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University of Basel

20 June 2022

Neutralizing antibodies control bacterial infection

Microscopic image: red blood cells with bacteria inside
Bartonella bacteria (green) have invaded red blood cells (red). (Image: Biozentrum, University of Basel)

University of Basel researchers have discovered neutralizing antibodies which prevent bacterial infection or bring them to a halt. Only changes in the antibody docking sites on the bacterial cell surface enables the pathogen to evade this effective immune defense.

Bartonella are bacteria that are transmitted from blood-sucking insects to mammals, including humans. There they enter the red blood cells and cause various symptoms. An example of such a human infection with a worldwide distribution is the louse-borne five-day fever or trench fever. A life threatening tropical disease, known as Oroya fever, is also caused by these pathogens.

Professor Christoph Dehio’s team at the Biozentrum, together with the researchers led by Professor Daniel Pinschewer at the Department of Biomedicine, has now investigated the response of the immune system to a Bartonella infection in a mouse model. In their study, they discovered antibodies that stop the infection process solely by binding to the bacteria. “Such neutralizing antibodies have previously been described mostly in the context of viral infections,” explains Dr. Lena Siewert, first author of the study, which has been published in PNAS. “Until now, we didn’t know that neutralizing antibodies can also control the bacterial infection process – without the aid of phagocytes or other immune factors.”

Antibodies block bacteria

The research team has succeeded in artificially producing these antibodies and showing how they attack the bacterium. “The antibody binds to a specific protein, a so-called autotransporter. These are found on the bacterial cell surface and are vital for the bacteria,” says Siewert. The antibodies prevent the pathogens from attaching to and invading the erythrocytes – so stopping the infection. The blood-sucking insects no longer ingest any pathogens with their blood meal and so cannot transmit them to a new host.

Original publication

Lena K. Siewert, Aleksandr Korotaev, Jaroslaw Sedzicki, Katja Fromm, Daniel D. Pinschewer and Christoph Dehio
Identification of the Bartonella autotransporter CFA as protective antigen and hypervariable target of neutralizing antibodies in mice.
PNAS (2022), doi: 10.1073/pnas.2202059119

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