[Narrative review of the immune response against coronavirus: An overview, applicability for SARS-COV-2, and therapeutic implications]

Mortality predictors in patients with COVID-19 pneumonia: a machine learning approach using eXtreme Gradient Boosting model

Recently, global health has seen an increase in demand for assistance as a result of the COVID-19 pandemic. This has prompted many researchers to conduct different studies looking for variables that are associated with increased clinical risk, and find effective and safe treatments. Many of these studies have been limited by presenting small samples and a large data set. Using machine learning (ML) techniques we can detect parameters that help us to improve clinical diagnosis, since they are a system for the detection, prediction and treatment of complex data. ML techniques can be valuable for the study of COVID-19, especially because they can uncover complex patterns in large data sets. This retrospective study of 150 hospitalized adult COVID-19 patients, of which we established two groups, those who died were called Case group (n = 53) while the survivors were Control group (n = 98). For analysis, a supervised learning algorithm eXtreme Gradient Boosting (XGBoost) has been used due to its good response compared to other methods because it is highly efficient, flexible and portable. In this study, the response to different treatments has been evaluated and has made it possible to accurately predict which patients have higher mortality using artificial intelligence, obtaining better results compared to other ML methods.

Persistent COVID-19 lung infection in a child with a primary immunodeficiency

SARS-CoV-2 infection in children with primary immunodeficiency disease (PID) and its complications have not yet been well described, the course of COVID-19 can range from mild illness to death. We aim to report the case of a child with a PID who develop a severe and persistent pulmonary COVID-19 infection. We present chronologically his clinical course, tests, interventions and radiological findings showing his irregular evolution and poor response to infection. This case highlights the need to accurately monitor the immune response in these cases to try to stop the progression of the damage.

Variants in ACE2; potential influences on virus infection and COVID-19 severity

The third pandemic of coronavirus infection, called COVID-19 disease, was first detected in November 2019th. Various determinants of disease progression such as age, sex, virus mutations, comorbidity, lifestyle, host immune response, and genetic background variation have caused clinical variability of COVID-19. The causative agent of COVID-19 is an enveloped coronavirus named severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) that invades host cells using an endocytic pathway. The SARS-CoV-2 spike protein is the main viral protein that contributes to the fusion of the virus particle to the host cell through angiotensin-converting enzyme 2 (ACE2). The highly conserved expression of ACE2 is found in various animals, which indicates its pivotal physiological function. The ACE2 has a crucial role in vascular, renal, and myocardial physiology. Genetic factors contributing to the outcome of SARS-CoV-2 infection are unknown; however, variants in the specific sites of ACE2 gene could be regarded as a main genetic risk factor for COVID-19. Given that ACE2 is the main site for virus landing on host cells, the effect of amino acid sequences of ACE2 on host susceptibility to COVID-19 seems reasonable. It would likely have a substantial role in the occurrence of a wide range of clinical symptoms. Several ACE2 variants can affect the protein stability, influencing the interaction between spike protein and ACE2 through imposing conformational changes while some other variants are known to cause a decrease or an increase in the ligand-receptor affinity. The other variations are located at the proteolytic cleavage site, which can influence virus infection; because soluble ACE2 can act as a decoy receptor for virus and decrease virus intake by cell surface ACE2. Notably, polymorphisms of regulatory and non-coding regions such as promoter in ACE2, can play crucial role in different expression levels of ACE2 among different individuals. Many studies should be performed to investigate the involvement of ACE2 polymorphism with susceptibility to COVID-19. Herein, we discuss some reported associations between variants of ACE2 and COVID-19 in details. In addition, the mode of action of ACE2 and its role in SARS-CoV-2 infection are highlighted which is followed by addressing the effects of several ACE2 variants on its protein stability, viral tropism or ligand-receptor affinity, secondary and tertiary structure or protein conformation, proteolytic cleavage site, and finally inter-individual clinical variability in COVID-19. The polymorphisms of regulatory regions of ACE2 and their effect on expression levels of ACE2 are also provided in this review. Such studies can improve the prediction of the affinity of mutant ACE2 variations with spike protein, and help the biopharmaceutical industry to design effective approaches for recombinant hACE2 therapy and vaccination of COVID-19 disease.

EMERGENCIA DE SARS-COV-2. ASPECTOS BÁSICOS SOBRE SU ORIGEN, EPIDEMIOLOGÍA, ESTRUCTURA Y PATOGENIA PARA CLÍNICOS

SARS-CoV-2 es el tercer coronavirus que emerge en las últimas dos décadas y produce la enfermedad denominada COVID-19 (enfermedad infecciosa por coronavirus 2019). Ha demostrado ser fácilmente transmisible entre humanos con una rápida diseminación mundial y declarada como pandemia el 11 de marzo 2020. A la fecha ha causado millones de casos y muertes, disrupción de servicios sanitarios y severas consecuencias sociales, económicas y políticas en todos los países. Los estudios filogenéticos lo relacionan con SARS-CoV presentes en murciélagos. Comparte características de patogenicidad con sus parientes más cercanos, SARS-CoV y MERS-CoV. 15 a 20% de los afectados presentan cuadros graves. A la fecha no se cuenta con antivirales efectivos ni vacunas. Para un adecuado control se hace imprescindible dilucidar aspectos epidemiológicos, moleculares y de patogenicidad. En esta revisión se presenta información básica sobre epidemiología, origen, estructura y patogenia de SARS-CoV-2.

Antibody-Based Immunotherapeutic Strategies for COVID-19

Global efforts to contain the coronavirus disease-2019 (COVID-19) include the development of novel preventive vaccines and effective therapeutics. Passive antibody therapies using convalescent plasma, SARS-CoV-2 (Severe-Acute-Respiratory-Syndrome-Corona-Virus-2)-specific neutralizing antibodies (NAbs), and the development of monoclonal antibodies (MAbs) are among the most promising strategies for prophylaxis and treatment of SARS-CoV-2 infections. In addition, several immunomodulatory antibodies acting via several mechanisms to boost the host immune defense against SARS-CoV-2 infection as well as to avoid the harmful overreaction of the immune system are currently under clinical trial. Our main objective is to present the current most up-to-date progress in some clinical trials registered at ClinicalTrials.gov. We highlight the pros and pitfalls of several SARS-CoV-2 antibody-based immunotherapeutics.

Alteraciones hematológicas en COVID-19

 El SARS (síndrome respiratorio agudo grave) es el estadio grave de la COVID-19 ocasionado por el SARS-CoV-2, que causa infecciones respiratorias en humanos y cuya transmisión se da principalmente por contacto. El virus ingresa a la célula huésped por la interacción de la proteína S con la enzima convertidora de angiotensina II (ACE2), presente en el tracto respiratorio, así como en monocitos, macrófagos, células endoteliales, corazón y tracto gastrointestinal. El aumento de IFN frena la replicación viral y activa la respuesta inmune adaptativa. Así, las manifestaciones clínicas de la infección se presentan frecuentemente a nivel del tracto respiratorio; sin embargo, también pueden involucrar otros sistemas como el hematopoyético. En el hemograma se observan recuentos celulares alterados, principalmente leucocitos y plaquetas. La linfopenia y neutrofilia se asocian con enfermedad severa y la trombocitopenia se presenta de manera heterogénea en la infección. Entre las complicaciones se encuentra la coagulación intravascular diseminada, producida cuando los monocitos y las células endoteliales son activadas por la liberación de citoquinas; esto genera daño endotelial, con la síntesis del factor tisular, secreción de factor tisular, activación plaquetaria y liberación del factor Von Willebrand, así como una condición hiperfibrinolítica especialmente en estadios tardíos de la infección. Las pruebas de laboratorio como el dímero D, los productos de degradación de la fibrina (PDF), tiempo de protrombina (TP), tiempo de tromboplastina parcial activado (TTPA), entre otras, son fundamentales para el diagnóstico, seguimiento y pronóstico de la enfermedad.

Severe SARS-CoV-2 Infection in Children With Suspected Acute Abdomen: A Case Series From a Tertiary Hospital in Spain

We describe 5 children with severe SARS-CoV-2 infection, hemodynamic instability and suspected acute abdomen. This form of the disease has not been previously documented. Four of the cases were confirmed SARS-CoV-2 infection and 1 probable. All of them were previously healthy and needed a pediatric critical care unit admission. The respiratory symptoms were not dominant or were absent. Also, fever was observed. Laboratory testing revealed lymphopenia and high levels of C-reactive protein and procalcitonin with D-dimer, ferritin and interleukin-6 usually elevated. Respiratory support and inotropic support were almost always necessary. In all of them, deterioration occurred on the day of admission.