Household Transmission of SARS-CoV-2 and Long-term Immunity in Children: A Prospective Study in Northern Spain.

BACKGROUND: The role of children in SARS-CoV-2 transmission and their immune response after infection have been profoundly discussed. Hereby, we analyze both aspects in a Spanish pediatric population. METHODS: Prospective, multicentre, longitudinal study performed from July 2020 to September 2021 in children up to 14 years old. Venous blood samples were collected every 6 months and serum was analyzed for antibodies against SARS-CoV-2 using a spike (S) and a nucleocapsid (N) protein assays. Household contacts of seropositive children were tested. Household transmission, antibody dynamics, and durability were analyzed. RESULTS: Two hundred children were recruited and 28 had SARS-CoV-2 antibodies at the end of the study, resulting in an overall seroprevalence of 16.6% (95% CI: 9.5%-19.6%). Most of children (18/28) were secondary cases. The secondary attack rate (SAR) was lower in households with pediatric index cases than in those with adult index cases ( P = 0.023). The median antibody titers in the first positive serology, for the seropositive patients, were 137 BAU/mL (IQR 83.3-427.4) for the S-assay and 132.5 COI (IQR 14.5-170.5) for the N-assay without significant differences between symptomatic and asymptomatic children. The median time between the RT-PCR and the last serology was 7.5 months (IQR 5.2-8.8), and the duration of SARS-CoV-2 antibodies after infection was proven to be at least 18 months. There were no cases of seroreversion. CONCLUSIONS: (1) Children are not the main drivers of SARS-CoV-2 household transmission. (2) They maintain SARS-CoV-2 antibodies for up to 18 months after infection and the titers are similar between symptomatic and asymptomatic children.

Change on the Circulation of Respiratory Viruses and Pediatric Healthcare Utilization during the COVID-19 Pandemic in Asturias, Northern Spain.

(1) Background: The COVID-19 pandemic and the implementation of restrictions and nonpharmaceutical interventions (NPIs) changed the trends in respiratory viral circulation and the pattern in pediatric healthcare utilization; (2) Methods: A retrospective, multicenter observational study designed to analyze the impact of the pandemic on pediatric healthcare utilization and the viral circulation pattern in children in a region in Northern Spain was carried out. Viral diagnostics data from all nasal or pharyngeal swabs collected in children in Asturias during the periods of March 2018−September 2019 and March 2020−September 2021 were analyzed, as well as the number of pediatric hospitalizations and emergency visits; (3) Results: A total of 14,640 samples were collected during the pandemic period. Of these, at least one respiratory virus was detected in 2940 (20.1%) while 5568/10,298 samples were positive in the pre-pandemic period (54.1%); p < 0.001. The detection of both enveloped and non-enveloped viruses decreased among periods (p < 0.001). After week 14, 2020, enveloped viruses were no longer detected until one year later, while non-enveloped viruses continued to be detected in children. Overall, a mean of 4946.8 (95% CI 4519.1−5374.4) pediatric emergency visits per month during the period 2018−2019 as compared to 2496.5 (95% CI 2086.4−2906.5) for 2020−2021 occurred (p < 0.001). The mean of pediatric hospitalizations also significantly decreased between periods, as follows: 346.6 (95% CI 313−380.2) in 2018−2019 vs. 161.1 (95% CI 138.4−183.8); p < 0.001; (4) Conclusions: Our study showed a remarkably reduction in pediatric hospitalizations and emergency visits and a change in the pattern of viral circulation during the COVID-19 pandemic in Asturias. The usual seasonal respiratory viruses, namely influenza or RSV were nearly absent in the pediatric population during the pandemic.

Variation in SARS-CoV-2 seroprevalence in children in the region of Asturias, Northern Spain.

BACKGROUND: Updated seroprevalence estimates are important to describe the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) landscape and to guide public health decisions. The aims are to describe longitudinal changes in seroprevalence in children in a region in Northern Spain and to analyze factors associated with SARS-CoV-2 seropositivity. METHODS: Prospective multicenter longitudinal study with subjects recruited from July to September 2020. Children (up to 14 years old) were included and followed up until September 2021. Venous blood samples were collected every six months during three testing rounds and were analyzed for SARS-CoV-2 antibodies. The data regarding epidemiological features, contact tracing, symptoms, and virological tests were collected. The evolution of SARS-CoV-2 seroprevalence during the study and the differences between children with positive and negative SARS-CoV-2 antibody tests were analyzed. RESULTS: Two hundred children were recruited (50.5% girls, median age 9.7 years). The overall seroprevalence increased from round 1 [1.5%, 95% confidence interval (CI) 0.3%-4.3%] to round 2 (9.1%, 95% CI 4.6%-12.7%) and round 3 (16.6%, 95% CI 9.5%-19.6%) (P < 0.001). Main changes occurred in children aged zero to four years (P = 0.001) who lived in urban areas (P < 0.001). None of the children who were previously positive became seronegative. Following multivariable analysis, three variables independently associated with SARS-CoV-2 seropositivity were identified: close contact with coronavirus disease 2019 (COVID-19) confirmed or suspected cases [odds ratio (OR) = 3.9, 95% CI 1.2-12.5], previous positive virological test (OR = 17.1, 95% CI 3.7-78.3) and fatigue (OR = 18.1, 95% CI 1.7-193.4). CONCLUSIONS: SARS-CoV-2 seroprevalence in children has remarkably increased during the time of our study. Fatigue was the only COVID-19-compatible symptom that was more frequent in seropositive than in seronegative children.

Trends and Pattern of Antibiotic Use in Children in Northern Spain, Interpreting Data about Antibiotic Consumption in Pediatric Outpatients.

Monitoring of antibiotic prescription and consumption behavior is crucial. The Access, Watch, and Reserve (AWaRe) classification of antibiotics has been recently introduced in order to measure and improve patterns of antibiotic use. In this study, retrospective data about systemic antibiotic consumption (expressed in defined daily dose per 1000 inhabitants per day (DID)) in pediatric outpatients in a region in northern Spain (around 100,000 children up to 14 years old) from 2005 to 2018 were analyzed and compared with antibiotic consumption in general population in Spain. The pattern of use was analyzed by the percentage of the current AWaRe categories, the Access-to-Watch index, and the amoxicillin index. Data were calculated annually and compared into two periods. Mean antibiotic consumption in pediatric outpatients was 14.0 DID (CI 95% 13.38-14.62). It remained stable throughout the study and was lower than consumption in general population in Spain, particularly from 2016. Changes in the consumption of the main active principles have led to an improvement in the three metrics of the pattern of use. It is important to have a thorough knowledge of the methodology applied in studies about antibiotic consumption. There is a lack of an optimal standardized metric for the pediatric population.

Evolución del consumo de antibióticos a nivel extrahospitalario en Asturias, España (2005-2018) / Evolution of antibiotic consumption in pediatric outpatients of Asturias, Spain (2005-2018)

Introducción: El consumo de antibióticos en España es elevado y más del 90% de las prescripciones se realizan en ámbito extrahospitalario. La exposición a antibióticos en la edad infantil es alta. El objetivo de este estudio es describir la evolución del consumo extrahospitalario de antibióticos en la población pediátrica del Principado de Asturias entre 2005 y 2018.Material y métodos: Estudio descriptivo y retrospectivo del consumo de antibacterianos de uso sistémico (grupo J01 de la clasificación ATC, Anatomical Therapeutic Chemical Classification) en ámbito extrahospitalario en la población pediátrica (0-13 años) del Principado de Asturias entre 2005 y 2018. Se compara el consumo, medido en número de dosis diarias definidas (DDD) por 1.000 habitantes y día (DHD), en 3 periodos de tiempo.Resultados: El consumo medio de antibacterianos en la población pediátrica asturiana (2005-2018) fue de 14 DHD (IC95% 13,4-14,6), con un aumento hasta 2009 (15,2 DHD) y descenso a partir de 2015 (11,9 DHD en 2018). A lo largo del estudio se detectó: 1) un aumento del consumo de amoxicilina (p=0,027), que supera al de amoxicilina-clavulánico desde el año 2011; 2) un consumo estable de macrólidos, con un aumento de azitromicina (p<0,001) y un descenso de claritromicina (p=0,001); 3) un descenso del consumo de cefalosporinas (p<0,001); 4) un aumento del consumo de quinolonas (p=0,002).Conclusiones: El consumo de antibióticos a nivel extrahospitalario en la población pediátrica del Principado de Asturias entre los años 2005 y 2018 ha experimentado un descenso mantenido en los últimos años y una mejora evolutiva del patrón de uso. (AU)

Introduction: Data about consumption of antibiotics in Spain are worrisome. They are mainly prescribed in the community sector and there is a high exposure to antibiotics in the pediatric population. The aim of this study is to describe the evolution of antibiotic consumption in the pediatric population of Asturias during 2005-2018 period.Material and methods: Retrospective and descriptive study using data about consumption of antibacterial agents for systemic use (J01 group of the Anatomical Therapeutic Chemical Classification) in pediatric outpatients in Principado de Asturias between 2005 and 2018. Data, expressed as defined daily dose (DDD) per 1000 inhabitants per day (DID), in three periods were compared.Results: Mean antibiotic consumption in pediatric outpatients in Principado de Asturias (2005-2018) was 14 DID (CI95% 13.4-14.6). Consumption increased until 2009 (15.2 DID) and decreased from 2015 onwards (11.9 DID in 2018). Remarkable data along the study were: 1) increase in amoxicillin consumption (p=0.027), that have exceeded that of amoxicillin-clavulanate since 2011; 2) steady consumption of macrolides, with an increase in azithromycin (p<0.001) and a decrease in clarithromycin (p=0.001); 3) reduction of cephalosporins consumption (p<0.001); 4) increase in quinolones consumption (p=0.002).Conclusions: Global antibiotic consumption in pediatric outpatients in Principado de Asturias between 2005 and 2018 has experienced a constant decrease lately and an improvement in patterns of antibacterial use. (AU)

Evolution of antibiotic consumption in pediatric outpatients of Asturias, Spain (2005-2018).

INTRODUCTION: Data about consumption of antibiotics in Spain are worrisome. They are mainly prescribed in the community sector and there is a high exposure to antibiotics in the pediatric population. The aim of this study is to describe the evolution of antibiotic consumption in the pediatric population of Asturias during 2005-2018 period. METHODS: Retrospective and descriptive study using data about consumption of antibacterial agents for systemic use (J01 group of the Anatomical Therapeutic Chemical Classification) in pediatric outpatients in Asturias between 2005 and 2018. Data, expressed as defined daily dose (DDD) per 1000 inhabitants per day (DID), in three periods were compared. RESULTS: Mean antibiotic consumption in pediatric outpatients in Asturias (2005-2018) was 14 DID (CI95% 13.4-14.6). Consumption increased until 2009 (15.2 DID) and decreased from 2015 onwards (11.9 DID in 2018). Remarkable data along the study were: 1) increase in amoxicillin consumption (p = 0.027), that have exceeded that of amoxicillin-clavulanate since 2011; 2) steady consumption of macrolides, with an increase in azithromycin (p < 0.001) and a decrease in clarithromycin (p = 0.001); 3) reduction of cephalosporins consumption (p < 0.001); 4) increase in quinolones consumption (p = 0.002). CONCLUSIONS: Global antibiotic consumption in pediatric outpatients in Asturias between 2005 and 2018 has experienced a constant decrease lately and an improvement in patterns of antibacterial use.

[Evolution of antibiotic consumption in pediatric outpatients of Asturias, Spain (2005-2018)]. / Evolución del consumo de antibióticos a nivel extrahospitalario en Asturias, España (2005-2018).

INTRODUCTION: Data about consumption of antibiotics in Spain are worrisome. They are mainly prescribed in the community sector and there is a high exposure to antibiotics in the pediatric population. The aim of this study is to describe the evolution of antibiotic consumption in the pediatric population of Asturias during 2005-2018 period. MATERIAL AND METHODS: Retrospective and descriptive study using data about consumption of antibacterial agents for systemic use (J01 group of the Anatomical Therapeutic Chemical Classification) in pediatric outpatients in Principado de Asturias between 2005 and 2018. Data, expressed as defined daily dose (DDD) per 1000 inhabitants per day (DID), in three periods were compared. RESULTS: Mean antibiotic consumption in pediatric outpatients in Principado de Asturias (2005-2018) was 14 DID (CI95% 13.4-14.6). Consumption increased until 2009 (15.2 DID) and decreased from 2015 onwards (11.9 DID in 2018). Remarkable data along the study were: 1) increase in amoxicillin consumption (p=0.027), that have exceeded that of amoxicillin-clavulanate since 2011; 2) steady consumption of macrolides, with an increase in azithromycin (p<0.001) and a decrease in clarithromycin (p=0.001); 3) reduction of cephalosporins consumption (p<0.001); 4) increase in quinolones consumption (p=0.002). CONCLUSIONS: Global antibiotic consumption in pediatric outpatients in Principado de Asturias between 2005 and 2018 has experienced a constant decrease lately and an improvement in patterns of antibacterial use.

Drosophila hedgehog can act as a morphogen in the absence of regulated Ci processing.

Extracellular Hedgehog (Hh) proteins induce transcriptional changes in target cells by inhibiting the proteolytic processing of full-length Drosophila Ci or mammalian Gli proteins to nuclear transcriptional repressors and by activating the full-length Ci or Gli proteins. We used Ci variants expressed at physiological levels to investigate the contributions of these mechanisms to dose-dependent Hh signaling in Drosophila wing imaginal discs. Ci variants that cannot be processed supported a normal pattern of graded target gene activation and the development of adults with normal wing morphology, when supplemented by constitutive Ci repressor, showing that Hh can signal normally in the absence of regulated processing. The processing-resistant Ci variants were also significantly activated in the absence of Hh by elimination of Cos2, likely acting through binding the CORD domain of Ci, or PKA, revealing separate inhibitory roles of these two components in addition to their well-established roles in promoting Ci processing.

Morphogens play a crucial role in determining how cells are organized in developing organisms. These chemical signals act over a wide area, and the amount of signal each cell receives typically initiates a sequence of events that spatially pattern the multiple cells of an organ or tissue. One of the most well-studied groups of morphogens are the hedgehog proteins, which are involved in the development of many animals, ranging from flies to humans. In fruit flies, hedgehog proteins kickstart a cascade of molecular changes that switch on a set of 'target' genes. They do this by ultimately altering the activity of a protein called cubitus interruptus, which comes in two lengths: a long version called Ci-155 and a short version called Ci-75. When hedgehog is absent, Ci-155 is kept in an inactive state in the cytoplasm, where it is slowly converted into its shorter form, Ci-75: this repressor protein is then able to access the nucleus, where it switches 'off' the target genes. However, when a hedgehog signal is present, the processing of Ci into its shorter form is inhibited. Instead, Ci-155 becomes activated by a separate mechanism that allows the long form protein to enter the nucleus and switch 'on' the target genes. But it was unclear whether hedgehog requires both of these mechanisms in order to act as a morphogen and regulate the activity of developmental genes. To answer this question, Little et al. mutated the gene for Ci in the embryo of fruit flies, so that the Ci-155 protein could no longer be processed into Ci-75. Examining the developing wings of these flies revealed that the genes targeted by hedgehog are still activated in the correct pattern. In some parts of the wing, Ci-75 is required to switch off specific sets of genes. But when Little et al. blocked these genes, by adding a gene that constantly produces the Ci repressor in the presence or absence of hedgehog, the adult flies still developed normally structured wings. This suggests that hedgehog does not need to regulate the processing of Ci-155 into Ci-75 in order to perform its developmental role. Previous work showed that when one of the major mechanisms used by hedgehog to activate Ci-155 is blocked, fruit flies are still able to develop normal wings. Taken together with the findings of Little et al., this suggests that the two mechanisms induced by hedgehog can compensate for each other, and independently regulate the development of the fruit fly wing. These mechanisms, which are also found in humans, have been linked to birth defects and several common types of cancer, and understanding how they work could help the development of new treatments.

The Exon Junction Complex and Srp54 Contribute to Hedgehog Signaling via ci RNA Splicing in Drosophila melanogaster.

Hedgehog (Hh) regulates the Cubitus interruptus (Ci) transcription factor in Drosophila melanogaster by activating full-length Ci-155 and blocking processing to the Ci-75 repressor. However, the interplay between the regulation of Ci-155 levels and activity, as well as processing-independent mechanisms that affect Ci-155 levels, have not been explored extensively. Here, we identified Mago Nashi (Mago) and Y14 core Exon Junction Complex (EJC) proteins, as well as the Srp54 splicing factor, as modifiers of Hh pathway activity under sensitized conditions. Mago inhibition reduced Hh pathway activity by altering the splicing pattern of ci to reduce Ci-155 levels. Srp54 inhibition also affected pathway activity by reducing ci RNA levels but additionally altered Ci-155 levels and activity independently of ci splicing. Further tests using ci transgenes and ci mutations confirmed evidence from studying the effects of Mago and Srp54 that relatively small changes in the level of Ci-155 primary translation product alter Hh pathway activity under a variety of sensitized conditions. We additionally used ci transgenes lacking intron sequences or the presumed translation initiation codon for an alternatively spliced ci RNA to provide further evidence that Mago acts principally by modulating the levels of the major ci RNA encoding Ci-155, and to show that ci introns are necessary to support the production of sufficient Ci-155 for robust Hh signaling and may also be important mediators of regulatory inputs.

Cambios evolutivos en las tasas y fenotipos de resistencia de Streptococcus pyogenes en una población pediátrica de Asturias, España (2005-2015) / Resistance rates and phenotypic characterization of Streptococcus pyogenes in a paediatric population in Northern Spain (2005-2015)

Introducción. Streptococcus pyogenes es uno de los principales microorganismos causantes de infecciones bacterianas en la edad pediátrica. El objetivo es analizar la evolución de las tasas y fenotipos de resistencia de S. pyogenes en una población pediátrica en el Norte de España en los últimos 11 años. Material y métodos. Estudio descriptivo retrospectivo de los aislamientos de S. pyogenes en muestras de pacientes pediátricos recogidas entre 2005 y 2015 en el Área Sanitaria V del Principado de Asturias (España). Se compararon las tasas de resistencia bacteriana entre los periodos 2005-2009 y 2010-2015 y se analizó la evolución de los fenotipos de los aislamientos resistentes. Resultados. Se registraron 1.794 aislamientos (70% en el periodo 2005-2009). El 87,5% procedían de muestras de exudado faríngeo y el 0,2% de hemocultivos. Se observó una disminución de las tasas de resistencia a tetraciclina (8,8% a 4,3%, p=0,02), eritromicina (22% a 9,3%, p<0,01) y clindamicina (6% a 1,7%, p<0,01) entre los dos periodos de tiempo. La detección de S. pyogenes resistentes a eritromicina con fenotipo MLSB fue disminuyendo de manera progresiva a lo largo del periodo de estudio. Conclusiones. Se ha observado una importante disminución de las tasas de resistencia a eritromicina y clindamicina a lo largo del periodo de estudio y un cambio en la distribución de los fenotipos de los aislamientos resistentes (AU)

Background. Streptococcus pyogenes is a significant cause of bacterial infections in children. The aim of the study is to analyse resistance rates and phenotypes of S. pyogenes isolates in a paediatric population in Northern Spain over the last 11 years. Methods. Descriptive retrospective study of S. pyogenes isolates from paediatric patients between 2005 and 2015 in a region of Asturias (Spain). Resistance rates and changes in erythromycin resistance phenotypes in two time periods (2005-2009 and 2010-2015) were studied. Results. A total of 1,794 S. pyogenes isolates were registered (70% from 2005 to 2009). 87.5% were obtained from pharyngeal swabs and 0.2% from blood cultures. Resistance rates to tetracycline (8.8% to 4.3%, p=0.02), erythromycin (22% to 9.3%, p<0.01) and clindamycin (6% to 1.7%, p<0.01) decreased between the two study periods. A reduction in erythromycin-resistant isolates with the MLSB phenotype was observed. Conclusions. A decrease in S. pyogenes resistance rates to erythromycin and clindamycin and a change in the erythromycin resistance phenotype were observed along the study period (AU)

V-myc immortalizes human neural stem cells in the absence of pluripotency-associated traits.

A better understanding of the molecular mechanisms governing stem cell self-renewal will foster the use of different types of stem cells in disease modeling and cell therapy strategies. Immortalization, understood as the capacity for indefinite expansion, is needed for the generation of any cell line. In the case of v-myc immortalized multipotent human Neural Stem Cells (hNSCs), we hypothesized that v-myc immortalization could induce a more de-differentiated state in v-myc hNSC lines. To test this, we investigated the expression of surface, biochemical and genetic markers of stemness and pluripotency in v-myc immortalized and control hNSCs (primary precursors, that is, neurospheres) and compared these two cell types to human Embryonic Stem Cells (hESCs) and fibroblasts. Using a Hierarchical Clustering method and a Principal Component Analysis (PCA), the v-myc hNSCs associated with their counterparts hNSCs (in the absence of v-myc) and displayed a differential expression pattern when compared to hESCs. Moreover, the expression analysis of pluripotency markers suggested no evidence supporting a reprogramming-like process despite the increment in telomerase expression. In conclusion, v-myc expression in hNSC lines ensures self-renewal through the activation of some genes involved in the maintenance of stem cell properties in multipotent cells but does not alter the expression of key pluripotency-associated genes.

Intermediate progenitors are increased by lengthening of the cell cycle through calcium signaling and p53 expression in human neural progenitors.

During development, neurons can be generated directly from a multipotent progenitor or indirectly through an intermediate progenitor (IP). This last mode of division amplifies the progeny of neurons. The mechanisms governing the generation and behavior of IPs are not well understood. In this work, we demonstrate that the lengthening of the cell cycle enhances the generation of neurons in a human neural progenitor cell system in vitro and also the generation and expansion of IPs. These IPs are insulinoma-associated 1 (Insm1)(+)/BTG family member 2 (Btg2)(-), which suggests an increase in a self-amplifying IP population. Later the cultures express neurogenin 2 (Ngn2) and become neurogenic. The signaling responsible for this cell cycle modulation is investigated. It is found that the release of calcium from the endoplasmic reticulum to the cytosol in response to B cell lymphoma-extra large overexpression or ATP addition lengths the cell cycle and increases the number of IPs and, in turn, the final neuron outcome. Moreover, data suggest that the p53-p21 pathway is responsible for the changes in cell cycle. In agreement with this, increased p53 levels are necessary for a calcium-induced increase in neurons. Our findings contribute to understand how calcium signaling can modulate cell cycle length during neurogenesis.

Modulation of the generation of dopaminergic neurons from human neural stem cells by Bcl-X(L): mechanisms of action.

Understanding the developmental mechanisms governing dopaminergic neuron generation and maintenance is crucial for the development of neuronal replacement therapeutic procedures, like in Parkinson's disease (PD), but also for research aimed at drug screening and pharmacology. In the present chapter, we review the present situation using stem cells of different origins (pluripotent and multipotent) and summarize current manipulations of stem cells for the enhancement of dopaminergic neuron generation, focusing on the actions of Bcl-X(L). Bcl-X(L) not only enhances dopaminergic neuron survival but also augments the expression of key developmental and maintenance genes, and, through the lengthening of the cell cycle early during differentiation, regulates cell fate decisions, producing a net enhancement of neurogenesis. The relevance of these findings is discussed in the context of basic neurogenesis and also for the development of efficient cell therapy in PD.

Bimodal viral vectors and in vivo imaging reveal the fate of human neural stem cells in experimental glioma model.

Transplantation of genetically engineered cells into the CNS offers immense potential for the treatment of several neurological disorders. Monitoring expression levels of transgenes and following changes in cell function and distribution over time is critical in assessing therapeutic efficacy of such cells in vivo. We have engineered lentiviral vectors bearing fusions between different combinations of fluorescent and bioluminescent marker proteins and used bioluminescence imaging and intravital-scanning microscopy in real time to study the fate of human neural stem cells (hNSCs) at a cellular resolution in glioma-bearing brains in vivo. Using Renilla luciferase (Rluc)-DsRed2 or GFP-Rluc-expressing malignant human glioma model, transduced hNSCs were shown to migrate extensively toward gliomas, with hNSCs populating gliomas at 10 d after transplantation. Furthermore, transduced hNSCs survived longer in mice with gliomas than in normal brain, but did not modulate glioma progression in vivo. These studies demonstrate the utility of bimodal viral vectors and real-time imaging in evaluating fate of NSCs in diseased models and thus provide a platform for accelerating cell-based therapies for CNS disorders.

The generation of dopaminergic neurons by human neural stem cells is enhanced by Bcl-XL, both in vitro and in vivo.

Progress in stem cell biology research is enhancing our ability to generate specific neuron types for basic and applied studies and to design new treatments for neurodegenerative diseases. In the case of Parkinson's disease (PD), alternative human dopaminergic (DAergic) neurons other than primary fetal tissue do not yet exist. One possible source could be human neural stem cells (hNSCs), although the yield in DAergic neurons and their survival are very limited. [see figure]. In this study, we found that Bcl-X(L) enhances (one-to-two orders of magnitude) the capacity for spontaneous dopaminergic differentiation of hNSCs, which then exceeds that of cultured human ventral mesencephalic tissue. Bcl-X(L) also enhanced total neuron generation by hNSCs, but to a lower extent. Neuronal phenotypes other than DA were not affected by Bcl-X(L), indicating an exquisitely specific effect on DAergic neurons. In vivo, grafts of Bcl-X(L)-overexpressing hNSCs do generate surviving human TH+ neurons in the adult rat 6-OH-dopamine lesioned striatum, something never seen when naive hNSCs were transplanted. Most of the data obtained here in terms of the effects of Bcl-X(L) are consistent with an enhanced survival type of mechanism and not supportive of induction, specification, or proliferation of DAergic precursors. From this in vitro and in vivo evidence, we conclude that enhancing Bcl-X(L) expression is important to obtain human DAergic neurons from hNSCs. These findings may facilitate the development of drug-screening and cell-replacement activities to discover new therapeutic strategies for PD.