Biomarkers of severity and prognosis in COVID-19 of children and adolescents with comorbidities: viral load in blood samples, saliva and feces, expressed and soluble ACE2, apoptosis via MCL-1

• Grant number: 21/04280-4
• Support Opportunities: Regular Research Grants
• Duration: November 01, 2021 - October 31, 2023
• Field of knowledge: Health Sciences - Medicine - Maternal and Child Health
• Principal Investigator: Thelma Suely Okay
• Grantee: Thelma Suely Okay
• Host Institution: Faculdade de Medicina (FM). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated researchers: Heloisa Helena de Sousa Marques ; Maria Fernanda Bádue Pereira

Abstract

Since the beginning of the COVID-19 pandemic, the fact that children and adolescents have less severe disease has been noteworthy, although infections with high viral load have been described in respiratory secretions of asymptomatic children and there are no studies on the presence of the virus in blood samples (RNAemia), in this age group. SARS-CoV-2 has a high affinity with the angiotensin-converting enzyme 2 receptor (ACE2) present in epithelial cells of the lungs, intestines, kidneys, heart, brain and blood vessel epithelia. Children appear to have lower ACE2 expression in epithelial cells, according to studies on cardiovascular and endocrine diseases, offering less opportunities for SARS-COV-2 to bind and penetrate human host cells, possibly constituting one of the mechanisms involved in their lower severity of COVID-19. In the present proposal, we intend to investigate the expression of ACE2 in fecal and salivary samples from children with COVID-19, presenting with or without comorbidities, since these biological materials contain desquamated epithelial cells, avoiding the performance of mouth or intestines biopsies. In addition, the same studies have shown that children have higher levels of soluble ACE2 in circulation than adults, promoting competition between the circulating ACE2, which keeps its binding site to SARS-CoV-2 active, leading to the binding of part of the viruses to the soluble ACE2, resulting in less viral particles entering new host cells, constituting another possible mechanism to explain the lower severity of COVID-19 in children. Another point that deserves investigation in COVID-19 is the programmed cell death (apoptosis), more specifically the pathway regulated by MCL-1 (Myeloid Cell Leukemia-1). In interaction studies between SARS-CoV-2 and the human host, the human MCL-1 protein was the factor that underwent the greatest positive regulation after contact with SARS-CoV-2. MCL-1 is encoded by the mcl-1 gene, which in turn undergoes strong transcriptional regulation (alternative splicing), giving rise to the long isoform (MCL-1L), with anti-apoptotic properties, that predominates in physiological situations. However, during inflammation/infection/COVID-19, the alternative splicing gives rise to two short isoforms, MCL-1S short and MCL-1ES extra-short, which are pro-apoptotic and bind specifically to the long isoform, inactivating it and favoring apoptosis. To control our expression experiments, we intend to study the translation of the mcl-1 gene through the serum concentrations of MCL-1. Therefore, the present research intends to evaluate the following parameters in both groups (with or without COVID, then divided into subgroups with or without comorbidities): a) Evaluate the viral load of SARS-CoV-2 in blood samples (RNAemia), saliva and feces of children and adolescents b) Evaluate the expression of the ACE2 receptor in epithelial cells of saliva and feces; c) Determine the circulating levels of soluble ACE2; d) Evaluate the expression of the three MCL-1 isoforms in blood samples; e) Determine the serum concentrations of MCL-1. The results of the laboratory parameters of the two groups with or without COVID-19 (presenting or not with comorbidities) will be compared, and those with statistically significant differences will be included in the logistic regression analysis as independent variables, with the outcome of infections as the dependent variable (recovery/death or severity of COVID-19- mild, moderate or severe). (AU)