Micro-organisms trick the immune system by evading an attack

It is a well-known fact that microbes have great talent to change their surface structure, which is why HIV and malaria vaccines are difficult to develop, and new influenza vaccines have to be developed year after year. In an article published in Cell Host & Microb, Professor Gunnar Lindahl from Lund University and his research group demonstrated that microbes could keep the immune system from triggering a response in the person attacked.

He says, “If we get a serious streptococcus infection, we want our immune defences to create antibodies aimed at certain parts of the micro-organisms’ surface protein. But that mechanism does not work particularly well, which is a disadvantage for us and an advantage for the bacteria.”

Gunnar Lindahl’s group selected group A streptococci for their study. These are a very important group of disease-causing pathogens that are responsible for a variety of illnesses, including ordinary tonsillitis, very serious autoimmune diseases, and fatal toxic shock syndrome.

The researchers studied the bacteria’s surface protein called the M protein, also referred to as the “hypervariable region,” which has the ability to vary extensively in order to evade an immune attack. Study findings demonstrated that a certain pertinent part of the protein was not only variable but also prevented an immune system attack.

Gunnar Lindahl says, “This may be what actually constitutes the micro-organisms’ primary weapon: that they avoid antagonizing the immune system. In the case of a long-lasting infection, the immune system does indeed start to produce antibodies eventually, but by then the micro-organisms can have established a firm footing.”

Scientific research conducted around the 50s had already documented the ability of microbes to keep the immune system from launching an attack. However, this ability was eclipsed by other self-protective mechanisms such as their proficiency to vary the surface structure. Since an immense variation to evade an immune attack was apparently in response to a strong antibody pressure, researchers did not pay attention to whether there actually was any strong antibody pressure.

Although the results of this study make up for a small part of research in molecular biology, it has far-reaching consequences on the development of new vaccines. In addition to taking into account the ability of variation in bacteria, viruses, and other microbes, vaccine developers must also mull over their aptitude to avoid triggering an immune system attack.

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