title: Investigation of potential carbohydrate antigen targets for human and baboon antibodies.
abstract: BACKGROUND
  The continued presence of a primate antibody-mediated response to cells and organs from alpha1,3-galactosyltransferase gene-knockout (GTKO) pigs indicates that there may be antigens other than Gal alpha 1,3Gal (alpha Gal) against which primates have xenoreactive antibodies. Human and baboon sera were tested for reactivity against a panel of saccharides that might be potential antigen targets for natural anti-non-alpha Gal antibodies.
  
  
  METHODS
  Human sera (n = 16) and baboon sera (n = 15) of all ABO blood types were tested using an enzyme-linked immunoadsorbent assay for binding of IgM and IgG to a panel of synthetic polyacrylamide-linked saccharides (n = 15). Human sera were also tested after adsorption on alpha Gal immunoaffinity beads. Sera from healthy wild-type (WT, n = 6) and GTKO (n = 6) pigs and from baboons (n = 4) sensitized to GTKO pig organ or artery transplants (of blood type O) were also tested. Forssman antigen expression on baboon and pig tissues was investigated by immunohistochemistry.
  
  
  RESULTS
  Both human and baboon sera showed high IgM and IgG binding to alpha Gal saccharides, alpha-lactosamine, and Forssman disaccharide. Human sera also demonstrated modest binding to N-glycolylneuraminic acid (Neu5Gc). When human sera were adsorbed on alpha Gal oligosaccharides, there was a reduction in binding to alpha Gal and alpha-lactosamine, but not to Forssman. WT and GTKO pig sera showed high binding to Forssman, and GTKO pig sera showed high binding to alpha Gal saccharides. Baboon sera sensitized to GTKO pigs showed no significant increased binding to any specific saccharide. Staining for Forssman was negative on baboon and pig tissues.
  
  
  CONCLUSIONS
  We were unable to identify definitively any saccharides from the selected panel that may be targets for primate anti-non-alpha Gal antibodies. The high level of anti-Forssman antibodies in humans, baboons, and pigs, and the absence of Forssman expression on pig tissues, suggest that the Forssman antigen does not play a role in the primate immune response to pigs.
authors.affiliation: Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, PA 15261, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Yeh
authors.forename: Mohamed
authors.initials: M
authors.lastname: Ezzelarab
authors.forename: Nicolai
authors.initials: N
authors.lastname: Bovin
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Hara
authors.forename: Cassandra
authors.initials: C
authors.lastname: Long
authors.forename: Koji
authors.initials: K
authors.lastname: Tomiyama
authors.forename: Frank
authors.initials: F
authors.lastname: Sun
authors.forename: David
authors.initials: D
authors.lastname: Ayares
authors.forename: Michel
authors.initials: M
authors.lastname: Awwad
authors.forename: David K C
authors.initials: DK
authors.lastname: Cooper
mesh_terms: D000818:Animals; D000906:Antibodies / Q000097:blood / Q000276:immunology*; D000941:Antigens / Q000737:chemistry / Q000276:immunology*; D002241:Carbohydrates / Q000737:chemistry / Q000276:immunology*; D005577:Forssman Antigen / Q000276:immunology; D005700:Galactosyltransferases / Q000235:genetics* / Q000378:metabolism; D055785:Gene Knockdown Techniques; D006801:Humans; D051379:Mice; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism; D010215:Papio / Q000097:blood / Q000276:immunology*; D013154:Spleen / Q000166:cytology / Q000276:immunology; D013552:Swine; D014018:Tissue Distribution
chemical_list: D000906:Antibodies; D000941:Antigens; D002241:Carbohydrates; D009844:Oligosaccharides; D005577:Forssman Antigen; D005700:Galactosyltransferases; C047006:N-acetyllactosaminide alpha-1,3-galactosyltransferase