Expression of SARS-CoV-2 entry factors in human oral tissue.

Yoshihiko Sawa,Tetsuro Ikebe,Hiroyuki Harada,Tatsuo Okui,Soichiro Ibaragi,Junro Yamashita

doi:10.1111/joa.13391

Abstract

The distribution of cells expressing SARS‐CoV‐2 entry factor angiotensin‐converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) in human oral tissues were tested. The investigation was conducted with normal flesh tissue and paraffin‐embedded specimens. The ACE2 and TMPRSS2 expression was detected with all subjects in the normal mucosa of the keratinized stratified squamous epithelia of the tongue and non‐keratinized stratified squamous epithelia of the lip and cheek. It was found that ACE2 is expressed in the cytoplasm and on the cell membrane mainly in the stratum granulosum of the epithelia while the TMPRSS2 is strongly expressed on the cell membrane mainly in the stratum granulosum and stratum spinosum, but not in the stratum basale. Antibodies’ reactions for ACE2 and TMPRSS2 were not observed in the nuclei or keratin layer. The expression of ACE2 and TMPRSS2 in the oral epithelia appears to be general, and the expression was also observed in the mucous and serous acini of the labial glands. The SARS‐CoV‐2 may transiently attach to the oral mucosa and the minor salivary glands which are present under all of the oral mucosa. The oral cavity can be considered an important organ for SARS‐CoV‐2 attachment and may provide a preventive medical avenue to guard against COVID‐19 by preventing saliva from scattering.

Highlights

Taste or olfactory disorders have been reported to occur in a third of patients in the early stages of COVID-19, the SARS-CoV-2 infections (Cevik et al, 2020; Zhang et al, 2020a, 2020b) (International Committee on Taxonomy of Viruses)
The SARS-CoV-2 initiates entry into human cells after the Spike protein (S) on the envelope binds to the SARSCoV-2 entry factor angiotensin-converting enzyme 2 (ACE2) which is a metallopeptidase on the cell membrane
The S1 binds to ACE2 and S2 is cleaved by another SARS-CoV-2 entry factor, a host cell-derived transmembrane serine protease 2 (TMPRSS2) and membrane fusion proceeds as a result of this

Summary

| INTRODUCTION

Taste or olfactory disorders have been reported to occur in a third of patients in the early stages of COVID-19, the SARS-CoV-2 infections (Cevik et al, 2020; Zhang et al, 2020a, 2020b) (International Committee on Taxonomy of Viruses). The SARS-CoV-2 initiates entry into human cells after the Spike protein (S) on the envelope binds to the SARSCoV-2 entry factor angiotensin-converting enzyme 2 (ACE2) which is a metallopeptidase on the cell membrane. The S1 binds to ACE2 and S2 is cleaved by another SARS-CoV-2 entry factor, a host cell-derived transmembrane serine protease 2 (TMPRSS2) and membrane fusion proceeds as a result of this. The virions are produced in the surface of the epithelium and spread into the surrounding tissue, and the viral genome remains as a plasmid in the basal cell nuclei. The present study aimed to provide details of the distribution of cells expressing the SARS-CoV-2 entry factors ACE2 and TMPRSS2 in the cytoplasm and cell membrane in oral tissue at immunohistochemical detection levels

| MATERIALS AND METHODS

| RESULTS

| DISCUSSION

Findings

| CONCLUSIONS