Heterogenicity of Tissue Distribution Recognized by A panel of Monoclonal Antibodies

Abstract

Abstract ACE2 (Angiotensin Converting Enzyme 2) is the main viral entry point for SARS-CoV and SARS-CoV-2. Human ACE2 is widely expressed on different organs but if virus attached all the organs that highly expressed ACE2 is not fully studied. Most recent finding showed that a novel short isoform of ACE2 expressed in the airway epithelium is substantially upregulated in response to interferon stimulation, but not SARS-CoV-2 infection due to this short isoform lacking SARS-CoV-2 spike high-affinity binding sites. This arouses our interest in whether ACE2 has more isoforms expressed in different tissues that directly affect different organs response to virus infection. To support understanding ACE2 expression in response to viral infection, we generated human ACE2 monoclonal antibody by immunizing rat with recombinant human ACE2 protein covering extracellular domain (Gln18-Ser740). We found that there is discrepancy in different clones on different tissues. After three rounds subcloning, four clones have been selected based on chromosomally stable IgG producing hybridoma cells. Our data showed that all four clones showed equivalent signals on ACE2 transfectants but staining signals varied on tubules of kidney and seminiferous tubules and leyding cells on testis, two clones showed medium level staining signals on intestine and colon, but only one clone showed positive staining signals on spleen vascular and red pulp sinus endothelium. In addition, different neutralization potency and Western blot detection performance were observed among the collections of clones. Our data indicated that different clones might recognize different epitopes of ACE2 and indirectly suggested that ACE2 might have different isoforms in different tissues.