Researchers have found that SARS-CoV-2 protein deposits contribute to an autoimmune condition where the body attacks the small filtering units in the kidney.

The SARS-CoV-2 virus, responsible for the deadly Covid-19 pandemic, is increasing kidney injury by storing proteins, according to a study. Researchers from Capital Medical University and Chifeng University in China found that SARS-CoV-2 protein deposits in the kidney are contributing to the “incidence and recurrence of membranous nephropathy (MN)” – an autoimmune condition where the body attacks the tiny filtering units. (glomeruli) in the kidney.

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Effects of SARS-CoV-2 on renal function

The study included 38 patients with biopsy-proven MN who developed new-onset proteinuria—elevated protein in the urine—post-Covid—and 100 patients with primary MN who were diagnosed before the epidemic as controls. “Thirteen of 38 patients tested positive for SARS-CoV-2 nucleocapsid protein. “Compared to control patients, clinical manifestations were more severe in patients after Covid infection,” the team said in a paper published in Kidney International Reports.

Those with positive SARS-CoV-2 protein levels had a “higher incidence of nephrotic syndrome, lower serum albumin levels, and greater severity of renal interstitial fibrosis than patients with negative SARS-CoV-2” protein levels. “Our study suggests that SARS-CoV-2 infection can lead to accumulation of viral proteins under epithelial cells and podocyte (kidney cell) injury,” the researchers said.

MN is the most common pathological form of adult nephrotic syndrome – a kidney disorder that causes the body to excrete excess protein in the urine. It is characterized by the deposition of immune complexes within glomerular epithelial cells, including specific antigens, IgG and complement membrane attack complex (MAC). Approximately 70 percent of MN are considered primary, while the remaining 30 percent are secondary to various etiologies, with infections such as hepatitis virus being an important secondary cause.

While previous studies have shown SARS-CoV-2 to be predominantly present in renal tubular epithelial cells of Covid patients with kidney injury, the new study, for the first time, found deposits of SARS-CoV-2 nucleocapsid protein along the glomerular basement membrane.

Yet the researchers noted that “the relationship between SARS-CoV-2 protein accumulation and the pathogenesis of MN remains unclear”. He called for further enquiry.

(IANS)