipa, Peru

Epidemiological studies conducted in Peru disclosed HTLV-1 to be prevalent in different ethnic groups, and found HTLV-2 in some Amazonian Indians and in men who have sex with men. No data concerning HTLV-1/2 infection in blood donors from Arequipa, a highlands region in southern Peru, is available. We searched for the presence of HTLV-1 and HTLV-2 antibodies in 2,732 serum samples obtained from blood donors from this geographic area. HTLV-1/2-specific antibodies were detected using an enzyme-linked immunosorbent assay (ELISA) and were confirmed by Western blot (WB). Reactive sera had their blood bags discarded from donation, and the demographic characteristics of the donors were analyzed. Thirty-five sera (1.2%) were HTLV seroreactive by ELISA, and 25 were confirmed HTLV-1-positive by WB. One serum disclosed HTLV-positivity, and the remaining nine serum samples showed indeterminate results by WB; three of which had an HTLV-1 indeterminate Gag profile. The median age of HTLV-positive individuals was 34.6 years; 27 were male and eight were female. All individuals were from southern Peru: 27 from Arequipa, five from Puno, and three from Cuzco. HTLV co-positivity with hepatitis B (five sera) and syphilis (one serum) were detected. Previous transfusion and tattooing were observed in two and one individuals, respectively. No serum was positive for HTLV/HIV co-infection. This study confirmed, for the first time, HTLV-1 infection and the absence of HTLV-2 infection in blood donors from Arequipa, Peru and suggests vertical transmission as the major route of HTLV-1 transmission and acquisition in this geographic region.

Molecular evidence of human T-cell lymphotropic virus types 1 and 2 (HTLV-1 and HTLV-2) infections in HTLV seroindeterminate individuals from São Paulo, Brazil

BACKGROUND

Using enzyme immunoassays and Western blot (Wb) tests, HTLV serodiagnosis yields indeterminate results in a significant number of cases.

OBJECTIVE

To determine the prevalence of HTLV infection among HTLV-seroindeterminate individuals.

STUDY DESIGN

We studied peripheral blood mononuclear cells from 65 anti-HTLV Wb-seroindeterminate individuals by attempting to amplify proviral DNA sequences (tax and pol) to identify HTLV-1 and HTLV-2 infections.

RESULTS

These 65 specimens exhibited predominantly (43%) anti-HTLV antibodies to gag-coded antigens in the absence of anti-p24 on Wb analysis. Tax proviral sequences were detected in 6 (9.2%) samples. According to restricted fragment polymorphism analysis (RFLP), we identified HTLV-1 proviral DNA in 4 samples, HTLV-2 in one and sequences from both in another. Nested PCR for the pol region was positive in 3 (4.6%) specimens, which were also positive for tax sequences. After hybridization HTLV-1 infection was confirmed in 2 samples (3.1%) and HTLV-2 in another (1.5%). Detection of a single HTLV DNA sequence may be due to infection by defective provirus, but its significance remains undefined. In this cohort, no Wb reactivity pattern was predictive of proviral detection. HTLV-1 infection was demonstrated in an individual who had Wb reactivity to gag-coded antigens only.

CONCLUSIONS

This emphasizes the importance of clinical and laboratory follow-up of HTLV-seroindeterminate individuals from endemic areas.

The human HTLV-3 and HTLV-4 retroviruses: new members of the HTLV family

Human T cell leukemia/lymphoma virus Type 1 and 2 (HTLV-1 and HTLV-2), together with their simian counterparts (STLV-1, STLV-2), belong to the Primate T lymphotropic viruses group (PTLV). HTLV-1 infects 15 to 20million people worldwide, while STLV-1 is endemic in a number of simian or ape species living in Africa or Asia. The high percentage of homologies between HTLV-1 and STLV-1 strains, led to the demonstration that most HTLV-1 subtypes arose from interspecies transmission between monkeys and humans. STLV-3 viruses belong to the third PTLV type and are equally divergent from HTLV-1 than from HTLV-2. They are endemic in several monkey species that live in West, Central, and East Africa. In 2005, we and others reported the discovery of the human homolog (HTLV-3) of STLV-3 in two asymptomatic inhabitants from South Cameroon whose sera exhibited HTLV indeterminate serologies. More recently, we reported a third case of HTLV-3 infection in Cameroon suggesting that this virus is not rare in the human population living in Central Africa. Together with STLV-3, these three human viral strains belong therefore to the PTLV-3 type. A fourth HTLV type (HTLV-4) was also discovered in the same geographical area. Current studies are aimed at determining the prevalence, distribution and modes of transmission of these viruses as well as their possible association with human diseases. Furthermore, molecular characterization of their viral transactivator Tax is ongoing in order to look for possible oncogenic properties.

Serological patterns and temporal trends of HTLV-1/2 infection in high-risk populations attending Public Health Units in São Paulo, Brazil

BACKGROUND

HTLV-1/2 diagnosis in high-risk populations from São Paulo, Brazil has been problematic due a high proportion of seroindeterminate results.

OBJECTIVES

To confirm and extend previous findings regarding HTLV-1/2 diagnosis in this geographic area.

STUDY DESIGN

Sera from 2312 patients were tested for HTLV-1/2 antibodies using enzyme immunoassay (EIA) and Western blot (WB) analysis. Patients were from AIDS Reference Centers (Group I; 1393 patients) and HTLV out-patient clinics (Group II; 919 patients). Results were analyzed according to patients' age, gender, and clinic type.

RESULTS

HTLV-1 and HTLV-2 were detected in both groups. Among seropositive females, HTLV-2 was slightly more common in Group I (54.5%), while HTLV-1 prevailed in Group II (73.9%). Males from Group II had a higher percentage of HTLV-seroindeterminate results. No correlation between HTLV serological results and age was detected. Temporal analyses disclosed a high number of HTLV-seroindeterminate samples, and a large spectrum of indeterminate WB profiles. GD21 and/or rgp46-II bands were detected in 34.6% of sera from Group I, and a p24 or p19 band was detected in 35.3% of sera from Group II.

CONCLUSIONS

High rates of HTLV-indeterminate serological patterns during temporal analyses were confirmed in high-risk populations from São Paulo, Brazil.

Difficulties in the diagnosis of HTLV-2 infection in HIV/AIDS patients from Brazil: comparative performances of serologic and molecular assays, and detection of HTLV-2b subtype

The current diagnosis of human T-lymphotropic virus type-2 (HTLV-2) infection is based on the search of specific antibodies; nevertheless, several studies conducted in Brazil pointed deficiencies of the commercially available kits in detecting HTLV-2, mostly in HIV/AIDS patients. This study searched for the presence of HTLV-1 and -2 in 758 HIV/AIDS patients from Londrina, Paraná, Brazil. Serum samples were screened for HTLV-1/2 antibodies using two EIA kits (Vironostika and Murex), and confirmed by WB (HTLV Blot 2.4, Genelabs). The results obtained by EIA disclosed 49 (6.5%) reactive sera: 43 positive by both EIA kits, and six with discordant results. WB confirmed HTLV-1 infection in seven samples (0.9%) and HTLV-2 in 21 sera (2.8%). Negative and indeterminate results were detected in four (0.5%) and 16 (2.1%) sera, respectively. Blood from 47 out of 49 HTLV seroreactive patients were collected and analyzed for the presence of env, LTR and tax genomic segments of HTLVs by PCR. PCR confirmed six cases of HTLV-1 and 37 cases of HTLV-2 infection (14 out of 16 that were found to be WB indeterminate). Restriction analysis of the env PCR products of HTLV-2 disclosed 36 isolates of HTLV-2a/c subtype, and one of HTLV-2b subtype. These results emphasize the need of improving serologic tests for detecting truly HTLV-2 infected patients from Brazil, and confirm the presence of HTLV-2b subtype in the South of this country.

Seroprevalence and molecular epidemiology of human T-Cell leukemia virus type 1 (HTLV-1) and HTLV-2 in blood donors from Dakar, Senegal

In 2002, human T-cell leukemia virus type 1 (HTLV-1) and HTLV-2 seroprevalence was 0.16% (8/4,900) in blood donors from Dakar, Senegal. Most of the positive donors originated from the country's southern region. Seven donors were infected by HTLV-1 (of cosmopolitan subtype), and one was infected by HTLV-2. These data highlight the problem of transfusion safety in this area where HTLV-1-associated lymphoproliferative and neurological diseases are endemic.

Ancient origin and molecular features of the novel human T-lymphotropic virus type 3 revealed by complete genome analysis

Human T-lymphotropic virus type 3 (HTLV-3) is a new virus recently identified in two primate hunters in Central Africa. Limited sequence analysis shows that HTLV-3 is distinct from HTLV-1 and HTLV-2 but is genetically similar to simian T-lymphotropic virus type 3 (STLV-3). We report here the first complete HTLV-3 sequence obtained by PCR-based genome walking using uncultured peripheral blood lymphocytes from an HTLV-3-infected person. The HTLV-3(2026ND) genome is 8,917 bp long and is genetically equidistant from HTLV-1 and HTLV-2, sharing about 62% identity. Phylogenetic analysis of all gene regions confirms this relationship and shows that HTLV-3 falls within the diversity of STLV-3, suggesting a primate origin. However, HTLV-3(2026ND) is unique, sharing only 87% to 92% sequence identity with STLV-3. SimPlot and phylogenetic analysis did not reveal any evidence of genetic recombination with either HTLV-1, HTLV-2, or STLV-3. Molecular dating estimates that the ancestor of HTLV-3 is as old as HTLV-1 and HTLV-2, with an inferred divergence time of 36,087 to 54,067 years ago. HTLV-3 has a prototypic genomic structure, with all enzymatic, regulatory, and structural proteins preserved. Like STLV-3, HTLV-3 is missing a third 21-bp transcription element found in the long terminal repeats of HTLV-1 and HTLV-2 but instead contains a unique activator protein-1 transcription factor upstream of the 21-bp repeat elements. A PDZ motif, like that in HTLV-1, which is important for cellular signal transduction and transformation, is present in the C terminus of the HTLV-3 Tax protein. A basic leucine zipper region located in the antisense strand of HTLV-1, believed to play a role in viral replication and oncogenesis, was also found in the complementary strand of HTLV-3. The ancient origin of HTLV-3, the broad distribution of STLV-3 in Africa, and the propensity of STLVs to cross species into humans all suggest that HTLV-3 may be prevalent and support the need for expanded surveillance for this virus.

Human T-cell lymphotropic virus types I and II (HTLV-I and -II) infection among seroindeterminate cases in Argentina

Human T-cell lymphotropic virus (HTLV) seroindeterminate cases have been reported among blood donors (BD) and in at-risk populations worldwide, including Argentina. The objective of the present work was to study the presence of HTLV-I/II infection and its association to specific Western blot (WB) patterns among healthy BD and at-risk populations in Argentina. We analyzed 83 HTLV-I/II seroindeterminate WB cases diagnosed among BD (n = 49) and in different at-risk populations (n = 34) for human retroviruses infections. Multiple indeterminate WB patterns were observed. Out of the total, 13.2% (11/83) of the cases were found to be HTLV-I/II positive by nested-PCR (n-PCR), including 13.2% (11/83) HTLV-I and 2.4% (2/83) presenting HTLV-I and -II co-infection. Most of their serological profiles showed reactivity to gag or env codified proteins. Two samples amplified only one of the six analyzed genes (1 HTLV-I pol gene and 1 HTLV-II tax gene). There was no association between the presence of Trypanosoma cruzi infection and an HTLV-I/II indeterminate WB pattern (only 3 of the 83 samples were positive for T. cruzi antibodies). In conclusion, the majority of HTLV-seroindeterminate WB donors lacked HTLV provirus and was thus considered uninfected. However, when seroreactivity to Env and Gag proteins are observed on the WB and especially in at-risk populations, HTLV infection should be suspected; such individuals should be followed-up and retested.

Molecular characterization of human T-cell lymphotropic virus type 2 (HTLV-II) from people living in urban areas of Sao Paulo city: Evidence of multiple subtypes circulation

BACKGROUND

In Brazil, human T-cell lymphotropic virus type I and type II (HTLV-I and HTLV-II) are co-circulating and possess approximately 65% homology, which results in high cross-reactivity in serological tests. Based on the detection of EIA and Western blot (WB) tests, HTLV serodiagnosis yields indeterminate results in high-risk population, with the true determination of HTLV-II prevalence requiring a combined serological and molecular analysis. Molecular analysis of HTLV-II isolates has shown the existence of four distinct subtypes: IIa, IIb, IIc, and IId. The aim of this study was to evaluate the routine EIA and WB used in Sao Paulo city, as well as molecular methods for confirmation of infection and HTLV-II subtype distribution.

RESULTS

Two hundred ninety-three individuals, who were enrolled in the HTLV out-clinic in Sao Paulo city, Brazil, between July 1997 and May 2003, were tested by EIAs, and positive sera 232 (79%) reactive by one of the tests. When these sera were tested by WB revealed 134 were HTLV-I, 28 HTLV-II, 4 HTLV-I/II, and 48 were indeterminate. Polymerase chain reaction (PCR) on the indeterminate group showed that 20 (42%) were HTLV-II and 28 were negative. From a total of 48 HTLV-II subjects with DNA available, restriction fragment length polymorphism (RFLP) of the env region revealed 47 HTLV-IIa and 1 HTLV-IIb. The phylogenetic analysis was performed on 23 samples, which identified 19 as subtype a, Brazilian subcluster, and 4 as subtype b. This is the first time HTLV-II subtype b has been described in Brazil. However, further studies, such as a complete nucleotide DNA sequencing, need to be done to confirm these findings.

Global epidemiology of HTLV-I infection and associated diseases

Epidemiologic aspects of human T-lymphotropic virus type I (HTLV-I) infection have been thoroughly studied over the course of approximately 25 years since its first description. The geographic distribution of the virus has been defined, with Japan, Africa, Caribbean islands and South America emerging as the areas of highest prevalence. The reasons for HTLV-I clustering, such as the high ubiquity in southwestern Japan but low prevalence in neighboring regions of Korea, China and eastern Russia are still unknown. The major modes of transmission are well understood, although better quantitative data on the incidence of transmission, and on promoting/inhibiting factors, are needed. Epidemiologic proof has been obtained for HTLV-I's causative role in major disease associations: adult T-cell leukemia (ATL), HTLV-associated myelopathy/tropical spastic paraparesis (HAM/TSP), HTLV-associated uveitis and infective dermatitis. However, more and better studies are needed for other apparent disease outcomes such as rheumatologic, psychiatric and infectious diseases. Since curative treatment of ATL and HAM/TSP is lacking and a vaccine is unavailable, the social and financial cost for the individual, his/her family and the health system is immense. For this reason, public health interventions aimed at counseling and educating high-risk individuals and populations are of paramount importance.