Why Don’t Sharks Get Viruses?

They should, in theory. Sharks have very primitive but, as it happens, highly effective immune systems.

There are no known shark viruses!

Now attention has focused on a possible reason: squalamine, a compound unique to sharks. It has proved to be a promising treatment for hepatitis and other viral diseases, researchers say.

Squalamine has not yet been tested as an antiviral agent in humans, but it has been given to hundreds of people in clinical trials designed to test its usefulness for other conditions.

Georgetown University Medical Center researcher Michael Zasloff, MD, PhD, and colleagues first discovered squalamine almost two decades ago while studying sharks in hopes of finding new, naturally occurring antibiotic agents.

Now squalamine is made synthetically, without needing to kill sharks.

New research by Zasloff has confirmed that it had “unambiguous” activity against viruses that attack cells in the liver and blood, including those that cause hepatitis B, C, and D, yellow fever and dengue fever.

The study appears online in the journal PNAS Early Edition.

How Does It Work?

Actually, it’s very interesting: squalamine does something no other compound can: it changes the electrical balance within cells, eliminating certain positively charged proteins that are bound to the negatively charged surface of the cells’ inner linings. That helps protect the cells that line the liver and blood vessels from infection, Zasloff says.

The result is that squalamine acts fast to stop viral replication by clearing the body of the invading virus within hours.

Because it works by making the host tissue less receptive to infection instead of directly targeting the virus, viral resistance may not be an issue.

Let’s hope this idea of the soil not the seed catches on elsewhere in medicine, eh?

Is Squalamine Safe?

Not necessarily. Reported side effects were few but electrical potential in cells is a vital part of life. Indeed, it is the definition of life: cells without electrical potential are dead. We are programmed at a basic level to maintain a gradient of electric charge over our cell membranes.

So it is very surprising that there wasn’t significant toxicity with this compound.

[REFERENCE: Zasloff, M. PNAS Early Edition, published online Sept. 19, 2011]