Subject(s)
Angiotensin-Converting Enzyme 2/metabolism , COVID-19/enzymology , Crohn Disease/enzymology , Gastrointestinal Microbiome , Ileum/enzymology , Inflammation Mediators/metabolism , Receptors, Virus/metabolism , SARS-CoV-2/enzymology , Angiotensin-Converting Enzyme 2/genetics , Animals , COVID-19/virology , Case-Control Studies , Colitis, Ulcerative/enzymology , Colitis, Ulcerative/immunology , Colitis, Ulcerative/microbiology , Crohn Disease/genetics , Crohn Disease/immunology , Crohn Disease/microbiology , Disease Models, Animal , Down-Regulation , Host-Pathogen Interactions , Humans , Ileum/immunology , Ileum/microbiology , Mice, Knockout , SARS-CoV-2/pathogenicity , STAT Transcription Factors/genetics , STAT Transcription Factors/metabolism , Serine Endopeptidases/metabolism , Signal Transduction , Toll-Like Receptors/genetics , Toll-Like Receptors/metabolismABSTRACT
The SARS-CoV-2 pandemic has so far claimed over three and a half million lives worldwide. Though the SARS-CoV-2 mediated disease COVID-19 has first been characterized by an infection of the upper airways and the lung, recent evidence suggests a complex disease including gastrointestinal symptoms. Even if a direct viral tropism of intestinal cells has recently been demonstrated, it remains unclear, whether gastrointestinal symptoms are caused by direct infection of the gastrointestinal tract by SARS-CoV-2 or whether they are a consequence of a systemic immune activation and subsequent modulation of the mucosal immune system. To better understand the cause of intestinal symptoms we analyzed biopsies of the small intestine from SARS-CoV-2 infected individuals. Applying qRT-PCR and immunohistochemistry, we detected SARS-CoV-2 RNA and nucleocapsid protein in duodenal mucosa. In addition, applying imaging mass cytometry and immunohistochemistry, we identified histomorphological changes of the epithelium, which were characterized by an accumulation of activated intraepithelial CD8+ T cells as well as epithelial apoptosis and subsequent regenerative proliferation in the small intestine of COVID-19 patients. In summary, our findings indicate that intraepithelial CD8+ T cells are activated upon infection of intestinal epithelial cells with SARS-CoV-2, providing one possible explanation for gastrointestinal symptoms associated with COVID-19.
Subject(s)
CD8-Positive T-Lymphocytes/immunology , COVID-19/immunology , Duodenum/immunology , Immunity, Mucosal , Intestinal Diseases/immunology , Intestinal Mucosa/immunology , Intraepithelial Lymphocytes/immunology , Lymphocyte Activation , SARS-CoV-2/immunology , Adult , Aged , Animals , Apoptosis , CD8-Positive T-Lymphocytes/virology , COVID-19/pathology , COVID-19/virology , Case-Control Studies , Cell Proliferation , Chlorocebus aethiops , Duodenum/pathology , Duodenum/virology , Female , Host-Pathogen Interactions , Humans , Intestinal Diseases/pathology , Intestinal Diseases/virology , Intestinal Mucosa/pathology , Intestinal Mucosa/virology , Intraepithelial Lymphocytes/virology , Male , Re-Epithelialization , SARS-CoV-2/pathogenicity , Vero Cells , Viral LoadABSTRACT
The newly identified severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19, a pandemic respiratory disease. Moreover, thromboembolic events throughout the body, including in the CNS, have been described. Given the neurological symptoms observed in a large majority of individuals with COVID-19, SARS-CoV-2 penetrance of the CNS is likely. By various means, we demonstrate the presence of SARS-CoV-2 RNA and protein in anatomically distinct regions of the nasopharynx and brain. Furthermore, we describe the morphological changes associated with infection such as thromboembolic ischemic infarction of the CNS and present evidence of SARS-CoV-2 neurotropism. SARS-CoV-2 can enter the nervous system by crossing the neural-mucosal interface in olfactory mucosa, exploiting the close vicinity of olfactory mucosal, endothelial and nervous tissue, including delicate olfactory and sensory nerve endings. Subsequently, SARS-CoV-2 appears to follow neuroanatomical structures, penetrating defined neuroanatomical areas including the primary respiratory and cardiovascular control center in the medulla oblongata.