Frogs and crocodiles have been found to produce substances that kill or prevent the spread of HIV, according to recent studies.  Scientists are investigating whether these findings could turn into a new drug or vaccine for HIV patients.

Investigators at Vanderbilt University Medical Center discovered that compounds secreted by frog skin are potent blockers of HIV infection; they published a report in the Journal of Virology in October 2005.  The study described how protein secretions from frog skin have been found to block the HIV virus from spreading between cells in the human immune system.

Frogs have specialized skin glands that create and store the proteinlike molecules, or peptides; when injured or frightened, the frog secretes the substance onto the surface of its skin to fight off bacteria, fungi and viruses.  If researchers are able to learn how the peptides kill HIV, they may be able to develop chemical molecules that can do the same.

Crocodiles also possess special means of combating HIV.  Researchers are examining a powerful peptide in the blood of crocodiles called Crocodillin, which is effective in killing the HIV virus on contact.  Scientists Mark Merchant and Adam Britton of Darwin's Crocodylus Park in Australia's Northern Territory are testing blood samples for the powerful crocodile antibodies.  They hope to develop and antibiotic that could be used for general infections, including HIV.  Crocodillin was first discovered by U.S. scientists in 2000, after observing that despite the severe injuries that crocodiles inflicted on each other, the wounds healed quickly and rarely got infected.

"The crocodile has an immune system which attaches to bacteria and tears in apart, and it explodes.  It's like putting a gun to the head of the bacteria and pulling the trigger," Adam Britton said.

The crocodile immune system differs from the human immune system because it directly attacks bacteria upon entry into the body.  However, if made into a drug, Crocodillin may be too powerful for human immune systems and need to be systhesized for safe consuption.  "There is a lot of work to be done.  It may take years before we can get to the stage where we have something to market," Britton said.

(Center for North American Herpetology press release, October 27, 2005
www.cnn.com, August 17, 2005
Sarah Vanstone)