Abstract
Angiotensin-converting enzyme 2 (ACE2) has been identified as the functional receptor for Severe Acute Respiratory Syndrome—Coronavirus−2 (SARS-CoV-2). It has been identified in the human gastrointestinal tract (GIT), and SARS-CoV-2 has been isolated in human and animal fecal samples. The aim of the present study was to investigate the expression of ACE2 in the gastrointestinal tract of domestic (cat) and wild (tiger) felines. Samples of the pylorus, duodenum, and distal colon were collected from six cats and one tiger. The tissues were processed for immunofluorescence assay with an anti-human ACE2 antibody. Angiotensin-converting enzyme 2 was widely expressed in the gastrointestinal mucosa of the cats and the tiger. In both the species, ACE2-immunoreactivity (ACE2-IR) was expressed by the mucosal epithelial cells of the GIT and by the enteric neurons. In the cats, ACE2-IR was also expressed by the smooth muscle cells of the blood vessels and the tunica muscularis. The expression of the ACE2 receptor in enteric neurons may support the potential neurotropic properties of SARS-CoV-2. Although the evidence of ACE2-IR in the feline GIT does not necessarily indicate the possibility of viral replication and SARS-CoV-2 spread with stool, the findings in the present study could serve as an anatomical basis for additional studies considering the risk of the SARS-CoV-2 fecal-oral transmission between cats/felids, and between cats/felids and humans.
Highlights
IntroductionIn addition to its physiological roles, angiotensin-converting enzyme 2 (ACE2) has been identified as the functional receptor for Severe Acute Respiratory Syndrome—Coronavirus−2 (SARS-CoV-2), the RNA virus responsible for Covid-19 [2,3,4]
In the intestinal tract, angiotensin-converting enzyme 2 (ACE2) plays significant roles in amino acid homeostasis, innate immune responses, and intestinal microbiota regulation [1].In addition to its physiological roles, ACE2 has been identified as the functional receptor for Severe Acute Respiratory Syndrome—Coronavirus−2 (SARS-CoV-2), the RNA virus responsible for Covid-19 [2,3,4]
Since the necessary condition for the enteric multiplication of SARS-CoV-2 is represented by the expression of its election receptor on the host cells, the present study immunohistochemically investigated the localization of ACE2 in the gastrointestinal tract (GIT) of feline domestic and wild species
Summary
In addition to its physiological roles, ACE2 has been identified as the functional receptor for Severe Acute Respiratory Syndrome—Coronavirus−2 (SARS-CoV-2), the RNA virus responsible for Covid-19 [2,3,4]. The spike proteins of SARS-CoV-2 associate with the ACE2 of sensitive cells to mediate infection of their target cells, after which viral replication begins in the cytoplasm. The lungs seem to be the main target of SARS-CoV-2 in which the virus causes severe respiratory syndrome [5]. Viral nucleocapsid proteins have been found in the epithelial cells of the human stomach, duodenum, and rectum [5], and SARS-CoV-2 has been isolated from stool samples [8].
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