#1360 SARS-COV-2 protein in renal tissue enhanced activation of complement system in MN patients with COVID-19 infection
Authors: Wang Guoqin , Yang Lei , Guo Weiyi , Xu Xiaoyi , Sun Lijun , Dong Hongrui , Zhao Xiaoyi , Cheng Hong 
Published: May 2024

Abstract

Background and Aims
Membranous nephropathy (MN) is the most common cause of nephrotic syndrome in adults. Complement plays an important role in the pathogenesis of MN. COVID-19 infection has been reported to be associated with the occurrence and recurrence of MN. Only few kidney biopsies from COVID-19 patients demonstrate the presence of SARS-CoV-2 in the tissue. The clinical and pathological characteristics and complement system activation of patients with SARS-COV2 in renal tissue are unclear, needing to further study.

Method
From December 2022 to June 2023, patients with renal biopsy-proven MN at Beijing Anzhen hospital who had experienced COVID-19 infection before proteinuria onset and renal biopsy were enrolled. One hundred patients with primary MN diagnosed from December 2018 to June 2019 (with no COVID-19) were enrolled as control. Patient medical records were reviewed for clinical and pathological data. We performed immunofluorescence and in situ hybridization assays for detection of the SARS-COV2. Glomerular staining for factor H, FHR-5 and MAC were detected by immunohistochemical. Serum C5b-9 were detected by enzyme-linked immunosorbent assay. Clinicopathological and immunological features between MN patients with and without SARS-COV2 infection were analyzed.

Results
A total of 38 MN patients was proteinuria onset after COVID-19 infection, including 11 patients had SARS-COV protein positive staining along capillary loops in glomerular deposits or in cytoplasm of tubular epithelial cells. The immunofluorescence result shows strong colocalization of SARS-COV2 and IgG, which suggests that SARS-COV protein participated in the formation of immune complex. Compared with primary MN patients, the serum albumin level of 38 MN patients with COVID-19 infection were lower (p = 0.011). However, the clinical manifestations of 11 MN patients with SARS-COV2 renal positive staining were obviously serous. Compared with primary MN patients, urinary protein and serum creatine levels significantly increased (p = 0.027 and p = 0.005), while serum albumin levels decreased (p = 0.014) and the proportion of nephrotic syndrome (p = 0.037) was higher. There was no significant difference in pathological manifestations between MN patients with or without COVID-19 infection. In follow-up, the proportion of patients with urinary protein decreased greater than 50% in MN patients with COVID-19 infection was lower than that in primary MN patients. of urinary protein level Serum level of complement C3 (p = 0.007) and MAC (P = 0.001) in MN patients with COVID-19 infection was significantly higher than that of primary MN patients, especially MN patients with renal tissue positive staining of SARS-COV2 protein (p = 0.002 and p = 0.007). In 38 MN patients with COVID-19 infection, compared with patients with renal tissue negative for SARS-COV2 protein, patients with renal tissue positive for SARS-COV2 protein presented with stronger intensity of MAC deposition (p = 0.023) and factor H deposition (p = 0.002).

Conclusion
The clinical manifestation of MN patients who was onset after COVID-19 infection with renal tissue positive for SARS-COV2 protein were not only significantly worse than those of primary MN patients, but also worse than patients without tissue SARS-COV2 positive MN patients. We speculate that the reason is the enhanced activation of the complement system in renal tissue.