title: Luminescent Immunoprecipitation System (LIPS) for Detection of Autoantibodies Against ATP4A and ATP4B Subunits of Gastric Proton Pump H+,K+-ATPase in Atrophic Body Gastritis Patients.
abstract: OBJECTIVE
  Circulating autoantibodies targeting the H+/K+-ATPase proton pump of gastric parietal cells are considered markers of autoimmune gastritis, whose diagnostic accuracy in atrophic body gastritis, the pathological lesion of autoimmune gastritis, remains unknown. This study aimed to assess autoantibodies against ATP4A and ATP4B subunits of parietal cells H+, K+-ATPase in atrophic body gastritis patients and controls.
  
  
  METHODS
  One-hundred and four cases with atrophic body gastritis and 205 controls were assessed for serological autoantibodies specific for ATP4A or ATP4B subunits using luminescent immunoprecipitation system (LIPS). Recombinant luciferase-reporter-fused-antigens were expressed by in vitro transcription-translation (ATP4A) or after transfection in Expi293F cells (ATP4B), incubated with test sera, and immune complexes recovered using protein-A-sepharose. LIPS assays were compared with a commercial enzyme immunoassay (EIA) for parietal cell autoantibodies.
  
  
  RESULTS
  ATP4A and ATP4B autoantibody titers were higher in cases compared to controls (P<0.0001). The area under the receiver-operating characteristic curve was 0.98 (95% CI 0.965-0.996) for ATP4A, and 0.99 (95% CI 0.979-1.000) for ATP4B, both higher as compared with that of EIA: 0.86 (95% CI 0.809-0.896), P<0.0001. Sensitivity-specificity were 100-89% for ATP4A and 100-90% for ATP4B assay. Compared with LIPS, EIA for parietal cell autoantibodies showed a lower sensitivity (72%, P<0.0001) at a similar specificity (92%, P=0.558).
  
  
  CONCLUSIONS
  Positivity to both, ATP4A and ATP4B autoantibodies is closely associated with atrophic body gastritis. Both assays had the highest sensitivity, at the cost of diagnostic accuracy (89 and 90% specificity), outperforming traditional EIA. Once validated, these LIPS assays should be valuable screening tools for detecting biomarkers of damaged atrophic oxyntic mucosa.
authors.affiliation: Clinical and Surgical Sciences and Translational Medicine, Sant'Andrea Hospital, School of Medicine, University Sapienza, Rome, Italy.
authors.forename: Edith
authors.initials: E
authors.lastname: Lahner
authors.affiliation: Diabetes Research Institute, IRCCS San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Brigatti
authors.affiliation: Diabetes Research Institute, IRCCS San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Marzinotto
authors.affiliation: Department of Internal Medicine and Medical Specialties, University Sapienza, Rome, Italy.
authors.forename: Marilia
authors.initials: M
authors.lastname: Carabotti
authors.affiliation: Clinical and Surgical Sciences and Translational Medicine, Sant'Andrea Hospital, School of Medicine, University Sapienza, Rome, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Scalese
authors.affiliation: Barbara Davis Center for Diabetes, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA.
authors.forename: Howard W
authors.initials: HW
authors.lastname: Davidson
authors.affiliation: Barbara Davis Center for Diabetes, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA.
authors.forename: Janet M
authors.initials: JM
authors.lastname: Wenzlau
authors.affiliation: Diabetes Research Institute, IRCCS San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Bosi
authors.affiliation: Diabetes Research Institute, IRCCS San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Piemonti
authors.affiliation: Clinical and Surgical Sciences and Translational Medicine, Sant'Andrea Hospital, School of Medicine, University Sapienza, Rome, Italy.
authors.forename: Bruno
authors.initials: B
authors.lastname: Annibale
authors.affiliation: Diabetes Research Institute, IRCCS San Raffaele Scientific Institute, Milan, Italy.|Department of Internal Medicine and Medical Specialties, University Sapienza, Rome, Italy.|Barbara Davis Center for Diabetes, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA.|Divisione di Genetica e Biologia Cellulare, IRCCS San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Vito
authors.initials: V
authors.lastname: Lampasona