Farmed horseshoe crabs could help fight sepsis
When hospitals are checking medical devices for sepsis-causing bacteria, they utilize a chemical derived from horseshoe crab blood. A new aquaculture system is promised to deliver a more sustainable supply of that blood, which could even be used to check human blood for the bacteria.
The blood of the Atlantic horseshoe crab (Limulus polyphemus) contains immune cells known as amebocytes, which produce a substance called Limulus Amebocyte Lysate (LAL). That chemical is in turn highly sensitive to the liposaccharide toxins that are produced by gram-negative bacteria, which are responsible for 80 percent of cases of life-threatening sepsis in humans.
As a result, LAL is widely used to test medical devices for the presence of such bacteria. Unfortunately, though, the LAL that's presently obtained from wild-caught L. polyphemus is unable to detect the tell-tale toxins in human blood samples. Additionally, although the animals are released back into the ocean after some of their blood is drawn, an estimated 30 percent of them die in the process – and the creatures are already classified as a vulnerable species.
With these drawbacks in mind, researchers from North Carolina-based Kepley BioSystems collaborated with colleagues from the nearby Joint School of Nanoscience and Nanoengineering, to develop a recirculating horseshoe crab aquaculture system.
Animals remain in the multi-tank setup long-term, receiving a special diet, and periodically having blood drawn under sterile conditions. The latter process involves "gently immobilizing" them, keeping their gills immersed in the water, and inserting an intravascular catheter through the pericardial membrane of their heart. The technique reportedly has a zero-percent mortality rate, and the L. polyphemus remain healthy and well-fed while living in the enclosure.
In fact, LAL obtained from the farmed animals is said to be of significantly better quality than that of their wild-caught counterparts, to the point that it can be used to detect sepsis in pretreated human blood samples.
"LAL has never before been used for patient diagnostics due to cross-reactivity and inhibitors in human blood," says Kepley president, Dr. Anthony Dellinger. "Using high-quality and potent LAL from aquaculture, we have now developed a method that makes blood samples compatible with the LAL assay, allowing it for the first time to be used in early, potentially life-saving detection of bacteria and fungi in blood."
The scientists now estimate that a total of 45,000 farmed horseshoe crabs would be sufficient to meet all current diagnostic needs, eliminating the necessity to harvest any from the wild. A paper on the research was recently published in the journal Frontiers in Marine Science.
A previous study, conducted at Princeton University, suggested that peptides harmlessly gathered from the skin of African clawed frogs could serve as an eco-friendly alternative to LAL.