NASAL EXPRESSION OF ANIOTENSIN-CONVERTING ENZYME 2 (ACE2) IN CHILDREN AND ADULTS WITH COVID-19

Abstract

"Emerging evidence suggests that the lower expression of SARS-CoV-2 entry factor angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) in the nasal epithelium of children may contribute to lower incidence of COVID-19 in this age group compared to adults, yet no direct evidence is available for this hypothesis. In this study, we compared the transcript levels of ACE2 and TMPRSS2 in nasopharyngeal swabs (NPS) of children and their companion adults within COVID-19 exposed-families (n=207), to assess their association with infection status. Additionally, NPS specimens from COVID-19 positive and symptomatic children (n=24) and adults (n=10) were assessed for associations of ACE2 and TMPRSS2 expression with patients' clinical and laboratory outcomes. In the paired dataset, the expression of both genes was higher among adults (n=115) compared to children (n=92), but the expression was not significantly different between COVID-19 positive and negative patients of all ages or within the same age group. Within the same families, the expression of ACE2 and TMPRSS2 was higher in COVID-19 positive adults when compared to COVID-19 negative children (p=0.0002 and 0.0061, for ACE2 and TMPRSS2, respectively, by Wilcoxon Signed-Rank test, n=94), but the expression of these genes was not significantly different between COVID-19 positive adults and children or between COVID-19 negative adults and positive children. Consistently, the expression of both genes was positively associated with SARS-CoV-2 positivity in this subgroup only (OR: 1.146, 95%CI: 1.038-1.284, p=0.0114 for ACE2 and OR: 1.123, 95%CI: 1.012-1.254, p=0.0334 for TMPRSS2). These findings suggest that children with lower expression of nasal ACE2 and TMPRSS2 are likely to remain COVID-19 negative despite being exposed to a COVID-19 positive family member. Using data from all specimens collected in this study and by grouping them as negative, asymptomatic and symptomatic for COVID-19, no significant association was found between the expression of ACE2 and TMPRSS2 genes and clinical symptoms or laboratory findings."