TY - JOUR
T1 - Serine protease HTRA1 as a novel target antigen in primary membranous nephropathy
AU - Al-Rabadi, Laith Farah
AU - Caza, Tiffany
AU - Trivin-Avillach, Claire
AU - Rodan, Aylin R.
AU - Andeen, Nicole
AU - Hayashi, Norifumi
AU - Williams, Brandi
AU - Revelo, Monica P.
AU - Clayton, Fred
AU - Abraham, Jo
AU - Lin, Edwin
AU - Liou, Willisa
AU - Zou, Chang Jiang
AU - Ramkumar, Nirupama
AU - Cummins, Tim
AU - Wilkey, Daniel W.
AU - Kawalit, Issa
AU - Herzog, Christian
AU - Storey, Aaron
AU - Edmondson, Rick
AU - Sjoberg, Ronald
AU - Yang, Tianxin
AU - Chien, Jeremy
AU - Merchant, Michael
AU - Arthur, John
AU - Klein, Jon
AU - Larsen, Chris
AU - Beck, Laurence H.
N1 - Funding Information:
phenotype of HTRA1-associated MN. This is supported by biopsy specimen features showing predominance of IgG4, absence of C1q or a full-house pattern of staining by immunofluorescence, and a lack of subendothelial deposits or endothelial tubuloreticular inclusions by electron microscopy. The peripheral capillary wall and subepithelial pattern of HTRA1 staining is more suggestive of a mechanism of immune complex formation related to shedding or secretion from the podocyte, similar to PLA2Rand THSD7A-associated MN,
Publisher Copyright:
© 2021 by the American Society of Nephrology
PY - 2021/7
Y1 - 2021/7
N2 - Background Identification of target antigens PLA2R, THSD7A, NELL1, or Semaphorin-3B can explain the majority of cases of primary membranous nephropathy (MN). However, target antigens remain unidentified in 15%-20% of patients. Methods A multipronged approach, using traditional and modern technologies, converged on a novel target antigen, and capitalized on the temporal variation in autoantibody titer for biomarker discovery. Immunoblotting of human glomerular proteins followed by differential immunoprecipitation and mass spectrometric analysis was complemented by laser-capture microdissection followed by mass spectrometry, elution of immune complexes from renal biopsy specimen tissue, and autoimmune profiling on a protein fragment microarray. Results These approaches identified serine protease HTRA1 as a novel podocyte antigen in a subset of patients with primary MN. Sera from two patients reacted by immunoblotting with a 51-kD protein within glomerular extract and with recombinant human HTRA1, under reducing and nonreducing conditions. Longitudinal serum samples from these patients seemed to correlate with clinical disease activity. As in PLA2R- and THSD7A- associated MN, anti-HTRA1 antibodies were predominantly IgG4, suggesting a primary etiology. Analysis of sera collected during active disease versus remission on protein fragment microarrays detected significantly higher titers of anti-HTRA1 antibody in active disease. HTRA1 was specifically detected within immune deposits of HTRA1-associated MN in 14 patients identified among three cohorts. Screening of 118 “quadruple-negative” (PLA2R-, THSD7A-, NELL1-, EXT2-negative) patients in a large repository of MN biopsy specimens revealed a prevalence of 4.2%. Conclusions Conventional and more modern techniques converged to identify serine protease HTRA1 as a target antigen in MN.
AB - Background Identification of target antigens PLA2R, THSD7A, NELL1, or Semaphorin-3B can explain the majority of cases of primary membranous nephropathy (MN). However, target antigens remain unidentified in 15%-20% of patients. Methods A multipronged approach, using traditional and modern technologies, converged on a novel target antigen, and capitalized on the temporal variation in autoantibody titer for biomarker discovery. Immunoblotting of human glomerular proteins followed by differential immunoprecipitation and mass spectrometric analysis was complemented by laser-capture microdissection followed by mass spectrometry, elution of immune complexes from renal biopsy specimen tissue, and autoimmune profiling on a protein fragment microarray. Results These approaches identified serine protease HTRA1 as a novel podocyte antigen in a subset of patients with primary MN. Sera from two patients reacted by immunoblotting with a 51-kD protein within glomerular extract and with recombinant human HTRA1, under reducing and nonreducing conditions. Longitudinal serum samples from these patients seemed to correlate with clinical disease activity. As in PLA2R- and THSD7A- associated MN, anti-HTRA1 antibodies were predominantly IgG4, suggesting a primary etiology. Analysis of sera collected during active disease versus remission on protein fragment microarrays detected significantly higher titers of anti-HTRA1 antibody in active disease. HTRA1 was specifically detected within immune deposits of HTRA1-associated MN in 14 patients identified among three cohorts. Screening of 118 “quadruple-negative” (PLA2R-, THSD7A-, NELL1-, EXT2-negative) patients in a large repository of MN biopsy specimens revealed a prevalence of 4.2%. Conclusions Conventional and more modern techniques converged to identify serine protease HTRA1 as a target antigen in MN.
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U2 - 10.1681/ASN.2020101395
DO - 10.1681/ASN.2020101395
M3 - Article
C2 - 33952630
AN - SCOPUS:85114063993
SN - 1046-6673
VL - 32
SP - 1666
EP - 1681
JO - Journal of the American Society of Nephrology
JF - Journal of the American Society of Nephrology
IS - 7
ER -