Comparative Evaluation of Nasal and Small Intestine Expression of ACE2, TMPRSS2 and ACE1 and in Children and in Adults

Importance: Clinical severity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection seems to be lower in children compared to that in adults. Defining the pathophysiological mechanisms of such disease patterns maybe relevant for development of effective public health strategies. It has been hypothesised that the lower severity of SARS-CoV-2 infection in children could be due to the differential expression of angiotensin-converting enzyme 2 (ACE2), which serves as a virus receptor. Objective: To evaluate the expression of ACE2, ACE1, and TMPRSS2 genes at the level of the two most relevant entry sites for SARS-CoV-2, the upper respiratory tract and small intestine, in healthy children and adult subjects. Design, Setting, and Participants: This prospective study included healthy individuals of both sexes, aged 1-10 years in the paediatric population (n=30) and 20-80 years in the adult population (n=30). The participants were consecutively evaluated at two tertiary centres for paediatrics, gastroenterology, and otolaryngology. Main Measures: Expression of ACE2, ACE1, and TMPRSS2 genes in samples collected from the upper respiratory tract and small intestine. Results: We found no difference in ACE2, ACE1, and TMPRSS2 expression in the nasal epithelium between children and adult subjects. ACE2 expression was more abundant in the small intestine of children compared to that in adults. ACE1 expression was higher in the small intestine of adults compared to that in children. Intestinal TMPRSS2 expression was similar in the two study populations. Conclusions and Relevance: The general lower severity of SARS-CoV-2 infection in children does not seem to be related to a lower expression of ACE2 and/or TMPRSS2 in the respiratory tract or in the gastrointestinal tract. Other co-factors may confer protection against SARS-CoV-2 in children. The exploration of such factors is of pivotal importance for development of innovative protective strategies against SARS-CoV-2. Funding Statement: This work was supported in part by a grant of Regione Campania POR FESR 2014/2020, Task Force Covid-19 DGR 140 – 17 March 2020. Declaration of Interests: The authors have no other conflict of interests that are directly relevant to the content of this manuscript, which remains their sole responsibility. Ethics Approval Statement: The study was approved by the Ethics Committee of the University Federico II of Naples, Italy. Written informed consent was obtained from the adult participants and from the parents/tutors of minors.