Extracellular Kir2.1C122Y Mutant Upsets Kir2.1-PIP2 Bonds and Is Arrhythmogenic in Andersen-Tawil Syndrome.

BACKGROUND: Andersen-Tawil syndrome type 1 is a rare heritable disease caused by mutations in the gene coding the strong inwardly rectifying K+ channel Kir2.1. The extracellular Cys (cysteine)122-to-Cys154 disulfide bond in the channel structure is crucial for proper folding but has not been associated with correct channel function at the membrane. We evaluated whether a human mutation at the Cys122-to-Cys154 disulfide bridge leads to Kir2.1 channel dysfunction and arrhythmias by reorganizing the overall Kir2.1 channel structure and destabilizing its open state. METHODS: We identified a Kir2.1 loss-of-function mutation (c.366 A>T; p.Cys122Tyr) in an ATS1 family. To investigate its pathophysiological implications, we generated an AAV9-mediated cardiac-specific mouse model expressing the Kir2.1C122Y variant. We employed a multidisciplinary approach, integrating patch clamping and intracardiac stimulation, molecular biology techniques, molecular dynamics, and bioluminescence resonance energy transfer experiments. RESULTS: Kir2.1C122Y mice recapitulated the ECG features of ATS1 independently of sex, including corrected QT prolongation, conduction defects, and increased arrhythmia susceptibility. Isolated Kir2.1C122Y cardiomyocytes showed significantly reduced inwardly rectifier K+ (IK1) and inward Na+ (INa) current densities independently of normal trafficking. Molecular dynamics predicted that the C122Y mutation provoked a conformational change over the 2000-ns simulation, characterized by a greater loss of hydrogen bonds between Kir2.1 and phosphatidylinositol 4,5-bisphosphate than wild type (WT). Therefore, the phosphatidylinositol 4,5-bisphosphate-binding pocket was destabilized, resulting in a lower conductance state compared with WT. Accordingly, on inside-out patch clamping, the C122Y mutation significantly blunted Kir2.1 sensitivity to increasing phosphatidylinositol 4,5-bisphosphate concentrations. In addition, the Kir2.1C122Y mutation resulted in channelosome degradation, demonstrating temporal instability of both Kir2.1 and NaV1.5 proteins. CONCLUSIONS: The extracellular Cys122-to-Cys154 disulfide bond in the tridimensional Kir2.1 channel structure is essential for the channel function. We demonstrate that breaking disulfide bonds in the extracellular domain disrupts phosphatidylinositol 4,5-bisphosphate-dependent regulation, leading to channel dysfunction and defects in Kir2.1 energetic stability. The mutation also alters functional expression of the NaV1.5 channel and ultimately leads to conduction disturbances and life-threatening arrhythmia characteristic of Andersen-Tawil syndrome type 1.

Inhibition of HIV replication through siRNA carried by CXCR4-targeted chimeric nanobody.

Small interfering RNA (siRNA) application in therapy still faces a major challenge with the lack of an efficient and specific delivery system. Current vehicles are often responsible for poor efficacy, safety concerns, and burden costs of siRNA-based therapeutics. Here, we describe a novel strategy for targeted delivery of siRNA molecules to inhibit human immunodeficiency virus (HIV) infection. Specific membrane translocation of siRNA inhibitor was addressed by an engineered nanobody targeting the HIV co-receptor CXCR4 (NbCXCR4) in fusion with a single-chain variable fragment (4M5.3) that carried the FITC-conjugated siRNA. 4M5.3-NbCXCR4 conjugate (4M5.3X4) efficiently targeted CXCR4+ T lymphocytes, specifically translocating siRNA by receptor-mediated endocytosis. Targeted delivery of siRNA directed to the mRNA of HIV transactivator tat silenced Tat-driven viral transcription and inhibited the replication of distinct virus clades. In summary, we have shown that the engineered nanobody chimera developed in this study constitutes an efficient and specific delivery method of siRNAs through CXCR4 receptor.

Kir2.1-NaV1.5 channelosome and its role in arrhythmias in inheritable cardiac diseases.

Sudden cardiac death in children and young adults is a relatively rare but tragic event whose pathophysiology is unknown at the molecular level. Evidence indicates that the main cardiac sodium channel (NaV1.5) and the strong inward rectifier potassium channel (Kir2.1) physically interact and form macromolecular complexes (channelosomes) with common partners, including adapter, scaffolding, and regulatory proteins that help them traffic together to their eventual membrane microdomains. Most important, dysfunction of either or both ion channels has direct links to hereditary human diseases. For example, certain mutations in the KCNJ2 gene encoding the Kir2.1 protein result in Andersen-Tawil syndrome type 1 and alter both inward rectifier potassium and sodium inward currents. Similarly, trafficking-deficient mutations in the gene encoding the NaV1.5 protein (SCN5A) result in Brugada syndrome and may also disturb both inward rectifier potassium and sodium inward currents. Moreover, gain-of-function mutations in KCNJ2 result in short QT syndrome type 3, which is extremely rare but highly arrhythmogenic, and can modify Kir2.1-NaV1.5 interactions in a mutation-specific way, further highlighting the relevance of channelosomes in ion channel diseases. By expressing mutant proteins that interrupt or modify Kir2.1 or NaV1.5 function in animal models and patient-specific pluripotent stem cell-derived cardiomyocytes, investigators are defining for the first time the mechanistic framework of how mutation-induced dysregulation of the Kir2.1-NaV1.5 channelosome affects cardiac excitability, resulting in arrhythmias and sudden death in different cardiac diseases.

The Kir2.1E299V mutation increases atrial fibrillation vulnerability while protecting the ventricles against arrhythmias in a mouse model of short QT syndrome type 3.

AIMS: Short QT syndrome type 3 (SQTS3) is a rare arrhythmogenic disease caused by gain-of-function mutations in KCNJ2, the gene coding the inward rectifier potassium channel Kir2.1. We used a multidisciplinary approach and investigated arrhythmogenic mechanisms in an in-vivo model of de-novo mutation Kir2.1E299V identified in a patient presenting an extremely abbreviated QT interval and paroxysmal atrial fibrillation. METHODS AND RESULTS: We used intravenous adeno-associated virus-mediated gene transfer to generate mouse models, and confirmed cardiac-specific expression of Kir2.1WT or Kir2.1E299V. On ECG, the Kir2.1E299V mouse recapitulated the QT interval shortening and the atrial-specific arrhythmia of the patient. The PR interval was also significantly shorter in Kir2.1E299V mice. Patch-clamping showed extremely abbreviated action potentials in both atrial and ventricular Kir2.1E299V cardiomyocytes due to a lack of inward-going rectification and increased IK1 at voltages positive to -80 mV. Relative to Kir2.1WT, atrial Kir2.1E299V cardiomyocytes had a significantly reduced slope conductance at voltages negative to -80 mV. After confirming a higher proportion of heterotetrameric Kir2.x channels containing Kir2.2 subunits in the atria, in-silico 3D simulations predicted an atrial-specific impairment of polyamine block and reduced pore diameter in the Kir2.1E299V-Kir2.2WT channel. In ventricular cardiomyocytes, the mutation increased excitability by shifting INa activation and inactivation in the hyperpolarizing direction, which protected the ventricle against arrhythmia. Moreover, Purkinje myocytes from Kir2.1E299V mice manifested substantially higher INa density than Kir2.1WT, explaining the abbreviation in the PR interval. CONCLUSION: The first in-vivo mouse model of cardiac-specific SQTS3 recapitulates the electrophysiological phenotype of a patient with the Kir2.1E299V mutation. Kir2.1E299V eliminates rectification in both cardiac chambers but protects against ventricular arrhythmias by increasing excitability in both Purkinje-fiber network and ventricles. Consequently, the predominant arrhythmias are supraventricular likely due to the lack of inward rectification and atrial-specific reduced pore diameter of the Kir2.1E299V-Kir2.2WT heterotetramer.

EVOLUTION OF DIAGNOSTIC DELAY IN PEDIATRIC INFLAMMATORY BOWEL DISEASE AND THE IMPACT OF THE COVID-19 PANDEMIC.

BACKGROUND: Pediatric inflammatory bowel disease (IBD) is increasingly prevalent, but diagnosis can still be challenging. Diagnostic delay is particularly deleterious in this age group. OBJECTIVE: This study explores the evolution of diagnostic delay in pediatric IBD and the influence of the COVID-19 pandemic. METHODS: Retrospective study including all pediatric IBD patients diagnosed during 2014, 2019 and 2020 in a tertiary hospital. Diagnostic delay, time to first medical visit, time to pediatric gastroenterologist (PG) visit and time to diagnosis were calculated and compared within a gap of five years (2019 and 2014) and with the year of onset of the pandemic (2020 and 2019). RESULTS: A total of 93 participants were included (2014: 32, 2019: 30, 2020: 31). No significant differences were observed in diagnostic delay, time to first medical visit in Crohn's disease (CD), time to PG visit and time to diagnosis when comparing 2019-2014 and 2020-2019. Time to first visit in ulcerative colitis (UC) and Undetermined-IBD increased in 2019 (P=0.03), with new decrease in 2020 (P=0.04). Diagnostic delay was longer in DC compared to UC plus Undetermined-IBD. CONCLUSION: Diagnostic delay is still an important matter in pediatric IBD, with no significant change over the last years. The time to the first PG visit and the time for diagnosis seem to have the greatest impact on diagnostic delay. Thus, strategies to enhance recognition of IBD symptoms among first-line physicians and to improve communication, facilitating referral, are of utmost importance. Despite the restraints in the health care system caused by the pandemic, time to diagnosis in pediatric IBD was not impaired during 2020 in our center.

Prevalence and Predictive Factors of Exclusive Breastfeeding in the First Six Months of Life.

INTRODUCTION: Exclusive breastfeeding (EBF) is currently recommended until six months of age. The Baby-friendly Hospital (BFH) initiative an international program to promote breastfeeding, was launched in Portugal in 1994. The aim of this study was to identify the prevalence and factors influencing breastfeeding in the first six months of life and to compare the results with a study carried out in 1999 including population from the same geographic area. MATERIAL AND METHODS: A prospective, longitudinal and observational study was carried out in two hospitals in the Lisbon metropolitan area, one BFH and another non-BFH. It consisted of different questionnaires answered by mothers at three distinct moments (zero, three and six months). The first questionnaire was applied between February and June 2019. RESULTS: A total of 423 infants were included, 324 from the BFH and 99 from the non-BFH. The breastfeeding rate was 94.3% at discharge, 78.2% at three months and 64.4% at six months, whereas EBF rate was 74.2%, 51.8% and 25.6% respectively. All women on EBF at six months, except one, were breastfeeding on demand. The discontinuation of EBF was associated with delayed skin-to-skin contact, Neonatal Intensive Care Unit admission, pacifier and artificial teats use, mother's return to work earlier and lower education levels. Conversely, factors that promote EBF were older gestational age, adequate birthweight, breastfeeding initiation in the first hour of life, rooming-in practice, shorter hospital stay and absence of infant's illnesses. Compared with 1999, although there was a significant improvement of breastfeeding rates at three and six months, the EBF rate was similar at six months (23%). Both studies identified the mother's lower education level and mother's return to work as contributing factors to breastfeeding discontinuation. CONCLUSION: Our results are in agreement with previously reported causes of breastfeeding discontinuation and emphasize the importance of sociocultural factors. Compared with 1999, the breastfeeding rates in this Portuguese population increased significantly at three and six months. However, it is still necessary to improve in order to achieve the World Health Organization global target.

Molecular stratification of arrhythmogenic mechanisms in the Andersen Tawil syndrome.

Andersen-Tawil syndrome (ATS) is a rare inheritable disease associated with loss-of-function mutations in KCNJ2, the gene coding the strong inward rectifier potassium channel Kir2.1, which forms an essential membrane protein controlling cardiac excitability. ATS is usually marked by a triad of periodic paralysis, life-threatening cardiac arrhythmias and dysmorphic features, but its expression is variable and not all patients with a phenotype linked to ATS have a known genetic alteration. The mechanisms underlying this arrhythmogenic syndrome are poorly understood. Knowing such mechanisms would be essential to distinguish ATS from other channelopathies with overlapping phenotypes and to develop individualized therapies. For example, the recently suggested role of Kir2.1 as a countercurrent to sarcoplasmic calcium reuptake might explain the arrhythmogenic mechanisms of ATS and its overlap with catecholaminergic polymorphic ventricular tachycardia. Here we summarize current knowledge on the mechanisms of arrhythmias leading to sudden cardiac death in ATS. We first provide an overview of the syndrome and its pathophysiology, from the patient's bedside to the protein and discuss the role of essential regulators and interactors that could play a role in cases of ATS. The review highlights novel ideas related to some post-translational channel interactions with partner proteins that might help define the molecular bases of the arrhythmia phenotype. We then propose a new all-embracing classification of the currently known ATS loss-of-function mutations according to their position in the Kir2.1 channel structure and their functional implications. We also discuss specific ATS pathogenic variants, their clinical manifestations, and treatment stratification. The goal is to provide a deeper mechanistic understanding of the syndrome toward the development of novel targets and personalized treatment strategies.

Extracellular cysteine disulfide bond break at Cys122 disrupts PIP2-dependent Kir2.1 channel function and leads to arrhythmias in Andersen-Tawil Syndrome.

Background: Andersen-Tawil Syndrome Type 1 (ATS1) is a rare heritable disease caused by mutations in the strong inwardly rectifying K+ channel Kir2.1. The extracellular Cys122-to-Cys154 disulfide bond in the Kir2.1 channel structure is crucial for proper folding, but has not been associated with correct channel function at the membrane. We tested whether a human mutation at the Cys122-to-Cys154 disulfide bridge leads to Kir2.1 channel dysfunction and arrhythmias by reorganizing the overall Kir2.1 channel structure and destabilizing the open state of the channel. Methods and Results: We identified a Kir2.1 loss-of-function mutation in Cys122 (c.366 A>T; p.Cys122Tyr) in a family with ATS1. To study the consequences of this mutation on Kir2.1 function we generated a cardiac specific mouse model expressing the Kir2.1C122Y mutation. Kir2.1C122Y animals recapitulated the abnormal ECG features of ATS1, like QT prolongation, conduction defects, and increased arrhythmia susceptibility. Kir2.1C122Y mouse cardiomyocytes showed significantly reduced inward rectifier K+ (IK1) and inward Na+ (INa) current densities independently of normal trafficking ability and localization at the sarcolemma and the sarcoplasmic reticulum. Kir2.1C122Y formed heterotetramers with wildtype (WT) subunits. However, molecular dynamic modeling predicted that the Cys122-to-Cys154 disulfide-bond break induced by the C122Y mutation provoked a conformational change over the 2000 ns simulation, characterized by larger loss of the hydrogen bonds between Kir2.1 and phosphatidylinositol-4,5-bisphosphate (PIP2) than WT. Therefore, consistent with the inability of Kir2.1C122Y channels to bind directly to PIP2 in bioluminescence resonance energy transfer experiments, the PIP2 binding pocket was destabilized, resulting in a lower conductance state compared with WT. Accordingly, on inside-out patch-clamping the C122Y mutation significantly blunted Kir2.1 sensitivity to increasing PIP2 concentrations. Conclusion: The extracellular Cys122-to-Cys154 disulfide bond in the tridimensional Kir2.1 channel structure is essential to channel function. We demonstrated that ATS1 mutations that break disulfide bonds in the extracellular domain disrupt PIP2-dependent regulation, leading to channel dysfunction and life-threatening arrhythmias.

Influence of SARS-CoV-2 pandemic on sleep habits in a pediatric population.

Objective: Assessment of changes in sleep habits at home in children during COVID-19 lockdown. Methods: Retrospective, transversal study in a pediatric ward of a level II hospital. Questionnaires concerning sleep quality, patterns and its modifications during lockdown were distributed from June to August 2020. Comparison with a control sample from previous study (2019). Statistical analysis on SPSS Statistics23. Results: Two groups were compared: during lockdown (n=36, mean age 9.3 years-old) and before lockdown (n=48, mean age 8.8 years-old). 55.6% stated changes in sleep patterns. There was an increase in sleep hours, specifically in school-aged children (p=0.05) and adolescents (p=0.03), with no impact in global subjective sleep quality. Significative increase in screen hours (p=0.02) and its use after dinner (p=0.04). Discussion: Changes in sleep patterns during lockdown were frequent, alongside a higher use of screens. However, these did not affect the subjective sleep quality nor increased the occurrence of sleep disturbances.

Reversible Cerebral Vasoconstriction Syndrome in a Previously Healthy Child: A Case Report.

Objectives: We describe the case of a healthy boy diagnosed with reversible cerebral vasoconstriction syndrome (RCVS) and posterior reversible encephalopathy syndrome (PRES). Methods: He was identified after presenting in the emergency department (ED). A review of the 5 previous cases of RCVS complicated with PRES reported in the literature was performed. Results: A 9-year-old boy was brought to the ED for intense, throbbing headache and vomiting. Physical and neurologic examinations were normal. Brain CT and CSF examination were unremarkable, and he was discharged after symptomatic relief. Five days later, he returned to the ED for generalized tonic-clonic seizures that ceased with levetiracetam. MRI with angiography showed PRES. Systolic hypertension refractory to therapy was documented. New-onset fluctuating right-sided paresis and paresthesia appeared, so MRI was repeated, showing diffuse cerebral vasoconstriction suggesting RCVS. Nimodipine was started with complete resolution of symptoms and normalization of blood pressure. Four weeks after discharge, TD and MRI showed total vasospasm resolution. There was no recurrence in 12-month follow-up. Discussion: This case emphasizes the interconnection between RCVS and PRES, highlighting the need to include both as differential diagnoses for severe headache and the essential role of MR angiography in the investigation.

Impact of COVID-19 in Pediatric Patients and Young Adults with Inflammatory Bowel Disease.

Introduction: Acute COVID-19 in pediatric and young adult patients tends to be milder in severity compared to adult infection. Recent studies seem to show that inflammatory bowel disease (IBD) patients are at no greater risk than the general population. We aim to describe our experience in the follow-up of pediatric and young adult patients with IBD followed in our center and determine possible risk factors of said population for severe COVID-19. Methods: We performed a retrospective study of all patients aged under 25 years followed for IBD at the Unit of Pediatric Gastroenterology in a tertiary center between December 2019 and April 2021 evaluating the incidence of COVID-19 and characterization of positive cases. Results: Of the 268 participants, 24 had COVID-19: the mean age was 19 years old and gender had an equal distribution; 75% (n = 18) had Crohn's disease, whereas only 25% (n = 6) had ulcerative colitis. Most patients were in clinical remission (n = 21). The majority of patients were under treatment with a tumor necrosis factor (TNF) antagonist (58%, n = 14), mainly infliximab, and most had no comorbidities other than IBD (83%). Regarding COVID-19, 17% of the patients were asymptomatic while the rest had only mild symptoms. There were no reported gastrointestinal complaints, no complications nor hospitalizations. Most patients did not require interruption of their IBD treatment. Conclusions: Our data suggest that pediatric and young adult IBD patients have a low risk for complications and hospitalization, regardless of IBD treatment. We believe that this experience is encouraging and allows for safe counseling regarding treatment options and school attendance in pediatric and young adult IBD patients.

Introdução: Na população pediátrica e de jovens adultos a gravidade da COVID-19 tende a ser moderada quando comparada com os doentes adultos. Os estudos mais recentes sugerem que os doentes com doença inflamatória intestinal (DII) não têm risco acrescido em relação à população geral. O objetivo do presente estudo é a descrição da nossa experiência no follow-up de crianças e jovens adultos com DII a COVID-19 e determinar a existência de possíveis fatores de risco para doença grave na referida população. Métodos: Foi realizado um estudo retrospetivo de todos os doentes com idade inferior a 25 anos, seguidos na Unidade de Gastrenterologia Pediátrico de um centro terciário por DII, com avaliação da incidência de COVID-19 entre dezembro de 2019 e abril de 2021, e caracterização dos casos postivos. Resultados: Entre os 268 participantes, 24 tiveram COVID-19. A idade média foi de 19 anos com uma distribuição por género equiparável. Destes, 75% (n = 18) tinham doença de Crohn, enquanto 25% (6) tinham colite ulcerosa. A maior parte dos doentes apresentavam-se em remissão clínica (n = 21) e, à data da doença COVID-19. A sua maioria, os doentes encontravam-se sob tratamento com antagonistas do fator de necrose tumoral (58%, n = 14), predominantemente o infliximab, e a generalidade dos doentes (83%) não apresentava outras comorbilidades além da DII. Relativamente à COVID-19, 17% eram assintomáticos enquanto os restantes apresentavam apenas sintomas ligeiros. Não houve relato de queixas gastrointestinais, complicações ou necessidade de hospitalização. Na maioria dos casos, não houve necessidade de interromper o tratamento da DII. Conclusão: Os nossos dados sugerem que doentes pediátricos e jovens adultos com DII apresentam um risco baixo de complicações ou hospitalização associados à COVID-19, independentemente do tratamento em curso para a DII. Este estudo apresenta resultados encorajadores e contribui para o aconselhamento adequado e fundamentado aos doentes e respetivos cuidadores, no que diz respeito às opções terapêuticas e frequência escolar dos doentes pediátricos e jovens adultos com DII.

Prevalence, multimodality imaging characterization, and mid-term prognosis of quadricuspid aortic valves: an analysis of eight cases, based on 160 004 exams performed during 12 years in a tertiary care hospital.

AIMS: Quadricuspid aortic valve (QAV) is a rare abnormality, which may cause aortic regurgitation (AR) requiring surgical intervention in some patients. The characteristics associated with aortic valve functional degeneration in patients with QAV are still unknown. The aim of this study is to describe QAV prevalence, characterize the disease by multimodality imaging, evaluate predictors of severe AR, and assess mid-term prognosis. METHODS AND RESULTS: Retrospective search in imaging exams database of one tertiary centre, for patients diagnosed with QAV between January 2007 and September 2019. QAV was characterized by cardiac computed tomography, transthoracic/transoesophageal echocardiography, and cardiac magnetic resonance. A total of 160 004 exams were reviewed and eight patients with QAV were identified (50% men, mean age 53.5 ± 10.7 years). The prevalence of QAV was 0.005%. During a median follow-up of 52 months (interquartile range 16-88), there were no deaths. Seven patients (88%) had pure AR (three severe, one moderate, and three mild) and one patient (12%) had moderate AR and moderate aortic stenosis. Three patients (38%) with severe AR underwent valve surgery (two replacements and one repair). Analysis of predictors of severe AR was not statistically significant. CONCLUSION: QAV is a rare congenital cardiac defect, with a prevalence of 0.005% in our study. Its predominant functional abnormality was regurgitation and about one-third of the patients required aortic valve surgery. Multimodality imaging may play a pivotal role in assessing patients with QAV with significant valve dysfunction or associated congenital heart disease and improve their treatment strategy.

Long-term outcomes after radiofrequency catheter ablation of the atrioventricular node: The experience of a Portuguese tertiary center.

INTRODUCTION: In patients with supraventricular arrhythmias and high ventricular rate, unresponsive to rate and rhythm control therapy or catheter ablation, atrioventricular (AV) node ablation may be performed. OBJECTIVES: To assess long-term outcomes after AV node ablation and to analyze predictors of adverse events. METHODS: We performed a detailed retrospective analysis of all patients who underwent AV node ablation between February 1997 and February 2019, in a single Portuguese tertiary center. RESULTS: A total of 123 patients, mean age 69±9 years and 52% male, underwent AV node ablation. Most of them presented atrial fibrillation at baseline (65%). During a median follow-up of 8.5 years (interquartile range 3.8-11.8), patients improved heart failure (HF) functional class (NYHA class III-IV 46% versus 13%, p=0.001), and there were reductions in hospitalizations due to HF (0.98±1.3 versus 0.28±0.8, p=0.001) and emergency department (ED) visits (1.1±1 versus 0.17±0.7, p=0.0001). There were no device-related complications. Despite permanent pacemaker stimulation, left ventricular ejection fraction did not worsen (47±13% vs. 47%±12, p=0.63). Twenty-eight patients died (23%). The number of ED visits due to HF before AV node ablation was an independent predictor of the composite adverse outcome (OR 1.8, 95% CI 1.24-2.61, p=0.002). CONCLUSIONS: Despite pacemaker dependency, the clinical benefit of AV node ablation persisted at long-term follow-up. The number of ED visits due to HF before AV node ablation was an independent predictor of the composite adverse outcome. AV node ablation should probably be considered earlier in the treatment of patients with supraventricular arrhythmias and HF, especially in cases that are unsuitable for selective ablation of the specific arrhythmia.

Therapeutic Antibody Engineering and Selection Strategies.

Antibody drugs became an increasingly important element of the therapeutic landscape. Their accomplishment has been driven by many unique properties, in particular by their very high specificity and selectivity, in contrast to the off-target liabilities of small molecules (SMs). Antibodies can bring additional functionality to the table with their ability to interact with the immune system, and this can be further manipulated with advances in antibody engineering.The expansion of strategies related to discovery technologies of monoclonal antibodies (mAbs) (phage display, yeast display, ribosome display, bacterial display, mammalian cell surface display, mRNA display, DNA display, transgenic animal, and human B cell derived) opened perspectives for the screening and the selection of therapeutic antibodies for, theoretically, any target from any kind of organism. Moreover, antibody engineering technologies were developed and explored to obtain chosen characteristics of selected leading candidates such as high affinity, low immunogenicity, improved functionality, improved protein production, improved stability, and others. This chapter contains an overview of discovery technologies, mainly display methods and antibody humanization methods for the selection of therapeutic humanized and human mAbs that appeared along the development of these technologies and thereafter. The increasing applications of these technologies will be highlighted in the antibody engineering area (affinity maturation, guided selection to obtain human antibodies) giving promising perspectives for the development of future therapeutics.

Magnetic Precipitation: A New Platform for Protein Purification.

One of the trends in downstream processing comprises the use of "anything-but-chromatography" methods to overcome the current downfalls of standard packed-bed chromatography. Precipitation and magnetic separation are two techniques already proven to accomplish protein purification from complex media, yet never used in synergy. With the aim to capture antibodies directly from crude extracts, a new approach combining precipitation and magnetic separation is developed and named as affinity magnetic precipitation. A precipitation screening, based on the Hofmeister series, and a commercial precipitation kit are tested with affinity magnetic particles to assess the best condition for antibody capture from human serum plasma and clarified cell supernatant. The best conditions are obtained when using PEG3350 as precipitant at 4 °C for 1 h, reaching 80% purity and 50% recovery of polyclonal antibodies from plasma, and 99% purity with 97% recovery yield of anti-TNFα mAb from cell supernatants. These results show that the synergetic use of precipitation and magnetic separation can represent an alternative for the efficient capture of antibodies.

The effects of transcatheter aortic valve implantation on cardiac electrical properties.

INTRODUCTION: Transcatheter aortic valve implantation (TAVI) is associated with cardiac electrical disturbances. However, beyond the risks of pacemaker implantation, few studies have performed a detailed assessment of the effects of TAVI on several cardiac electrical properties. OBJECTIVES: To assess the frequency and type of electrocardiographic disturbances following TAVI, according to the type of prostheses and to assess predictors of these disturbances. METHODS: We performed a detailed retrospective analysis of all electrocardiograms in patients who underwent TAVI, before and after the procedure, at a tertiary center from August 2007 to October 2016. Patients with permanent pacemakers were excluded. RESULTS: We included 182 patients (78±8 years; 56% female) and self-expanding prostheses (SEP) were implanted in 54%. Most patients (80%) were in sinus rhythm at baseline. After TAVI, 21% of patients developed new-onset atrial fibrillation and there was a significant increase in PR interval at discharge (186±41 ms vs. 176±32; p=0.003), which was not maintained after at six-month follow-up (181±35 ms, p=0.06). There was also a significant increase in QRS duration at discharge (129±28 ms vs. 114±25 at baseline p<0.0001), which persisted at six-months (122±28 ms, p<0.0001). New-onset left-bundle branch block (LBBB) was observed in 25% of patients. The depth of valve implantation was a predictor of new LBBB at discharge after multivariate analysis (OR 37.6, 95% CI 14.6-65.2, p=0.001). CONCLUSIONS: The main electrocardiographic disturbances post TAVI were PR prolongation, increased QRS and new-onset LBBB. These disturbances were more pronounced in patients undergoing SEP implantation and tended to improve at six-month follow-up. The depth of valve implantation was a predictor of conduction disturbances.

Chimeric Small Antibody Fragments as Strategy to Deliver Therapeutic Payloads.

Antibody-drug conjugates (ADCs) represent an innovative class of biopharmaceuticals, which aim at achieving a site-specific delivery of cytotoxic agents to the target cell. The use of ADCs represents a promising strategy to overcome the disadvantages of conventional pharmacotherapy of cancer or neurological diseases, based on cytotoxic or immunomodulatory agents. ADCs consist of monoclonal antibodies attached to biologically active drugs by means of cleavable chemical linkers. Advances in technologies for the coupling of antibodies to cytotoxic drugs promise to deliver greater control of drug pharmacokinetic properties and to significantly improve pharmacodelivery applications, minimizing exposure of healthy tissue. The clinical success of brentuximab vedotin and trastuzumab emtansine has led to an extensive expansion of the clinical ADC pipeline. Although the concept of an ADC seems simple, designing a successful ADC is complex and requires careful selection of the receptor antigen, antibody, linker, and payload. In this review, we explore insights in the antibody and antigen requirements needed for optimal payload delivery and support the development of novel and improved ADCs for the treatment of cancer and neurological diseases.

Evolução do atraso diagnóstico na doença inflamatória intestinal em idade pediátrica e o impacto da pandemia COVID-19 / Evolution of diagnostic delay in pediatric inflammatory bowel disease and the impact of the covid-19 pandemic

ABSTRACT Background: Pediatric inflammatory bowel disease (IBD) is increasingly prevalent, but diagnosis can still be challenging. Diagnostic delay is particularly deleterious in this age group. Objective This study explores the evolution of diagnostic delay in pediatric IBD and the influence of the COVID-19 pandemic. Methods Retrospective study including all pediatric IBD patients diagnosed during 2014, 2019 and 2020 in a tertiary hospital. Diagnostic delay, time to first medical visit, time to pediatric gastroenterologist (PG) visit and time to diagnosis were calculated and compared within a gap of five years (2019 and 2014) and with the year of onset of the pandemic (2020 and 2019). Results A total of 93 participants were included (2014: 32, 2019: 30, 2020: 31). No significant differences were observed in diagnostic delay, time to first medical visit in Crohn's disease (CD), time to PG visit and time to diagnosis when comparing 2019-2014 and 2020-2019. Time to first visit in ulcerative colitis (UC) and Undetermined-IBD increased in 2019 (P=0.03), with new decrease in 2020 (P=0.04). Diagnostic delay was longer in DC compared to UC plus Undetermined-IBD. Conclusion Diagnostic delay is still an important matter in pediatric IBD, with no significant change over the last years. The time to the first PG visit and the time for diagnosis seem to have the greatest impact on diagnostic delay. Thus, strategies to enhance recognition of IBD symptoms among first-line physicians and to improve communication, facilitating referral, are of utmost importance. Despite the restraints in the health care system caused by the pandemic, time to diagnosis in pediatric IBD was not impaired during 2020 in our center.

RESUMO Contexto Apesar da prevalência crescente da doença inflamatória intestinal (DII) em idade pediátrica, o seu diagnóstico pode ser desafiante. Um atraso no diagnóstico é particularmente deletério nesta faixa etária. Objetivo Este estudo investiga a evolução do atraso diagnóstico na DII pediátrica e o impacto da pandemia COVID-19 no mesmo. Métodos Estudo retrospetivo que incluiu todos os doentes em idade pediátrica diagnosticados com DII durante 2014, 2019 e 2020 num hospital terciário. O atraso diagnóstico, o tempo para a primeira visita médica, o tempo para a primeira visita ao gastroenterologista pediátrico (GP) e o tempo para o diagnóstico foram calculados e comparados num intervalo de cinco anos (2019 e 2014) e com o ano marcado pelo surgimento da pandemia COVID-19 (2020 e 2019). Resultados Foram incluídos 93 participantes (2014: 32, 2019: 30, 2020: 31). Não se observou diferença significativa no atraso diagnóstico, no tempo para a primeira visita médica na doença de Crohn (DC), no tempo para a primeira visita ao GP e no tempo para o diagnóstico após comparação entre 2019-2014 e 2020-2019. Na colite ulcerosa e colite indeterminada, o tempo para a primeira visita médica aumentou em 2019 (P=0,03), com nova diminuição em 2020 (P=0,04). O atraso diagnóstico foi superior na DC comparativamente com a colite ulcerosa e colite indeterminada. Conclusão O atraso diagnóstico na DII pediátrica continua a ser um tema importante, que não sofreu alteração significativa ao longo dos últimos anos. O tempo para a primeira visita ao GP e o tempo para o diagnóstico parecem ter maior impacto no atraso diagnóstico, pelo que são necessárias estratégias para aumentar o reconhecimento dos sintomas da DII entre os médicos de primeira linha, bem como melhorar a comunicação e a referenciação. Apesar das restrições causadas pela pandemia no sistema de saúde, o tempo para o diagnóstico na DII pediátrica não foi comprometido no nosso centro em 2020.