HTLV-2 horizontal and vertical transmission in a family from a Brazilian urban area: seroepidemiological, clinical and molecular study

Brazilian Protocol for Sexually Transmitted Infections 2020: human T-cell lymphotropic virus (HTLV) infection

This article addresses the Human T-lymphotropic virus (HTLV). This subject comprises the Clinical Protocol and Therapeutic Guidelines for Comprehensive Care for People with Sexually Transmitted Infections, published by the Brazilian Ministry of Health. HTLV-1/2 infection is a public health problem globally, and Brazil has the largest number of individuals living with the virus. HTLV-1 causes several clinical manifestations of neoplasm (adult T-cell leukemia/lymphoma) and inflammatory nature, such as HTLV-1-associated myelopathy and other manifestations such as uveitis, arthritis, and infective dermatitis. These pathologies have high morbidity and mortality and negatively impact the quality of life of infected individuals. This review includes relevant information for health authorities professionals regarding viral transmission, diagnosis, treatment, and monitoring of individuals living with HTLV-1 and 2 in Brazil. HTLV-1/2 transmission can occur through blood transfusion and derivatives, injectable drug use, organ transplantation, unprotected sexual intercourse, and vertical transmission.

The Epidemiological Impact of STIs among General and Vulnerable Populations of the Amazon Region of Brazil: 30 years of Surveillance

Sexually transmitted infections (STIs) represent a worldwide public health problem and, although many of them are curable, they continue to be neglected, especially in areas with a low human development index, such as in the northern region of Brazil. This review describes the results of 30 years of studies at the Virus Laboratory at the Federal University of Pará, including the prevalence and molecular epidemiology of HIV-1, HTLV-1/2, HPV, HBV, Treponema pallidum and Chlamydia trachomatis among urban and non-urban populations, and also in vulnerable groups in the Brazilian Amazon. Control strategies and challenges in preventing STIs are discussed considering this immense geographic region, where essential health services are unable to reach the entire population, especially the most vulnerable, such as female sex workers, people who use illicit drugs, remnants of quilombolos and indigenous communities.

[Brazilian Protocol for Sexually Transmitted Infections 2020: human T cell lymphotropic virus (HTLV) infection]

This manuscript is related to the chapter about human T-cell lymphotropic virus (HTLV) that is part of the Clinical Protocol and Therapeutic Guidelines for Comprehensive Care for People with Sexually Transmitted Infections, published by the Brazilian Health Ministry. HTLV-1/2 infection is a worldwide public health problem and Brazil has the largest number of individuals living with the virus. HTLV-1 causes a variety of clinical manifestations of a neoplastic nature, such as adult leukemia/T-cell lymphoma, and also of an inflammatory nature, such as HTLV-1-associated myelopathy, as well as other manifestations such as uveitis, arthritis and infective dermatitis. These pathologies have high morbidity and mortality and negatively impact the quality of life of infected individuals. This review includes relevant information for health service managers and workers regarding virus transmission modes, diagnosis, treatment and monitoring of individuals living with HTLV-1 and 2 in Brazil.

HTLV-2 infection in Manaus, Brazil: first description of HTLV-2c subtype in an urban area of the Western Amazon region

INTRODUCTION

We investigated the prevalence of human T-cell lymphotropic virus types 1 and 2 (HTLV-1/2) infection in patients with hematological diseases from the western Amazon region of Brazil.

METHODS

Samples from 306 patients were submitted for the molecular diagnosis of HTLV-1/2 infection by real time PCR (qPCR), with amplification, sequencing, and phylogenetic analysis of the long terminal repeat (LTR) region.

RESULTS

A 29-year-old male carrier of sickle cell anemia with a history of multiple blood transfusions was diagnosed with the HTLV-2c subtype.

CONCLUSIONS

This study describes the first known occurrence of HTLV-2c in the urban area of Brazil's western Amazon region.

HTLV in South America: Origins of a silent ancient human infection

The description of the first human retrovirus, human T-lymphotropic virus 1 (HTLV-1), was soon associated with an aggressive lymphoma and a chronic inflammatory neurodegenerative disease. Later, other associated clinical manifestations were described, affecting diverse target organs in the human body and showing the enormous burden carried by the virus and the associated diseases. The epidemiology of HTLV-1 and HTLV-2 showed that they were largely distributed around the world, although it is possible to locate geographical areas with pockets of low and very high prevalence and incidence. Aboriginal Australians and indigenous peoples of Brazil are examples of the large spread of HTLV-1 and HTLV-2, respectively. The epidemiological link of both situations is their occurrence among isolated, epidemiologically closed or semi-closed communities. The origin of the viruses in South America shows two different branches with distinct timing of entry. HTLV-1 made its probable entrance in a more recent route through the east coast of Brazil at the beginning of the slave trade from the African continent, starting in the 16th century and lasting for more than 350 years. HTLV-2 followed the ancient route of human migration from the Asian continent, crossing the Behring Strait and then splitting in South America as the population became separated by the Andes Mountains. By that time, HTLV-2c probably arose and became isolated among the indigenous populations in the Brazilian Amazon. The study of epidemiologically closed communities of indigenous populations in Brazil allowed tracing the most likely route of entry, the generation of a new molecular subtype (HTLV-2c), the elucidation of the vertical transmission of HTLV-2, the intrafamilial aggregation of cases and the escape and spread of the virus to other areas in Brazil and abroad. Despite the burden and impact of both viruses, they are maintained as silent infections among human populations because 1, health authorities in most South American countries in which national surveillance is poor have little interest in the disease, 2, the information is commonly lost as indigenous groups do not have specific policies for HTLV and other sexually transmitted infections, and 3, health access is not feasible or properly delivered.

Phenotypic and functional changes in gamma delta T lymphocytes from HTLV-1 carriers

Human T-cell lymphotropic virus type-1 (HTLV-1) is the etiologic agent of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), which is a chronic inflammatory disease that leads to gradual loss of motor movement as a result of the death of spinal cord cells through immune mediated mechanisms. The risk to develop HAM/TSP disease positively correlates with the magnitude of HTLV-1 proviral load. Gamma-delta T lymphocytes have been recognized as important players in a variety of infectious diseases. Therefore, we have investigated interactions between HTLV-1 infection and γδ T lymphocytes during HAM/TSP. Similar frequencies of total γδ T lymphocytes and their Vγ9δ2⁺ and Vγ9δ2^neg subpopulations were observed in HAM/TSP patients. However, T lymphocytes obtained from HTLV-1 carriers displayed significantly higher rates of spontaneous proliferation and NKp30 expression when compared to cells from uninfected donors. In addition, an important decrease in the frequency of granzyme B⁺ γδ T lymphocytes (approximately 50%) was observed in HAM/TSP patients. Higher proportion of IFN-γ⁺ γδ T lymphocytes was found in HTLV-1-infected patients, which positively correlated with the HTLV-1 proviral load in peripheral blood mononuclear cells. Collectively, our data indicates that HTLV-1 infection leads to phenotypic and functional changes in the population of γδ T lymphocyte population, suggesting that HTLV-1 infection modulates functions associated to these cells, which might be involved in controlling the infection or in the development of HTLV-1-associated diseases.

Mother-to-Child HTLV-1 Transmission: Unmet Research Needs

Mother-to-child transmission (MTCT) of Human T-cell lymphotropic virus type 1 (HTLV-1) causes lifelong infection. At least 5–10 million individuals worldwide are currently living with HTLV-1. Studies of regional variation are required to better understand the contribution of MTCT to the global burden of infection. Although most infected individuals remain asymptomatic ∼10% develop high morbidity, high mortality disease. Infection early in life is associated with a higher risk of disease development. Adult T-cell leukemia (ATL), which is caused by HTLV-1 and has a median survival of 8 months is linked to MTCT, indeed evidence of ATL following infection as an adult is sparse. Infective dermatitis also only occurs following neonatal infection. Whilst HTLV-1-associated myelopathy (HAM) follows sexual and iatrogenic infection approximately 30% of patients presenting with HAM/TSP acquired the infection through their mothers. HAM/TSP is a disabling neurodegenerative disease that greatly impact patient’s quality of life. To date there is no cure for HTLV-1 infection other than bone marrow transplantation for ATL nor any measure to prevent HTLV-1 associated diseases in an infected individual. In this context, prevention of MTCT is expected to contribute disproportionately to reducing both the incidence of HTLV-1 and the burden of HTLV-1 associated diseases. In order to successfully avoid HTLV-1 MTCT, it is important to understand all the variables involved in this route of infection. Questions remain regarding frequency and risk factors for in utero peri-partum transmission whilst little is known about the efficacy of pre-labor cesarean section to reduce these infections. Understanding the contribution of peripartum infection to the burden of disease will be important to gauge the risk-benefit of interventions in this area. Few studies have examined the impact of HTLV-1 infection on fertility or pregnancy outcomes nor the susceptibility of the mother to infection during pregnancy and lactation. Whilst breast-feeding is strongly associated with transmission and avoidance of breast-feeding a proven intervention little is known about the mechanism of transmission from the breast milk to the infant and there have been no clinical trials of antiretroviral therapy (ARV) to prevent this route of transmission.

Estimation of HTLV-1 vertical transmission cases in Brazil per annum

Background

Brazil has at least 800,000 HTLV-1 infected individuals. HTLV-1 can be transmitted via sexual intercourse, contact with blood and from mother to child, mainly by breastfeeding. Treatments for the high morbidity/mortality associated diseases (ATL and HAM/TSP) are limited, therefore, infection prevention is of utmost importance. However, antenatal screening is not routinely performed in Brazil. A lack of data regarding the number of individuals infected via breastfeeding impairs the development of government policies. The objective is to estimate the number of HTLV-1 infections occurring annually due to mother to child transmission (MTCT) in Brazil, nationally and regionally.

Methodology

To estimate HTLV-1 MTCT in Brazil the following variables are modelled: number of births, prevalence of HTLV-1 infection in pregnant women, breastfeeding duration rate and transmission risk according to breastfeeding period. The number of cases of HAM/TSP and ATL attributable to MTCT are also estimated.

Principal findings

In 2008, there were 2,934,828 live births in Brazil. HTLV prevalence in pregnant women in Brazil ranges between 0.1–1.05% by region. An estimated 16,548 HTLV-1 infected women are pregnant each year. According to the breastfeeding pattern and HTLV-1 prevalence of each region there are an estimated 3,024 new cases of HTLV-1 infection due to MTCT annually of which 2,610 are preventable through infant feeding advice. These 3,024 transmissions will result in 120–604 cases of ATL and 8–272 of HAM/TSP. North-East region comprises the high number of MTCT cases, followed by South-East.

Conclusions/significance

A high number of new HTLV-1 infections due to MTCT occur every year in Brazil. Antenatal screening and avoiding breastfeeding are essential to prevent subsequent development of HTLV-1-associated diseases.

The human T-cell lymphotropic virus type 1 (HTLV-1) causes lifelong infection in humans. Although most infected individuals remain asymptomatic HTLV-1 causes severe disease in at least 5% of carriers. In the present study we estimate the number of HTLV-1 infections that occur annually due to mother to child transmission (MTCT) in Brazil and within its regions. The high number of estimated cases due to MTCT (3,024) which will give rise in adult life to HTLV-1associated diseases suggest the importance of performing HTLV-1 antenatal screening in Brazil to reduce the dissemination of this infection and to thus prevent a blood cancer to which most individuals succumb within 8 months of presentation and in others a disabling disease of the spinal cord.

HTLV-1 and -2 in a first-time blood donor population in Northeastern Brazil: Prevalence, molecular characterization, and evidence of intrafamilial transmission

Independent epidemiology for respective human T-cell lymphotropic virus (HTLV) types 1 and 2 is little known in blood donors in Brazil, where screening for HTLV-1/2 is mandatory at blood banks, but no testing to confirm/differentiate these viruses. Therefore, this study aims to assess the prevalence of HTLV-1 and -2 in a first-time blood donor population in Northeastern Brazil and to carry out molecular characterization of respective isolates. A cross-sectional study was conducted at the State Blood Bank in Piauí. Samples were screened for anti-HTLV-1/2 by enzyme immunoassay, and reactive samples were confirmed using a line immunoassay and polymerase chain reaction (PCR). Of 37 306 blood donors, 47 were anti-HTLV-1/2 reactive by enzyme immunoassay. After confirmed by line immunoassay, 22 were positive for HTLV-1 (0.59 per 1000; 95% CI: 0.38-0.87), 14 were positive for HTLV-2 (0.37 per 1000; 95% CI: 0.21-0.61), 1 was indeterminate, and the remaining donors were negative. The HTLV-1 infection was also confirmed by PCR in all anti-HTLV-1-positive samples, and sequencing classified these isolates as belonging to the Transcontinental (A) subgroup of the Cosmopolitan (1a) subtype. Of 14 anti-HTLV-2-positive samples, 11 were also PCR positive, which belonged to subtype a (HTLV-2a/c). In addition, 38 family members of 5 HTLV-1- and 3 HTLV-2-infected donors were analyzed. Familial transmission of HTLV-1 and -2 was evidenced in 3 families. In conclusion, in Northeastern Brazil, where HTLV-1 and -2 are endemic, counseling blood donor candidates and their families might play a key role in limiting the spread of these viruses.

Infectious Agents As Markers of Human Migration toward the Amazon Region of Brazil

Infectious agents are common companions of humans and since ancient times they follow human migration on their search for a better place to live. The study of paleomicrobiology was significantly improved in its accuracy of measurement with the constant development of better methods to detect and analyze nucleic acids. Human tissues are constantly used to trace ancient infections and the association of anthropological evidences are important to confirm the microbiological information. Infectious agents which establish human persistent infections are particularly useful to trace human migrations. In the present article, the evidence of infection by viral agents such as human T-lymphotropic virus 1, human T-lymphotropic virus 2, human herpes virus-8, JC virus, and a bacterium, Chlamydia trachomatis, was described using different methodologies for their detection. Their presence was further used as biomarkers associated with anthropological and other relevant information to trace human migration into the Amazon region of Brazil. The approach also evidenced their microbiological origin, emergence, evolution, and spreading. The information obtained confirms much of the archeological information available tracing ancient and more recent human migration into this particular geographical region. In this article, the paleomicrobiological information on the subject was summarized and reviewed.