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Claire de Thoisy-Méchin

Press Relations

Tel. +33 (0)1 44 27 23 34

Email: claire.de_thoisy-mechin@upmc.fr

 

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Katherine Tyrka

International Press Relations

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Email: katherine.tyrka@upmc.fr

Bovine albumin involved in a kidney disease

A research team led by Hanna Debiec (Inserm) and Pierre Ronco (Inserm/UPMC and Tenon Hospital) has identified the bovine albumin, an alimentary antigen in cow milk, as the cause of a rare kidney disease among children under five. This disease is hard to treat and can lead to kidney insufficiency requiring dialysis or transplant. This discovery underlines the alimentary risk to young child who presented the antigen in the renal deposits that characterize the disease. The researchers’ work has been published in the June 2nd edition of The New England Journal of Medicine. Hanna Debiec is in charge of research at Inserm, and Pierre Ronco leads the research unit 702 “Reshaping and repairing kidney tissue” (Inserm/UPMC) and is head of the nephrology and dialysis department at Tenon Hospital (AP-HP).

Membranous glomerulonephritis is a rare disease which damages kidneys, the organs that filter our blood. This disease causes some antibodies (immunoglobulins) to collect in the glomerulus, which filters blood and produces urine. The capillary wall, and the cells that line it, make up the glomerular filter that is “attacked” by those deposits. In 85% of the cases, the disease causes are undetermined: it is called “idiopathic”.  

Hanna Debiec and Pierre Ronco have just identified bovine albumin as being an antigen involved in the formation of the disease among young child under 5. Bovine albumin comes from diet and more especially from natural cow milk or whose components are built-in in some industrial formulas.

To reach this conclusion, researchers studied 222 people including 50 patients affected by membranous glomerulonephritis. They showed the presence of undigested bovine albumin and the related antibodies in reaction to this protein in the serum of 11 affected patients, including four children under five.

“In an unexpected way, and only among children, this albumin carries positive electric charge which favors its deposit on the glomerulus capillary wall negatively charged,” explains Hanna Debiec, in charge of research at Inserm. “That’s why antibodies then come to attack the deposited albumin, which causes lesions”.

These are the first results to indentify an alimentary antigen in the membranous glomerulonephritis. The reasons why the bovine albumin is modified and absorbed without being digested remain obscure. Pierre Ronco suggests that “some methods of industrial preparations can make it partly resistant to the damage caused by the enzymes of the alimentary canal. Intestinal flora can also play an important part or also the patency of the intestinal barrier to proteins that is bigger among young child and may be increased by digestive infections.”

“We are continuing our research because other antigens from the environment could be involved among affected children or adults. Identifying those antigens would enable us to envisage ways to prevent or treat the disease, for example through an appropriate diet” underlines Pierre Ronco.

This research result has been protected by an application for patent by Inserm Transfert.

How does the membranous glomerulonephritis evolve?

The lesions of the glomerular filter caused by the antibodies’ deposits favor the entry of proteins with an abnormally large diameter into the urine, so this albumin has an important role: to control the distribution of liquids in the body. The reduced concentration of this protein in blood then leads to an accumulation of salt and water outside the cells, causing edemas. In advanced cases, glomerulus and the rest of renal tissues are overrun by a large fibrosis, which endangers kidney functioning. Membranous glomerulonephritis can eventually cause serious kidney failure, which at end stage requires dialysis or transplant. The disease recurs on the transplanted kidney in almost 40% of the cases. It is rarer among children than among adults, representing only 2% of the diseases identified by biopsy.

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14/06/11