Brain-Thymus Connections in Chagas Disease.

BACKGROUND: The brain and the immune systems represent the two primary adaptive systems within the body. Both are involved in a dynamic process of communication, vital for the preservation of mammalian homeostasis. This interplay involves two major pathways: the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system. SUMMARY: The establishment of infection can affect immunoneuroendocrine interactions, with functional consequences for immune organs, particularly the thymus. Interestingly, the physiology of this primary organ is not only under the control of the central nervous system (CNS) but also exhibits autocrine/paracrine regulatory circuitries mediated by hormones and neuropeptides that can be altered in situations of infectious stress or chronic inflammation. In particular, Chagas disease, caused by the protozoan parasite Trypanosoma cruzi (T. cruzi), impacts upon immunoneuroendocrine circuits disrupting thymus physiology. Here, we discuss the most relevant findings reported in relation to brain-thymic connections during T. cruzi infection, as well as their possible implications for the immunopathology of human Chagas disease. KEY MESSAGES: During T. cruzi infection, the CNS influences thymus physiology through an intricate network involving hormones, neuropeptides, and pro-inflammatory cytokines. Despite some uncertainties in the mechanisms and the fact that the link between these abnormalities and chronic Chagasic cardiomyopathy is still unknown, it is evident that the precise control exerted by the brain over the thymus is markedly disrupted throughout the course of T. cruzi infection.

Thymic Innervation Impairment in Experimental Autoimmune Encephalomyelitis.

INTRODUCTION: The thymus is the primary lymphoid organ responsible for normal T-cell development. Yet, in abnormal metabolic conditions as well as an acute infection, the organ exhibits morphological and cellular alterations. It is well established that the immune system is in a tidy connection and dependent on the central nervous system (CNS), which regulates thymic function by means of innervation and neurotransmitters. Sympathetic innervation leaves the CNS and spreads through thymic tissue, where nerve endings interact directly or indirectly with thymic cells contributing to their maintenance and development. METHODS: Herein, we hypothesized that brain damage due to an inflammatory process might elicit alterations upon the thymic-CNS neuroimmune axis, altering not just the sympathetic innervation and neurotransmitter release, but also modifying the thymus microenvironment and T-cell development. We used the well-established multiple sclerosis model of experimental autoimmune encephalomyelitis (EAE), to study putative changes in the thymic neural, lymphoid, and microenvironmental compartments. RESULTS: We showed that along with EAE clinical development, thymus morphology, and cellular compartments are affected, altering the peripheric T-cell population and modifying the retrograde thymic communication toward the CNS. CONCLUSION: Altogether, our data suggest that the thymic-CNS neuroimmune bidirectional axis is compromised in EAE. This imbalance may contribute to an increased and uncontrolled auto-immune reaction.

Investigation of Unprecedented Sites and Proposition of New Ligands for Programmed Cell Death Protein I through Molecular Dynamics with Probes and Virtual Screening.

Cancer immunotherapy has attracted increasing attention over the last few years. Programmed cell death protein 1 (PD-1) promotes self-tolerance and inhibits immune responses by modulating the T-cell function. The interaction between PD-1 and programmed cell death ligand-1 (PD-L1) leads to immune exhaustion, protecting cancer cells from destruction. Here, we computationally designed a novel ligand named 1508 that binds to an unprecedented PD-1 cavity identified by MixMD and defined by amino acid residues Lys78 to Val97. We showed through a set of MD simulations totaling 12.5 µs that ligand 1508 establishes frequent cation-π and hydrogen bonding interactions with amino acid residues Lys78 and Arg86, respectively, and stabilizes the PD-1 C'D loop in a conformation that does not favor PD-1-PD-L1 complex formation. This study highlights the power of MixMD in exposing new cavities prone to protein-protein complex inhibition and establishes the basis for the design of new molecules that target the PD-1 C'D cavity as an alternative for exploring the modulation of the PD-1-PD-L1 complex in cancer therapy.

Article-processing charges as a barrier for science in low-to-medium income regions.

It is widely accepted that science is universal by nature. However, to make science universal, access to research findings is imperative. The open access model of publication of academic articles was established and consolidated during the last two decades. However, most of the open access journals apply article-processing charges (APCs), which can cost more than USD 10,000.00. In regions where support for research is scarce, these funds are usually not available. Similar problems occur in countries with weak economies and, consequently, unfavorable currency conversion rates. This situation reveals a barrier to the alleged universality of science and the access to research findings. In this manuscript, the barriers faced by authors and institutions from low-to-middle income regions to cover APCs and make their science freely available are discussed and illustrated with recent numbers.

Brazilian science: towards extinction?

Brazilian science is under attack. In this manuscript, we will discuss the most recent events that, if not reverted, will make Brazilian science inviable. We urge the scientific community in Brazil and abroad to stand up and resist in defense of more than a century of essential scientific contributions.

Critically Ill Coronavirus Disease 2019 Patients Exhibit Hyperactive Cytokine Responses Associated With Effector Exhausted Senescent T Cells in Acute Infection.

BACKGROUND: Coronavirus disease 2019 (COVID-19) can progress to severe pneumonia with respiratory failure and is aggravated by the deregulation of the immune system causing an excessive inflammation including the cytokine storm. METHODS: In this study, we report that severe acutely infected patients have high levels of both type-1 and type-2 cytokines. RESULTS: Our results show abnormal cytokine levels upon T-cell stimulation, in a nonpolarized profile. Furthermore, our findings indicate that this hyperactive cytokine response is associated with a significantly increased frequency of late-differentiated T cells with particular phenotype of effector exhausted/senescent CD28-CD57+ cells. Of note, we demonstrated for the first time an increased frequency of CD3+CD4+CD28-CD57+ T cells with expression of programmed death 1, one of the hallmarks of T-cell exhaustion. CONCLUSIONS: These findings reveal that COVID-19 is associated with acute immunodeficiency, especially within the CD4+ T-cell compartment, and points to possible mechanisms of loss of clonal repertoire and susceptibility to viral relapse and reinfection events.

VLA-4 as a Central Target for Modulating Neuroinflammatory Disorders.

The complex steps leading to the central nervous system (CNS) inflammation and the progress to neuroinflammatory and neurodegenerative disorders have opened up new research and intervention avenues. This review focuses on the therapeutic targeting of the VLA-4 integrin to discuss the clear-cut effect on immune cell trafficking into brain tissues. Besides, we explore the possibility that blocking VLA-4 may have a relevant impact on nonmigratory activities of immune cells, such as antigen presentation and T-cell differentiation, during the neuroinflammatory process. Lastly, the recent refinement of computational techniques is highlighted as a way to increase specificity and to reduce the detrimental side effects of VLA-4 immunotherapies aiming at developing better clinical interventions.

Immunology south of the equator in the Americas.

Despite a troubled economic and political past, a tradition of fundamental research in immunology and infectious diseases has been fostered in Argentina, Brazil and Chile, as well as in other South American countries.

Semaphorin-3A-Related Reduction of Thymocyte Migration in Chemically Induced Diabetic Mice.

BACKGROUND: Previous work revealed the existence of a severe thymic atrophy with massive loss of immature CD4+CD8+ thymocytes in animals developing insulin-dependent diabetes, chemically induced by alloxan. Furthermore, the intrathymic expression of chemokines, such as CXCL12, is changed in these animals, suggesting that cell migration-related patterns may be altered. One molecular interaction involved in normal thymocyte migration is that mediated by soluble semaphorin-3A and its cognate receptor neuropilin-1. OBJECTIVES: We investigated herein the expression and role of semaphorin-3A in the migratory responses of thymocytes from alloxan-induced diabetic mice. We characterized semaphorin-3A and its receptor, neuropilin-1, in thymuses from control and diabetic mice as well as semaphorin-3A-dependent migration of developing thymocytes in both control and diabetic animals. METHODS: Diabetes was chemically induced after a single injection of alloxan in young adult BALB/c mice. Thymocytes were excised from control and diabetic individuals and subjected to cytofluorometry for simultaneous detection of semaphorin-3A or neuropilin-1 in CD4/CD8-defined subsets. Cell migration in response to semaphorin-3A was performed using cell migration transwell chambers. RESULTS: Confirming previous data, we observed a severe decrease in the total numbers of thymocytes in diabetic mice, which comprised alterations in both immature (double-negative subpopulations) and mature CD4/CD8-defined thymocyte subsets. These were accompanied by a decrease in the absolute numbers of semaphorin-3A-bearing thymocytes, comprising CD4-CD8-, CD4+CD8+, and CD4-CD8+ cells. Additionally, immature CD4-CD8- and CD4+CD8+ developing T cells exhibited a decrease in the membrane density of semaphorin-3A. The relative and absolute numbers of neuropilin-1-positive thymocytes were also decreased in diabetic mouse thymocytes compared to controls, as seen in CD4-CD8-, CD4+CD8+, and CD4-CD8+ cell subpopulations. Functionally, we observed a decrease in the chemorepulsive role of semaphorin-3A, as revealed by transwell migration chambers. Such an effect was seen in all immature and mature thymocyte subsets. CONCLUSIONS: Taken together, our data clearly unravel a disruption in the normal cell migration pattern of developing thymocytes following chemically induced insulin-dependent diabetes, as ascertained by the altered migratory response to sempahorin-3A. In conceptual terms, it is plausible to think that such disturbances in the migration pattern of thymocytes from these diabetic animals may exert an impact in the cell-mediated immune response of these mice.

CD49d Is Upregulated in Circulating T Lymphocytes from HTLV-1-Infected Patients.

INTRODUCTION: HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic progressive myelopathy associated with an inflammation of the central nervous system (CNS), being characterized by perivascular infiltration of inflammatory cells. HTLV-1-infected cells have the capacity to migrate through endothelial layers by enhancing adhesion receptor expression and corresponding ligands. T cells interact with the extracellular matrix via integrin receptors and these interactions affect both cell migration and proliferation. The importance of these interactions in retrovirus-induced diseases, however, remains less clear. METHODS: Herein we studied the expression of 3 integrin alpha chains (CD49d, CD49e, and CD49f) on the membrane of T-cell subsets in patients infected by HTLV-1, both HAM/TSP patients and oligo/asymptomatic subjects who were asymptomatic or presented slight manifestations related to the virus infection. RESULTS: We observed higher peripheral blood frequency of CD49dhiCD4+ and CD49dhiCD8+ T cells in HTLV-1-infected patients. CONCLUSION: Our findings suggest that the increased expression of adhesion molecules, such as CD49d on T lymphocytes from HTLV-1-infected patients may contribute to the pathogenesis of the disease, in both oligo/asymptomatic and HAM/TSP-infected subjects. Accordingly, it is conceivable that there is a potential use of CD49d as target for a therapeutic approach aiming at blocking migration of activated T cells from HTLV-1-infected patients into the CNS, thus avoiding the progression to HAM/TSP.

Human acute Chagas disease: changes in factor VII, activated protein C and hepatic enzymes from patients of oral outbreaks in Pará State (Brazilian Amazon).

Oral transmission of Chagas disease has been increasing in Latin American countries. The present study aimed to investigate changes in hepatic function, coagulation factor levels and parasite load in human acute Chagas disease (ACD) secondary to oral Trypanosoma cruzi transmission. Clinical and epidemiological findings of 102 infected individuals attended in the State of Pará from October 2013 to February 2016 were included. The most common symptoms were fever (98%), asthenia (83.3%), face and limb edema (80.4%), headache (74.5%) and myalgia (72.5%). The hepatic enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST) of 30 ACD patients were higher compared with controls, and this increase was independent of the treatment with benznidazole. Moreover, ACD individuals had higher plasma levels of activated protein C and lower levels of factor VII of the coagulation cascade. Patients with the highest parasite load had also the most increased transaminase levels. Also, ALT and AST were associated moderately (r = 0.429) and strongly (r = 0.595) with parasite load respectively. In conclusion, the present study raises the possibility that a disturbance in coagulation and hepatic function may be linked to human ACD.

Environmental Signals on Microglial Function during Brain Development, Neuroplasticity, and Disease.

Recent discoveries on the neurobiology of the immunocompetent cells of the central nervous system (CNS), microglia, have been recognized as a growing field of investigation on the interactions between the brain and the immune system. Several environmental contexts such as stress, lesions, infectious diseases, and nutritional and hormonal disorders can interfere with CNS homeostasis, directly impacting microglial physiology. Despite many encouraging discoveries in this field, there are still some controversies that raise issues to be discussed, especially regarding the relationship between the microglial phenotype assumed in distinct contexts and respective consequences in different neurobiological processes, such as disorders of brain development and neuroplasticity. Also, there is an increasing interest in discussing microglial-immune system cross-talk in health and in pathological conditions. In this review, we discuss recent literature concerning microglial function during development and homeostasis. In addition, we explore the contribution of microglia to synaptic disorders mediated by different neuroinflammatory outcomes during pre- and postnatal development, with long-term consequences impacting on the risk and vulnerability to the emergence of neurodevelopmental, neurodegenerative, and neuropsychiatric disorders.

Zika virus infects human blood mononuclear cells.

BACKGROUND: Zika virus (ZIKV) infection gained public health concern after the 2015 outbreak in Brazil, when microcephaly rates increased in babies born from infected mothers. It was demonstrated that ZIKV causes a congenital Zika virus syndrome, including various alterations in the development of the central nervous system. Although the infection of cells from the nervous system has been well documented, less is known in respect of ZIKV ability to infect immune cells. Herein, we investigated if peripheral blood mononuclear cells (PBMCs), freshly-isolated from healthy donors, could be infected by ZIKV. METHODS: PBMCs from healthy donors were isolated and cultured in medium with ZIKV strain Rio-U1 (MOI = 0.1). Infection was analyzed by RT-qPCR and flow cytometry. RESULTS: We detected the ZIKV RNA in PBMCs from all donors by RT-qPCR analysis. The detection of viral antigens by flow cytometry revealed that PBMC from more than 50% the donors were infected by ZIKV, with CD3+CD4+ T cells, CD3-CD19+ B cells and CD3+CD8+ T cells being, respectively, the most frequently infected subpopulations, followed by CD14+ monocytes. Additionally, we observed high variability in PBMC infection rates among different donors, either by numbers or type infected cells. CONCLUSIONS: These findings raise the hypothesis that PBMCs can act as a reservoir of the virus, which may facilitate viral dissemination to different organs, including immune-privileged sites.

Reduced CD4 T Lymphocytes in Lymph Nodes of the Mouse Model of Autism Induced by Valproic Acid.

OBJECTIVE: Considering the potential role of lymphocytes in the pathophysiology of autism spectrum disorder (ASD), we aimed to evaluate possible alterations of T cell pools in the lymphoid organs of an animal model of autism induced by valproic acid (VPA). Pregnant Swiss mice received a single intraperitoneal injection of 600 mg/kg of VPA (VPA group) or saline (control group) on day 11 of gestation. Male offspring were euthanized on postnatal day 60 for removal of thy-muses, spleens, and a pool of inguinal, axillary and brachial lymph nodes. Cellularity was evaluated, and flow cytometry analysis was performed on cell suspensions incubated with the mouse antibodies anti-CD3-FITC, anti-CD4-PE, and anti-CD8-PE-Cy7. We observed that the prenatal exposure to VPA induced a reduction in the numbers of CD3+CD4+ T cells in their lymph nodes when compared to the control animals. This was specific since it was not seen in the thymus or spleen. The consistent decrease in the number of CD4+ T cells in subcutaneous lymph nodes of mice from the animal model of autism may be related to the allergic symptoms frequently observed in ASD. Further research is necessary to characterize the immunological patterns in ASD and the connection with the pathophysiology of this disorder.

Acute Chagas disease in the state of Pará, Amazon Region: is it increasing?

Acute Chagas disease (ACD) has a distinct epidemiological profile in the Amazon Region, with cases and outbreaks of Trypanosoma cruzi infection being possibly related to the ingestion of contaminated food. Data on ACD in the state of Pará retrieved from 2000 to 2016 from the Brazilian Notifiable Diseases Information System (SINAN) were evaluated. During this period, 2,030 of the 16,807 reported cases were confirmed, with a higher incidence between the months of August and December, thus characterising a seasonal pattern of acute infection, and coinciding with the higher production of "açaí", one fruit likely involved in the oral transmission of the disease. Evaluation of the absolute numbers of confirmed ACD cases secondary to oral infection suggests that infection through this route increased during the 2010-2016 period, differing from what was recorded in terms of vectorial or other infection routes. These findings point to the need of intensifying strategies to prevent or substantially reduce oral transmission.

Sphingosine-1-Phosphate Receptor 1 Is Involved in Non-Obese Diabetic Mouse Thymocyte Migration Disorders.

NOD (non-obese diabetic) mice spontaneously develop type 1 diabetes following T cell-dependent destruction of pancreatic β cells. Several alterations are observed in the NOD thymus, including the presence of giant perivascular spaces (PVS) filled with single-positive (SP) CD4⁺ and CD8⁺ T cells that accumulate in the organ. These cells have a decreased expression of membrane CD49e (the α5 integrin chain of the fibronectin receptor VLA-5 (very late antigen-5). Herein, we observed lower sphingosine-1-phosphate receptor 1 (S1P1) expression in NOD mouse thymocytes when compared with controls, mainly in the mature SP CD4⁺CD62Lhi and CD8⁺CD62Lhi subpopulations bearing the CD49e− phenotype. In contrast, differences in S1P1 expression were not observed in mature CD49e⁺ thymocytes. Functionally, NOD CD49e− thymocytes had reduced S1P-driven migratory response, whereas CD49e⁺ cells were more responsive to S1P. We further noticed a decreased expression of the sphingosine-1-phosphate lyase (SGPL1) in NOD SP thymocytes, which can lead to a higher sphingosine-1-phosphate (S1P) expression around PVS and S1P1 internalization. In summary, our results indicate that the modulation of S1P1 expression and S1P/S1P1 interactions in NOD mouse thymocytes are part of the T-cell migratory disorder observed during the pathogenesis of type 1 diabetes.

Zika Virus Infection in the Elderly: Possible Relationship with Guillain-Barré Syndrome.

The Zika virus (ZIKV) outbreak in French Polynesia, in 2013, and in Brazil, in 2015, was correlated with neurological complications, which comprised, among others, congenital microcephaly and Guillain-Barré syndrome (GBS), which includes a group of acute autoimmune neuropathies generally reported after respiratory or gastrointestinal infectious diseases. Despite being relatively rare, the incidence rate of GBS rises with age, which makes GBS more frequent in the elderly, in whom it is also a more severe disease with slower recovery than in younger patients. Different forms of GBS have been described having diagnostic confirmation of a previous infection with the ZIKV virus. Although we do not have enough evidence that elderly people are a particularly susceptible population to developing GBS following ZIKV infection, this is plausible. We should consider this possibility, particularly taking into account that aging subjects are more susceptible to infections. In this context, a deeper understanding of how the immune system in the elderly functions in relation to ZIKV infection is necessary, as well as an understanding of what kind of alterations of the nervous system such an infection triggers in the elderly, beyond GBS. This will be relevant for better therapeutic interventions and for designing vaccine candidates that can be applied in an aging population, particularly those prone to develop ZIKV-induced autoimmunity.

Laminin-database v.2.0: an update on laminins in health and neuromuscular disorders.

The laminin (LM)-database, hosted at http://www.lm.lncc.br, was published in the NAR database 2011 edition. It was the first database that provided comprehensive information concerning a non-collagenous family of extracellular matrix proteins, the LMs. In its first version, this database contained a large amount of information concerning LMs related to health and disease, with particular emphasis on the haemopoietic system. Users can easily access several tabs for LMs and LM-related molecules, as well as LM nomenclatures and direct links to PubMed. The LM-database version 2.0 integrates data from several publications to achieve a more comprehensive knowledge of LMs in health and disease. The novel features include the addition of two new tabs, 'Neuromuscular Disorders' and 'miRNA--LM Relationship'. More specifically, in this updated version, an expanding set of data has been displayed concerning the role of LMs in neuromuscular and neurodegenerative diseases, as well as the putative involvement of microRNAs. Given the importance of LMs in several biological processes, such as cell adhesion, proliferation, differentiation, migration and cell death, this upgraded version expands for users a panoply of information, regarding complex molecular circuitries that involve LMs in health and disease, including neuromuscular and neurodegenerative disorders.

CD4(+)CD25(High) Treg cells in HIV/HTLV co-infected patients with neuropathy: high expression of Alpha4 integrin and lower expression of Foxp3 transcription factor.

BACKGROUND: Regulatory CD4 T cells (Tregs) are critical in maintaining the homeostasis of the immune system. Quantitative or phenotypic alterations and functional impairment of Tregs have been associated with the development of pathologies including those of the central nervous system. Individuals with HIV-1/HTLV-1 co-infection are more prone to develop neurological complications. The aim of this study was to characterize phenotypically Treg cells in HIV-1/HTLV-1 co-infected Mozambican individuals presenting neurological symptoms. METHODS: A cross-sectional study was conducted among HIV-infected individuals presentingneurological symptoms, with and without HTLV co-infection, and blood donors. Peripheral bloodmononuclear cells were stained with monoclonal antibodies conjugated with fluorochromes to quantifyTregs and activated T cells by four colors flow cytometry. RESULTS: Higher Treg cell frequency (10.6%) was noted in HIV-1/HTLV-1 co-infected group with neurological symptoms when compared to HIV-1 mono-infected group with neurological symptoms (0.38%, p = 0.003) and control group (0.9%, p = 0.0105). An inverse correlation between Foxp3 and CD49d expression was observed in all study groups (rh = -0.71, p = 0.001). In addition, increased levels of Treg cells in co-infected patients were strongly associated with total activated CD4 T cells (rh = 0.8, p = 0.01). CONCLUSION: Treg cells in co-infected patients present phenotypic alterations and might have dysfunction marked by low expression of Foxp3 and increased expression of molecules not frequently seen on Treg cells, such as CD49d. These alterations may be related to (1) changes in Treg cell trafficking and migration, possibly making those cells susceptible to HIV infection, and (2) inability to control the activation and proliferation of effector T lymphocytes.

HAM/TSP-derived HTLV-1-infected T cell lines promote morphological and functional changes in human astrocytes cell lines: possible role in the enhanced T cells recruitment into Central Nervous System.

BACKGROUND: The mechanisms through which HTLV-1 leads to and maintains damage in the central nervous system of patients undergoing HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) are still poorly understood. In recent years, increasing evidence indicates that, not only lymphocytes but also glial cells, in particular astrocytes, play a role in the pathophysiology of HAM/TSP. In this study we used a model of co-culture between human HTLV-1-infected (CIB and C91PL) and non-infected (CEM) T lymphocyte cell lines and astrocyte (U251 and U87) cell lines to mimic the in vivo T cell-astrocyte interactions. RESULTS: We first observed that CIB and C91PL adhere strongly to cultured astrocytes cell lines, and that co-cultures of HTLV-1 infected and astrocyte cell lines cells resulted in rapid syncytium formation, accompanied by severe morphological alterations and increased apoptotic cell death of astrocyte cells. Additionally, cultures of astrocyte cell lines in presence of supernatants harvested from HTLV-1-infected T cell cultures resulted in significant increase in the mRNA of CCL2, CXCL1, CXCL2, CXCL3, CXCL10, IL-13, IL-8, NFKB1, TLR4, TNF, MMP8 and VCAM1, as compared with the values obtained when we applied supernatants of non-infected T- cell lines. Lastly, soluble factors secreted by cultured astrocytic cell lines primed through 1-h interaction with infected T cell lines, further enhanced migratory responses, as compared to the effect seen when supernatants from astrocytic cell lines were primed with non-infected T cell lines. CONCLUSION: Collectively, our results show that HTLV-1 infected T lymphocyte cell lines interact strongly with astrocyte cell lines, leading to astrocyte damage and increased secretion of attracting cytokines, which in turn may participate in the further attraction of HTLV-1-infected T cells into central nervous system (CNS), thus amplifying and prolonging the immune damage of CNS.