title: An ELISA system to detect anti-factor VIII antibodies without interference by lupus anticoagulants. Preliminary data in hemophilia A patients.
abstract: OBJECTIVE
  Difficulties in identifying the coexistence of neutralizing anti-factor VIII antibodies (anti-fVIII) and lupus anticoagulant (LA) are mainly due to the interference of LA on anti-fVIII assays. Our aim was to reveal the presence of anti-fVIII using a system that is not affected by LA.
  
  
  METHODS
  We developed an enzyme-linked immunosorbent assay (ELISA) method that uses phospholipid-free recombinant factor VIII as the antigen. A monoclonal anti-fVIII was tested as a positive control, excluding non-specific binding by using two unrelated monoclonal antibodies. The ELISA was performed on hemophilic plasmas with anti-fVIII and negative LA (n=12) or without inhibitors (n=12). Two hemophilic plasmas with LA and presumably anti-fVIII were also assayed. Positive LA (n=12) and normal (n=10) plasmas were tested as negative controls.
  
  
  RESULTS
  All (12/12) plasmas with anti-fVIII and 5/12 hemophilic plasmas without inhibitors were positive; LA and normal plasma controls were negative.
  
  
  CONCLUSIONS
  Results presented here show that LA does not interfere with the anti-fVIII ELISA: However, the assay detects both neutralizing and non-neutralizing anti-fVIII antibodies, therefore a neutralizing effect must be confirmed through functional tests.
authors.affiliation: Instituto de Investigaciones Hematológicas "Mariano R. Castex", Academia Nacional de Medicina, Pacheco de Melo 3081, 1425 Buenos Aires, Argentina. blanco@connmed.com.ar
authors.forename: A N
authors.initials: AN
authors.lastname: Blanco
authors.forename: A A
authors.initials: AA
authors.lastname: Peirano
authors.forename: S H
authors.initials: SH
authors.lastname: Grosso
authors.forename: L C
authors.initials: LC
authors.lastname: Gennari
authors.forename: R P
authors.initials: RP
authors.lastname: Bianco
authors.forename: M A
authors.initials: MA
authors.lastname: Lazzari
mesh_terms: D000906:Antibodies / Q000097:blood / Q000276:immunology*; D003429:Cross Reactions; D004797:Enzyme-Linked Immunosorbent Assay; D005169:Factor VIII / Q000276:immunology*; D006467:Hemophilia A / Q000097:blood / Q000276:immunology*; D006801:Humans; D016682:Lupus Coagulation Inhibitor / Q000276:immunology; D011994:Recombinant Proteins / Q000276:immunology; D012680:Sensitivity and Specificity
chemical_list: D000906:Antibodies; D016682:Lupus Coagulation Inhibitor; D011994:Recombinant Proteins; D005169:Factor VIII