Featured Research

from universities, journals, and other organizations

Frog-killing fungus paralyzes amphibian immune response

Date:
October 17, 2013
Source:
Vanderbilt University Medical Center
Summary:
A fungus that is killing frogs and other amphibians around the world releases a toxic factor that disables the amphibian immune response, investigators report.

Poison dart frogs like this one, photographed by Louise Rollins-Smith during a trip to Panama in 2010, are threatened by fungal infections that paralyze their immune response.
Credit: Louise Rollins-Smith/Vanderbilt University

A fungus that is killing frogs and other amphibians around the world releases a toxic factor that disables the amphibian immune response, Vanderbilt University investigators report Oct. 18 in the journal Science.

The findings represent "a step forward in understanding a long-standing puzzle -- why the amphibian immune system seems to be so inept at clearing the fungus," said Louise Rollins-Smith, Ph.D., associate professor of Pathology, Microbiology and Immunology. Although the identity of the toxic fungal factor (or factors) remains a mystery, its ability to inhibit a wide range of cell types -- including cancerous cells -- suggests that it may offer new directions for the development of immunosuppressive or anti-cancer agents.

The populations of amphibian species have been declining worldwide for more than 40 years. In the late 1990s, researchers discovered that an ancient fungus, Batrachochytrium dendrobatidis, was causing skin infections, and the fungus is now recognized as a leading contributor to global amphibian decline.

Rollins-Smith, an immunologist, and her colleagues have been studying the immune response to the fungus for more than 10 years.

"Amphibians have excellent and complex immune systems -- nearly as complex as humans -- and they should be able to recognize and clear the fungus," she said.

In early studies, the investigators demonstrated that some frogs produce anti-microbial peptides in the skin that offer a first layer of defense against the fungus. But when the fungus gets into the layers of the skin, Rollins-Smith said, the conventional lymphocyte (immune cell)-mediated immune response should be activated to clear it.

They found in the current studies that recognition of the fungus by macrophage and neutrophil cells was not impaired.

"We think it's not a block at the initial recognition stage," Rollins-Smith said. "The macrophages and neutrophils can see it as a pathogen, they can eat it up, they can do their thing."

But during the next stage of the immune response, when lymphocytes should be activated, the fungus exerts its toxic effects. The investigators demonstrated that B. dendrobatidis cells and supernatants (the incubation liquid separated from the cells) impaired lymphocyte proliferation and induced cell death of lymphocytes from frogs, mice and humans. The toxic fungal factor also inhibited the growth of cancerous mammalian cell lines.

The toxic factor was resistant to heat and proteases (enzymes that cut proteins into pieces), suggesting that it is not a protein. It appears to be a component of the cell wall, because drugs that interfere with cell wall synthesis reduce its inhibitory activity and because the zoospore -- an immature form of the fungus that lacks a cell wall -- does not produce the factor.

The new findings suggest the possibility that toxic factors -- in addition to acting locally to inhibit the immune response -- might also get into the circulation and have neurotoxic effects, Rollins-Smith said.

"Fungal infection causes rapid behavioral changes -- frogs become lethargic and start to crawl out of the water -- suggesting that even though the fungus stays in the skin, the toxic material is having effects elsewhere."

The studies, led by graduate students J. Scott Fites and Jeremy Ramsey, could also suggest new conservation measures for species that may be medically important.

"Amphibian skin has long been favored in folklore for its medicinal properties," Rollins-Smith said. "Frogs are a rich source of potentially useful molecules that might work against human pathogens."

The research was supported by grants from the National Science Foundation. Other authors of the Science paper include Whitney Holden, Sarah Collier, Danica Sutherland, Laura Reinert, Sophia Gayek, Terence Dermody, M.D., Thomas Aune, Ph.D., and Kyra Oswald-Richter, Ph.D.


Story Source:

The above story is based on materials provided by Vanderbilt University Medical Center. Note: Materials may be edited for content and length.


Journal Reference:

  1. J. S. Fites, J. P. Ramsey, W. M. Holden, S. P. Collier, D. M. Sutherland, L. K. Reinert, A. S. Gayek, T. S. Dermody, T. M. Aune, K. Oswald-Richter, L. A. Rollins-Smith. The Invasive Chytrid Fungus of Amphibians Paralyzes Lymphocyte Responses. Science, 2013; 342 (6156): 366 DOI: 10.1126/science.1243316

Cite This Page:

Vanderbilt University Medical Center. "Frog-killing fungus paralyzes amphibian immune response." ScienceDaily. ScienceDaily, 17 October 2013. <www.sciencedaily.com/releases/2013/10/131017144404.htm>.
Vanderbilt University Medical Center. (2013, October 17). Frog-killing fungus paralyzes amphibian immune response. ScienceDaily. Retrieved August 30, 2014 from www.sciencedaily.com/releases/2013/10/131017144404.htm
Vanderbilt University Medical Center. "Frog-killing fungus paralyzes amphibian immune response." ScienceDaily. www.sciencedaily.com/releases/2013/10/131017144404.htm (accessed August 30, 2014).

Share This




More Plants & Animals News

Saturday, August 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

We've Got Mites Living In Our Faces And So Do You

We've Got Mites Living In Our Faces And So Do You

Newsy (Aug. 30, 2014) A new study suggests 100 percent of adult humans (those over 18 years of age) have Demodex mites living in their faces. Video provided by Newsy
Powered by NewsLook.com
Experimental Ebola Drug ZMapp Cures Lab Monkeys Of Disease

Experimental Ebola Drug ZMapp Cures Lab Monkeys Of Disease

Newsy (Aug. 29, 2014) In a new study, a promising experimental treatment for Ebola managed to cure a group of infected macaque monkeys. Video provided by Newsy
Powered by NewsLook.com
Killer Amoeba Found in Louisiana Water System

Killer Amoeba Found in Louisiana Water System

AP (Aug. 28, 2014) State health officials say testing has confirmed the presence of a killer amoeba in a water system serving three St. John the Baptist Parish towns. (Aug. 28) Video provided by AP
Powered by NewsLook.com
Raw: Australian Sheep Gets Long Overdue Haircut

Raw: Australian Sheep Gets Long Overdue Haircut

AP (Aug. 28, 2014) Hoping to break the record for world's wooliest, Shaun the sheep came up 10 pounds shy with his fleece weighing over 50 pounds after being shorn for the first time in years. (Aug. 28) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins