Antibody discovery paves the way for new treatments against group A streptococcal infections – ScienceDaily

Researchers at Lund University in Sweden have discovered a rare form of antibody binding that leads to an effective immune response against bacteria, as well as an antibody that has the potential to protect against Strep A infection. The discovery may explain why so many Group A strep vaccines fail.

The results were published in: EMBO Molecular Medicine.

Group A streptococci have several ways to evade the body’s immune system, and when they infect us, they can cause both common throat infections (strep throat), scarlet fever, sepsis, swine pox and skin infections. So far, antibiotics have worked against these bacteria, but if they become resistant they will pose a major public health threat.

One strategy used by the scientific community to find new ways to fight bacterial infections is to create target-seeking antibodies. First, the antibodies produced by the body’s immune system in the event of an infection are mapped, and then their effects on the immune system are examined. In this way, antibodies can be identified that can be used both for prophylactic therapy and for therapy during an ongoing infection. However, this is a challenging process and many attempts to develop antibody-based therapies against Strep A have failed.

The current study shows that antibodies interact unexpectedly with group A streptococci and, more specifically, how they bind to the M protein, which is probably the most important bacterial protein on the cell surface.

“We found that this happens in a way that has never been described before. Normally, an antibody binds via one of the two Y arms to its target protein at a single site, whichever of the two arms is used for binding. But what we’ve seen – and this is very important information – is that the two Y arms are used for binding. your arm, two “Different locations of the same target protein,” explains Pontus Nordenfelt, one of the study’s authors.

This means that two arms of the same antibody can bind to two different sites on a target protein. It turns out that precisely this type of attachment is necessary for effective protection, and researchers believe it could explain why so many vaccine attempts fail, possibly because it’s rare. There may also be a reason why bacteria manage to evade the immune system.

It has long been known that the M protein of streptococcal bacteria is of great importance in how diseases occur and develop in the body. Finding an antibody that binds to this protein and thus signals it to the immune system can prevent bacteria from infecting body cells. As we know that the human body can fight infection, such antibodies exist but they are hard to find.

Therefore, the researchers focused on examining antibodies in patients who recovered from group A streptococcal infection. They were able to identify three so-called monoclonal antibodies from a patient who had recovered from strep A infection. Monoclonal antibodies are identical copies of each other and in this case target a single protein (M protein) of group A streptococci. The researchers then investigated in animal studies whether it was possible to use antibodies to boost the immune system in the fight against group A streptococci. It turns out that the antibody with the newly discovered binding mechanism produces a strong immune response against the bacteria. The researchers have now applied for a patent based on the findings in the article and will continue to study the antibody.

“This opens up possibilities where previous vaccine attempts have failed and means that the monoclonal antibody we used has the potential to protect against infection,” said Wael Bahnan, one of the authors behind the study.

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materials provided by Lund University. Note: Content can be edited for style and length.

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