They have been on Earth for about 83 million years, and their giant ancestor Deinosuchus is thought to have eaten dinosaurs. But while crocodiles are best known as aggressive apex predators, reptiles also have plenty of offensive power in their immune systems.
For the first time, scientists have discovered a unique component of saltwater crocodile physiology that helps the immune system identify and kill fungal infections. This allows them to thrive in microbial and pathogen-laden waters without infection, despite frequently sustaining sporting scars from territorial disputes in the wild.
Researchers at Latrope University in Melbourne, Australia, have isolated a unique pH-sensing mechanism consisting of small proteins known as defensins that detect infection and alert the immune system. The alarming role of defensins is so far unique to these reptiles and has not been identified in other plants or animals.
This finding has great potential to develop effective and targeted treatments for human fungal infections, which are steadily becoming more frequent due to increasing antibiotic resistance.
“Alligators have excellent antifungal defenses,” says lead author Scott Williams, a researcher at La Trobe University. “When we unraveled the structures of alligator defensins, they surprisingly looked like human proteins, which means they could be used as templates to treat fungal infections in humans. “
Discovered in the 1980s, defensins are an integral part of the immune system of plants and animals, helping to protect against microbial pathogens such as bacteria and fungi. However, little is known about the role of proteins in many other species.
In saltwater crocodiles, the defensin CpoBD13 has antibacterial activity that records environmental pH levels. This allows the animal’s immune system to recognize the infected area or cells and attack and kill the fungal pathogen.
“[Crocodile] “Because defensins can change their activity based on the pH environment, we can design other defensins to turn off or on depending on the presence or absence of infection,” Williams said. “Some treatments happen to act on healthy cells, but this mechanism helps reduce these off-target effects and focus on the harmful ones.”
The researchers believe their findings may lead to the development of synthetic defensins with pH-dependent activity that could be used to treat serious infections in humans.
This research Nature Communications.
Source: La Trobe University
