NEW YORK: MIT engineers have developed new antimicrobial peptides, which can combat bacteria causing respiratory and other infections, based on a naturally occurring peptide produced by a South American wasp. The venom of insects such as wasps and bees is full of compounds that can kill bacteria. Unfortunately, many of these compounds are also toxic to humans, making it impossible to use them as antibiotic drugs.
The scientists are now creating yet more variants of the peptide, hoping to produce one that will be just as safe and effective, but at lower doses. They also believe that their findings could be used to develop new antibiotics from other naturally-occurring antimicrobial peptides.
Not be dissuaded, an MIT team recently analyzed the venom from the South American Polybia Paulista wasp. The scientists found that one of the bacteria-killing peptides within that venom was only 12 amino acids long, suggesting that it would be relatively easy to manipulate within the lab.
Be on their findings, the researchers produced a few dozen more particularly effective variants, then tested how toxic they were to human embryonic kidney cells grown in a glass dish. Those that weren’t toxic were subsequently tested on mice infected with Pseudomonas aeruginosa bacteria, which frequently causes respiratory and urinary tract infections. While several of the variants reduced the infection, one of them (given at a high dose) eradicated it completely within four days.
To measure the peptides’ toxicity, the researchers exposed them to human embryonic kidney cells grown in a lab dish. In mice infected with Pseudomonas aeruginosa, the team found that several of the peptides could reduce the infection and could eliminate it completely.
As part of their immune defenses, many organisms, including humans, produce peptides that can kill bacteria. To help fight the emergence of antibiotic-resistant bacteria, many scientists have been trying to adapt these peptides as potential new drugs.
In the first phase of their study, the researchers created a few dozen variants of the original peptide and then measured how those changes affected the peptides’ helical structure and their hydrophobicity, which also helps to determine how well the peptides interact with membranes. They then tested these peptides against seven strains of bacteria and two of fungus, making it possible to correlate their structure and physicochemical properties with their antimicrobial potency.
Based on the structure-function relationships they identified, the researchers then designed another few dozen peptides for further testing. They were able to identify optimal percentages of hydrophobic amino acids and positively charged amino acids, and they also identified a cluster of amino acids where any changes would impair the overall function of the molecule.