Potent HIV killer found in alligator blood

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Powerful infection-fighting proteins found in alligator blood could help fight HIV and antibiotic-resistant 'superbugs' in humans, suggests new American research.

Scientists who successfully extracted the active proteins from alligators' white blood cells have found that these kill a wide variety of bacteria, fungi and viruses. The findings were presented over the weekend at the annual meeting of the American Chemical Society in New Orleans.

"We're very excited about the potential of these alligator blood proteins as both antibacterial and antifungal agents," says Mark Merchant, principal investigator at McNeese State University in Louisiana, USA, and co-author of the study. "There's a very real possibility that you could be treated with an alligator blood product one day."

Alligator's have a remarkable immune system that is well documented by researchers. Despite serious injuries sustained in brutal territorial fights, the reptiles heal quickly and without infection – a trait put down to evolutionary adaptation.

"Since crocodilians fight, inflict nasty wounds, and live in an environment that is rich in potentially infectious microbes, they have had to evolve a potent defence for protection against microbial invasion," said Merchant.

Earlier studies by Merchant and colleagues had found that alligators have an 'innate immune system', that is, their bodies can fight assailants - like fungi, virus and bacteria - without ever being exposed to them. The immune response is aggressive, destroying many of the microorganisms that humans are so vulnerable to.

Merchant has been collaborating with chemists Kermit Murray and Lancia Darville from Louisiana State University to extract blood samples from captured American alligators, and study the proteins within them. In recent work, the scientists isolated the disease-fighting white blood cells (leucocytes) in the samples and extracted the active proteins – short chains of amino acids known as antibiotic peptides - for analysis.

The group is now working to isolate and identify the antibiotic peptides responsible for the microbe-fighting power seen in the alligator's effective immune response. If successful, they aim to develop the proteins' chemical structures for use as antibacterial, antiviral and antifungal drugs in human medicine.

"Studies carried out by Merchant showed the 'gator serum had antiviral activity against the human immunodeficiency virus (HIV) [the virus that causes aids]," said fellow researcher Lancia Darville. "When exposing alligator's white blood cells to HIV in a lab, most of the virus was destroyed. If we are able to isolate the active peptides we hope to develop them for potential use of treating viruses such as HIV."

Merchant has also demonstrated that peptides in the crocodilian blood can kill the Herpes simplex virus, as well as fight fungal diseases such as the Candida albicans yeast infection. It is also successful against a broad range of bacteria, most significantly MRSA (Methicillin-resistant Staphylococcus aureus), the lethal 'superbug' that is becoming increasingly resistant to existing antibiotics and is a scourge in hospitals around the world.

However, it may not be easy to mimic any antimicrobial peptide for clinical use, added Darville. "Certain challenges, such as possible toxicity of the peptides as well as their potent antimicrobial activity under human physiological conditions, makes this process challenging."

Despite this, antibiotics containing alligator blood-derived proteins could be on our shelves in around 10 years, Merchant suggested. The proteins show particular promise as topical ointments - such as might be used in the foot ulcers of diabetic patients or on the skin of burn patients - to avert infection until damaged skin can heal.

Merchant is now conducting collaborative work with crocodile researcher Adam Britton of Big Gecko, a wildlife consultancy in Darwin, Australia, to find out if similar antimicrobial substances exist in other related reptiles, such as the crocodile and broad-snouted caiman.

"There are very clear human medical benefits that can come out of this research," Britton said. "It underscores the value of speculative research into the biology and physiology of animals that have spent millions of years getting things right - in this case, their immune system."