Abstract: FR-OR055
Novel Quantitative Immunoassays for Anti-HTRA1 Antibodies in Membranous Nephropathy
Session Information
- Pathology: Novel Mechanisms and Modalities
November 07, 2025 | Location: Room 371A, Convention Center
Abstract Time: 04:30 PM - 04:40 PM
Category: Pathology and Lab Medicine
- 1800 Pathology and Lab Medicine
Authors
- Al-Rabadi, Laith, University of Utah Health, Salt Lake City, Utah, United States
- Arivett, Brock A., Meharry Medical College, Nashville, Tennessee, United States
- Ferru, Nicoletta, Universitatsklinikum Hamburg-Eppendorf, Hamburg, HH, Germany
- Caza, Tiffany, Arkana Laboratories, Little Rock, Arkansas, United States
- Beck, Laurence H., Boston University, Boston, Massachusetts, United States
- Hoxha, Elion, Universitatsklinikum Hamburg-Eppendorf, Hamburg, HH, Germany
- Borza, Dorin-Bogdan, Meharry Medical College, Nashville, Tennessee, United States
Background
We have previously identified serine protease HTRA1 as an antigen in 1-2% of patients with primary membranous nephropathy (MN). Anti-HTRA1 antibodies are currently detected within patient sera by Western blotting, which is not suitable for clinical use. We aimed to develop a robust reproducible assay for the quantitative measurement of anti-HTRA1 antibody titers.
Methods
Longitudinal serum samples from a subset of patients with confirmed diagnosis of HTRA1-associated MN by biopsy and Western blotting were used to develop and optimize an ELISA immunoassay using recombinant HTRA1 or the inactive HTRA1 S328A mutant. Screening for additional cases was performed in 59 MN patients found to be anti-PLA2R negative among 148 MN patients from the CureGN cohort. The immunoassay was validated in a cohort of 231 MN patients negative for anti-PLA2R and anti-THSD7A antibodies from the University of Hamburg.
Results
Similar results were obtained using wild type HTRA1 and the S328A mutated protein. Anti-HTRA1 antibodies were predominantly (but not exclusive) of IgG4 subclass. Assaying for IgG4 was more specific than pan-IgG in our ELISA. In longitudinal samples, anti-HTRA1 titers were found to correlate with proteinuria, decreasing with remission and increasing during recurrence. Anti-HTRA1 antibodies were detected in 3 out of 59 (5.1%) anti-PLA2R-negative MN patients from the CureGN cohort. Results of anti-HTRA1 ELISA closely correlated with signal strength from immunoblotting analyses. Seropositivity by ELISA was further corroborated using “Simple Western” capillary electrophoresis. In the Hamburg cohort, five out of 231 MN patients found positive for HTRA1 on Western blot and biopsy were also found positive by ELISA.
Conclusion
Both ELISA and capillary electrophoresis immunoassays afford rapid, reproducible and accurate measurement of circulating antibody levels in patients with HTRA1-associated MN, which could be used to monitor disease activity and response to treatment.
Funding
- NIDDK Support