How to Control HTLV-1-Associated Diseases: Preventing de Novo Cellular Infection Using Antiviral Therapy

Novel insights into human T-lymphotropic virus type-1 (HTLV-1) pathogenesis-host interactions in the manifestation of HTLV-1-associated myelopathy/tropical spastic paraparesis

Human T-lymphotropic virus type-1 (HTLV-1) was the first discovered human oncogenic retrovirus, the etiological agent of two serious diseases have been identified as adult T-cell leukaemia/lymphoma malignancy and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), a debilitating chronic neuro-myelopathy. Despite more than 40 years of molecular, histopathological and immunological studies on HTLV-1-associated diseases, the virulence and pathogenicity of this virus are yet to be clarified. The reason why the majority of HTLV-1-infected individuals (∼95%) remain asymptomatic carriers is still unclear. The deterioration of the immune system towards oncogenicity and autoimmunity makes HTLV-1 a natural probe for the study of malignancy and neuro-inflammatory diseases. Additionally, its slow worldwide spreading has prompted public health authorities and researchers, as urged by the WHO, to focus on eradicating HTLV-1. In contrast, neither an effective therapy nor a protective vaccine has been introduced. This comprehensive review focused on the most relevant studies of the neuro-inflammatory propensity of HTLV-1-induced HAM/TSP. Such an emphasis on the virus-host interactions in the HAM/TSP pathogenesis will be critically discussed epigenetically. The findings may shed light on future research venues in designing and developing proper HTLV-1 therapeutics.

Non-cancerous complications in HTLV-1 carriers

INTRODUCTION

Human T-cell leukemia virus type 1 (HTLV-1) carriers may develop adult T-cell leukemia (ATL), or HTLV-1-associated myelopathy (HAM)/tropical spastic paraparesis (TSP). The evidence is limited regarding other diseases potentially associated with HTLV-1, such as HTLV-1-associated autoimmune diseases.

AREA COVERED

We summarized the available information on complications associated with HTLV-1 infection.

EXPERT OPINION

Previous studies showed that HTLV-1 carriers have an increased incidence of collagen diseases including Sjögren's syndrome, as well as dysthyroidism, diabetes mellitus, and atherosclerosis. Furthermore, cognitive deficits are observed in asymptomatic carriers and in symptomatic carriers who develop HAM/TSP. It is hypothesized that altered immunoregulation occurs as a result of persistent HTLV-1 infection. A systematic review and meta-analysis demonstrated that HTLV-1 infection itself has an adverse impact on overall survival. ATL alone cannot entirely explain the adverse impact of HTLV-1 infection on overall mortality, because the incidence is low, and therefore HTLV-1-associated diseases as a whole may contribute to the inferior clinical outcome. However, there are insufficient data to determine the causal relationship between HTLV-1 infection and each complication. While non-cancerous events linked to HTLV-1 infection are not fatal, they are likely to reduce quality of life. Large prospective studies should be conducted by international collaborators.

Emerging perspectives on RNA virus-mediated infections: from pathogenesis to therapeutic interventions

RNA viruses continue to pose significant threats to global public health, necessitating a profound understanding of their pathogenic mechanisms and the development of effective therapeutic interventions. This manuscript provides a comprehensive overview of emerging perspectives on RNA virus-mediated infections, spanning from the intricate intricacies of viral pathogenesis to the forefront of innovative therapeutic strategies. A critical exploration of antiviral drugs sets the stage, highlighting the diverse classes of compounds that target various stages of the viral life cycle, underscoring the ongoing efforts to combat viral infections. Central to this discussion is the exploration of RNA-based therapeutics, with a spotlight on messenger RNA (mRNA)-based approaches that have revolutionized the landscape of antiviral interventions. Furthermore, the manuscript delves into the intricate world of delivery systems, exploring inno-vative technologies designed to enhance the efficiency and safety of mRNA vaccines. By analyzing the challenges and advancements in delivery mechanisms, this review offers a roadmap for future research and development in this critical area. Beyond conventional infectious diseases, the document explores the expanding applications of mRNA vaccines, including their promising roles in cancer immunotherapy and personalized medicine approaches. This manuscript serves as a valuable resource for researchers, clinicians, and policymakers alike, offering a nuanced perspective on RNA virus pathogenesis and the cutting-edge therapeutic interventions. By synthesizing the latest advancements and challenges, this review contributes significantly to the ongoing discourse in the field, driving the development of novel strategies to combat RNA virus-mediated infections effectively.

Identification of small molecule antivirals against HTLV-1 by targeting the hDLG1-Tax-1 protein-protein interaction

Human T-cell leukemia virus type-1 (HTLV-1) is the first pathogenic retrovirus discovered in human. Although HTLV-1-induced diseases are well-characterized and linked to the encoded Tax-1 oncoprotein, there is currently no strategy to target Tax-1 functions with small molecules. Here, we analyzed the binding of Tax-1 to the human homolog of the drosophila discs large tumor suppressor (hDLG1/SAP97), a multi-domain scaffolding protein involved in Tax-1-transformation ability. We have solved the structures of the PDZ binding motif (PBM) of Tax-1 in complex with the PDZ1 and PDZ2 domains of hDLG1 and assessed the binding of 10 million molecules by virtual screening. Among the 19 experimentally confirmed compounds, one systematically inhibited the Tax-1-hDLG1 interaction in different biophysical and cellular assays, as well as HTLV-1 cell-to-cell transmission in a T-cell model. Thus, our work demonstrates that interactions involving Tax-1 PDZ-domains are amenable to small-molecule inhibition, which provides a framework for the design of targeted therapies for HTLV-1-induced diseases.

Advances in the treatment of human T-cell lymphotropic virus type-I associated myelopathy

INTRODUCTION

Nearly 2-3% of those 10 to 20 million individuals infected with the Human T-cell lymphotropic virus type-1 (HTLV-1); are predisposed to developing HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). It is a neuro-inflammatory disease; differentiated from multiple sclerosis based on the presence of typical neurologic symptoms, confirmation of HTLV-1 infection, and other molecular biomarkers.

AREAS COVERED

A brief review of the epidemiology, host immune responses, and molecular pathogenesis of HAM/TSP is followed by detailed discussions about the host-related risk factors for developing HAM/TSP and success/failure stories of the attempted management strategies.

EXPERT OPINION

Currently, there is no effective treatment for HAM/TSP. Anti-retroviral therapy, peculiar cytokines (IFN-α), some anti-oxidants, and allograft bone marrow transplantation have been used for treating these patients with limited success. Under current conditions, asymptomatic carriers should be examined periodically by a neurologist for early signs of spinal cord injury. Then it is crucial to determine the progress rate to adapt the best management plan for each patient. Corticosteroid therapy is most beneficial in those with acute myelitis. However, slow-progressing patients are best managed using a combination of symptomatic and physical therapy. Additionally, preventive measures should be taken to decrease further spread of HTLV-1 infection.

A Review of the Prevention of Mother-to-Child Transmission of Human T-Cell Lymphotrophic Virus Type 1 (HTLV-1) With a Proposed Management Algorithm

Human T cell lymphotropic virus type 1 (HTLV-1) is a human retrovirus that is endemic in a number of regions across the world. There are an estimated 5–10 million people infected worldwide. Japan is currently the only country with a national antenatal screening programme in place. HTLV-1 is primarily transmitted sexually in adulthood, however it can be transmitted from mother-to-child perinatally. This can occur transplacentally, during the birth process or via breastmilk. If HTLV-1 is transmitted perinatally then the lifetime risk of adult T cell leukemia/lymphoma rises from 5 to 20%, therefore prevention of mother-to-child transmission of HTLV-1 is a public health priority. There are reliable immunological and molecular tests available for HTLV-1 diagnosis during pregnancy and screening should be considered on a country by country basis. Further research on best management is needed particularly for pregnancies in women with high HTLV-1 viral load. A first step would be to establish an international registry of cases and to monitor outcomes for neonates and mothers. We have summarized key risk factors for mother-to-child transmission of HTLV-1 and subsequently propose a pragmatic guideline for management of mothers and infants in pregnancy and the perinatal period to reduce the risk of transmission. This is clinically relevant in order to reduce mother-to-child transmission of HTLV-1 and it's complications.

Repurposing antiviral drugs against HTLV-1 protease by molecular docking and molecular dynamics simulation

Human T-cell leukemia virus type I (HTLV-1) belongs to the delta retrovirus family and the etiological agent of adult T-cell leukemia (ATL(. While the current HTLV-1 therapy, relies on using Zidovudine plus IFN-γ, there is no FDA approved drugs against it. In silico drug repurposing is a fast and accurate way for screening US-FDA approved drugs to find a therapeutic option for the HTLV-1 infection. So that, this research aims to analyze a dataset of approved antiviral drugs as a potential prospect for an anti-viral drug against HTLV-1 infection. Molecular docking simulation was performed to identify interactions of the antiviral drugs with the key residues in the HTLV-1 protease binding site. Then, molecular dynamics simulation was also performed for the potential protein-ligand complexes to confirm the stable behavior of the ligands inside the binding pocket. The best docking scores with the target was found to be Simeprevir, Atazanavir, and Saquinavir compounds which indicate that these drugs can firmly bind to the HTLV-1 protease. The MD simulation confirmed the stability of Simeprevir-protease, Atazanavir-Protease, and Saquinavir-Protease interactions. Clearly, these compounds should be further evaluated in experimental assays and clinical trials to confirm their actual activity against HTLV-1 infection.Communicated by Ramaswamy H. Sarma.

HTLV-1 Transmission and HIV Pre-exposure Prophylaxis: A Scoping Review

HIV pre-exposure prophylaxis (HIV-PrEP) is effective in reducing the likelihood of HIV acquisition in HIV-negative people at high risk of exposure. Guidelines recommend testing for sexually transmitted infections (STIs) before starting, and periodically on PrEP, including bacterial infections, HIV, hepatitis C virus, and, for those who are non-immune, hepatitis B virus. Diagnosed infections can be promptly treated to reduce onward transmission. HTLV-1 is not mentioned; however, it is predominantly sexually transmitted, causes adult T-cell leukaemia/lymphoma (ATL) or myelopathy in 10% of those infected, and is associated with an increased risk of death in those without any classically HTLV-associated condition. The 2021 WHO Technical Report on HTLV-1 called for the strengthening of global public health measures against its spread. In this scoping review, we, therefore, (1) discuss the epidemiological context of HIV-PrEP and HTLV-1 transmission; (2) present current knowledge of antiretrovirals in relation to HTLV-1 transmission prevention, including nucleos(t)ide reverse transcriptase inhibitors (NRTIs) and integrase strand transfer inhibitors (INSTIs); and (3) identify knowledge gaps where data are urgently required to inform global public health measures to protect HIV-PrEP users from HTLV-1 acquisition. We suggest that systematic seroprevalence studies among PrEP-using groups, including men who have sex with men (MSM), people who inject drugs (PWIDs), and female sex workers (FSWs), are needed. Further data are required to evaluate antiretroviral efficacy in preventing HTLV-1 transmission from in vitro studies, animal models, and clinical cohorts. PrEP delivery programmes should consider prioritizing the long-acting injectable INSTI, cabotegravir, in HTLV-1 endemic settings.

Retroviral infection of human neurospheres and use of stem Cell EVs to repair cellular damage

HIV-1 remains an incurable infection that is associated with substantial economic and epidemiologic impacts. HIV-associated neurocognitive disorders (HAND) are commonly linked with HIV-1 infection; despite the development of combination antiretroviral therapy (cART), HAND is still reported to affect at least 50% of HIV-1 infected individuals. It is believed that the over-amplification of inflammatory pathways, along with release of toxic viral proteins from infected cells, are primarily responsible for the neurological damage that is observed in HAND; however, the underlying mechanisms are not well-defined. Therefore, there is an unmet need to develop more physiologically relevant and reliable platforms for studying these pathologies. In recent years, neurospheres derived from induced pluripotent stem cells (iPSCs) have been utilized to model the effects of different neurotropic viruses. Here, we report the generation of neurospheres from iPSC-derived neural progenitor cells (NPCs) and we show that these cultures are permissive to retroviral (e.g. HIV-1, HTLV-1) replication. In addition, we also examine the potential effects of stem cell derived extracellular vesicles (EVs) on HIV-1 damaged cells as there is abundant literature supporting the reparative and regenerative properties of stem cell EVs in the context of various CNS pathologies. Consistent with the literature, our data suggests that stem cell EVs may modulate neuroprotective and anti-inflammatory properties in damaged cells. Collectively, this study demonstrates the feasibility of NPC-derived neurospheres for modeling HIV-1 infection and, subsequently, highlights the potential of stem cell EVs for rescuing cellular damage induced by HIV-1 infection.

Comparative analysis of the unbinding pathways of antiviral drug Indinavir from HIV and HTLV1 proteases by supervised molecular dynamics simulation

Determining the unbinding pathways of potential small molecule compounds from their target proteins is of great significance for designing efficacious treatment solutions. One of these potential compounds is the approved HIV-1 protease inhibitor, Indinavir, which has a weak effect on the HTLV-1 protease. In this work, by employing the SuMD method, we reconstructed the unbinding pathways of Indinavir from HIV and HTLV-1 proteases to compare and understand the mechanism of the unbinding and to discover the reasons for the lack of inhibitory activity of Indinavir against the HTLV-1 protease. We achieved multiple unbinding events from both HIV and HTLV-1 proteases in which the RMSD values of Indinavir reached over 40 Å. Also, we found that the mobility and fluctuations of the flap region are higher in the HTLV-1 protease, making the drug less stable. We realized that critically positioned aromatic residues such as Trp98/Trp98' and Phe67/Phe67' in the HTLV-1 protease could make strong π-Stacking interactions with Indinavir in the unbinding pathway, which are unfavorable for the stability of Indinavir in the active site. The details found in this study can make a reasonable explanation for the lack of inhibitory activity of this drug against HTLV-1 protease. We believe the details discovered in this work can help design more effective and selective inhibitors for the HTLV-1 protease.

Activation of PERK-ATF4-CHOP pathway as a novel therapeutic approach for efficient elimination of HTLV-1-infected cells

Patients with adult T-cell leukemia (ATL) exhibit a poor prognosis and overall survival rate when treated with standard chemotherapy, highlighting the continued requirement for the development of novel safe and effective therapies for human T-cell leukemia virus type 1 (HTLV-1)-related diseases. In this study, we demonstrated that MK-2048, a second-generation HIV-1 integrase (IN) inhibitor, potently and selectively kills HTLV-1-infected cells. Differential transcriptome profiling revealed significantly elevated levels of gene expression of the unfolded protein response (UPR) PKR-like ER kinase (PERK) signaling pathway in ATL cell lines following MK-2048 treatment. We also identified a significant downregulation in glucose regulated protein 78 (GRP78), a master regulator of the UPR in the CD4+CADM1+ HTLV-1-infected cell population of primary HTLV-1 carrier peripheral blood mononuclear cells (PBMCs) (n = 9), suggesting that HTLV-1-infected cells are hypersensitive to endoplasmic reticulum (ER) stress-mediated apoptosis. MK-2048 efficiently reduced proviral loads in primary HTLV-1 carrier PBMCs (n = 4), but had no effect on the total numbers of these cells, indicating that MK-2048 does not affect the proliferation of HTLV-1-uninfected PBMCs. MK-2048 specifically activated the ER stress-related proapoptotic gene, DNA damage-inducible transcript 3 protein (DDIT3), also known as C/EBP homologous protein (CHOP), in HTLV-1-infected but not uninfected cells of HTLV-1-carrier PBMCs. Our findings demonstrated that MK-2048 selectively induces HTLV-1-infected cell apoptosis via the activation of the UPR. This novel regulatory mechanism of the HIV IN inhibitor MK-2048 in HTLV-1-infected cells provides a promising prophylactic and therapeutic target for HTLV-1-related diseases including ATL.

HTLV-I and Strongyloides in Australia: The worm lurking beneath

Strongyloidiasis and HTLV-I (human T-lymphotropic virus-1) are important infections that are endemic in many countries around the world with an estimated 370 million infected with Strongyloides stercoralis alone, and 5-10 million with HTVL-I. Co-infections with these pathogens are associated with significant morbidity and can be fatal. HTLV-I infects T-cells thus causing dysregulation of the immune system which has been linked to dissemination and hyperinfection of S. stercoralis leading to bacterial sepsis which can result in death. Both of these pathogens are endemic in Australia primarily in remote communities in Queensland, the Northern Territory, and Western Australia. Other cases in Australia have occurred in immigrants and refugees, returned travellers, and Australian Defence Force personnel. HTLV-I infection is lifelong with no known cure. Strongyloidiasis is a long-term chronic disease that can remain latent for decades, as shown by infections diagnosed in prisoners of war from World War II and the Vietnam War testing positive decades after they returned from these conflicts. This review aims to shed light on concomitant infections of HTLV-I with S. stercoralis primarily in Australia but in the global context as well.

Lymphotropic Viruses: Chronic Inflammation and Induction of Cancers

Inflammation induced by transcription factors, including Signal Transducers and Activators of Transcription (STATs) and NF-κB, in response to microbial pathogenic infections and ligand dependent receptors stimulation are critical for controlling infections. However, uncontrolled inflammation induced by these transcription factors could lead to immune dysfunction, persistent infection, inflammatory related diseases and the development of cancers. Although the induction of innate immunity and inflammation in response to viral infection is important to control virus replication, its effects can be modulated by lymphotropic viruses including human T-cell leukemia virus type 1 (HTLV-1), Κaposi's sarcoma herpesvirus (KSHV), and Epstein Barr virus (EBV) during de novo infection as well as latent infection. These lymphotropic viruses persistently activate JAK-STAT and NF-κB pathways. Long-term STAT and NF-κB activation by these viruses leads to the induction of chronic inflammation, which can support the persistence of these viruses and promote virus-mediated cancers. Here, we review how HTLV-1, KSHV and EBV hijack the function of host cell surface molecules (CSMs), which are involved in the regulation of chronic inflammation, innate and adaptive immune responses, cell death and the restoration of tissue homeostasis. Thus, better understanding of CSMs-mediated chronic activation of STATs and NF-κB pathways in lymphotropic virus-infected cells may pave the way for therapeutic intervention in malignancies caused by lymphotropic viruses.

Regulation of Expression and Latency in BLV and HTLV

Human T-lymphotrophic virus type 1 (HTLV-1) and Bovine leukemia virus (BLV) belong to the Deltaretrovirus genus. HTLV-1 is the etiologic agent of the highly aggressive and currently incurable cancer adult T-cell leukemia (ATL) and a neurological disease HTLV-1-associated myelopathy (HAM)/tropical spastic paraparesis (TSP). BLV causes neoplastic proliferation of B cells in cattle: enzootic bovine leucosis (EBL). Despite the severity of these conditions, infection by HTLV-1 and BLV appear in most cases clinically asymptomatic. These viruses can undergo latency in their hosts. The silencing of proviral gene expression and maintenance of latency are central for the establishment of persistent infection, as well as for pathogenesis in vivo. In this review, we will present the mechanisms that control proviral activation and retroviral latency in deltaretroviruses, in comparison with other exogenous retroviruses. The 5′ long terminal repeats (5′-LTRs) play a main role in controlling viral gene expression. While the regulation of transcription initiation is a major mechanism of silencing, we discuss topics that include (i) the epigenetic control of the provirus, (ii) the cis-elements present in the LTR, (iii) enhancers with cell-type specific regulatory functions, (iv) the role of virally-encoded transactivator proteins, (v) the role of repressors in transcription and silencing, (vi) the effect of hormonal signaling, (vii) implications of LTR variability on transcription and latency, and (viii) the regulatory role of non-coding RNAs. Finally, we discuss how a better understanding of these mechanisms may allow for the development of more effective treatments against Deltaretroviruses.

Microbial Biofilms: Human T-cell Leukemia Virus Type 1 First in Line for Viral Biofilm but Far Behind Bacterial Biofilms

Human T-cell leukemia virus type 1 (HTLV-1) is a retrovirus associated with adult T-cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). To date, it is the unique published example of a virus able to form a biofilm at the surface of infected cells. Deeply studied in bacteria, bacterial biofilms represent multicellular assemblies of bacteria in contact with a surface and shielded by the extracellular matrix (ECM). Microbial lifestyle in biofilms, either viral or bacterial, is opposed structurally and physiologically to an isolated lifestyle, in which viruses or bacteria freely float in their environment. HTLV-1 biofilm formation is believed to be promoted by viral proteins, mainly Tax, through remodeling of the ECM of the infected cells. HTLV-1 biofilm has been linked to cell-to-cell transmission of the virus. However, in comparison to bacterial biofilms, very little is known on kinetics of viral biofilm formation or dissemination, but also on its pathophysiological roles, such as escape from immune detection or therapeutic strategies, as well as promotion of leukemogenesis. The switch between production of cell-free isolated virions and cell-associated viral biofilm, although not fully apprehended yet, remains a key step to understand HTLV-1 infection and pathogenesis.

The role of endogenous retroviruses-K in human cancer

It is known that human endogenous retroviruses (HERVs) constitute almost 8% of the human genome. Although the expression of HERVs from the human genome is tightly regulated, different exogenous and endogenous factors could trigger HERV activation. Aberrant expression of different HERVs may potentially cause a variety of diseases such as neurological and autoimmune diseases as well as cancer. It is suggested that HERV-K can induce cancer through different mechanisms that are discussed. The interplay between some tumor viruses and HERV-K seems to be a key player in progression of viral-associated cancers because elevated levels of Rec and Np9 proteins are observed in several cancers. The frequent over expression of HERV proteins and some specific antibodies in cancer cells could be considered as suitable prognostic and therapeutic biomarkers in diagnosis and treatment of cancers. The expression of HERV proteins in cancers and development of immune responses against them may also be used as targets for cancer immunotherapy. Further studies are warranted to evaluate the role of HERVs in cancer formation and use of different HERV proteins in developing new diagnostic and therapeutic approaches for cancer treatments.

The effect of alcoholic extract from Eucalyptus camaldulensis leaves on HTLV-1 Tax activities

HTLV-1 is a human retrovirus responsible for adult T-cell leukemia (ATL) and certain other clinical disorders. The viral Tax oncoprotein plays a central role in HTLV-1 pathogenicity, mainly due to its capacity of inducing the transcriptional activity of various transcriptional factors like NFқB. Eucalyptus camaldulensis (Ec) is considered as a traditional medicinal plant with valuable therapeutic effects. Here we evaluated the activity of its ethanolic leave extract on different Tax activities by testing its influence on Tax-induced activity of NFқB and HTLV-1 LTR in Jurkat cells. Our results showed that Ec inhibited Tax induced activation of NFқB -, SRF- dependent promoters and HTLV-1 LTR. Ec extract has no effect on the binding of Tax to NFқB while it strongly prevented the degradation of IҝBα induced by Tax probably as a result of preventing the link between Tax and IKKγ. In addition, increasing the cellular level of P-TEFb-cyclinT1 significantly reduced the inhibitory effect of Ec on Tax activities, probably by preventing the interaction between Tax and P-TEFb-cyclin T1. The 40%-MeOH fraction of this extract, which is rich with polyphenols, offered the highest inhibitory effect against Tax activities. Further studies are required for the isolation and identification of active component/s in this extract which may be developed in the future as preventive/curing drugs for HTLV-1 related diseases.

Antiretroviral Therapy in HTLV-1 Infection: An Updated Overview

The human T cell leukemic/lymphotropic virus type 1 (HTLV-1), discovered several years ago, is the causative agent for a rapid progressive haematological malignancy, adult T cell leukemia (ATL), for debilitating neurological diseases and for a number of inflammatory based diseases. Although the heterogeneous features of the diseases caused by HTLV-1, a common topic concerning related therapeutic treatments relies on the use of antiretrovirals. This review will compare the different approaches and opinions in this matter, giving a concise overview of preclinical as well as clinical studies covering all the aspects of antiretrovirals in HTLV-1 infection. Studies will be grouped on the basis of the class of antiretroviral, putting together both pre-clinical and clinical results and generally following a chronological order. Analysis of the existing literature highlights that a number of preclinical studies clearly demonstrate that different classes of antiretrovirals, already utilized as anti-HIV agents, are actually capable to efficiently contrast HTLV-1 infection. Nevertheless, the results of most of the clinical studies are generally discouraging on the same point. In conclusion, the design of new antiretrovirals more specifically focused on HTLV-1 targets, and/or the establishment of early treatments with antiretrovirals could hopefully change the perspectives of diseases caused by HTLV-1.

Breastfeeding and the Risk of Infant Illness in Asia: A Review

Infancy remains the most vulnerable period of human life for death, illness, and establishing a lifetime trajectory of growth and health. It is estimated that there are 5.3 million deaths under five years of age worldwide and approximately 800,000 lives could be saved by improving breastfeeding rates and duration. In Asia, an estimated 300,000-350,000 child deaths could be prevented with optimal breastfeeding and the majority would be under 12 months of age. We present a systematic review of studies of infection and breastfeeding in infants in Asia and further review interactions of selected infectious diseases and breastfeeding. Initially, 2459 records of possible interest were identified, 153 full text papers were reviewed in detail, and 13 papers describing diarrhoeal disease and/or acute respiratory tract infection were selected for inclusion in the review. Additional papers were selected to discuss specific diseases and their relationship to breastfeeding. The review found that a variety of methods were used with differing definitions of breastfeeding and diseases. Overall, breastfeeding when compared to the use of infant formula, is associated with significantly lower rates of diarrhoeal disease and lower respiratory tract infection, with a reduction of 50% or more to be expected, especially in infants under six months of age. The relationship between breastfeeding and specific diseases including measles and HTLV1 were reviewed. Breastfeeding reduces some disease rates, but there remain a few conditions where breastfeeding may be contra-indicated.

HTLV-1 infection: An emerging risk. Pathogenesis, epidemiology, diagnosis and associated diseases

The Human T-Lymphotropic Virus type 1 (HTLV-1) affects up to 10 million people worldwide. It is directly associated to one of the most aggressive T cell malignancies: Adult T Cell Leukemia-Lymphoma (ATLL) and a progressive neurological disorder, Tropical Spastic Paraparesis/ HTLV-1 Associated Myelopathy (TSP/HAM). Also, infected patients tend to have more severe forms of infectious diseases such as Strongyloidiasis and Tuberculosis. HTLV spreads through parenteral, sexual, and vertical (mother-to-child) routes. Effective viral transmission is produced mainly by cell to cell mechanism, unlike other retroviruses such as HIV, which usually spread infecting cells in a cell-free form. HTLV also has a peculiar distribution, with clusters of high endemicity in nearby areas of very low prevalence or absence of the virus. This could be explained by factors including a possible founder effect, the predominance of mother to child transmission and the cell-to-cell trans-mission mechanisms. More data on viral epidemiology are needed in order to develop strategies in endemic areas aimed at reducing viral dissemination. In this review, we critically analyze HTLV-1 pathogenesis, epidemiology, diagnosis, associated diseases, preventive strategies, and treatments, with emphasis to the emerging risk for Europe and particularly Spain, focusing on prevention methods to avoid viral transmission and associated diseases.

Inhibition of HTLV-1 Infection by HIV-1 First- and Second-Generation Integrase Strand Transfer Inhibitors

More than 10 million people worldwide are infected with the retrovirus human T-cell lymphotropic virus type 1 (HTLV-1). Infection phenotypes can range from asymptomatic to severe adult T-cell leukemia/lymphoma (ATLL) and HTLV-1-associated myelopathy. HTLV-1, like human immunodeficiency virus type 1 (HIV-1), is a blood-borne pathogen and viral infection happens in a similar fashion, with the major mode of transmission through breastfeeding. There is a strong correlation between time of infection and disease development, with a higher incidence of ATLL in patients infected during childhood. There is no successful therapeutic or preventative regimen for HTLV-1. It is therefore essential to develop therapies to inhibit transmission or block the onset/development of HTLV-1 associated diseases. Recently, we have seen the overwhelming success of integrase strand transfer inhibitors (INSTIs) in the treatment of HIV-1. Previously, raltegravir was shown to inhibit HTLV-1 infection. Here, we tested FDA-approved and two Phase II HIV-1 INSTIs in vitro and in a cell-to-cell infection model and show that they are highly active in blocking HTLV-1 infection, with bictegravir (EC₅₀ = 0.30 ± 0.17 nM) performing best overall. INSTIs, in particular bictegravir, are more potent in blocking HTLV-1 transmission than tenofovir disproxil fumarate (TDF), an RT inhibitor. Our data suggest that HIV-1 INSTIs could present a good clinical strategy in HTLV-1 management and justifies the inclusion of INSTIs in clinical trials.

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.

Transactivation of human endogenous retroviruses by tumor viruses and their functions in virus-associated malignancies

Human endogenous retroviruses (HERVs), viral-associated sequences, are normal components of the human genome and account for 8–9% of our genome. These original provirus sequences can be transactivated to produce functional products. Several reactivated HERVs have been implicated in cancers and autoimmune diseases. An emerging body of literature supports a potential role of reactivated HERVs in viral diseases, in particular viral-associated neoplasms. Demystifying studies on the mechanism(s) of HERV reactivation could provide a new framework for the development of treatment and prevention strategies targeting virus-associated tumors. Although available data suggest that co-infection by other viruses, such as Kaposi’s Sarcoma-associated herpesvirus (KSHV) and Epstein–Barr virus (EBV), may be a crucial driving force to transactivate HERV boom, the mechanisms of action of viral infection-induced HERV transactivation and the contributions of HERVs to viral oncogenesis warrant further studies. Here, we review viral co-infection contributes to HERVs transactivation with focus on human viral infection associated oncogenesis and diseases, including the abilities of viral regulators involved in HERV reactivation, and physiological effects of viral infection response on HERV reactivation.