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.

Characterization of Systemic Disease Development and Paw Inflammation in a Susceptible Mouse Model of Mayaro Virus Infection and Validation Using X-ray Synchrotron Microtomography.

Mayaro virus (MAYV) is an emerging arthropod-borne virus endemic in Latin America and the causative agent of arthritogenic febrile disease. Mayaro fever is poorly understood; thus, we established an in vivo model of infection in susceptible type-I interferon receptor-deficient mice (IFNAR-/-) to characterize the disease. MAYV inoculations in the hind paws of IFNAR-/- mice result in visible paw inflammation, evolve into a disseminated infection and involve the activation of immune responses and inflammation. The histological analysis of inflamed paws indicated edema at the dermis and between muscle fibers and ligaments. Paw edema affected multiple tissues and was associated with MAYV replication, the local production of CXCL1 and the recruitment of granulocytes and mononuclear leukocytes to muscle. We developed a semi-automated X-ray microtomography method to visualize both soft tissue and bone, allowing for the quantification of MAYV-induced paw edema in 3D with a voxel size of 69 µm3. The results confirmed early edema onset and spreading through multiple tissues in inoculated paws. In conclusion, we detailed features of MAYV-induced systemic disease and the manifestation of paw edema in a mouse model extensively used to study infection with alphaviruses. The participation of lymphocytes and neutrophils and expression of CXCL1 are key features in both systemic and local manifestations of MAYV disease.

SARS-CoV-2 infected children form early immune memory responses dominated by nucleocapsid-specific CD8+ T cells and antibodies.

This is the third year of the SARS-CoV-2 pandemic, and yet most children remain unvaccinated. COVID-19 in children manifests as mostly mild or asymptomatic, however high viral titers and strong cellular and humoral responses are observed upon acute infection. It is still unclear how long these responses persist, and if they can protect from re-infection and/or disease severity. Here, we analyzed immune memory responses in a cohort of children and adults with COVID-19. Important differences between children and adults are evident in kinetics and profile of memory responses. Children develop early N-specific cytotoxic T cell responses, that rapidly expand and dominate their immune memory to the virus. Children's anti-N, but not anti-S, antibody titers increase over time. Neutralization titers correlate with N-specific antibodies and CD8+T cells. However, antibodies generated by infection do not efficiently cross-neutralize variants Gamma or Delta. Our results indicate that mechanisms that protect from disease severity are possibly different from those that protect from reinfection, bringing novel insights for pediatric vaccine design. They also underline the importance of vaccination in children, who remain at risk for COVID-19 despite having been previously infected.

Identification and characterization of the anti-SARS-CoV-2 activity of cationic amphiphilic steroidal compounds.

The ongoing COVID-19 pandemic caused a significant loss of human lives and a worldwide decline in quality of life. Treatment of COVID-19 patients is challenging, and specific treatments to reduce COVID-19 aggravation and mortality are still necessary. Here, we describe the discovery of a novel class of epiandrosterone steroidal compounds with cationic amphiphilic properties that present antiviral activity against SARS-CoV-2 in the low micromolar range. Compounds were identified in screening campaigns using a cytopathic effect-based assay in Vero CCL81 cells, followed by hit compound validation and characterization. Compounds LNB167 and LNB169 were selected due to their ability to reduce the levels of infectious viral progeny and viral RNA levels in Vero CCL81, HEK293, and HuH7.5 cell lines. Mechanistic studies in Vero CCL81 cells indicated that LNB167 and LNB169 inhibited the initial phase of viral replication through mechanisms involving modulation of membrane lipids and cholesterol in host cells. Selection of viral variants resistant to steroidal compound treatment revealed single mutations on transmembrane, lipid membrane-interacting Spike and Envelope proteins. Finally, in vivo testing using the hACE2 transgenic mouse model indicated that SARS-CoV-2 infection could not be ameliorated by LNB167 treatment. We conclude that anti-SARS-CoV-2 activities of steroidal compounds LNB167 and LNB169 are likely host-targeted, consistent with the properties of cationic amphiphilic compounds that modulate host cell lipid biology. Although effective in vitro, protective effects were cell-type specific and did not translate to protection in vivo, indicating that subversion of lipid membrane physiology is an important, yet complex mechanism involved in SARS-CoV-2 replication and pathogenesis.

Kinetics of peripheral blood neutrophils in severe coronavirus disease 2019.

OBJECTIVES: Emerging evidence of dysregulation of the myeloid cell compartment urges investigations on neutrophil characteristics in coronavirus disease 2019 (COVID-19). We isolated neutrophils from the blood of COVID-19 patients receiving general ward care and from patients hospitalised at intensive care units (ICUs) to explore the kinetics of circulating neutrophils and factors important for neutrophil migration and activation. METHODS: Multicolour flow cytometry was exploited for the analysis of neutrophil differentiation and activation markers. Multiplex and ELISA technologies were used for the quantification of protease, protease inhibitor, chemokine and cytokine concentrations in plasma. Neutrophil polarisation responses were evaluated microscopically. Gelatinolytic and metalloproteinase activity in plasma was determined using a fluorogenic substrate. Co-culturing healthy donor neutrophils with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) allowed us to investigate viral replication in neutrophils. RESULTS: Upon ICU admission, patients displayed high plasma concentrations of granulocyte-colony-stimulating factor (G-CSF) and the chemokine CXCL8, accompanied by emergency myelopoiesis as illustrated by high levels of circulating CD10-, immature neutrophils with reduced CXCR2 and C5aR expression. Neutrophil elastase and non-metalloproteinase-derived gelatinolytic activity were increased in plasma from ICU patients. Significantly higher levels of circulating tissue inhibitor of metalloproteinase 1 (TIMP-1) in patients at ICU admission yielded decreased total MMP proteolytic activity in blood. COVID-19 neutrophils were hyper-responsive to CXCL8 and CXCL12 in shape change assays. Finally, SARS-CoV-2 failed to replicate inside human neutrophils. CONCLUSION: Our study provides detailed insights into the kinetics of neutrophil phenotype and function in severe COVID-19 patients, and supports the concept of an increased neutrophil activation state in the circulation.

Pediatric COVID-19 patients in South Brazil show abundant viral mRNA and strong specific anti-viral responses.

COVID-19 manifests as a milder disease in children than adults, but the underlying mechanisms are not fully characterized. Here we assess the difference in cellular or humoral immune responses of pediatric and adult COVID-19 patients to see if these factors contribute to the severity dichotomy. Children's non-specific immune profile is dominated by naive lymphocytes and HLA-DRhighCX3CR1low dendritic cells; meanwhile, children show strong specific antibody and T cell responses for viral structural proteins, with their T cell responses differing from adults by having weaker CD8+TNF+ T cells responses to S peptide pool but stronger responses to N and M peptide pools. Finally, viral mRNA is more abundant in pediatric patients. Our data thus support a scenario in which SARS-CoV-2 infected children contribute to transmission yet are less susceptible to COVID-19 symptoms due to strong and differential responses to the virus.

Elevated Glucose Levels Favor SARS-CoV-2 Infection and Monocyte Response through a HIF-1α/Glycolysis-Dependent Axis.

COVID-19 can result in severe lung injury. It remained to be determined why diabetic individuals with uncontrolled glucose levels are more prone to develop the severe form of COVID-19. The molecular mechanism underlying SARS-CoV-2 infection and what determines the onset of the cytokine storm found in severe COVID-19 patients are unknown. Monocytes and macrophages are the most enriched immune cell types in the lungs of COVID-19 patients and appear to have a central role in the pathogenicity of the disease. These cells adapt their metabolism upon infection and become highly glycolytic, which facilitates SARS-CoV-2 replication. The infection triggers mitochondrial ROS production, which induces stabilization of hypoxia-inducible factor-1α (HIF-1α) and consequently promotes glycolysis. HIF-1α-induced changes in monocyte metabolism by SARS-CoV-2 infection directly inhibit T cell response and reduce epithelial cell survival. Targeting HIF-1ɑ may have great therapeutic potential for the development of novel drugs to treat COVID-19.

[Left ventricular papillary fibroelastoma].

We evaluated the case of a patient with Papillary Fibroelastoma (PFE) that presented embolization to the upper right limb. The patient was submitted to percutaneous embolectomy, with fragment removal. The diagnosis was confirmed by transthoracic echocardiogram and anatomopathological analysis of the fragment. The patient chose to undergo the conservative clinical treatment and the follow-up has shown good evolution with no disease recurrence to date. We decided to use this rare and interesting case with the objective of reviewing the current literature and discuss the best therapeutic management.

Fibroelastoma papilífero do ventrículo esquerdo / Fibroelastoma papilar del ventrículo izquierdo / Left ventricular papillary fibroelastoma

Avaliamos o caso de uma paciente portadora de fibroelastoma papilífero (FEP) que apresentou embolização para membro superior direito. A paciente foi submetida à embolectomia percutânea, com retirada do fragmento. O diagnóstico foi confirmado por ecocardiograma transtorácico e exame anatomopatológico. Optou-se pelo tratamento clínico conservador e acompanhamento da paciente, que mostrou boa evolução e não teve recorrência do quadro até o momento. Aproveitamos esse raro e interessante caso na intenção de revisar a literatura vigente e discutir a melhor conduta terapêutica.

We evaluated the case of a patient with Papillary Fibroelastoma (PFE) that presented embolization to the upper right limb. The patient was submitted to percutaneous embolectomy, with fragment removal. The diagnosis was confirmed by transthoracic echocardiogram and anatomopathological analysis of the fragment. The patient chose to undergo the conservative clinical treatment and the follow-up has shown good evolution with no disease recurrence to date. We decided to use this rare and interesting case with the objective of reviewing the current literature and discuss the best therapeutic management.

Evaluamos el caso de una paciente portadora de fibroelastoma papilar (FEP) que presentó embolización para miembro superior derecho. La paciente fue sometida a embolectomía percutánea, con retirada del fragmento. El diagnóstico fue confirmado por ecocardiograma transtoracico y examen anatomopatológico. Se optó por el tratamiento clínico conservador y seguimiento de la paciente, que mostró la buena evolución y no tuvo recurrencia del cuadro hasta el momento. Aprovechamos este raro e interesante caso en la intención de revisar la literatura vigente y discutir la mejor conducta terapéutica.