The bacterium Clostridium botulinum produces botulinum toxin, known to be one of the most poisonous toxins for humans. Despite this, it was exploited by research at Harvard, who developed both cosmetic and medical applications.
Researchers from Harvard University in conjunction with the Broad Institute in the United States, experimented with botulinum toxin, developing it for the purpose of obtaining new protease enzymes. Which have the function of cutting proteins for their activation or deactivation. These enzymes have a high selectivity to help regulate growth hormones and anti-inflammatory activity, that is, neuroregeneration actions.
During the development of the investigation, the team obtained the reprogramming of the protease enzymes. This consisted of cutting new protein targets different from the native ones of the initial proteases. Similarly, they began to work on what the team called a “classic challenge in biology”; this consists of designing treatments where the purpose is to enter a cell.
Thanks to the difference in size with the rest of the proteins, botulinum toxin proteases can reach neurons more easily. This feature provides them with a broader scope, giving them a greater possibility to be used in various types of therapies. With this, “customized” proteases can be developed with specific instructions to know which and which protein to cut.
“Such an ability could make ‘proteome editing’ feasible, complementing the recent development of genome editing technologies,” said Harvard researcher David Liu. This represents a window of opportunity for the treatment of various conditions such as neurological damage. This research opens a possibility of protease therapy, proteins help increase the body’s ability to heal nerve damage through a temporary or one-shot treatment.
Unlike antibodies whose targets are specific, proteases have the ability to bind to any protein, and do more than just attack its target, even reactivate inactive proteins. “Despite these important characteristics, proteases have not been widely adopted as therapy, mainly due to the lack of technology to generate proteases that cleave protein targets of choice,” Liu commented.
Using a technology called Phage Assisted Continuous Evolution (PACE). Using this technology, dozens of protein generations can be developed per day with minimal human intervention. Using PACE, early proteases (called promiscuous) were taught to stop cutting off certain targets and become more selective.
By obtaining the first result, the team escalated to the next challenge, teaching a protease to recognize only a completely new target. With PACE, the inhibition of the natural activity of the protease was achieved to give way to a new specificity in them.
Despite the information, more work is necessary before becoming part of a treatment in humans, one of the limitations to overcome is not being able to use them in chronic diseases. This is due to the ability of the body, specifically the immune system, to recognize botulinum toxin as a foreign substance, attacking and inactivating it during the process.