The epidemiology of human retrovirus-associated illnesses

Therapeutic advances for the management of adult T cell leukemia: Where do we stand?

Adult T cell leukemia (ATL) is an aggressive blood malignancy secondary to chronic infection with the human T cell leukemia virus type I (HTLV-1) retrovirus. ATL encompasses four subtypes (acute, lymphoma, chronic, and smoldering), which exhibit different clinical characteristics and respond differently to various treatment strategies. Yet, all four subtypes are characterized by a dismal long-term prognosis and a low survival rate. While antiretroviral therapy improves overall survival outcomes in smoldering and chronic subtypes, survival remains poor in lymphoma subtypes despite their good response to intensive chemotherapy. Nonetheless, acute ATL remains the most aggressive form associated with profound immunosuppression, chemo-resistance and dismal prognosis. Targeted therapies such as monoclonal antibodies, epigenetic therapies, and arsenic/IFN, emerged as promising therapeutic approaches in ATL. Allogeneic hematopoietic cell transplantation is the only potentially curative modality, alas applicable to only a small percentage of patients. The recent findings demonstrating the expression of the viral oncoprotein Tax in primary ATL cells from patients with acute or chronic ATL, albeit at low levels, and their dependence on continuous Tax expression for their survival, position ATL as a virus-addicted leukemia and validates the rationale of anti-viral treatment strategies. This review provides a comprehensive overview on conventional, anti-viral and targeted therapies of ATL, with emphasis on Tax-targeted therapied in the pre-clinical and clinical settings.

Current State of Therapeutics for HTLV-1

Human T cell leukaemia virus type-1 (HTLV-1) is an oncogenic retrovirus that causes lifelong infection in ~5-10 million individuals globally. It is endemic to certain First Nations populations of Northern and Central Australia, Japan, South and Central America, Africa, and the Caribbean region. HTLV-1 preferentially infects CD4+ T cells and remains in a state of reduced transcription, often being asymptomatic in the beginning of infection, with symptoms developing later in life. HTLV-1 infection is implicated in the development of adult T cell leukaemia/lymphoma (ATL) and HTLV-1-associated myelopathies (HAM), amongst other immune-related disorders. With no preventive or curative interventions, infected individuals have limited treatment options, most of which manage symptoms. The clinical burden and lack of treatment options directs the need for alternative treatment strategies for HTLV-1 infection. Recent advances have been made in the development of RNA-based antiviral therapeutics for Human Immunodeficiency Virus Type-1 (HIV-1), an analogous retrovirus that shares modes of transmission with HTLV-1. This review highlights past and ongoing efforts in the development of HTLV-1 therapeutics and vaccines, with a focus on the potential for gene therapy as a new treatment modality in light of its successes in HIV-1, as well as animal models that may help the advancement of novel antiviral and anticancer interventions.

Prevalence and characteristics of HTLV-associated uveitis in patients from Bahia, an endemic area for HTLV - 1 in Brazil

BACKGROUND

HTLV-1-associated uveitis (HAU) is an inflammatory reaction of the choroid, retina, optic nerve and vitreous that can lead to vision impairment. The worldwide prevalence of HAU varies widely.

OBJECTIVE

To determine the prevalence of HAU in patients from Salvador, Bahia-Brazil, and describe uveitis type and associated symptoms.

METHODS

Cross-sectional analytical study to determine the prevalence of uveitis in HTLV-1-infected patients recruited in Bahia, Brazil, a region considered endemic for HTLV-1. Patients were enrolled at a local reference center for HTLV (infected) and at an outpatient ophthalmology clinic (noninfected group). All patients were examined by the same ophthalmologist following a single protocol. Prevalence ratios (PR) were calculated.

RESULTS

A total of 168 consecutively examined HTLV-1-infected patients and 410 noninfected patients (randomly selected) were included. Females predominated (82.1%) in the HTLV-1-infected group (versus 64.4% in the uninfected group) (p < 0.001). The mean age of infected and uninfected patients was 53.2 and 62.8 years, respectively (p < 0.001). The prevalence of uveitis in HTLV-1+ and HTLV-1- patients was 7.14% and 0.73%, respectively (PR = 9.76; 95CI%:2.79-34.15; p < 0.01). Bilateral intermediate uveitis, associated with symptoms including visual disturbances and floaters, was most commonly identified in the HTLV-1-infected patients, whereas unilateral anterior uveitis, in association with symptoms such as blurring and ocular pain, was more common in the uninfected group.

CONCLUSION

The prevalence of uveitis in patients with HTLV-1 was markedly higher than in uninfected subjects. HAU patients were mostly asymptomatic and exhibited bilateral presentation, with uveitis more frequently localized in the intermediate chamber.

Primary cells from patients with adult T cell leukemia/lymphoma depend on HTLV-1 Tax expression for NF-κB activation and survival

Adult T cell leukemia/lymphoma (ATL) is an aggressive malignancy secondary to chronic infection with human T cell leukemia virus type 1 (HTLV-1). The viral oncoprotein Tax initiates T cell transformation through activation of critical cellular pathways, including NF-κB. Unexpectedly, Tax protein is not detectable in most ATL cells, in contrast to the HTLV-1 HBZ protein which antagonizes Tax effects. Here, we demonstrate that primary ATL cells from patients with acute or chronic ATL express very low levels of Tax mRNA and protein. Critically, survival of these primary ATL cells is dependent on continued Tax expression. Mechanistically, Tax extinction results in reversal of NF-κB activation, P53/PML activation and apoptosis. Tax drives interleukin-10 (IL-10) expression and recombinant IL-10 rescues the survival of tax-depleted primary ATL cells. These results demonstrate the critical role of continued Tax and IL-10 expression for the survival of primary ATL cells, highlighting their relevance as therapeutic targets.

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

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

Interplay between innate immunity and the viral oncoproteins Tax and HBZ in the pathogenesis and therapeutic response of HTLV-1 associated adult T cell leukemia

The Human T-cell Leukemia virus type 1 (HTLV-1) causes an array of pathologies, the most aggressive of which is adult T-cell leukemia (ATL), a fatal blood malignancy with dismal prognosis. The progression of these diseases is partly ascribed to the failure of the immune system in controlling the spread of virally infected cells. HTLV-1 infected subjects, whether asymptomatic carriers or symptomatic patients are prone to opportunistic infections. An increasing body of literature emphasizes the interplay between HTLV-1, its associated pathologies, and the pivotal role of the host innate and adoptive immune system, in shaping the progression of HTLV-1 associated diseases and their response to therapy. In this review, we will describe the modalities adopted by the malignant ATL cells to subvert the host innate immune response with emphasis on the role of the two viral oncoproteins Tax and HBZ in this process. We will also provide a comprehensive overview on the function of innate immunity in the therapeutic response to chemotherapy, anti-viral or targeted therapies in the pre-clinical and clinical settings.

Adult T-Cell Leukemia: a Comprehensive Overview on Current and Promising Treatment Modalities

PURPOSE OF THE REVIEW

Adult T-cell leukemia (ATL) is an aggressive chemo-resistant malignancy secondary to HTLV-1 retrovirus. Prognosis of ATL remains dismal. Herein, we emphasized on the current ATL treatment modalities and their drawbacks, and opened up on promising targeted therapies with special focus on the HTLV-1 regulatory proteins Tax and HBZ.

RECENT FINDINGS

Indolent ATL and a fraction of acute ATL exhibit long-term survival following antiviral treatment with zidovudine and interferon-alpha. Monoclonal antibodies such as mogamulizumab improved response rates, but with little effect on survival. Allogeneic hematopoietic cell transplantation results in long-term survival in one third of transplanted patients, alas only few patients are transplanted. Salvage therapy with lenalidomide in relapsed/refractory patients leads to prolonged survival in some of them. ATL remains an unmet medical need. Targeted therapies focusing on the HTLV-1 viral replication and/or viral regulatory proteins, as well as on the host antiviral immunity, represent a promising approach for the treatment of ATL.

A novel high performing multiplex immunoassay Multi-HTLV for serological confirmation and typing of HTLV infections

Background

Human T-Cell Lymphotropic Viruses (HTLV) type 1 and type 2 account for an estimated 5 to 10 million infections worldwide and are transmitted through breast feeding, sexual contacts and contaminated cellular blood components. HTLV-associated syndromes are considered as neglected diseases for which there are no vaccines or therapies available, making it particularly important to ensure the best possible diagnosis to enable proper counselling of infected persons and avoid secondary transmission. Although high quality antibody screening assays are available, currently available confirmatory tests are costly and have variable performance, with high rates of indeterminate and non-typable results reported in many regions of the world. The objective of this project was to develop and validate a new high-performance multiplex immunoassay for confirmation and discrimination of HTLV-1 and HTLV-2 strains.

Methodology/Principal findings

The multiplex platform was used first as a tool to identify suitable antigens and in a second step for assay development. With data generated on over 400 HTLV-positive blood donors sourced from USA and French blood banks, we developed and validated a high-precision interpretation algorithm. The Multi-HTLV assay demonstrated very high performance for confirmation and strain discrimination with 100% sensitivity, 98.1% specificity and 100% of typing accuracy in validation samples. The assay can be interpreted either visually or automatically with a colorimetric image reader and custom algorithm, providing highly reliable results.

Conclusions/Significance

The newly developed Multi-HTLV is very competitive with currently used confirmatory assays and reduces considerably the number of indeterminate results. The multiparametric nature of the assay opens new avenues to study specific serological signatures of each patient, follow the evolution of infection, and explore utility for HTLV disease prognosis. Improving HTLV diagnostic testing will be critical to reduce transmission and to improve monitoring of seropositive patients.

HTLV viruses are responsible for more than 10 million cases of infection worldwide. The infection is considered as a neglected disease due to lack of vaccines and treatments. Accurate diagnosis is crucial for counselling infected persons and prevention of secondary transmissions. In spite of the development of excellent serological screening assays, many cases of indeterminate and untyped results are still regularly reported and their infection status remain uncertain. To address the need of more precise diagnosis, we have developed a new cutting-edge in-vitro diagnostic confirmation test, named Multi-HTLV, which has been validated on a large panel of HTLV samples. The test is a multiplex immunoassay allowing powerful detection of antibodies against HTLV through combination of a set of selective and validated virus-specific antigens in a blood sample. The Multi-HTLV assay increases the reliability of HTLV diagnostics and strain typing thanks to a high precision mathematical algorithm.

Reviewing Antiviral Research Against Viruses Causing Human Diseases - A Structure Guided Approach

The littlest of all the pathogens, viruses have continuously been the foremost strange microorganisms to consider. Viral Infections can cause extreme sicknesses as archived by the HIV/AIDS widespread or the later Ebola or Zika episodes. Apprehensive framework distortions are too regularly watched results of numerous viral contaminations. Besides, numerous infections are oncoviruses, which can trigger different sorts of cancer. Nearly every year a modern infection species rises debilitating the world populace with an annihilating episode. Subsequently, the need of creating antivirals to combat such rising infections. In any case, from the innovation of to begin with antiviral medicate Idoxuridine in 1962 to the revelation of Baloxavir marboxil (Xofluza) that was FDA-approved in 2018, the hone of creating antivirals has changed significantly. In this article, different auxiliary science strategies have been described that can be referral for therapeutics innovation.

CD30-positive lymphomatous (nonleukemic) variant of adult T-cell leukemia/lymphoma, HTLV-1 associated

Nonleukemic variant of HTLV-1-associated adult T-cell leukemia lymphoma (ATLL) is a rare variant, and herein, we describe a case with strong and diffuse positivity of neoplastic cells for CD30. Even though ATLL is aggressive entity with poor prognosis, in our case, there was very good clinical response achieved with brentuximab-containing regimen. Therefore, HTLV-1-associated ATLL can be included in the differential diagnostic approach of CD30-positive lymphoproliferative disorders.

Interaction of perforin and granzyme B and HTLV-1 viral factors is associated with Adult T cell Leukemia development

Objective(s):

Human T cell leukaemia virus type 1 (HTLV-1) is associated with adult T cell leukaemia (ATL), a malignant lymphoproliferative disease that infects CD4 T cells. It is not clear why the majority of HTLV-1-infected individuals remain asymptomatic carries (ACs) and a minority develop ATL. Cellular immune response has a critical role in ATL and destroys malignant and HTLV-1-infected cells. Perforin and granzyme have important functional roles in apoptosis and destruction of infected cells. In the present study we examined the role of perforin and granzyme in ATL patients and ACs.

Materials and Methods:

Peripheral blood mononuclear cells (PBMCs) were isolated from ATL patients and ACs by using Ficoll-hypaque density centrifugation. RNA was extracted and cDNA was synthesized. A real-time PCR TaqMan method was designed and optimized for evaluation of perforin, granzyme, tax, and HBZ gene expression. HTLV-1 proviral load (PVL) was quantified in patients with ATL and ACs.

Results:

The mRNA expression of tax and HBZ was significantly higher in ATL patients than ACs (P=0.011 and P=0.0001,respectively). The HTLV-1 PVL was higher in ATL patients compared to with AC group (P=0.015). There was a significant increase in perforin gene expression in ACs compared with ATL patients (P=0.002). Furthermore, the expression of granzyme was also higher in ACs compared with ATL patients, and significant differences were observed between the two groups (P=0.036).

Conclusion:

Low expression of perforin and granzyme in ATL patients seems to influence the efficiency of CTL function and destruction of HTLV-1-infected cells, which might contribute to the disease pathogenesis.

Novel Treatments of Adult T Cell Leukemia Lymphoma

Adult T cell leukemia-lymphoma (ATL) is an aggressive malignancy secondary to chronic infection with the human T cell leukemia virus type I (HTLV-I) retrovirus. ATL carries a dismal prognosis. ATL classifies into four subtypes (acute, lymphoma, chronic, and smoldering) which display different clinical features, prognosis and response to therapy, hence requiring different clinical management. Smoldering and chronic subtypes respond well to antiretroviral therapy using the combination of zidovudine (AZT) and interferon-alpha (IFN) with a significant prolongation of survival. Conversely, the watch and wait strategy or chemotherapy for these indolent subtypes allies with a poor long-term outcome. Acute ATL is associated with chemo-resistance and dismal prognosis. Lymphoma subtypes respond better to intensive chemotherapy but survival remains poor. Allogeneic hematopoietic stem cell transplantation (HSCT) results in long-term survival in roughly one third of transplanted patients but only a small percentage of patients can make it to transplant. Overall, current treatments of aggressive ATL are not satisfactory. Prognosis of refractory or relapsed patients is dismal with some encouraging results when using lenalidomide or mogamulizumab. To overcome resistance and prevent relapse, preclinical or pilot clinical studies using targeted therapies such as arsenic/IFN, monoclonal antibodies, epigenetic therapies are promising but warrant further clinical investigation. Anti-ATL vaccines including Tax peptide-pulsed dendritic cells, induced Tax-specific CTL responses in ATL patients. Finally, based on the progress in understanding the pathophysiology of ATL, and the risk-adapted treatment approaches to different ATL subtypes, treatment strategies of ATL should take into account the host immune responses and the host microenvironment including HTLV-1 infected non-malignant cells. Herein, we will provide a summary of novel treatments of ATL in vitro, in vivo, and in early clinical trials.

Seroprevalence of human T-lymphotropic virus HTLV and its associated factors in donors of a blood bank of Medellín-Colombia, 2014-2018

BACKGROUND

Research on HTLV in Colombia is limited; despite being an endemic country there are few studies on the magnitude of this infection. The aim of this study was to determine the seroprevalence of HTLV I/II and its associated factors in donors to a blood bank of Medellín Colombia, 2014-2018.

METHODS

This is a cross-sectional study of 52,159 donors with a secondary information source. Seroprevalence of HTLV I/II was determined with its confidence interval and the population characteristics were described by frequency and summary measures. To explore the associated factors, Pearson's Chi square test, Mann-Whitney U test, crude odds ratios were used and they were adjusted by logistic regression in SPSS 25.0.

RESULTS

88% of the population lived in the metropolitan area, 68.5% belonged to the University. 76.2% were altruistic donors (unpaid donors who did not donate to a specific patient). 24.5% were repetitive (paid) donors. 75% of the donors were under 41 years old. The seroprevalence of HTLV I/II was 0.176% (95% CI = 0.139% -0.213%), being statistically lower in repetitive donors and men.

CONCLUSION

The seroprevalence of HTLV I/II infection in the studied blood bank is lower than that reported in other blood banks at the departmental and national levels. In Medellín, it was associated with the frequency of donation and gender, which is useful information for the hemovigilance programs of the city.

Seroprevalence of viral infections in captive rhesus and cynomolgus macaques

Macaques serve as important animal models for biomedical research. Viral infection of macaques can compromise animal health as well as the results of biomedical research, and infected animals constitute an occupational health risk. Therefore, monitoring macaque colonies for viral infection is an important task. We used a commercial chip-based assay to analyze sera of 231 macaques for the presence of antibody responses against nine animal and human viruses. We report high seroprevalence of cytomegalovirus (CMV), lymphocryptovirus (LCV), rhesus rhadinovirus (RRV) and simian foamy virus (SFV) antibodies in all age groups. In contrast, antibodies against simian retrovirus type D (SRV/D) and simian T cell leukemia virus (STLV) were detected only in 5 % and 10 % of animals, respectively, and were only found in adult or aged animals. Moreover, none of the animals had antibodies against herpes B virus (BV), in keeping with the results of in-house tests previously used for screening. Finally, an increased seroprevalence of measles virus antibodies in animals with extensive exposure to multiple humans for extended periods of time was observed. However, most of these animals were obtained from external sources, and a lack of information on the measles antibody status of the animals at the time of arrival precluded drawing reliable conclusions from the data. In sum, we show, that in the colony studied, CMV, LCV, RRV and SFV infection was ubiquitous and likely acquired early in life while SRV/D and STLV infection was rare and likely acquired during adulthood.

[Primary cutaneous localization revealing leukemia/T-cell lymphoma associated with chronic HTLV-1 infection in a adult. A case presentation]

Adult T-cell leukemia/lymphoma (ATLL) is a rare medical condition and a diagnosis that ought to be considered for patients living in an area endemic for the HTLV-1 virus (human T-lymphotrophic virus) where a T-cell lymphoproliferative diagnosis has been made. The cutaneous clinical forms may be the first manifestation of the disease. We report here an observation in a 60-year-old Senegalese woman whose skin lesions were sampled to reveal the ATLL immunophenotypic profile CD4+, CD25+, FoxP3-, and CD7-. HTLV-1 seropositivity confirmed the histopathological diagnosis, and should be corroborated by demonstration of a molecular clonal rearrangement by PCR (Polymerase Chain Reaction). This is a problem because such techniques are not always available in Africa.

Cognitive impairment is frequent among symptomatic carriers of human T-cell lymphotropic virus type 1 (HTLV-1), regardless of their clinical status

The main goal of this study was to investigate the presence of cognitive impairment in patients infected with HTLV-1 presenting or not TSP/HAM.

METHODS

Cross-sectional study including 104 participants: 37 asymptomatic HTLV-1 carriers, 37 patients diagnosed with TSP/HAM and 30 HTLV-1 negative control patients. Within the HTLV-1 positive group, 53 were female and 21 were male, the average age was 46 (SD=13.5) and the average schooling time was 7.7years (SD=3.3).The sociodemographic variables (genre, age and education) were compared between the three groups. The assessment tools used were: Beck Depression Inventory, Lawton's Activities of Daily Life Scale and a complete neuropsychological battery. The application of these assessment tools was carried out in blind. Both HTLV-1 asymptomatic subjects and HAM/TSP patients showed a lower performance on neuropsychological tests and higher depression scores when compared to the control group. HTLV-1 patients performed poorly in several cognitive domains, but only fluid intelligence, estimated intellectual functioning, immediate and delayed recall of visual memory and information processing speed (in the specific case of patients with TSP/HAM) reached statistical significance when compared with controls. Depression was not associated with cognitive impairment. HTLV-1 carriers presented a higher frequency of cognitive impairment than normal controls.

[Diffuse interstitial lung disease revealing adult T-Cell leukemia/lymphoma (HTLV-1)]

La leucémie/lymphome à cellules T de l'adulte est une prolifération tumorale de cellules lymphoïdes T matures activées, dont l'agent étiologique est le rétrovirus humain T cell-leukemia virus type 1, ce virus entraine rarement des désordres inflammatoires bronchioloalveolaires. Nous rapportons l'observation d'un patient hospitalisé pour une pneumopathie interstitielle diffuse et dont le bilan étiologique a révélé une leucémie lymphome à cellules T de l'adulte HTLV1+.

High Prevalences and a Wide Genetic Diversity of Simian Retroviruses in Non-human Primate Bushmeat in Rural Areas of the Democratic Republic of Congo

Like the majority of emerging infectious diseases, HIV and HTLV are of zoonotic origin. Here we assess the risk of cross-species transmissions of their simian counterparts, SIV and STLV, from non-human primates (NHP) to humans in the Democratic Republic of Congo (DRC). A total of 331 samples, derived from NHP bushmeat, were collected as dried blood spots (DBS, n = 283) or as tissue samples (n = 36) at remote forest sites mainly in northern and eastern DRC. SIV antibody prevalences in DBS were estimated with a novel high throughput immunoassay with antigens representing the actual known diversity of HIV/SIV lineages. Antibody-positive samples were confirmed by PCR and sequence analysis. Screening for STLV infection was done with universal primers in tax, and new strains were further characterized in LTR. SIV and STLV infection in tissue samples was done by PCR only. Overall, 5 and 15.4% of NHP bushmeat was infected with SIV and STLV, respectively. A new SIV lineage was identified in Allen's swamp monkeys (Allenopithecus nigroviridis). Three new STLV-1 subtypes were identified in Allen's swamp monkeys (Allenopithecus nigroviridis), blue monkeys (Cercopithecus mitis), red-tailed guenons (Cercopithecus ascanius schmidti) and agile mangabeys (Cercocebus agilis). SIV and STLV prevalences varied according to species and geographic region. Our study illustrates clearly, even on a small sample size from a limited number of geographic areas, that our knowledge on the genetic diversity and geographic distribution of simian retroviruses is still limited and that humans continue to be exposed to relative high proportions on infected NHP bushmeat.

Human T-cell lymphotropic virus-1 infection: three infected generations in the same family

The human T-cell lymphotropic virus-1 (HTLV-1) affects worldwide population; the estimated number of currently infected individuals is 10-20 million. In this report, we describe the clinical findings of three family members with vertical transmission of HTLV-1. This case report highlights the importance of healthcare providers who have optimal knowledge about HTLV-1 including its transmission and pertinent attributes, and who are able to provide affected individuals with adequate information regarding their condition.

Evaluation of human T-lymphotropic virus prevalence/co-infection rates for a four-year period in a non-metropolitan blood center in Southeast Brazil

INTRODUCTION

Human T-lymphotropic virus types 1/2 (HTLV-1/2) are distributed worldwide and are endemic in specific regions.

METHODS

Serological evaluation of the HTLV-1/2 prevalence and co-infection rate [human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), Chagas disease, and syphilis)] for 2011-2014 was performed with volunteer blood donors from the western part of São Paulo State.

RESULTS

Serrana and Araçatuba had higher HTLV seroprevalence rates (0.1%); while Franca, Olimpia, and Bebedouro had lower seroprevalences (0.04%). Co-infection (HBV and syphilis) was present in 12.3% of HTLV-infected blood donors.

CONCLUSIONS

Our findings provide data for the prevalence of HTLV in Brazil and demonstrate the importance of regional and global hemovigilance.

Indigenous tropical spastic paraparesis in Madrid (Spain). Experience on screening of human T-lymphotropic virus

We have recently documented a case of tropical spastic paraparesis by HTLV-I in a Spanish patient. HTLV-I infection is rare in Europe, and hardly ever is accompanied by symptoms, but if it does it could trigger a major health issue. This case is presented here, as well as a discussion on the situations in which HTLV-I detection is justified. An analysis was made of the HTLV diagnostic requests at our centre during 2014-2015 (n=123). The diagnostic algorithm was: 1) Enzyme immunoassay, 2) Reverse hybridization, and 3) Proviral DNA detection by PCR. The results showed several situations of HTLV screening, emphasising those related to paraparesis (22%). Seven cases of HTLV-I infection were found: five in patients from endemic regions, one in an HIV-infected patient, and the case of TSP mentioned above. HTLV-I surveillance in non-endemic regions is a challenging issue, as the cost-benefit ratio is not well-established. This case report emphasises the importance of including HTLV within the differential diagnosis of insidious spastic paraparesis.

HTLV-1 and leukemogenesis: virus-cell interactions in the development of adult T-cell leukemia

Human T-cell lymphotropic virus type 1 (HTLV-1) was originally discovered in the early 1980s. It is the first retrovirus to be unambiguously linked causally to a human cancer. HTLV-1 currently infects approximately 20 million people worldwide. In this chapter, we review progress made over the last 30 years in our understanding of HTLV-1 infection, replication, gene expression, and cellular transformation.

[Serological diagnosis of HTLV-1/2: combination of screening assays to define the serological status in blood donors]

Alternative algorithms were evaluated in order to reduce the number of false reactive results for antibodies against HTLV-1/2. From 20,210 samples tested, 0.37% (74/20,210) was reactive by ELISA Murex. Of these, 23 were confirmed as positive by the indirect immunofluorescence assay whereas 51 were negative, being the positive predictive value (PPV) 31.08%. From a combination of the ELISA Murex assay with the particle agglutination assay (PA) and ELISA MP, the following results were obtained: 26/74 were reactive by ELISA Murex and PA, PPV 88.5% and 32/74 were reactive by ELISA Murex and ELISA MP, PPV 71.8 %. The ROC curve analysis determined that for an RP 4.74, the values for sensitivity, specificity, PPV and NPV by ELISA Murex were 100%, 98.04%, 95.8% and 100%, respectively. We propose that reactive samples by ELISA Murex with an RP d 4.74 should be retested in duplicate by PA, and the resulting concordantly nonreactive samples should be defined as negative for HTLV-1/2.

HTLV-I infection in the South West Indian Ocean islands, particularly in La Réunion and the Seychelles

Data on HTLV-I are scarce in several Southwest Indian Ocean islands except for La Réunion and The Seychelles. The two cases of HTLV-I have been confirmed by Western-Blot in La Réunion, among blood donors. In Seychelles (87 400 inhabitants in 2012), where blood donors and some other cases are screened, HTLV-I was confirmed with a line immune assay in 43 persons and at least 10-20 patients are known to have tropical spastic paraparesia or adult T-cell lymphoma associated with HTLV-I. In the south-west Indian Ocean, a possibly important other issue may be co-infection of HTLV-1 with the Strongyloides stercoralis roundworm, which is endemic in all countries of the region and which can sometimes lead to severe symptomatic infestation.

Development and validation of a real-time PCR assay for a novel HTLV-1 tax sequence detection and proviral load quantitation

A quantitative real-time PCR (qPCR) assay using SYBR Green dye was established in order to detect and quantify the proviral DNA of HTLV-1 in peripheral blood mononuclear cells (PBMCs). Primers were designed, and the assay was standardized to amplify a novel, conserved HTLV-1 tax region. Proviral load was normalized to the amount of cellular DNA by quantitation of the human albumin gene. Firstly, the qPCR was assessed determining the specificity, sensitivity, dynamic range and intra- and inter-assay reproducibility of the technique. The limit of detection as determined by PROBIT analysis using dilutions of the standard was 2.97 copies. The assay had an excellent dynamic range from 10⁵ to 10¹ copies per reaction and good intra- and inter-assay reproducibility, CVs less than 2%. Secondly, the performance of the qPCR was tested on 40 HTLV-1 seropositive individuals. Proviral load for HTLV-1 carriers ranged from 2.2×10² to more than 8.3×10⁴ copies/10⁶ PBMCs. The high sensitivity and wide dynamic range allowed the determination of a broad range of HTLV-1 proviral loads in infected individuals. This assay is a valuable alternative diagnostic tool when current available serological assays are insufficient. In addition, it will facilitate the study of the relationship between proviral load and pathogenesis.

Men, primates, and germs: an ongoing affair

Humans and nonhuman primates are phylogenetically (i.e., genetically) related and share pathogens that can jump from one species to another. The specific strategies of three groups of pathogens for crossing the species barrier among primates will be discussed. In Africa, gorillas and chimpanzees have succumbed for years to simultaneous epizootics (i.e.. "multi-emergence") of Ebola virus in places where they are in contact with Chiropters, which could be animal reservoirs of these viruses. Human epidemics often follow these major outbreaks. Simian immunodeficiency viruses (SIVs) have an ancient history of coevolution and many interspecific exchanges with their natural hosts. Chimpanzee and gorilla SIVs have crossed the species barrier at different times and places, leading to the emergence of HIV-1 and HIV-2. Other retroviruses, such as the Simian T-Lymphotropic Viruses and Foamiviruses, have also a unique ancient or recent history of crossing the species barrier. The identification of gorilla Plasmodium parasites that are genetically close to P. falciparum suggests that gorillas were the source of the deadly human P. falciparum. Nonhuman plasmodium species that can infect humans represent an underestimated risk.

Adult T-cell lymphoma/leukaemia with haematemesis as a prodromal manifestation

We report a case of adult T-cell leukaemia/lymphoma (ATLL) with haematemesis as a prodromal manifestation. The patient was a 34-year-old woman from Yazd. She also gave a history of a fluctuating skin lesions consisting of non-pruritic papules and ulcers on her feet. Upper gastrointestinal endoscopy disclosed obvious nodularities without ulceration in the antrum of the stomach. Histological and immunohistochemical studies of the gastric biopsy specimen showed lymphomatous infiltration of diffuse pleomorphic type with a T-cell phenotype. Laboratory investigations revealed leucocytosis (consisting of highly atypical lymphocytes, many with clover-leaf-shaped nuclei) and hypercalcaemia. She was found to be seropositive for human T-lymphotropic virus type 1. A diagnosis of overt ATLL was made. The findings in this case indicate that an awareness of the existence of this disease in a non-endemic area such as Yazd is necessary to avoid potential misdiagnosis and be helpful in appropriate therapeutic decision.

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.

Simian retroviruses in African apes

It is now well established that simian immunodeficiency viruses (SIVs) from chimpanzees (SIVcpz) and gorillas (SIVgor) from west Central Africa are at the origin of HIV-1/AIDS. Apes are also infected with other retroviruses, notably simian T-cell lymphotropic viruses (STLVs) and simian foamy viruses (SFVs), that can be transmitted to humans. We discuss the actual knowledge on SIV, STLV and SFV infections in chimpanzees, gorillas, and bonobos. We especially elaborate on how the recent development of non-invasive methods has allowed us to identify the reservoirs of the HIV-1 ancestors in chimpanzees and gorillas, and increased our knowledge of the natural history of SIV infections in chimpanzees. Multiple cross-species events with retroviruses from apes to humans have occurred, but only one transmission of SIVcpz from chimpanzees in south-eastern Cameroon spread worldwide, and is responsible for the actual HIV pandemic. Frequent SFV transmissions have been recently reported, but no human-to-human transmission has been documented yet. Because humans are still in contact with apes, identification of pathogens in wild ape populations can signal which pathogens may be cause risk for humans, and allow the development of serological and molecular assays with which to detect transmissions to humans. Finally, non-invasive sampling also allows the study of the impact of retroviruses and other pathogens on the health and survival of endangered species such as chimpanzees, gorillas, and bonobos.

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

BACKGROUND

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

RESULTS

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

CONCLUSIONS

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

Cross-species transmission of simian retroviruses: how and why they could lead to the emergence of new diseases in the human population

The HIV-1 group M epidemic illustrates the extraordinary impact and consequences resulting from a single zoonotic transmission. Exposure to blood or other secretions of infected animals, through hunting and butchering of bushmeat, or through bites and scratches inflicted by pet nonhuman primates (NHPs), represent the most plausible source for human infection with simian immunodeficiency virus (SIV), simian T-cell lymphotropic virus (STLV) and simian foamy virus. The chance for cross-species transmissions could increase when frequency of exposure and retrovirus prevalence is high. According to the most recent data, human exposure to SIV or STLV appears heterogeneous across the African countries surveyed. Exposure is not sufficient to trigger disease: viral and host molecular characteristics and compatibility are fundamental factors to establish infection. A successful species jump is achieved when the pathogen becomes transmissible between individuals within the new host population. To spread efficiently, HIV likely required changes in human behavior. Given the increasing exposure to NHP pathogens through hunting and butchering, it is likely that SIV and other simian viruses are still transmitted to the human population. The behavioral and socio-economic context of the twenty-first century provides favorable conditions for the emergence and spread of new epidemics. Therefore, it is important to evaluate which retroviruses the human population is exposed to and to better understand how these viruses enter, infect, adapt and spread to its new host.