Menus Subscribe Search

Follow us


Quick Studies

fung.jpg

Cryptococcus. (Photo: Public Domain)

How Weak Immune Systems Escort a Deadly Fungus Into the Brain

• April 30, 2014 • 10:50 AM

Cryptococcus. (Photo: Public Domain)

A pervasive fungus, passed along by pigeon droppings, can kill HIV patients by using a Trojan Horse strategy to invade their brains.

Pigeon droppings and vulnerable immune systems can be a deadly combination.

Fortunately, scientists are starting to figure out how different strains of a yeast that hitchhiked its way around the world in pigeon intestines can ride along inside immune cells through our bodies and into our brains.

Droppings of the humble rock dove often teem with a species of Cryptococcus, better known as Crypto, a soil-dwelling genus of fungus that researchers in 2007 concluded “gained the ability to sexually reproduce in pigeon guano and then swept the globe.” We breathe the yeast into our lungs all the time. After most of us do that, our immune systems successfully attack, either killing the invaders or smothering them and rendering them harmless. The story is different, however, for those with weakened immune systems. In the bodies of HIV patients, in particular, C. neoformans can radiate from the lungs throughout the body. Once the fungal cells reach the central nervous system, they can trigger deadly meningitis.

Scientists are starting to figure out how different strains of a yeast that hitchhiked its way around the world in pigeon intestines can ride along inside immune cells through our bodies and into our brains.

This is no obscure disease. An estimated 625,000 people are killed every year by the painful malady, most of them infected with HIV. It is a leading killer of HIV sufferers.

Understanding how the fungus works its way from the lung to the brain is a priority for medical researchers. And research published this month in the Journal of Clinical Investigation has revealed that it does this by tricking our immune systemsit hitches a ride, Trojan Horse style, inside the cells that were dispatched to attack it.

The scientists studied C. neoformans strains taken from 65 HIV patients in parts of South Africa and Thailand. They measured how effectively human macrophages (also known as phagocytes), which are large defensive cells that move freely around the body, gobbled up each strain. They found a positive correlation between the density of fungal cells in the patients’ central nervous systems and the rate at which the strains were absorbed by macrophages. The patients infected with strains that were most easily engulfed by the defensive cells were most likely to die of fungal meningitis.

The scientists propose that the macrophages are ferrying the pathogen into the brains of HIV patients. “In HIV-infected patients … the ease of uptake of cryptococci by macrophages, coupled with the inability to orchestrate an effective IFN-γ-activated fungicidal macrophage response, results in unchecked proliferation and survival,” they write.

The findings reveal that still-functioning elements of HIV patients’ immune systems help the disease spread, while broken down elements cruelly hobble any kind of an effective response.

“The immunocompromised patients that come down with Crypto have defects in adaptive immunity, or T-cell function,” says University of Birmingham professor Robin May, one of the authors of the paper. “Phagocyte function is usually semi-normal in such patients, which is why Cryptococci can still exploit these cells.”

May says the findings could help doctors figure out whether patients are infected with higher-risk strains, and prescribe treatments accordingly. In the longer term, they could lead to the development of more effective therapies.

John Upton
John Upton is a science journalist with an ecology background. He has written recently for VICE, Slate, Nautilus, Modern Farmer, Grist, and Audubon magazine. He blogs at Wonk on the Wildlife. Upton's favorite eukaryotes are fungi, but he won't fault you for being human. Follow him on Twitter @johnupton.

More From John Upton

A weekly roundup of the best of Pacific Standard and PSmag.com, delivered straight to your inbox.

Recent Posts

November 26 • 4:00 PM

Turmoil at JPMorgan

Examiners are reportedly blocked from doing their job as “London Whale” trades blow up.


November 26 • 2:00 PM

Rich Kids Are More Likely to Be Working for Dad

Nepotism is alive and well, especially for the well-off.


November 26 • 12:00 PM

How Do You Make a Living, Taxidermist?

Taxidermist Katie Innamorato talks to Noah Davis about learning her craft, seeing it become trendy, and the going-rate for a “Moss Fox.”


November 26 • 10:28 AM

Attitudes About Race Affect Actions, Even When They Don’t

Tiny effects of attitudes on individuals’ actions pile up quickly.


November 26 • 10:13 AM

Honeybees Touring America


November 26 • 10:00 AM

Understanding Money

In How to Speak Money, John Lanchester explains how the monied people talk about their mountains of cash.


November 26 • 8:00 AM

The Exponential Benefits of Eating Less

Eating less food—whole food and junk food, meat and plants, organic and conventional, GMO and non-GMO—would do a lot more than just better our personal health.


November 26 • 6:00 AM

The Incorruptible Bodies of Saints

Their figures were helped along by embalming, but, somehow, everyone forgot that part.


November 26 • 4:00 AM

The Geography of Real Estate Markets Is Shifting Under Our Feet

Policies aimed at unleashing supply in order to make housing more affordable are relying on outdated models.



November 25 • 4:00 PM

Is the Federal Reserve Bank of New York Doing Enough to Monitor Wall Street?

Bank President William Dudley says supervision is stronger than ever, but Democratic senators are unconvinced: “You need to fix it, Mr. Dudley, or we need to get someone who will.”


November 25 • 3:30 PM

Cultural Activities Help Seniors Retain Health Literacy

New research finds a link between the ability to process health-related information and regular attendance at movies, plays, and concerts.


November 25 • 12:00 PM

Why Did Doctors Stop Giving Women Orgasms?

You can thank the rise of the vibrator for that, according to technology historian Rachel Maines.


November 25 • 10:08 AM

Geography, Race, and LOLs

The online lexicon spreads through racial and ethnic groups as much as it does through geography and other traditional linguistic measures.


November 25 • 10:00 AM

If It’s Yellow, Seriously, Let It Mellow

If you actually care about water and the future of the species, you’ll think twice about flushing.


November 25 • 8:00 AM

Sometimes You Should Just Say No to Surgery

The introduction of national thyroid cancer screening in South Korea led to a 15-fold increase in diagnoses and a corresponding explosion of operations—but no difference in mortality rates. This is a prime example of over-diagnosis that’s contributing to bloated health care costs.



November 25 • 6:00 AM

The Long War Between Highbrow and Lowbrow

Despise The Avengers? Loathe the snobs who despise The Avengers? You’re not the first.


November 25 • 4:00 AM

Are Women More Open to Sex Than They Admit?

New research questions the conventional wisdom that men overestimate women’s level of sexual interest in them.


November 25 • 2:00 AM

The Geography of Innovation, or, Why Almost All Japanese People Hate Root Beer

Innovation is not a product of population density, but of something else entirely.


November 24 • 4:00 PM

Federal Reserve Announces Sweeping Review of Its Big Bank Oversight

The Federal Reserve Board wants to look at whether the views of examiners are being heard by higher-ups.



November 24 • 2:00 PM

That Catcalling Video Is a Reminder of Why Research Methods Are So Important

If your methods aren’t sound then neither are your findings.


November 24 • 12:00 PM

Yes, Republicans Can Still Win the White House

If the economy in 2016 is where it was in 2012 or better, Democrats will likely retain the White House. If not, well….


November 24 • 11:36 AM

Feeling—Not Being—Wealthy Cuts Support for Economic Redistribution

A new study suggests it’s relative wealth that leads people to oppose taxing the rich and giving to the poor.


Follow us


Attitudes About Race Affect Actions, Even When They Don’t

Tiny effects of attitudes on individuals' actions pile up quickly.

Geography, Race, and LOLs

The online lexicon spreads through racial and ethnic groups as much as it does through geography and other traditional linguistic measures.

Feeling—Not Being—Wealthy Cuts Support for Economic Redistribution

A new study suggests it's relative wealth that leads people to oppose taxing the rich and giving to the poor.

Sufferers of Social Anxiety Disorder, Your Friends Like You

The first study of friends' perceptions suggest they know something's off with their pals but like them just the same.

Standing Up for My Group by Kicking Yours

Members of a minority ethnic group are less likely to express support for gay equality if they believe their own group suffers from discrimination.

The Big One

One in two United States senators and two in five House members who left office between 1998 and 2004 became lobbyists. November/December 2014

Copyright © 2014 by Pacific Standard and The Miller-McCune Center for Research, Media, and Public Policy. All Rights Reserved.