Ultra-bright, efficient and stable perovskite light-emitting diodes.

Metal halide perovskites are attracting a lot of attention as next-generation light-emitting materials owing to their excellent emission properties, with narrow band emission1-4. However, perovskite light-emitting diodes (PeLEDs), irrespective of their material type (polycrystals or nanocrystals), have not realized high luminance, high efficiency and long lifetime simultaneously, as they are influenced by intrinsic limitations related to the trade-off of properties between charge transport and confinement in each type of perovskite material5-8. Here, we report an ultra-bright, efficient and stable PeLED made of core/shell perovskite nanocrystals with a size of approximately 10 nm, obtained using a simple in situ reaction of benzylphosphonic acid (BPA) additive with three-dimensional (3D) polycrystalline perovskite films, without separate synthesis processes. During the reaction, large 3D crystals are split into nanocrystals and the BPA surrounds the nanocrystals, achieving strong carrier confinement. The BPA shell passivates the undercoordinated lead atoms by forming covalent bonds, and thereby greatly reduces the trap density while maintaining good charge-transport properties for the 3D perovskites. We demonstrate simultaneously efficient, bright and stable PeLEDs that have a maximum brightness of approximately 470,000 cd m-2, maximum external quantum efficiency of 28.9% (average = 25.2 ± 1.6% over 40 devices), maximum current efficiency of 151 cd A-1 and half-lifetime of 520 h at 1,000 cd m-2 (estimated half-lifetime >30,000 h at 100 cd m-2). Our work sheds light on the possibility that PeLEDs can be commercialized in the future display industry.

E/e' Ratio Predicts the Atrial Pacing-Induced Left Atrial Pressure Response in Patients with Preserved Ejection Fraction.

Background and Objectives: Left atrial hypertension is one of the pathophysiologies of heart failure with preserved ejection fraction. We hypothesized that left atrial pressure response (LAPR) to incremental pacing is higher in patients with atrial fibrillation (AF) and can predict left ventricular diastolic dysfunction. Materials and Methods: Patients requiring left atrial access as a part of a therapeutic procedure for AF (n = 204, AF group) or supraventricular tachycardia (n = 34, control group) were analyzed (male n = 183, 54 ± 12 years old). LAPR was measured during incremental pacing. Results: Baseline left atrial pressure and LAPR at all pacing rates were not different between the AF and control groups. They were higher in patients with a high E/e' (≥ 8) than in those with a low E/e' (<8). LAPR at a pacing interval of 400 ms and E/e' were positively correlated (r = 0.373, p < 0.001). Body mass index and a high E/e' were independent predictors of pacing-induced left atrial hypertension. Conclusions: LAPR to incremental pacing was constant regardless of AF. The non-invasive echocardiographic marker E/e' reflected pacing-induced left atrial hypertension.

Association of atrial fibrillation with infectivity and severe complications of COVID-19: A nationwide cohort study.

Infection is associated with the occurrence, recurrence, and progression of atrial fibrillation (AF), and is also closely related to poor prognosis. However, studies of the relationship between infectivity and severe complications of coronavirus infectious disease-19  (COVID-19) with a history of AF are limited. To estimate infectivity and severity of complications in COVID-19 patients with a history of AF, this study was done. From the Korean nationwide COVID-19 dataset, 212 678 participants with at least one severe acute respiratory syndrome coronavirus 2 (COVID-19) test were included between January 1 and June 4, 2020. AF was defined according to at least two outpatient hospital visits or one admission with an ICD-10 code of "I48" before the COVID-19 test. To investigate the association of AF with infectivity and severe complications of COVID-19, 1:4 ratio propensity score matching (PSM) was performed. Severe complications of COVID-19 were defined as a composite outcome of mechanical ventilation, intensive care unit admission, and death within 2 months after COVID-19 diagnosis. Among 212 678 participants who underwent the COVID-19 test, there were 7713 COVID-19 positive patients. After PSM, COVID-19 PCR positivity did not show a significant difference according to the presence of AF (odds ratio [OR]: 0.79, 95% confidence interval [CI]: [0.60-1.04]). Of 7713 COVID-19 patients, 62 (0.8%) had a history of AF and severe complications occurred in 444 (5.7%) patients. After PSM, AF was associated with the development of severe complications (OR: 2.04, 95% CI: [1.10-3.79]) and mortality (OR: 2.09, 95% CI: [1.01-4.31]) of COVID-19. We found that AF was associated with an increased risk of severe complications in COVID-19 infected patients.

Associations of heart failure with susceptibility and severe complications of COVID-19: A nationwide cohort study.

Infection is associated with occurrence and worsening of heart failure (HF). However, studies on the association of susceptibility and severe complications of coronavirus disease 2019 (COVID-19) with HF history are limited. From the Korean nationwide COVID-19 data set, 212,678 participants with at least one severe acute respiratory syndrome coronavirus 2 real-time reverse transcription polymerase chain reaction (RT-PCR) test were included between January 1 and June 4, 2020. To investigate the association of HF with susceptibility and severe complications of COVID-19, 1:4 ratio propensity score matching (PSM) and logistic regression analysis were performed. The primary outcome was a composite outcome of mechanical ventilation, intensive care unit (ICU) admission, and death. After PSM, COVID-19 PCR positivity did not show a significant difference according to HF history in multivariable analysis (odds ratio [OR]: 0.91, 95% confidence interval (CI) (0.79-1.04), p = 0.146). Of 7630 individuals with confirmed COVID-19 infection, 310 (4.1%) had HF history. The overall primary outcome occurred in 426 (5.6%) individuals, including 159 (2.1%) cases of mechanical ventilation, 254 (3.3%) cases of ICU admission, and 215 (2.8%) cases of death. In multivariate logistic analysis, presence of HF history was associated independently with primary outcome (OR: 1.99, 95% CI: 1.42-2.79, p < 0.001), particularly mortality (OR: 2.02, 95% CI: 1.36-3.00, p < 0.001). Our study demonstrated that HF history is associated poor prognosis, particularly mortality, in COVID-19. Patients with HF can have severe complication if infected with COVID-19; therefore, careful management are necessary.

Analysis of national surveillance of respiratory pathogens for community-acquired pneumonia in children and adolescents.

BACKGROUND: Respiratory infections among children, particularly community-acquired pneumonia (CAP), is a major disease with a high frequency among outpatient and inpatient visits. The causes of CAP vary depending on individual susceptibility, the epidemiological characteristics of the community, and the season. We performed this study to establish a nationwide surveillance network system and identify the causative agents for CAP and antibiotic resistance in Korean children with CAP. METHODS: The monitoring network was composed of 28 secondary and tertiary medical institutions. Upper and lower respiratory samples were assayed using a culture or polymerase chain reaction (PCR) from August 2018 to May 2020. RESULTS: A total of 1023 cases were registered in patients with CAP, and PCR of atypical pneumonia pathogens revealed 422 cases of M. pneumoniae (41.3%). Respiratory viruses showed a positivity rate of 65.7% by multiplex PCR test, and human rhinovirus was the most common virus, with 312 cases (30.5%). Two hundred sixty four cases (25.8%) were isolated by culture, including 131 cases of S. aureus (12.8%), 92 cases of S. pneumoniae (9%), and 20 cases of H. influenzae (2%). The cultured, isolated bacteria may be colonized pathogen. The proportion of co-detection was 49.2%. The rate of antibiotic resistance showed similar results as previous reports. CONCLUSIONS: This study will identify the pathogens that cause respiratory infections and analyze the current status of antibiotic resistance to provide scientific evidence for management policies of domestic respiratory infections. Additionally, in preparation for new epidemics, including COVID-19, monitoring respiratory infections in children and adolescents has become more important, and research on this topic should be continuously conducted in the future.

The Impact of Personal Thoracic Impedance on Electrical Cardioversion in Patients with Atrial Arrhythmias.

Background and Objectives: Direct current cardioversion (DCCV) is a safe and useful treatment for atrial tachyarrhythmias. In the past, the energy delivered in DCCV was decided upon empirically, based only on the type of tachyarrhythmia. This conventional method does not consider individual factors and may lead to unnecessary electrical damage. Materials and Methods: We performed DCCV in patients with atrial tachyarrhythmias. The impedance and electrical current at the moment of shock were measured. The human thoracic impedance between both defibrillator patches and the electric current that was used were measured. Results: A total of 683 DCCVs were performed on 466 atrial tachyarrhythmia patients. The average impedance was 64 ± 11 Ω and the average successful current was 23 ± 6 mA. The magnitude of the electrical current that was successful depended upon the human impedance (linear regression, B = -0.266, p < 0.001) and the left atrial diameter (B = 0.092, p < 0.001). Impedance was directly proportional to body mass index (BMI) (B = 1.598, p < 0.001) and was higher in females than in males (77 ± 15 Ω vs. 63 ± 11 Ω, p < 0.001). Notably, the high-impedance (>70 Ω) group had a higher BMI (27 ± 4 kg/m2 vs. 25 ± 3 kg/m2, p < 0.001) and a higher proportion of females (37% vs. 9%, p < 0.001) than the low-impedance group (<70 Ω). However, thoracic impedance was not an independent predictor for successful DCCV. Conclusions: Human thoracic impedance was one of the factors that impacted the level of electrical current required for successful DCCV in patients with atrial arrhythmias. In the future, it will be helpful to consider individual predictors, such as BMI and gender, to minimize electrical damage during DCCV.

Spoligotype Variation of Mycobacterium tuberculosis Strains Prevailing in Korea.

Tuberculosis (TB) is an ongoing global health problem, including in South Korea. To manage TB efficiently, it is necessary to understand the epidemiology, transmission route, and characteristics of prevailing Mycobacterium tuberculosis strains. In this study, we investigated microevolutions over time in the spoligotype patterns of M. tuberculosis isolated from TB patients in Korea. We collected 1,055 clinical M. tuberculosis isolates from 16 provinces in Korea from 1994 to 2006 and analyzed them by spoligotyping. We observed 26 subfamilies, including two large predominant families: a Beijing family (72.7%) and the T family (19.1%). Specifically, the abundance of spoligotype SIT269 from the Beijing-like subfamily significantly increased in the 2000s relative to the 1990s in Korea. This study provides an overview of the M. tuberculosis genotype trends over time in Korea. These data also indicate that we should consider the influence of the newly growing SIT269 subtype identified in the Beijing family.

Comparison between linear and focal ablation of complex fractionated atrial electrograms in patients with non-paroxysmal atrial fibrillation: a prospective randomized trial.

AIMS: Findings regarding efficacy of substrate modification for non-paroxysmal atrial fibrillation (AF) are inconsistent. We prospectively compared clinical outcomes of complex fractionated atrial electrogram (CFAE)-guided focal ablation (CFA) and CFAE-guided linear ablation (CLA) in patients with non-paroxysmal AF. METHODS AND RESULTS: We randomized 150 patients with non-paroxysmal AF into CFA and CLA groups in a 1:1 ratio. Complex fractionated atrial electrogram distribution was evaluated using an automated algorithm of a three-dimensional mapping system. After pulmonary vein isolation (PVI), CFAE-guided ablation was performed in the left atrium and then in the right atrium (RA). When compared with conventional CFA, CLA was performed based on conventional lines, with additional lines. Atrial fibrillation was not induced after PVI alone or with cavotricuspid isthmus ablation in 20.7% of patients. To achieve the endpoint, additional CFAE-guided RA ablation was required in 42.7% and 36.0% of patients undergoing CFA and CLA, respectively (P = 0.403). Atrial fibrillation was terminated during CFAE-guided ablation in 72.9% and 75.0% of patients undergoing CFA and CLA, respectively (P = 0.792). Termination of atrial tachycardia (AT) or non-inducibility of AF/AT was achieved in 61.3% and 68.0% of patients undergoing CFA and CLA, respectively (P = 0.393). The CLA group showed decreased 1-year freedom from AF/AT recurrence (60.0%, CFA vs. 47.3%, CLA; log rank P = 0.085), but no significant difference throughout the follow-up (22.2 ± 21.0 months) (67.1%, CFA vs. 68.9%, CLA; log rank P = 0.298). CONCLUSION: Long-term efficacy of CFAE-guided ablation was unaffected by the ablation technique in patients with non-paroxysmal AF.

Enzyme-Free Nucleic Acid Amplification Assay Using a Cellphone-Based Well Plate Fluorescence Reader.

Nucleic acids, DNA and RNA, provide important fingerprint information for various pathogens and have significant diagnostic value; however, improved approaches are urgently needed to enable rapid detection of nucleic acids in simple point-of-care formats with high sensitivity and specificity. Here, we present a system that utilizes a series of toehold-triggered hybridization/displacement reactions that are designed to convert a given amount of RNA molecules (i.e., the analyte) into an amplified amount of signaling molecules without any washing steps or thermocycling. Fluorescent probes for signal generation were designed to consume products of the catalytic reaction in order to push the equilibrium and enhance the assay fold amplification for improved sensitivity and reaction speed. The system of toehold-assisted reactions is also modeled to better understand its performance and capabilities, and we empirically demonstrate the success of this approach with two analytes of diagnostic importance, i.e., influenza viral RNA and a micro RNA (miR-31). We also show that the amplified signal permits using a compact and cost-effective smartphone-based fluorescence reader, an important requirement toward a nucleic-acid-based point-of-care diagnostic system.

Characteristics of atrial fibrillation patients suffering atrioesophageal fistula after radiofrequency catheter ablation.

INTRODUCTION: Radiofrequency catheter ablation (RFCA) in atrial fibrillation (AF) patients can cause various complications and atrioesophageal (AE) fistula is one of the most catastrophic complications of RFCA. METHODS AND RESULTS: RFCA registries from 3 cardiovascular centers in the Republic of Korea consisted of 5721 patients undergoing 6724 procedures. Before undergoing RFCA, patients underwent either computed tomography or magnetic resonance imaging. We evaluated clinical, anatomical, and procedural characteristics of patients who developed AE fistula after RFCA. A total of 10 patients developed AE fistula after RFCA (0.15% per procedure). All AE fistulas occurred during first-time RFCA. Eight patients died and mortality rate was 80.0%. No patients had any gastrointestinal symptom at the time of discharge and mean duration time from RFCA to symptom onset was 23.4 days. Six patients (60.0%) had paroxysmal AF. Substrate modification in addition to pulmonary vein isolation was performed in 4 patients (40.0%). Patients with old age, low body weight, and high CHA2 DS2 -VASc score were at increased risk of AE fistula. Baseline imaging evaluation revealed that esophagus had closest contact with LA posterior wall near left inferior pulmonary vein rather than left superior pulmonary vein and all documented AE fistulas were located near left inferior pulmonary vein. CONCLUSION: Posterior wall of LA near left inferior pulmonary vein was the most vulnerable location for AE fistula. Pulmonary vein isolation was the main lesion set associated with AE fistula and old age, low body weight, and high CHA2 DS2 -VASc score were significant risk factors for AE fistula.

Long-term clinical outcomes of catheter ablation in patients with atrial fibrillation predisposing to tachycardia-bradycardia syndrome: a long pause predicts implantation of a permanent pacemaker.

BACKGROUND: There is a controversy as to whether catheter ablation should be the first-line therapy for tachycardia-bradycardia syndrome (TBS) in patients with atrial fibrillation (AF). METHODS: We aimed to investigate long-term clinical outcomes of catheter ablation in patients with TBS and AF. Among 145 consecutive patients who underwent catheter ablation of AF with TBS, 121 patients were studied. RESULTS: Among 121 patients, 11 (9.1%) received implantation of a permanent pacemaker during a mean 21 months after ablation. Length of pause on termination of AF was significantly greater in patients who received pacemaker implantation after ablation than those who underwent ablation only (7.9 ± 3.5 vs. 5.1 ± 2.1 s, p < 0.001). Using a multivariate model, a long pause of 6.3 s or longer after termination of AF was associated with the requirement to implant a permanent pacemaker after ablation (HR 1.332, 95% CI 1.115-1.591, p = 0.002). CONCLUSION: This study suggests that, in patients with AF predisposing to TBS, long pause on termination of AF predicts the need to implant a permanent pacemaker after catheter ablation.

Long-Term Outcome of Catheter Ablation for Atrial Fibrillation in Patients With Apical Hypertrophic Cardiomyopathy.

INTRODUCTION: Atrial fibrillation (AF) is a common manifestation in cases of hypertrophic cardiomyopathy (HCM). Catheter ablation (CA) for AF in patients with asymmetric septal HCM (SeHCM) is selectively effective and often needs a repeat procedure. Apical HCM (ApHCM) has a better prognosis than SeHCM. However, the outcome of CA for AF in patients with ApHCM is unclear. METHODS AND RESULTS: Eighteen patients with ApHCM (ApHCM group) and 13 SeHCM patients (SeHCM group) underwent CA for AF. Ninety sex-, age-, and AF type-matched non-HCM patients who underwent CA for AF were selected as controls (5 controls for each ApHCM patient). During a median follow-up of 44.7 ± 30.8 months, 50% of the patients remained free from AF/atrial tachycardia (AT) in the ApHCM group. The ApHCM patients displayed enlarged left atrial (LA) diameter (47.1 ± 6.0 mm vs. 42.4 ± 5.5 mm, P = 0.006) and increased E/Ea ratio (13.5 ± 4.4 vs. 9.1 ± 3.1, P < 0.001) as compared to the control group. In contrast, the mean LA diameter and E/Ea ratio of the ApHCM group were not different than those of the SeHCM group. The overall freedom from AF/AT in the ApHCM group was significantly worse than in the control group (log rank P = 0.028), but there was no difference between the ApHCM and SeHCM groups (P = 0.831). High LA diameter index ≥25 mm/m(2) (HR 12.8, 95% CI [1.2-142.1]; P = 0.037) was an independent predictor of AF/AT recurrence among patients with ApHCM. CONCLUSION: Long-term outcome of CA for AF was worse in patients with ApHCM, as compared to controls, but was similar to patients with SeHCM.

Atrial fibrillation cycle length as a predictor for the extent of substrate ablation.

AIMS: Atrial fibrillation (AF) cycle length (CL) has been demonstrated to be one of the predictors for termination during ablation for AF. We evaluated the AF CL gradient between right atrium (RA) and left atrium (LA) and their mean AF CL in predicting the extent of substrate ablation. METHODS AND RESULTS: One-hundred and thirty-six patients undergoing first ablation for persistent AF were studied. Stepwise ablation, sequentially in the following order: pulmonary veins (PV), LA, and RA, was performed to achieve AF termination. Stepwise ablation terminated AF in 110 patients (81%). In the AF termination group, AF was terminated by PV isolation (PVI) (Group P), PVI plus LA ablation (Group L), and PVI plus LA plus RA ablation (Group R) in 14 patients (13%), 49 patients (44%), and 47 patients (43%), respectively. Group R had much shorter mean AF CL than Group L (156 ± 18 vs. 174 ± 24 ms, P < 0.001) and mean AF CL in Group L was much shorter than Group P (174 ± 24 vs. 209 ± 36 ms, P = 0.004). The RA to LA AF CL gradient was not significantly different between left-side ablation (Group P + Group L) and additional RA ablation (Group R) (P = 0.177). Mean AF CL >180.50 ms predicted AF termination by PVI (Group P) with 79% sensitivity and 84% specificity while mean AF CL >165.25 ms predicted AF termination by left-side ablation (Group P + Group L) with 67% sensitivity and 75% specificity. After a mean follow-up of 15 ± 7 months, freedom from arrhythmia recurrence was significantly higher in left-side ablation (Group P + Group L) than additional RA ablation (Group R) (P = 0.024). CONCLUSION: Baseline mean AF CL may identify the subset of patients in whom persistent AF can be terminated by different extent of substrate ablation, which may in turn predict the chance of recurrence. However, baseline RA to LA AF CL gradient cannot predict the need for additional RA ablation.

Interplay between clathrin and Rab5 controls the early phagocytic trafficking and intracellular survival of Brucella abortus within HeLa cells.

Lipid raft-associated clathrin is essential for host-pathogen interactions during infection. Brucella abortus is an intracellular pathogen that circumvents host defenses, but little is known about the precise infection mechanisms that involve interaction with lipid raft-associated mediators. The aim of this study was to elucidate the clathrin-mediated phagocytic mechanisms of B. abortus. The clathrin dependence of B. abortus infection in HeLa cells was investigated using an infection assay and immunofluorescence microscopy. The redistribution of clathrin in the membrane and in phagosomes was investigated using sucrose gradient fractionation of lipid rafts and the isolation of B. abortus-containing vacuoles, respectively. Clathrin and dynamin were concentrated into lipid rafts during B. abortus infection, and the entry and intracellular survival of B. abortus within HeLa cells were abrogated by clathrin inhibition. Clathrin disruption decreased actin polymerization and the colocalization of B. abortus-containing vacuoles with clathrin and Rab5 but not lysosome-associated membrane protein 1 (LAMP-1). Thus, our data demonstrate that clathrin plays a fundamental role in the entry and intracellular survival of B. abortus via interaction with lipid rafts and actin rearrangement. This process facilitates the early intracellular trafficking of B. abortus to safe replicative vacuoles.

Primary cardiac lymphoma presenting as an atypical type of hypertrophic cardiomyopathy.

Primary cardiac lymphoma (PCL) is a very rare malignancy although cardiac involvement with the disseminated disease is not uncommon. We present a case of a 43-year-old man with PCL that initially presented as marked thickening of all cardiac walls and was mistakenly diagnosed as an atypical type of hypertrophic cardiomyopathy. The diagnosis of PCL was made with a delay of 9 months after the initial presentation, when atypical lymphocytes staining positive for CD79a and CD20 were demonstrated in the rapidly growing mediastinal and neck mass. Anthracycline-based chemotherapy and anti-CD20 immunotherapy resulted in a remarkable reduction in cardiac wall thickness and mediastinal mass. The first lesson to be learnt from this case is that PCL can present as a diffuse infiltrative disease without a mass. The second lesson is that prompt exploratory thoracotomy should not be delayed when the diagnosis is elusive.

Patterns of decrease in multidirectional myocardial deformations in patients with fluctuating left ventricular ejection fraction.

Few studies have examined the variations in longitudinal/circumferential/radial strain (LS/CS/RS) and strain rate (LSr/CSr/RSr) in individual hearts when the left ventricular ejection fraction (LVEF) has changed. We hypothesized the relationships of strain/strain rate and LVEF are not linear, but vary with multiple inflection points (IPs) in individual hearts.Twenty-five patients with fluctuating LVEF (ΔLVEF > 10%) who had 2-D speckle tracking echocardiography available for analysis were enrolled. After models of best fit were obtained from the 'collective' plots to determine inflection points, the decrements of slopes above inflection points (IP) were compared with those below IPs in the 'individual hearts' plots.In the 'collective' plots, both LS and LSr linearly decreased in proportion to LVEF when LVEF ≥ 40% but remained constant regardless of LVEF when LVEF < 40% (IPs when LVEF = 40%, P < 0.0001). The RS-LVEF relationship was sigmoid with two IPs when LVEF = 30% and 50% (P < 0.0001). However, in the 'individual hearts' plots, the decrements of slopes above and below IPs were not different for LS-LVEF and LSr-LVEF, and marginally different for RS-LVEF (P = 0.049, across IP when LVEF = 50%).Collectively, the relationship of LS/LSr/RS and LVEF seemed to be not linear, but inflective, however, we could not prove the inflective relationship in individual hearts with fluctuating LVEF. Further study with more patients is needed to prove our hypothesis.

Valley-centre tandem perovskite light-emitting diodes.

Perovskite light-emitting diodes (PeLEDs) have emerged as a promising new light source for displays. The development roadmap for commercializing PeLEDs should include a tandem device structure, specifically by stacking a thin nanocrystal PeLED unit and an organic light-emitting diode unit, which can achieve a vivid and efficient tandem display; however, simply combining light-emitting diodes with different characteristics does not guarantee both narrowband emission and high efficiency, as it may cause a broadened electroluminescence spectra and a charge imbalance. Here, by conducting optical simulations of the hybrid tandem (h-tandem) PeLED, we have discovered a crucial optical microcavity structure known as the h-tandem valley, which enables the h-tandem PeLED to emit light with a narrow bandwidth. Specifically, the centre structure of the h-tandem valley (we call it valley-centre tandem) demonstrates near-perfect charge balance and optimal microcavity effects. As a result, the h-tandem PeLED achieves a high external quantum efficiency of 37.0% and high colour purity with a narrow full-width at half-maximum of 27.3 nm (versus 64.5 nm in organic light-emitting diodes) along with a fast on-off response. These findings offer a new strategy to overcome the limitations of nanocrystal-based PeLEDs, providing valuable optical and electrical guidelines for integrating different types of light-emitting device into practical display applications.

Toll-like receptor 4-linked Janus kinase 2 signaling contributes to internalization of Brucella abortus by macrophages.

Brucella abortus is an intracellular pathogen that uses a crafty strategy to invade and proliferate within host cells, but the distinct signaling pathways associated with phagocytic mechanisms of B. abortus remain unclear. The present study was performed to test the hypothesis that Toll-like receptor 4 (TLR4)-linked signaling interacting with Janus kinase 2 (JAK2) plays an essential role in B. abortus phagocytosis by macrophages. The effects of TLR4-JAK2 signaling on B. abortus phagocytosis in murine macrophage RAW 264.7 cells were observed through an infection assay and confocal microscopy. We determined that the uptake of B. abortus was negatively affected by the dysfunction of TLR4 and JAK2. F-actin polymerization detected by flow cytometry and F-actin assay was amplified for B. abortus entry, whereas that event was attenuated by the disruption of TLR4 and JAK2. Importantly, JAK2 phosphorylation and actin skeleton reorganization were suppressed immediately after B. abortus infection in bone marrow-derived macrophages (BMDMs) from TLR4(-/-) mice, showing the cooperation of JAK2 with TLR4. Furthermore, small GTPase Cdc42 participated in the intermediate pathway of TLR4-JAK2 signaling on B. abortus phagocytosis. Consequently, TLR4-associated JAK2 activation in the early cellular signaling events plays a pivotal role in B. abortus-induced phagocytic processes in macrophages, implying the pathogenic significance of JAK2-mediated entry. Here, we elucidate that this specific phagocytic mechanism of B. abortus might provide achievable strategies for inhibiting B. abortus invasion.

The role of a Brucella abortus lipoprotein in intracellular replication and pathogenicity in experimentally infected mice.

Brucella abortus, the causative agent of brucellosis, can survive and replicate within host cells. Understanding bacterial virulence factors and bacteria-host cell interactions is critical for controlling brucellosis. However, little is known regarding the pathogenic mechanisms of brucellosis. A lipoprotein mutant (Gene Bank ID: 3339351) of B. abortus showed a lower rate of intracellular replication than did the wild-type strain in HeLa cells and RAW 264.7 macrophages. The adherent activity of the lipoprotein mutant was slightly increased compared to that of the wild-type strain in HeLa cells. After infection into macrophages, the lipoprotein mutant co-localized with either late endosomes or lysosomes. In mice infected with the lipoprotein mutant, fewer lipoprotein mutants were recovered from the spleen at 8 weeks post-infection compared to the wild-type strain. The ability to protect the lipoprotein mutant against infection by the virulent B. abortus strain 544 was similar to that of strain RB51. Our results indicate that the B. abortus lipoprotein is an important factor for survival within phagocytes and mice, and the B. abortus lipoprotein mutant may help improve live vaccines used to control brucellosis.

RGS2-mediated intracellular Ca2+ level plays a key role in the intracellular replication of Brucella abortus within phagocytes.

BACKGROUND: Brucella abortus can proliferate within professional and nonprofessional phagocytic host cells and thereby successfully bypass the bacteriocidal effects of phagocytes. However, the intracellular survival mechanism and factors of virulence are not fully understood. METHODS: We have investigated the role of the regulator of G protein signaling 2 (RGS2), an intracellular calcium ([Ca(2+)](i)) regulator of the host cell, in the intracellular survival of B. abortus within phagocytes. RESULTS: B. abortus infection markedly induced RGS2 messenger RNA expression in early phase and increased the [Ca(2+)](i) level up to 24 hours postinfection within macrophages from wild-type mice. The [Ca(2+)](i) level, however, was not influenced by B. abortus infection within macrophages from RGS2-deficient mice. Furthermore, B. abortus survival was reduced within RGS2-deficient macrophages, and hence bacterial proliferation was inhibited in RGS2-deficient mice. Moreover, treatment with the Ca(2+) chelator ethylenediaminetetraacetic acid (EDTA) or 1,2-bis-(2-amino-phenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (BAPTA-AM) and the L-type Ca(2+) channel-blocking agent nifedipine or genistein also showed a reduced intracellular replication of B. abortus within macrophages. CONCLUSION: These results indicate that B. abortus infection induces host RGS2 expression and that up-regulation of [Ca(2+)](i) levels is an essential factor for the intracellular survival of B. abortus within phagocytes.