Comprehensive analysis of early T cell responses to acute Zika Virus infection during the first epidemic in Bahia, Brazil.

BACKGROUND: In most cases, Zika virus (ZIKV) causes a self-limited acute illness in adults, characterized by mild clinical symptoms that resolve within a few days. Immune responses, both innate and adaptive, play a central role in controlling and eliminating virus-infected cells during the early stages of infection. AIM: To test the hypothesis that circulating T cells exhibit phenotypic and functional activation characteristics during the viremic phase of ZIKV infection. METHODS: A comprehensive analysis using mass cytometry was performed on peripheral blood mononuclear cells obtained from patients with acute ZIKV infection (as confirmed by RT-PCR) and compared with that from healthy donors (HD). The frequency of IFN-γ-producing T cells in response to peptide pools covering immunogenic regions of structural and nonstructural ZIKV proteins was quantified using an ELISpot assay. RESULTS: Circulating CD4+ and CD8+ T lymphocytes from ZIKV-infected patients expressed higher levels of IFN-γ and pSTAT-5, as well as cell surface markers associated with proliferation (Ki-67), activation ((HLA-DR, CD38) or exhaustion (PD1 and CTLA-4), compared to those from HD. Activation of CD4+ and CD8+ memory T cell subsets, including Transitional Memory T Cells (TTM), Effector Memory T cells (TEM), and Effector Memory T cells Re-expressing CD45RA (TEMRA), was prominent among CD4+ T cell subset of ZIKV-infected patients and was associated with increased levels of IFN-γ, pSTAT-5, Ki-67, CTLA-4, and PD1, as compared to HD. Additionally, approximately 30% of ZIKV-infected patients exhibited a T cell response primarily directed against the ZIKV NS5 protein. CONCLUSION: Circulating T lymphocytes spontaneously produce IFN-γ and express elevated levels of pSTAT-5 during the early phase of ZIKV infection whereas recognition of ZIKV antigen results in the generation of virus-specific IFN-γ-producing T cells.

Usefulness of receptor binding domain protein-based serodiagnosis of COVID-19.

Objectives: This study evaluated the performance of recombinant receptor binding domain (RBD) protein-based enzyme-linked immunosorbent assays (RBD-ELISAs) for detecting anti-SARS-CoV-2 immunoglobulin (Ig) G and IgM antibodies. Methods: In this study, 705 sera from SARS-CoV-2-infected individuals and 315 sera from healthy individuals were analyzed. Results: The RBD-ELISA IgG exhibited high specificity (99.1%) and moderate sensitivity (48.0%), with an overall diagnostic accuracy of 73.5%. RBD-ELISA IgM demonstrated specificity at 94.6% and sensitivity at 51.1%, with an accuracy of 72.8%. Both assays displayed improved performance when analyzing samples collected 15-21 days post-symptom onset, achieving sensitivity and accuracy exceeding 88% and 90%, respectively. Combining RBD-ELISA IgG and IgM in parallel analysis enhanced sensitivity to 98.6% and accuracy to 96.2%. Comparing these RBD-ELISAs with commercially available tests, the study found overlapping sensitivity and similar specificity values. Notably, the combined RBD-ELISA IgG and IgM showed superior performance. Cross-reactivity analysis revealed low false-positive rates (4.4% for IgG, 3.7% for IgM), primarily with viral infections. Conclusion: This research underscores the potential of RBD-based ELISAs for COVID-19 diagnosis, especially when assessing samples collected 15-21 days post-symptom onset and utilizing a parallel testing approach. The RBD protein's immunogenicity and specificity make it a valuable tool for serodiagnosis, offering an alternative to polymerase chain reaction-based methods, particularly in resource-limited settings.

Prevalence and risk factors for long COVID after mild disease: A cohort study with a symptomatic control group.

Background: There is limited data on the prevalence and risk factors for long COVID and few prospective studies with appropriate control groups and adequate sample sizes. We performed a prospective study to determine the prevalence and risk factors for long COVID. Methods: We recruited individuals aged ≥15 years who were clinically suspected of having an acute SARS-CoV-2 infection from September 2020 to April 2021. We collected nasopharyngeal swabs three to five days following symptom onset for analysing using reverse transcriptase polymerase chain reaction (RT-PCR). We also collected clinical and sociodemographic characteristics from both SARS-CoV-2 positive and negative participants using structured questionnaires. We followed-up the participants via telephone interview to assess early outcomes and persistent symptoms. For COVID-19 cases, 5D-3L EuroQol questionnaire was used to assess the impact of symptoms on quality of life. Results: We followed 814 participants (412 COVID-19 positive and 402 COVID-19 negative persons). Most (n = 741/814) had mild symptoms. Both groups had similar sociodemographic and clinical characteristics, except for the hospitalization rate (15.8% in the COVID-19 positive vs 1.5% in the COVID-19 negative group). One month after disease onset, 122/412 (29.6%) individuals in the COVID-19 positive (long COVID) and 24 (6%) in the COVID-19 negative group reported residual symptoms. In the long COVID group, fatigue, olfactory disorder, and myalgia were the most frequent symptoms in the acute phase. Compared to recovered individuals, older age and having more than five symptoms during the acute phase were risk factors for long COVID. Quality of life was evaluated in 102 out of 122 cases of long COVID, with 57 (55.9%) reporting an impact in at least one dimension of the European Quality of Life 5 Dimensions 3 Level (EQ-5D-3L) questionnaire. Conclusions: In this prospective study consisting predominantly of individuals with mild disease, the persistence of symptoms after an acute respiratory illness was associated with a diagnosis of COVID-19. Polysymptomatic acute disease and older age were risk factors for long COVID.

Assembling the layers of the hematopoietic system: A window of opportunity for thymopoiesis in the embryo.

During embryonic development, several independent generations of hematopoietic cells were identified. They occur in the yolk sac and the intra-embryonic major arteries, in a narrow window of development. They arise sequentially, starting with primitive erythrocytes in the yolk sac blood islands, progressing to less differentiated erythromyeloid progenitors still in the yolk sac, and culminating with multipotent progenitors, some of which will generate the adult hematopoietic stem cell compartment. All these cells contribute to the formation of a layered hematopoietic system that reflects adaptative strategies to the fetal environment and the embryo's needs. It is mostly composed, at these stages, of erythrocytes and tissue-resident macrophages both of yolk sac origin, the latter persisting throughout life. We propose that subsets of lymphocytes of embryonic origin derive from a different intra-embryonic generation of multipotent cells occurring before the emergence of hematopoietic stem cell progenitors. These multipotent cells have a limited lifespan and generate cells that provide basic protection against pathogens before the adaptive immune system is functional, contribute to tissue development and homeostasis, and shape the establishment of a functional thymus. Understanding the properties of these cells will impact the understanding of childhood leukemia and of adult autoimmune pathology and thymic involution.

Genomic monitoring unveils a high prevalence of severe acute respiratory syndrome coronavirus 2 Omicron variant in vaccine breakthrough cases in Bahia, Brazil.

OBJECTIVE: Genome sequencing has been proved to be an excellent tool to monitor the molecular epidemiology of the disease caused by severe acute respiratory syndrome coronavirus 2, i.e., coronavirus disease 2019. Some reports of infected, vaccinated individuals have aroused great interest because they are primarily being infected with circulating variants of concern. To investigate the cases of infected, vaccinated individuals in Salvador, Bahia, Brazil, we performed genomic monitoring to estimate the magnitude of the different variants of concern in these cases. METHODS: Nasopharyngeal swabs from infected (symptomatic and asymptomatic), vaccinated or unvaccinated individuals (n=29), and quantitative reverse transcription polymerase chain reaction cycle threshold value (Ct values) of ≤30 were subjected to viral sequencing using nanopore technology. RESULTS: Our analysis revealed that the Omicron variant was found in 99% of cases and the Delta variant was found in only one case. Infected, fully vaccinated patients have a favorable clinical prognosis; however, within the community, they become viral carriers with the aggravating factor of viral dissemination of variants of concern not neutralized by the currently available vaccines. CONCLUSION: It is important to acknowledge the limitations of these vaccines and to develop new vaccines to emergent variants of concern, as is the case of influenza vaccine; going through new doses of the same coronavirus vaccines is "more of the same."

Reabilitação funcional e barreiras para atividade física na COVID-longa: um ensaio clínico randomizado / Functional rehabilitation and barriers to physical activity after COVID-19: a randomized clinical trial

O estudo teve como objetivo analisar as barreiras percebidas à prática de atividade física durante um programa de treinamento multicomponente em adultos e idosos pós infecção por COVID-19. Realizou-se um ensaio clínico randomizado com 40 participantes (19 grupo controle e 21 grupo intervenção). Foram coletadas informações sociodemográficas, de saúde e de barreiras para a prática de atividade física, antes, 12 e 24 semanas após o início da intervenção. A medida das barreiras para a prática de atividade física foi obtida por meio de uma escala válida composta por 16 itens. As diferen-ças de barreiras entre os grupos e ao longo de tempo foi analisada a partir das Equações de Estimativa Generalizada, α = 0,05. As barreiras mais citadas pelos dois grupos na linha de base foram "Preguiça, cansaço ou desânimo" (71%), "Dores, lesões ou incapacidade" (38%) e "Falta de motivação" (48%). As análises principais indicaram que ambos os grupos tiveram redução na frequência da barreira "Pre-guiça, cansaço ou desânimo" na 12ª semana (p = 0,003), porém voltando aos valores iniciais na 24ª semana (p = 0,441). Já a barreira "Por causa da epidemia de coronavírus" foi reduzida na 12ª semana (p = 0,704) e ainda mais reduzida na 24ª semana (p = 0,158), comportamento também similar entre os grupos. Como principal conclusão, barreiras para atividade física podem ser reduzidas pela parti-cipação em programas de exercício supervisionado e recomendação para a prática de atividade física

The study aimed to analyze perceived barriers to physical activity during a multicomponent training pro-gram in adults and seniors post-COVID-19 infection. A randomized clinical trial was conducted with 40 participants (19 control group and 21 intervention group). Sociodemographic, health, and barriers to physical activity information were collected before, 12 and 24 weeks after the start of the intervention. The measure of barriers to physical activity was obtained through a valid scale composed of 16 items. Differences in barriers between groups and over time were analyzed using Generalized Estimating Equations, α = 0.05. The most frequently mentioned barriers at baseline by both groups were "Laziness, fatigue, or lack of enthusiasm" (71%), "Pain, injuries, or disability" (38%), and "Lack of motivation" (48%). The main analyses indicated that both groups had a reduction in the frequency of the barrier "Laziness, fatigue, or lack of enthusiasm" at week 12 (p = 0.003), but returned to initial values at week 24 (p = 0.441). The barrier "Because of the coronavirus epidemic" was reduced in week 12 (p = 0.704) and further reduced in week 24 (p = 0.158), with a similar pattern between groups. The key conclusion is that barriers to physical activity can be reduced through participation in supervised exercise programs and recommendations for physical activity

Genomic monitoring unveils a high prevalence of severe acute respiratory syndrome coronavirus 2 Omicron variant in vaccine breakthrough cases in Bahia, Brazil

SUMMARY OBJECTIVE: Genome sequencing has been proved to be an excellent tool to monitor the molecular epidemiology of the disease caused by severe acute respiratory syndrome coronavirus 2, i.e., coronavirus disease 2019. Some reports of infected, vaccinated individuals have aroused great interest because they are primarily being infected with circulating variants of concern. To investigate the cases of infected, vaccinated individuals in Salvador, Bahia, Brazil, we performed genomic monitoring to estimate the magnitude of the different variants of concern in these cases. METHODS: Nasopharyngeal swabs from infected (symptomatic and asymptomatic), vaccinated or unvaccinated individuals (n=29), and quantitative reverse transcription polymerase chain reaction cycle threshold value (Ct values) of ≤30 were subjected to viral sequencing using nanopore technology. RESULTS: Our analysis revealed that the Omicron variant was found in 99% of cases and the Delta variant was found in only one case. Infected, fully vaccinated patients have a favorable clinical prognosis; however, within the community, they become viral carriers with the aggravating factor of viral dissemination of variants of concern not neutralized by the currently available vaccines. CONCLUSION: It is important to acknowledge the limitations of these vaccines and to develop new vaccines to emergent variants of concern, as is the case of influenza vaccine; going through new doses of the same coronavirus vaccines is "more of the same."

Systematic review - alopecia areata and tofacitinib in paediatric patients.

INTRODUCTION: Alopecia Areata is a nonscarring hair loss disorder and is the most common hair loss cause in children. It is a chronic autoimmune disorder with a severe psychological impact in patients' lives. JAK inhibitors, in particular Tofacitinib, have been having promising results on Alopecia Areata Treatment. In this study we aimed to do a Systematic Review on the role of Tofacitinib (either orally or topically), considering efficacy and safety, in treating children with Alopecia Areata. MATERIALS AND METHODS: PubMed, Cochrane and Web of Science databases were searched (up to 1st of September of 2021) looking for Tofacitinib (all text/all fields) and MeSH/Keyword term Alopecia Areata. RESULTS AND CONCLUSIONS: We included 14 studies and 64 cases in the Systematic Review. From these, 12 were considering systemic administration (47 patients) and two were considering topical administration (17 patients). Responsiveness was as high as 81.3%. The responsiveness was similar among different genders (78.6% in males and 80.0% in females) and either whether administration was topic (70.6% responsiveness) or systemic (85.1% responsiveness). Adverse effects were rare and, when present, were mild. Studies shows promising results in what considers the efficacy and safety of Tofacitinib in the treatment of Alopecia Areata. As the available evidence to date is of low quality, further randomised studies are required to confirm these findings.

A Critical Analysis of the COVID-19 Hospitalization Network in Countries with Limited Resources.

To effectively combat the COVID-19 pandemic, countries with limited resources could only allocate intensive and non-intensive care units to a low number of regions. In this work, we evaluated the actual displacement of infected patients in search of care, aiming to understand how the networks of planned and actual hospitalizations take place. To assess the flow of hospitalizations outside the place of residence, we used the concepts of complex networks. Our findings indicate that the current distribution of health facilities in Bahia, Brazil, is not sufficient to effectively reduce the distances traveled by patients with COVID-19 who require hospitalization. We believe that unnecessary trips to distant hospitals can put both the sick and the healthy involved in the transport process at risk, further delaying the stabilization of the COVID-19 pandemic in each region of the state of Bahia. From the results found, we concluded that, to mitigate this situation, the implementation of health units in countries with limited resources should be based on scientific methods, and international collaborations should be established.

Haff Disease in Salvador, Brazil, 2016-2021: Attack rate and detection of toxin in fish samples collected during outbreaks and disease surveillance.

Background: From late 2016 to early 2021, cases of Haff disease, a rare cause of rhabdomyolysis, possibly due to poisoning by palytoxin-like compounds in seafood, were detected in Salvador, Brazil. Surveillance was established to detect additional cases aiming at describing the clinical characteristics of the cases, identifying associated factors, estimating disease attack rate, and investigating the presence of biotoxins and trace metals in selected fish specimens obtained from cases. Method: Between December/2016-January/2021, surveillance investigated Haff disease suspected cases, and obtained clinical and fish samples to test. Findings: Of 65 cases investigated during the 2016-2017 outbreak, 43 (66%) had high creatine phosphokinase (CPK) levels. Among those with laboratory-confirmed rhabdomyolysis, 38 (88%) were hospitalized, 11 (26%) required intensive care, and three (7%) dialysis. Ingestion of marine fish 24h before disease onset was reported by 74% of the cases with elevated CPK and by 41% of those without CPK measurement (P=0·02). Attack rate for individuals who ate fish related to the outbreak was 55%. Following this outbreak, surveillance identified 12 suspected cases between 2017-2019, and a second outbreak in 2020-2021, with 16 laboratory-confirmed rhabdomyolysis patients (five required intensive care; one died). No traces of ciguatoxins and metals were detected in fish specimens obtained in 2016, found to be Seriola rivoliana. Some fish samples from 2020 were screened for palytoxin (PlTX)-like compounds and contained detectable levels of molecule fragments characteristics of isobaric PlTX, ovatoxin-a (OVTX-a), OVTX-b and OVTX-d. Interpretation: These findings support the hypothesis that compounds related to PlTX accumulated in marine fish may be the toxic agent causing the disease. Haff disease is a life-threatening condition, requiring clinical suspicion for patients with sudden-onset myalgia following fish ingestion. Suspected cases should be reported to health authorities for investigation.

Interleukin-10 induces interferon-γ-dependent emergency myelopoiesis.

In emergency myelopoiesis (EM), expansion of the myeloid progenitor compartment and increased myeloid cell production are observed and often mediated by the pro-inflammatory cytokine interferon gamma (IFN-γ). Interleukin-10 (IL-10) inhibits IFN-γ secretion, but paradoxically, its therapeutic administration to humans causes hematologic changes similar to those observed in EM. In this work, we use different in vivo systems, including a humanized immune system mouse model, to show that IL-10 triggers EM, with a significant expansion of the myeloid progenitor compartment and production of myeloid cells. Hematopoietic progenitors display a prominent IFN-γ transcriptional signature, and we show that IFN-γ mediates IL-10-driven EM. We also find that IL-10, unexpectedly, reprograms CD4 and CD8 T cells toward an activation state that includes IFN-γ production by these T cell subsets in vivo. Therefore, in addition to its established anti-inflammatory properties, IL-10 can induce IFN-γ production and EM, opening additional perspectives for the design of IL-10-based immunotherapies.

NK Cell Responses in Zika Virus Infection Are Biased towards Cytokine-Mediated Effector Functions.

Zika virus (ZIKV) is a mosquito-borne flavivirus that has emerged as a global concern because of its impact on human health. ZIKV infection during pregnancy can cause microcephaly and other severe brain defects in the developing fetus and there have been reports of the occurrence of Guillain-Barré syndrome in areas affected by ZIKV. NK cells are activated during acute viral infections and their activity contributes to a first line of defense because of their ability to rapidly recognize and kill virus-infected cells. To provide insight into NK cell function during ZIKV infection, we have profiled, using mass cytometry, the NK cell receptor-ligand repertoire in a cohort of acute ZIKV-infected female patients. Freshly isolated NK cells from these patients contained distinct, activated, and terminally differentiated, subsets expressing higher levels of CD57, NKG2C, and KIR3DL1 as compared with those from healthy donors. Moreover, KIR3DL1+ NK cells from these patients produced high levels of IFN-γ and TNF-α, in the absence of direct cytotoxicity, in response to in vitro stimulation with autologous, ZIKV-infected, monocyte-derived dendritic cells. In ZIKV-infected patients, overproduction of IFN-γ correlated with STAT-5 activation (r = 0.6643; p = 0.0085) and was mediated following the recognition of MHC class 1-related chain A and chain B molecules expressed by ZIKV-infected monocyte-derived dendritic cells, in synergy with IL-12 production by the latter cells. Together, these findings suggest that NK cells contribute to the generation of an efficacious adaptive anti-ZIKV immune response that could potentially affect the outcome of the disease and/or the development of persistent symptoms.

Zika Virus Congenital Syndrome and MTOR gene variants: insights from a family of dizygotic twins.

Congenital Zika virus syndrome (CZS) is associated with damage to neural progenitor cells by ZIKA virus infection. There are no accurate statistics on the percentage of pregnant mothers who have had babies affected by the syndrome. Few cases of discordant twins have been described in the literature and, therefore, we hypothesize that the genetic background of the progeny and/or mother may play a role in the fate of the syndrome. We performed a complete exome sequencing in a set of dizygotic individuals and their parents. After that, we selected discordant variants on the MTOR gene between the affected and unaffected twin and we observed a mutation (rs2295079), placed in a region restricted to proximal 5'-UTR, as a strong possible causal variant. In addition, in most brain tissues (including fetal brain) evaluated for expression quantitative trait loci (eQTL), this locus is strongly correlated with post-translational modifications of histones (promoter and enhancer marks) and hypersensitivity to DNAse I (open chromatin mark). Taken together, our data suggest that changes in the MTOR gene may be related to CZS. Additional functional studies should be carried out to prove how and why a MTOR mutation can predispose the fetus to the syndrome.

Óbitos por Covid -19 no estado da Bahia: da captação à publicação / Deaths by Covid -19 in the state of Bahia: from capture to publication / Muertes por Covid -19 en el estado de Bahía: desde la captura hasta la publicación

Identificada inicialmente em Wuhan, na China, a Covid-19 causada pelo novo coronavírus da síndrome respiratória (SARS-CoV-2) provocou um alerta global. Diante desse cenário emergencial, o Brasil, assim como outros países, tem vivenciando grandes mudanças nas ações e serviços em saúde. Na Bahia, a velocidade de disseminação da doença ocasionou um aumento significativo na notificação de casos e óbitos, promovendo uma restruturação no processo de trabalho da vigilância epidemiológica estadual para atuar de forma oportuna na captação, investigação e classificação de casos, e publicação e recomendações de medidas sanitárias. Este trabalho objetiva descrever o processo de trabalho na vigilância epidemiológica de óbitos por Covid-19 no estado da Bahia. Trata-se de um relato de experiência do processo de trabalho de análise dos óbitos por Covid-19 no período de março a dezembro de 2020. A trajetória metodológica foi estruturada em análise documental, relatórios de investigação, ferramentas de notificação do Ministério da Saúde e outros sistemas oficiais, como o Formulário Eletrônico do SUS ­ FormSUS, produzido pela Diretoria de Vigilância Epidemiológica para identificar os óbitos por Covid-19 nos hospitais da Bahia em tempo hábil, facilitando o processo de captação, investigação, análise e publicação de informação de mortalidade. Observou-se que a estruturação de um processo organizado e aplicado ao fluxo de trabalho possibilitou a qualificação e a fidedignidade das informações dos óbitos por Covid-19, garantindo mudanças incrementais no âmbito da vigilância e segurança das informações publicadas, essenciais para o planejamento das ações de prevenção e controle.

Initially identified in Wuhan, China, Covid-19 caused by the respiratory syndrome coronavirus (SARS-CoV-2) has triggered a global alert. Faced with this emergency scenario, Brazil, like other countries, has been experiencing major changes in health actions and services. In the state of Bahia, the rapid spread of the disease increased significantly the notification of cases and deaths, promoting a restructuring in the work process of state epidemiological surveillance to act in a timely manner in capturing, investigating and classifying cases, publishing and recommending sanitary measures. This paper aims at describing the work process in the epidemiological surveillance of deaths by Covid-19 in the state of Bahia. This is an experience report of Covid-19 death analysis work process, from March to December 2020. The methodological trajectory was structured in document analysis, investigation reports, notification tools from the Ministry of Health and others official systems, and the SUS FormSUS Electronic Form, produced by the Epidemiological Surveillance Directorate (Divep) to identify deaths by Covid-19 by hospitals in Bahia in a timely manner, facilitating the process of capturing, investigating, analyzing and publishing information of mortality. It was observed that the structuring of an organized process and application to the workflow enabled the qualification and reliability of death information by Covid-19, ensuring incremental changes in the scope of surveillance and security in the published information, essential for planning prevention and control actions.

Inicialmente identificado en Wuhan, China, el covid-19 causante del síndrome respiratorio agudo grave (SARS-CoV-2) ha desencadenado una alerta global. Ante este escenario de emergencia, Brasil, al igual que otros países, ha venido experimentando importantes cambios en las acciones y servicios de salud. En Bahía, la velocidad de propagación de la enfermedad provocó un aumento significativo en la notificación de casos y defunciones, promoviendo una reestructuración en el proceso de trabajo de la vigilancia epidemiológica estadual para actuar de manera oportuna en la recopilación, investigación, clasificación de casos, publicación y recomendación de medidas preventivas. Este artículo tiene como objetivo describir el proceso de trabajo en la vigilancia epidemiológica de las muertes por covid-19 en el estado de Bahía. Es un informe de experiencia del proceso de trabajo de análisis de muertes por covid-19, de marzo a diciembre de 2020. La trayectoria metodológica se estructuró en análisis de documentos, informes de investigación, herramientas de notificación del Ministerio de Salud y otros sistemas oficiales, así como el Formulario Electrónico SUS FormSUS, elaborado por la Dirección de Vigilancia Epidemiológica (Divep) para identificar las muertes por covid-19 en los hospitales de Bahía de manera oportuna, lo que facilita el proceso de recopilación, investigación, análisis y publicación de información sobre mortalidad. Se observó que la estructuración de un proceso organizado y aplicado al flujo de trabajo permitió la calificación y confiabilidad de la información de muertes por covid-19, asegurando cambios incrementales en el alcance de la vigilancia y seguridad de la información publicada, fundamental para planificar la prevención y el control.

A wave of bipotent T/ILC-restricted progenitors shapes the embryonic thymus microenvironment in a time-dependent manner.

During embryonic development, multiple waves of hematopoietic progenitors with distinct lineage potential are differentially regulated in time and space. Two different waves of thymic progenitors colonize the fetal thymus where they contribute to thymic organogenesis and homeostasis. The origin, the lineage differentiation potential of the first wave, and their relative contribution in shaping the thymus architecture, remained, however, unclear. Here, we show that the first wave of thymic progenitors comprises a unique population of bipotent T and innatel lymphoid cells (T/ILC), generating a lymphoid tissue inducer cells (LTi's), in addition to invariant Vγ5+ T cells. Transcriptional analysis revealed that innate lymphoid gene signatures and, more precisely, the LTi-associated transcripts were expressed in the first, but not in the second, wave of thymic progenitors. Depletion of early thymic progenitors in a temporally controlled manner showed that the progeny of the first wave is indispensable for the differentiation of autoimmune regulator-expressing medullary thymic epithelial cells (mTECs). We further show that these progenitors are of strict hematopoietic stem cell origin, despite the overlap between lymphopoiesis initiation and the transient expression of lymphoid-associated transcripts in yolk sac (YS) erythromyeloid-restricted precursors. Our work highlights the relevance of the developmental timing on the emergence of different lymphoid subsets, required for the establishment of a functionally diverse immune system.

Clinical and laboratory findings of acute Zika virus infection in patients from Salvador during the first Brazilian epidemic

Abstract Several major epidemics of Zika fever, caused by the ZIKA virus (ZIKV), have emerged in Brazil since early 2015, eventually spreading to other countries on the South American continent. The present study describes the clinical manifestations and laboratory findings of patients with confirmed acute ZIKV infection during the first epidemic that occurred in Salvador, Brazil. All included patients were seen at the emergency room of a private tertiary hospital located in Salvador, Brazil from 2015 through 2017. Patients were considered eligible if signs of systemic viral febrile disease were present. All individuals were tested for ZIKV and Chikungunya infection using PCR, while rapid test was used to detect Dengue virus antibodies or, alternatively, the NS1 antigen. A diagnosis of acute ZIKV infection was confirmed in 78/434 (18%) individuals with systemic viral febrile illness. Positivity was mainly observed in blood, followed by saliva and urine. Coinfection with Chikungunya and/or Dengue virus was detected in 5% of the ZIKV-infected patients. The most frequent clinical findings were myalgia, arthralgia and low-grade fever. Laboratory analysis demonstrated normal levels of hematocrit, platelets and liver enzymes. In summary, in acute settings where molecular testing remains unavailable, clinicians face difficulties to confirm the diagnosis of ZIKV infection, as they rely only on clinical examinations and conventional laboratory tests.

Clinical and laboratory findings of acute Zika virus infection in patients from Salvador during the first Brazilian epidemic.

Several major epidemics of Zika fever, caused by the ZIKA virus (ZIKV), have emerged in Brazil since early 2015, eventually spreading to other countries on the South American continent. The present study describes the clinical manifestations and laboratory findings of patients with confirmed acute ZIKV infection during the first epidemic that occurred in Salvador, Brazil. All included patients were seen at the emergency room of a private tertiary hospital located in Salvador, Brazil from 2015 through 2017. Patients were considered eligible if signs of systemic viral febrile disease were present. All individuals were tested for ZIKV and Chikungunya infection using PCR, while rapid test was used to detect Dengue virus antibodies or, alternatively, the NS1 antigen. A diagnosis of acute ZIKV infection was confirmed in 78/434 (18%) individuals with systemic viral febrile illness. Positivity was mainly observed in blood, followed by saliva and urine. Coinfection with Chikungunya and/or Dengue virus was detected in 5% of the ZIKV-infected patients. The most frequent clinical findings were myalgia, arthralgia and low-grade fever. Laboratory analysis demonstrated normal levels of hematocrit, platelets and liver enzymes. In summary, in acute settings where molecular testing remains unavailable, clinicians face difficulties to confirm the diagnosis of ZIKV infection, as they rely only on clinical examinations and conventional laboratory tests.

New Challenge for Zika Virus Infection: Human Reservoirs?

Zika virus (ZIKV) is considered to cause an acute self-limited infection in adults, and microcephaly in fetus. Presence of the virus for long periods has been detected in body fluids; however, persistent viremia in serum for more than 1 year has not yet been reported. We have investigated persistence of ZIKV in serum samples of 77 subjects who were infected by the virus between 18 months and 3 years before the start of this study. The subjects included children with microcephaly and their parents. Serum samples were subjected to routine RT-qPCR assay for ZIKV, Chikungunya virus, and Dengue virus. From the 77 subjects, five showed positive for the presence of ZIKV particles by RT-qPCR, including four members of the same family. Viral isolation in Vero cells and C6/36 cells confirmed the result and showed the viral particles were active. We have detected viremia in healthy carriers up to 3 years after symptom onset. Humans acting as potential viral reservoirs have major implication for the current understanding of ZIKV infection.

Hematopoiesis: A Layered Organization Across Chordate Species.

The identification of distinct waves of progenitors during development, each corresponding to a specific time, space, and function, provided the basis for the concept of a "layered" organization in development. The concept of a layered hematopoiesis was established by classical embryology studies in birds and amphibians. Recent progress in generating reliable lineage tracing models together with transcriptional and proteomic analyses in single cells revealed that, also in mammals, the hematopoietic system evolves in successive waves of progenitors with distinct properties and fate. During embryogenesis, sequential waves of hematopoietic progenitors emerge at different anatomic sites, generating specific cell types with distinct functions and tissue homing capacities. The first progenitors originate in the yolk sac before the emergence of hematopoietic stem cells, some giving rise to progenies that persist throughout life. Hematopoietic stem cell-derived cells that protect organisms against environmental pathogens follow the same sequential strategy, with subsets of lymphoid cells being only produced during embryonic development. Growing evidence indicates that fetal immune cells contribute to the proper development of the organs they seed and later ensure life-long tissue homeostasis and immune protection. They include macrophages, mast cells, some γδ T cells, B-1 B cells, and innate lymphoid cells, which have "non-redundant" functions, and early perturbations in their development or function affect immunity in the adult. These observations challenged the view that all hematopoietic cells found in the adult result from constant and monotonous production from bone marrow-resident hematopoietic stem cells. In this review, we evaluate evidence for a layered hematopoietic system across species. We discuss mechanisms and selective pressures leading to the temporal generation of different cell types. We elaborate on the consequences of disturbing fetal immune cells on tissue homeostasis and immune development later in life.