Natural history of viral markers in children infected with human T lymphotropic virus type I in Jamaica

How Can We Prevent Mother-to-Child Transmission of HTLV-1?

The perception of human T-cell leukemia virus type 1 (HTlV-1) infection as a "silent disease" has recently given way to concern that its presence may be having a variety of effects. HTLV-1 is known to cause adult T-cell leukemia (ATL), an aggressive cancer of peripheral CD4 T cells; however, it is also responsible for HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Most patients develop ATL as a result of HTLV-1 mother-to-child transmission. The primary route of mother-to-child transmission is through the mother's milk. In the absence of effective drug therapy, total artificial nutrition such as exclusive formula feeding is a reliable means of preventing mother-to-child transmission after birth, except for a small percentage of prenatal infections. A recent study found that the rate of mother-to-child transmission with short-term breastfeeding (within 90 days) did not exceed that of total artificial nutrition. Because these preventive measures are in exchange for the benefits of breastfeeding, clinical applications of antiretroviral drugs and immunotherapy with vaccines and neutralizing antibodies are urgently needed.

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.

Health state utility values in people living with HTLV-1 and in patients with HAM/TSP: The impact of a neglected disease on the quality of life

BACKGROUND

HTLV-1 is a neglected sexually transmitted infection despite being the cause of disabling neurological disease HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). There is no treatment for this infection and public health policies are essential to reduce its transmission. However, there are no data to support adequate cost-effective analysis in this field. The aim of this study was to obtain health state utility values for individuals with HAM/TSP and HTLV-1 asymptomatic carriers (AC). The impact of both states on quality of life (QoL) is described and compared to other diseases.

METHODS

A cross-sectional observational study of 141 individuals infected with HTLV-1 (79 with HAM/TSP and 62 AC) from three Brazilian states (Rio de Janeiro, São Paulo and Alagoas) and from the United Kingdom. Participants completed a validated general health questionnaire (EQ-5D, Euroqol) from which country specific health state utility values are generated. Clinical and epidemiological data were collated.

PRINCIPAL FINDINGS

Health state utility value for HAM/TSP was 0.2991. QoL for 130 reported clinical conditions ranges from 0.35 to 0.847. 12% reported their quality of life as worse as death. Low QoL was associated with severity rather than duration of disease with a moderate inverse correlation between QoL and Osame's Motor Disability Score (-0.4933) Patients who are wheelchair dependent had lowest QoL whilst those still walking unaided had the highest. AC also reported impaired QoL (0.7121) compared to general population.

CONCLUSION

HTLV-1 and its associated neurological disease has a marked impact on QoL. This study provides robust data to support the development of cost-utility analysis of interventions for HTLV-1.

Influence of Immunogenetic Biomarkers in the Clinical Outcome of HTLV-1 Infected Persons

Human T-lymphotropic virus 1, a member of the Retroviridae family, causes a neglected, silent, persistent infection affecting circa 5 to 10 million people around the world, with biology, immune pathology, clinical diseases, epidemiology, and laboratory issues still unsolved. Most of the infected subjects are asymptomatic, but severe clinical disorders appear as a neurodegenerative disease (HTLV-1 associated myelopathy—HAM) or a lymphoprolipherative disorder (Adult T Leukemia/Lymphoma—ATLL) and in other target organs of the human body. HTLV-1 infections are frequently asymptomatic, but there is a large spectrum of diseases that have been described along the years. The mechanisms by which the virus interacts with the host, the different modes of response of the host to the infection, and the immunogenic characteristics of the host are some of the interesting and unanswered questions that may direct the outcome of the disease. The most relevant published results dealing with the genetic variations of the host, the immune response to HTLV-1 infection, and the outcome of the infection are presented herein, including Human Leucocyte Antigen (HLA), Killer Immunoglobulin-like Receptors (KIR), interleukin 6, 10, 28, Fas and Fas ligand, IFN-gamma, TNF-A, and Mannose-binding lectin. In summary, there are still several unmet research needs in the field of useful biomarkers on HTLV-1 pathogenesis.

Natural Course of Human T-Cell Leukemia Virus Type 1 Proviral DNA Levels in Carriers During Pregnancy

The measurement of human T-cell leukemia virus type 1 (HTLV-1) proviral DNA levels by using polymerase chain reaction has been beneficial for confirming HTLV-1 infection during pregnancy. However, the influence of pregnancy on HTLV-1 infection and proviral DNA levels among pregnant women with HTLV-1 has not been clarified. We prospectively gathered blood samples from 36 pregnant women in whom HTLV-1 carriage was previously diagnosed and sequentially measured their proviral DNA levels. The HTLV-1 proviral DNA levels remained at a plateau during pregnancy but were elevated after delivery. Moreover, flow cytometry and serological analyses revealed that the regulatory T-cell population and soluble interleukin 2 receptor levels were similarly elevated after birth in comparison with those in control pregnant women. This study is the first to provide data on sequential changes in HTLV-1 proviral DNA levels during and after pregnancy. These findings will guide the establishment of a better program to prevent mother-to-child transmission of HTLV-1.

A novel mother-to-child human T-cell leukaemia virus type 1 (HTLV-1) transmission model for investigating the role of maternal anti-HTLV-1 antibodies using orally infected mother rats

Human T-cell leukaemia virus type 1 (HTLV-1) is a human retrovirus that is a causative agent of adult T-cell leukaemia/lymphoma (ATL) and is mainly transmitted from an infected mother to her child via breastfeeding. Such an HTLV-1 infection during childhood is believed to be a risk factor for ATL development. Although it has been suggested that an increased proviral load (PVL), a higher titre of antibody (Ab) in the infected mother and prolonged breastfeeding are associated with an increased risk of mother-to-child transmission (MTCT), the mechanisms underlying MTCT of HTLV-1 remain largely unknown. In this study, we developed an MTCT model using orally HTLV-1-infected rats that have no Ab responses against viral antigens, such as Gag and Env. In this model, HTLV-1 could be transmitted from the infected mother rats to their offspring at a high rate (50-100 %), and the rate of MTCT tended to be correlated with the PVL of the infected mother rats. Furthermore, passive immunization of uninfected adult rats and an infected mother rat with a rat anti-HTLV-1 Env gp46-neutralizing mAb was unable to suppress primary oral HTLV-1 infection to the adult rats and vertical HTLV-1 transmission to the offspring, respectively. Our findings indicate that this MTCT model would be useful to investigate not only the mechanisms of MTCT but also the role of anti-HTLV-1 Ab in MTCT of HTLV-1. They also provide some information on the role of maternal Abs in MTCT, which should be considered when designing a strategy for prevention of MTCT of HTLV-1.

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.

Quantitative differences in HTLV-I antibody responses: classification and relative risk assessment for asymptomatic carriers and ATL and HAM/TSP patients from Jamaica

Adult T-cell leukemia (ATL) and human T-cell lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) are known to be caused by HTLV-I infection. However, current methods used to determine HTLV-I infection do not differentiate between HTLV-I asymptomatic carriers (ACs) and ATL and HAM/TSP patients. Using the luciferase immunoprecipitation system, a highly sensitive, quantitative technology that can efficiently detect HTLV-I Ab responses, we examined Ab responses for HTLV-I in serum/plasma samples from 439 subjects in Jamaica, including HTLV-I-seronegative donors, ACs, and ATL and HAM/TSP patients. The Ab responses of HTLV-I-infected subjects differed significantly from those of seronegative donors for all 3 immunodominant proteins, Gag, Env, and Tax. HAM/TSP patients had significantly higher Ab responses for Gag and Env compared with ACs, and Ab responses for all 3 Ags were higher in HAM/TSP patients than in ATL patients. Moreover, immunoreactivities for HTLV-I Ags as determined by the luciferase immunoprecipitation system could distinguish HAM/TSP patients from ACs at a true-positive rate of 85.42% and from ATL patients at a true-positive rate of 75.00%, and modeled in conjunction with subject information to distinguish HAM/TSP patients from ACs (odds ratio = 14.12) and from ATL patients (odds ratio = 7.00). The relative risk assessment resulting from these significant differences between Ab responses in HTLV-I-infected groups may be a useful diagnostic tool in the future.

Transformation of breast milk macrophages by HTLV-I: implications for HTLV-I transmission via breastfeeding

Human T cell leukemia virus type I (HTLV-I), a causative agent of adult T-cell leukemia (ATL), is transmitted from mother to child predominantly by breastfeeding. The source of HTLV-I-infected cells in breast milk has been thought to be T cells, however, the majority of cells in breast milk are CD14(+) macrophages but not CD3(+) T lymphocytes, and no data are available regarding HTLV-I transmission through breast milk macrophages (BrMMpsi). To explore the potential of BrMMpsi as a possible source of infection in mother to child transmission (MTCT) of HTLV-I, an immortalized cell line (HTLV-BrMMpsi) has been established from BrMMpsi by infection with HTLV-I. HTLV-BrMMpsi retained macrophage characteristics and did not express a complete dendritic cell (DC) phenotype; nevertheless, HTLV-BrMMpsi efficiently promoted T cell proliferation in primary allogeneic mixed lymphocyte reaction (MLR) like DC. Moreover, HTLV-I infection could be transmitted from HTLV-BrMMpsi to activated T cells in the peripheral blood. These findings suggested that BrMMpsi might be an appropriate HTLV-I reservoir involved in MTCT transmission via breastfeeding.

High HTLV-1 proviral load, a marker for HTLV-1 associated myelopathy/tropical spastic paraparesis, is also detected in patients with infective dermatitis associated with HTLV-1

Salvador (BA, Brazil) is an endemic area for human T-cell lymphotrophic virus type 1 (HTLV-1). The overall prevalence of HTLV-1 infection in the general population has been estimated to be 1.76%. HTLV-1 carriers may develop a variety of diseases such as adult T-cell leukemia/lymphoma, HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and infective dermatitis associated with HTLV-1 (IDH). IDH is a chronic and severe form of childhood exudative and infective dermatitis involving mainly the scalp, neck and ears. It has recently been observed that 30% of patients with IDH develop juvenile HAM/TSP. The replication of HTLV-1 has been reported to be greater in adult HAM/TSP patients than in asymptomatic HTLV-1 carriers. In the current study, the proviral load of 28 children and adolescents with IDH not associated with HAM/TSP was determined and the results were compared to those obtained in 28 HTLV-1 adult carriers and 28 adult patients with HAM/TSP. The proviral load in IDH patients was similar to that of patients with HAM/TSP and much higher than that found in HTLV-1 carriers. The high levels of proviral load in IDH patients were not associated with age, duration of illness, duration of breast-feeding, or activity status of the skin disease. Since proviral load is associated with neurological disability, these data support the view that IDH patients are at high risk of developing HAM/TSP.

Proviral loads and clonal expansion of HTLV-1-infected cells following vertical transmission: a 10-year follow-up of children in Jamaica

OBJECTIVE

Few studies have specifically examined proviral load (PVL) and clonal evolution of human T-lymphotropic virus type 1 (HTLV-1)-infected cells in vertically infected children.

METHODS

Sequential samples (from ages 1 to 16 years) from 3 HTLV-1-infected children (cases A, B and C) in the Jamaica Mother Infant Cohort Study were analyzed for their PVL and clonal expansion of HTLV-1-infected cells in peripheral blood mononuclear cells (PBMCs) by inverse-long PCR.

RESULTS

The baseline PVL (per 100,000 PBMCs) of case A was 260 (at 1 year of age) and of case B it was 1,867 (at 3 years of age), and they remained constant for more than 10 years. Stochastic patterns of clonal expansion of HTLV-1-infected cells were predominately detected. In contrast, case C, who had lymphadenopathy, seborrheic dermatitis and hyperreflexia, showed an increase in PVL from 2,819 at 1.9 years to 13,358 at 13 years of age, and expansion of 2 dominant clones.

CONCLUSION

The clonal expansion of HTLV-1-infected cells is induced in early childhood after infection acquired from their mothers. Youths with high PVL and any signs and symptoms associated with HTLV-1 infection should be closely monitored.

Manifestações cutâneas da infecção e das doenças relacionadas ao vírus linfotrópico de células T humanas do tipo 1

O vírus linfotrópico de células T humanas tipo 1 (HTLV-1) é um retrovírus encontrado em todo o mundo e, no Brasil, tem distribuição heterogênea com várias regiões consideradas de alta prevalência. Está relacionado com doenças graves e/ou incapacitantes, como a leucemia/linfoma de células T do adulto, com a doença neurológica conhecida como mielopatia associada ao HTLV-1/paraparesia espástica tropical, com a uveíte associada ao HTLV-1 e com a dermatite infecciosa. O risco para o aparecimento dessas doenças depende, principalmente, de fatores genéticos, da forma como a infecção foi adquirida e da carga proviral. Estima-se que até 10% dos infectados possam desenvolver alguma doença relacionada ao vírus ao longo da vida. O comprometimento da pele tem sido descrito tanto nas doenças relacionadas ao HTLV-1 quanto nos indivíduos portadores assintomáticos. Vários mecanismos são propostos para explicar as lesões da pele, seja pela presença direta do vírus em células, pela imunossupressão ou por resposta inflamatória que a infecção pelo vírus poderia desencadear. Dentre as manifestações dermatológicas mais freqüentes destacam-se a xerose, as dermatofitoses e as infecções bacterianas recorrentes. Neste artigo são revistos os principais aspectos referentes à infecção e às doenças relacionadas ao HTLV- 1, com ênfase na discussão das manifestações dermatológicas observadas nesse contexto.

Hematologic and biochemical changes associated with human T lymphotropic virus type 1 infection in Jamaica: a report from the population-based blood donors study

OBJECTIVE

We investigated changes in hematologic and biochemical parameters associated with human T lymphotropic virus type 1 (HTLV-1) infection, antibody titer, and provirus load. Additionally, on a subset of participants, we assessed the epidemiologic relationship of HTLV-1 with Strongyloides stercoralis.

METHODS

Among volunteer blood donors in Jamaica, HTLV-1 carriers (n=482) were frequency matched with HTLV-1 negative subjects (n=355) by age (+/-5 years), sex, and date of blood donation (+/-3 months). HTLV-1 antibody titer, provirus load, S. stercoralis IgG antibodies, complete blood cell count, blood chemistry, and urinalysis parameters were measured.

RESULTS

HTLV-1 carriers, compared with HTLV-1-negative individuals, had elevated levels of cleaved lymphocytes (24.5% vs. 16.4%), any lymphocyte abnormalities (atypical, cleaved, and reactive lymphocytes combined, 45.7% vs. 35.4%), and gamma-glutamyl transferase levels (21.2 vs. 19.6 IU/L), as well as lower eosinophil count (2.6% vs. 3.1%). Among carriers, HTLV-1 antibody titer (n=482) was inversely correlated with mean corpuscular volume (r=-0.10) and positively correlated with levels of total protein (r=0.16), phosphorus (r=0.12), and lactate dehydrogenase (r=0.24). HTLV-1-provirus load (n=326) was higher among carriers with cleaved lymphocytes and any lymphocyte abnormalities. Provirus load was inversely correlated with hemoglobin (r=-0.11), mean corpuscular volume (r=-0.15), neutrophil (r=-0.12), and eosinophil (r=-0.19) levels and was positively correlated with lactate dehydrogenase levels (r=0.12). Provirus load was significantly higher among male than female subjects. S. stercoralis antibodies were detected in 35 (12.1%) of 288 participants but were not associated with HTLV-1 status, antibody titer, or provirus load.

CONCLUSIONS

Markers of HTLV-1 infection (infection status, antibody titer, and provirus load) are associated with hematologic and biochemical alterations, such as lymphocyte abnormalities, anemia, decreased eosinophils, and elevated lactate dehydrogenase levels.